Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks.

Science.gov (United States)

Hwang, Seungtaik; Gopalan, Arun; Hovestadt, Maximilian; Piepenbreier, Frank; Chmelik, Christian; Hartmann, Martin; Snurr, Randall Q; Kärger, Jörg

2018-03-15

Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n- alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n- butane was observed, followed by an increase for n- pentane, and another decrease for n- hexane. This observation was confirmed by uptake measurements with n- butane/ n -pentane mixtures, which yield faster uptake of n- pentane. Further evidence is provided by the observation of overshooting effects, i.e., by transient n- pentane concentrations exceeding the (eventually attained) equilibrium value. Accompanying grand canonical Monte Carlo simulations reveal, for the larger n- alkanes, significant differences between the adsorbed and gas phase molecular configurations, indicating strong confinement effects within ZIF-4, which, with increasing chain length, may be expected to give rise to configurational shifts facilitating molecular propagation at particular chain lengths.

Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks

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Seungtaik Hwang

2018-03-01

Full Text Available Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n-alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n-butane was observed, followed by an increase for n-pentane, and another decrease for n-hexane. This observation was confirmed by uptake measurements with n-butane/n-pentane mixtures, which yield faster uptake of n-pentane. Further evidence is provided by the observation of overshooting effects, i.e., by transient n-pentane concentrations exceeding the (eventually attained equilibrium value. Accompanying grand canonical Monte Carlo simulations reveal, for the larger n-alkanes, significant differences between the adsorbed and gas phase molecular configurations, indicating strong confinement effects within ZIF-4, which, with increasing chain length, may be expected to give rise to configurational shifts facilitating molecular propagation at particular chain lengths.

Adsorbed Organic Material and Its Control on Wettability

DEFF Research Database (Denmark)

Matthiesen, Jesper; Hassenkam, Tue; Bovet, Nicolas Emile

2017-01-01

salinity. Here we quantified the response of sandstone core plug material in its preserved state (i.e., after storage in kerosene) and after the same core plug material was treated with ethanol and ozone to remove adsorbed organic compounds. We used the chemical force microscopy (CFM) mode of atomic force...... surfaces in artificial seawater (ASW; 35,600 ppm) and in ASW diluted to ∼1,500 ppm (ASW-low). Both before and after the ethanol/ozone treatment, and for both the alkane and the carboxylate functionalized tips, the adhesion was lower in ASW diluted to ∼1,500 ppm than in ASW. For both alkane and carboxylate...... ethanol/ozone treatment, to be a result of the loss of the organic material that was originally adsorbed on these surfaces, which adds to the charge density and thereby to the salinity dependent EDL force. Investigating the same area on the same pore surface, before and after removal of the organic...

In situ STM imaging of the structures of pentacene molecules adsorbed on Au(111).

Science.gov (United States)

Pong, Ifan; Yau, Shuehlin; Huang, Peng-Yi; Chen, Ming-Chou; Hu, Tarng-Shiang; Yang, Yawchia; Lee, Yuh-Lang

2009-09-01

In situ scanning tunneling microscope (STM) was used to examine the spatial structures of pentacene molecules adsorbed onto a Au(111) single-crystal electrode from a benzene dosing solution containing 16-400 microM pentacene. Molecular-resolution STM imaging conducted in 0.1 M HClO(4) revealed highly ordered pentacene structures of ( radical31 x radical31)R8.9 degrees , (3 x 10), ( radical31 x 10), and ( radical7 x 2 radical7)R19.1 degrees adsorbed on the reconstructed Au(111) electrode dosed with different pentacene solutions. These pentacene structures and the reconstructed Au(111) substrate were stable between 0.2 and 0.8 V [vs reversible hydrogen electrode, RHE]. Increasing the potential to E > 0.8 V lifted the reconstructed Au(111) surface and disrupted the ordered pentacene adlattices simultaneously. Ordered pentacene structures could be restored by applying potentials negative enough to reinforce the reconstructed Au(111). At potentials negative of 0.2 V, the adsorption of protons became increasingly important to displace adsorbed pentacene admolecules. Although the reconstructed Au(111) structure was not essential to produce ordered pentacene adlayers, it seemed to help the adsorption of pentacene molecules in a long-range ordered pattern. At room temperature (25 degrees C), approximately 100 pentacene molecules seen in STM images could rotate and align themselves to a neighboring domain in 10 s, suggesting that pentacene admolecules could be mobile on Au(111) under the STM imaging conditions of -150 mV in bias voltage and 1 nA in feedback current.

Tribochemical synthesis of nano-lubricant films from adsorbed molecules at sliding solid interface: Tribo-polymers from α-pinene, pinane, and n-decane

Science.gov (United States)

He, Xin; Barthel, Anthony J.; Kim, Seong H.

2016-06-01

The mechanochemical reactions of adsorbed molecules at sliding interfaces were studied for α-pinene (C10H16), pinane (C10H18), and n-decane (C10H22) on a stainless steel substrate surface. During vapor phase lubrication, molecules adsorbed at the sliding interface could be activated by mechanical shear. Under the equilibrium adsorption condition of these molecules, the friction coefficient of sliding steel surfaces was about 0.2 and a polymeric film was tribochemically produced. The synthesis yield of α-pinene tribo-polymers was about twice as much as pinane tribo-polymers. In contrast to these strained bicyclic hydrocarbons, n-decane showed much weaker activity for tribo-polymerization at the same mechanical shear condition. These results suggested that the mechanical shear at tribological interfaces could induce the opening of the strained ring structure of α-pinene and pinane, which leads to polymerization of adsorbed molecules at the sliding track. On a stainless steel surface, such polymerization reactions of adsorbed molecules do not occur under typical surface reaction conditions. The mechanical properties and boundary lubrication efficiency of the produced tribo-polymer films are discussed.

Adsorption kinetics and dynamics of small organic molecules on a silica wafer: Butane, pentane, nonane, thiophene, and methanol adsorption on SiO2/Si(1 1 1)

International Nuclear Information System (INIS)

Funk, S.; Goering, J.; Burghaus, U.

2008-01-01

The adsorption kinetics (by thermal desorption spectroscopy) and adsorption dynamics (by molecular beam scattering) have been determined for a number of alkanes, methanol, thiophene, and water on a silica wafer-SiO 2 /Si(1 1 1). No indications for bond activation were present, i.e., all probe molecules adsorb molecularly obeying 1st order kinetics. The coverage-dependent heat of adsorption has been determined accordingly. The adsorption dynamics are precursor-mediated with Kisliuk-like shapes of the adsorption probabilities at low impact energies and adsorbate-assisted adsorption at large impact energies

Metathesis of alkanes and related reactions

KAUST Repository

Basset, Jean-Marie

2010-02-16

(Figure Presented) The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, (=SiO)2TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of aluminasupported tungsten hydride, W(H)3/Al 2O3, which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis of

Metathesis of alkanes and related reactions.

Science.gov (United States)

Basset, Jean-Marie; Copéret, Christophe; Soulivong, Daravong; Taoufik, Mostafa; Cazat, Jean Thivolle

2010-02-16

The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, ([triple bond]SiO)(2)TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of alumina-supported tungsten hydride, W(H)(3)/Al(2)O(3), which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis

Alkane Metathesis

KAUST Repository

Basset, Jean-Marie

2015-03-29

Catalytic activation of alkanes which directly transforms light alkanes into higher homologs is a major area in organometallic chemistry and petrochemical chemistry. This transformation is a chemical challenge considering the inertness of the sp3 carbon-hydrogen bond. It is generally accepted that this catalytic process involves the formation of olefins. This reaction is defined as alkane metathesis. To date, two catalytic systems of alkane metathesis exist: (i) a single catalytic system prepared by surface organometallic chemistry, acting as multifunctional-supported catalyst which transforms any alkanes into a mixture of their lower and higher homologs and (ii) the other catalytic systems employing a tandem strategy with two different metals, one metal for alkane (de)hydrogenation and another for olefin metathesis in which the activity of these catalysts is essentially driven by the performance of the (de)hydrogenation steps. In this book chapter, we would focus on the evolution of these two classes of catalysts by looking at their specific reactivity of the catalysts towards alkanes, comparing their performances and studying the mechanism.

Identification and use of an alkane transporter plug-in for application in biocatalysis and whole-cell biosensing of alkanes

DEFF Research Database (Denmark)

Grant, Chris; Deszcz, Dawid; Wei, Yu-Chia

2014-01-01

Effective application of whole-cell devices in synthetic biology and biocatalysis will always require consideration of the uptake of molecules of interest into the cell. Here we demonstrate that the AlkL protein from Pseudomonas putida GPo1 is an alkane import protein capable of industrially rele...

Alkane inducible proteins in Geobacillus thermoleovorans B23

Directory of Open Access Journals (Sweden)

Kato Tomohisa

2009-03-01

Full Text Available Abstract Background Initial step of β-oxidation is catalyzed by acyl-CoA dehydrogenase in prokaryotes and mitochondria, while acyl-CoA oxidase primarily functions in the peroxisomes of eukaryotes. Oxidase reaction accompanies emission of toxic by-product reactive oxygen molecules including superoxide anion, and superoxide dismutase and catalase activities are essential to detoxify them in the peroxisomes. Although there is an argument about whether primitive life was born and evolved under high temperature conditions, thermophilic archaea apparently share living systems with both bacteria and eukaryotes. We hypothesized that alkane degradation pathways in thermophilic microorganisms could be premature and useful to understand their evolution. Results An extremely thermophilic and alkane degrading Geobacillus thermoleovorans B23 was previously isolated from a deep subsurface oil reservoir in Japan. In the present study, we identified novel membrane proteins (P16, P21 and superoxide dismutase (P24 whose production levels were significantly increased upon alkane degradation. Unlike other bacteria acyl-CoA oxidase and catalase activities were also increased in strain B23 by addition of alkane. Conclusion We first suggested that peroxisomal β-oxidation system exists in bacteria. This eukaryotic-type alkane degradation pathway in thermophilic bacterial cells might be a vestige of primitive living cell systems that had evolved into eukaryotes.

Sensitivity of photoelectron diffraction to conformational changes of adsorbed molecules: Tetra-tert-butyl-azobenzene/Au(111

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A. Schuler

2017-01-01

Full Text Available Electron diffraction is a standard tool to investigate the atomic structure of surfaces, interfaces, and adsorbate systems. In particular, photoelectron diffraction is a promising candidate for real-time studies of structural dynamics combining the ultimate time resolution of optical pulses and the high scattering cross-sections for electrons. In view of future time-resolved experiments from molecular layers, we studied the sensitivity of photoelectron diffraction to conformational changes of only a small fraction of molecules in a monolayer adsorbed on a metallic substrate. 3,3′,5,5′-tetra-tert-butyl-azobenzene served as test case. This molecule can be switched between two isomers, trans and cis, by absorption of ultraviolet light. X-ray photoelectron diffraction patterns were recorded from tetra-tert-butyl-azobenzene/Au(111 in thermal equilibrium at room temperature and compared to patterns taken in the photostationary state obtained by exposing the surface to radiation from a high-intensity helium discharge lamp. Difference patterns were simulated by means of multiple-scattering calculations, which allowed us to determine the fraction of molecules that underwent isomerization.

Unimolecular H2 elimination during the liquid phase radiolysis and photolysis of alkane - alkane mixtures

International Nuclear Information System (INIS)

Wojnarovits, L.; Foeldiak, G.

1980-01-01

Unimolecular H 2 elimination from alkanes was investigated in cyclopentane-cyclohexane, n-hexane-cyclohexane and cyclohexane-cyclooctane mixtures during fluradiolysis and 7.6 eV photolysis. During the radiolysis of all systems, and when the fluorescence shift law allowed it, during the photolysis as well, inhibited H 2 detachment was observed from the first component and sensitized hydrogen molecule elimination from the second. It has been concluded that the same excited state (the lowest singlet, S 1 ) is responsible for the H 2 elimination during radiolysis and photolysis and this is that one that gives rise to fluorescence in the experiments of other authors. The H 2 and H elimination from alkanes generally have different excited precursors. The direct population of S 1 by γ-irradiation is of limited importance and this intermediate is mainly produced in ''charge neutralization'' processes. (author)

Structure and phase transitions of monolayers of intermediate-length n-alkanes on graphite studied by neutron diffraction and molecular dynamics simulation

Science.gov (United States)

Diama, A.; Matthies, B.; Herwig, K. W.; Hansen, F. Y.; Criswell, L.; Mo, H.; Bai, M.; Taub, H.

2009-08-01

We present evidence from neutron diffraction measurements and molecular dynamics (MD) simulations of three different monolayer phases of the intermediate-length alkanes tetracosane (n-C24H50 denoted as C24) and dotriacontane (n-C32H66 denoted as C32) adsorbed on a graphite basal-plane surface. Our measurements indicate that the two monolayer films differ principally in the transition temperatures between phases. At the lowest temperatures, both C24 and C32 form a crystalline monolayer phase with a rectangular-centered (RC) structure. The two sublattices of the RC structure each consists of parallel rows of molecules in their all-trans conformation aligned with their long axis parallel to the surface and forming so-called lamellas of width approximately equal to the all-trans length of the molecule. The RC structure is uniaxially commensurate with the graphite surface in its [110] direction such that the distance between molecular rows in a lamella is 4.26 Å=√3 ag, where ag=2.46 Å is the lattice constant of the graphite basal plane. Molecules in adjacent rows of a lamella alternate in orientation between the carbon skeletal plane being parallel and perpendicular to the graphite surface. Upon heating, the crystalline monolayers transform to a "smectic" phase in which the inter-row spacing within a lamella expands by ˜10% and the molecules are predominantly oriented with the carbon skeletal plane parallel to the graphite surface. In the smectic phase, the MD simulations show evidence of broadening of the lamella boundaries as a result of molecules diffusing parallel to their long axis. At still higher temperatures, they indicate that the introduction of gauche defects into the alkane chains drives a melting transition to a monolayer fluid phase as reported previously.

Structural Insights into Diversity and n-Alkane Biodegradation Mechanisms of Alkane Hydroxylases

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Yurui eJi

2013-03-01

Full Text Available Environmental microbes utilize four degradation pathways for the oxidation of n-alkanes. Although the enzymes degrading n-alkanes in different microbes may vary, enzymes functioning in the first step in the aerobic degradation of alkanes all belong to the alkane hydroxylases. Alkane hydroxylases are a class of enzymes that insert oxygen atoms derived from molecular oxygen into different sites of the alkane terminus (or termini depending on the type of enzymes. In this review, we summarize the different types of alkane hydroxylases, their degrading steps and compare typical enzymes from various classes with regard to their three dimensional structures, in order to provide insights into how the enzymes mediate their different roles in the degradation of n-alkanes and what determines their different substrate ranges. Through the above analyses, the degrading mechanisms of enzymes can be elucidated and molecular biological methods can be utilized to expand their catalytic roles in the petrochemical industry or in bioremediation of oil-contaminated environments.

Total internal reflection sum-frequency generation spectroscopy and dense gold nanoparticles monolayer: a route for probing adsorbed molecules

International Nuclear Information System (INIS)

Tourillon, Gerard; Dreesen, Laurent; Volcke, Cedric; Sartenaer, Yannick; Thiry, Paul A; Peremans, Andre

2007-01-01

We show that sum-frequency generation spectroscopy performed in the total internal reflection configuration (TIR-SFG) combined with a dense gold nanoparticles monolayer allows us to study, with an excellent signal to noise ratio and high signal to background ratio, the conformation of adsorbed molecules. Dodecanethiol (DDT) was used as probe molecules in order to assess the potentialities of the approach. An enhancement of more than one order of magnitude of the SFG signals arising from the adsorbed species is observed with the TIR geometry compared to the external reflection one while the SFG non-resonant contribution remains the same for both configurations. Although further work is required to fully understand the origin of the SFG process on nanoparticles, our work opens new possibilities for studying nanostructures

Thermodynamics of mixtures containing alkoxyethanols. XXVIII: Liquid-liquid equilibria for 2-phenoxyethanol + selected alkanes

Energy Technology Data Exchange (ETDEWEB)

Alonso, Victor; Garcia, Mario [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain); Gonzalez, Juan Antonio, E-mail: jagl@termo.uva.es [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain); Garcia De La Fuente, Isaias; Cobos, Jose Carlos [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain)

2011-07-10

Highlights: {yields} LLE coexistence curves were determined for mixtures of 2PhEE with alkanes. {yields} UCST values are higher for n-alkane systems than for solutions with cyclic alkanes. {yields} For the latter mixtures, UCST increases with the size of the alkyl group attached. {yields} Alkoxyethanol-alkoxyethanol interactions are enhanced by aromatic group in cellosolve. - Abstract: The coexistence curves of the liquid-liquid equilibria (LLE) for systems of 2-phenoxyethanol (2PhEE) with heptane, octane, cyclohexane, methylcyclohexane or ethylcyclohexane have been determined by the method of the critical opalescence using a laser scattering technique. All the curves show an upper critical solution temperature (UCST), have a rather horizontal top and their symmetry depends on the relative size of the mixture compounds. UCST values are higher for systems with linear alkanes than for solutions including cyclic alkanes. For these mixtures, the UCST increases with the size of the alkyl group attached to the cyclic part of the molecule. It is shown that interactions between alkoxyethanol molecules are stronger when the hydroxyether contains an aromatic group. Data are used to determine the critical exponent for the order parameter mole fraction. Values obtained are consistent with those provided by the Ising model or by the renormalization group theory.

Thermodynamics of mixtures containing alkoxyethanols. XXVIII: Liquid-liquid equilibria for 2-phenoxyethanol + selected alkanes

International Nuclear Information System (INIS)

Alonso, Victor; Garcia, Mario; Gonzalez, Juan Antonio; Garcia De La Fuente, Isaias; Cobos, Jose Carlos

2011-01-01

Highlights: → LLE coexistence curves were determined for mixtures of 2PhEE with alkanes. → UCST values are higher for n-alkane systems than for solutions with cyclic alkanes. → For the latter mixtures, UCST increases with the size of the alkyl group attached. → Alkoxyethanol-alkoxyethanol interactions are enhanced by aromatic group in cellosolve. - Abstract: The coexistence curves of the liquid-liquid equilibria (LLE) for systems of 2-phenoxyethanol (2PhEE) with heptane, octane, cyclohexane, methylcyclohexane or ethylcyclohexane have been determined by the method of the critical opalescence using a laser scattering technique. All the curves show an upper critical solution temperature (UCST), have a rather horizontal top and their symmetry depends on the relative size of the mixture compounds. UCST values are higher for systems with linear alkanes than for solutions including cyclic alkanes. For these mixtures, the UCST increases with the size of the alkyl group attached to the cyclic part of the molecule. It is shown that interactions between alkoxyethanol molecules are stronger when the hydroxyether contains an aromatic group. Data are used to determine the critical exponent for the order parameter mole fraction. Values obtained are consistent with those provided by the Ising model or by the renormalization group theory.

Structure investigation of organic molecules on Au(111) surfaces; Strukturuntersuchung organischer Molekuele auf Au(111)-Oberflaechen

Energy Technology Data Exchange (ETDEWEB)

Kazempoor, Michel

2009-02-02

The present work covers two topics namely the coadsorption of formic acid and water on Au(111) and the structure of biphenylalkanthiole SAMs on Au(111) surfaces. The coadsorption of formic acid and water on Au(111) surfaces has been investigated by means of vibrational and photoelectron spectroscopy (HREELS, XPS). Formic acid adsorbs at 90 K molecularly with vibrational modes characteristic for flat lying zig-zag chains in the mono- and multilayer regime, like in solid formic acid. The structure of the flat lying formic acid chains was determined by low energy electron diffraction (LEED) as a (2r3 x r19) unit cell. Annealing results in a complete desorption at 190 K. Sequential adsorption of formic acid and water at 90 K shows no significant chemical interaction. Upon annealing the coadsorbed layer to 140 K a hydrogenbonded cyclic complex of formic acid with one water molecule could be identified using isotopically labelled adsorbates. Upon further annealing this complex decomposes leaving molecularly adsorbed formic acid on the surface at 160 K, accompanied by a proton exchange between formic acid and water. The influence of the alkane spacer chain length on the structure of biphenylalkanethiols on Au(111) surfaces was investigated as well. A systematic study was done on BPn-SAMs deposited from the gas phase. For every chain length a structure was found by LEED. Furthermore the influence of temperature on the structure was investigated in the range from room temperature up to about 400 K. To obviate influences from different preparation methods BP3 and BP4 was deposited from gas phase and from solution. No LEED spots were observed on BP4 SAMs deposited from solution. For BP3 an influence of the preparation could be excluded. For all BPn-SAMs a good agreement between LEED and STM data's was found. Nevertheless different unit cells were determined by LEED and STM consistent structures could be suggested considering the unit cell size given by LEED and the

Mechanism of melting in submonolayer films of nitrogen molecules adsorbed on the basal planes of graphite

DEFF Research Database (Denmark)

Hansen, Flemming Yssing; Bruch, Ludwig Walter; Taub, H.

1995-01-01

The melting mechanism in submonolayer films of N-2 molecules adsorbed on the basal planes of graphite is studied using molecular-dynamics simulations. The melting is strongly correlated with the formation of vacancies in the films. As the temperature increases, the edges of the submonolayer patch...

Modeling adsorption: Investigating adsorbate and adsorbent properties

Science.gov (United States)

Webster, Charles Edwin

1999-12-01

Surface catalyzed reactions play a major role in current chemical production technology. Currently, 90% of all chemicals are produced by heterogeneously catalyzed reactions. Most of these catalyzed reactions involve adsorption, concentrating the substrate(s) (the adsorbate) on the surface of the solid (the adsorbent). Pore volumes, accessible surface areas, and the thermodynamics of adsorption are essential in the understanding of solid surface characteristics fundamental to catalyst and adsorbent screening and selection. Molecular properties such as molecular volumes and projected molecular areas are needed in order to convert moles adsorbed to surface volumes and areas. Generally, these molecular properties have been estimated from bulk properties, but many assumptions are required. As a result, different literature values are employed for these essential molecular properties. Calculated molar volumes and excluded molecular areas are determined and tabulated for a variety of molecules. Molecular dimensions of molecules are important in the understanding of molecular exclusion as well as size and shape selectivity, diffusion, and adsorbent selection. Molecular dimensions can also be used in the determination of the effective catalytic pore size of a catalyst. Adsorption isotherms, on zeolites, (crystalline mineral oxides) and amorphous solids, can be analyzed with the Multiple Equilibrium Analysis (MEA) description of adsorption. The MEA produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, ΔHi, and entropies, ΔSi) of adsorption for each process. Pore volumes and accessible surface areas are calculated from the process capacities. Adsorption isotherms can also be predicted for existing and new adsorbate-adsorbent systems with the MEA. The results show that MEA has the potential of becoming a standard characterization method for microporous solids that will lead to an increased understanding of their behavior in gas

Image Charge Effects in the Wetting Behavior of Alkanes on Water with Accounting for Water Solubility

Directory of Open Access Journals (Sweden)

Kirill A. Emelyanenko

2016-03-01

Full Text Available Different types of surface forces, acting in the films of pentane, hexane, and heptane on water are discussed. It is shown that an important contribution to the surface forces originates from the solubility of water in alkanes. The equations for the distribution of electric potential inside the film are derived within the Debye-Hückel approximation, taking into account the polarization of the film boundaries by discrete charges at water-alkane interface and by the dipoles of water molecules dissolved in the film. On the basis of above equations we estimate the image charge contribution to the surface forces, excess free energy, isotherms of water adsorption in alkane film, and the total isotherms of disjoining pressure in alkane film. The results indicate the essential influence of water/alkane interface charging on the disjoining pressure in alkane films, and the wettability of water surface by different alkanes is discussed.

Journal of Chemical Sciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

In keeping with experimental data, we find the presence of ordered adsorbed layers both at single monolayer coverage and when the adsorbed layer coexists with ... The zig-zag backbone planes of all the alkane molecules lie parallel to the graphite surface at the multilayer coverage, while a few molecules are observed to ...

Quantum chemical analysis of thermodynamics of 2D cluster formation of alkanes at the water/vapor interface in the presence of aliphatic alcohols.

Science.gov (United States)

Vysotsky, Yu B; Kartashynska, E S; Belyaeva, E A; Fainerman, V B; Vollhardt, D; Miller, R

2015-11-21

Using the quantum chemical semi-empirical PM3 method it is shown that aliphatic alcohols favor the spontaneous clusterization of vaporous alkanes at the water surface due to the change of adsorption from the barrier to non-barrier mechanism. A theoretical model of the non-barrier mechanism for monolayer formation is developed. In the framework of this model alcohols (or any other surfactants) act as 'floats', which interact with alkane molecules of the vapor phase using their hydrophobic part, whereas the hydrophilic part is immersed into the water phase. This results in a significant increase of contact effectiveness of alkanes with the interface during the adsorption and film formation. The obtained results are in good agreement with the existing experimental data. To test the model the thermodynamic and structural parameters of formation and clusterization are calculated for vaporous alkanes C(n)H(2n+2) (n(CH3) = 6-16) at the water surface in the presence of aliphatic alcohols C(n)H(2n+1)OH (n(OH) = 8-16) at 298 K. It is shown that the values of clusterization enthalpy, entropy and Gibbs' energy per one monomer of the cluster depend on the chain lengths of corresponding alcohols and alkanes, the alcohol molar fraction in the monolayers formed, and the shift of the alkane molecules with respect to the alcohol molecules Δn. Two possible competitive structures of mixed 2D film alkane-alcohol are considered: 2D films 1 with single alcohol molecules enclosed by alkane molecules (the alcohols do not form domains) and 2D films 2 that contain alcohol domains enclosed by alkane molecules. The formation of the alkane films of the first type is nearly independent of the surfactant type present at the interface, but depends on their molar fraction in the monolayer formed and the chain length of the compounds participating in the clusterization, whereas for the formation of the films of the second type the interaction between the hydrophilic parts of the surfactant is

Excited-state potential-energy surfaces of metal-adsorbed organic molecules from linear expansion Δ-self-consistent field density-functional theory (ΔSCF-DFT).

Science.gov (United States)

Maurer, Reinhard J; Reuter, Karsten

2013-07-07

Accurate and efficient simulation of excited state properties is an important and much aspired cornerstone in the study of adsorbate dynamics on metal surfaces. To this end, the recently proposed linear expansion Δ-self-consistent field method by Gavnholt et al. [Phys. Rev. B 78, 075441 (2008)] presents an efficient alternative to time consuming quasi-particle calculations. In this method, the standard Kohn-Sham equations of density-functional theory are solved with the constraint of a non-equilibrium occupation in a region of Hilbert-space resembling gas-phase orbitals of the adsorbate. In this work, we discuss the applicability of this method for the excited-state dynamics of metal-surface mounted organic adsorbates, specifically in the context of molecular switching. We present necessary advancements to allow for a consistent quality description of excited-state potential-energy surfaces (PESs), and illustrate the concept with the application to Azobenzene adsorbed on Ag(111) and Au(111) surfaces. We find that the explicit inclusion of substrate electronic states modifies the topologies of intra-molecular excited-state PESs of the molecule due to image charge and hybridization effects. While the molecule in gas phase shows a clear energetic separation of resonances that induce isomerization and backreaction, the surface-adsorbed molecule does not. The concomitant possibly simultaneous induction of both processes would lead to a significantly reduced switching efficiency of such a mechanism.

Element-specific and site-specific ion desorption from adsorbed molecules by deep core-level photoexcitation at the K-edges

CERN Document Server

Baba, Y H

2003-01-01

This article reviews our recent works on the ion desorption from adsorbed and condensed molecules at low temperature following the core-level photoexcitations using synchrotron soft x-rays. The systems investigated here are adsorbed molecules with relatively heavy molecular weight containing third-row elements such as Si, P, S, and Cl. Compared with molecules composed of second-row elements, the highly element-specific and site-specific fragment-ion desorption were observed when we tune the photon energy at the dipole-allowed 1s -> sigma sup * (3p sup *) resonance. On the basis of the resonance Auger decay spectra around the 1s ionization thresholds, the observed highly specific ion desorption is interpreted by the localization of the excited electrons (here we call as 'spectator electrons') in the antibonding sigma sup * orbital. In order to separate the direct photo-induced process from the indirect processes triggered by the secondary electrons, the photon-stimulated ion desorption was also investigated in...

Thermodynamic characteristics of the adsorption of organic molecules on modified MCM-41 adsorbents

Science.gov (United States)

Gus'kov, V. Yu.; Sukhareva, D. A.; Salikhova, G. R.; Karpov, S. I.; Kudasheva, F. Kh.; Roessner, F.; Borodina, E. V.

2017-07-01

The adsorption of a number of organic molecules on samples of MCM-41 adsorbent modified with dichloromethylphenylsilane and subsequently treated with sulfuric acid (MDCS) and N-trimethoxysilylpropyl- N, N, N-trimethylammonium chloride (MNM) is studied. Specific retention volumes equal to the Henry constant are determined by means of inverse gas chromatography at infinite dilution. The thermodynamic characteristics of adsorption, the dispersive and specific components of the Helmholtz energy of adsorption, and the increment of the methyl group to the heat of adsorption are calculated. It is shown that the grafting of aminosilane and phenylsilane groups enhances the forces of dispersion and reduces specific interactions. A greater drop in polarity is observed for MDCS than for MNM, due to the stronger polarity of amoinosilane; the enthalpy factor makes the main contribution to the adsorption of organic compounds on the investigated adsorbents. It is found that the MNM sample is capable of the irreversible adsorption of alcohols.

Spins of adsorbed molecules investigated by the detection of Kondo resonance

Science.gov (United States)

Komeda, Tadahiro

2014-12-01

Surface magnetism has been one of the platforms to explore the magnetism in low dimensions. It is also a key component for the development of quantum information processes, which utilizes the spin degree of freedom. The Kondo resonance is a phenomenon that is caused by an interaction between an isolated spin and conduction electrons. First observed in the 1930s as an anomalous increase in the low-temperature resistance of metals embedded with magnetic atoms, the Kondo physics mainly studied the effects of bulk magnetic impurities in the resistivity. In the last 15 years it has undergone a revival by a scanning tunneling microscope (STM) which enables the measurement of the Kondo resonance at surfaces using an atomic scale point contact. The detection of the Kondo resonance can be a powerful tool to explore surface magnetism. In this article, I review recent studies of the surface spin of adsorbed molecules by the detection of the Kondo resonance. Researches on metal phthalocyanine (MPc) and porphyrin molecules will be examined. In addition, the Kondo resonance for double-decker lanthanoide Pc molecules will be discussed. Some of the double-decker Pc molecules show single-molecule magnet (SMM) behavior, which attracts attention as a material for electronic devices. For both classes, the ligand plays a crucial role in determining the parameters of the Kondo resonance, such as the Kondo temperature and the change of the shape from peak to Fano-dip. In addition, the spin in delocalized molecular orbital forms the Kondo resonance, which shows significant differences from the Kondo resonance formed by the metal spins. Since molecular orbital can be tuned in a flexible manner by the design of the molecule, the Kondo resonance formed by delocalized molecular orbital might expand the knowledge of this field.

Phase properties of elastic waves in systems constituted of adsorbed diatomic molecules on the (001) surface of a simple cubic crystal

Science.gov (United States)

Deymier, P. A.; Runge, K.

2018-03-01

A Green's function-based numerical method is developed to calculate the phase of scattered elastic waves in a harmonic model of diatomic molecules adsorbed on the (001) surface of a simple cubic crystal. The phase properties of scattered waves depend on the configuration of the molecules. The configurations of adsorbed molecules on the crystal surface such as parallel chain-like arrays coupled via kinks are used to demonstrate not only linear but also non-linear dependency of the phase on the number of kinks along the chains. Non-linear behavior arises for scattered waves with frequencies in the vicinity of a diatomic molecule resonance. In the non-linear regime, the variation in phase with the number of kinks is formulated mathematically as unitary matrix operations leading to an analogy between phase-based elastic unitary operations and quantum gates. The advantage of elastic based unitary operations is that they are easily realizable physically and measurable.

Surface Chemistry Dependence of Mechanochemical Reaction of Adsorbed Molecules-An Experimental Study on Tribopolymerization of α-Pinene on Metal, Metal Oxide, and Carbon Surfaces.

Science.gov (United States)

He, Xin; Kim, Seong H

2018-02-20

Mechanochemical reactions between adsorbate molecules sheared at tribological interfaces can induce association of adsorbed molecules, forming oligomeric and polymeric products often called tribopolymers). This study revealed the role or effect of surface chemistry of the solid substrate in mechanochemical polymerization reactions. As a model reactant, α-pinene was chosen because it was known to readily form tribopolymers at the sliding interface of stainless steel under vapor-phase lubrication conditions. Eight different substrate materials were tested-palladium, nickel, copper, stainless steel, gold, silicon oxide, aluminum oxide, and diamond-like carbon (DLC). All metal substrates and DLC were initially covered with surface oxide species formed naturally in air or during the oxidative sample cleaning. It was found that the tribopolymerization yield of α-pinene is much higher on the substrates that can chemisorb α-pinene, compared to the ones on which only physisorption occurs. From the load dependence of the tribopolymerization yield, it was found that the surfaces capable of chemisorption give a smaller critical activation volume for the mechanochemical reaction, compared to the ones capable of physisorption only. On the basis of these observations and infrared spectroscopy analyses of the adsorbed molecules and the produced polymers, it was concluded that the mechanochemical reaction mechanisms might be different between chemically reactive and inert surfaces and that the chemical reactivity of the substrate surface greatly influences the tribochemical polymerization reactions of adsorbed molecules.

Trimethylamine (fishy odor) adsorption by biomaterials: effect of fatty acids, alkanes, and aromatic compounds in waxes.

Science.gov (United States)

Boraphech, Phattara; Thiravetyan, Paitip

2015-03-02

Thirteen plant leaf materials were selected to be applied as dried biomaterial adsorbents for polar gaseous trimethylamine (TMA) adsorption. Biomaterial adsorbents were efficient in adsorbing gaseous TMA up to 100% of total TMA (100 ppm) within 24 h. Sansevieria trifasciata is the most effective plant leaf material while Plerocarpus indicus was the least effective in TMA adsorption. Activated carbon (AC) was found to be lower potential adsorbent to adsorb TMA when compared to biomaterial adsorbents. As adsorption data, the Langmuir isotherm supported that the gaseous TMA adsorbed monolayer on the adsorbent surface and was followed pseudo-second order kinetic model. Wax extracted from plant leaf could also adsorb gaseous TMA up to 69% of total TMA within 24 h. Another 27-63% of TMA was adsorbed by cellulose and lignin that naturally occur in high amounts in plant leaf. Subsequently, the composition appearing in biomaterial wax showed a large quantity of short-chain fatty acids (≤C18) especially octadecanoic acid (C18), and short-chain alkanes (C12-C18) as well as total aromatic components dominated in the wax, which affected TMA adsorption. Hence, it has been demonstrated that plant biomaterial is a superior biosorbent for TMA removal.

Nuclear magnetic resonance study of the structure of simple molecules adsorbed on metal surfaces: acetylene on platinum

International Nuclear Information System (INIS)

Wang, P.K.

1984-01-01

We have used NMR to determine the structure of acetylene (HC - CH) adsorbed at room temperature on small platinum particles by studying the 13 C- 13 C, 13 C- 1 H, and 1 H- 1 H dipolar interactions among the nuclei in the adsorbed molecules. We find a model of 77% CCH 2 and 23% HCCH to be the only one consistent with all of our data. The C-C bond length of the majority species, CCH 2 , is determined as 1.44 +- 0.02 A, midway between a single and double bond, suggesting that both carbon atoms bond to the surface. 36 references, 29 figures, 1 table

Topologically guided tuning of Zr-MOF pore structures for highly selective separation of C6 alkane isomers

KAUST Repository

Wang, Hao; Dong, Xinglong; Lin, Junzhong; Teat, Simon J.; Jensen, Stephanie; Cure, Jeremy; Alexandrov, Eugeny V.; Xia, Qibin; Tan, Kui; Wang, Qining; Olson, David H.; Proserpio, Davide M.; Chabal, Yves J.; Thonhauser, Timo; Sun, Junliang; Han, Yu; Li, Jing

2018-01-01

As an alternative technology to energy intensive distillations, adsorptive separation by porous solids offers lower energy cost and higher efficiency. Herein we report a topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating. Zr6O4(OH)4(bptc)3 adsorbs a large amount of n-hexane but excluding branched isomers. The n-hexane uptake is ~70% higher than that of a benchmark adsorbent, zeolite-5A. A derivative structure, Zr6O4(OH)8(H2O)4(abtc)2, is capable of discriminating all three C6 isomers and yielding a high separation factor for 3-methylpentane over 2,3-dimethylbutane. This property is critical for producing gasoline with further improved quality. Multicomponent breakthrough experiments provide a quantitative measure of the capability of these materials for separation of C6 alkane isomers. A detailed structural analysis reveals the unique topology, connectivity and relationship of these compounds.

Topologically guided tuning of Zr-MOF pore structures for highly selective separation of C6 alkane isomers

KAUST Repository

Wang, Hao

2018-04-25

As an alternative technology to energy intensive distillations, adsorptive separation by porous solids offers lower energy cost and higher efficiency. Herein we report a topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating. Zr6O4(OH)4(bptc)3 adsorbs a large amount of n-hexane but excluding branched isomers. The n-hexane uptake is ~70% higher than that of a benchmark adsorbent, zeolite-5A. A derivative structure, Zr6O4(OH)8(H2O)4(abtc)2, is capable of discriminating all three C6 isomers and yielding a high separation factor for 3-methylpentane over 2,3-dimethylbutane. This property is critical for producing gasoline with further improved quality. Multicomponent breakthrough experiments provide a quantitative measure of the capability of these materials for separation of C6 alkane isomers. A detailed structural analysis reveals the unique topology, connectivity and relationship of these compounds.

Stability, structural and electronic properties of benzene molecule adsorbed on free standing Au layer

Energy Technology Data Exchange (ETDEWEB)

Katoch, Neha, E-mail: nehakatoch2@gmail.com; Kapoor, Pooja; Sharma, Munish; Ahluwalia, P. K. [Physics Department, Himachal Pradesh University, Shimla, Himachal Pradesh, India 171005 (India); Kumar, Ashok [Center for Physical Sciences, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, India, 151001 (India)

2016-05-23

We report stability and electronic properties of benzene molecule adsorbed on the Au atomic layer within the framework of density function theory (DFT). Horizontal configuration of benzene on the top site of Au monolayer prefers energetically over other studied configurations. On the adsorption of benzene, the ballistic conductance of Au monolayer is found to decrease from 4G{sub 0} to 2G{sub 0} suggesting its applications for the fabrications of organic sensor devices based on the Au atomic layers.

Direct comparison of the electronic coupling efficiency of sulfur and selenium alligator clips for molecules adsorbed onto gold electrodes

International Nuclear Information System (INIS)

Patrone, L.; Palacin, S.; Bourgoin, J.P.

2003-01-01

Scanning tunneling microscopy experiments have been performed to compare the electronic coupling provided by S and by Se used as alligator clips for bisthiol- and biselenol-terthiophene molecules adsorbed onto gold. The molecules were inserted in a dodecanethiol (DT) self-assembled monolayer. Their apparent height above the dodecanethiol matrix was used as a measure of the electronic coupling strength corresponding to S and Se, respectively. We show that the insertion behaviors of the two molecules are qualitatively the same, and that Se provides systematically a better coupling link than S, whatever the tunneling conditions

Interplay of adsorbate-adsorbate and adsorbate-substrate interactions in self-assembled molecular surface nanostructures

DEFF Research Database (Denmark)

Schnadt, Joachim; Xu, Wei; Vang, Ronnie Thorbjørn

2010-01-01

a large tolerance to monatomic surface steps on the Ag(110) surface. The observed behaviour is explained in terms of strong intermolecular hydrogen bonding and a strong surface-mediated directionality, assisted by a sufficient degree of molecular backbone flexibility. In contrast, the same kind of step......-edge crossing is not observed when the molecules are adsorbed on the isotropic Ag(111) or more reactive Cu(110) surfaces. On Ag(111), similar 1-D assemblies are formed to those on Ag(110), but they are oriented along the step edges. On Cu(110), the carboxylic groups of NDCA are deprotonated and form covalent...... bonds to the surface, a situation which is also achieved on Ag(110) by annealing to 200 degrees C. These results show that the formation of particular self-assembled molecular nanostructures depends significantly on a subtle balance between the adsorbate-adsorbate and adsorbate-substrate interactions...

Transcriptome response to alkane biofuels in Saccharomyces cerevisiae: identification of efflux pumps involved in alkane tolerance

Science.gov (United States)

2013-01-01

Background Hydrocarbon alkanes have been recently considered as important next-generation biofuels because microbial production of alkane biofuels was demonstrated. However, the toxicity of alkanes to microbial hosts can possibly be a bottleneck for high productivity of alkane biofuels. To tackle this toxicity issue, it is essential to understand molecular mechanisms of interactions between alkanes and microbial hosts, and to harness these mechanisms to develop microbial host strains with improved tolerance against alkanes. In this study, we aimed to improve the tolerance of Saccharomyces cerevisiae, a model eukaryotic host of industrial significance, to alkane biofuels by exploiting cellular mechanisms underlying alkane response. Results To this end, we first confirmed that nonane (C9), decane (C10), and undecane (C11) were significantly toxic and accumulated in S. cerevisiae. Transcriptome analyses suggested that C9 and C10 induced a range of cellular mechanisms such as efflux pumps, membrane modification, radical detoxification, and energy supply. Since efflux pumps could possibly aid in alkane secretion, thereby reducing the cytotoxicity, we formed the hypothesis that those induced efflux pumps could contribute to alkane export and tolerance. In support of this hypothesis, we demonstrated the roles of the efflux pumps Snq2p and Pdr5p in reducing intracellular levels of C10 and C11, as well as enhancing tolerance levels against C10 and C11. This result provided the evidence that Snq2p and Pdr5p were associated with alkane export and tolerance in S. cerevisiae. Conclusions Here, we investigated the cellular mechanisms of S. cerevisiae response to alkane biofuels at a systems level through transcriptome analyses. Based on these mechanisms, we identified efflux pumps involved in alkane export and tolerance in S. cerevisiae. We believe that the results here provide valuable insights into designing microbial engineering strategies to improve cellular tolerance for

Transfer of chirality from adsorbed chiral molecules to the substrates highlighted by circular dichroism in angle-resolved valence photoelectron spectroscopy

DEFF Research Database (Denmark)

Contini, G.; Turchini, S.; Sanna, Simone

2012-01-01

Studies of self-assembled chiral molecules on achiral metallic surfaces have mostly focused on the determination of the geometry of adsorbates and their electronic structure. The aim of this paper is to provide direct information on the chirality character of the system and on the chirality...... transfer from molecules to substrate by means of circular dichroism in the angular distribution of valence photoelectrons for the extended domain of the chiral self-assembled molecular structure, formed by alaninol adsorbed on Cu(100). We show, by the dichroic behavior of a mixed molecule–copper valence...... state, that the presence of molecular chiral domains induces asymmetry in the interaction with the substrate and locally transfers the chiral character to the underlying metal atoms participating in the adsorption process; combined information related to the asymmetry of the initial electronic state...

Effect of substrate thickness on ejection of phenylalanine molecules adsorbed on free-standing graphene bombarded by 10 keV C{sub 60}

Energy Technology Data Exchange (ETDEWEB)

Golunski, M. [Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Krakow (Poland); Verkhoturov, S.V.; Verkhoturov, D.S.; Schweikert, E.A. [Department of Chemistry, Texas A& M University, College Station, TX 77840 (United States); Postawa, Z., E-mail: zbigniew.postawa@uj.edu.pl [Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Krakow (Poland)

2017-02-15

Highlights: • Substrate thickness has a prominent effect on the molecular ejection mechanism. • Collisions with projectile atoms leads to molecular ejection at thin substrates. • Interactions with deforming graphene sheet ejects molecules from thicker substrates. • Probability of fragmentation process decreases with the graphene substrate thickness. - Abstract: Molecular dynamics computer simulations have been employed to investigate the effect of substrate thickness on the ejection mechanism of phenylalanine molecules deposited on free-standing graphene. The system is bombarded from the graphene side by 10 keV C{sub 60} projectiles at normal incidence and the ejected particles are collected both in transmission and reflection directions. It has been found that the ejection mechanism depends on the substrate thickness. At thin substrates mostly organic fragments are ejected by direct collisions between projectile atoms and adsorbed molecules. At thicker substrates interaction between deforming topmost graphene sheet and adsorbed molecules becomes more important. As this process is gentle and directionally correlated, it leads predominantly to ejection of intact molecules. The implications of the results to a novel analytical approach in Secondary Ion Mass Spectrometry based on ultrathin free-standing graphene substrates and a transmission geometry are discussed.

Homology modeling and protein engineering of alkane monooxygenase in Burkholderia thailandensis MSMB121: in silico insights.

Science.gov (United States)

Jain, Chakresh Kumar; Gupta, Money; Prasad, Yamuna; Wadhwa, Gulshan; Sharma, Sanjeev Kumar

2014-07-01

The degradation of hydrocarbons plays an important role in the eco-balancing of petroleum products, pesticides and other toxic products in the environment. The degradation of hydrocarbons by microbes such as Geobacillus thermodenitrificans, Burkhulderia, Gordonia sp. and Acinetobacter sp. has been studied intensively in the literature. The present study focused on the in silico protein engineering of alkane monooxygenase (ladA)-a protein involved in the alkane degradation pathway. We demonstrated the improvement in substrate binding energy with engineered ladA in Burkholderia thailandensis MSMB121. We identified an ortholog of ladA monooxygenase found in B. thailandensis MSMB121, and showed it to be an enzyme involved in an alkane degradation pathway studied extensively in Geobacillus thermodenitrificans. Homology modeling of the three-dimensional structure of ladA was performed with a crystal structure (protein databank ID: 3B9N) as a template in MODELLER 9v11, and further validated using PROCHECK, VERIFY-3D and WHATIF tools. Specific amino acids were substituted in the region corresponding to amino acids 305-370 of ladA protein, resulting in an enhancement of binding energy in different alkane chain molecules as compared to wild protein structures in the docking experiments. The substrate binding energy with the protein was calculated using Vina (Implemented in VEGAZZ). Molecular dynamics simulations were performed to study the dynamics of different alkane chain molecules inside the binding pockets of wild and mutated ladA. Here, we hypothesize an improvement in binding energies and accessibility of substrates towards engineered ladA enzyme, which could be further facilitated for wet laboratory-based experiments for validation of the alkane degradation pathway in this organism.

Phase Behavior and Evaporation Profile of Tween 20 - Eugenol System. Effect of Different Alkane Chain Length and Solvent System

International Nuclear Information System (INIS)

Kassim, A.; Lim, W.H.; Kuangl, D.; Rusmawati, W.W.M.; Abdullah, A.H.; Teoh, S.P.

2003-01-01

The isotropic region of Tween 20/eugenol/n-alkane in aqueous systems was determined. The solubilisation trend of isotropic solution formed in the presence of eugenol was studied as a function of different alkyl chain length of n-alkane. The solubility of solvent in surfactant solution is dependent on their molecular polarity. An increase in n-alkane chain length (lower polarity) lead to smaller isotropic region which will affect the surfactant partitioning between the interface, the oil phase and the aqueous phase of the microemulsion as the oil chain length is varied. The changes of evaporation behaviour were affected strongly by the types of phases existed in the systems. The increment of n-alkane and water content led to higher evaporation rate. But the formation of w/o microemulsion would lower the evaporation rate because water molecules were trapped in the core of aggregates. In solubilisation system, evaporation rate is dependent on the solvent content and the interaction between Tween 20 and solvent molecules in the mixed composition. (author)

Auger spectra of alkanes

International Nuclear Information System (INIS)

Rye, R.R.; Jennison, D.R.; Houston, J.E.

1980-01-01

The gas-phase Auger line shapes of the linear alkanes C 1 through C 6 and of neopentane are presented and analyzed. The general shape of the spectra are characteristic of carbon in a tetrahedral environment with the major feature in all cases occurring at approx.249 eV. The relatively large spectral changes found between methane and ethane results from the direct interaction of the terminal methyl groups in ethane, and the spectra of the higher alkanes are shown to be a composite of contributions from terminal methyl and interior methylene group carbon atoms. Theoretical analysis based on a one-electron approximation is shown to be capable of making a molecular orbital assignment by comparing calculated vertical transitions to features in the Auger spectra of ethane and propane, and, in the case of ethane, of differentiating between the 2 E/sub g/ and 2 A/sub 1g/ assignment of the ground state of (C 2 H 6 ) + . A one-electron based molecular orbital treatment, however, is shown to partially break down in propane and neopentane. Analysis of neopentane and the observed absence of any noticeable major peak energy shift with increasing molecular size (as predicted by the one-electron treatment) suggests that some Auger final states occur in which both valence holes are localized on the same subunit of the molecule

Growth of n-alkane films on a single-crystal substrate

DEFF Research Database (Denmark)

Wu, Z. U.; Ehrlich, S. N.; Matthies, B.

2001-01-01

The structure and growth mode of alkane films (n-C/sub n/H/sub 2n+2/; n=4, 6, 7) adsorbed on a Ag(111) surface have been investigated by synchrotron X-ray scattering. New models are proposed for the butane (n=4) and hexane (n=6) monolayer and butane bilayer structures. Specular reflectivity scans...... reveal that growth of all films is preempted between two and three layers by nucleation of bulk particles oriented with a single bulk crystal plane parallel to the film. In the case of butane, the bulk particles also have a fixed azimuthal relationship with the film resulting in complete epitaxy....

Squeezing molecular thin alkane lubrication films between curved solid surfaces with long-range elasticity: Layering transitions and wear

DEFF Research Database (Denmark)

Sivebæk, Ion Marius; Samoilov, V. N.; Persson, B. N. J.

2003-01-01

The properties of alkane lubricants confined between two approaching solids are investigated by a model that accounts for the curvature and the elastic properties of the solid surfaces. We consider linear alkane molecules of different chain lengths, C3H8, C4H10, C8H18, C9H20, C10H22, C12H26 and C14...

Total internal reflection second-harmonic generation: probing the alkane water interface

International Nuclear Information System (INIS)

Conboy, J.C.; Daschbach, J.L.; Richmond, G.L.

1994-01-01

Total internal reflection Second-Harmonic Generation (SHG) has been used to study a series of neat n-alkane/water interfaces. Polarization and incident angular-dependent measurements of the SH response show good agreement with theoretical predictions. Analysis of the incident and polarization angular-dependent SH response allows for determination of the nonlinear optical properties of molecules comprising the interfacial region. Based on Kleinman symmetry, the measured surface nonlinear susceptibilities suggest a high degree of interfacial order for octane and decane with less order indicated by the odd carbon n-alkanes examined, heptane and nonane. The SH response in reflection and transmission has been measured under a Total Internal Reflection (TIR) of the fundamental. The measured nonlinear susceptibilities in each case are found to be identical. (orig.)

Biodegradation of n-alkanes on oil-seawater interfaces at different temperatures and microbial communities associated with the degradation.

Science.gov (United States)

Lofthus, Synnøve; Netzer, Roman; Lewin, Anna S; Heggeset, Tonje M B; Haugen, Tone; Brakstad, Odd Gunnar

2018-04-01

Oil biodegradation studies have mainly focused on microbial processes in dispersions, not specifically on the interfaces between the oil and the seawater in the dispersions. In this study, a hydrophobic adsorbent system, consisting of Fluortex fabrics, was used to investigate biodegradation of n-alkanes and microbial communities on oil-seawater interfaces in natural non-amended seawater. The study was performed over a temperature range from 0 to 20 °C, to determine how temperature affected biodegradation at the oil-seawater interfaces. Biodegradation of n-alkanes were influenced both by seawater temperature and chain-length. Biotransformation rates of n-alkanes decreased by reduced seawater temperature. Low rate coefficients at a seawater temperature of 0 °C were probably associated with changes in physical-chemical properties of alkanes. The primary bacterial colonization of the interfaces was predominated by the family Oceanospirillaceae at all temperatures, demonstrating the wide temperature range of these hydrocarbonoclastic bacteria. The mesophilic genus Oleibacter was predominant at the seawater temperature of 20 °C, and the psychrophilic genus Oleispira at 5 and 0 °C. Upon completion of n-alkane biotransformation, other oil-degrading and heterotrophic bacteria became abundant, including Piscirickettsiaceae (Cycloclasticus), Colwelliaceae (Colwellia), Altermonadaceae (Altermonas), and Rhodobacteraceae. This is one of a few studies that describe the biodegradation of oil, and the microbial communities associated with the degradation, directly at the oil-seawater interfaces over a large temperature interval.

Improved Alkane Production in Nitrogen-Fixing and Halotolerant Cyanobacteria via Abiotic Stresses and Genetic Manipulation of Alkane Synthetic Genes.

Science.gov (United States)

Kageyama, Hakuto; Waditee-Sirisattha, Rungaroon; Sirisattha, Sophon; Tanaka, Yoshito; Mahakhant, Aparat; Takabe, Teruhiro

2015-07-01

Cyanobacteria possess the unique capacity to produce alkane. In this study, effects of nitrogen deficiency and salt stress on biosynthesis of alkanes were investigated in three kinds of cyanobacteria. Intracellular alkane accumulation was increased in nitrogen-fixing cyanobacterium Anabaena sp. PCC7120, but decreased in non-diazotrophic cyanobacterium Synechococcus elongatus PCC7942 and constant in a halotolerant cyanobacterium Aphanothece halophytica under nitrogen-deficient condition. We also found that salt stress increased alkane accumulation in Anabaena sp. PCC7120 and A. halophytica. The expression levels of two alkane synthetic genes were not upregulated significantly under nitrogen deficiency or salt stress in Anabaena sp. PCC7120. The transformant Anabaena sp. PCC7120 cells with additional alkane synthetic gene set from A. halophytica increased intracellular alkane accumulation level compared to control cells. These results provide a prospect to improve bioproduction of alkanes in nitrogen-fixing halotolerant cyanobacteria via abiotic stresses and genetic engineering.

Topologically guided tuning of Zr-MOF pore structures for highly selective separation of C6 alkane isomers

Energy Technology Data Exchange (ETDEWEB)

Wang, Hao [Rutgers Univ., Piscataway, NJ (United States). Department of Chemistry and Chemical Biology; Dong, Xinglong [King Abdullah University of Science and Technology, Thuwal (Saudi Arabia). Advanced Membranes and Porous Materials Center, Physical Sciences and Engineering Division; Lin, Junzhong [Peking University, Beijing (China). College of Chemistry and Molecular Engineering; Teat, Simon J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); Jensen, Stephanie [Wake Forest University, Winston-Salem, NC (United States). Department of Physics; Cure, Jeremy [Univ. of Texas-Dallas, Richardson, TX (United States). Department of Materials Science & Engineering; Alexandrov, Eugeny V. [Samara University (Russia). Samara Center for Theoretical Materials Science (SCTMS; Xia, Qibin [Rutgers Univ., Piscataway, NJ (United States). Department of Chemistry and Chemical Biology; South China University of Technology, Guangzhou (China). School of Chemistry and Chemical Engineering; Tan, Kui [Univ. of Texas-Dallas, Richardson, TX (United States). Department of Materials Science & Engineering; Wang, Qining [Rutgers Univ., Piscataway, NJ (United States). Department of Chemistry and Chemical Biology; Olson, David H. [Rutgers Univ., Piscataway, NJ (United States). Department of Chemistry and Chemical Biology; Proserpio, Davide M. [Samara University (Russia). Samara Center for Theoretical Materials Science (SCTMS; Università degli Studi di Milano, Milano (Italy). Dipartimento di Chimica; Chabal, Yves J. [Univ. of Texas-Dallas, Richardson, TX (United States). Department of Materials Science & Engineering; Thonhauser, Timo [Wake Forest University, Winston-Salem, NC (United States). Department of Physics; Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Department of Chemistry; Sun, Junliang [Peking University, Beijing (China). College of Chemistry and Molecular Engineering; Han, Yu [King Abdullah University of Science and Technology, Thuwal (Saudi Arabia). Advanced Membranes and Porous Materials Center, Physical Sciences and Engineering Division; Li, Jing [Rutgers Univ., Piscataway, NJ (United States). Department of Chemistry and Chemical Biology

2018-05-01

As an alternative technology to energy intensive distillations, adsorptive separation by porous solids offers lower energy cost and higher efficiency. Herein we report a topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating. Zr₆O₄(OH)₄(bptc)₃ adsorbs a large amount of n-hexane but excluding branched isomers. The n-hexane uptake is ~70% higher than that of a benchmark adsorbent, zeolite-5A. A derivative structure, Zr₆O₄(OH)₈(H₂O)₄(abtc)₂, is capable of discriminating all three C6 isomers and yielding a high separation factor for 3-methylpentane over 2,3-dimethylbutane. This property is critical for producing gasoline with further improved quality. Multicomponent breakthrough experiments provide a quantitative measure of the capability of these materials for separation of C6 alkane isomers. A detailed structural analysis reveals the unique topology, connectivity and relationship of these compounds.

Localized diffusive motion on two different time scales in solid alkane nanoparticles

International Nuclear Information System (INIS)

Wang, S.-K.; Mamontov, Eugene; Bai, M.; Hansen, F.Y.; Taub, H.; Copley, J.R.D.; Garcia Sakai, V.; Gasparovic, Goran; Jenkins, Timothy; Tyagi, M.; Herwig, Kenneth W.; Neumann, D.A.; Montfrooij, W.; Volkmann, U.G.

2010-01-01

High-energy-resolution quasielastic neutron scattering on three complementary spectrometers has been used to investigate molecular diffusive motion in solid nano- to bulk-sized particles of the alkane n-C32H66. The crystalline-to-plastic and plastic-to-fluid phase transition temperatures are observed to decrease as the particle size decreases. In all samples, localized molecular diffusive motion in the plastic phase occurs on two different time scales: a 'fast' motion corresponding to uniaxial rotation about the long molecular axis; and a 'slow' motion attributed to conformational changes of the molecule. Contrary to the conventional interpretation in bulk alkanes, the fast uniaxial rotation begins in the low-temperature crystalline phase.

Shock tube measurements of the rate constants for seven large alkanes+OH

KAUST Repository

Badra, Jihad

2015-01-01

Reaction rate constants for seven large alkanes + hydroxyl (OH) radicals were measured behind reflected shock waves using OH laser absorption. The alkanes, n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethyl-butane, 2,3-dimethyl-butane, 2-methyl-heptane, and 4-methyl-heptane, were selected to investigate the rates of site-specific H-abstraction by OH at secondary and tertiary carbons. Hydroxyl radicals were monitored using narrow-line-width ring-dye laser absorption of the R1(5) transition of the OH spectrum near 306.7 nm. The high sensitivity of the diagnostic enabled the use of low reactant concentrations and pseudo-first-order kinetics. Rate constants were measured at temperatures ranging from 880 K to 1440 K and pressures near 1.5 atm. High-temperature measurements of the rate constants for OH + n-hexane and OH + 2,2-dimethyl-butane are in agreement with earlier studies, and the rate constants of the five other alkanes with OH, we believe, are the first direct measurements at combustion temperatures. Using these measurements and the site-specific H-abstraction measurements of Sivaramakrishnan and Michael (2009) [1,2], general expressions for three secondary and two tertiary abstraction rates were determined as follows (the subscripts indicate the number of carbon atoms bonded to the next-nearest-neighbor carbon): S20=1.58×10-11exp(-1550K/T)cm3molecule-1s-1(887-1327K)S30=2.37×10-11exp(-1850K/T)cm3molecule-1s-1(887-1327K)S21=4.5×10-12exp(-793.7K/T)cm3molecule-1s-1(833-1440K)T100=2.85×10-11exp(-1138.3K/T)cm3molecule-1s-1(878-1375K)T101=7.16×10-12exp(-993K/T)cm3molecule-1s-1(883-1362K) © 2014 The Combustion Institute.

Enzymes and Genes Involved in Aerobic Alkane Degradation

Directory of Open Access Journals (Sweden)

Zongze eShao

2013-05-01

Full Text Available Alkanes are major constituents of crude oil. They are also present at low concentrations in diverse non-contaminated because many living organisms produce them as chemo-attractants or as protecting agents against water loss. Alkane degradation is a widespread phenomenon in nature. The numerous microorganisms, both prokaryotic and eukaryotic, capable of utilizing alkanes as a carbon and energy source, have been isolated and characterized. This review summarizes the current knowledge of how bacteria metabolize alkanes aerobically, with a particular emphasis on the oxidation of long-chain alkanes, including factors that are responsible for chemotaxis to alkanes , transport across cell membrane of alkanes , the regulation of alkane degradation gene and initial oxidation.

Atomic force microscopy measurements of topography and friction on dotriacontane films adsorbed on a SiO2 surface

DEFF Research Database (Denmark)

Trogisch, S.; Simpson, M.J.; Taub, H.

2005-01-01

We report comprehensive atomic force microscopy (AFM) measurements at room temperature of the nanoscale topography and lateral friction on the surface of thin solid films of an intermediate-length normal alkane, dotriacontane (n-C32H66), adsorbed onto a SiO2 surface. Our topographic and frictional...

Production of liquid alkanes by controlling reactivity of sorbitol hydrogenation with a Ni/HZSM-5 catalyst in water

International Nuclear Information System (INIS)

Zhang, Qing; Wang, Tiejun; Xu, Ying; Zhang, Qi; Ma, Longlong

2014-01-01

Graphical abstract: MCM-41-modified Ni/HZSM-5 catalyst was developed by impregnation method with high catalytic performance for sorbitol hydrogenation in water. Appropriate amount of MCM-41 addition can distinctly promote the improvement in the surface structure and modulation of acidic sites of the catalyst. The scission of C–O bond in the sorbitol molecule into liquid alkanes was easily carried out on the catalyst containing more Lewis acidic sites. - Highlights: • Ni/HZSM-5 promoted with MCM-41 is active for sorbitol hydrogenation to liquid alkanes. • Lewis acidic sites of Ni/HZSM-5 can be modulated by pure silica MCM-41. • MCM-41 added can distinctly decrease carbon deposition on the catalyst surface. - Abstract: Liquid fuels derived from renewable biomass are of great importance on the potential substitution for diminishing fossil fuels. The conversion of sorbitol (a product of biomass-derived glucose hydrogenation) into liquid alkanes such as pentane and hexane over the Ni/HZSM-5 catalysts with or without MCM-41 addition was investigated in the presence of hydrogen in water medium. The production distribution of sorbitol hydrogenation can be controlled by adjusting the acidity of the catalyst. The scission of C–C bond in the sorbitol molecule into light C 1 –C 4 alkanes was mainly carried out over Ni/HZSM-5 containing strong Brønsted acid sites, while C–O bond scission into heavier alkanes was dominated over the catalysts added by MCM-41 containing weak Lewis acid sites. The sorbitol conversion and total liquid alkanes selectivity were found to be 67.1% and 98.7% over 2%Ni/HZSM-5 modified by 40 wt% of MCM-41, whereas the corresponding value was 40% and 35.6% over 2%Ni/HZSM-5 in the absence of MCM-41. The effect of MCM-41 on the structure, acidity, and reducibility of Ni/HZSM-5 was investigated by using XRD, Py-IR, IR, and H 2 -TPR. Meanwhile, the resistance of carbon deposition over the catalyst modified by MCM-41 was studied by using TG�

Nonadiabatic effects on surfaces: Kohn anomaly, electronic damping of adsorbate vibrations, and local heating of single molecules

International Nuclear Information System (INIS)

Kroeger, J

2008-01-01

Three aspects of electron-phonon coupling at metal surfaces are reviewed. One aspect is the Kohn effect, which describes an anomalous dispersion relation of surface phonons due to quasi-one-dimensional nesting of Fermi surface contours. The combination of electron energy loss spectroscopy and angle-resolved photoelectron spectroscopy allows us to unambiguously characterize Kohn anomaly systems. A second aspect is the nonadiabatic damping of adsorbate vibrations. Characteristic spectroscopic line shapes of vibrational modes allow us to estimate the amount of energy transfer between the vibrational mode and electron-hole pairs. Case studies of a Kohn anomaly and nonadiabatic damping are provided by the hydrogen- and deuterium-covered Mo(110) surface. As a third aspect of interaction between electrons and phonons, local heating of a C 60 molecule adsorbed on Cu(100) and in contact with the tip of a scanning tunnelling microscope is covered

Variation in n-Alkane Distributions of Modern Plants: Questioning Applications of n-Alkanes in Chemotaxonomy and Paleoecology

Science.gov (United States)

Bush, R. T.; McInerney, F. A.

2010-12-01

Long chain n-alkanes (n-C21 to n-C37) are synthesized as part of the epicuticular leaf wax of terrestrial plants and are among the most recognizable and widely used plant biomarkers. n-Alkane distributions have been utilized in previous studies on modern plant chemotaxonomy, testing whether taxa can be identified based on characteristic n-alkane profiles. Dominant n-alkanes (e.g. n-C27 or n-C31) have also been ascribed to major plant groups (e.g. trees or grasses respectively) and have been used in paleoecology studies to reconstruct fluctuations in plant functional types. However, many of these studies have been based on relatively few modern plant data; with the wealth of modern n-alkane studies, a more comprehensive analysis of n-alkanes in modern plants is now possible and can inform the usefulness of n-alkane distributions as paleoecological indicators. The work presented here is a combination of measurements made using plant leaves collected from the Chicago Botanic Garden and a compilation of published literature data from six continents. We categorized plants by type: angiosperms, gymnosperms, woody plants, forbs, grasses, ferns and pteridophytes, and mosses. We then quantified n-alkane distribution parameters such as carbon preference index (CPI), average chain length (ACL), and dispersion (a measure of the spread of the profile over multiple chain lengths) and used these to compare plant groups. Among all plants, one of the emergent correlations is a decrease in dispersion with increasing CPI. Within and among plant groups, n-alkane distributions show a very large range of variation, and the results show little or no correspondence between broad plant groups and a single dominant n-alkane or a ratio of n-alkanes. These findings are true both when data from six continents are combined and when plants from a given region are compared (North America). We also compared the n-alkane distributions of woody angiosperms, woody gymnosperms, and grasses with one

Short-chain alkanes synergise responses of moth pests to their sex pheromones.

Science.gov (United States)

Gurba, Alexandre; Guerin, Patrick M

2016-05-01

The use of sex pheromones for mating disruption of moth pests of crops is increasing worldwide. Efforts are under way to augment the efficiency and reliability of this control method by adding molecules derived from host plants to the sex attractants in dispensers. We show how attraction of the European grapevine moth, Lobesia botrana Den. & Schiff., and the codling moth, Cydia pomonella L., males to underdosed levels of their sex pheromones is increased by adding heptane or octane over a range of release rates. Pheromone-alkane mixtures enhance male recruitment by up to 30%, reaching levels induced by calling females, and shorten the flight time to the sex attractant by a factor of 2. The findings show the promise of using short-chain alkanes as pheromone synergists for mating disruption of insect pests of food crops. Alkane-pheromone combinations are expected to increase the competitiveness of dispensers with females, and to reduce the amount of pheromone needed for the control of these pests. © 2015 Society of Chemical Industry.

Electron stimulated desorption of cations from C sub 6 H sub 6 and C sub 6 H sub 1 sub 2 molecules adsorbed on Pt(1 1 1) and Ar spacer layer

CERN Document Server

Kawanowa, H; Hanatani, K; Gotoh, Y; Souda, R

2003-01-01

Mechanisms of electron stimulated cation desorption have been investigated for adsorbed C sub 6 H sub 6 and C sub 6 H sub 1 sub 2 molecules on the Pt(1 1 1) surface and the Ar spacer layer formed on it. The ion yields from the molecules adsorbed on the Ar spacer layer are highly enhanced at the smallest coverage and decay steeply with increasing coverage. No such enhancement was observed when they are adsorbed directly on the Pt(1 1 1) substrate. This behavior is explained in terms of the Coulombic repulsion of cations confined in nanoclusters, together with the delocalization of valence holes on the Pt(1 1 1) substrate as well as in the multilayer hydrocarbons. The holes in the C sub 6 H sub 6 molecule are more delocalized than those in the C sub 6 H sub 1 sub 2 molecule due to the overlap of pi orbitals.

Production of Low-Freezing-Point Highly Branched Alkanes through Michael Addition.

Science.gov (United States)

Jing, Yaxuan; Xia, Qineng; Liu, Xiaohui; Wang, Yanqin

2017-12-22

A new approach for the production of low-freezing-point, high-quality fuels from lignocellulose-derived molecules was developed with Michael addition as the key step. Among the investigated catalysts, CoCl 2 ⋅6 H 2 O was found most active for the Michael addition of 2,4-pentanedione with FA (single aldol adduct of furfural and acetone, 4-(2-furanyl)-3-butene-2-one). Over CoCl 2 ⋅6 H 2 O, a high carbon yield of C 13 oxygenates (about 75 %) can be achieved under mild conditions (353 K, 20 h). After hydrodeoxygenation, low-freezing-point (hydrodeoxygenation, high density (0.8415 g mL -1 ) and low-freezing-point (<223 K) branched alkanes with 18, 23 carbons within lubricant range were also obtained over a Pd/NbOPO 4 catalyst. These highly branched alkanes can be directly used as transportation fuels or additives. This work opens a new strategy for the synthesis of highly branched alkanes with low freezing point from renewable biomass. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorbates in a Box: Titration of Substrate Electronic States

Science.gov (United States)

Cheng, Zhihai; Wyrick, Jonathan; Luo, Miaomiao; Sun, Dezheng; Kim, Daeho; Zhu, Yeming; Lu, Wenhao; Kim, Kwangmoo; Einstein, T. L.; Bartels, Ludwig

2010-08-01

Nanoscale confinement of adsorbed CO molecules in an anthraquinone network on Cu(111) with a pore size of ≈4nm arranges the CO molecules in a shell structure that coincides with the distribution of substrate confined electronic states. Molecules occupy the states approximately in the sequence of rising electron energy. Despite the sixfold symmetry of the pore boundary itself, the adsorbate distribution adopts the threefold symmetry of the network-substrate system, highlighting the importance of the substrate even for such quasi-free-electron systems.

How do rod-like molecules freeze and arrange in mesopores?

International Nuclear Information System (INIS)

Huber, Patrick; Wallacher, Dirk; Hofmann, Tommy; Knorr, Klaus

2003-01-01

We present an x-ray diffraction study on rod-like molecules, i.e. the normal alkanes C 19 H 40 and C 9 H 20 condensed in nanoporous Vycor glass. Temperature-dependent diffraction patterns elucidate how the structure and phase behaviour of these molecules are affected by the random substrate disorder and the geometric confinement. For the medium-length alkane C 19 H 40 a quenching of the lamellar ordering is observed, whereas this geometric ordering principle survives in the case of the short-length C 9 H 20 , although in a modified fashion

Molecular dynamics studies of the melting of butane and hexane monolayers adsorbed on the basal-plane surface of graphite

DEFF Research Database (Denmark)

Hansen, Flemming Yssing; Newton, J. C.; Taub, H.

1993-01-01

The effect of molecular steric properties on the melting of quasi-two-dimensional solids is investigated by comparing results of molecular dynamics simulations of the melting of butane and hexane monolayers adsorbed on the basal-plane surface of graphite. These molecules differ only in their length......, being members of the n-alkane series [CH3(CH2)n−2CH3] where n=4 for butane and n=6 for hexane. The simulations employ a skeletal model, which does not include the hydrogen atoms explicitly, to represent the intermolecular and molecule–substrate interactions. Nearest-neighbor intramolecular bonds...... are fixed in length, but the molecular flexibility is preserved by allowing the bend and dihedral torsion angles to vary. The simulations show a qualitatively different melting behavior for the butane and hexane monolayers consistent with neutron and x-ray scattering experiments. The melting of the low...

Preparation of theoretical scanning tunneling microscope images of adsorbed molecules: a theoretical study of benzene on the Cu(110) surface

International Nuclear Information System (INIS)

Shapter, J.G.; Rogers, B.L.; Ford, M.J.

2003-01-01

Full text: Since its development in 1982, the Scanning Tunneling Microscope (STM) has developed into a powerful tool for the study of surfaces and adsorbates. However, the utility of the technique can be further enhanced through the development of techniques for generating theoretical STM images. This is particularly true when studying molecules adsorbed on a substrate, as the results are often interpreted superficially due to an inadequate understanding of the orbital overlap probed in the experiment. A method of preparing theoretical scanning tunneling microscope (STM) images using comparatively inexpensive desktop computers and the commercially available CRYSTAL98 package is presented through a study of benzene adsorbed on the Cu(110) surface. Density Functional Theory (DFT) and Hartree-Fock (HF) methods are used to model clean Cu(110) slabs of various thicknesses and to simulate the adsorption of benzene onto these slabs. Eight possible orientations of benzene on the Cu(110) surface are proposed, and the optimum orientation according to the calculations is presented. Theoretical STM images of the Cu(110) surface and benzene adsorbed on the Cu(110) surface are compared with experimental STM images of the system from a published study. Significant differences are observed and are examined in detail

Pulse radiolysis of alkanes: a time-resolved EPR study - Part I. Alkyl radicals

International Nuclear Information System (INIS)

Shkrob, I.A.; Trifunac, A.D.

1995-01-01

Time-resolved EPR was applied to detect short-lived alkyl radicals in pulse radiolysis of liquid alkanes. Two problems were addressed: (i) the mechanism of radical formation and (ii) the mechanism of chemically-induced spin polarization in these radicals. (i) The ratio of yields of penultimate and interior radicals in n-alkanes at the instant of their generation was found to be ≅ 1.25 times greater than the statistical quantity. This higher-than-statistical production of penultimate radicals indicates that the proton transfer reaction involving excited radical cations must be a prevailing route of radical generation. The relative yields of hydrogen abstraction and fragmentation for various branched alkanes are estimated. It is concluded that the fragmentation occurs prior to the formation of radicals in an excited precursor species. (ii) The analysis of spin-echo kinetics in n-alkanes suggests that the alkyl radicals gain the emissive polarization in spur reactions. This initial polarization increases with shortening of the aliphatic chain. We suggest that the origin of this polarization is the ST mechanism operating in the pairs of alkyl radicals and hydrogen atoms generated in dissociation of excited alkane molecules. It is also found that a long-chain structure of alkyl radicals results in much higher rate of Heisenberg spin exchange relative to the recombination rate (up to 30 times). That suggests prominent steric effects in recombination or the occurrence of through-chain electron exchange. The significance of these results in the context of cross-linking in polyethylene and higher paraffins is discussed. (Author)

Matrix effect on hydrogen-atom tunneling of organic molecules in cryogenic solids

International Nuclear Information System (INIS)

Ichikawa, Tsuneki

2000-01-01

Although the tunneling of atoms through potential energy barriers separating the reactant and reaction systems is not paid much attention in organic reactions, this plays an important role in reactions including the transfer of light atoms. Atomic tunneling is especially important for chemical reactions at low temperatures, since the thermal activation of reactant systems is very slow process in comparison with the tunneling. One of the typical reactions of atomic tunneling is hydrogen-atom abstraction from alkanes in cryogenic solids exposed to high-energy radiation. Irradiation of alkane molecules causes the homolytic cleavage of C-H bonds, which results in the pairwise formation of free hydrogen atoms and organic free radicals. Since the activation energies for the abstraction of hydrogen atoms from alkane molecules by free hydrogen atoms are higher than 5 kcal/mol, the lifetime of free hydrogen atoms at 77 K is estimated from the Arrhenius equation of k=vexp(-E a /RT) to be longer than 10 hrs. However, except for solid methane, free hydrogen atoms immediately convert to alkyl radicals even at 4.2 K by hydrogen-atom tunneling from alkane molecules to the free hydrogen atoms. The rate of hydrogen atom tunneling does not necessary increase with decreasing activation energy or the peak height of the potential energy barrier preventing the tunneling. Although the activation energy is the lowest at the tertiary carbon of alkanes, hydrogen atom tunneling from branched alkanes with tertiary carbon at the antepenultimate position of the carbon skeleton is the fastest at the secondary penultimate carbon. Based on our experimental results, we have proposed that the peculiarity of the hydrogen-atom abstraction in cryogenic solids comes from the steric hindrance by matrix molecules to the deformation of alkane molecules from the initial sp 3 to the final sp 2 configurations. The steric hindrance causes the increase of the height of the potential energy barrier for the

Catalytic total hydrodeoxygenation of biomass-derived polyfunctionalized substrates to alkanes.

Science.gov (United States)

Nakagawa, Yoshinao; Liu, Sibao; Tamura, Masazumi; Tomishige, Keiichi

2015-04-13

The total hydrodeoxygenation of carbohydrate-derived molecules to alkanes, a key reaction in the production of biofuel, was reviewed from the aspect of catalysis. Noble metals (or Ni) and acid are the main components of the catalysts, and group 6 or 7 metals such as Re are sometimes added as modifiers of the noble metal. The main reaction route is acid-catalyzed dehydration plus metal-catalyzed hydrogenation, and in some systems metal-catalyzed direct CO dissociation is involved. The appropriate active metal, acid strength, and reaction conditions depend strongly on the reactivity of the substrate. Reactions that use Pt or Pd catalysts supported on Nb-based acids or relatively weak acids are suitable for furanic substrates. Carbohydrates themselves and sugar alcohols undergo CC dissociation easily. The systems that use metal-catalyzed direct CO dissociations can give a higher yield of the corresponding alkane from carbohydrates and sugar alcohols. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Friction and diffusion dynamics of adsorbates at surfaces

NARCIS (Netherlands)

Fusco, C.

2005-01-01

A theoretical study of the motion of adsorbates (e. g. atoms, molecules or clusters) on solid surfaces is presented, with a focus on surface diffusion and atomic-scale friction. These two phenomena are inextricably linked, because when an atomic or molecular adsorbate diffuses, or is pulled, it

Effect of solid phase on the selectivity of alkyl radical formation by gamma-irradiation of branched alkanes

International Nuclear Information System (INIS)

Koizumi, Hitoshi; Hashino, Masatoshi; Ichikawa, Tsuneki; Yoshida, Hiroshi

1992-01-01

ESR and electron spin echo measurements of alkyl radicals generated by γ-irradiation of glassy and crystalline branched alkanes C 10 ∼ C 13 have been carried out to elucidate the effect of molecular structure and solid phase on the selectivity of alkyl radical formation. Alkyl radicals generated and stabilized at 77 K in the glassy alkanes are secondary penultimate radicals. Tertiary radicals and secondary radicals other than the penultimate one are not generated either by hydrogen abstraction or from ionized or excited molecules. In the crystalline alkanes, however, a small amount of secondary internal radicals are generated in addition to the predominant formation of the secondary penultimate radicals. It is concluded that the detachment of C-H hydrogen preferentially takes place at the location where the motion of carbon atoms assisting the detachment of the C-H hydrogen easily occurs. (author)

A novel growth mode of alkane films on a SiO2 surface

DEFF Research Database (Denmark)

Mo, H.; Taub, H.; Volkmann, U.G.

2003-01-01

on the SiO2 surface with the long-axis of the C32 molecules oriented parallel to the interface followed by a C32 monolayer with the long-axis perpendicular to it. Finally, preferentially oriented bulk particles nucleate having two different crystal structures. This growth model differs from that found...... previously for shorter alkanes deposited from the vapor phase onto solid surfaces....

Short-chain alkane cycling in deep Gulf of Mexico cold-seep sediments

Science.gov (United States)

Sibert, R.; Joye, S. B.; Hunter, K.

2015-12-01

Mixtures of light hydrocarbon gases are common in deep Gulf of Mexico cold-seep sediments, and are typically dissolved in pore fluids, adsorbed to sediment particles, trapped in methane ice, or as free gas. The dominant component in these natural gas mixtures is usually methane (>80% C1), but ethane (C2) and propane (C3) are nearly always present in trace amounts (95% of the methane produced at depth never reaches the water column. Production of C1 and C2 in deep-sea sediments has been historically attributed only to thermocatalytic processes, though limited data suggests production of C2/C3 compounds through the activity of archaea at depth. Furthermore, carbon isotopic data on ethane and propane from deep cores of Gulf of Mexico sediments suggest alkanogenesis at >3 m depth in the sediment column and alkane oxidation in uppermost oxidant-rich sediments. Additional studies have also isolated microorganisms capable of oxidizing ethane and propane in the laboratory, but field studies of microbial-driven dynamics of C2/C3 gases in cold-seep sediments are rare. Here, we present the results of a series of incubation experiments using sediment slurries culled from surface sediments from one of the most prolific natural oil and gas seeps in the Gulf of Mexico. Rates of alkane oxidation were measured under a variety of conditions to assess the surface-driven microbial controls on C2/C3 cycling in cold-seep environments. Such microbial processes are important in terms of the possible 'oxidative overprinting' of alkane isotopic signatures produced at depth, possibly obscuring typical microbial isotopic signals.

Pulse radiolysis studies on liquid alkanes and related polymers

International Nuclear Information System (INIS)

Tagawa, S.; Hayashi, N.; Yoshida, Y.; Washio, M.; Tabata, Y.

1989-01-01

Absorption spectra of alkane radical cations, alkane excited states, and alkyl radicals and electrons in irradiated neat liquid alkanes at room temperature were assigned on subnanosecond and nanosecond time scale after an electron pulse. Two broad visible and near-infrared absorption bands of alkane excited states and radical cations, and UV absorption band of alkyl radicals was observed in neat n-alkanes. In neat cyclohezane and trans-decalin, very broad visible absorption band mainly due to alkane excited states and UV absorption band of alkyl radicals were observed. In neat neopentane and isooctane, visible absorption bands were not observed, although UV absorption bands of alkyl radicals were observed. The wavelengths of absorptive peaks of alkane radical cations and excited states become longer with increasing the number of carbon atoms of n-alkanes. The lifetimes of alkane radical cations become shorter with decreasing the number of carbon atoms of n-alkanes and are shorter than those of electrons in neat alkanes. The main processes of the alkyl radical formation finish within the time resolution of our system (about 20 ps). The alkyl radicals are produced mainly from excited radicals cations and partly from higher excited states, the lowest excited states, radical cations, and thermal hydrogen atoms, In irradiated ethylene-propylene copolymers, broad absorption bands of excited states and tail parts of absorption bands of radical cations and electrons were observed in visible and near-infrared region, although UV absorption of alkyl radicals was not confirmed lack of transparency of polymer films. (author)

Comparison of gas-solid chromatography and MM2 force field molecular binding energies for greenhouse gases on a carbonaceous surface.

Science.gov (United States)

Rybolt, Thomas R; Bivona, Kevin T; Thomas, Howard E; O'Dell, Casey M

2009-10-01

Gas-solid chromatography was used to determine B(2s) (gas-solid virial coefficient) values for eight molecular adsorbates interacting with a carbon powder (Carbopack B, Supelco). B(2s) values were determined by multiple size variant injections within the temperature range of 313-553 K. The molecular adsorbates included: carbon dioxide (CO(2)); tetrafluoromethane (CF(4)); hexafluoroethane (C(2)F(6)); 1,1-difluoroethane (C(2)H(4)F(2)); 1-chloro-1,1-difluoroethane (C(2)H(3)ClF(2)); dichlorodifluoromethane (CCl(2)F(2)); trichlorofluoromethane (CCl(3)F); and 1,1,1-trichloroethane (C(2)H(3)Cl(3)). Two of these molecules are of special interest because they are "super greenhouse gases". The global warming potential, GWP, for CF(4) is 6500 and for C(2)F(6) is 9200 relative to the reference value of 1 for CO(2). The GWP index considers both radiative blocking and molecular lifetime. For these and other industrial greenhouse gases, adsorptive trapping on a carbonaceous solid, which depends on molecule-surface binding energy, could avoid atmospheric release. The temperature variations of the gas-solid virial coefficients in conjunction with van't Hoff plots were used to find the experimental adsorption energy or binding energy values (E(*)) for each adsorbate. A molecular mechanics based, rough-surface model was used to calculate the molecule-surface binding energy (Ecal(*)) using augmented MM2 parameters. The surface model consisted of parallel graphene layers with two separated nanostructures each containing 17 benzene rings arranged in linear strips. The separation of the parallel nanostructures had been optimized in a prior study to appropriately represent molecule-surface interactions for Carbopack B. Linear regressions of E(*) versus Ecal(*) for the current data set of eight molecules and the same surface model gave E(*)=0.926 Ecal(*) and r(2)=0.956. A combined set of the current and prior Carbopack B adsorbates studied (linear alkanes, branched alkanes, cyclic alkanes

Mechanism of trans-vinylene groups formation in the radiolysis of polyethylene and n-alkanes

International Nuclear Information System (INIS)

Borzov, S.M.; Sukhov, F.F.; Slovokhotova, N.A.

1984-01-01

Infrared spectra of polyethylene and some n-alkanes were studied after their irradiation at 20 K with 1-MeV electrons and subsequent heating to 160 K. The mechanism of trans-vinylene groups formation is suggested, which takes into account the decay of excited states of molecules in primary processes and the intra-chain recombination of free radicals in post-irradiation reactions. (author)

Geochemical Tracers and Rates of Short-Chain Alkane Production in Gulf of Mexico Cold Seep Sediments

Science.gov (United States)

Sibert, R.; Bernard, B. B.; Brooks, J. M.; Hunter, K.; Joye, S. B.

2014-12-01

The organic-rich cold seep sediments in the deep Gulf of Mexico commonly contain mixtures of light hydrocarbon gases either dissolved in pore fluids, adsorbed to sediment particles, trapped in methane ice, or as free gas. The dominant component in these natural gas mixtures is typically methane (C1), but ethane (C2) and propane (C3) are nearly always present in trace or major amounts. The ratio of C1:C2:C3 varies but C2 and C3 are typically present at single digit percent levels, whereas methane usually dominates at >80%. Methane production proceeds by at least two well-studied mechanisms: either 1) by thermocatalytic cracking of fossil organic matter, or 2) as a direct product of microbial metabolism, methanogenesis. In contrast, ethane and propane production in deep-sea sediments has been historically attributed only to thermocatalytic processes. However, limited data suggests production of C2/C3 compounds through the activity of archaea. Such studies of microbial- driven dynamics of C2/C3 gases (i.e. 'alkanogenesis') in cold seep sediments are rare. Furthermore, the identities of potential substrates are poorly constrained and no attempt has been made to quantify production rates of C2/C3 gases. However, carbon isotopic data on ethane and propane from deep cores from the Gulf of Mexico suggest alkanogenesis at depth in the sediment column and alkane oxidation in uppermost oxidant-rich sediments. Here, we present the results of a series of incubation experiments using sediment slurries culled from GC600, one of the most prolific natural oil and gas seeps in the Gulf of Mexico. Rates of both alkane production and oxidation were measured under a variety of conditions to assess the net rates of alkane production and elucidate the driving microbiological mechanisms and controls on the central processes of >C1 alkane cycling in cold seep sediments. Microbial processes are important both in terms of alkane production and oxidation, raising many questions as to the

Alkane Metathesis

KAUST Repository

Basset, Jean-Marie; Callens, Emmanuel; Riache, Nassima

2015-01-01

metal for alkane (de)hydrogenation and another for olefin metathesis in which the activity of these catalysts is essentially driven by the performance of the (de)hydrogenation steps. In this book chapter, we would focus on the evolution of these two

Organic adsorbates on metal surfaces. PTCDA and NTCDA on AG(110)

Energy Technology Data Exchange (ETDEWEB)

Abbasi, Afshin

2010-02-22

Polyaromatic molecules functionalized with carboxylic groups have served as model systems for the growth of organic semiconducting films on a large variety of substrates. Most non-reactive substrates allow for a growth mode compatible with the bulk phase of the molecular crystal with two molecules in the unit cell, but some more reactive substrates including Ag(111) and Ag(110) can induce substantial changes in the first monolayer (ML). In the specific case of Ag(110), the adsorbate unit cell of both NTCDA and PTCDA resembles a brickwall structure, with a single molecule in the unit cell. From this finding, it can be concluded that the adsorbate-substrate interaction is stronger than typical inter-molecular binding energies in the respective bulk phases. In the present work, the interactions between small Ag(110) clusters and a single NTCDA or PTCDA molecule are investigated with different ab initio techniques. Four major ingredients contribute to the binding between adsorbate and substrate: Directional bonds between Ag atoms in the topmost layer and the oxygen atoms of the molecule, Pauli repulsion between filled orbitals of molecule and substrate, an attractive van-der-Waals interaction, and a negative net charge on the molecule inducing positive image charges in the substrate, resulting therefore in an attractive Coulomb interaction between these opposite charges. As both Hartree-Fock theory and density functional theory with typical gradient-corrected density functional do not contain any long range correlation energy required for dispersion interactions, we compare these approaches with the fastest numerical technique where the leading term of the van-der-Waals interaction is included, i.e. second order Moeller-Plesset theory (MP2). Both Hartree-Fock and density functional theory result in bended optimized geometries where the adsorbate is interacting mainly via the oxygen atoms, with the core of the molecule repelled from the substrate. Only at the MP2 level

Adsorbate-induced lifting of substrate relaxation is a general mechanism governing titania surface chemistry.

Science.gov (United States)

Silber, David; Kowalski, Piotr M; Traeger, Franziska; Buchholz, Maria; Bebensee, Fabian; Meyer, Bernd; Wöll, Christof

2016-09-30

Under ambient conditions, almost all metals are coated by an oxide. These coatings, the result of a chemical reaction, are not passive. Many of them bind, activate and modify adsorbed molecules, processes that are exploited, for example, in heterogeneous catalysis and photochemistry. Here we report an effect of general importance that governs the bonding, structure formation and dissociation of molecules on oxidic substrates. For a specific example, methanol adsorbed on the rutile TiO 2 (110) single crystal surface, we demonstrate by using a combination of experimental and theoretical techniques that strongly bonding adsorbates can lift surface relaxations beyond their adsorption site, which leads to a significant substrate-mediated interaction between adsorbates. The result is a complex superstructure consisting of pairs of methanol molecules and unoccupied adsorption sites. Infrared spectroscopy reveals that the paired methanol molecules remain intact and do not deprotonate on the defect-free terraces of the rutile TiO 2 (110) surface.

In situ detection of anaerobic alkane metabolites in subsurface environments

Directory of Open Access Journals (Sweden)

Lisa eGieg

2013-06-01

Full Text Available Alkanes comprise a substantial fraction of crude oil and refined fuels. As such, they are prevalent within deep subsurface fossil fuel deposits and in shallow subsurface environments such as aquifers that are contaminated with hydrocarbons. These environments are typically anaerobic, and host diverse microbial communities that can potentially use alkanes as substrates. Anaerobic alkane biodegradation has been reported to occur under nitrate-reducing, sulfate-reducing, and methanogenic conditions. Elucidating the pathways of anaerobic alkane metabolism has been of interest in order to understand how microbes can be used to remediate contaminated sites. Alkane activation primarily occurs by addition to fumarate, yielding alkylsuccinates, unique anaerobic metabolites that can be used to indicate in situ anaerobic alkane metabolism. These metabolites have been detected in hydrocarbon-contaminated shallow aquifers, offering strong evidence for intrinsic anaerobic bioremediation. Recently, studies have also revealed that alkylsuccinates are present in oil and coal seam production waters, indicating that anaerobic microbial communities can utilize alkanes in these deeper subsurface environments. In many crude oil reservoirs, the in situ anaerobic metabolism of hydrocarbons such as alkanes may be contibuting to modern-day detrimental effects such as oilfield souring, or may lead to more benefical technologies such as enhanced energy recovery from mature oilfields. In this review, we briefly describe the key metabolic pathways for anaerobic alkane (including n-alkanes, isoalkanes, and cyclic alkanes metabolism and highlight several field reports wherein alkylsuccinates have provided evidence for anaerobic in situ alkane metabolism in shallow and deep subsurface environments.

Kinetics of conformational changes of fibronectin adsorbed onto model surfaces.

Science.gov (United States)

Baujard-Lamotte, L; Noinville, S; Goubard, F; Marque, P; Pauthe, E

2008-05-01

Fibronectin (FN), a large glycoprotein found in body fluids and in the extracellular matrix, plays a key role in numerous cellular behaviours. We investigate FN adsorption onto hydrophilic bare silica and hydrophobic polystyrene (PS) surfaces using Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) in aqueous medium. Adsorption kinetics using different bulk concentrations of FN were followed for 2h and the surface density of adsorbed FN and its time-dependent conformational changes were determined. When adsorption occurs onto the hydrophilic surface, FN molecules keep their native conformation independent of the adsorption conditions, but the amount of adsorbed FN increases with time and the bulk concentration. Although the protein surface density is the same on the hydrophobic PS surface, this has a strong impact on the average conformation of the adsorbed FN layer. Indeed, interfacial hydration changes induced by adsorption onto the hydrophobic surface lead to a decrease in unhydrated beta-sheet content and cause an increase in hydrated beta-strand and hydrated random domain content of adsorbed FN. This conformational change is mainly dependent on the bulk concentration. Indeed, at low bulk concentrations, the secondary structures of adsorbed FN molecules undergo strong unfolding, allowing an extended and hydrated conformation of the protein. At high bulk concentrations, the molecular packing reduces the unfolding of the stereoregular structures of the FN molecules, preventing stronger spreading of the protein.

Heat capacity measurements of atoms and molecules adsorbed on evaporated metal films

International Nuclear Information System (INIS)

Kenny, T.W.

1989-05-01

Investigations of the properties of absorbed monolayers have received great experimental and theoretical attention recently, both because of the importance of surface processes in practical applications such as catalysis, and the importance of such systems to the understanding of the fundamentals of thermodynamics in two dimensions. We have adapted the composite bolometer technology to the construction of microcalorimeters. For these calorimeters, the adsorption substrate is an evaporated film deposited on one surface of an optically polished sapphire wafer. This approach has allowed us to make the first measurements of the heat capacity of submonolayer films of 4 He adsorbed on metallic films. In contrast to measurements of 4 He adsorbed on all other insulating substrates, we have shown that 4 He on silver films occupies a two-dimensional gas phase over a broad range of coverages and temperatures. Our apparatus has been used to study the heat capacity of Indium flakes. CO multilayers, 4 He adsorbed on sapphire and on Ag films and H 2 adsorbed on Ag films. The results are compared with appropriate theories. 68 refs., 19 figs

High resolution spectroscopy on adsorbed molecules on a Ni (110)-surface: vibrational states and electronic levels

International Nuclear Information System (INIS)

Kardinal, I.

1998-01-01

The complementary techniques of HR-XPS and HREELS have been applied to two distinct problems. The first studies adsorption and dissociation of C 2 N 2 on Ni (110) at room temperature (RT) and at 90 K and its co-adsorption with CO. At RT C 2 N 2 dissociates and forms a c(2x2)-CN structure. The resulting CN is found to be bound in the grooves of the (110) surface yielding the lowest C-N vibrational energy yet observed. C 2 N 2 was found to dissociate even at 90 K however the resulting CN overlayer after warming to RT showed remarkable differences to that of the RT adsorption. As well as the in-groove species a number of adsorption sites on the ridges with a bond order higher have been identified. Preadsorbed CO is completely driven of the Ni (110) surface by co-adsorption of CN at RT. HREELS indicates that first CO is desorbed from the on-top-sites and then from the bridge-sites of the (110)-ridges involving a considerable increase of the HREELS cross section for the CO on the bridge-sites. Also the signal intensity of the coadsorbed CN is suppressed by the CO present on the surface. The second study investigated the adsorption of bithiophene (BiT) on clean Ni (110) and the S-modified c(2x2)-S-Ni (110) and p(4x1)-S-Ni (110). The latter provided a strongly structured substrate which forced the assembly of the adsorbed BiT-molecules. The high degree of order of this adsorbate/substrate system was obvious in both the HR-XPS results and the BREELS results with strong azimuthal anisotropy. This system was used to asses the ability to use the HREELS impact selection rules to determine molecular orientation of a reasonably complex adsorbate overlayer. (author)

Electronic structure of benzene adsorbed on Ni and Cu surfaces

Energy Technology Data Exchange (ETDEWEB)

Weinelt, M.; Nilsson, A.; Wassdahl, N. [Uppsala Univ. (Sweden)] [and others

1997-04-01

Benzene has for a long time served as a prototype adsorption system of large molecules. It adsorbs with the molecular plane parallel to the surface. The bonding of benzene to a transition metal is typically viewed to involve the {pi} system. Benzene adsorbs weakly on Cu and strongly on Ni. It is interesting to study how the adsorption strength is reflected in the electronic structure of the adsorbate-substrate complex. The authors have used X-ray Emission (XE) and X-ray Absorption (XA) spectroscopies to selectively study the electronic states localized on the adsorbed benzene molecule. Using XES the occupied states can be studies and with XAS the unoccupied states. The authors have used beamline 8.0 and the Swedish endstation equipped with a grazing incidence x-ray spectrometer and a partial yield absorption detector. The resolution in the XES and XAS were 0.5 eV and 0.05 eV, respectively.

Solid-Liquid equilibrium of n-alkanes using the Chain Delta Lattice Parameter model

DEFF Research Database (Denmark)

Coutinho, João A.P.; Andersen, Simon Ivar; Stenby, Erling Halfdan

1996-01-01

The formation of a solid phase in liquid mixtures with large paraffinic molecules is a phenomenon of interest in the petroleum, pharmaceutical, and biotechnological industries among onters. Efforts to model the solid-liquid equilibrium in these systems have been mainly empirical and with different...... degrees of success.An attempt to describe the equilibrium between the high temperature form of a paraffinic solid solution, commonly known as rotator phase, and the liquid phase is performed. The Chain Delta Lattice Parameter model (CDLP) is developed allowing a successful description of the solid-liquid...... equilibrium of n-alkanes ranging from n-C_20 to n-C_40.The model is further modified to achieve a more correct temperature dependence because it severely underestimates the excess enthalpy. It is shown that the ratio of excess enthalpy and entropy for n-alkane solid solutions, as happens for other solid...

C14–22 n-Alkanes in Soil from the Freetown Layered Intrusion, Sierra Leone: Products of Pt Catalytic Breakdown of Natural Longer Chain n-Alkanes?

Directory of Open Access Journals (Sweden)

John F. W. Bowles

2018-03-01

Full Text Available Soil above a platinum-group element (PGE-bearing horizon within the Freetown Layered Intrusion, Sierra Leone, contains anomalous concentrations of n-alkanes (CnH2n+2 in the range C14 to C22 not readily attributable to an algal or lacustrine origin. Longer chain n-alkanes (C23 to C31 in the soil were derived from the breakdown of leaf litter beneath the closed canopy humid tropical forest. Spontaneous breakdown of the longer chain n-alkanes to form C14–22 n-alkanes without biogenic or abiogenic catalysts is unlikely as the n-alkanes are stable. In the Freetown soil, the catalytic properties of the PGE (Pt in particular may lower the temperature at which oxidation of the longer chain n-alkanes can occur. Reaction between these n-alkanes and Pt species, such as Pt2+(H2O2(OH2 and Pt4+(H2O2(OH4 can bend and twist the alkanes, and significantly lower the Heat of Formation. Microbial catalysis is a possibility. Since a direct organic geochemical source of the lighter n-alkanes has not yet been identified, this paper explores the theoretical potential for abiogenic Pt species catalysis as a mechanism of breakdown of the longer n-alkanes to form C14–22 alkanes. This novel mechanism could offer additional evidence for the presence of the PGE in solution, as predicted by soil geochemistry.

Negative photoion spectroscopy of the core-excited bromo-chloro-alkanes, Br(CH2)nCl, n = 1-4

International Nuclear Information System (INIS)

Scully, S W J; Mackie, R A; Browning, R; Dunn, K F; Latimer, C J

2004-01-01

Polar photodissociation of a set of bromo-chloro-alkanes in the vicinity of the Br 3d core edge has been observed for the first time. It is shown that negative photoion spectroscopy is a powerful tool for investigating the various decay mechanisms of core-excited molecules. Analysis of these results indicates that the observed polar photodissociation arises from two competing spectator Auger decay processes in which the molecule can dissociate either before or after the core hole relaxation

Self-consistent field theory of polymer-ionic molecule complexation

OpenAIRE

Nakamura, Issei; Shi, An-Chang

2010-01-01

A self-consistent field theory is developed for polymers that are capable of binding small ionic molecules (adsorbates). The polymer-ionic molecule association is described by Ising-like binding variables, C_(i)^(a)(kΔ)(= 0 or 1), whose average determines the number of adsorbed molecules, nBI. Polymer gelation can occur through polymer-ionic molecule complexation in our model. For polymer-polymer cross-links through the ionic molecules, three types of solutions for nBI are obtained, depending...

Critical wetting of n-alkanes on water; Mouillage critique des alcanes sur l`eau

Energy Technology Data Exchange (ETDEWEB)

Ragil, K

1996-10-18

This study concerns the wetting properties of n-alkanes on water under thermodynamic equilibrium conditions, a problem that is interesting for the petroleum industry as well as for the fundamental understanding of wetting phenomena. An experimental study using ellipsometry reveals that pentane on water undergoes a continuous or critical wetting transition at a temperature equal to 53.1 deg. C. This is the first experimental observation of such a transition, confirming theoretical predictions made on this subject over ten years. This transition is characterized by a continuous and reversible evolution of the thickness of the film of pentane with temperature from a thick (but finite film) to a macroscopic film. The critical wetting transition occurs when the Hamaker constant of the system, which gives the net interaction between the two interfaces bounding the wetting layer of pentane in terms of the van der Waals forces, changes sign. A theoretical approach based on the Cahn-Landau theory, which takes into account long range forces (van der Waals forces), enables us to explain the mechanism of the critical wetting transition and to show that a first-order wetting transition should precede it. Because of their similar dispersive properties, linear alkanes could all be able to show such a succession of transitions. An ellipsometry study performed on a brine/hexane/vapor system confirms that a discontinuous transition from a thin microscopic film to a thick but finite adsorbed film takes place. THis study demonstrates that the wetting of alkanes on water is determined by subtle interplay between short range and long range forces, which can lead to an intermediary state between partial and complete wetting. (author)

Irradiation Degradation of Adsorbents for Minor Actinides Recovery

International Nuclear Information System (INIS)

Watanabe, S.; Sano, Y.; Kofuji, H.; Takeuchi, M.; Koizumi, T.

2015-01-01

Extraction chromatography is one of the promising technologies for minor actinides (MA: Am and Cm) recovery from high-level liquid waste. The degradation behaviour of the organic species in the adsorbents under radiation exposure is important to discuss the safety and durability of the adsorbent in the extraction chromatography process. In this study, gamma-ray irradiation experiments on TODGA/SiO 2 -P adsorbent were carried out to investigate the degradation products from radiolysis of the adsorbent. The degraded organic species eluted from the adsorbent and those remaining inside the adsorbent were thoroughly identified by GC/MS, FT-IR and NMR analyses. The species suspected as hydrolysis products of TODGA were mainly detected from the analyses. Since some radicals such as.H or.OH are generated by the gamma-ray irradiation on water molecules, it was discussed that the radicals products from radiolysis of HNO 3 solution are related to the degradation reaction of the extractants. (authors)

Density functional theory study the effects of oxygen-containing functional groups on oxygen molecules and oxygen atoms adsorbed on carbonaceous materials.

Science.gov (United States)

Qi, Xuejun; Song, Wenwu; Shi, Jianwei

2017-01-01

Density functional theory was used to study the effects of different types of oxygen-containing functional groups on the adsorption of oxygen molecules and single active oxygen atoms on carbonaceous materials. During gasification or combustion reactions of carbonaceous materials, oxygen-containing functional groups such as hydroxyl(-OH), carbonyl(-CO), quinone(-O), and carboxyl(-COOH) are often present on the edge of graphite and can affect graphite's chemical properties. When oxygen-containing functional groups appear on a graphite surface, the oxygen molecules are strongly adsorbed onto the surface to form a four-member ring structure. At the same time, the O-O bond is greatly weakened and easily broken. The adsorption energy value indicates that the adsorption of oxygen molecules changes from physisorption to chemisorption for oxygen-containing functional groups on the edge of a graphite surface. In addition, our results indicate that the adsorption energy depends on the type of oxygen-containing functional group. When a single active oxygen atom is adsorbed on the bridge site of graphite, it gives rise to a stable epoxy structure. Epoxy can cause deformation of the graphite lattice due to the transition of graphite from sp2 to sp3 after the addition of an oxygen atom. For quinone group on the edge of graphite, oxygen atoms react with carbon atoms to form the precursor of CO2. Similarly, the single active oxygen atoms of carbonyl groups can interact with edge carbon atoms to form the precursor of CO2. The results show that oxygen-containing functional groups on graphite surfaces enhance the activity of graphite, which promotes adsorption on the graphite surface.

Dynamics of copper-phthalocyanine molecules on Au/Ge(001)

NARCIS (Netherlands)

Sotthewes, Kai; Heimbuch, Rene; Zandvliet, Henricus J.W.

2015-01-01

Spatially resolved current-time scanning tunneling spectroscopy combined with current-distance spectroscopy has been used to characterize the dynamic behavior of copper-phthalocyanine (CuPc) molecules adsorbed on a Au-modified Ge(001) surface. The analyzed CuPc molecules are adsorbed in a “molecular

Ecological applications of the irradiated adsorbents

International Nuclear Information System (INIS)

Tusseyev, T.

2004-01-01

Full text: In our previous works it was shown that after irradiation some adsorbents gain new interesting properties such as increasing (or decreasing) of their adsorption capacity, selectivity in relation to some gases, change of chemical bounds of gas molecules with adsorbent surface as well as other properties. We investigated a lot of adsorbents with semiconducting and dielectric properties. A high temperature superconductor was investigated also. Adsorbents were irradiated by ultraviolet (UV) and gamma - radiation, reactor (n.γ) - radiation, α-particles (E=40-50 MeV), protons ( E=30 MeV), and also He-3 ions (E-29-60 MeV). The following techniques were used: volumetric (manometrical), mass-spectrometer and IR spectroscopic methods, and also method of electronic - paramagnetic resonance (spin paramagnetic resonance) The obtained results allow to speak about creation of new adsorbents for gas purification (clearing) from harmful impurities, gas selection into components, an increasing of adsorbing surface. Thus one more advantage of the irradiated adsorbents is that they have 'memory effect', i.e. they can be used enough long time after irradiation. In laboratory conditions we built the small-sized adsorptive pump on the basis of the irradiated zeolites which are capable to work in autonomous conditions. It was found, that some of adsorbents after irradiation gain (or lose) selectivity in relation to definite gases. So, silica gel, which one in initial state does not adsorb hydrogen, after gamma irradiation it becomes active in relation to hydrogen. Some of rare earths oxides also show selectivity in relation to hydrogen and oxygen depending on a type of irradiation. Thus, it is possible to create different absorbents, depending on a solved problem, using a way or selection of adsorbents, either of radiation type and energy, as a result obtained adsorbents can be used for various ecological purposes

Surface-Enhanced Raman Spectroscopy of Dye and Thiol Molecules Adsorbed on Triangular Silver Nanostructures: A Study of Near-Field Enhancement, Localization of Hot-Spots, and Passivation of Adsorbed Carbonaceous Species

Directory of Open Access Journals (Sweden)

Manuel R. Gonçalves

2012-01-01

Full Text Available Surface-enhanced Raman spectroscopy (SERS of thiols and dye molecules adsorbed on triangular silver nanostructures was investigated. The SERS hot-spots are localized at the edges and corners of the silver triangular particles. AFM and SEM measurements permit to observe many small clusters formed at the edges of triangular particles fabricated by nanosphere lithography. Finite-element calculations show that near-field enhancements can reach values of more than 200 at visible wavelengths, in the gaps between small spherical particles and large triangular particles, although for the later no plasmon resonance was found at the wavelengths investigated. The regions near the particles showing strong near-field enhancement are well correlated with spatial localization of SERS hot-spots done by confocal microscopy. Silver nanostructures fabricated by thermal evaporation present strong and fast fluctuating SERS activity, due to amorphous carbon contamination. Thiols and dye molecules seem to be able to passivate the undesired SERS activity on fresh evaporated silver.

Structures of adsorbed CO on atomically smooth and on stepped sngle crystal surfaces

International Nuclear Information System (INIS)

Madey, T.E.; Houston, J.E.

1980-01-01

The structures of molecular CO adsorbed on atomically smooth surfaces and on surfaces containing monatomic steps have been studied using the electron stimulated desorption ion angular distribution (ESDIAD) method. For CO adsorbed on the close packed Ru(001) and W(110) surfaces, the dominant bonding mode is via the carbon atom, with the CO molecular axis perpendicular to the plane of the surface. For CO on atomicaly rough Pd(210), and for CO adsorbed at step sites on four different surfaces vicinal to W(110), the axis of the molecule is tilted or inclined away from the normal to the surface. The ESDIAD method, in which ion desorption angles are related to surface bond angles, provides a direct determination of the structures of adsorbed molecules and molecular complexes on surfaces

Thermal, Catalytic Conversion of Alkanes to Linear Aldehydes and Linear Amines.

Science.gov (United States)

Tang, Xinxin; Jia, Xiangqing; Huang, Zheng

2018-03-21

Alkanes, the main constituents of petroleum, are attractive feedstocks for producing value-added chemicals. Linear aldehydes and amines are two of the most important building blocks in the chemical industry. To date, there have been no effective methods for directly converting n-alkanes to linear aldehydes and linear amines. Here, we report a molecular dual-catalyst system for production of linear aldehydes via regioselective carbonylation of n-alkanes. The system is comprised of a pincer iridium catalyst for transfer-dehydrogenation of the alkane using t-butylethylene or ethylene as a hydrogen acceptor working sequentially with a rhodium catalyst for olefin isomerization-hydroformylation with syngas. The system exhibits high regioselectivity for linear aldehydes and gives high catalytic turnover numbers when using ethylene as the acceptor. In addition, the direct conversion of light alkanes, n-pentane and n-hexane, to siloxy-terminated alkyl aldehydes through a sequence of Ir/Fe-catalyzed alkane silylation and Ir/Rh-catalyzed alkane carbonylation, is described. Finally, the Ir/Rh dual-catalyst strategy has been successfully applied to regioselective alkane aminomethylation to form linear alkyl amines.

Deposition of radiation energy in solids as visualized by the distribution, structure and properties of alkyl radicals in γ-irradiated n-alkane single crystals

International Nuclear Information System (INIS)

Gillbro, T.; Lund, A.

1976-01-01

This paper summarizes results obtained earlier from ESR studies of γ-irradiated n-alkane single crystals. It also contains some new experimental results that serve to give a more complete picture of the deposition of radiation energy in solid alkanes. The experiments performed with solid n-alkanes have thus far provided structural data that permit the nature and even the conformation of alkyl radicals to be clearly understood. Two types of radical exist namely, one where the unpaired electron is located next to the end methyl group and one with the unpaired electron in the interior of the chain. The first type has a conformation which differs from that of the undamaged molecule. Microwave saturation data show that there is a difference in relaxation properties of these radicals which can be understood in terms of a difference in mobility. Relative yield measurements give the distribution of isomeric alkyl, the result differing from that obtained using product analysis in liquids. For protiated n-alkanes n-alkyl is lacking and the 2-alkyl concentration is higher than expected. For deuterated n-alkanes the ESR spectrum is mainly that of radicals with the unpaired electron located in the interior of the carbon chain. This isotope effect is again contrary to observations in liquid n-alkanes. The broad lines observed in protiated alkanes irradiated at 77 K and deuterated alkanes irradiated at 4.2 K are not believed to arise from strong spin-spin interactions. They are thought instead to arise from distorted crystal and radical structures relating to the damaged regions of the crystals. (Auth.)

Plant n-alkane production from litterfall altered the diversity and community structure of alkane degrading bacteria in litter layer in lowland subtropical rainforest in Taiwan

Science.gov (United States)

Huang, Tung-Yi; Hsu, Bing-Mu; Chao, Wei-Chun; Fan, Cheng-Wei

2018-03-01

n-Alkane and alkane-degrading bacteria have long been used as crucial biological indicators of paleoecology, petroleum pollution, and oil and gas prospecting. However, the relationship between n-alkane and alkane-degrading bacteria in natural forests is still poorly understood. In this study, long-chain n-alkane (C14-C35) concentrations in litterfall, litter layer, and topsoil as well as the diversity and abundance of n-alkane-degrading bacterial communities in litter layers were investigated in three habitats across a lowland subtropical rainforest in southern Taiwan: ravine, windward, and leeward habitats in Nanjenshan. Our results demonstrate that the litterfall yield and productivity of long-chain n-alkane were highest in the ravine habitats. However, long-chain n-alkane concentrations in all habitats were decreased drastically to a similar low level from the litterfall to the bulk soil, suggesting a higher rate of long-chain n-alkane degradation in the ravine habitat. Operational taxonomic unit (OTU) analysis using next-generation sequencing data revealed that the relative abundances of microbial communities in the windward and leeward habitats were similar and different from that in the ravine habitat. Data mining of community amplicon sequencing using the NCBI database revealed that alkB-gene-associated bacteria (95 % DNA sequence similarity to alkB-containing bacteria) were most abundant in the ravine habitat. Empirical testing of litter layer samples using semi-quantitative polymerase chain reaction for determining alkB gene levels confirmed that the ravine habitat had higher alkB gene levels than the windward and leeward habitats. Heat map analysis revealed parallels in pattern color between the plant and microbial species compositions of the habitats, suggesting a causal relationship between the plant n-alkane production and microbial community diversity. This finding indicates that the diversity and relative abundance of microbial communities in the

Miscibility and interaction between 1-alkanol and short-chain phosphocholine in the adsorbed film and micelles.

Science.gov (United States)

Takajo, Yuichi; Matsuki, Hitoshi; Kaneshina, Shoji; Aratono, Makoto; Yamanaka, Michio

2007-09-01

The miscibility and interaction of 1-hexanol (C6OH) and 1-heptanol (C7OH) with 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) in the adsorbed films and micelles were investigated by measuring the surface tension of aqueous C6OH-DHPC and aqueous C7OH-DHPC solutions. The surface density, the mean molecular area, the composition of the adsorbed film, and the excess Gibbs energy of adsorption g(H,E), were estimated. Further, the critical micelle concentration of the mixtures was determined from the surface tension versus molality curves; the micellar composition was calculated. The miscibility of the 1-alkanols and DHPC molecules in the adsorbed film and micelles was examined using the phase diagram of adsorption (PDA) and that of micellization (PDM). The PDA and the composition dependence of g(H,E) indicated the non-ideal mixing of the 1-alkanols and DHPC molecules due to the attractive interaction between the molecules in the adsorbed film, while the PDM indicated that the 1-alkanol molecules were not incorporated in the micelles within DHPC rich region. The dependence of the mean molecular area of the mixtures on the surface composition suggested that the packing property of the adsorbed film depends on the chain length of 1-alkanol: C6OH expands the DHPC adsorbed film more than C7OH.

Theory and simulation of epitaxial rotation. Light particles adsorbed on graphite

DEFF Research Database (Denmark)

Vives, E.; Lindgård, P.-A.

1993-01-01

We present a theory and Monte Carlo simulations of adsorbed particles on a corrugated substrate. We have focused on the case of rare gases and light molecules, H-2 and D2, adsorbed on graphite. The competition between the particle-particle and particle-substrate interactions gives rise to frustra...... found a modulated 4 x 4 structure. Energy, structure-factor intensities, peak positions, and epitaxial rotation angles as a function of temperature and coverage have been determined from the simulations. Good agreement with theory and experimental data is found.......We present a theory and Monte Carlo simulations of adsorbed particles on a corrugated substrate. We have focused on the case of rare gases and light molecules, H-2 and D2, adsorbed on graphite. The competition between the particle-particle and particle-substrate interactions gives rise...... between the commensurate and incommensurate phase for the adsorbed systems. From our simulations and our theory, we are, able to understand the gamma phase of D2 as an ordered phase stabilized by disorder. It can be described as a 2q-modulated structure. In agreement with the experiments, we have also...

Comparative assessment of computational methods for the determination of solvation free energies in alcohol-based molecules.

Science.gov (United States)

Martins, Silvia A; Sousa, Sergio F

2013-06-05

The determination of differences in solvation free energies between related drug molecules remains an important challenge in computational drug optimization, when fast and accurate calculation of differences in binding free energy are required. In this study, we have evaluated the performance of five commonly used polarized continuum model (PCM) methodologies in the determination of solvation free energies for 53 typical alcohol and alkane small molecules. In addition, the performance of these PCM methods, of a thermodynamic integration (TI) protocol and of the Poisson-Boltzmann (PB) and generalized Born (GB) methods, were tested in the determination of solvation free energies changes for 28 common alkane-alcohol transformations, by the substitution of an hydrogen atom for a hydroxyl substituent. The results show that the solvation model D (SMD) performs better among the PCM-based approaches in estimating solvation free energies for alcohol molecules, and solvation free energy changes for alkane-alcohol transformations, with an average error below 1 kcal/mol for both quantities. However, for the determination of solvation free energy changes on alkane-alcohol transformation, PB and TI yielded better results. TI was particularly accurate in the treatment of hydroxyl groups additions to aromatic rings (0.53 kcal/mol), a common transformation when optimizing drug-binding in computer-aided drug design. Copyright © 2013 Wiley Periodicals, Inc.

Fast on-line analysis of process alkane gas mixtures by NIR spectroscopy

NARCIS (Netherlands)

Boelens, H. F. M.; Kok, W. T.; de Noord, O. E.; Smilde, A. K.

2000-01-01

Proper operation of a molecular sieve process for the separation of iso- and cyclo-alkanes front normal alkanes requires the fast online detection of normal alkanes breaking through the column. The feasibility of using near-infrared (NIR) spectroscopy for this application was investigated. Alkane

Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

Energy Technology Data Exchange (ETDEWEB)

Ogletree, D.F.

1986-11-01

LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2..sqrt..3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (..sqrt..3 x ..sqrt..3) reconstruction on the (111) face of the ..cap alpha..-CuAl alloy has been determined.

Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

International Nuclear Information System (INIS)

Ogletree, D.F.

1986-11-01

LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2√3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (√3 x √3) reconstruction on the (111) face of the α-CuAl alloy has been determined

Crystallization features of normal alkanes in confined geometry.

Science.gov (United States)

Su, Yunlan; Liu, Guoming; Xie, Baoquan; Fu, Dongsheng; Wang, Dujin

2014-01-21

How polymers crystallize can greatly affect their thermal and mechanical properties, which influence the practical applications of these materials. Polymeric materials, such as block copolymers, graft polymers, and polymer blends, have complex molecular structures. Due to the multiple hierarchical structures and different size domains in polymer systems, confined hard environments for polymer crystallization exist widely in these materials. The confined geometry is closely related to both the phase metastability and lifetime of polymer. This affects the phase miscibility, microphase separation, and crystallization behaviors and determines both the performance of polymer materials and how easily these materials can be processed. Furthermore, the size effect of metastable states needs to be clarified in polymers. However, scientists find it difficult to propose a quantitative formula to describe the transition dynamics of metastable states in these complex systems. Normal alkanes [CnH2n+2, n-alkanes], especially linear saturated hydrocarbons, can provide a well-defined model system for studying the complex crystallization behaviors of polymer materials, surfactants, and lipids. Therefore, a deeper investigation of normal alkane phase behavior in confinement will help scientists to understand the crystalline phase transition and ultimate properties of many polymeric materials, especially polyolefins. In this Account, we provide an in-depth look at the research concerning the confined crystallization behavior of n-alkanes and binary mixtures in microcapsules by our laboratory and others. Since 2006, our group has developed a technique for synthesizing nearly monodispersed n-alkane containing microcapsules with controllable size and surface porous morphology. We applied an in situ polymerization method, using melamine-formaldehyde resin as shell material and nonionic surfactants as emulsifiers. The solid shell of microcapsules can provide a stable three-dimensional (3-D

Metabolism of Hydrocarbons in n-Alkane-Utilizing Anaerobic Bacteria.

Science.gov (United States)

Wilkes, Heinz; Buckel, Wolfgang; Golding, Bernard T; Rabus, Ralf

2016-01-01

The glycyl radical enzyme-catalyzed addition of n-alkanes to fumarate creates a C-C-bond between two concomitantly formed stereogenic carbon centers. The configurations of the two diastereoisomers of the product resulting from n-hexane activation by the n-alkane-utilizing denitrifying bacterium strain HxN1, i.e. (1-methylpentyl)succinate, were assigned as (2S,1'R) and (2R,1'R). Experiments with stereospecifically deuterated n-(2,5-2H2)hexanes revealed that exclusively the pro-S hydrogen atom is abstracted from C2 of the n-alkane by the enzyme and later transferred back to C3 of the alkylsuccinate formed. These results indicate that the alkylsuccinate-forming reaction proceeds with an inversion of configuration at the carbon atom (C2) of the n-alkane forming the new C-C-bond, and thus stereochemically resembles a SN2-type reaction. Therefore, the reaction may occur in a concerted manner, which may avoid the highly energetic hex-2-yl radical as an intermediate. The reaction is associated with a significant primary kinetic isotope effect (kH/kD ≥3) for hydrogen, indicating that the homolytic C-H-bond cleavage is involved in the first irreversible step of the reaction mechanism. The (1-methylalkyl)succinate synthases of n-alkane-utilizing anaerobic bacteria apparently have very broad substrate ranges enabling them to activate not only aliphatic but also alkyl-aromatic hydrocarbons. Thus, two denitrifiers and one sulfate reducer were shown to convert the nongrowth substrate toluene to benzylsuccinate and further to the dead-end product benzoyl-CoA. For this purpose, however, the modified β-oxidation pathway known from alkylbenzene-utilizing bacteria was not employed, but rather the pathway used for n-alkane degradation involving CoA ligation, carbon skeleton rearrangement and decarboxylation. Furthermore, various n-alkane- and alkylbenzene-utilizing denitrifiers and sulfate reducers were found to be capable of forming benzyl alcohols from diverse alkylbenzenes

Catalytic conversion of light alkanes

Energy Technology Data Exchange (ETDEWEB)

Lyons, J.E.

1992-06-30

The second Quarterly Report of 1992 on the Catalytic Conversion of Light Alkanes reviews the work done between April 1, 1992 and June 31, 1992 on the Cooperative Agreement. The mission of this work is to devise a new catalyst which can be used in a simple economic process to convert the light alkanes in natural gas to oxygenate products that can either be used as clean-burning, high octane liquid fuels, as fuel components or as precursors to liquid hydrocarbon uwspomdon fuel. During the past quarter we have continued to design, prepare, characterize and test novel catalysts for the mild selective reaction of light hydrocarbons with air or oxygen to produce alcohols directly. These catalysts are designed to form active metal oxo (MO) species and to be uniquely active for the homolytic cleavage of the carbon-hydrogen bonds in light alkanes producing intermediates which can form alcohols. We continue to investigate three molecular environments for the active catalytic species that we are trying to generate: electron-deficient macrocycles (PHASE I), polyoxometallates (PHASE II), and regular oxidic lattices including zeolites and related structures as well as other molecular surface structures having metal oxo groups (PHASE I).

Self-consistent field theory of polymer-ionic molecule complexation.

Science.gov (United States)

Nakamura, Issei; Shi, An-Chang

2010-05-21

A self-consistent field theory is developed for polymers that are capable of binding small ionic molecules (adsorbates). The polymer-ionic molecule association is described by Ising-like binding variables, C(i) ((a))(kDelta)(=0 or 1), whose average determines the number of adsorbed molecules, n(BI). Polymer gelation can occur through polymer-ionic molecule complexation in our model. For polymer-polymer cross-links through the ionic molecules, three types of solutions for n(BI) are obtained, depending on the equilibrium constant of single-ion binding. Spinodal lines calculated from the mean-field free energy exhibit closed-loop regions where the homogeneous phase becomes unstable. This phase instability is driven by the excluded-volume interaction due to the single occupancy of ion-binding sites on the polymers. Moreover, sol-gel transitions are examined using a critical degree of conversion. A gel phase is induced when the concentration of adsorbates is increased. At a higher concentration of the adsorbates, however, a re-entrance from a gel phase into a sol phase arises from the correlation between unoccupied and occupied ion-binding sites. The theory is applied to a model system, poly(vinyl alcohol) and borate ion in aqueous solution with sodium chloride. Good agreement between theory and experiment is obtained.

Radiolysis of alanine adsorbed in a clay mineral

Energy Technology Data Exchange (ETDEWEB)

Aguilar-Ovando, Ellen Y.; Negron-Mendoza, Alicia [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior s/n, Ciudad Universitaria, Apartado Postal 70-543, Deleg. Coyoacan, C.P. 04510 (Mexico)

2013-07-03

Optical activity in molecules is a chemical characteristic of living beings. In this work, we examine the hypothesis of the influence of different mineral surfaces on the development of a specific chirality in organic molecules when subjected to conditions simulating the primitive Earth during the period of chemical evolution. By using X-ray diffraction techniques and HPLC/ELSD to analyze aqueous suspensions of amino acids adsorbed on minerals irradiated in different doses with a cobalt-60 gamma source, the experiments attempt to prove the hypothesis that some solid surfaces (like clays and meteorite rocks) may have a concentration capacity and protective role against external sources of ionizing radiation (specifically {gamma}-ray) for some organic compounds (like some amino acids) adsorbed on them. Preliminary results show a slight difference in the adsorption and radiolysis of the D-and L-alanine.

Radiolysis of alanine adsorbed in a clay mineral

International Nuclear Information System (INIS)

Aguilar-Ovando, Ellen Y.; Negrón-Mendoza, Alicia

2013-01-01

Optical activity in molecules is a chemical characteristic of living beings. In this work, we examine the hypothesis of the influence of different mineral surfaces on the development of a specific chirality in organic molecules when subjected to conditions simulating the primitive Earth during the period of chemical evolution. By using X-ray diffraction techniques and HPLC/ELSD to analyze aqueous suspensions of amino acids adsorbed on minerals irradiated in different doses with a cobalt-60 gamma source, the experiments attempt to prove the hypothesis that some solid surfaces (like clays and meteorite rocks) may have a concentration capacity and protective role against external sources of ionizing radiation (specifically γ-ray) for some organic compounds (like some amino acids) adsorbed on them. Preliminary results show a slight difference in the adsorption and radiolysis of the D-and L-alanine

The Dynamics and Structures of Adsorbed Surfaces

DEFF Research Database (Denmark)

Nielsen, M; Ellenson, W. D.; McTague, J. P.

1978-01-01

. Elastic neutron diffraction measurements, determining the two-dimensional structural ordering of the adsorbed films, have been performed on layers of N2, Ar, H2, D2, O2, Kr, and He. Measurements on layers of larger molecules such as CD4 and ND3 have also been reported. Inelastic neutron scattering...... measurements, studying the dynamics of the adsorbed films are only possible in a few especially favourable cases such as 36Ar and D2 films, where the coherent phonon scattering cross-sections are very large. In other cases incoherent scattering from hydrogen can give information about e.g. the mobility...

Calculation of gamma spectra for positron annihilation on molecules

Energy Technology Data Exchange (ETDEWEB)

Green, Dermot G; Gribakin, G F [Centre for Theoretical Atomic, Molecular and Optical Physics, Queen' s University Belfast, BT7 1NN (United Kingdom); Wang, F [Centre for Molecular Simulation, Sinburne University of Technology, Melbourne, Victoria 3122 (Australia); Surko, C M, E-mail: dgreen09@qub.ac.u [Physics Department, University of California, San Diego, La Jolla, California 92093-0319 (United States)

2009-11-01

Gamma spectra for positron annihilation on molecules are calculated based on molecular electron momentum densities and using an atomic adjustment factor that accounts for the positron. Results for H{sub 2} agree well with experiment. Analysis of methane and larger alkanes and their substitutes is underway.

Distribution and sources of n-alkanes in surface sediments of Taihu Lake, China

Directory of Open Access Journals (Sweden)

Yu Yunlong

2016-03-01

Full Text Available The last study on n-alkanes in surface sediments of Taihu Lake was in 2000, only 13 surface sediment samples were analysed, in order to have a comprehensive and up-to-date understanding of n-alkanes in the surface sediments of Taihu Lake, 41 surface sediment samples were analyzed by GC-MS. C10 to C37 were detected, the total concentrations of n-alkanes ranged from 2109 ng g−1 to 9096 ng g−1 (dry weight. There was strong odd carbon predominance in long chain n-alkanes and even carbon predominance in short chain n-alkanes. When this finding was combined with the analysis results of wax n-alkanes (WaxCn, carbon preference index (CPI, unresolved complex mixture (UCM, hopanes and steranes, it was considered that the long chain n-alkanes were mainly from terrigenous higher plants, and that the short chain n-alkanes mainly originated from bacteria and algae in the lake, compared with previous studies, there were no obvious anthropogenic petrogenic inputs. Terrestrial and aquatic hydrocarbons ratio (TAR and C21−/C25+ indicated that terrigenous input was higher than aquatic sources and the nearshore n-alkanes were mainly from land-derived sources. Moreover, the distribution of short chain n-alkanes presented a relatively uniform pattern, while the long chain n-alkanes presented a trend that concentrations dropped from nearshore places to the middle of lake.

Surface-Enhanced Raman Spectroscopy of Dye and Thiol Molecules Adsorbed on Triangular Silver Nano structures: A Study of Near-Field Enhancement, Localization of Hot-Spots, and Passivation of Adsorbed Carbonaceous Species

International Nuclear Information System (INIS)

Goncalves, M.R.; Marti, O.; Fabian Enderle, F.

2012-01-01

Surface-enhanced Raman spectroscopy (SERS) of thiols and dye molecules adsorbed on triangular silver nanostructures was investigated. The SERS hot-spots are localized at the edges and corners of the silver triangular particles. AFM and SEM measurements permit to observe many small clusters formed at the edges of triangular particles fabricated by nanosphere lithography. Finite-element calculations show that near-field enhancements can reach values of more than 200 at visible wavelengths, in the gaps between small spherical particles and large triangular particles, although for the later no plasmon resonance was found at the wavelengths investigated. The regions near the particles showing strong near-field enhancement are well correlated with spatial localization of SERS hot-spots done by confocal microscopy. Silver nanostructures fabricated by thermal evaporation present strong and fast fluctuating SERS activity, due to amorphous carbon contamination. Thiols and dye molecules seem to be able to passivate the undesired SERS activity on fresh evaporated silver. excitation: by far-field illumination of metal nanostructures or rough metal Raman scattering cross-section of gold-palladium target Temporal Fluctuation in SERS Temporal and spectral fluctuations.

H-Abstraction by OH from Large Branched Alkanes: Overall Rate Measurements and Site-Specific Tertiary Rate Calculations

KAUST Repository

Liu, Dapeng

2017-01-10

Reaction rate coefficients for the reaction of hydroxyl (OH) radicals with nine large branched alkanes (i.e., 2-methyl-3-ethyl-pentane, 2,3-dimethyl-pentane, 2,2,3-trimethylbutane, 2,2,3-trimethyl-pentane, 2,3,4-trimethyl-pentane, 3-ethyl-pentane, 2,2,3,4-tetramethyl-pentane, 2,2-dimethyl-3-ethyl-pentane, and 2,4-dimethyl-3-ethyl-pentane) are measured at high temperatures (900-1300 K) using a shock tube and narrow-line-width OH absorption diagnostic in the UV region. In addition, room-temperature measurements of six out of these nine rate coefficients are performed in a photolysis cell using high repetition laser-induced fluorescence of OH radicals. Our experimental results are combined with previous literature measurements to obtain three-parameter Arrhenius expressions valid over a wide temperature range (300-1300 K). The rate coefficients are analyzed using the next-nearest-neighbor (N-N-N) methodology to derive nine tertiary (T003, T012, T013, T022, T023, T111, T112, T113, and T122) site-specific rate coefficients for the abstraction of H atoms by OH radicals from branched alkanes. Derived Arrhenius expressions, valid over 950-1300 K, are given as (the subscripts denote the number of carbon atoms connected to the next-nearest-neighbor carbon): T003 = 1.80 × 10-10 exp(-2971 K/T) cm3 molecule-1 s-1; T012 = 9.36 × 10-11 exp(-3024 K/T) cm3 molecule-1 s-1; T013 = 4.40 × 10-10 exp(-4162 K/T) cm3 molecule-1 s-1; T022 = 1.47 × 10-10 exp(-3587 K/T) cm3 molecule-1 s-1; T023 = 6.06 × 10-11 exp(-3010 K/T) cm3 molecule-1 s-1; T111 = 3.98 × 10-11 exp(-1617 K/T) cm3 molecule-1 s-1; T112 = 9.08 × 10-12 exp(-3661 K/T) cm3 molecule-1 s-1; T113 = 6.74 × 10-9 exp(-7547 K/T) cm3 molecule-1 s-1; T122 = 3.47 × 10-11 exp(-1802 K/T) cm3 molecule-1 s-1.

Electronic properties of adsorbates and clean surfaces of metals and semiconductors

International Nuclear Information System (INIS)

Lecante, J.

1980-01-01

This paper surveys recent progress in experimental studies on electronic properties of adsorbates and clean metal surfaces. Electron spectroscopy and particularly angle resolved photoelectron spectroscopy appears to be a very powerful tool to get informations on electronic levels of adsorbates or clean surfaces. Moreover this technique may also give informations about the atomic geometry of the surface. Experimental investigation about surface plasmons, surface states, core level shifts are presented for clean surfaces. As examples of adsorbate covered surfaces two typical cases are chosen: two dimensional band structure and oriented molecules. Finally the photoelectron diffraction may be used for surface structure determination either in the case of an adsorbate or a clean metal surface [fr

Optimized reaction mechanism rate rules for ignition of normal alkanes

KAUST Repository

Cai, Liming

2016-08-11

The increasing demand for cleaner combustion and reduced greenhouse gas emissions motivates research on the combustion of hydrocarbon fuels and their surrogates. Accurate detailed chemical kinetic models are an important prerequisite for high fidelity reacting flow simulations capable of improving combustor design and operation. The development of such models for many new fuel components and/or surrogate molecules is greatly facilitated by the application of reaction classes and rate rules. Accurate and versatile rate rules are desirable to improve the predictive accuracy of kinetic models. A major contribution in the literature is the recent work by Bugler et al. (2015), which has significantly improved rate rules and thermochemical parameters used in kinetic modeling of alkanes. In the present study, it is demonstrated that rate rules can be used and consistently optimized for a set of normal alkanes including n-heptane, n-octane, n-nonane, n-decane, and n-undecane, thereby improving the predictive accuracy for all the considered fuels. A Bayesian framework is applied in the calibration of the rate rules. The optimized rate rules are subsequently applied to generate a mechanism for n-dodecane, which was not part of the training set for the optimized rate rules. The developed mechanism shows accurate predictions compared with published well-validated mechanisms for a wide range of conditions.

SFG investigation of adsorbed CO and NO on NiO(111) surface

Energy Technology Data Exchange (ETDEWEB)

Bandara, Athula; Dobashi, Shinsaku; Kubota, Jun; Onda, Ken; Wada, Akihide; Domen, Kazunari; Hirose, Chiaki [Tokyo Inst. of Tech., Yokohama (Japan). Research Lab. of Resources Utilization; Kano, S.S.

1997-07-01

Adsorption structures of CO and NO on the NiO(111) film grown on Ni(111) crystal have been investigated by sum frequency generation (SFG) spectroscopy and infrared reflection absorption spectroscopy (IRAS). The CO stretching band of adsorbed CO on NiO(111) was observed at 2144 cm{sup -1} on the SFG spectra for both p- and s-polarized visible light. However, adsorbed NO on NiO(111) was observed at 1805 cm{sup -1} on the SFG spectra only for the p-polarized visible light. The results suggest that the adsorbed CO molecule was tilted from the surface normal but the NO molecule was perpendicular to the surface. These orientations of CO and NO reflect the surface structure of NiO(111) which has (2 x 2)-reconstructed microfacets. Adsorption of CO on Ni(111) instead of NiO(111) was also examined by SFG and IRAS. Absorption bands due to linear and bridged CO were observed at 2076 and 1918 cm{sup -1}, respectively, by IRAS. On the other hand, the linear CO molecules on Ni(111) gave an SFG peak at 2076 cm{sup -1} only for the p-polarized visible light indicating the CO molecules are perpendicular to the surface, and bridged CO molecules did not give any SFG signal. The absence of the bridged CO signal is believed to be due to the smaller Raman tensor of bridged CO. (author)

SFG investigation of adsorbed CO and NO on NiO(111) surface

International Nuclear Information System (INIS)

Bandara, Athula; Dobashi, Shinsaku; Kubota, Jun; Onda, Ken; Wada, Akihide; Domen, Kazunari; Hirose, Chiaki; Kano, S.S.

1997-01-01

Adsorption structures of CO and NO on the NiO(111) film grown on Ni(111) crystal have been investigated by sum frequency generation (SFG) spectroscopy and infrared reflection absorption spectroscopy (IRAS). The CO stretching band of adsorbed CO on NiO(111) was observed at 2144 cm -1 on the SFG spectra for both p- and s-polarized visible light. However, adsorbed NO on NiO(111) was observed at 1805 cm -1 on the SFG spectra only for the p-polarized visible light. The results suggest that the adsorbed CO molecule was tilted from the surface normal but the NO molecule was perpendicular to the surface. These orientations of CO and NO reflect the surface structure of NiO(111) which has (2 x 2)-reconstructed microfacets. Adsorption of CO on Ni(111) instead of NiO(111) was also examined by SFG and IRAS. Absorption bands due to linear and bridged CO were observed at 2076 and 1918 cm -1 , respectively, by IRAS. On the other hand, the linear CO molecules on Ni(111) gave an SFG peak at 2076 cm -1 only for the p-polarized visible light indicating the CO molecules are perpendicular to the surface, and bridged CO molecules did not give any SFG signal. The absence of the bridged CO signal is believed to be due to the smaller Raman tensor of bridged CO. (author)

Structural and electronic properties of the adsorbed and defected Cu nanowires: A density-functional theory study

Energy Technology Data Exchange (ETDEWEB)

Duan, Ying-Ni [College of Physics and Information Technology, Shaanxi Normal University, Xian 710062, Shaanxi (China); Department of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830011, Xinjiang (China); Zhang, Jian-Min, E-mail: jianm_zhang@yahoo.com [College of Physics and Information Technology, Shaanxi Normal University, Xian 710062, Shaanxi (China); Fan, Xiao-Xi [Department of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830011, Xinjiang (China); Xu, Ke-Wei [College of Physics and Mechanical and Electronic Engineering, Xian University of Arts and Science, Xian 710065, Shaanxi (China)

2014-12-01

Using first-principles calculations based on density-functional theory, we systematically investigate the influence of adsorbates (CO molecule and O atom) and defects (adsorb one extra Cu atom and monovacancy) on the structural and electronic properties of Cu{sub 5-1}NW and Cu{sub 6-1}NW. For both nanowires, CO molecule prefers to adsorb on the top site, while O atom prefers to adsorb on the center site. The hybridization between the CO and Cu states is dominated by the donation–backdonation process, which leads to the formation of bonding/antibonding pairs, 5σ{sub b}/5σ{sub a} and 2π{sub b}{sup ⁎}/2π{sub a}{sup ⁎}. The larger adsorption energies, larger charge transfers to O adatom and larger decrease in quantum conductance 3G{sub 0} for an O atom adsorbed on the Cu{sub 5-1}NW and Cu{sub 6-1}NW show both Cu{sub 5-1}NW and Cu{sub 6-1}NW can be used as an O sensor. Furthermore, the decrease in quantum conductance 1G{sub 0} for a CO molecule adsorbed on the Cu{sub 6-1}NW also shows the Cu{sub 6-1}NW can be used to detect CO molecule. So we expect these results may have implications for CuNW based chemical sensing. High adsorption energy of one extra Cu atom and relatively low formation energy of a monovacancy suggest that these two types of defects are likely to occur in the fabrication of CuNWs. One extra Cu atom does not decrease the quantum conductance, while a Cu monovacancy leads to a drop of the quantum conductance.

Oxidative addition of C--H bonds in organic molecules to transition metal centers

International Nuclear Information System (INIS)

Bergman, R.G.

1989-04-01

Alkanes are among the most chemically inert organic molecules. They are reactive toward a limited range of reagents, such as highly energetic free radicals and strongly electrophilic and oxidizing species. This low reactivity is a consequence of the C--H bond energies in most saturated hydrocarbons. These values range from 90 to 98 kcal/mole for primary and secondary C--H bonds; in methane, the main constituent of natural gas, the C--H bond energy is 104 kcal/mole. This makes methane one of the most common but least reactive organic molecules in nature. This report briefly discusses the search for metal complexes capable of undergoing the C--H oxidative addition process allowing alkane chemistry to be more selective than that available using free radical reagents. 14 refs

Synthesis of Renewable Lubricant Alkanes from Biomass-Derived Platform Chemicals.

Science.gov (United States)

Gu, Mengyuan; Xia, Qineng; Liu, Xiaohui; Guo, Yong; Wang, Yanqin

2017-10-23

The catalytic synthesis of liquid alkanes from renewable biomass has received tremendous attention in recent years. However, bio-based platform chemicals have not to date been exploited for the synthesis of highly branched lubricant alkanes, which are currently produced by hydrocracking and hydroisomerization of long-chain n-paraffins. A selective catalytic synthetic route has been developed for the production of highly branched C 23 alkanes as lubricant base oil components from biomass-derived furfural and acetone through a sequential four-step process, including aldol condensation of furfural with acetone to produce a C 13 double adduct, selective hydrogenation of the adduct to a C 13 ketone, followed by a second condensation of the C 13 ketone with furfural to generate a C 23 aldol adduct, and finally hydrodeoxygenation to give highly branched C 23 alkanes in 50.6 % overall yield from furfural. This work opens a general strategy for the synthesis of high-quality lubricant alkanes from renewable biomass. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption of diclofenac and nimesulide on activated carbon: Statistical physics modeling and effect of adsorbate size

Science.gov (United States)

Sellaoui, Lotfi; Mechi, Nesrine; Lima, Éder Cláudio; Dotto, Guilherme Luiz; Ben Lamine, Abdelmottaleb

2017-10-01

Based on statistical physics elements, the equilibrium adsorption of diclofenac (DFC) and nimesulide (NM) on activated carbon was analyzed by a multilayer model with saturation. The paper aimed to describe experimentally and theoretically the adsorption process and study the effect of adsorbate size using the model parameters. From numerical simulation, the number of molecules per site showed that the adsorbate molecules (DFC and NM) were mostly anchored in both sides of the pore walls. The receptor sites density increase suggested that additional sites appeared during the process, to participate in DFC and NM adsorption. The description of the adsorption energy behavior indicated that the process was physisorption. Finally, by a model parameters correlation, the size effect of the adsorbate was deduced indicating that the molecule dimension has a negligible effect on the DFC and NM adsorption.

Geomicrobiological linkages between short-chain alkane consumption and sulfate reduction rates in seep sediments.

Directory of Open Access Journals (Sweden)

Arpita eBose

2013-12-01

Full Text Available Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C2-C5 and longer alkanes. C2-C4 alkanes such as ethane, propane and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C1-C4 then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist. Changes in the δ13C of all the alkanes in the reactors show enrichment over the course of the incubation, with the C3 and C4 incubations showing the greatest enrichment (4.4‰ and 4.5‰ respectively. The concurrent depletion in the δ13C of dissolved inorganic carbon (DIC implies a transfer of carbon from the alkane to the DIC pool (-3.5 and -6.7‰ for C3 and C4 incubations, respectively. Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C1-C4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3-C4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community

First-principles investigations of electronic and magnetic properties of SrTiO3 (001) surfaces with adsorbed ethanol and acetone molecules

Science.gov (United States)

Adeagbo, Waheed A.; Fischer, Guntram; Hergert, Wolfram

2011-05-01

First-principles methods based on density functional theory are used to investigate the electronic and magnetic properties of molecular interaction of the TiO2 terminated SrTiO3 (100) surface with ethanol or acetone. Both the perfect surface and the surface with an oxygen or a titanium vacancy in the top layer are considered. Ethanol and acetone are preferentially adsorbed molecularly via their respective oxygen atom on top of the Ti atom on the perfect surface. In case of an oxygen vacancy the adsorption of ethanol or acetone occurs directly on top of the vacancy and does not significantly affect the magnetism caused by the vacancy. In the case of a titanium vacancy both adsorbates occupy positions above Ti atoms. During this adsorption process the ethanol molecule dissociates into a CH3CO radical and three hydrogen atoms. The latter form hydroxide bonds with three of the four dangling oxygen bonds around the Ti vacancy and any magnetic moment induced by the Ti vacancy is annihilated. Thus the ethanol and acetone have a different impact on the surface magnetism of the SrTiO3 (100) surface.

Probing the dynamics of 3He atoms adsorbed on MCM-41 with pulsed NMR

Science.gov (United States)

Huan, C.; Masuhara, N.; Adams, J.; Lewkowitz, M.; Sullivan, N. S.

2018-03-01

We report measurements of the nuclear spin-spin and spin-lattice relaxation times for 3He adsorbed on MCM-41 for temperatures 0.08 < T < 1.2 K. Deviations from Curie behavior are observed at low temperatures. The relaxation times exhibit a two-component behavior representing the differing dynamics of the mobile quasi-free molecules in the center of the tubes compared to the adsorbed layer on the walls. The amplitudes of the two components provide an accurate measure of the number of fluid-like molecules traveling in the center of the nanotubes.

Ethene/ethane and propene/propane separation via the olefin and paraffin selective metal-organic framework adsorbents CPO-27 and ZIF-8.

Science.gov (United States)

Böhme, Ulrike; Barth, Benjamin; Paula, Carolin; Kuhnt, Andreas; Schwieger, Wilhelm; Mundstock, Alexander; Caro, Jürgen; Hartmann, Martin

2013-07-09

Two types of metal-organic frameworks (MOFs) have been synthesized and evaluated in the separation of C2 and C3 olefins and paraffins. Whereas Co2(dhtp) (=Co-CPO-27 = Co-MOF-74) and Mg2(dhtp) show an adsorption selectivity for the olefins ethene and propene over the paraffins ethane and propane, the zeolitic imidazolate framework ZIF-8 behaves in the opposite way and preferentially adsorbs the alkane. Consequently, in breakthrough experiments, the olefins or paraffins, respectively, can be separated.

Studies of ethylene hydrogenation and of adsorbed C/sub 2/H/sub 4/ and H/sub 2/ on chromia and lanthana catalysts

Energy Technology Data Exchange (ETDEWEB)

Khodakov, Y.S.; Makarov, P.A.; Delzer, G.; Minachev, K.M.

1980-01-01

Temperature-programed desorption of ethylene or hydrogen adsorbed at -78/sup 0/, -68/sup 0/, and +20/sup 0/C on chromic oxide, a 1:7 chromic oxide/alumina catalyst prepared by impregnation, alumina, and lanthanum oxide pretreated at 400/sup 0/-900/sup 0/C in vacuo showed that ethylene adsorbed on these oxides on three different sites from which it desorbed at -40/sup 0/ to +10/sup 0/C, at 50/sup 0/-100/sup 0/C, and at 350/sup 0/-400/sup 0/C; and that hydrogen adsorbed only on the latter two sites. One preadsorbed ethylene molecule was displaced at room temperature by 16 molecules of carbon monoxide, 79 molecules of carbon dioxide, or 135 molecules of water. Hydrogen was displaced at lower temperature. The nature of the surface sites and of the adsorbed species, and their reactivities are discussed.

Selective conversion of butane into liquid hydrocarbon fuels on alkane metathesis catalysts

KAUST Repository

Szeto, Kaï Chung

2012-01-01

We report a selective direct conversion of n-butane into higher molecular weight alkanes (C 5+) by alkane metathesis reaction catalysed by silica-alumina supported tungsten or tantalum hydrides at moderate temperature and pressure. The product is unprecedented, asymmetrically distributed towards heavier alkanes. This journal is © 2012 The Royal Society of Chemistry.

NMR diffusion and relaxation measurements of organic molecules adsorbed in porous media

International Nuclear Information System (INIS)

Gjerdaaker, Lars

2002-01-01

a bipolar form of the pulsed field gradient has proved to be an efficient method for both reducing the cross-term between the applied and internal gradient and reducing the eddy current dead time. Without the use of a bipolar sequence, the measured diffusivities are likely to be underestimated. In order to get sufficient attenuation of the signal a stimulated-echo sequence together with magnetic field gradients have been used. It was then possible to increase the z-storage period to compensate for insufficient gradient strength. However, the employed diffusion probe and gradient power supply are able to generate magnetic field gradients that make the z-storage period unnecessary. In this work we also present a spin-echo analogue to the 13-interval PFGSTE sequence presented by Cotts et al., a so-called 11-interval bipolar PFGSE sequence. Conclusions: The molecular dynamics of four organic adsorbates confined in porous materials have been investigated. The confinement gives rise to substantial changes in the phase behaviour and molecular dynamics. From the line shape of the confined substances a narrow-line component superimposed on a broad resonance is observed at temperatures well below the transition point of the bulk material. This narrow-line component is, in the freezing region, attributed to the surface layer and the undercooled liquid in the smaller pores that remains unfrozen. In the low-temperature region, the narrow-line component corresponds to the surface layer, while the broad component originates from the crystalline phase at the centre of the pores. The persistent surface layer does not appear to crystallize at all, and a relatively high diffusion rate of this liquid-like phase is observed over a wide temperature range, even well below the transition point of the bulk material. However, with decreasing temperature T2 of the molecules in the surface layer becomes shorter and the contribution to the NMR signal decreases gradually. For pivalic acid and

Role of adsorbates on current fluctuations in DC field emission

International Nuclear Information System (INIS)

Luong, M.; Bonin, B.; Long, H.; Safa, H.

1996-01-01

Field emission experiments in DC regime usually show important current fluctuations for a fixed electric field. These fluctuations are attributed to adsorbed layers (molecules or atoms), liable to affect the work function, height and shape of the potential barrier binding the electron in the metal. The role of these adsorbed species is investigated by showing that the field emission from a well desorbed sample is stable and reproducible and by comparing the emission from the same sample before and after desorption. (author)

Atomic-Scale Control of Electron Transport through Single Molecules

DEFF Research Database (Denmark)

Wang, Y. F.; Kroger, J.; Berndt, R.

2010-01-01

Tin-phthalocyanine molecules adsorbed on Ag(111) were contacted with the tip of a cryogenic scanning tunneling microscope. Orders-of-magnitude variations of the single-molecule junction conductance were achieved by controllably dehydrogenating the molecule and by modifying the atomic structure...

Adsorbed layers on (111)InAs faces in contact with In-As-Cl-H gas phase, and the possibility of phase transitions in the adsorbed layers

Science.gov (United States)

Chernov, A. A.; Ruzaikin, M. P.

1981-04-01

Adsorption of various species existing in the In-As-Cl-H CVD gaseous system on both InAs (111) faces is considered. Arsenic is supposed to be adsorbed in the form of triangles As 3 and tetrahedrons As 4, each of them occupying 3 atomic sites above In or As atoms on (111)In or (111)As, respectively. The system of polyatomic adsorption equations was used to find the coverages of the faces by various species. Admolecule-surface bond strengths are taken to be equal to the ones for the single bonds in molecules. Pauling electronegativities were used to find the effective charges of the atoms in the adsorption layer. Thus, the dipole moments of adsorbed molecules which arise are directed along the In-As bonds in the InAs lattice. With this geometry, the calculated electrostatic dipole-dipole attraction between InCl molecules forming a dense layer on (111)As exceeds 12 kcal/mol. Thus, condensation of the two-dimensional gas of adsorbed InCl molecules should be expected. Corresponding S-shape isotherms θ( P) are calculated for different As 3 vapor pressures, θ and P being the surface coverage and bulk vapor pressure of InCl. Intervals of {InCl 3}/{H 2} ratios at different temperatures where the two-dimensional condensation may occur, are presented for realistic CVD conditions. Two-dimensional condensation may result in sharp changes in kinetic coefficient and thus in autho-oscillations in growth rate and doping level creating periodic superstructures. Nucleation and CVD growth processes are discussed.

A study of binuclear zirconium hydride catalysts of the hydrogenolysis of alkanes by the density functional theory method

Science.gov (United States)

Ustynyuk, L. Yu.; Fast, A. S.; Ustynyuk, Yu. A.; Lunin, V. V.

2012-06-01

Binuclear hydride centers containing two Zr(IV) atoms are suggested as promising catalysts for the hydrogenolysis of alkanes under mild conditions ( T model compounds L2(H)Zr(X)2Zr(H)L2 (X = H, L = OSi≡ ( 4a), X = L = OMe ( 4d)), L(H)Zr(O)2Zr(H)L (L = OSi≡ ( 4b), Cp( 4c)) and (≡SiO)2(H)Zr-O-Zr(H)(OSi≡)2 ( 4e and 4f) with the propane molecule were studied using the density functional theory method. The results show that centers of the 4a, 4e, and 4f types and especially 4b are promising catalysts of the hydrogenolysis of alkanes due to a high degree of unsaturation of two Zr atoms and their sequential participation in the splitting of the C-C bond and hydrogenation of ethylene formed as a result of splitting.

Hydrothermal conversion of cellulose to alkanes with in-situ hydrogen

Energy Technology Data Exchange (ETDEWEB)

Yin, Sudong; Tan, Zhongchao [Department of Mechanical and Mechatronics Engineering, University of Waterloo (Canada)], Email: tanz@uwaterloo.ca

2011-07-01

A recently study examined the probability of hydrothermal conversion of cellulose to alkanes with in-situ H2 instead of external H2. This paper discusses the results of that study. The study researched the effects of volumetric ratios of initial input water to the reactor (W/R) and of selected catalysts on the alkane yields and composition. It was found that with the proper W/R ratios, the reforming of steam in the steam gas phase would automatically produce in-situ H2 and the key was to maintain the right balance of steam phase and liquid phase in the reactor. All the study results conclude that direct hydrothermal conversion of cellulose to alkanes with in-situ H2 is technically feasible. In addition, the application of this technology would protect the alkane bio-oil production biomass from the impact of unstable external supply of H2.

Enhanced binding capacity of boronate affinity adsorbent via surface modification of silica by combination of atom transfer radical polymerization and chain-end functionalization for high-efficiency enrichment of cis-diol molecules

Energy Technology Data Exchange (ETDEWEB)

Wang, Wei; He, Maofang; Wang, Chaozhan; Wei, Yinmao, E-mail: ymwei@nwu.edu.cn

2015-07-30

Boronate affinity materials have been widely used for specific separation and preconcentration of cis-diol molecules, but most do not have sufficient capacity due to limited binding sites on the material surface. In this work, we prepared a phenylboronic acid-functionalized adsorbent with a high binding capacity via the combination of surface-initiated atom transfer radical polymerization (SI-ATRP) and chain-end functionalization. With this method, the terminal chlorides of the polymer chains were used fully, and the proposed adsorbent contains dense boronic acid polymers chain with boronic acid on the chain end. Consequently, the proposed adsorbent possesses excellent selectivity and a high binding capacity of 513.6 μmol g{sup −1} for catechol and 736.8 μmol g{sup −1} for fructose, which are much higher than those of other reported adsorbents. The dispersed solid-phase extraction (dSPE) based on the prepared adsorbent was used for extraction of three cis-diol drugs (i.e., epinephrine, isoprenaline and caffeic acid isopropyl ester) from plasma; the eluates were analyzed by HPLC-UV. The reduced amount of adsorbent (i.e., 2.0 mg) could still eliminate interferences efficiently and yielded a recovery range of 85.6–101.1% with relative standard deviations ranging from 2.5 to 9.7% (n = 5). The results indicated that the proposed strategy could serve as a promising alternative to increase the density of surface functional groups on the adsorbent; thus, the prepared adsorbent has the potential to effectively enrich cis-diol substances in real samples. - Highlights: • Boronate adsorbent is prepared via ATRP and chain-end functionalization. • The adsorbent has quite high binding capacity for cis-diols. • Binding capacity is easily manipulated by ATRP condition. • Chain-end functionalization can improve binding capacity significantly. • Reduced adsorbent is consumed in dispersed solid-phase extraction of cis-diols.

Distribution of metal and adsorbed guest species in zeolites

Energy Technology Data Exchange (ETDEWEB)

Chmelka, B.F.

1989-12-01

Because of their high internal surface areas and molecular-size cavity dimensions, zeolites are used widely as catalysts, shape- selective supports, or adsorbents in a variety of important chemical processes. For metal-catalyzed reactions, active metal species must be dispersed to sites within the zeolite pores that are accessible to diffusing reactant molecules. The distribution of the metal, together with transport and adsorption of reactant molecules in zeolite powders, are crucial to ultimate catalyst performance. The nature of the metal or adsorbed guest distribution is known, however, to be dramatically dependent upon preparatory conditions. Our objective is to understand, at the molecular level, how preparatory treatments influence the distribution of guest species in zeolites, in order that macroscopic adsorption and reaction properties of these materials may be better understood. The sensitivity of xenon to its adsorption environment makes {sup 129}Xe NMR spectroscopy an important diagnostic probe of metal clustering and adsorbate distribution processes in zeolites. The utility of {sup 129}Xe NMR depends on the mobility of the xenon atoms within the zeolite-guest system, together with the length scale of the sample heterogeneity being studied. In large pore zeolites containing dispersed guest species, such as Pt--NaY, {sup 129}Xe NMR is insensitive to fine structural details at room temperature.

Distribution of metal and adsorbed guest species in zeolites

International Nuclear Information System (INIS)

Chmelka, B.F.

1989-12-01

Because of their high internal surface areas and molecular-size cavity dimensions, zeolites are used widely as catalysts, shape- selective supports, or adsorbents in a variety of important chemical processes. For metal-catalyzed reactions, active metal species must be dispersed to sites within the zeolite pores that are accessible to diffusing reactant molecules. The distribution of the metal, together with transport and adsorption of reactant molecules in zeolite powders, are crucial to ultimate catalyst performance. The nature of the metal or adsorbed guest distribution is known, however, to be dramatically dependent upon preparatory conditions. Our objective is to understand, at the molecular level, how preparatory treatments influence the distribution of guest species in zeolites, in order that macroscopic adsorption and reaction properties of these materials may be better understood. The sensitivity of xenon to its adsorption environment makes 129 Xe NMR spectroscopy an important diagnostic probe of metal clustering and adsorbate distribution processes in zeolites. The utility of 129 Xe NMR depends on the mobility of the xenon atoms within the zeolite-guest system, together with the length scale of the sample heterogeneity being studied. In large pore zeolites containing dispersed guest species, such as Pt--NaY, 129 Xe NMR is insensitive to fine structural details at room temperature

Equilibrium and heat of adsorption of diethyl phthalate on heterogeneous adsorbents

Energy Technology Data Exchange (ETDEWEB)

Zhang, W.M.; Xu, Z.W.; Pan, B.C.; Hong, C.H.; Jia, K.; Jiang, P.J.; Zhang, Q.J.; Pan, B.J. [Nanjing University, Nanjing (China)

2008-09-15

Removal of phthalate esters from water has been of considerable concern recently. In the present study, the adsorptive removal performance of diethyl phthalate (DEP) from water was investigated with the aminated polystyrene resin (NDA-101) and oxidized polystyrene resin (NDA-702). In addition, the commercial homogeneous polystyrene resin (XAD-4) and acrylic ester resin (Amberlite XAD-7) as well as coal-based granular activated carbon (AC-750) were chosen for comparison. The corresponding equilibrium isotherms are well described by the Freundlich equation and the adsorption capacities for DEP followed the order NDA-702 > NDA-101 > AC-750 > XAD-4 > XAD-7. Analysis of adsorption mechanisms suggested that these adsorbents spontaneously adsorb DEP molecules driven mainly by enthalpy change, and the adsorption process was derived by multiple adsorbent-adsorbate interactions such as hydrogen bonding, {pi}-{pi} stacking, and micropore filling. The information related to the adsorbent surface heterogeneity and the adsorbate-adsorbate interaction was obtained by Do's model. All the results indicate that heterogeneous resins NDA-702 and NDA-101 have excellent potential as an adsorption material for the removal of DEP from the contaminated water.

Transport through a Single Octanethiol Molecule

NARCIS (Netherlands)

Kockmann, D.; Poelsema, Bene; Zandvliet, Henricus J.W.

2009-01-01

Octanethiol molecules adsorbed on Pt chains are studied with scanning tunneling microscopy and spectroscopy at 77 K. The head of the octanethiol binds to a Pt atom and the tail is lying flat down on the chain. Open-loop current time traces reveal that the molecule wags its tail and attaches to the

Biobased production of alkanes and alkenes through metabolic engineering of microorganisms

DEFF Research Database (Denmark)

Kang, Min Kyoung; Nielsen, Jens

2017-01-01

Advancement in metabolic engineering of microorganisms has enabled bio-based production of a range of chemicals, and such engineered microorganism can be used for sustainable production leading to reduced carbon dioxide emission there. One area that has attained much interest is microbial...... hydrocarbon biosynthesis, and in particular, alkanes and alkenes are important high-value chemicals as they can be utilized for a broad range of industrial purposes as well as ‘drop-in’ biofuels. Some microorganisms have the ability to biosynthesize alkanes and alkenes naturally, but their production level...... is extremely low. Therefore, there have been various attempts to recruit other microbial cell factories for production of alkanes and alkenes by applying metabolic engineering strategies. Here we review different pathways and involved enzymes for alkane and alkene production and discuss bottlenecks...

Many-body dispersion effects in the binding of adsorbates on metal surfaces

Energy Technology Data Exchange (ETDEWEB)

Maurer, Reinhard J. [Department of Chemistry, Yale University, New Haven, Connecticut 06520 (United States); Ruiz, Victor G.; Tkatchenko, Alexandre [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany)

2015-09-14

A correct description of electronic exchange and correlation effects for molecules in contact with extended (metal) surfaces is a challenging task for first-principles modeling. In this work, we demonstrate the importance of collective van der Waals dispersion effects beyond the pairwise approximation for organic–inorganic systems on the example of atoms, molecules, and nanostructures adsorbed on metals. We use the recently developed many-body dispersion (MBD) approach in the context of density-functional theory [Tkatchenko et al., Phys. Rev. Lett. 108, 236402 (2012) and Ambrosetti et al., J. Chem. Phys. 140, 18A508 (2014)] and assess its ability to correctly describe the binding of adsorbates on metal surfaces. We briefly review the MBD method and highlight its similarities to quantum-chemical approaches to electron correlation in a quasiparticle picture. In particular, we study the binding properties of xenon, 3,4,9,10-perylene-tetracarboxylic acid, and a graphene sheet adsorbed on the Ag(111) surface. Accounting for MBD effects, we are able to describe changes in the anisotropic polarizability tensor, improve the description of adsorbate vibrations, and correctly capture the adsorbate–surface interaction screening. Comparison to other methods and experiment reveals that inclusion of MBD effects improves adsorption energies and geometries, by reducing the overbinding typically found in pairwise additive dispersion-correction approaches.

Structure of solid surfaces and of adsorbates by low-energy electron diffraction

International Nuclear Information System (INIS)

Somorjai, G.A.

1977-01-01

LEED theory has developed to the point where the diffraction beam intensities can be computed using the locations of the surface atoms as the only adjustable parameters. The position of atoms in many clean monatomic solid surfaces and the surface structures of ordered monolayers of adsorbed atoms have been determined this way. Surface crystallography studies are now extended to small hydrocarbon molecules that are adsorbed on metal surfaces. These studies are reviewed

Structure formation in bis(terpyridine) derivative adlayers: molecule-substrate versus molecule-molecule interactions.

Science.gov (United States)

Hoster, Harry E; Roos, Matthias; Breitruck, Achim; Meier, Christoph; Tonigold, Katrin; Waldmann, Thomas; Ziener, Ulrich; Landfester, Katharina; Behm, R Jürgen

2007-11-06

The influence of the substrate and the deposition conditions-vapor deposition versus deposition from solution-on the structures formed upon self-assembly of deposited bis(terpyridine) derivative (2,4'-BTP) monolayers on different hexagonal substrates, including highly oriented pyrolytic graphite (HOPG), Au(111), and (111)-oriented Ag thin films, was investigated by high-resolution scanning tunneling microscopy and by model calculations of the intermolecular energies and the lateral corrugation of the substrate-adsorbate interaction. Similar quasi-quadratic network structures with almost the same lattice constants obtained on all substrates are essentially identical to the optimum configuration expected from an optimization of the adlayer structure with C-H...N-type bridging bonds as a structure-determining factor, which underlines a key role of the intermolecular interactions in adlayer order. Slight distortions from the optimum values to form commensurate adlayer structures on the metal substrates and the preferential orientation of the adlayer with respect to the substrate are attributed to the substrate-adsorbate interactions, specifically, the lateral corrugation in the substrate-adsorbate interaction upon lateral displacement and rotation of the adsorbed BTP molecules. The fact that similar adlayer structures are obtained on HOPG under ultrahigh vacuum conditions (solid|gas interface) and on HOPG in trichlorobenzene (solid|liquid interface) indicates that the intermolecular interactions are not severely affected by the solvent.

Characterisation of lignite as an industrial adsorbent

Energy Technology Data Exchange (ETDEWEB)

Ying Qi; Andrew F.A. Hoadley; Alan L. Chaffee; Gil Garnier [Monash University, Clayton, Vic. (Australia). Department of Chemical Engineering

2011-04-15

An alternative use of the abundant and inexpensive lignite (also known as brown coal) as an industrial adsorbent has been characterised. The adsorptive properties of two Victorian lignite without any pre-treatment were investigated using the cationic methylene blue dye as a model compound in aqueous solutions. Two commercial activated carbon products were also studied for comparison. The adsorption equilibrium of the four adsorbents was better described by the Langmuir isotherm model than the Freundlich model. The adsorption capacities of the two untreated lignite adsorbents, Loy Yang and Yallourn, calculated using Langmuir isotherms were 286 and 370 mg/g, respectively, higher than a coconut shell-based activated carbon (167 mg/g), but lower than a coal-based activated carbon (435 mg/g). Surface area results suggested that larger micropores and mesopores were important for achieving good methylene blue adsorption by the activated carbons. However, FTIR and cation exchange capacity analyses revealed that, for the lignite, chemical interactions between lignite surface functional groups and methylene blue molecules occurred, thereby augmenting its adsorption capacity. 63 refs., 3 figs., 7 tabs.

Transporting method for adsorbing tower and the adsorbing tower

International Nuclear Information System (INIS)

Shimokawa, Nobuhiro.

1996-01-01

A cylindrical plastic bag is disposed to the upper surface of an adsorbing tower so as to surround a suspending piece. One opening of the bag is sealed, and other opening is secured in a sealed state to a bag holding portion disposed to glove box at a gate for the adsorbing tower box. The adsorbing tower is transported into the glove box, and after the completion of the operation of the adsorbing tower, the adsorbing tower is taken out in a state that the bag is restricted and sealed at a portion below the adsorbing tower. The bag may be made of a vinyl plastic, the bag holding portion may be a short-cylindrical protrusion, and may have an O-ring groove at the outer surface. Even if the adsorbing tower is heavy, the adsorbing tower can be carried out easily in a state where it is sealed gas tightly. (N.H.)

Kinetics of the homogeneous exchange of alpha-lactalbumin adsorbed on titanium oxide surface.

Science.gov (United States)

Bentaleb, A; Haïkel, Y; Voegel, J C; Schaaf, P

1998-06-05

The homogeneous exchange process whereby alpha-lactalbumine molecules adsorbed on hydrophilic titanium oxide particles are replaced by alpha-lactalbumine molecules in solution has been investigated by means of a 125I radio-labeling technique, alpha-lactalbumine is a compact and highly negatively charged protein, making this study complementary to previous work devoted to the general understanding of the exchange mechanisms of adsorbed proteins on solid surfaces. The isotherm of alpha-lactalbumine exhibits bimodal adsorption shape, and the exchange process whereby adsorbed proteins are replaced by new incoming ones from the bulk solution has been studied at both the upper and the lower plateau of the isotherm. In the upper plateau the exchange process was found to be of first order with respect to the bulk molecules, and the release rate constant was equal to 0.914 L. mol-1.s-1. This behavior is identical to what has been observed with other proteinic systems. In the lower plateau domain, in contrast, the protein release process is independent of the concentration of proteins in the bulk, but the release rates are higher than the pure desorption rates. This constitutes, to our knowledge, a behavior that never before has been observed and that remains to be explained.

Quantitative relationship between adsorbed amount of solute and solvent composition

International Nuclear Information System (INIS)

Wang Yan; Geng Xindu; Zebolsky, Don M.

2003-01-01

A new adsorption isotherm that relates the amount of solute adsorbed to the solvent concentration is proposed. The new equation is derived from Geng and Shi's stoichiometric displacement model for adsorption (SDM-A). The obtained equation may be simplified to an expression containing two parameters. The equation with two parameters, valid for low concentrations of solute, is a logarithmically linear relationship. The intercept contains a thermodynamic equilibrium constant of the solute displacing solvent from the adsorbent. The slope is the negative value of the stoichiometric displacement parameter (Z), the average total number of solvent molecules displaced from an active site on the adsorbent and from the solute. Tests with a homologous series of aromatic alcohols by frontal analysis in reversed phase liquid chromatography demonstrate that experimental results fit the equation well

Controlled contact to a C-60 molecule

DEFF Research Database (Denmark)

Neel, N.; Kröger, J.; Limot, L.

2007-01-01

The tip of a low-temperature scanning tunneling microscope is approached towards a C-60 molecule adsorbed at a pentagon-hexagon bond on Cu(100) to form a tip-molecule contact. The conductance rapidly increases to approximate to 0.25 conductance quanta in the transition region from tunneling to co...

Carbon and hydrogen isotopic composition of methane and C2+ alkanes in electrical spark discharge: implications for identifying sources of hydrocarbons in terrestrial and extraterrestrial settings.

Science.gov (United States)

Telling, Jon; Lacrampe-Couloume, Georges; Sherwood Lollar, Barbara

2013-05-01

The low-molecular-weight alkanes--methane, ethane, propane, and butane--are found in a wide range of terrestrial and extraterrestrial settings. The development of robust criteria for distinguishing abiogenic from biogenic alkanes is essential for current investigations of Mars' atmosphere and for future exobiology missions to other planets and moons. Here, we show that alkanes synthesized during gas-phase radical recombination reactions in electrical discharge experiments have values of δ(2)H(methane)>δ(2)H(ethane)>δ(2)H(propane), similar to those of the carbon isotopes. The distribution of hydrogen isotopes in gas-phase radical reactions is likely due to kinetic fractionations either (i) from the preferential incorporation of (1)H into longer-chain alkanes due to the more rapid rate of collisions of the smaller (1)H-containing molecules or (ii) by secondary ion effects. Similar δ(13)C(C1-C2+) and δ(2)H(C1-C2+) patterns may be expected in a range of extraterrestrial environments where gas-phase radical reactions dominate, including interstellar space, the atmosphere and liquid hydrocarbon lakes of Saturn's moon Titan, and the outer atmospheres of Jupiter, Saturn, Neptune, and Uranus. Radical recombination reactions at high temperatures and pressures may provide an explanation for the combined reversed δ(13)C(C1-C2+) and δ(2)H(C1-C2+) patterns of terrestrial alkanes documented at a number of high-temperature/pressure crustal sites.

Photochemical dynamics of surface oriented molecules

International Nuclear Information System (INIS)

Ho, W.

1992-01-01

The period 8/01/91-7/31/92 is the first year of a new project titled ''Photochemical Dynamics of Surface Oriented Molecules'', initiated with DOE Support. The main objective of this project is to understand the dynamics of elementary chemical reactions by studying photochemical dynamics of surface-oriented molecules. In addition, the mechanisms of photon-surface interactions need to be elucidated. The strategy is to carry out experiments to measure the translational energy distribution, as a function of the angle from the surface normal, of the photoproducts by time-of-flight (TOF) technique by varying the photon wavelength, intensity, polarization, and pulse duration. By choosing adsorbates with different bonding configuration, the effects of adsorbate orientation on surface photochemical dynamics can be studied

Interaction of atomic hydrogen with ethylene adsorbed on nickel films

International Nuclear Information System (INIS)

Korchak, V.N.; Tret'yakov, I.I.; Kislyuk, M.U.

1976-01-01

The reactivity of ethylene adsorbed on the pure films of nickel at various temperatures was studied with respect to hydrogen atoms generated in the gaseous phase. The experiments were conducted in a glass vacuum apparatus enabling one to obtain the highest vacuum up to 2x20 -10 torr. The catalyst, nickel films, was produced by their deposition onto the walls of the glass reactor at a pressure of the residual gas of 10 -9 torr and a temperature of the walls of 25 deg C. Gas purity was analyzed by the mass spectrometric method. The ethylene adsorbed at the temperatures below 173 deg K reacted readily with the hydrogen atoms to yield ethane. The process ran without practically any activation energy involved and was limited by the attachment of the first hydrogen atom to the ethylene molecule. The efficiency of this interaction was 0.02 of the number of the hydrogen atoms collisions against the surface occupied by the ethylene. The adsorption of the ethylene at room and higher temperatures was accompanied by its disproportioning with the release of the hydrogen into the gaseous phase and a serious destruction of the ethylene molecules adsorbed to produce hydrogen residues interacting with neither molecular nor atomic hydrogen [ru

Graphene symmetry-breaking with molecular adsorbates: modeling and experiment

Science.gov (United States)

Groce, M. A.; Hawkins, M. K.; Wang, Y. L.; Cullen, W. G.; Einstein, T. L.

2012-02-01

Graphene's structure and electronic properties provide a framework for understanding molecule-substrate interactions and developing techniques for band gap engineering. Controlled deposition of molecular adsorbates can create superlattices which break the degeneracy of graphene's two-atom unit cell, opening a band gap. We simulate scanning tunneling microscopy and spectroscopy measurements for a variety of organic molecule/graphene systems, including pyridine, trimesic acid, and isonicotinic acid, based on density functional theory calculations using VASP. We also compare our simulations to ultra-high vacuum STM and STS results.

Determination Of Adsorption And Paraffin Characterization Of Treatment To Adsorb Vegetable Oil

International Nuclear Information System (INIS)

Aminah, Neneng Siti; Mulijani, Sri; Sudirman; Ridwan

2004-01-01

Using vegetable oil repeatedly, beside affect on quality decline of food and the oil itself, it is harmful to human health. Some poisoning and carcinogenic symptom were founded with experiment using animals. According to that fact, the aim of the research is using paraffin and candle to adsorb used vegetable oil and to convert into solid sample, so it can be easily wasted. At first, 2 g of sample was poured into the heated oil, with gently stirrer until it turned cold and harden. Each sample and standard before and after treatment was characterized with Ftir, XRD, and DSc. The result shows that paraffins adsorbs 40 ml used vegetable oil with 2 g sample in proportion. That proportion is lower than the standard which can adsorb 66.67 ml vegetable oil in the same weight sample. The difference of paraffin and standard is caused by physical properties within that two materials, and it can be explained by Ftir, X-Ray Diffraction (XRD) and differential scanning calorimetry (DSc). Based on result of Ftir analysis, standard consented of saturated hydrocarbon compound (alkanes) whereas paraffin consisted of unsaturated hydrocarbon compound (alkenes). Infrared spectrum after treatment showed the changes of compound, O-H and esters group were formed and it shows characterised the adsorption process. The result of DSc analysis showed that crystalline the melting point of standard is 75,3 o C and paraffin is 54,17 o C. The result of analysis XRD, described that standard and paraffin before treatment are crystalline whereas after treatment are am orf

Atmospheric fate of oil matter adsorbed on sea salt particles under UV light

Science.gov (United States)

Vaitilingom, M.; Avij, P.; Huang, H.; Valsaraj, K. T.

2014-12-01

The presence of liquid petroleum hydrocarbons at the sea water surface is an important source of marine pollution. An oil spill in sea-water will most likely occur due to an involuntary accident from tankers, offshore platforms, etc. However, a large amount of oil is also deliberately spilled in sea-water during the clean-out process of tank vessels (e.g. for the Mediterranean Sea, 490,000 tons/yr). Moreover, the pollution caused by an oil spill does not only affect the aquatic environment but also is of concern for the atmospheric environment. A portion of the oil matter present at the sea-water surface is transported into the atmosphere viaevaporation and adsorption at the surface of sea spray particles. Few studies are related to the presence of oil matter in airborne particles resulting from their adsorption on sea salt aerosols. We observed that the non-volatile oil matter was adsorbed at the surface of sea-salt crystals (av. size of 1.1 μm). Due to their small size, these particles can have a significant residence time in the atmosphere. The hydrocarbon matter adsorbed at the surface of these particles can also be transformed by catalyzers present in the atmosphere (i.e. UV, OH, O3, ...). In this work, we focused on the photo-oxidation rates of the C16 to C30alkanes present in these particles. We utilized a bubble column reactor, which produced an abundance of small sized bubbles. These bubbles generated droplets upon bursting at the air-salt water interface. These droplets were then further dried up and lifted to the top of the column where they were collected as particles. These particles were incubated in a controlled reactor in either dark conditions or under UV-visible light. The difference of alkane content analyzed by GC-MS between the particles exposed to UV or the particles not exposed to UV indicated that up to 20% in mass was lost after 20 min of light exposure. The degradation kinetics varied for each range of alkanes (C16-20, C21-25, C26

Zeolites as alcohol adsorbents from aqueous solutions

Directory of Open Access Journals (Sweden)

Cekova Blagica

2006-01-01

Full Text Available The potential usage of zeolites as adsorbents for the removal of organic molecules from water was investigated in a series of experiments with aqueous solutions of lower alcohols. This could represent a simple solution to the problem of cleaning up industrial wastewater as well as recovering valuable chemicals at relatively low costs. Adsorption isotherms of the Langmuir type were applied, and calculations showed that the amount of propanol adsorbed on silicalite corresponded to approximately 70% of the pore volume. The adsorption process is simple, and recovery of the more concentrated products is easily done by heat treatment and/or at lowered pressures. Adsorption experiments with aqueous acetone showed that silicalite had approximately the same adsorption capacity for acetone as for n-propanol. Heats of adsorption were determined calorimetrically.

Fundamental Flame Velocities of Pure Hydrocarbons I : Alkanes, Alkenes, Alkynes Benzene, and Cyclohexane

Science.gov (United States)

Gerstein, Melvin; Levine, Oscar; Wong, Edgar L

1950-01-01

The flame velocities of 37 pure hydrocarbons including normal and branched alkanes, alkenes, and alkynes; as well as benzene and cyclohexane, together with the experimental technique employed are presented. The normal alkanes have about the same flame velocity from ethane through heptane with methane being about 16 percent lower. Unsaturation increases the flame velocity in the order of alkanes, alkenes, and alkynes. Branching reduces the flame velocity.

Black molecular adsorber coatings for spaceflight applications

Science.gov (United States)

Abraham, Nithin S.; Hasegawa, Mark M.; Straka, Sharon A.

2014-09-01

The molecular adsorber coating is a new technology that was developed to mitigate the risk of on-orbit molecular contamination on spaceflight missions. The application of this coating would be ideal near highly sensitive, interior surfaces and instruments that are negatively impacted by outgassed molecules from materials, such as plastics, adhesives, lubricants, epoxies, and other similar compounds. This current, sprayable paint technology is comprised of inorganic white materials made from highly porous zeolite. In addition to good adhesion performance, thermal stability, and adsorptive capability, the molecular adsorber coating offers favorable thermal control characteristics. However, low reflectivity properties, which are typically offered by black thermal control coatings, are desired for some spaceflight applications. For example, black coatings are used on interior surfaces, in particular, on instrument baffles for optical stray light control. Similarly, they are also used within light paths between optical systems, such as telescopes, to absorb light. Recent efforts have been made to transform the white molecular adsorber coating into a black coating with similar adsorptive properties. This result is achieved by optimizing the current formulation with black pigments, while still maintaining its adsorption capability for outgassing control. Different binder to pigment ratios, coating thicknesses, and spray application techniques were explored to develop a black version of the molecular adsorber coating. During the development process, coating performance and adsorption characteristics were studied. The preliminary work performed on black molecular adsorber coatings thus far is very promising. Continued development and testing is necessary for its use on future contamination sensitive spaceflight missions.

The interaction of linear and ring forms of DNA molecules with nanodiamonds synthesized by detonation

International Nuclear Information System (INIS)

Purtov, K V; Burakova, L P; Puzyr, A P; Bondar, V S

2008-01-01

Nanodiamonds synthesized by detonation have been found not to immobilize the ring form of pUC19 plasmid DNA. Linear pUC19 molecules with blunt ends, prepared by restriction of the initial ring form of pUC19 DNA, and linear 0.25-10 kb DNA fragments are adsorbed on nanodiamonds. The amount of adsorbed linear DNA molecules depends on the size of the molecules and the size of the nanodiamond clusters

Selective conversion of butane into liquid hydrocarbon fuels on alkane metathesis catalysts

KAUST Repository

Szeto, Kaï Chung; Hardou, Lucie; Merle, Nicolas; Basset, Jean-Marie; Thivolle-Cazat, Jean; Papaioannou, Charalambos; Taoufik, Mostafa

2012-01-01

We report a selective direct conversion of n-butane into higher molecular weight alkanes (C 5+) by alkane metathesis reaction catalysed by silica-alumina supported tungsten or tantalum hydrides at moderate temperature and pressure. The product

Bicarbonate Elution of Uranium from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

Energy Technology Data Exchange (ETDEWEB)

Pan, Horng-Bin [Department of Chemistry, University of Idaho, Moscow, Idaho 83844 USA; Wai, Chien M. [Department of Chemistry, University of Idaho, Moscow, Idaho 83844 USA; Kuo, Li-Jung [Pacific Northwest National Laboratory, Marine Sciences Laboratory, Sequim, Washington 98382 USA; Gill, Gary [Pacific Northwest National Laboratory, Marine Sciences Laboratory, Sequim, Washington 98382 USA; Tian, Guoxin [Lawrence Berkeley National Laboratory, Berkeley, California 94720 USA; Rao, Linfeng [Lawrence Berkeley National Laboratory, Berkeley, California 94720 USA; Das, Sadananda [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 USA; Mayes, Richard T. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 USA; Janke, Christopher J. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 USA

2017-05-02

Uranium adsorbed on amidoxime-based polyethylene fibers in simulated seawater can be quantitatively eluted using 3 M KHCO3 at 40°C. Thermodynamic calculations are in agreement with the experimental observation that at high bicarbonate concentrations (3 M) uranyl ions bound to amidoxime molecules are converted to uranyl tris-carbonato complex in the aqueous solution. The elution process is basically the reverse reaction of the uranium adsorption process which occurs at a very low bicarbonate concentration (~10-3 M) in seawater. In real seawater experiments, the bicarbonate elution is followed by a NaOH treatment to remove natural organic matter adsorbed on the polymer adsorbent. Using the sequential bicarbonate and NaOH elution, the adsorbent is reusable after rinsing with deionized water and the recycled adsorbent shows no loss of uranium loading capacity based on real seawater experiments.

Optimization of linear and branched alkane interactions with water to simulate hydrophobic hydration

Science.gov (United States)

Ashbaugh, Henry S.; Liu, Lixin; Surampudi, Lalitanand N.

2011-08-01

Previous studies of simple gas hydration have demonstrated that the accuracy of molecular simulations at capturing the thermodynamic signatures of hydrophobic hydration is linked both to the fidelity of the water model at replicating the experimental liquid density at ambient pressure and an accounting of polarization interactions between the solute and water. We extend those studies to examine alkane hydration using the transferable potentials for phase equilibria united-atom model for linear and branched alkanes, developed to reproduce alkane phase behavior, and the TIP4P/2005 model for water, which provides one of the best descriptions of liquid water for the available fixed-point charge models. Alkane site/water oxygen Lennard-Jones cross interactions were optimized to reproduce the experimental alkane hydration free energies over a range of temperatures. The optimized model reproduces the hydration free energies of the fitted alkanes with a root mean square difference between simulation and experiment of 0.06 kcal/mol over a wide temperature range, compared to 0.44 kcal/mol for the parent model. The optimized model accurately reproduces the temperature dependence of hydrophobic hydration, as characterized by the hydration enthalpies, entropies, and heat capacities, as well as the pressure response, as characterized by partial molar volumes.

The state of physically adsorbed substances in microporous adsorbents

International Nuclear Information System (INIS)

Fomkin, A.A.

1987-01-01

Xe, Kr, Ar, CF 3 Cl, CH 4 adsorption in NaX microporous zeolite of 0.98 Na 2 OxAl 2 O 3 x2.36SiO 2 x0.02H 2 O is studied. Some properties of adsorbates (density, coefficients of expansion, enthalpy, heat capacity) are determined and discussed. The adsorbate in the microporous adsorbent is shown to be a particular state of a substance. Liniarity of adsorption isosteres and sharp changes during isosteric heat capacity of the adsorbate points to the fact that in microporous adsorbents phase transformations of the second type are possible

The effect of n-alkane selection depth on the quality of denormalizate

Energy Technology Data Exchange (ETDEWEB)

Dorodnova, V.S.; Bayburskaya, E.L.; Martynenko, A.G.

1982-01-01

The effect of n-alkane selection depth from crude diesel fuel on the quality of denormalization on a carbamide deparaffination G-64 device at the Gorknefteorgsintez Production Association. Diesel fuel with o.c. 210/sup 0/, c.c. 315/sup 0/, 828 kg/m/sup 3/ density, -25, n/sup 20/ D 1.4620, aniline point 66.9/sup 0/ and n-alkane content 14.7% was used. The regime of the stage of complex formation was maximal approximation of industrial conditions: ratio Cr: ben. 1:2.6 mass. no, complex formation 25/sup 0/, length of contact 30 min, levels of washing, 2; methanol, 2.0% in Cr. Changing the quantity of carbamide aided the various extraction depths of n-alkanes from the Cr. Following distillation of the solution the following parameters were examined: refraction, density, aniline point, diesel index; Obtained: the dependencies for changes in these indicators depending on the depth of the selection of n-alkanes from the potential or from their content in the denormalizate; as well as the dependence of the component composition of paraffins on the degree of their extraction from the Cr. To simultaneously obtain paraffins and diesel fuel of export quality with a diesel index no lower than 55, it is necessary to guarantee up to 50% (no higher) of paraffin selection from the potential Cr containing 14.7% n-alkanes; the sediment content of n-alkanes in the denormalizate must be found at the 7.4% level.

Alkanes as Components of Soil Hydrocarbon Status: Behavior and Indication Significance

Science.gov (United States)

Gennadiev, A. N.; Zavgorodnyaya, Yu. A.; Pikovskii, Yu. I.; Smirnova, M. A.

2018-01-01

Studies of soils on three key plots with different climatic conditions and technogenic impacts in Volgograd, Moscow, and Arkhangelsk oblasts have showed that alkanes in the soil exchange complex have some indication potential for the identification of soil processes. The following combinations of soil-forming factors and processes have been studied: (a) self-purification of soil after oil pollution; (b) accumulation of hydrocarbons coming from the atmosphere to soils of different land use patterns; and (c) changes in the soil hydrocarbon complex beyond the zone of technogenic impact due to the input of free hydrocarbon-containing gases. At the injection input of hydrocarbon pollutants, changes in the composition and proportions of alkanes allow tracing the degradation trend of pollutants in the soil from their initial content to the final stage of soil self-purification, when the background concentrations of hydrocarbons are reached. Upon atmospheric deposition of hydrocarbons onto the soil, from the composition and mass distribution of alkanes, conclusions can be drawn about the effect of toxicants on biogeochemical processes in the soil, including their manifestation under different land uses. Composition analysis of soil alkanes in natural landscapes can reveal signs of hydrocarbon emanation fluxes in soils. The indication potentials of alkanes in combination with polycyclic aromatic hydrocarbons and other components of soil hydrocarbon complex can also be used for the solution of other soil-geochemical problems.

Magnetic susceptibility of oxygen adsorbed on the surface of spherical and fibrous activated carbon.

Directory of Open Access Journals (Sweden)

Kiyoshi Kawamura

2009-02-01

Full Text Available The magnetic susceptibilities of oxygen adsorbed on the surface of bead-shaped activated carbon and activated carbon fibers were evaluated as a function of temperature between 4.2 K and 300 K, and found to exhibit a sharp peak at around 50 K. This implies that the adsorbed oxygen molecules form an antiferromagnetic state. The relation between the susceptibility and the adsorbed mass suggest that the thickness of the adsorbed oxygen is thin enough to consider a two-dimensional structure for bead–shaped activated carbon and carbon fibers across the fiber axis but thick enough to regard it as three-dimensional along the fiber axis. The result is discussed with reference to the study on one-dimensional oxygen array.

Alkane dimers interaction

DEFF Research Database (Denmark)

Ferrighi, Lara; Madsen, Georg Kent Hellerup; Hammer, Bjørk

2010-01-01

The interaction energies of a series of n-alkane dimers, from methane to decane, have been investigated with Density Functional Theory (DFT), using the MGGA-M06-L density functional. The results are compared both to the available wavefunction-based values as well as to dispersion corrected DFT...... values. The MGGA-M06-L density functional is a semi-local functional designed and has proven to provide accurate estimates of dispersion interactions for several systems at moderate computational cost. In the present application, it reproduces the trends obtained by the more expensive wavefunction...

Abundance of macroalgal organic matter in biofilms: Evidence from n-alkane biomarkers

Digital Repository Service at National Institute of Oceanography (India)

Garg, A; Bhosle, N.B.

carbon (OC), organic nitrogen (ON), chlorophyll a, diatoms and bacterial numbers on the titanium panels generally increased over the period of immersion. Total lipids and n-alkane concentration also showed similar trends. n-alkanes from C sub(12) to C sub...

Optimization of the elaboration conditions of an adsorber for the hydrogen storage; Optimisation des conditions d'elaboration d'un adsorbant pour le stockage d'hydrogene

Energy Technology Data Exchange (ETDEWEB)

Fierro, V.; Mareche, J.F.; Furdin, G. [Nancy-1 Univ. Henri Poincare, UMR - CNRS 7555, Laboratoire de Chimie du Solide Mineral, 54 - Vandoeuvre-les-Nancy (France); Szczurek, A.; Albiniak, A. [Wroclaw Univ. of Technology, Laboratory for Lignites and Carbon Adsorbents, Institute of Chemistry and Technology of Petroleum and Coal (Poland); Latroche, M. [Chimie Metallurgique des Terres Rares, ICMPE, UMR 7182, CNRS, 94 - Thiais (France); Celzard, A. [Nancy-Univ., ENSTIB, Laboratoire de Chimie du Solide Mineral, UMR CNRS 7555, 88 - Epinal (France)

2008-07-01

The microporous carbon are very efficient adsorbents for the hydrogen storage, because of pores size under 2 nm. This study describes the optimization of the elaboration conditions for a carbon adsorbent for the hydrogen storage by adsorption. The storage capacity has been measured at 25 C for 20 MPa and also at 77 K for pressures between 6 and 9 MPa. the porous texture characterization has been realized by four molecule probes of increasing diameter: CO{sub 2}, N{sub 2}, C{sub 6}H{sub 6} and CCl{sub 4}. (A.L.B.)

Comparing the accuracy of high-dimensional neural network potentials and the systematic molecular fragmentation method: A benchmark study for all-trans alkanes

Energy Technology Data Exchange (ETDEWEB)

Gastegger, Michael; Kauffmann, Clemens; Marquetand, Philipp, E-mail: philipp.marquetand@univie.ac.at [Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, Vienna (Austria); Behler, Jörg [Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, Universitätsstraße 150, Bochum (Germany)

2016-05-21

Many approaches, which have been developed to express the potential energy of large systems, exploit the locality of the atomic interactions. A prominent example is the fragmentation methods in which the quantum chemical calculations are carried out for overlapping small fragments of a given molecule that are then combined in a second step to yield the system’s total energy. Here we compare the accuracy of the systematic molecular fragmentation approach with the performance of high-dimensional neural network (HDNN) potentials introduced by Behler and Parrinello. HDNN potentials are similar in spirit to the fragmentation approach in that the total energy is constructed as a sum of environment-dependent atomic energies, which are derived indirectly from electronic structure calculations. As a benchmark set, we use all-trans alkanes containing up to eleven carbon atoms at the coupled cluster level of theory. These molecules have been chosen because they allow to extrapolate reliable reference energies for very long chains, enabling an assessment of the energies obtained by both methods for alkanes including up to 10 000 carbon atoms. We find that both methods predict high-quality energies with the HDNN potentials yielding smaller errors with respect to the coupled cluster reference.

Comparing the accuracy of high-dimensional neural network potentials and the systematic molecular fragmentation method: A benchmark study for all-trans alkanes

International Nuclear Information System (INIS)

Gastegger, Michael; Kauffmann, Clemens; Marquetand, Philipp; Behler, Jörg

2016-01-01

Many approaches, which have been developed to express the potential energy of large systems, exploit the locality of the atomic interactions. A prominent example is the fragmentation methods in which the quantum chemical calculations are carried out for overlapping small fragments of a given molecule that are then combined in a second step to yield the system’s total energy. Here we compare the accuracy of the systematic molecular fragmentation approach with the performance of high-dimensional neural network (HDNN) potentials introduced by Behler and Parrinello. HDNN potentials are similar in spirit to the fragmentation approach in that the total energy is constructed as a sum of environment-dependent atomic energies, which are derived indirectly from electronic structure calculations. As a benchmark set, we use all-trans alkanes containing up to eleven carbon atoms at the coupled cluster level of theory. These molecules have been chosen because they allow to extrapolate reliable reference energies for very long chains, enabling an assessment of the energies obtained by both methods for alkanes including up to 10 000 carbon atoms. We find that both methods predict high-quality energies with the HDNN potentials yielding smaller errors with respect to the coupled cluster reference.

Crystal structures of eight mono-methyl alkanes (C26–C32 via single-crystal and powder diffraction and DFT-D optimization

Directory of Open Access Journals (Sweden)

Lee Brooks

2015-09-01

Full Text Available The crystal structures of eight mono-methyl alkanes have been determined from single-crystal or high-resolution powder X-ray diffraction using synchrotron radiation. Mono-methyl alkanes can be found on the cuticles of insects and are believed to act as recognition pheromones in some social species, e.g. ants, wasps etc. The molecules were synthesized as pure S enantiomers and are (S-9-methylpentacosane, C26H54; (S-9-methylheptacosane and (S-11-methylheptacosane, C28H58; (S-7-methylnonacosane, (S-9-methylnonacosane, (S-11-methylnonacosane and (S-13-methylnonacosane, C30H62; and (S-9-methylhentriacontane, C32H66. All crystallize in space group P21. Depending on the position of the methyl group on the carbon chain, two packing schemes are observed, in which the molecules pack together hexagonally as linear rods with terminal and side methyl groups clustering to form distinct motifs. Carbon-chain torsion angles deviate by less than 10° from the fully extended conformation, but with one packing form showing greater curvature than the other near the position of the methyl side group. The crystal structures are optimized by dispersion-corrected DFT calculations, because of the difficulties in refining accurate structural parameters from powder diffraction data from relatively poorly crystalline materials.

Heat transfer between adsorbate and laser-heated hot electrons

International Nuclear Information System (INIS)

Ueba, H; Persson, B N J

2008-01-01

Strong short laser pulses can give rise to a strong increase in the electronic temperature at metal surfaces. Energy transfer from the hot electrons to adsorbed molecules may result in adsorbate reactions, e.g. desorption or diffusion. We point out the limitations of an often used equation to describe the heat transfer process in terms of a friction coupling. We propose a simple theory for the energy transfer between the adsorbate and hot electrons using a newly introduced heat transfer coefficient, which depends on the adsorbate temperature. We calculate the transient adsorbate temperature and the reaction yield for a Morse potential as a function of the laser fluency. The results are compared to those obtained using a conventional heat transfer equation with temperature-independent friction. It is found that our equation of energy (heat) transfer gives a significantly lower adsorbate peak temperature, which results in a large modification of the reaction yield. We also consider the heat transfer between different vibrational modes excited by hot electrons. This mode coupling provides indirect heating of the vibrational temperature in addition to the direct heating by hot electrons. The formula of heat transfer through linear mode-mode coupling of two harmonic oscillators is applied to the recent time-resolved study of carbon monoxide and atomic oxygen hopping on an ultrafast laser-heated Pt(111) surface. It is found that the maximum temperature of the frustrated translation mode can reach high temperatures for hopping, even when direct friction coupling to the hot electrons is not strong enough

Hydrogen Bonding to Alkanes: Computational Evidence

DEFF Research Database (Denmark)

Hammerum, Steen; Olesen, Solveig Gaarn

2009-01-01

The structural, vibrational, and energetic properties of adducts of alkanes and strong cationic proton donors were studied with composite ab initio calculations. Hydrogen bonding in [D-H+ H-alkyl] adducts contributes to a significant degree to the interactions between the two components, which is...

Core Level Spectra of Organic Molecules Adsorbed on Graphene

Directory of Open Access Journals (Sweden)

Abhilash Ravikumar

2018-03-01

Full Text Available We perform first principle calculations based on density functional theory to investigate the effect of the adsorption of core-excited organic molecules on graphene. We simulate Near Edge X-ray absorption Fine Structure (NEXAFS and X-ray Photoemission Spectroscopy (XPS at the N and C edges for two moieties: pyridine and the pyridine radical on graphene, which exemplify two different adsorption characters. The modifications of molecular and graphene energy levels due to their interplay with the core-level excitation are discussed. We find that upon physisorption of pyridine, the binding energies of graphene close to the adsorption site reduce mildly, and the NEXAFS spectra of the molecule and graphene resemble those of gas phase pyridine and pristine graphene, respectively. However, the chemisorption of the pyridine radical is found to significantly alter these core excited spectra. The C 1s binding energy of the C atom of graphene participating in chemisorption increases by ∼1 eV, and the C atoms of graphene alternate to the adsorption site show a reduction in the binding energy. Analogously, these C atoms also show strong modifications in the NEXAFS spectra. The NEXAFS spectrum of the chemisorbed molecule is also modified as a result of hybridization with and screening by graphene. We eventually explore the electronic properties and magnetism of the system as a core-level excitation is adiabatically switched on.

The synthesis of a new type adsorbent for the removal of toxic gas by radiation-induced graft polymerization

International Nuclear Information System (INIS)

Okamoto, Jiro; Sugo, Takanobu

1990-01-01

A new type of adsorbent containing sulfuric acid group for the removal of ammonia gas was synthesized by radiation-induced graft polymerization of styrene onto fibrous and nonwoven type polypropylene followed by sulufonation with chlorosulfonic acid. The rate of the adsorption of ammonia gas by H-type adsorbent is independent of the ion-exchange capacity. The amount of ammonia gas adsorbed by the chemical adsorption was dependent on the ion-exchange capacity of H-type fibrous adsorbent and was kept constant value in spite of the equilibrium pressure of ammonia gas. Cu(II)- and Ni(II)-types fibrous adsorbent were prepared by the ion exchange reaction of Na-type fibrous adsorbent with metal nitrate solutions. Although, the rate of adsorption of ammonia gas by metal-type fibrous adsorbent is lower than that of H-type adsorbent, the amount of ammonia gas adsorbed increases compared to H-type adsorbent with the same ion exchange capacity. It was related to the highest coordination number of metal ion. The ratio of the number of ammonia molecules adsorbed chemically and the number of metal ion adsorbed in fibrous adsorbent was 4 for Cu-type and 6 for Ni-type fibrous adsorbent, respectively. (author)

Regioselective alkane hydroxylation with a mutant AlkB enzyme

Science.gov (United States)

Koch, Daniel J.; Arnold, Frances H.

2012-11-13

AlkB from Pseudomonas putida was engineered using in-vivo directed evolution to hydroxylate small chain alkanes. Mutant AlkB-BMO1 hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. Mutant AlkB-BMO2 similarly hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. These biocatalysts are highly active for small chain alkane substrates and their regioselectivity is retained in whole-cell biotransformations.

The quantitative significance of Syntrophaceae and syntrophic partnerships in methanogenic degradation of crude oil alkanes.

Science.gov (United States)

Gray, N D; Sherry, A; Grant, R J; Rowan, A K; Hubert, C R J; Callbeck, C M; Aitken, C M; Jones, D M; Adams, J J; Larter, S R; Head, I M

2011-11-01

Libraries of 16S rRNA genes cloned from methanogenic oil degrading microcosms amended with North Sea crude oil and inoculated with estuarine sediment indicated that bacteria from the genera Smithella (Deltaproteobacteria, Syntrophaceace) and Marinobacter sp. (Gammaproteobacteria) were enriched during degradation. Growth yields and doubling times (36 days for both Smithella and Marinobacter) were determined using qPCR and quantitative data on alkanes, which were the predominant hydrocarbons degraded. The growth yield of the Smithella sp. [0.020 g(cell-C)/g(alkane-C)], assuming it utilized all alkanes removed was consistent with yields of bacteria that degrade hydrocarbons and other organic compounds in methanogenic consortia. Over 450 days of incubation predominance and exponential growth of Smithella was coincident with alkane removal and exponential accumulation of methane. This growth is consistent with Smithella's occurrence in near surface anoxic hydrocarbon degrading systems and their complete oxidation of crude oil alkanes to acetate and/or hydrogen in syntrophic partnership with methanogens in such systems. The calculated growth yield of the Marinobacter sp., assuming it grew on alkanes, was [0.0005 g(cell-C)/g(alkane-C)] suggesting that it played a minor role in alkane degradation. The dominant methanogens were hydrogenotrophs (Methanocalculus spp. from the Methanomicrobiales). Enrichment of hydrogen-oxidizing methanogens relative to acetoclastic methanogens was consistent with syntrophic acetate oxidation measured in methanogenic crude oil degrading enrichment cultures. qPCR of the Methanomicrobiales indicated growth characteristics consistent with measured rates of methane production and growth in partnership with Smithella. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

Imaging and manipulation of a polar molecule on Ag(111)

DEFF Research Database (Denmark)

Lin, R.; Braun, K.F.; Tang, H.

2001-01-01

A scanning tunneling microscope (STM) was applied to image and laterally manipulate isolated phosphangulene molecules on Ag(111) at 6 K. Atomic-resolution images clearly revealed three characteristic types of appearances (three-lobed, fish and bump shape) for the adsorbed molecules, which could...

Application of a Crossover Equation of State to Describe Phase Equilibrium and Critical Properties of n-Alkanes and Methane/n-Alkane Mixtures

DEFF Research Database (Denmark)

P. C. M. Vinhal, Andre; Yan, Wei; Kontogeorgis, Georgios M.

2018-01-01

and the asymptotic one near the critical point. Although several crossover EOSs have been developed in the last decades their use in modeling industrial processes is rather limited. In this work, we use the crossover Soave–Redlich–Kwong (CSRK) to describe phase equilibrium and critical properties of pure n......-alkanes and methane/n-alkane binary mixtures and compare the results to two other modeling approaches of the SRK EOS. In the case of the pure fluids, CSRK gives an accurate overall description of the phase equilibrium and critical properties; nevertheless, a minor increase in the deviation of the saturation pressure...

Observing single molecule chemical reactions on metal nanoparticles.

Energy Technology Data Exchange (ETDEWEB)

Emory, S. R. (Steven R.); Ambrose, W. Patrick; Goodwin, P. M. (Peter M); Keller, Richard A.

2001-01-01

We report the study of the photodecomposition of single Rhodamine 6G (R6G) dye molecules adsorbed on silver nanoparticles. The nanoparticles were immobilized and spatially isolated on polylysine-derivatized glass coverslips, and confocal laser microspectroscopy was used to obtain surface-enhanced Raman scattering (SERS) spectra from individual R6G molecules. The photodecomposition of these molecules was observed with 150-ms temporal resolution. The photoproduct was identified as graphitic carbon based on the appearance of broad SERS vibrational bands at 1592 cm{sup -1} and 1340 cm{sup -1} observed in both bulk and averaged single-molecule photoproduct spectra. In contrast, when observed at the single-molecule level, the photoproduct yielded sharp SERS spectra. The inhomogeneous broadening of the bulk SERS spectra is due to a variety of photoproducts in different surface orientations and is a characteristic of ensemble-averaged measurements of disordered systems. These single-molecule studies indicate a photodecomposition pathway by which the R6G molecule desorbs from the metal surface, an excited-state photoreaction occurs, and the R6G photoproduct(s) readsorbs to the surface. A SERS spectrum is obtained when either the intact R6G or the R6G photoproduct(s) are adsorbed on a SERS-active site. This work further illustrates the power of single-molecule spectroscopy (SMS) to reveal unique behaviors of single molecules that are not discernable with bulk measurements.

The fate of primary cations in radiolysis of alkanes as studied by ESR

International Nuclear Information System (INIS)

Iwasaki, M.; Toriyama, K.; Nunome, K.

1983-01-01

The structures and reactions of alkane cations (RH + ) have been studied by ESR to elucidate the fate of primary cations in radiolysis of alkanes. Radical cations of prototype alkanes such as C 2 H 6 , C 3 H 8 , iso-C 4 H 10 and neo-C 5 H 12 etc. as well as their partially deuterated analogues were stabilized in irradiated frozen matrices such as SF 6 , CFCl 2 CF 2 Cl and CFCl 3 having a higher ionization potential than that of these alkanes contained as dilute solutes. RH + in SF 6 and in CFCl 2 CF 2 Cl converts into alkyl radicals by deprotonation probably through bimolecular reactions, whereas RH + in CFCl 3 unimolecularily decomposes into olefinic cations by H 2 and/or CH 4 elimination reactions. It is further found that the electronic structures of propane and isobutane cations in halocarbon matrices are different from those in SF 6 and the difference is drastically reflected in the site preference of their deprotonation reactions. The results are discussed in relation to the mechanisms of pairwise formation of alkyl radicals in low temperature radiolysis of neat alkanes and its suppression by addition of electron scavengers. (author)

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

Science.gov (United States)

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

2013-01-25

The role of the structure of three isoreticular metal-organic frameworks (IRMOFs) on their adsorption behavior has been studied in this work, selecting different kinds of volatile organic compounds (VOCs) as adsorbates (alkanes, alkenes, cycloalkanes, aromatics and chlorinated). For this purpose, three samples (IRMOF-1, IRMOF-8 and IRMOF-10) with cubic structure and without functionalities on the organic linkers were synthesized. Adsorption capacities at infinite dilution were derived from the adsorption isotherms, whereas thermodynamic properties have been determined from chromatographic retention volume. The capacity and the strength of adsorption were strongly influenced by the adsorbate size. This effect is especially relevant for n-alkanes adsorption, indicating the key role of the cavity size on this phenomenon, and hence the importance of the IRMOF structural properties. A different behavior has been observed for the polar compounds, where an enhancement on the specificity of the adsorption with the π-electron rich regions was observed. This fact suggests the specific interaction of these molecules with the organic linkers of the IRMOFs. Copyright © 2012 Elsevier B.V. All rights reserved.

Packing properties 1-alkanols and alkanes in a phospholipid membrane

DEFF Research Database (Denmark)

Westh, Peter

2006-01-01

We have used vibrating tube densitometry to investigate the packing properties of four alkanes and a homologous series of ten alcohols in fluid-phase membranes of dimyristoyl phosphatidylcholine (DMPC). It was found that the volume change of transferring these compounds from their pure states int...... into the membrane core, which is loosely packed. In this region, they partially occupy interstitial (or free-) volume, which bring about a denser molecular packing and generate a negative contribution to Vm(puremem)....... into the membrane, Vm(puremem), was positive for small (C4-C6) 1-alkanols while it was negative for larger alcohols and all alkanes. The magnitude of Vm(puremem) ranged from about +4 cm3/mol for alcohols with an alkyl chain about half the length of the fatty acids of DMPC, to -10 to -15 cm3/mol for the alkanes...

Catalytic dehydroaromatization of n-alkanes by pincer-ligated iridium complexes

Science.gov (United States)

Ahuja, Ritu; Punji, Benudhar; Findlater, Michael; Supplee, Carolyn; Schinski, William; Brookhart, Maurice; Goldman, Alan S.

2011-02-01

Aromatic hydrocarbons are among the most important building blocks in the chemical industry. Benzene, toluene and xylenes are obtained from the high temperature thermolysis of alkanes. Higher alkylaromatics are generally derived from arene-olefin coupling, which gives branched products—that is, secondary alkyl arenes—with olefins higher than ethylene. The dehydrogenation of acyclic alkanes to give alkylaromatics can be achieved using heterogeneous catalysts at high temperatures, but with low yields and low selectivity. We present here the first catalytic conversion of n-alkanes to alkylaromatics using homogeneous or molecular catalysts—specifically ‘pincer’-ligated iridium complexes—and olefinic hydrogen acceptors. For example, the reaction of n-octane affords up to 86% yield of aromatic product, primarily o-xylene and secondarily ethylbenzene. In the case of n-decane and n-dodecane, the resulting alkylarenes are exclusively unbranched (that is, n-alkyl-substituted), with selectivity for the corresponding o-(n-alkyl)toluene.

The use of n-alkane markers to estimate the intake and apparent ...

African Journals Online (AJOL)

However, the effect of the higher recovery of the dosed marker needs further investigation. The estimates of apparent dry matter digestibility corresponded well with measured values, provided the factor for the incomplete faecal recovery of the internal alkanes was included in the calculation. It was concluded that the alkane ...

Distribution, activity and function of short-chain alkane degrading phylotypes in hydrothermal vent sediments

Science.gov (United States)

Adams, M. M.; Joye, S. B.; Hoarfrost, A.; Girguis, P. R.

2012-12-01

Global geochemical analyses suggest that C2-C4 short chain alkanes are a common component of the utilizable carbon pool in deep-sea sediments worldwide and have been found in diverse ecosystems. From a thermodynamic standpoint, the anaerobic microbial oxidation of these aliphatic hydrocarbons is more energetically yielding than the anaerobic oxidation of methane (AOM). Therefore, the preferential degradation of these hydrocarbons may compete with AOM for the use of oxidants such as sulfate, or other potential oxidants. Such processes could influence the fate of methane in the deep-sea. Sulfate-reducing bacteria (SRB) from hydrocarbon seep sediments of the Gulf of Mexico and Guaymas Basin have previously been enriched that anaerobically oxidize short chain alkanes to generate CO2 with the preferential utilization of 12C-enriched alkanes (Kniemeyer et al. 2007). Different temperature regimens along with multiple substrates were tested and a pure culture (deemed BuS5) was isolated from mesophilic enrichments with propane or n-butane as the sole carbon source. Through comparative sequence analysis, strain BuS5 was determined to cluster with the metabolically diverse Desulfosarcina / Desulfococcus cluster, which also contains the SRB found in consortia with anaerobic, methane-oxidizing archaea in seep sediments. Enrichments from a terrestrial, low temperature sulfidic hydrocarbon seep also corroborated that propane degradation occurred with most bacterial phylotypes surveyed belonging to the Deltaproteobacteria, particularly Desulfobacteraceae (Savage et al. 2011). To date, no microbes capable of ethane oxidation or anaerobic C2-C4 alkane oxidation at thermophilic temperature have been isolated. The sediment-covered, hydrothermal vent systems found at Middle Valley (Juan de Fuca Ridge, eastern Pacific Ocean) are a prime environment for investigating mesophilic to thermophilic anaerobic oxidation of short-chain alkanes, given the elevated temperatures and dissolved

Study of factors that influence complex-formation of n-alkanes with crystal carbamide

Energy Technology Data Exchange (ETDEWEB)

Dorodnova, V.S.; Korzhov, Yu.A.; Martynenko, A.G.

1982-01-01

Studies effect of temperature, solid phase content in the suspension and amount of MeOH on extent of n-alkane extraction during carbamide deparaffinization. A most thorough extraction of n-alkanes is achieved with a graduated temperature regimen of complex-formation.

Self-consistent molecular dynamics calculation of diffusion in higher n-alkanes.

Science.gov (United States)

Kondratyuk, Nikolay D; Norman, Genri E; Stegailov, Vladimir V

2016-11-28

Diffusion is one of the key subjects of molecular modeling and simulation studies. However, there is an unresolved lack of consistency between Einstein-Smoluchowski (E-S) and Green-Kubo (G-K) methods for diffusion coefficient calculations in systems of complex molecules. In this paper, we analyze this problem for the case of liquid n-triacontane. The non-conventional long-time tails of the velocity autocorrelation function (VACF) are found for this system. Temperature dependence of the VACF tail decay exponent is defined. The proper inclusion of the long-time tail contributions to the diffusion coefficient calculation results in the consistency between G-K and E-S methods. Having considered the major factors influencing the precision of the diffusion rate calculations in comparison with experimental data (system size effects and force field parameters), we point to hydrogen nuclear quantum effects as, presumably, the last obstacle to fully consistent n-alkane description.

Cool-flame Extinction During N-Alkane Droplet Combustion in Microgravity

Science.gov (United States)

Nayagam, Vedha; Dietrich, Daniel L.; Hicks, Michael C.; Williams, Forman A.

2014-01-01

Recent droplet combustion experiments onboard the International Space Station (ISS) have revealed that large n-alkane droplets can continue to burn quasi-steadily following radiative extinction in a low-temperature regime, characterized by negative-temperaturecoefficient (NTC) chemistry. In this study we report experimental observations of n-heptane, n-octane, and n-decane droplets of varying initial sizes burning in oxygen/nitrogen/carbon dioxide and oxygen/helium/nitrogen environments at 1.0, 0.7, and 0.5 atmospheric pressures. The oxygen concentration in these tests varied in the range of 14% to 25% by volume. Large n-alkane droplets exhibited quasi-steady low-temperature burning and extinction following radiative extinction of the visible flame while smaller droplets burned to completion or disruptively extinguished. A vapor-cloud formed in most cases slightly prior to or following the "cool flame" extinction. Results for droplet burning rates in both the hot-flame and cool-flame regimes as well as droplet extinction diameters at the end of each stage are presented. Time histories of radiant emission from the droplet captured using broadband radiometers are also presented. Remarkably the "cool flame" extinction diameters for all the three n-alkanes follow a trend reminiscent of the ignition delay times observed in previous studies. The similarities and differences among the n-alkanes during "cool flame" combustion are discussed using simplified theoretical models of the phenomenon

SUBSTRATE-SPECIFICITY OF THE ALKANE HYDROXYLASE SYSTEM OF PSEUDOMONAS-OLEOVORANS GPO1

NARCIS (Netherlands)

van Beilen, J.B.; Kingma, Jacob; Witholt, Bernard

1994-01-01

We have studied the hydroxylation of a wide range of linear, branched and cyclic alkanes and alkylbenzenes by the alkane hydroxylase system of Pseudomonas oleovorans GPo1 in vivo and in vitro. In vivo hydroxylation was determined with whole cells of the recombinant PpS8141; P. putida PpS81 carrying

Investigating C4 Grass Contributions to N-alkane Based Paleoclimate Reconstructions

Science.gov (United States)

Doman, C. E.; Enders, S. K.; Chadwick, O.; Freeman, K. H.

2014-12-01

Plant wax n-alkanes are long-chain, saturated hydrocarbons contained within the protective waxy cuticle on leaves. These lipids are pervasive and persistent in soils and sediments and thus are ideal biomarkers of ancient terrestrial organic matter. In ecosystems dominated by C3 plants, the relationship between the carbon isotopic value of whole leaves and lipids is fairly well documented, but this relationship has not been fully investigated for plants that use C4 photosynthesis. In both cases, it is unclear if the isotopic relationships are sensitive to environmental conditions, or reflect inherited characteristics. This study used a natural climate gradient on the Kohala peninsula of Hawaii to investigate relationships between climate and the δ13C and δ2H values of n-alkanes in C3 and C4 plants. δ13C of C3 leaves and lipids decreased 5 ‰ from the driest to the wettest sites, consistent with published data. Carbon isotope values of C4 plants showed no relationship to moisture up to 1000 mm mean annual precipitation (MAP). Above this threshold, δ 13C values were around 10‰ more depleted, likely due to a combination of canopy effects and C4 grasses growing in an uncharacteristically wet and cold environment. In C3 plants, the fractionation between leaf and lipid carbon isotopes did not vary with MAP, which allows estimations of δ13C leaf to be made from alkanes preserved in ancient sediments. Along this transect, C3 plants produce around twice the quantity of n-alkanes as C4 grasses. C4 grasses produce longer carbon chains. As a result, n-alkanes in the geologic record will be biased towards C3 plants, but the presence of alkanes C33 and C35 indicate the contributions of C4 grasses. In both C3 and C4 plants, average chain length increased with mean annual precipitation, but the taxonomic differences in chain length were greater than environmental differences. Hydrogen isotopes of n-alkanes show no trends with MAP, but do show clear differences between plant

Leaf wax n-alkane distributions in and across modern plants: Implications for paleoecology and chemotaxonomy

Science.gov (United States)

Bush, Rosemary T.; McInerney, Francesca A.

2013-09-01

Long chain (C21 to C37) n-alkanes are among the most long-lived and widely utilized terrestrial plant biomarkers. Dozens of studies have examined the range and variation of n-alkane chain-length abundances in modern plants from around the world, and n-alkane distributions have been used for a variety of purposes in paleoclimatology and paleoecology as well as chemotaxonomy. However, most of the paleoecological applications of n-alkane distributions have been based on a narrow set of modern data that cannot address intra- and inter-plant variability. Here, we present the results of a study using trees from near Chicago, IL, USA, as well as a meta-analysis of published data on modern plant n-alkane distributions. First, we test the conformity of n-alkane distributions in mature leaves across the canopy of 38 individual plants from 24 species as well as across a single growing season and find no significant differences for either canopy position or time of leaf collection. Second, we compile 2093 observations from 86 sources, including the new data here, to examine the generalities of n-alkane parameters such as carbon preference index (CPI), average chain length (ACL), and chain-length ratios for different plant groups. We show that angiosperms generally produce more n-alkanes than do gymnosperms, supporting previous observations, and furthermore that CPI values show such variation in modern plants that it is prudent to discard the use of CPI as a quantitative indicator of n-alkane degradation in sediments. We also test the hypotheses that certain n-alkane chain lengths predominate in and therefore can be representative of particular plant groups, namely, C23 and C25 in Sphagnum mosses, C27 and C29 in woody plants, and C31 in graminoids (grasses). We find that chain-length distributions are highly variable within plant groups, such that chemotaxonomic distinctions between grasses and woody plants are difficult to make based on n-alkane abundances. In contrast

Adsorption of different amphiphilic molecules onto polystyrene latices.

Science.gov (United States)

Jódar-Reyes, A B; Ortega-Vinuesa, J L; Martín-Rodríguez, A

2005-02-15

In order to know the influence of the surface characteristics and the chain properties on the adsorption of amphiphilic molecules onto polystyrene latex, a set of experiments to study the adsorption of ionic surfactants, nonionic surfactants and an amphiphilic synthetic peptide on different latex dispersions was performed. The adsorbed amount versus the equilibrium surfactant concentration was determined. The main adsorption mechanism was the hydrophobic attraction between the nonpolar tail of the molecule and the hydrophobic regions of the latex surface. This attraction overcame the electrostatic repulsion between chains and latex surface with identical charge sign. However, the electrostatic interactions chain-surface and chain-chain also played a role. General patterns for the adsorption of ionic chains on charged latex surfaces could be established. Regarding the shape, the isotherms presented different plateaus corresponding to electrostatic effects and conformational changes. The surfactant size also affects the adsorption results: the higher the hydrophilic moiety in the surfactant molecule the lower the adsorbed amount.

Simulation studies on structural and thermal properties of alkane thiol capped gold nanoparticles.

Science.gov (United States)

Devi, J Meena

2017-06-01

The structural and thermal properties of the passivated gold nanoparticles were explored employing molecular dynamics simulation for the different surface coverage densities of the self-assembled monolayer (SAM) of alkane thiol. The structural properties of the monolayer protected gold nanoparticles such us overall shape, organization and conformation of the capping alkane thiol chains were found to be influenced by the capping density. The structural order of the thiol capped gold nanoparticles enhances with the increase in the surface coverage density. The specific heat capacity of the alkane thiol capped gold nanoparticles was found to increase linearly with the thiol coverage density. This may be attributed to the enhancement in the lattice vibrational energy. The present simulation results suggest, that the structural and thermal properties of the alkane thiol capped gold nanoparticles may be modified by the suitable selection of the SAM coverage density. Copyright © 2017 Elsevier Inc. All rights reserved.

A kinetic theory description of the viscosity of dense fluids consisting of chain molecules.

Science.gov (United States)

de Wijn, Astrid S; Vesovic, Velisa; Jackson, George; Trusler, J P Martin

2008-05-28

An expression for the viscosity of a dense fluid is presented that includes the effect of molecular shape. The molecules of the fluid are approximated by chains of equal-sized, tangentially jointed, rigid spheres. It is assumed that the collision dynamics in such a fluid can be approximated by instantaneous collisions between two rigid spheres belonging to different chains. The approach is thus analogous to that of Enskog for a fluid consisting of rigid spheres. The description is developed in terms of two molecular parameters, the diameter sigma of the spherical segment and the chain length (number of segments) m. It is demonstrated that an analysis of viscosity data of a particular pure fluid alone cannot be used to obtain independently effective values of both sigma and m. Nevertheless, the chain lengths of n-alkanes are determined by assuming that the diameter of each rigid sphere making up the chain can be represented by the diameter of a methane molecule. The effective chain lengths of n-alkanes are found to increase linearly with the number C of carbon atoms present. The dependence can be approximated by a simple relationship m=1+(C-1)3. The same relationship was reported within the context of a statistical associating fluid theory equation of state treatment of the fluid, indicating that both the equilibrium thermodynamic properties and viscosity yield the same value for the chain lengths of n-alkanes.

Thermal analysis as an aid to forensics: Alkane melting and oxidative stability of wool

International Nuclear Information System (INIS)

Alan Riga, D.

1998-01-01

Interdisciplinary methods and thermal analytical techniques in particular are effective tools in aiding the identification and characterization of materials in question involved in civil or criminal law. Forensic material science uses systematic knowledge of the physical or material world gained through analysis, observation and experimentation. Thermal analytical data can be used to aid the legal system in interpreting technical variations in quite often a complex system.Calorimetry and thermal microscopic methods helped define a commercial product composed of alkanes that was involved in a major law suit. The solid-state structures of a number of normal alkanes have unique crystal structures. These alkanes melt and freeze below room temperature to more than 60C below zero. Mixtures of specific alkanes have attributes of pure chemicals. The X-ray diffraction structure of a mixture of alkanes is the same as a pure alkane, but the melting and freezing temperature are significantly lower than predicted. The jury ruled that the product containing n-alkanes had the appropriate melting characteristics. The thermal-physical properties made a commercial fluid truly unique and there was no advertising infringement according to the law and the jury trialA combination of thermogravimetry, differential thermal analysis, infrared spectroscopy and macrophotography were used to conduct an extensive modeling and analysis of physical evidence obtained in a mobile home fire and explosion. A person's death was allegedly linked to the misuse of a kerosene space heater. The thermal analytical techniques showed that external heating was the cause of the space heater's deformation, not a firing of the heater with gasoline and kerosene. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Thermal analysis as an aid to forensics: Alkane melting and oxidative stability of wool

Energy Technology Data Exchange (ETDEWEB)

Alan Riga, D. [Professor of Chemistry, Cleveland State University and TechCon Inc., 6325 Aldenham Dr., Cleveland, OH 44143-3331 (United States)

1998-12-21

Interdisciplinary methods and thermal analytical techniques in particular are effective tools in aiding the identification and characterization of materials in question involved in civil or criminal law. Forensic material science uses systematic knowledge of the physical or material world gained through analysis, observation and experimentation. Thermal analytical data can be used to aid the legal system in interpreting technical variations in quite often a complex system.Calorimetry and thermal microscopic methods helped define a commercial product composed of alkanes that was involved in a major law suit. The solid-state structures of a number of normal alkanes have unique crystal structures. These alkanes melt and freeze below room temperature to more than 60C below zero. Mixtures of specific alkanes have attributes of pure chemicals. The X-ray diffraction structure of a mixture of alkanes is the same as a pure alkane, but the melting and freezing temperature are significantly lower than predicted. The jury ruled that the product containing n-alkanes had the appropriate melting characteristics. The thermal-physical properties made a commercial fluid truly unique and there was no advertising infringement according to the law and the jury trialA combination of thermogravimetry, differential thermal analysis, infrared spectroscopy and macrophotography were used to conduct an extensive modeling and analysis of physical evidence obtained in a mobile home fire and explosion. A person's death was allegedly linked to the misuse of a kerosene space heater. The thermal analytical techniques showed that external heating was the cause of the space heater's deformation, not a firing of the heater with gasoline and kerosene. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Molecular dynamics simulation studies of mid-size liquid n-Alkanes, C12–C160

International Nuclear Information System (INIS)

Kwon, Tae Woo; Lee, Song Hi

2015-01-01

In this study, we report the results of molecular dynamics simulations (MD) for model systems of mid-size liquid n-alkanes (C 12 –C 160 ) at several temperatures (⁓2700 K) in canonical ensembles to calculate structural and dynamic properties (viscosity η, self-diffusion constant D, and monomeric friction constant ζ). For the small n-alkanes for n ≤ 80, the chains are clearly ≥ 1, which leads to the conclusion that the liquid n-alkanes are far away from the Rouse regime, but for the n-alkanes for n ≥ 120, the chains are ⁓ 1 and they are Gaussian. It is found that the long chains of these n-alkanes at high temperatures show abnormalities in density, viscosity, and monomeric friction constant. The mass and temperature dependences of structural and dynamic properties (η, D, and ζ) are discussed

Analysis of final products from the liquid alkanes radiolysis at low dose, low temperature and high dose rate

International Nuclear Information System (INIS)

Tilquin, B.; Doncker, J. de.

1991-01-01

Yields of final products (dimers) from the radiolysis of n-hexane and 2,3-dimethylbutane are studied by capillary chromatographic techniques for trace analysis. Reaction of intermediates with the products, the alkane molecules or impurities, is reduced by using low dose (1 kGy), low temperature (195 K) and high dose rate (LINAC). Temperature is the most important experiment variable; by reducing the temperature, reactions with significant activation energies do not compete with radical-radical termination reactions. Products from LINAC radiolysis provide information about active species (reactive fragment, allylic radical...) which deserve a more detailed examination by direct methods [fr

Electrical transport through a metal-molecule-metal junction; Transport electrique a travers une jonction metal-molecule-metal

Energy Technology Data Exchange (ETDEWEB)

Kergueris, Ch

1998-12-17

We investigate the electrical transport through a very few molecules connected to metallic electrodes at room temperature. First, the state of the art in molecular electronics is outlined. We present the most convincing molecular devices reported so far in the literature and the theoretical tools available to analyze the electron transport mechanism through a molecular junction. Second, we describe the use of mechanically controllable break junctions to investigate the electron transport properties through a metal-molecule-metal junction. Two kindsof molecules were adsorbed on the two facing gold electrodes, dodecane-thiol (DT) and bis-thiol-ter-thiophene ({alpha},{omega} T3), that are basically expected to behave as an insulator and as a molecular wire, respectively. In the latter case, we study the chemical reactivity of the molecule and show that {alpha},{omega} T3 is chemically adsorbed on gold electrodes. Current-voltage characteristics of the junction were observed at room temperature. The Gold-DT-Gold junction behaves as a simple metal-insulator-metal junction. On the other hand, the electron transport through a Gold-{alpha},{omega} T3-Gold junction explicitly involves the electronic structure of the molecule which gives rise to step-like features in the current-voltage characteristics. The measured zero bias conductance is interpreted using the scattering theory. At high bias, we discuss two different models: a coherent model where the electron has no time to be completely re-localized in the molecule and a sequential model where the electron is localized in the molecule during the transfer. Finally, we show that the mechanical action of decreasing the inter-electrodes spacing can be used to induce a strong modification of the current-voltage characteristics. (author)

Alkane oxidation by Pseudomonas oleovorans : genes and proteins

NARCIS (Netherlands)

van Beilen, Jan Berthold

1994-01-01

This thesis deals with the molecular genetics and biochemistry of oxidation of medium chainlength alkanes by P. oleovorans, as part of a program to develop biotechnological processes, based on oxygenases.

The environmental effect on the radial breathing mode of carbon nanotubes. II. Shell model approximation for internally and externally adsorbed fluids

Science.gov (United States)

Longhurst, M. J.; Quirke, N.

2006-11-01

We have previously shown that the upshift in the radial breathing mode (RBM) of closed (or infinite) carbon nanotubes in solution is almost entirely due to coupling of the RBM with an adsorbed layer of fluid on the nanotube surface. The upshift can be modeled analytically by considering the adsorbed fluid as an infinitesimally thin shell, which interacts with the nanotube via a continuum Lennard-Jones potential. Here we extend the model to include internally as well as externally adsorbed waterlike molecules, and find that filling the nanotubes leads to an additional upshift of two to six wave numbers. We show that using molecular dynamics, the RBM can be accurately reproduced by replacing the fluid molecules with a mean field harmonic shell potential, greatly reducing simulation times.

sup(60)Co hot atom chemistry of tris(acetylacetonato) cobalt(III) adsorbed on silica gel

International Nuclear Information System (INIS)

Nishioji, H.; Sakai, Y.; Tominaga, T.

1985-01-01

The sup(60)Co hot atom reactions were studied in tris(acetylacetonato)cobalt(III) adsorbed on silica gel surface. sup(57)Fe Moessbauer spectra of tris(acetylacetonato)iron(III) in the corresponding system were also measured in order to examine the state of dispersion of complex molecules on silica gel. The retention formation processes were discussed in terms of the dependence of sup(60)Co retention on the adsorbed amount (concentration) of cobalt(III) complexes. (author)

The Tunable Bandgap of AB-Stacked Bilayer Graphene on SiO2 with H2O Molecule Adsorption

International Nuclear Information System (INIS)

Wang Tao; Guo Qing; Liu Yan; Wang Wen-Bo; Sheng Kuang; Ao Zhi-Min; Yu Bin

2011-01-01

The atomic and electronic structures of AB-stacking bilayer graphene (BLG) in the presence of H 2 O molecules are investigated by density functional theory calculations. For free-standing BLG, the bandgap is opened to 0.101 eV with a single H 2 O molecule adsorbed on its surface. The perfectly suspended BLG is sensitive to H 2 O adsorbates, which break the BLG lattice symmetry and open an energy gap. While a single H 2 O molecule is adsorbed on the BLG surface with a SiO 2 substrate, the bandgap widens to 0.363 eV. Both the H 2 O molecule adsorption and the oxide substrate contribute to the BLG bandgap opening. The phenomenon is interpreted with the charge transfer process in 2D carbon nanostructures. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

New Antifouling Platform Characterized by Single-Molecule Imaging

Science.gov (United States)

2015-01-01

Antifouling surfaces have been widely studied for their importance in medical devices and industry. Antifouling surfaces mostly achieved by methoxy-poly(ethylene glycol) (mPEG) have shown biomolecular adsorption less than 1 ng/cm2 which was measured by surface analytical tools such as surface plasmon resonance (SPR) spectroscopy, quartz crystal microbalance (QCM), or optical waveguide lightmode (OWL) spectroscopy. Herein, we utilize a single-molecule imaging technique (i.e., an ultimate resolution) to study antifouling properties of functionalized surfaces. We found that about 600 immunoglobulin G (IgG) molecules are adsorbed. This result corresponds to ∼5 pg/cm2 adsorption, which is far below amount for the detection limit of the conventional tools. Furthermore, we developed a new antifouling platform that exhibits improved antifouling performance that shows only 78 IgG molecules adsorbed (∼0.5 pg/cm2). The antifouling platform consists of forming 1 nm TiO2 thin layer, on which peptidomimetic antifouling polymer (PMAP) is robustly anchored. The unprecedented antifouling performance can potentially revolutionize a variety of research fields such as single-molecule imaging, medical devices, biosensors, and others. PMID:24503420

New antifouling platform characterized by single-molecule imaging.

Science.gov (United States)

Ryu, Ji Young; Song, In Taek; Lau, K H Aaron; Messersmith, Phillip B; Yoon, Tae-Young; Lee, Haeshin

2014-03-12

Antifouling surfaces have been widely studied for their importance in medical devices and industry. Antifouling surfaces mostly achieved by methoxy-poly(ethylene glycol) (mPEG) have shown biomolecular adsorption less than 1 ng/cm(2) which was measured by surface analytical tools such as surface plasmon resonance (SPR) spectroscopy, quartz crystal microbalance (QCM), or optical waveguide lightmode (OWL) spectroscopy. Herein, we utilize a single-molecule imaging technique (i.e., an ultimate resolution) to study antifouling properties of functionalized surfaces. We found that about 600 immunoglobulin G (IgG) molecules are adsorbed. This result corresponds to ∼5 pg/cm(2) adsorption, which is far below amount for the detection limit of the conventional tools. Furthermore, we developed a new antifouling platform that exhibits improved antifouling performance that shows only 78 IgG molecules adsorbed (∼0.5 pg/cm(2)). The antifouling platform consists of forming 1 nm TiO2 thin layer, on which peptidomimetic antifouling polymer (PMAP) is robustly anchored. The unprecedented antifouling performance can potentially revolutionize a variety of research fields such as single-molecule imaging, medical devices, biosensors, and others.

Preferential methanogenic biodegradation of short-chain n-alkanes by microbial communities from two different oil sands tailings ponds.

Science.gov (United States)

Mohamad Shahimin, Mohd Faidz; Foght, Julia M; Siddique, Tariq

2016-05-15

Oil sands tailings ponds harbor diverse anaerobic microbial communities capable of methanogenic biodegradation of solvent hydrocarbons entrained in the tailings. Mature fine tailings (MFT) from two operators (Albian and CNRL) that use different extraction solvents were incubated with mixtures of either two (n-pentane and n-hexane) or four (n-pentane, n-hexane, n-octane and n-decane) n-alkanes under methanogenic conditions for ~600 d. Microbes in Albian MFT began methane production by ~80 d, achieving complete depletion of n-pentane and n-hexane in the two-alkane mixture and their preferential biodegradation in the four-alkane mixture. Microbes in CNRL MFT preferentially metabolized n-octane and n-decane in the four-alkane mixture after a ~80 d lag but exhibited a lag of ~360 d before commencing biodegradation of n-pentane and n-hexane in the two-alkane mixture. 16S rRNA gene pyrosequencing revealed Peptococcaceae members as key bacterial n-alkane degraders in all treatments except CNRL MFT amended with the four-alkane mixture, in which Anaerolineaceae, Desulfobacteraceae (Desulfobacterium) and Syntrophaceae (Smithella) dominated during n-octane and n-decane biodegradation. Anaerolineaceae sequences increased only in cultures amended with the four-alkane mixture and only during n-octane and n-decane biodegradation. The dominant methanogens were acetoclastic Methanosaetaceae. These results highlight preferential n-alkane biodegradation by microbes in oil sands tailings from different producers, with implications for tailings management and reclamation. Copyright © 2016 Elsevier B.V. All rights reserved.

Scanning tunneling microscopy studies of organic monolayers adsorbed on the rhodium(111) crystal surface

Energy Technology Data Exchange (ETDEWEB)

Cernota, Paul Davis [Univ. of California, Berkeley, CA (United States)

1999-08-01

Scanning Tunneling Microscopy studies were carried out on ordered overlayers on the (111) surface of rhodium. These adsorbates include carbon monoxide (CO), cyclohexane, cyclohexene, 1,4-cyclohexadiene, para-xylene, and meta-xylene. Coadsorbate systems included: CO with ethylidyne, CO with para- and meta-xylene, and para-xylene with meta-xylene. In the case of CO, the structure of the low coverage (2x2) overlayer has been observed. The symmetry of the unit cell in this layer suggests that the CO is adsorbed in the 3-fold hollow sites. There were also two higher coverage surface structures with (√7x√7) unit cells. One of these is composed of trimers of CO and has three CO molecules in each unit cell. The other structure has an additional CO molecule, making a total of four. This extra CO sits on a top site.

Gas chromatographic-mass spectrometric investigation of n-alkanes and carboxylic acids in bottom sediments of the northern Caspian Sea

Science.gov (United States)

Kenzhegaliev, Akimgali; Zhumagaliev, Sagat; Kenzhegalieva, Dina; Orazbayev, Batyr

2018-03-01

Prior to the start of experimental oil production in the Kashagan field (northern part of the Caspian Sea), n-alkanes and carboxylic acids contained in samples obtained from bottom sediments in the area of artificial island "D" were investigated by gas chromatography-mass spectrometry. Concentrations of 10 n-alkanes (composed of C10-C13, C15-C20) and 11 carboxylic acids (composed of C6-C12, C14-C16) were identified and measured. Concentrations of individual alkanes and carboxylic acids in bottom sediments of the various samples varied between 0.001 ÷ 0.88 μg/g and 0.001 ÷ 1.94 μg/g, respectively. Mass spectra, in particular the M+ molecular ion peak and the most intense peaks of fragment ions, are given. The present study illustrates the stability of molecular ions to electronic ionisation and the main fragment ions to the total ion current and shows that the initial fragmentation of alkanes implies radical cleavage of C2H5 rather than CH3. All aliphatic monocarboxylic acids studied were characterised by McLafferty rearrangement leading to the formation of F4 cation-radical with m/z 60 and F3 cation-radical with m/z 88 in the case of ethylhexanoic acid. The formation of oxonium ions presents another important aspect of acid fragmentation. Using mass numbers of oxonium ions and rearrangement ions allows determination of the substitution character in α- and β- C atoms. The essence of our approach is to estimate the infiltration of hydrocarbon fluids from the enclosing formation into sea water, comprising an analysis of derivatives of organic compounds in bottom sediments. Thus, concentrations of derived organic molecules can serve as a basis for estimates of the depth at which hydrocarbon fluids leak, i.e., to serve as an auxiliary technique in the search for hydrocarbon deposits and to repair well leaks.

Surface-enhanced Raman spectrum of Gly-Gly adsorbed on the silver colloidal surface

Science.gov (United States)

Xiaojuan, Yuan; Huaimin, Gu; Jiwei, Wu

2010-08-01

Raman and SERS spectra of homodipeptide Gly-Gly and Gly were recorded and compared in this paper, and band assignment for the functional groups contained in these molecules was analyzed in detail. Time-dependent and pH-dependent SERS spectra of Gly-Gly molecule adsorbed on nano-colloidal silver surface were also studied. The time-dependent SERS spectra of Gly-Gly are characterized by the increase in intensity of bands primarily representing the vibrational signatures emanating from the amino and amide moiety of Gly-Gly molecule. It is found that the adsorption style of Gly-Gly on the silver colloid changes as time goes on; at 5 min after adding the sample to the silver colloid, Gly-Gly adsorbs on silver surface firstly through the carboxylate, amino and amide groups, and then the carboxylate group is far away from the silver surface at 10 min to 3 days. The SERS variation of Gly-Gly with the change of pH suggests that the adsorption style is pH-dependent, the different adsorption behavior of the Gly-Gly occurs on silver surface at different pH values.

Electron-Stimulated Desorption of Positive Ions from Methanol Adsorbed on a Solid Ar Substrate

Science.gov (United States)

Kawanowa, H.; Hanatani, K.; Gotoh, Y.; Souda, R.

Electron-stimulated desorption (ESD) of positive ions from weakly physisorbed molecules has been investigated. From methanol adsorbed on a solid Ar substrate, the protonated cluster ions of the type H+(CH3OH)n (n = 1 - 4) are emitted, together with the fragment ions such as CHn+ (n = 0 - 3), H3O+, CHO+, CH3O+, etc. The yields of these ions are markedly enhanced at the smallest coverage and decay steeply with increasing coverage. Coulomb explosion between valence holes confined in adsorbed nanoclusters is responsible for the enhanced ion yields. Very few ions except for H+ are emitted from a thick layer as well as nanoclusters adsorbed directly on a metal substrate due to the delocalization of valence holes.

An in situ XPS study of L-cysteine co-adsorbed with water on polycrystalline copper and gold

Science.gov (United States)

Jürgensen, Astrid; Raschke, Hannes; Esser, Norbert; Hergenröder, Roland

2018-03-01

The interactions of biomolecules with metal surfaces are important because an adsorbed layer of such molecules introduces complex reactive functionality to the substrate. However, studying these interactions is challenging: they usually take place in an aqueous environment, and the structure of the first few monolayers on the surface is of particular interest, as these layers determine most interfacial properties. Ideally, this requires surface sensitive analysis methods that are operated under ambient conditions, for example ambient pressure x-ray photoelectron spectroscopy (AP-XPS). This paper focuses on an AP-XPS study of the interaction of water vapour and l-Cysteine on polycrystalline copper and gold surfaces. Thin films of l-Cysteine were characterized with XPS in UHV and in a water vapour atmosphere (P ≤ 1 mbar): the structure of the adsorbed l-Cysteine layer depended on substrate material and deposition method, and exposure of the surface to water vapour led to the formation of hydrogen bonds between H2O molecules and the COO- and NH2 groups of adsorbed l-Cysteine zwitterions and neutral molecules, respectively. This study also proved that it is possible to investigate monolayers of biomolecules in a gas atmosphere with AP-XPS using a conventional laboratory Al-Kα x-ray source.

Development of a computationally-designed polymeric adsorbent specific for mycotoxin patulin.

Science.gov (United States)

Piletska, Elena V; Pink, Demi; Karim, Kal; Piletsky, Sergey A

2017-12-04

Patulin is a toxic compound which is found predominantly in apples affected by mould rot. Since apples and apple-containing products are a popular food for the elderly, children and babies, the monitoring of the toxin is crucial. This paper describes a development of a computationally-designed polymeric adsorbent for the solid-phase extraction of patulin, which provides an effective clean-up of the food samples and allows the detection and accurate quantification of patulin levels present in apple juice using conventional chromatography methods. The developed bespoke polymer demonstrates a quantitative binding towards the patulin present in undiluted apple juice. The polymer is inexpensive and easy to mass-produce. The contributing factors to the function of the adsorbent is a combination of acidic and basic functional monomers producing a zwitterionic complex in the solution that formed stronger binding complexes with the patulin molecule. The protocols described in this paper provide a blueprint for the development of polymeric adsorbents for other toxins or different food matrices.

Anchoring of alkyl chain molecules on oxide surface using silicon alkoxide

Energy Technology Data Exchange (ETDEWEB)

Narita, Ayumi, E-mail: narita.ayumi@jaea.go.jp [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan); Graduate School of Science and Engineering, Ibaraki University, Bunnkyo, Mito-shi, Ibaraki-ken 310-8512 (Japan); Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan); Yaita, Tsuyoshi [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan); Graduate School of Science and Engineering, Ibaraki University, Bunnkyo, Mito-shi, Ibaraki-ken 310-8512 (Japan)

2012-01-01

Chemical states of the interfaces between octadecyl-triethoxy-silane (ODTS) molecules and sapphire surface were measured by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) using synchrotron soft X-rays. The nearly self-assembled monolayer of ODTS was formed on the sapphire surface. For XPS and NEXAFS measurements, it was elucidated that the chemical bond between silicon alkoxide in ODTS and the surface was formed, and the alkane chain of ODTS locates upper side on the surface. As a result, it was elucidated that the silicon alkoxide is a good anchor for the immobilization of organic molecules on oxides.

Alkane Hydroxylase Gene (alkB Phylotype Composition and Diversity in Northern Gulf of Mexico Bacterioplankton

Directory of Open Access Journals (Sweden)

Conor Blake Smith

2013-12-01

Full Text Available Natural and anthropogenic activities introduce alkanes into marine systems where they are degraded by alkane hydroxylases expressed by phylogenetically diverse bacteria. Partial sequences for alkB, one of the structural genes of alkane hydroxylase, have been used to assess the composition of alkane-degrading communities, and to determine their responses to hydrocarbon inputs. We present here the first spatially extensive analysis of alkB in bacterioplankton of the northern Gulf of Mexico (nGoM, a region that experiences numerous hydrocarbon inputs. We have analyzed 401 partial alkB gene sequences amplified from genomic extracts collected during March 2010 from 17 water column samples that included surface waters and bathypelagic depths. Previous analyses of 16S rRNA gene sequences for these and related samples have shown that nGoM bacterial community composition and structure stratify strongly with depth, with distinctly different communities above and below 100 m. Although we hypothesized that alkB gene sequences would exhibit a similar pattern, PCA analyses of operational protein units (OPU indicated that community composition did not vary consistently with depth or other major physical-chemical variables. We observed 22 distinct OPUs, one of which was ubiquitous and accounted for 57% of all sequences. This OPU clustered with alkB sequences from known hydrocarbon oxidizers (e.g., Alcanivorax and Marinobacter. Some OPUs could not be associated with known alkane degraders, however, and perhaps represent novel hydrocarbon-oxidizing populations or genes. These results indicate that the capacity for alkane hydrolysis occurs widely in the nGoM, but that alkane degrader diversity varies substantially among sites and responds differently than bulk communities to physical-chemical variables.

Alkane Biosynthesis Genes in Cyanobacteria and Their Transcriptional Organization

International Nuclear Information System (INIS)

Klähn, Stephan; Baumgartner, Desirée; Pfreundt, Ulrike; Voigt, Karsten; Schön, Verena; Steglich, Claudia; Hess, Wolfgang R.

2014-01-01

In cyanobacteria, alkanes are synthesized from a fatty acyl-ACP by two enzymes, acyl–acyl carrier protein reductase and aldehyde deformylating oxygenase. Despite the great interest in the exploitation for biofuel production, nothing is known about the transcriptional organization of their genes or the physiological function of alkane synthesis. The comparison of 115 microarray datasets indicates the relatively constitutive expression of aar and ado genes. The analysis of 181 available genomes showed that in 90% of the genomes both genes are present, likely indicating their physiological relevance. In 61% of them they cluster together with genes encoding acetyl-CoA carboxyl transferase and a short-chain dehydrogenase, strengthening the link to fatty acid metabolism and in 76% of the genomes they are located in tandem, suggesting constraints on the gene arrangement. However, contrary to the expectations for an operon, we found in Synechocystis sp. PCC 6803 specific promoters for the two genes, sll0208 (ado) and sll0209 (aar), which give rise to monocistronic transcripts. Moreover, the upstream located ado gene is driven by a proximal as well as a second, distal, promoter, from which a third transcript, the ~160 nt sRNA SyR9 is transcribed. Thus, the transcriptional organization of the alkane biosynthesis genes in Synechocystis sp. PCC 6803 is of substantial complexity. We verified all three promoters to function independently from each other and show a similar promoter arrangement also in the more distant Nodularia spumigena, Trichodesmium erythraeum, Anabaena sp. PCC 7120, Prochlorococcus MIT9313, and MED4. The presence of separate regulatory elements and the dominance of monocistronic mRNAs suggest the possible autonomous regulation of ado and aar. The complex transcriptional organization of the alkane synthesis gene cluster has possible metabolic implications and should be considered when manipulating the expression of these genes in cyanobacteria.

Alkane biosynthesis genes in cyanobacteria and their transcriptional organization

Directory of Open Access Journals (Sweden)

Stephan eKlähn

2014-07-01

Full Text Available In cyanobacteria, alkanes are synthesized from a fatty acyl-ACP by two enzymes, acyl-acyl carrier protein reductase (AAR and aldehyde deformylating oxygenase (ADO. Despite the great interest in the exploitation for biofuel production, nothing is known about the transcriptional organization of their genes or the physiological function of alkane synthesis. The comparison of 115 microarray datasets indicates the relatively constitutive expression of aar and ado genes. The analysis of 181 available genomes showed that in 90% of the genomes both genes are present, likely indicating their physiological relevance. In 61% of them they cluster together with genes encoding acetyl-CoA carboxyl transferase and a short chain dehydrogenase, strengthening the link to fatty acid metabolism and in 76% of the genomes they are located in tandem, suggesting constraints on the gene arrangement. However, contrary to the expectations for an operon, we found in Synechocystis sp. PCC 6803 specific promoters for the two genes, sll0208 (ado and sll0209 (aar, that give rise to monocistronic transcripts. Moreover, the upstream located ado gene is driven by a proximal as well as a second, distal, promoter, from which a third transcript, the ~160 nt sRNA SyR9 is transcribed. Thus, the transcriptional organization of the alkane biosynthesis genes in Synechocystis sp. PCC 6803 is of substantial complexity. We verified all three promoters to function independently from each other and show a similar promoter arrangement also in the more distant Nodularia spumigena, Trichodesmium erythraeum, Anabaena sp. PCC 7120, Prochlorococcus MIT9313 and MED4. The presence of separate regulatory elements and the dominance of monocistronic mRNAs suggest the possible autonomous regulation of ado and aar. The complex transcriptional organization of the alkane synthesis gene cluster has possible metabolic implications and should be considered when manipulating the expression of these genes in

Alkane Biosynthesis Genes in Cyanobacteria and Their Transcriptional Organization

Energy Technology Data Exchange (ETDEWEB)

Klähn, Stephan; Baumgartner, Desirée; Pfreundt, Ulrike; Voigt, Karsten; Schön, Verena; Steglich, Claudia; Hess, Wolfgang R., E-mail: wolfgang.hess@biologie.uni-freiburg.de [Genetics and Experimental Bioinformatics, Institute of Biology 3, Faculty of Biology, University of Freiburg, Freiburg (Germany)

2014-07-14

In cyanobacteria, alkanes are synthesized from a fatty acyl-ACP by two enzymes, acyl–acyl carrier protein reductase and aldehyde deformylating oxygenase. Despite the great interest in the exploitation for biofuel production, nothing is known about the transcriptional organization of their genes or the physiological function of alkane synthesis. The comparison of 115 microarray datasets indicates the relatively constitutive expression of aar and ado genes. The analysis of 181 available genomes showed that in 90% of the genomes both genes are present, likely indicating their physiological relevance. In 61% of them they cluster together with genes encoding acetyl-CoA carboxyl transferase and a short-chain dehydrogenase, strengthening the link to fatty acid metabolism and in 76% of the genomes they are located in tandem, suggesting constraints on the gene arrangement. However, contrary to the expectations for an operon, we found in Synechocystis sp. PCC 6803 specific promoters for the two genes, sll0208 (ado) and sll0209 (aar), which give rise to monocistronic transcripts. Moreover, the upstream located ado gene is driven by a proximal as well as a second, distal, promoter, from which a third transcript, the ~160 nt sRNA SyR9 is transcribed. Thus, the transcriptional organization of the alkane biosynthesis genes in Synechocystis sp. PCC 6803 is of substantial complexity. We verified all three promoters to function independently from each other and show a similar promoter arrangement also in the more distant Nodularia spumigena, Trichodesmium erythraeum, Anabaena sp. PCC 7120, Prochlorococcus MIT9313, and MED4. The presence of separate regulatory elements and the dominance of monocistronic mRNAs suggest the possible autonomous regulation of ado and aar. The complex transcriptional organization of the alkane synthesis gene cluster has possible metabolic implications and should be considered when manipulating the expression of these genes in cyanobacteria.

Electron and photon-beam induced reactions of adsorbed disilane: Low-temperature thin-film growth

International Nuclear Information System (INIS)

Bozso, F.; Avouris, Ph.

1991-01-01

Electrons and photons of sufficient energy can cause fragmentation and desorption of adsorbed molecules or fragments of them, by inducing electronic excitations to dissociative states. The surface species after such excitations are mostly of highly reactive radical character, which readily react with the substrate and with other molecular or radical species in the adsorbed layer. This paper discusses the adsorption, thermal and electron/photon-beam induced reactions of disilane, oxygen and ammonia on Si(111)-7x7, and the electron/photon-induced growth of silicon, silicon dioxide and silicon nitride films at 100K

n-Alkane assimilation and tert-butyl alcohol (TBA) oxidation capacity in Mycobacterium austroafricanum strains.

Science.gov (United States)

Lopes Ferreira, Nicolas; Mathis, Hugues; Labbé, Diane; Monot, Frédéric; Greer, Charles W; Fayolle-Guichard, Françoise

2007-06-01

Mycobacterium austroafricanum IFP 2012, which grows on methyl tert-butyl ether (MTBE) and on tert-butyl alcohol (TBA), the main intermediate of MTBE degradation, also grows on a broad range of n-alkanes (C2 to C16). A single alkB gene copy, encoding a non-heme alkane monooxygenase, was partially amplified from the genome of this bacterium. Its expression was induced after growth on n-propane, n-hexane, n-hexadecane and on TBA but not after growth on LB. The capacity of other fast-growing mycobacteria to grow on n-alkanes (C1 to C16) and to degrade TBA after growth on n-alkanes was compared to that of M. austroafricanum IFP 2012. We studied M. austroafricanum IFP 2012 and IFP 2015 able to grow on MTBE, M. austroafricanum IFP 2173 able to grow on isooctane, Mycobacterium sp. IFP 2009 able to grow on ethyl tert-butyl ether (ETBE), M. vaccae JOB5 (M. austroaafricanum ATCC 29678) able to degrade MTBE and TBA and M. smegmatis mc2 155 with no known degradation capacity towards fuel oxygenates. The M. austroafricanum strains grew on a broad range of n-alkanes and three were able to degrade TBA after growth on propane, hexane and hexadecane. An alkB gene was partially amplified from the genome of all mycobacteria and a sequence comparison demonstrated a close relationship among the M. austroafricanum strains. This is the first report suggesting the involvement of an alkane hydroxylase in TBA oxidation, a key step during MTBE metabolism.

Regioselective alkane hydroxylation with a mutant CYP153A6 enzyme

Science.gov (United States)

Koch, Daniel J.; Arnold, Frances H.

2013-01-29

Cytochrome P450 CYP153A6 from Myobacterium sp. strain HXN1500 was engineered using in-vivo directed evolution to hydroxylate small-chain alkanes regioselectively. Mutant CYP153A6-BMO1 selectively hydroxylates butane and pentane at the terminal carbon to form 1-butanol and 1-pentanol, respectively, at rates greater than wild-type CYP153A6 enzymes. This biocatalyst is highly active for small-chain alkane substrates and the regioselectivity is retained in whole-cell biotransformations.

Critical constants and acentric factors for long-chain alkanes suitable for corresponding states applications

DEFF Research Database (Denmark)

Kontogeorgis, Georgios; Dimitrios, Tassios

1997-01-01

Several methods for the estimation of the critical temperature T-c, the critical pressure P-c, and the acentric factor omega for long-chain n-alkanes are reviewed and evaluated for the prediction of vapor pressures using Corresponding States (CS) methods, like the Lee-Kesler equation and the cubic....... Anselme, Correlation of the critical properties of alkanes and alkanols, Fluid Phase Equilibria, 56 (1990) 153-169; W. Hu, J. Lovland and P. Vonka. Generalized vapor pressure equations for n-alkanes, 1-alkenes, and 1-alkanols, Presented at the 11th Int. Congress of Chemical Engineering, Chemical Equipment...

Cyclooctane metathesis catalyzed by silica-supported tungsten pentamethyl [(ΞSiO)W(Me)5]: Distribution of macrocyclic alkanes

KAUST Repository

Riache, Nassima

2014-10-03

Metathesis of cyclic alkanes catalyzed by the new surface complex [(ΞSiO)W(Me)5] affords a wide distribution of cyclic and macrocyclic alkanes. The major products with the formula CnH2n are the result of either a ring contraction or ring expansion of cyclooctane leading to lower unsubstituted cyclic alkanes (5≤n≤7) and to an unprecedented distribution of unsubstituted macrocyclic alkanes (12≤n≤40), respectively, identified by GC/MS and by NMR spectroscopies.

Photoelectron diffraction studies of small adsorbates on single crystal surfaces

International Nuclear Information System (INIS)

Pascal, Mathieu

2002-01-01

The structural determination of small molecules adsorbed on single crystal surfaces has been investigated using scanned energy mode photoelectron diffraction (PhD). The experimental PhD data were compared to theoretical models using a simulation program based on multiple scattering calculations. Three adsorption systems have been examined on Ag(110), Cu(110) and Cu(111) crystals. The structure of the (2x1)-O adsorption phase on Ag(110) revealed that the O atoms occupied the long bridge site and are almost co-planar with the top layer of Ag atoms. The best agreement between multiple scattering theory and experiment has been obtained for a missing-row (or equivalently an 'added- row') reconstruction. Alternative buckled-row and unreconstructed surface models can be excluded. The adsorption of the benzoate species on Cu(110) has been found to occur via the carboxylate group. The molecules occupy short bridge sites with the O atoms being slightly displaced from atop sites and are aligned along the close-packed azimuth. The tilt of the molecule with respect to the surface and the degree to which the surface is relaxed have also been investigated. The adsorption of methyl on Cu(111) was studied using either azomethane or methyl iodide to prepare the surface layers. At saturation coverage the preferred adsorption site is the fcc threefold hollow site, whereas at half saturation coverage ∼ 30 % of the methyl species occupy the hop threefold hollow sites. Best agreement between theory and experiment corresponded to a methyl group adsorbed with C 3v symmetry. The height of the C above the surface in a pure methyl layer was 1.66 ± 0.02 A, but was reduced to 1.62 ± 0.02 A in the presence of co-adsorbed iodine, suggesting that iodine increases the strength of adsorption. Iodine was also found to occupy the fee threefold hollow sites with a Cu-l bondlength of 2.61 ± 0.02 A. (author)

SERS and DFT study of p-hydroxybenzoic acid adsorbed on colloidal silver particles.

Science.gov (United States)

Chen, Y; Chen, S J; Li, S; Wei, J J

2015-10-16

In this study, normal Raman spectra of p—hydroxybenzoic acid (PHBA) powder and its surface—enhanced Raman scattering (SERS) spectra in silver colloidal solutions were measured under near infrared excitation conditions. In theoretical calculation, two models of PHBA adsorbed on the surfaces of silver nanoparticles were established. The Raman frequencies of these two models using density functional theory (DFT) method were calculated, and compared with the experimental results. It was found that the calculated Raman frequencies were in good agreement with experimental values, which indicates that there are two enhanced mechanism physical (electromagnetic, EM) enhancement and chemical (charge—transfer, CT) enhancement, in silver colloidal solutions regarding SERS effect. Furthermore, from high—quality SERS spectrum of PHBA obtained in silver colloids, we inferred that PHBA molecules in silver colloids adsorb onto the metal surfaces through carboxyl at a perpendicular orientation. The combination of SERS spectra and DFT calculation is thus useful for studies of the adsorption—orientation of a molecule on a metal colloid.

Frontier molecular orbitals of a single molecule adsorbed on thin insulating films supported by a metal substrate: electron and hole attachment energies.

Science.gov (United States)

Scivetti, Iván; Persson, Mats

2017-09-06

We present calculations of vertical electron and hole attachment energies to the frontier orbitals of a pentacene molecule absorbed on multi-layer sodium chloride films supported by a copper substrate using a simplified density functional theory (DFT) method. The adsorbate and the film are treated fully within DFT, whereas the metal is treated implicitly by a perfect conductor model. We find that the computed energy gap between the highest and lowest unoccupied molecular orbitals-HOMO and LUMO -from the vertical attachment energies increases with the thickness of the insulating film, in agreement with experiments. This increase of the gap can be rationalised in a simple dielectric model with parameters determined from DFT calculations and is found to be dominated by the image interaction with the metal. We find, however, that this simplified model overestimates the downward shift of the energy gap in the limit of an infinitely thick film.

Structure and phase transitions of monolayers of intermediate-length n-alkanes on graphite studied by neutron diffraction and molecular dynamics simulation

DEFF Research Database (Denmark)

Diama, A.; Matthies, B.; Herwig, K. W.

2009-01-01

measurements indicate that the two monolayer films differ principally in the transition temperatures between phases. At the lowest temperatures, both C24 and C32 form a crystalline monolayer phase with a rectangular-centered (RC) structure. The two sublattices of the RC structure each consists of parallel rows...... show evidence of broadening of the lamella boundaries as a result of molecules diffusing parallel to their long axis. At still higher temperatures, they indicate that the introduction of gauche defects into the alkane chains drives a melting transition to a monolayer fluid phase as reported previously...

Vibrational properties of water molecules adsorbed in different zeolitic frameworks

International Nuclear Information System (INIS)

Crupi, V; Longo, F; Majolino, D; Venuti, V

2006-01-01

The perturbation of water 'sorbed' in samples of zeolites of different structural type, genesis, and cation composition (K-, Na-, Mg- and Ca-rich zeolites), namely the CHA framework of a synthetic K-chabazite, the LTA framework of synthetic Na-A and Mg50-A zeolites, and the NAT framework of a natural scolecite, has been studied by FTIR-ATR spectroscopy, in the -10 to +80 o C temperature range. The aim was to show how differences in the chemical composition and/or in the topology of the zeolite framework and, in particular, the possibility for the guest water molecules to develop guest-guest and/or host-guest interactions, lead to substantial differences in their vibrational dynamical properties. The spectra, collected in the O-H stretching and H 2 O bending mode regions, are complex, with multiple bands being observed. As far as water in the CHA and LTA frameworks is concerned, whose behaviour is governed by the balance of water-water, water-framework and water-extra-framework cations interactions, the assignment of the resolved components of the O-H stretching band has been discussed by fitting the band shapes into individual components attributed to H 2 O molecules engaged in different degrees of hydrogen bonding. A detailed quantitative picture of the connectivity pattern of water, as a function of temperature and according to the chemical and topological properties of the environment, is furnished. The H 2 O bending vibrational bands give additional information that perfectly agrees with the results obtained from the analysis of the O-H stretching spectral region. In the case of scolecite, a small-pored zeolite where water-water interactions are eliminated, the increased complexity observed in the infrared spectra in the O-H stretching and H 2 O bending regions was explained as due to the hydrogen bonding between the water molecules and the network, and also with the extra-framework cation. Furthermore, these observations have been correlated with the different

40 CFR 721.10103 - Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear.

Science.gov (United States)

2010-07-01

...-alkane, branched and linear. 721.10103 Section 721.10103 Protection of Environment ENVIRONMENTAL..., branched and linear. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as naphtha (fischer-tropsch), C4-11-alkane, branched and linear (PMN P-04-235; CAS No...

A molecular dynamics study on the transport of a charged biomolecule in a polymeric adsorbent medium and its adsorption onto a charged ligand.

Science.gov (United States)

Riccardi, E; Wang, J-C; Liapis, A I

2010-08-28

The transport of a charged adsorbate biomolecule in a porous polymeric adsorbent medium and its adsorption onto the covalently immobilized ligands have been modeled and investigated using molecular dynamics modeling and simulations as the third part of a novel fundamental methodology developed for studying ion-exchange chromatography based bioseparations. To overcome computational challenges, a novel simulation approach is devised where appropriate atomistic and coarse grain models are employed simultaneously and the transport of the adsorbate is characterized through a number of locations representative of the progress of the transport process. The adsorbate biomolecule for the system studied in this work changes shape, orientation, and lateral position in order to proceed toward the site where adsorption occurs and exhibits decreased mass transport coefficients as it approaches closer to the immobilized ligand. Furthermore, because the ligands are surrounded by counterions carrying the same type of charge as the adsorbate biomolecule, it takes the biomolecule repeated attempts to approach toward a ligand in order to displace the counterions in the proximity of the ligand and to finally become adsorbed. The formed adsorbate-ligand complex interacts with the counterions and polymeric molecules and is found to evolve slowly and continuously from one-site (monovalent) interaction to multisite (multivalent) interactions. Such a transition of the nature of adsorption reduces the overall adsorption capacity of the ligands in the adsorbent medium and results in a type of surface exclusion effect. Also, the adsorption of the biomolecule also presents certain volume exclusion effects by not only directly reducing the pore volume and the availability of the ligands in the adjacent regions, but also causing the polymeric molecules to change to more compact structures that could further shield certain ligands from being accessible to subsequent adsorbate molecules. These

Hydrogenation and hydrodeoxygenation of biomass-derived oxygenates to liquid alkanes for transportation fuels.

Science.gov (United States)

Sun, Shaohui; Yang, Ruishu; Wang, Xin; Yan, Shaokang

2018-04-01

An attractive approach for the production of transportation fuels from renewable biomass resources is to convert oxygenates into alkanes. In this paper, C 5 -C 20 alkanes formed via the hydrogenation and hydrodeoxygenation of the oligomers of furfuryl alcohol(FA) can be used as gasoline, diesel and jet fuel fraction. The first step of the process is the oligomers of FA convert into hydrogenated products over Raney Ni catalyst in a batch reactor. The second step of the process converts hydrogenated products to alkanes via hydrodeoxygenation over different bi-functional catalysts include hydrogenation and acidic deoxidization active sites. After this process, the oxygen content decreased from 22.1 wt% in the oligomers of FA to 0.58 wt% in the hydrodeoxygenation products.

Surface enhanced Raman scattering of new acridine based fluorophore adsorbed on silver electrode

Science.gov (United States)

Solovyeva, Elena V.; Myund, Liubov A.; Denisova, Anna S.

2015-10-01

4,5-Bis(N,N-di(2-hydroxyethyl)iminomethyl)acridine (BHIA) is a new acridine based fluoroionophore and a highly-selective sensor for cadmium ion. The direct interaction of the aromatic nitrogen atom with a surface is impossible since there are bulky substituents in the 4,5-positions of the acridine fragment. Nevertheless BHIA molecule shows a reliable SERS spectrum while adsorbed on a silver electrode. The analysis of SERS spectra pH dependence reveals that BHIA species adsorbed on a surface can exist in both non-protonated and protonated forms. The adsorption of BHIA from alkaline solution is accompanied by carbonaceous species formation at the surface. The intensity of such "carbon bands" turned out to be related with the supporting electrolyte (KCl) concentration. Upon lowering the electrode potential the SERS spectra of BHIA do not undergo changes but the intensity of bands decreases. This indicates that the adsorption mechanism on the silver surface is realized via aromatic system of acridine fragment. In case of such an adsorption mechanism the chelate fragment of the BHIA molecule is capable of interaction with the solution components. Addition of Cd2+ ions to a system containing BHIA adsorbed on a silver electrode in equilibrium with the solution leads to the formation of BHIA/Cd2+ complex which desorption causes the loss of SERS signal.

Analysis of alkane-dependent methanogenic community derived from production water of a high-temperature petroleum reservoir

Energy Technology Data Exchange (ETDEWEB)

Mbadinga, Serge Maurice; Li, Kai-Ping; Zhou, Lei; Wang, Li-Ying; Yang, Shi-Zhong; Liu, Jin-Feng; Mu, Bo-Zhong [East China Univ. of Science and Technology, Shanghai (China). State Key Lab. of Bioreactor Engineering and Inst. of Applied Chemistry; Gu, Ji-Dong [Hong Kong Univ. (China). School of Biological Sciences

2012-10-15

Microbial assemblage in an n-alkanes-dependent thermophilic methanogenic enrichment cultures derived from production waters of a high-temperature petroleum reservoir was investigated in this study. Substantially higher amounts of methane were generated from the enrichment cultures incubated at 55 C for 528 days with a mixture of long-chain n-alkanes (C{sub 15}-C{sub 20}). Stoichiometric estimation showed that alkanes-dependent methanogenesis accounted for about 19.8% of the total amount of methane expected. Hydrogen was occasionally detected together with methane in the gas phase of the cultures. Chemical analysis of the liquid cultures resulted only in low concentrations of acetate and formate. Phylogenetic analysis of the enrichment revealed the presence of several bacterial taxa related to Firmicutes, Thermodesulfobiaceae, Thermotogaceae, Nitrospiraceae, Dictyoglomaceae, Candidate division OP8 and others without close cultured representatives, and Archaea predominantly related to uncultured members in the order Archaeoglobales and CO{sub 2}-reducing methanogens. Screening of genomic DNA retrieved from the alkanes-amended enrichment cultures also suggested the presence of new alkylsuccinate synthase alpha-subunit (assA) homologues. These findings suggest the presence of poorly characterized (putative) anaerobic n-alkanes degraders in the thermophilic methanogenic enrichment cultures. Our results indicate that methanogenesis of alkanes under thermophilic condition is likely to proceed via syntrophic acetate and/or formate oxidation linked with hydrogenotrophic methanogenesis. (orig.)

Alkane-grown Beauveria bassiana produce mycelial pellets displaying peroxisome proliferation, oxidative stress, and cell surface alterations.

Science.gov (United States)

Huarte-Bonnet, Carla; Paixão, Flávia R S; Ponce, Juan C; Santana, Marianela; Prieto, Eduardo D; Pedrini, Nicolás

2018-06-01

The entomopathogenic fungus Beauveria bassiana is able to grow on insect cuticle hydrocarbons, inducing alkane assimilation pathways and concomitantly increasing virulence against insect hosts. In this study, we describe some physiological and molecular processes implicated in growth, nutritional stress response, and cellular alterations found in alkane-grown fungi. The fungal cytology was investigated using light and transmission electron microscopy while the surface topography was examined using atomic force microscopy. Additionally, the expression pattern of several genes associated with oxidative stress, peroxisome biogenesis, and hydrophobicity were analysed by qPCR. We found a novel type of growth in alkane-cultured B. bassiana similar to mycelial pellets described in other alkane-free fungi, which were able to produce viable conidia and to be pathogenic against larvae of the beetles Tenebrio molitor and Tribolium castaneum. Mycelial pellets were formed by hyphae cumulates with high peroxidase activity, exhibiting peroxisome proliferation and an apparent surface thickening. Alkane-grown conidia appeared to be more hydrophobic and cell surfaces displayed different topography than glucose-grown cells. We also found a significant induction in several genes encoding for peroxins, catalases, superoxide dismutases, and hydrophobins. These results show that both morphological and metabolic changes are triggered in mycelial pellets derived from alkane-grown B. bassiana. Copyright © 2017 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

On the relation between Zenkevich and Wiener indices of alkanes

Directory of Open Access Journals (Sweden)

ZARKO BOSKOVIC

2004-04-01

Full Text Available A relatively complicated relation was found to exist between the quantity U, recently introduced by Zenkevich (providing a measure of internal molecular energy, and the Wiener index W (measuring molecular surface area and intermolecular forces. We now report a detailed analysis of this relation and show that, in the case of alkanes, its main features are reproduced by the formula U = –aW + b + gn1; where n1 is the number of methyl groups, and a, b and g are constants, depending only on the number of carbon atoms. Thus, for isomeric alkanes with the same number of methyl groups, U and W are linearly correlated.

Structural and Kinetic Studies of Novel Cytochrome P450 Small-Alkane Hydroxylases

Energy Technology Data Exchange (ETDEWEB)

Arnold, Frances H.

2012-02-27

The goals of this project are to investigate (1) the kinetics and stabilities of engineered cytochrome P450 (P450) small alkane hydroxylases and their evolutionary intermediates, (2) the structural basis for catalytic proficiency on small alkanes of these engineered P450s, and (3) the changes in redox control resulting from protein engineering. To reach these goals, we have established new methods for determining the kinetics and stabilities of multicomponent P450s such as CYP153A6. Using these, we were able to determine that CYP153A6 is proficient for hydroxylation of alkanes as small as ethane, an activity that has never been observed previously in any natural P450. To elucidate the structures of the engineered P450s, we obtained x-ray diffraction data for two variants in the P450PMO (propane monooxygenase) lineage and a preliminary structure for the most evolved variant. This structure shows changes in the substrate binding regions of the enzyme and a reduction in active site volume that are consistent with the observed changes in substrate specificity from fatty acids in the native enzyme to small alkanes in P450PMO. We also constructed semi-rational designed libraries mutating only residues in the enzyme active site that in one round of mutagenesis and screening produced variants that achieved nearly half of the activity of the most evolved enzymes of the P450PMO lineage. Finally, we found that changes in redox properties of the laboratory-evolved P450 alkane hydroxylases did not reflect the improvement in their electron transfer efficiency. The heme redox potential remained constant throughout evolution, while activity increased and coupling efficiency improved from 10% to 90%. The lack of correlation between heme redox potential and enzyme activity and coupling efficiency led us to search for other enzyme properties that could be better predictors for activity towards small alkanes, specifically methane. We investigated the oxidation potential of the radical

Aggregate formation of eosin-Y adsorbed on nanocrystalline TiO2 films

Science.gov (United States)

Yaguchi, Kaori; Furube, Akihiro; Katoh, Ryuzi

2012-11-01

We have studied the adsorption of eosin-Y on nanocrystalline TiO2 films with two different solvents namely acetonitrile (ACN) and ethanol (EtOH). A Langmuir-type adsorption isotherm was observed with ACN. In contrast, a Freundlich-type adsorption isotherm was observed with EtOH, suggesting that EtOH molecules co-adsorbed on TiO2 surface. Absorption spectra of the dye adsorbed films clearly show aggregate formation at high concentrations of dye in the solutions. From the analysis of the spectra, we conclude that head-to-tail type aggregates are observed with ACN, whereas various types of aggregates, including H-type and head-to-tail type aggregates, are observed with EtOH.

The effect of environmental factors on stable isotopic composition of n-alkanes in Mediterranean olive oils

Science.gov (United States)

Pedentchouk, Nikolai; Mihailova, Alina; Abbado, Dimitri

2014-05-01

Traceability of the geographic origin of olive oils is an important issue from both commercial and health perspectives. This study evaluates the impact of environmental factors on stable C and H isotope compositions of n-alkanes in extra virgin olive oils from Croatia, France, Greece, Italy, Morocco, Portugal, Slovenia, and Spain. The data are used to investigate the applicability of stable isotope methodology for olive oil regional classification in the Mediterranean region. Analysis of stable C isotope composition of n-C29 alkane showed that extra virgin olive oils from Portugal and Spain have the most positive n-C29 alkane delta13C values. Conversely, olive oils from Slovenia, northern and central Italy are characterized by the most negative values. Overall, the n-C29 alkane delta13C values show a positive correlation with the mean air temperature during August-December and a negative correlation with the mean relative humidity during these months. Analysis of stable H isotope composition of n-C29 alkane revealed that the deltaD values are the most positive in olive oils from Greece and Morocco and the most negative in oils from northern Italy. The deltaD values of oils show significant correlation with all the analyses geographical parameters: the mean air temperature and relative humidity during August-December, the total amount of rainfall (the same months) and the annual deltaD values of precipitation. As predictor variables in the Categorical Data Analysis, the n-C29 alkane deltaD values show the most significant discriminative power, followed by the n-C29 alkane delta13C values. Overall, 93.4% of olive oil samples have been classified correctly into one of the production regions. Our findings suggest that an integrated analysis of C and H isotope compositions of n-alkanes extracted from extra virgin olive oil could become a useful tool for geographical provenancing of this highly popular food commodity.

Characterization and Two-Dimensional Crystallization of Membrane Component AlkB of the Medium-Chain Alkane Hydroxylase System from Pseudomonas putida GPo1

OpenAIRE

Alonso, Hernan; Roujeinikova, Anna

2012-01-01

The alkane hydroxylase system of Pseudomonas putida GPo1 allows it to use alkanes as the sole source of carbon and energy. Bacterial alkane hydroxylases have tremendous potential as biocatalysts for the stereo- and regioselective transformation of a wide range of chemically inert unreactive alkanes into valuable reactive chemical precursors. We have produced and characterized the first 2-dimensional crystals of the integral membrane component of the P. putida alkane hydroxylase system, the no...

Hydrogenation and hydrodeoxygenation of biomass-derived oxygenates to liquid alkanes for transportation fuels

Directory of Open Access Journals (Sweden)

Shaohui Sun

2018-04-01

Full Text Available An attractive approach for the production of transportation fuels from renewable biomass resources is to convert oxygenates into alkanes. In this paper, C5–C20 alkanes formed via the hydrogenation and hydrodeoxygenation of the oligomers of furfuryl alcohol(FA can be used as gasoline, diesel and jet fuel fraction. The first step of the process is the oligomers of FA convert into hydrogenated products over Raney Ni catalyst in a batch reactor. The second step of the process converts hydrogenated products to alkanes via hydrodeoxygenation over different bi-functional catalysts include hydrogenation and acidic deoxidization active sites. After this process, the oxygen content decreased from 22.1 wt% in the oligomers of FA to 0.58 wt% in the hydrodeoxygenation products.

A Novel Nanohybrid Nanofibrous Adsorbent for Water Purification from Dye Pollutants.

Science.gov (United States)

Homaeigohar, Shahin; Zillohu, Ahnaf Usman; Abdelaziz, Ramzy; Hedayati, Mehdi Keshavarz; Elbahri, Mady

2016-10-19

In this study, we devised a novel nanofibrous adsorbent made of polyethersulfone (PES) for removal of methylene blue (MB) dye pollutant from water. The polymer shows a low isoelectric point thus at elevated pHs and, being nanofibrous, can offer a huge highly hydroxylated surface area for adsorption of cationic MB molecules. As an extra challenge, to augment the adsorbent's properties in terms of adsorption capacity in neutral and acidic conditions and thermal stability, vanadium pentoxide (V₂O₅) nanoparticles were added to the nanofibers. Adsorption data were analyzed according to the Freundlich adsorption model. The thermodynamic parameters verified that only at basic pH is the adsorption spontaneous and in general the process is entropy-driven and endothermic. The kinetics of the adsorption process was evaluated by the pseudo-first- and pseudo-second-order models. The latter model exhibited the highest correlation with data. In sum, the adsorbent showed a promising potential for dye removal from industrial dyeing wastewater systems, especially when envisaging their alkaline and hot conditions.

Effects of surfactants on bacteria and the bacterial degradation of alkanes in crude oil

Energy Technology Data Exchange (ETDEWEB)

Bruheim, Per

1998-12-31

This thesis investigates the effects of surfactants on the bacterial degradation of alkanes in crude oil. Several alkane oxidising Gram positive and Gram negative were tested for their abilities to oxidise alkanes in crude oil emulsified with surfactants. The surfactants used to make the oil in water emulsions were either of microbial or chemical origin. Oxidation rates of resting bacteria oxidising various crude oil in water emulsions were measured by Warburg respirometry. The emulsions were compared with non-emulsified oil to see which was the preferred substrate. The bacteria were pregrown to both the exponential and stationary phase of growth before harvesting and preparation for the Warburg experiments. 123 refs., 4 figs., 14 tabs.

40 CFR 721.10163 - Chloro fluoro alkane (generic).

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Chloro fluoro alkane (generic). 721.10163 Section 721.10163 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC...)(2) of this section. (2) The significant new uses are: (i) Industrial, commercial, and consumer...

The (gas + liquid) critical properties and phase behaviour of some binary alkanol (C2-C5) + alkane (C5-C12) mixtures

International Nuclear Information System (INIS)

Morton, David W.; Lui, Matthew P.W.; Young, Colin L.

2003-01-01

Previously, the investigation of the (gas + liquid) critical properties of (alkanol + alkane) mixtures has focussed on (primary alkanol + straight chain alkane) mixtures. The experimental data available for (alkanol + alkane) mixtures, which include secondary or tertiary alcohols and/or branched chain alkanes, are extremely limited. This work extends the existing body of data on (alkanol + alkane) mixtures to include mixtures containing these components. Here the (gas + liquid) critical temperatures of 29 {alkanol (C 2 -C 5 ) + alkane (C 5 -C 12 )} mixtures are reported. All the (gas + liquid) critical lines for the binary mixtures studied are continuous, indicating they obey either Type I or Type II phase behaviour

Diversity of alkane degrading bacteria associated with plants in a petroleum oil-contaminated environment and expression of alkane monooxygenase (alkB) genes

Science.gov (United States)

Andria, V.; Yousaf, S.; Reichenauer, T. G.; Smalla, K.; Sessitsch, A.

2009-04-01

Among twenty-six different plant species, Italian ryegrass (Lolium multiflorum var. Taurus), Birdsfoot trefoil (Lotus corniculatus var. Leo), and the combination of both plants performed well in a petroleum oil contaminated soil. Hydrocarbon degrading bacteria were isolated from the rhizosphere, root interior and shoot interior and subjected to the analysis of 16S rRNA, the 16S and 23S rRNA intergenic spacer region and alkane hydroxylase genes. Higher numbers of culturable, degrading bacteria were associated with Italian ryegrass, which were also characterized by a higher diversity, particularly in the plant interior. Only half of the isolated bacteria hosted known alkane hydroxylase genes (alkB and cytochrome P153-like). Our results indicated that alkB genes have spread through horizontal gene transfer, particularly in the Italian ryegrass rhizosphere, and suggested mobility of catabolic genes between Gram-negative and Gram-positive bacteria. We furthermore studied the colonization behaviour of selected hydrocarbon-degrading strains (comprising an endopyhte and a rhizosphere strain) as well as the expression of their alkane monooxygenase genes in association with Italian ryegrass. Results showed that the endophyte strain better colonized the plant, particularly the plant interior, and also showed higher expression of alkB genes suggesting a more efficient degradation of the pollutant. Furthermore, plants inoculated with the endophyte were better able to grow in the presence of diesel. The rhizosphere strain colonized primarily the rhizosphere and showed low alkB gene expression in the plant interior.

n-Alkanes in sediments from the Yellow River Estuary, China: Occurrence, sources and historical sedimentary record.

Science.gov (United States)

Wang, Shanshan; Liu, Guijian; Yuan, Zijiao; Da, Chunnian

2018-04-15

A total of 21 surface sediments from the Yellow River Estuary (YRE) and a sediment core from the abandoned Old Yellow River Estuary (OYRE) were analyzed for n-alkanes using gas chromatography-mass spectrometry (GC-MS). n-Alkanes in the range C 12 -C 33 and C 13 -C 34 were identified in the surface sediments and the core, respectively. The homologous series were mainly bimodal distribution pattern without odd/even predominance in the YRE and OYRE. The total n-alkanes concentrations in the surface sediments ranged from 0.356 to 0.572mg/kg, with a mean of 0.434mg/kg on dry wt. Evaluation of n-alkanes proxies indicated that the aliphatic hydrocarbons in the surface sediments were derived mainly from a petrogenic source with a relatively low contribution of submerged/floating macrophytes, terrestrial and emergent plants. The dated core covered the time period 1925-2012 and the mean sedimentation rate was ca. 0.5cm/yr. The total n-alkanes concentrations in the core ranged from 0.0394 to 0.941mg/kg, with a mean of 0.180mg/kg. The temporal evolution of n-alkanes reflected the historical input of aliphatic hydrocarbons and was consistent with local and regional anthropogenic activity. In general, the investigation on the sediment core revealed a trend of regional environmental change and the role of anthropogenic activity in environmental change. Copyright © 2017 Elsevier Inc. All rights reserved.

Bidirectional gene sequences with similar homology to functional proteins of alkane degrading bacterium pseudomonas fredriksbergensis DNA

International Nuclear Information System (INIS)

Megeed, A.A.

2011-01-01

The potential for two overlapping fragments of DNA from a clone of newly isolated alkanes degrading bacterium Pseudomonas frederiksbergensis encoding sequences with similar homology to two parts of functional proteins is described. One strand contains a sequence with high homology to alkanes monooxygenase (alkB), a member of the alkanes hydroxylase family, and the other strand contains a sequence with some homology to alcohol dehydrogenase gene (alkJ). Overlapping of the genes on opposite strands has been reported in eukaryotic species, and is now reported in a bacterial species. The sequence comparisons and ORFS results revealed that the regulation and the genes organization involved in alkane oxidation represented in Pseudomonas frederiksberghensis varies among the different known alkane degrading bacteria. The alk gene cluster containing homologues to the known alkane monooxygenase (alkB), and rubredoxin (alkG) are oriented in the same direction, whereas alcohol dehydrogenase (alkJ) is oriented in the opposite direction. Such genomes encode messages on both strands of the DNA, or in an overlapping but different reading frames, of the same strand of DNA. The possibility of creating novel genes from pre-existing sequences, known as overprinting, which is a widespread phenomenon in small viruses. Here, the origin and evolution of the gene overlap to bacteriophages belonging to the family Microviridae have been investigated. Such a phenomenon is most widely described in extremely small genomes such as those of viruses or small plasmids, yet here is a unique phenomenon. (author)

LEED crystallography studies of the structure of clean and adsorbate-covered Ir, Pt and Rh crystal surfaces

International Nuclear Information System (INIS)

Koestner, R.J.

1982-08-01

There have only been a few Low Energy Electron Diffraction (LEED) intensity analyses carried out to determine the structure of molecules adsorbed on metal surfaces; most surface crystallography studies concentrated on the structure of clean unreconstructed or atomic adsorbate-covered transition metal faces. The few molecular adsorption systems already investigated by dynamical LEED are CO on Ni(100), Cu(100) and Pd(100) as well as C 2 H 2 and C 2 H 4 adsorbed on Pt(111). The emphasis of this thesis research has been to extend the applicability of LEED crystallography to the more complicated unit cells found in molecular overlayers on transition metals or in there constructed surfaces of clean transition metals

Solid acid catalysts in heterogeneous n-alkanes hydroisomerisation ...

African Journals Online (AJOL)

As the current global environmental concerns have prompted regulations to reduce the level of aromatic compounds, particularly benzene and its derivatives in gasoline, ydroisomerisation of n-alkanes is becoming a major alternative for enhancing octane number. Series of solid acid catalysts comprising of Freidel crafts, ...

The growth and electronic structure of azobenzene-based functional molecules on layered crystals

International Nuclear Information System (INIS)

Iwicki, J; Ludwig, E; Buck, J; Kalläne, M; Kipp, L; Rossnagel, K; Köhler, F; Herges, R

2012-01-01

In situ ultraviolet photoelectron spectroscopy is used to study the growth of ultrathin films of azobenzene-based functional molecules (azobenzene, Disperse Orange 3 and a triazatriangulenium platform with an attached functional azo-group) on the layered metal TiTe 2 and on the layered semiconductor HfS 2 at liquid nitrogen temperatures. Effects of intermolecular interactions, of the substrate electronic structure, and of the thermal energy of the sublimated molecules on the growth process and on the adsorbate electronic structure are identified and discussed. A weak adsorbate-substrate interaction is particularly observed for the layered semiconducting substrate, holding the promise of efficient molecular photoswitching.

Surface chemical reactions induced by molecules electronically-excited in the gas

DEFF Research Database (Denmark)

Petrunin, Victor V.

2011-01-01

and alignment are taking place, guiding all the molecules towards the intersections with the ground state PES, where transitions to the ground state PES will occur with minimum energy dissipation. The accumulated kinetic energy may be used to overcome the chemical reaction barrier. While recombination chemical...... be readily produced. Products of chemical adsorption and/or chemical reactions induced within adsorbates are aggregated on the surface and observed by light scattering. We will demonstrate how pressure and spectral dependencies of the chemical outcomes, polarization of the light and interference of two laser...... beams inducing the reaction can be used to distinguish the new process we try to investigate from chemical reactions induced by photoexcitation within adsorbed molecules and/or gas phase photolysis....

Sulfur removal from fuel using zeolites/polyimide mixed matrix membrane adsorbents

International Nuclear Information System (INIS)

Lin, Ligang; Wang, Andong; Dong, Meimei; Zhang, Yuzhong; He, Benqiao; Li, Hong

2012-01-01

Graphical abstract: Membrane adsorption process is proposed for sulfur removal. Three-dimensional network structure is key to fulfill adsorption function of MMMs, which adsorption/desorption behavior is markedly related with binding force with sulfur molecules. Highlights: ► Membrane adsorption process is proposed for sulfur removal. ► Three-dimensional network structure of MMMs is key to fulfill adsorption function. ► Adsorption/desorption behavior is markedly related with binding force. - Abstract: A novel membrane adsorption process was proposed for the sulfur removal from fuels. The mixed matrix membranes (MMMs) adsorbents composed of polyimide (PI) and various Y zeolites were prepared. By the detailed characterization of FT-IR, morphology, thermal and mechanical properties of MMMs adsorbents, combining the adsorption and desorption behavior research, the process–structure–function relationship was discussed. Field-emission scanning electron microscope (FESEM) images show that the functional particles are incorporated into the three-dimensional network structure. MMMs adsorbents with 40% of zeolites content possess better physical properties, which was confirmed by mechanical strength and thermo stability analysis. Influence factors including post-treatment, content of incorporated zeolites, adsorption time, temperature, initial sulfur concentration as well as sulfur species on the adsorption performance of MMMs adsorbents have been evaluated. At 4 wt.% zeolites content, adsorption capacity for NaY/PI, AgY/PI and CeY/PI MMMs adsorbents come to 2.0, 7.5 and 7.9 mg S/g, respectively. And the regeneration results suggest that the corresponding spent membranes can recover about 98%, 90% and 70% of the desulfurization capacity, respectively. The distinct adsorption and desorption behavior of MMMs adsorbents with various functional zeolites was markedly related with their various binding force and binding mode with sulfur compounds.

n-Alkane distributions as indicators of novel ecosystem development in western boreal forest soils

Science.gov (United States)

Norris, Charlotte; Dungait, Jennifer; Quideau, Sylvie

2013-04-01

Novel ecosystem development is occurring within the western boreal forest of Canada due to land reclamation following surface mining in the Athabasca Oil Sands Region. Sphagnum peat is the primary organic matter amendment used to reconstruct soils in the novel ecosystems. We hypothesised that ecosystem recovery would be indicated by an increasing similarity in the biomolecular characteristics of novel reconstructed soil organic matter (SOM) derived from peat to those of natural boreal ecosystems. In this study, we evaluated the use of the homologous series of very long chain (>C20) n-alkanes with odd-over-even predominance as biomarker signatures to monitor the re-establishment of boreal forests on reconstructed soils. The lipids were extracted from dominant vegetation inputs and SOM from a series of natural and novel ecosystem reference plots. We observed unique very long n-alkane signatures of the source vegetation, e.g. Sphagnum sp. was dominated by C31 and aspen (Populus tremuloides Michx.) leaves by C25. Greater concentrations of very long chain n-alkanes were extracted from natural than novel ecosystem SOM (puse of n-alkanes as biomarkers of ecosystem development is a promising method.

Complete braided adsorbent for marine testing to demonstrate 3g-U/kg-adsorbent

Energy Technology Data Exchange (ETDEWEB)

Janke, Chris [ORNL; Yatsandra, Oyola [ORNL; Mayes, Richard [ORNL; none,; Gill, Gary [PNNL; Li-Jung, Kuo [PNNL; Wood, Jordana [PNNL; Sadananda, Das [ORNL

2014-04-30

ORNL has manufactured four braided adsorbents that successfully demonstrated uranium adsorption capacities ranging from 3.0-3.6 g-U/kg-adsorbent in marine testing at PNNL. Four new braided and leno woven fabric adsorbents have also been prepared by ORNL and are currently undergoing marine testing at PNNL.

Adsorption behavior of Co anchored on graphene sheets toward NO, SO2, NH3, CO and HCN molecules

International Nuclear Information System (INIS)

Tang, Yanan; Chen, Weiguang; Li, Chenggang; Pan, Lijun; Dai, Xianqi; Ma, Dongwei

2015-01-01

Graphical abstract: - Highlights: • In contrast to the pristine graphene, a vacancy defect in graphene strongly stabilizes the Co atom. • The positively charged of Co atom on graphene can regulate the stability of gas molecules. • Different gas molecules can modulate the electronic structure of Co–graphene systems. • The adsorbed NO on Co–graphene can effectively regulate the magnetic properties of systems. - Abstract: Based on the first-principles of density-functional theory (DFT), the effects of gas adsorption on the change in geometric stability, electronic structure and magnetic properties of graphene with anchored Co (Co–graphene) systems were investigated. A single Co adatom interacts much weaker with pristine graphene (Co/pri–graphene) than with the graphene containing a single vacancy (Co/SV–graphene). The Co dopant provides more electrons to the dangling bonds of carbon atom at defective site and exhibits more positive charges, which makes Co/SV–graphene less prone to be adsorbed by gas molecules in comparison to Co/pri–graphene. It is found that the electronic structure and magnetic properties of Co–graphene systems can be modulated by adsorbing gas molecules. Except the NH 3 molecule, the adsorbed NO, SO 2 , CO or HCN as electron acceptors on the Co/pri–graphene can exhibit semiconducting properties. Among the gas molecules, the strong adsorption of NO molecule can effectively regulate the magnetic properties of Co–graphene systems. Moreover, the stable configuration of Co/SV–graphene is more likely to be the gas sensor for detecting NO and SO 2 . The results validate that the reactivity of atomic-scale catalyst is supported on graphene sheets, which is expected to be potentially efficient in the gas sensors and electronic device

Oxidation of monovacancies in graphene by oxygen molecules

KAUST Repository

Kaloni, Thaneshwor P.; Cheng, Yingchun; Faccio, R.; Schwingenschlö gl, Udo

2011-01-01

We study the oxidation of monovacancies in graphene by oxygen molecules using first principles calculations. In particular, we address the local magnetic moments which develop at monovacancies and show that they remain intact when a molecule is adsorbed such that the dangling carbon bonds are not fully saturated. However, the lowest energy configuration does not maintain dangling bonds and is found to be semiconducting. Our data can explain the experimentally observed behavior of graphene under exposure to an oxygen plasma.

Oxidation of monovacancies in graphene by oxygen molecules

KAUST Repository

Kaloni, Thaneshwor P.

2011-10-14

We study the oxidation of monovacancies in graphene by oxygen molecules using first principles calculations. In particular, we address the local magnetic moments which develop at monovacancies and show that they remain intact when a molecule is adsorbed such that the dangling carbon bonds are not fully saturated. However, the lowest energy configuration does not maintain dangling bonds and is found to be semiconducting. Our data can explain the experimentally observed behavior of graphene under exposure to an oxygen plasma.

n-Alkanes in surficial sediments of Visakhapatnam harbour, east coast of India

Digital Repository Service at National Institute of Oceanography (India)

Punyu, V.R.; Harji, R.R.; Bhosle, N.B.; Sawant, S.S.; Venkat, K.

-alkanes mainly at C15, C17 and C19 Keywords. Sediments; lipids; n-alkanes; Visakhapatnam harbour. J. Earth Syst. Sci. 122, No. 2, April 2013, pp. 467–477 c© Indian Academy of Sciences 467 468 V R Punyu et al while terrestrial plants exhibit predominance of long... steel plant, a fertilizer plant and a lead and zinc smelter in the vicinity are discharged into this harbour. The harbour handles items such as man- ganese and iron ore, coal and oil products. Added to this, it receives most of the urban run...

Thermodynamic parameters for the adsorption of volatile n-alkane ...

African Journals Online (AJOL)

alkanes hexane to nonane on ground dried water hyacinth (E. crassipes) root biomass were studied between 40 and 70°C column temperature using inverse gas chromatography, before and after treatment of the root biomass with mineral acid ...

Distribution and sources of n-alkanes and polycyclic aromatic hydrocarbons in shellfish of the Egyptian Red Sea coast

Directory of Open Access Journals (Sweden)

Ahmed El Nemr

2016-06-01

Full Text Available Aromatic hydrocarbons and n-alkanes were analyzed in shellfish collected from 13 different sites along the Egyptian Red Sea coast. All samples were analyzed for n-alkanes (C8–C40 and polycyclic aromatic hydrocarbons (EPA list of PAHs. n-Alkanes in shellfish samples from 13 locations were found to be in the range of 71.0–701.1 ng/g with a mean value of 242.2 ± 192.1 ng/g dry wt. Different indices were calculated for the n-alkanes to assess their sources. These were carbon preference index (CPI, average chain length (ACL, terrigenous/aquatic ratio (TAR, natural n-alkane ratio (NAR and proxy ratio (Paq. Most of the collected samples of n-alkanes were discovered to be from natural sources. Aromatic hydrocarbons (16 PAHs from 13 sites varied between 1.3 and 160.9 ng/g with an average of 47.9 ± 45.5 ng/g dry wt. Benzo(apyrine (BaP, a cancer risk assessment, was calculated for the PAHs and resulted in ranges between 0.08 and 4.47 with an average of 1.25 ng/g dry wt.

Evaluation of n-alkanes and their carbon isotope enrichments (d13C) as diet composition markers

NARCIS (Netherlands)

Derseh, M.B.; Pellikaan, W.F.; Tolera, A.; Hendriks, W.H.

2011-01-01

Plant cuticular n-alkanes have been successfully used as markers to estimate diet composition and intake of grazing herbivores. However, additional markers may be required under grazing conditions in botanically diverse vegetation. This study was conducted to describe the n-alkane profiles and the

Stable isotope labeled n-alkanes to assess digesta passage kinetics through the digestive tract of ruminants

NARCIS (Netherlands)

Warner, D.; Ferreira, L.M.M.; Breuer, M.J.H.; Dijkstra, J.; Pellikaan, W.F.

2013-01-01

We describe the use of carbon stable isotope (13C) labeled n-alkanes as a potential internal tracer to assess passage kinetics of ingested nutrients in ruminants. Plant cuticular n-alkanes originating from intrinsically 13C labeled ryegrass plants were pulse dosed intraruminally in four

Shale gas opportunities. Dehydrogenation of light alkanes

Energy Technology Data Exchange (ETDEWEB)

Patcas, F.C.; Dieterle, M.; Rezai, A.; Asprion, N. [BASF SE, Ludwigshafen (Germany)

2013-11-01

The discovery and use of shale gas in North America has become a game changer for the chemical industry by access to a cheaper feedstock compared to conventional oil. Increased number of ethane crackers spurred increasing interest in light alkanes dehydrogenation. Several companies have announced their interest in new propane dehydrogenation units in North America. BASF is developing light alkanes dehydrogenation technologies for two decades now. BASF developed jointly with Linde the isothermal C3 dehydrogenation process. The latest dehydrogenation catalyst development at BASF focused on a supported and steam resistant Pt-Sn catalyst which yielded excellent selectivity and activity. Intense research work both internally as well as in cooperation with universities contributed to the understanding of the relationship between the surface structure and catalyst performances like activity, selectivity and coking resistance. Using such type of catalysts BASF developed an autothermal propane dehydrogenation as well as a butane dehydrogenation process. The most recent catalyst development was a dehydrogenation catalyst coated on a honeycomb monolith to improve catalyst usage and pressure drop. This will probably be the first industrial usage of catalytic monoliths in a chemical synthesis process. (orig.) (Published in summary form only)

The Calculation of Standard Enthalpies of Formation of Alkanes: Illustrating Molecular Mechanics and Spreadsheet Programs

Science.gov (United States)

Hawk, Eric Leigh

1999-02-01

How group increment methods may be used to predict standard enthalpies of formation of alkanes is outlined as an undergraduate computational chemistry experiment. The experiment requires input and output data sets. Although users may create their own data sets, both sets are provided. The input data set contains experimentally determined gas-phase standard enthalpies of formation and calculated steric energies for 10 alkanes. The steric energy for an alkane is calculated via a Molecular Mechanics approach employing Allinger's MM3 force field. Linear regression analysis on data contained in the input data set generates the coefficients that are used with the output data set to calculate standard enthalpies of formation for 15 alkanes. The average absolute error for the calculated standard enthalpies of formation is 1.22 kcal/mol. The experiment is highly suited to those interested in incorporating more computational chemistry in their curricula. In this regard, it is ideally suited for a physical chemistry laboratory, but it may be used in an organic chemistry course as well.

Orientational epitaxy in adsorbed monolayers

International Nuclear Information System (INIS)

Novaco, A.D.; McTague, J.P.

1977-01-01

The ground state for adsorbed monolayers on crystalline substrates is shown to involve a definite relative orientation of the substrate and adsorbate crystal axes, even when the relative lattice parameters are incommensurate. The rotation angle which defines the structure of the monolayer-substrate system is determined by the competition between adsorbate-substrate and adsorbate-adsorbate energy terms, and is generally not a symmetry angle. Numerical predictions are presented for the rare gas-graphite systems, whose interaction potentials are rather well known. Recent LEED data for some of these systems appear to corroborate these predictions

LEED crystallography studies of the structure of clean and adsorbate-covered Ir, Pt and Rh crystal surfaces

Energy Technology Data Exchange (ETDEWEB)

Koestner, R.J.

1982-08-01

There have only been a few Low Energy Electron Diffraction (LEED) intensity analyses carried out to determine the structure of molecules adsorbed on metal surfaces; most surface crystallography studies concentrated on the structure of clean unreconstructed or atomic adsorbate-covered transition metal faces. The few molecular adsorption systems already investigated by dynamical LEED are CO on Ni(100), Cu(100) and Pd(100) as well as C/sub 2/H/sub 2/ and C/sub 2/H/sub 4/ adsorbed on Pt(111). The emphasis of this thesis research has been to extend the applicability of LEED crystallography to the more complicated unit cells found in molecular overlayers on transition metals or in there constructed surfaces of clean transition metals.

Ultrafast electron dynamics at alkali/ice structures adsorbed on a metal surface

International Nuclear Information System (INIS)

Meyer, Michael

2011-01-01

The goal of this work is to study the interaction between excess electrons in water ice structures adsorbed on metal surfaces and other charged or neutral species, like alkali ions, or chemically reactive molecules, like chlorofluorocarbons (CFC), respectively. The excess electrons in the ice can interact with the ions directly or indirectly via the hydrogen bonded water molecules. In both cases the presence of the alkali influences the population, localization, and lifetime of electronic states of excess electrons in the ice adlayer. These properties are of great relevance when considering the highly reactive character of the excess electrons, which can mediate chemical reactions by dissociative electron attachment (DEA). The influence of alkali adsorption on electron solvation and transfer dynamics in ice structures is investigated for two types of adsorption configurations using femtosecond time-resolved two-photon photoelectron spectroscopy. In the first system alkali atoms are coadsorbed on top of a wetting amorphous ice film adsorbed on Cu(111). At temperatures between 60 and 100 K alkali adsorption leads to the formation of positively charged alkali ions at the ice/vacuum interface. The interaction between the alkali ions at the surface and the dipole moments of the surrounding water molecules results in a reorientation of the water molecules. As a consequence new electron trapping sites, i.e. at local potential minima, are formed. Photoinjection of excess electrons into these alkali-ion covered amorphous ice layers, results in the trapping of a solvated electron at an alkali-ion/water complex. In contrast to solvation in pure amorphous ice films, where the electrons are located in the bulk of the ice layer, solvated electrons at alkali-ion/water complexes are located at the ice/vacuum interface. They exhibit lifetimes of several picoseconds and show a fast energetic stabilization. With ongoing solvation, i.e. pump-probe time delay, the electron transfer is

Arbuscular mycorrhizal wheat inoculation promotes alkane and polycyclic aromatic hydrocarbon biodegradation: Microcosm experiment on aged-contaminated soil

International Nuclear Information System (INIS)

Ingrid, Lenoir; Lounès-Hadj Sahraoui, Anissa; Frédéric, Laruelle; Yolande, Dalpé; Joël, Fontaine

2016-01-01

Very few studies reported the potential of arbuscular mycorrhizal symbiosis to dissipate hydrocarbons in aged polluted soils. The present work aims to study the efficiency of arbuscular mycorrhizal colonized wheat plants in the dissipation of alkanes and polycyclic aromatic hydrocarbons (PAHs). Our results demonstrated that the inoculation of wheat with Rhizophagus irregularis allowed a better dissipation of PAHs and alkanes after 16 weeks of culture by comparison to non-inoculated condition. These dissipations observed in the inoculated soil resulted from several processes: (i) a light adsorption on roots (0.5% for PAHs), (ii) a bioaccumulation in roots (5.7% for PAHs and 6.6% for alkanes), (iii) a transfer in shoots (0.4 for PAHs and 0.5% for alkanes) and mainly a biodegradation. Whereas PAHs and alkanes degradation rates were respectively estimated to 12 and 47% with non-inoculated wheat, their degradation rates reached 18 and 48% with inoculated wheat. The mycorrhizal inoculation induced an increase of Gram-positive and Gram-negative bacteria by 56 and 37% compared to the non-inoculated wheat. Moreover, an increase of peroxidase activity was assessed in mycorrhizal roots. Taken together, our findings suggested that mycorrhization led to a better hydrocarbon biodegradation in the aged-contaminated soil thanks to a stimulation of telluric bacteria and hydrocarbon metabolization in mycorrhizal roots. - Highlights: • Phytoremediation of aged-hydrocarbon polluted soils may be improved using arbuscular mycorrhizal fungi. • Inoculation of wheat with R. irregularis improved dissipation of PAH and alkanes. • Dissipation resulted from adsorption and bioaccumulation in wheat and mainly from biodegradation in soil. • Biodegradation was due to a stimulation of rhizosphere bacteria and an induction of root peroxidase. - Inoculation of wheat by an arbuscular mycorrhizal fungus improves biodegradation of alkanes and polycyclic aromatic hydrocarbons in an aged

Clay minerals and metal oxides strongly influence the structure of alkane-degrading microbial communities during soil maturation.

Science.gov (United States)

Steinbach, Annelie; Schulz, Stefanie; Giebler, Julia; Schulz, Stephan; Pronk, Geertje J; Kögel-Knabner, Ingrid; Harms, Hauke; Wick, Lukas Y; Schloter, Michael

2015-07-01

Clay minerals, charcoal and metal oxides are essential parts of the soil matrix and strongly influence the formation of biogeochemical interfaces in soil. We investigated the role of these parental materials for the development of functional microbial guilds using the example of alkane-degrading bacteria harbouring the alkane monooxygenase gene (alkB) in artificial mixtures composed of different minerals and charcoal, sterile manure and a microbial inoculum extracted from an agricultural soil. We followed changes in abundance and community structure of alkane-degrading microbial communities after 3 and 12 months of soil maturation and in response to a subsequent 2-week plant litter addition. During maturation we observed an overall increasing divergence in community composition. The impact of metal oxides on alkane-degrading community structure increased during soil maturation, whereas the charcoal impact decreased from 3 to 12 months. Among the clay minerals illite influenced the community structure of alkB-harbouring bacteria significantly, but not montmorillonite. The litter application induced strong community shifts in soils, maturated for 12 months, towards functional guilds typical for younger maturation stages pointing to a resilience of the alkane-degradation function potentially fostered by an extant 'seed bank'.

Theoretical study of n-alkane adsorption on metal surfaces

DEFF Research Database (Denmark)

Morikawa, Yoshitada; Ishii, Hisao; Seki, Kazuhiko

2004-01-01

The interaction between n-alkane and metal surfaces has been studied by means of density-functional theoretical calculations within a generalized gradient approximation (GGA). We demonstrate that although the GGA cannot reproduce the physisorption energy well, our calculations can reproduce the e...

Flash Points of Secondary Alcohol and n-Alkane Mixtures.

Science.gov (United States)

Esina, Zoya N; Miroshnikov, Alexander M; Korchuganova, Margarita R

2015-11-19

The flash point is one of the most important characteristics used to assess the ignition hazard of mixtures of flammable liquids. To determine the flash points of mixtures of secondary alcohols with n-alkanes, it is necessary to calculate the activity coefficients. In this paper, we use a model that allows us to obtain enthalpy of fusion and enthalpy of vaporization data of the pure components to calculate the liquid-solid equilibrium (LSE) and vapor-liquid equilibrium (VLE). Enthalpy of fusion and enthalpy of vaporization data of secondary alcohols in the literature are limited; thus, the prediction of these characteristics was performed using the method of thermodynamic similarity. Additionally, the empirical models provided the critical temperatures and boiling temperatures of the secondary alcohols. The modeled melting enthalpy and enthalpy of vaporization as well as the calculated LSE and VLE flash points were determined for the secondary alcohol and n-alkane mixtures.

Infrared spectroscopic and voltammetric study of adsorbed CO on stepped surfaces of copper monocrystalline electrodes

International Nuclear Information System (INIS)

Koga, O.; Teruya, S.; Matsuda, K.; Minami, M.; Hoshi, N.; Hori, Y.

2005-01-01

Voltammetric and infrared (IR) spectroscopic measurements were carried out to study adsorbed CO on two series of copper single crystal electrodes n(111)-(111) and n(111)-(100) in 0.1M KH 2 PO 4 +0.1M K 2 HPO 4 at 0 o C. Reversible voltammetric waves were observed below -0.55V versus SHE for adsorption of CO which displaces preadsorbed phosphate anions. The electric charge of the redox waves is proportional to the step atom density for both single crystal series. This fact indicates that phosphate anions are specifically adsorbed on the step sites below -0.55V versus SHE. Voltammetric measurements indicated that (111) terrace of Cu is covered with adsorbed CO below -0.5V versus SHE. Nevertheless, no IR absorption band of adsorbed CO is detected from (111) terrace. Presence of adsorbed CO on (111) terrace is presumed which is not visible by the potential difference spectroscopy used in the present work. IR spectroscopic measurements showed that CO is reversibly adsorbed with an on-top manner on copper single crystal electrodes of n(111)-(111) and n(111)-(100) with approximately same wavenumber of C?O stretching vibration of 2070cm -1 . The IR band intensity is proportional to the step atom density. Thus CO is adsorbed on (111) or (100) steps on the single crystal surfaces. An analysis of the IR band intensity suggested that one CO molecule is adsorbed on every two or more Cu step atom of the monocrystalline surface. The spectroscopic data were compared with those reported for uhv system. The C-O stretching wavenumber of adsorbed CO in the electrode-electrolyte system is 30-40cm -1 lower than those in uhv system

Microbial communities in methane- and short chain alkane-rich hydrothermal sediments of Guaymas Basin

Directory of Open Access Journals (Sweden)

Frederick eDowell

2016-01-01

Full Text Available The hydrothermal sediments of Guaymas Basin, an active spreading center in the Gulf of California (Mexico, are rich in porewater methane, short-chain alkanes, sulfate and sulfide, and provide a model system to explore habitat preferences of microorganisms, including sulfate-dependent, methane- and short chain alkane-oxidizing microbial communities. In this study, sediments (above 60˚C covered with sulfur-oxidizing microbial mats surrounding a hydrothermal mound (termed Mat Mound were characterized by porewater geochemistry of methane, C2-C6 short-chain alkanes, sulfate, sulfide, sulfate reduction rate measurements, in-situ temperature gradients, bacterial and archaeal 16S rRNA gene clone libraries and V6 tag pyrosequencing. The most abundantly detected groups in the Mat mound sediments include anaerobic methane-oxidizing archaea of the ANME-1 lineage and its sister clade ANME-1Guaymas, the uncultured bacterial groups SEEP-SRB2 within the Deltaproteobacteria and the separately branching HotSeep-1 Group; these uncultured bacteria are candidates for sulfate-reducing alkane oxidation and for sulfate-reducing syntrophy with ANME archaea. The archaeal dataset indicates distinct habitat preferences for ANME-1, ANME-1-Guaymas and ANME-2 archaea in Guaymas Basin hydrothermal sediments. The bacterial groups SEEP-SRB2 and HotSeep-1 co-occur with ANME-1 and ANME-1Guaymas in hydrothermally active sediments underneath microbial mats in Guaymas Basin. We propose the working hypothesis that this mixed bacterial and archaeal community catalyzes the oxidation of both methane and short-chain alkanes, and constitutes a microbial community signature that is characteristic for hydrothermal and/or cold seep sediments containing both substrates.

Constructing a proton titration curve from ion-step measurements, applied to a membrane with adsorbed protein

NARCIS (Netherlands)

Eijkel, Jan C.T.; Bosch, Coen; Olthuis, Wouter; Bergveld, Piet

1997-01-01

A new measuring method is described for obtaining a proton titration curve. The curve is obtained from a microporous composite membrane, consisting of polystyrene beads in an agarose matrix, with lysozyme molecules adsorbed to the bead surface. The membrane is incorporated into a sensor system by

Theoretical and experimental study of the vibrational excitations in ethane monolayers adsorbed on graphite (0001) surfaces

DEFF Research Database (Denmark)

Hansen, Flemming Yssing; Taub, H.

1987-01-01

The collective vibrational excitations of two different crystalline monolayer phases of ethane (C2H6) adsorbed on the graphite (0001) surface have been investigated theoretically and experimentally. The monolayer phases studied are the commensurate 7/8 ×4 structure in which the ethane molecules lie...

Structural, electronic, and magnetic properties of pristine and oxygen-adsorbed graphene nanoribbons

Energy Technology Data Exchange (ETDEWEB)

Miwa, R.H.; Veiga, R.G.A. [Instituto de Fisica, Universidade Federal de Uberlandia, Caixa Postal 593, CEP 38400-902, Uberlandia, MG (Brazil); Srivastava, G.P., E-mail: gps@excc.ex.ac.uk [School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)

2010-07-15

The structural, electronic and magnetic properties of pristine and oxygen-adsorbed (3,0) zigzag and (6,1) armchair graphene nanoribbons have been investigated theoretically, by employing the ab initio pseudopotential method within the density functional scheme. The zigzag nanoribbon is more stable with antiferromagnetically coupled edges, and is semiconducting. The armchair nanoribbon does not show any preference for magnetic ordering and is semiconducting. The oxygen molecule in its triplet state is adsorbed most stably at the edge of the zigzag nanoribbon. The Stoner metallic behaviour of the ferromagnetic nanoribbons and the Slater insulating (ground state) behaviour of the antiferromagnetic nanoribbons remain intact upon oxygen adsorption. However, the local magnetic moment of the edge carbon atom of the ferromagnetic zigzag ribbon is drastically reduced, due to the formation of a spin-paired C-O bond.

The adsorber loop concept for the contact between seawater and adsorber granulate

International Nuclear Information System (INIS)

Koske, P.H.; Ohlrogge, K.

1984-01-01

For the production of 1 kg uranium from seawater about 10 9 kg seawater - depending on the extraction efficiency - have to be processed in a production plant. Such high seawater flows have to be put through adsorber beds the area of which depends on the flow velocity of the water in the bed. For a typical polyamidoxim (PAO) adsorber granulate with a grain size distribution of 0.3 to 1.2 mm the velocity in a fluidized bed is limited to about 1 cm/s in order to prevent carry out of the adsorber material. The consequences of this rather low bed velocity are large and expensive bed areas for technical production plants. The present paper deals with the so-called ''adsorber loop concept'' in which the adsorber granulate is carried along with the seawater to be processed in a loop-like configuration and is separated again from the water before this is leaving the adsorption unit. This concept enables considerably higher seawater velocities thus reducing the bed area. Theoretical considerations are presented together with experimental results from field tests. (author)

Separation of benzene from alkanes by solvent extraction with 1-ethylpyridinium ethylsulfate ionic liquid

International Nuclear Information System (INIS)

Gomez, Elena; Dominguez, Irene; Calvar, Noelia; Dominguez, Angeles

2010-01-01

The (liquid + liquid) equilibrium (LLE) data for ternary mixtures {alkane + benzene + 1-ethylpyridinium ethylsulfate ([EPy][EtSO 4 ])} at T = (283.15 and 298.15) K and atmospheric pressure are presented. The alkanes used were hexane and heptane. The cloud point method was used to determinate the binodal curve, and the tie-line compositions were obtained by density measurements. The LLE data obtained were used to calculate distribution coefficients and selectivity values. The consistency of tie-line data was ascertained by applying the Othmer-Tobias and Hand equations. Correlation of the experimental tie-lines was conducted through the use of NRTL equation, which provides good correlation of the experimental data. The results show that [EPy][EtSO 4 ] can be used as an alternative solvent in liquid extraction processes for the removal of benzene from its mixtures with alkanes.

Laser-induced desorption of organic molecules from front- and back-irradiated metal foils

International Nuclear Information System (INIS)

Zinovev, Alexander V.; Veryovkin, Igor V.; Pellin, Michael J.

2009-01-01

Laser-Induced Acoustic Desorption (LIAD) from thin metal foils is a promising technique for gentle and efficient volatilization of intact organic molecules from surfaces of solid substrates. Using the Single Photon Ionization (SPI) method combined with time-of-flight mass-spectrometry (TOF MS), desorbed flux in LIAD was examined and compared to that from direct laser desorption (LD). Molecules of various organic dyes were used in experiments. Translational velocities of the desorbed intact molecules did not depend on the desorbing laser intensity, which implies the presence of more sophisticated mechanism of energy transfer than the direct mechanical or thermal coupling between the laser pulse and the adsorbed molecules. The results of our experiments indicate that the LIAD phenomenon cannot be described in terms of a simple mechanical shake-off nor the direct laser desorption. Rather, they suggest that multi-step energy transfer processes are involved. Possible qualitative mechanism of LIAD that are based on formation of non-equilibrium energy states in the adsorbate-substrate system are proposed and discussed.

From illite/smectite clay to mesoporous silicate adsorbent for efficient removal of chlortetracycline from water.

Science.gov (United States)

Wang, Wenbo; Tian, Guangyan; Zong, Li; Zhou, Yanmin; Kang, Yuru; Wang, Qin; Wang, Aiqin

2017-01-01

A series of mesoporous silicate adsorbents with superior adsorption performance for hazardous chlortetracycline (CTC) were sucessfully prepared via a facile one-pot hydrothermal reaction using low-cost illite/smectite (IS) clay, sodium silicate and magnesium sulfate as the starting materials. In this process, IS clay was "teared up" and then "rebuilt" as new porous silicate adsorbent with high specific surface area of 363.52m 2 /g (about 8.7 folds higher than that of IS clay) and very negative Zeta potential (-34.5mV). The inert SiOSi (Mg, Al) bonds in crystal framework of IS were broken to form Si(Al) O - groups with good adsorption activity, which greatly increased the adsorption sites served for holding much CTC molecules. Systematic evaluation on adsorption properties reveals the optimal silicate adsorbent can adsorb 408.81mg/g of CTC (only 159.7mg/g for raw IS clay) and remove 99.3% (only 46.5% for raw IS clay) of CTC from 100mg/L initial solution (pH3.51; adsorption temperature 30°C; adsorbent dosage, 3g/L). The adsorption behaviors of CTC onto the adsorbent follows the Langmuir isotherm model, Temkin equation and pseudo second-order kinetic model. The mesopore adsorption, electrostatic attraction and chemical association mainly contribute to the enhanced adsorption properties. As a whole, the high-efficient silicate adsorbent could be candidates to remove CTC from the wastewater with high amounts of CTC. Copyright © 2016. Published by Elsevier B.V.

Paleoclimatic implications of the hydrogen isotopic composition of terrigenous n-alkanes from Lake Yamzho, southern Tibetan Plateau

International Nuclear Information System (INIS)

Xia Zhonghuan; Xu Baiqing; Wu Guangjian; Zhu Liping; Muegler Ines; Gleixner, Gerd; Sachse, Dirk

2009-01-01

The hydrogen isotopic composition (δD) of leaf water used for biosynthesis of n-alkanes can be modified by climate. Therefore, the δD can be considered as potential paleolimatic proxy to explore. We compared measured δD values of alkanes (n-C 25 to n-C 31 ) extracted from a short sediment profile spanning the past 50 years with a 7-year resolution from Lake Yamzho, southern Tibetan Plateau. Climatic control was reconstructed using meteorological records of the nearby Langkazi and Lhasa weather stations. We found that the δD values of the n-alkanes correlated with the mean annular air temperature and significantly correlated with the mean growing season air temperature. On the other hand, the δD values show poor correlations with both rainfall amount and relative humidity. These results indicate that stable isotope composition of n-alkanes could be an excellent proxy for paleotemperature reconstruction. (author)

Adsorbed states of chlorophenol on Cu(110) and controlled switching of single-molecule junctions

Energy Technology Data Exchange (ETDEWEB)

Okuyama, H., E-mail: hokuyama@kuchem.kyoto-u.ac.jp; Kitaguchi, Y.; Hattori, T.; Ueda, Y.; Ferrer, N. G.; Hatta, S.; Aruga, T. [Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

2016-06-28

A molecular junction of substituted benzene (chlorophenol) is fabricated and controlled by using a scanning tunneling microscope (STM). Prior to the junction formation, the bonding geometry of the molecule on the surface is characterized by STM and electron energy loss spectroscopy (EELS). EELS shows that the OH group of chlorophenol is dissociated on Cu(110) and that the molecule is bonded nearly flat to the surface via an O atom, with the Cl group intact. We demonstrate controlled contact of an STM tip to the “available” Cl group and lift-up of the molecule while it is anchored to the surface via an O atom. The asymmetric bonding motifs of the molecule to the electrodes allow for reversible control of the junction.

Observation of the adsorption and desorption of vibrationally excited molecules on a metal surface

Science.gov (United States)

Shirhatti, Pranav R.; Rahinov, Igor; Golibrzuch, Kai; Werdecker, Jörn; Geweke, Jan; Altschäffel, Jan; Kumar, Sumit; Auerbach, Daniel J.; Bartels, Christof; Wodtke, Alec M.

2018-06-01

The most common mechanism of catalytic surface chemistry is that of Langmuir and Hinshelwood (LH). In the LH mechanism, reactants adsorb, become thermalized with the surface, and subsequently react. The measured vibrational (relaxation) lifetimes of molecules adsorbed at metal surfaces are in the range of a few picoseconds. As a consequence, vibrational promotion of LH chemistry is rarely observed, with the exception of LH reactions occurring via a molecular physisorbed intermediate. Here, we directly detect adsorption and subsequent desorption of vibrationally excited CO molecules from a Au(111) surface. Our results show that CO (v = 1) survives on a Au(111) surface for 1 × 10-10 s. Such long vibrational lifetimes for adsorbates on metal surfaces are unexpected and pose an interesting challenge to the current understanding of vibrational energy dissipation on metal surfaces. They also suggest that vibrational promotion of surface chemistry might be more common than is generally believed.

Detection of gas molecules on single Mn adatom adsorbed graphyne: a DFT-D study

Science.gov (United States)

Lu, Zhansheng; Lv, Peng; Ma, Dongwei; Yang, Xinwei; Li, Shuo; Yang, Zongxian

2018-02-01

As one of the prominent applications in intelligent systems, gas sensing technology has attracted great interest in both industry and academia. In the current study, the pristine graphyne (GY) without and with a single Mn atom is investigated to detect the gas molecules (CO, CH4, CO2, NH3, NO and O2). The pristine GY is promising to detect O2 molecules because of its chemical adsorption on GY with large electron transfer. The great stability of the Mn/GY is found, and the Mn atom prefers to anchor at the alkyne ring as a single atom. Upon single Mn atom anchoring, the sensitivity and selectivity of GY based gas sensors is significantly improved for various molecules, except CH4. The recovery time of the Mn/GY after detecting the gas molecules may help to appraise the detection efficiency for the Mn/GY. The current study will help to understand the mechanism of detecting the gas molecules, and extend the potentially fascinating applications of GY-based materials.

Organized single-molecule magnets: direct observation of new Mn12 derivatives on gold

International Nuclear Information System (INIS)

Cornia, A.; Fabretti, A.C.; Pacchioni, M.; Zobbi, L.; Bonacchi, D.; Caneschi, A.; Gatteschi, D.; Biagi, R.; Del Pennino, U.; De Renzi, V.; Gurevich, L.; Zant, H.S.J. van der

2004-01-01

Gold adsorbates of the dodecamanganese(III,IV) single-molecule magnet (SMM) [Mn 12 O 12 (L) 16 (H 2 O) 4 ] where L=16-(acetylthio)hexadecanoate have been prepared and investigated by X-ray photoelectron spectroscopy and scanning tunneling microscopy (STM). The successful imaging of Mn 12 molecules by STM represents a first step toward the magnetic addressing of individual SMMs and the development of molecule-based devices for magnetic information storage

Paleoclimate and Asian monsoon variability inferred from n-alkanes and their stable isotopes at lake Donggi Cona, NE Tibetan Plateau

Science.gov (United States)

Saini, Jeetendra; Guenther, Franziska; Mäusbacher, Roland; Gleixner, Gerd

2015-04-01

The Tibetan Plateau is one of the most extensive and sensitive region of elevated topography affecting global climate. The interplay between the Asian summer monsoon and the westerlies greatly influences the lake systems at the Tibetan Plateau. Despite a considerable number of research efforts in last decade, possible environmental reactions to change in monsoon dynamics are still not well understood. Here we present results from a sediment core of lake Donggi Cona, which dates back to late glacial period. Distinct organic geochemical proxies and stable isotopes are used to study the paleoenvironmental and hydrological changes in late glacial and Holocene period. Sedimentary n-alkanes of lake Donggi Cona are used as a proxy for paleoclimatic and monsoonal reconstruction. The hydrogen (δD) and carbon (δ13C) isotopes of n-alkanes are used as proxy for hydrological and phytoplankton productivity, respectively . Qualitative and quantitative analysis were performed for n-alkanes over the sediment core. δD proxy for sedimentary n-alkanes is used to infer lake water and rainfall signal. δD of (n-alkane C23) records the signal of the lake water, whereas δD of (n-alkane C29) record the precipitation signal, hence act as an appropriate proxy to track Asian monsoon. Long chain n-alkanes dominate over the sediment core while unsaturated mid chain n-alkenes have high abundance in some samples. From 18.4-13.8 cal ka BP, sample shows low organic productivity due to cold and arid climate. After 13.8-11.8 cal ka BP, slight increase in phytoplankton productivity indicate onset of weaker monsoon. From 11.8-6.8 cal ka BP, high content of organic matter indicates rise in productivity and strong monsoon with high inflow. After 6.8 cal ka BP, decrease in phytoplankton productivity indicating cooler climate and show terrestrial signal. Our results provide new insight into the variability of east Asian monsoon and changes in phytoplankton productivity for last 18.4 ka. Keywords: n-alkanes

Adsorption Mechanism of Inhibitor and Guest Molecules on the Surface of Gas Hydrates.

Science.gov (United States)

Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2015-09-23

The adsorption of guest and kinetic inhibitor molecules on the surface of methane hydrate is investigated by using molecular dynamics simulations. We calculate the free energy profile for transferring a solute molecule from bulk water to the hydrate surface for various molecules. Spherical solutes with a diameter of ∼0.5 nm are significantly stabilized at the hydrate surface, whereas smaller and larger solutes exhibit lower adsorption affinity than the solutes of intermediate size. The range of the attractive force is subnanoscale, implying that this force has no effect on the macroscopic mass transfer of guest molecules in crystal growth processes of gas hydrates. We also examine the adsorption mechanism of a kinetic hydrate inhibitor. It is found that a monomer of the kinetic hydrate inhibitor is strongly adsorbed on the hydrate surface. However, the hydrogen bonding between the amide group of the inhibitor and water molecules on the hydrate surface, which was believed to be the driving force for the adsorption, makes no contribution to the adsorption affinity. The preferential adsorption of both the kinetic inhibitor and the spherical molecules to the surface is mainly due to the entropic stabilization arising from the presence of cavities at the hydrate surface. The dependence of surface affinity on the size of adsorbed molecules is also explained by this mechanism.

Role of cysteine residues in the structure, stability, and alkane producing activity of cyanobacterial aldehyde deformylating oxygenase.

Directory of Open Access Journals (Sweden)

Yuuki Hayashi

Full Text Available Aldehyde deformylating oxygenase (AD is a key enzyme for alkane biosynthesis in cyanobacteria, and it can be used as a catalyst for alkane production in vitro and in vivo. However, three free Cys residues in AD may impair its catalytic activity by undesired disulfide bond formation and oxidation. To develop Cys-deficient mutants of AD, we examined the roles of the Cys residues in the structure, stability, and alkane producing activity of AD from Nostoc punctiforme PCC 73102 by systematic Cys-to-Ala/Ser mutagenesis. The C71A/S mutations reduced the hydrocarbon producing activity of AD and facilitated the formation of a dimer, indicating that the conserved Cys71, which is located in close proximity to the substrate-binding site, plays crucial roles in maintaining the activity, structure, and stability of AD. On the other hand, mutations at Cys107 and Cys117 did not affect the hydrocarbon producing activity of AD. Therefore, we propose that the C107A/C117A double mutant is preferable to wild type AD for alkane production and that the double mutant may be used as a pseudo-wild type protein for further improvement of the alkane producing activity of AD.

Measurement of the average mass of proteins adsorbed to a nanoparticle by using a suspended microchannel resonator.

Science.gov (United States)

Nejadnik, M Reza; Jiskoot, Wim

2015-02-01

We assessed the potential of a suspended microchannel resonator (SMR) to measure the adsorption of proteins to nanoparticles. Standard polystyrene beads suspended in buffer were weighed by a SMR system. Particle suspensions were mixed with solutions of bovine serum albumin (BSA) or monoclonal human antibody (IgG), incubated at room temperature for 3 h and weighed again with SMR. The difference in buoyant mass of the bare and protein-coated polystyrene beads was calculated into real mass of adsorbed proteins. The average surface area occupied per protein molecule was calculated, assuming a monolayer of adsorbed protein. In parallel, dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), and zeta potential measurements were performed. SMR revealed a statistically significant increase in the mass of beads because of adsorption of proteins (for BSA and IgG), whereas DLS and NTA did not show a difference between the size of bare and protein-coated beads. The change in the zeta potential of the beads was also measurable. The surface area occupied per protein molecule was in line with their known size. Presented results show that SMR can be used to measure the mass of adsorbed protein to nanoparticles with a high precision in the presence of free protein. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Enhanced biodegradation of alkane hydrocarbons and crude oil by mixed strains and bacterial community analysis.

Science.gov (United States)

Chen, Yu; Li, Chen; Zhou, Zhengxi; Wen, Jianping; You, Xueyi; Mao, Youzhi; Lu, Chunzhe; Huo, Guangxin; Jia, Xiaoqiang

2014-04-01

In this study, two strains, Acinetobacter sp. XM-02 and Pseudomonas sp. XM-01, were isolated from soil samples polluted by crude oil at Bohai offshore. The former one could degrade alkane hydrocarbons (crude oil and diesel, 1:4 (v/v)) and crude oil efficiently; the latter one failed to grow on alkane hydrocarbons but could produce rhamnolipid (a biosurfactant) with glycerol as sole carbon source. Compared with pure culture, mixed culture of the two strains showed higher capability in degrading alkane hydrocarbons and crude oil of which degradation rate were increased from 89.35 and 74.32 ± 4.09 to 97.41 and 87.29 ± 2.41 %, respectively. In the mixed culture, Acinetobacter sp. XM-02 grew fast with sufficient carbon source and produced intermediates which were subsequently utilized for the growth of Pseudomonas sp. XM-01 and then, rhamnolipid was produced by Pseudomonas sp. XM-01. Till the end of the process, Acinetobacter sp. XM-02 was inhibited by the rapid growth of Pseudomonas sp. XM-01. In addition, alkane hydrocarbon degradation rate of the mixed culture increased by 8.06 to 97.41 % compared with 87.29 % of the pure culture. The surface tension of medium dropping from 73.2 × 10(-3) to 28.6 × 10(-3) N/m. Based on newly found cooperation between the degrader and the coworking strain, rational investigations and optimal strategies to alkane hydrocarbons biodegradation were utilized for enhancing crude oil biodegradation.

Characterization of Adsorbents for Cytokine Removal from Blood in an In Vitro Model.

Science.gov (United States)

Harm, Stephan; Gabor, Franz; Hartmann, Jens

2015-01-01

Cytokines are basic targets that have to be removed effectively in order to improve the patient's health status in treating severe inflammation, sepsis, and septic shock. Although there are different adsorbents commercially available, the success of their clinical use is limited. Here, we tested different adsorbents for their effective removal of cytokines from plasma and the resulting effect on endothelial cell activation. The three polystyrene divinylbenzene (PS-DVB) based adsorbents Amberchrom CG161c and CG300m and a clinically approved haemoperfusion adsorbent (HAC) were studied with regard to cytokine removal in human blood. To induce cytokine release from leucocytes, human blood cells were stimulated with 1 ng/ml LPS for 4 hours. Plasma was separated and adsorption experiments in a dynamic model were performed. The effect of cytokine removal on endothelial cell activation was evaluated using a HUVEC-based cell culture model. The beneficial outcome was assessed by measuring ICAM-1, E-selectin, and secreted cytokines IL-8 and IL-6. Additionally the threshold concentration for HUVEC activation by TNF-α and IL-1β was determined using this cell culture model. CG161c showed promising results in removing the investigated cytokines. Due to its pore size the adsorbent efficiently removed the key factor TNF-α, outperforming the commercially available adsorbents. The CG161c treatment reduced cytokine secretion and expression of cell adhesion molecules by HUVEC which underlines the importance of effective removal of TNF-α in inflammatory diseases. These results confirm the hypothesis that cytokine removal from the blood should approach physiological levels in order to reduce endothelial cell activation.

Adsorption behavior of Co anchored on graphene sheets toward NO, SO{sub 2}, NH{sub 3}, CO and HCN molecules

Energy Technology Data Exchange (ETDEWEB)

Tang, Yanan, E-mail: yntang2010@hotmail.com [College of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Quantum Materials Research Center, Zhengzhou Normal University, Henan 450044 (China); Chen, Weiguang; Li, Chenggang; Pan, Lijun [College of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Quantum Materials Research Center, Zhengzhou Normal University, Henan 450044 (China); Dai, Xianqi, E-mail: xqdai@henannu.edu.cn [College of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Quantum Materials Research Center, Zhengzhou Normal University, Henan 450044 (China); Ma, Dongwei [College of Physics and Electrical Engineering, Anyang Normal University, Anyang, Henan 455000 (China)

2015-07-01

Graphical abstract: - Highlights: • In contrast to the pristine graphene, a vacancy defect in graphene strongly stabilizes the Co atom. • The positively charged of Co atom on graphene can regulate the stability of gas molecules. • Different gas molecules can modulate the electronic structure of Co–graphene systems. • The adsorbed NO on Co–graphene can effectively regulate the magnetic properties of systems. - Abstract: Based on the first-principles of density-functional theory (DFT), the effects of gas adsorption on the change in geometric stability, electronic structure and magnetic properties of graphene with anchored Co (Co–graphene) systems were investigated. A single Co adatom interacts much weaker with pristine graphene (Co/pri–graphene) than with the graphene containing a single vacancy (Co/SV–graphene). The Co dopant provides more electrons to the dangling bonds of carbon atom at defective site and exhibits more positive charges, which makes Co/SV–graphene less prone to be adsorbed by gas molecules in comparison to Co/pri–graphene. It is found that the electronic structure and magnetic properties of Co–graphene systems can be modulated by adsorbing gas molecules. Except the NH{sub 3} molecule, the adsorbed NO, SO{sub 2}, CO or HCN as electron acceptors on the Co/pri–graphene can exhibit semiconducting properties. Among the gas molecules, the strong adsorption of NO molecule can effectively regulate the magnetic properties of Co–graphene systems. Moreover, the stable configuration of Co/SV–graphene is more likely to be the gas sensor for detecting NO and SO{sub 2}. The results validate that the reactivity of atomic-scale catalyst is supported on graphene sheets, which is expected to be potentially efficient in the gas sensors and electronic device.

Direct hydrodeoxygenation of raw woody biomass into liquid alkanes.

Science.gov (United States)

Xia, Qineng; Chen, Zongjia; Shao, Yi; Gong, Xueqing; Wang, Haifeng; Liu, Xiaohui; Parker, Stewart F; Han, Xue; Yang, Sihai; Wang, Yanqin

2016-03-30

Being the only sustainable source of organic carbon, biomass is playing an ever-increasingly important role in our energy landscape. The conversion of renewable lignocellulosic biomass into liquid fuels is particularly attractive but extremely challenging due to the inertness and complexity of lignocellulose. Here we describe the direct hydrodeoxygenation of raw woods into liquid alkanes with mass yields up to 28.1 wt% over a multifunctional Pt/NbOPO4 catalyst in cyclohexane. The superior performance of this catalyst allows simultaneous conversion of cellulose, hemicellulose and, more significantly, lignin fractions in the wood sawdust into hexane, pentane and alkylcyclohexanes, respectively. Investigation on the molecular mechanism reveals that a synergistic effect between Pt, NbOx species and acidic sites promotes this highly efficient hydrodeoxygenation of bulk lignocellulose. No chemical pretreatment of the raw woody biomass or separation is required for this one-pot process, which opens a general and energy-efficient route for converting raw lignocellulose into valuable alkanes.

Relevance of carbon structure to formation of tar and liquid alkane during coal pyrolysis

International Nuclear Information System (INIS)

Liu, Peng; Le, Jiawei; Wang, Lanlan; Pan, Tieying; Lu, Xilan; Zhang, Dexiang

2016-01-01

Highlights: • Curve-fitting method was used to quantify the accurate contents of structural carbon. • Effect of carbon structure in coal with different rank on formation of pyrolysis tar was studied. • Numerical interrelation between carbon types in coal structure and tar yield is elaborated. • Effect of carbon structure on formation of liquid alkane during coal pyrolysis is discussed. - Abstract: The relevance of carbon structure to formation of tar and liquid alkane during coal pyrolysis were discussed extensively. The pyrolysis tests were carried out in a tube reactor at 873 K and keep 15 min. The carbon distribution in coals was investigated by solid state "1"3C nuclear magnetic resonance (N.M.R.). The curve-fitting method was used to quantify the accurate contents of structural carbon. The alkanes in coal tar were analyzed by Gas Chromatograph–Mass Spectrometer (GC–MS). The results show that oxygen-linked aromatic carbon decreases with the increasing of coal rank. The aliphatic carbon contents of Huainan (HN) coal are 44.20%, the highest among the four coals. The carbon types in coal structure have a significant influence on the formation of tar and liquid alkane. The coal tar yields are related to the aliphatic substituted aromatic carbon, CH_2/CH_3 ratio and oxygen-linked carbon in coal so that the increasing order of tar yield is Inner Mongolia lignite (IM, 6.30 wt.%) < Sinkiang coal (SK, 7.55 wt.%) < Shenmu coal (SM, 12.84 wt.%) < HN (16.29 wt.%). The highest contents of oxygen-linked aromatic carbon in IM lead to phenolic compound of 41.06% in IM-tar. The contents of alkane in SM-tar are the highest because the appropriate CH_2/CH_3 ratio and the highest aliphatic side chains on aromatic rings in SM leading to generate aliphatic hydrocarbon with medium molecular weight easily. The mechanism on formation of tar and liquid alkane plays an important role in guiding the industrialization of pyrolysis-based poly-generation producing tar with high

Mechanism of formation of humus coatings on mineral surfaces 3. Composition of adsorbed organic acids from compost leachate on alumina by solid-state 13C NMR

Science.gov (United States)

Wershaw, R. L.; Llaguno, E.C.; Leenheer, J.A.

1996-01-01

The adsorption of compost leachate DOC on alumina is used as a model for elucidation of the mechanism of formation of natural organic coatings on hydrous metal oxide surfaces in soils and sediments. Compost leachate DOC is composed mainly of organic acid molecules. The solid-state 13C NMR spectra of these organic acids indicate that they are very similar in composition to aquatic humic substances. Changes in the solid-state 13C NMR spectra of compost leachate DOC fractions adsorbed on alumina indicate that the DOC molecules are most likely adsorbed on metal oxide surfaces through a combination of polar and hydrophobic interaction mechanisms. This combination of polar and hydrophobic mechanism leads to the formation of bilayer coatings of the leachate molecules on the oxide surfaces.

Functional screening of aldehyde decarbonylases for long-chain alkane production by Saccharomyces cerevisiae

DEFF Research Database (Denmark)

Kang, Min-Kyoung; Zhou, Yongjin J.; Buijs, Nicolaas A.

2017-01-01

Background: Low catalytic activities of pathway enzymes are often a limitation when using microbial based chemical production. Recent studies indicated that the enzyme activity of aldehyde decarbonylase (AD) is a critical bottleneck for alkane biosynthesis in Saccharomyces cerevisiae. We therefore...... detected in other AD expressed yeast strains. Dynamic expression of SeADO and CwADO under GAL promoters increased alkane production to 0.20 mg/L/OD600 and no fatty alcohols, with even number chain lengths from C8 to C14, were detected in the cells. Conclusions: We demonstrated in vivo enzyme activities...

Orientation of rod molecules in selective slits: a density functional theory

International Nuclear Information System (INIS)

Xu Xiaofei; Cao Dapeng; Wang Wenchuan

2008-01-01

A density functional theory (DFT) is used to investigate molecular orientation of rod fluids in selective slits. The DFT approach combines a modified fundamental measure theory (MFMT) for excluded-volume effect, the first-order thermodynamics perturbation theory for chain connectivity and the mean-field approximation for van der Waals (vdW) attraction. To study the molecular orientation, the intramolecular bonding orientation function is introduced into the DFT. First, we investigate the orientation of the surfactant-like rod molecule of AB 6 (i.e. ABBBBBB) in a nanoslit of H 20σ, where the walls selectively adsorb segment 'A'. It is observed that, with the increase of the surface energy of the wall to head segment (i.e. 'A' segment) of the rod molecule, the rod molecules adsorbed on the wall present the perpendicular orientation gradually, and assemble into a smectic-A-like monolayer finally. In addition, we also explore the molecular orientation of the rods with both end segments preferring to the wall, i.e. AB 8 A and AB 7 A, in a nanoslit of H = 10σ. Interestingly, the AB 8 A rod monolayer is compatible with either a smectic-A-like or a smectic-C-like organization, but AB 7 A rod molecules exhibit the smectic-A-like organization. The orientation factor of the AB 7 A rod molecule reaches 1, suggesting that AB 7 A rod molecules self-assemble into an ordered structure with perfectly perpendicular orientation to the wall.

Enriching the hydrogen storage capacity of carbon nanotube doped with polylithiated molecules

Science.gov (United States)

Panigrahi, P.; Naqvi, S. R.; Hankel, M.; Ahuja, R.; Hussain, T.

2018-06-01

In a quest to find optimum materials for efficient storage of clean energy, we have performed first principles calculations to study the structural and energy storage properties of one-dimensional carbon nanotubes (CNTs) functionalized with polylithiated molecules (PLMs). Van der Waals corrected calculations disclosed that various PLMs like CLi, CLi2, CLi3, OLi, OLi2, OLi3, bind strongly to CNTs even at high doping concentrations ensuring a uniform distribution of dopants without forming clusters. Bader charge analysis reveals that each Li in all the PLMs attains a partial positive charge and transform into Li+ cations. This situation allows multiple H2 molecules adsorbed with each Li+ through the polarization of incident H2 molecules via electrostatic and van der Waals type of interaction. With a maximum doping concentration, that is 3CLi2/3CLi3 and 3OLi2/3OLi3 a maximum of 36 H2 molecules could be adsorbed that corresponds to a reasonably high H2 storage capacity with the adsorption energies in the range of -0.33 to -0.15 eV/H2. This suits the ambient condition applications.

Contrasting bonding behavior of thiol molecules on carbon fullerene structures

International Nuclear Information System (INIS)

Mixteco-Sanchez, J.C.; Guirado-Lopez, R.A.

2003-01-01

We have performed semiempirical as well as ab initio density-functional theory (DFT) calculations at T=0 to analyze the equilibrium configurations and electronic properties of spheroidal C 60 as well as of cylindrical armchair (5,5) and (8,8) fullerenes passivated with SCH 3 and S(CH 2 ) 2 CH 3 thiols. Our structural results reveal that the lowest-energy configurations of the adsorbates strongly depend on their chain length and on the structure of the underlying substrate. In the low-coverage regime, both SCH 3 and S(CH 2 ) 2 CH 3 molecules prefer to organize into a molecular cluster on one side of the C 60 surface, providing thus a less protective organic coating for the carbon structure. However, with increasing the number of adsorbed thiols, a transition to a more uniform distribution is obtained, which actually takes place for six and eight adsorbed molecules when using S(CH 2 ) 2 CH 3 and SCH 3 chains, respectively. In contrast, for the tubelike arrangements at the low-coverage regime, a quasi-one-dimensional zigzag organization of the adsorbates along the tubes is always preferred. The sulfur-fullerene bond is considerably strong and is at the origin of outward and lateral displacements of the carbon atoms, leading to the stabilization of three-membered rings on the surface (spheroidal structures) as well as to sizable nonuniform radial deformations (cylindrical configurations). The electronic spectrum of our thiol-passivated fullerenes shows strong variations in the energy difference between the highest occupied and lowest unoccupied molecular orbitals as a function of the number and distribution of adsorbed thiols, opening thus the possibility to manipulate the transport properties of these compounds by means of selective adsorption mechanisms

Polystyrene-Divinylbenzene-Based Adsorbents Reduce Endothelial Activation and Monocyte Adhesion Under Septic Conditions in a Pore Size-Dependent Manner.

Science.gov (United States)

Eichhorn, Tanja; Rauscher, Sabine; Hammer, Caroline; Gröger, Marion; Fischer, Michael B; Weber, Viktoria

2016-10-01

Endothelial activation with excessive recruitment and adhesion of immune cells plays a central role in the progression of sepsis. We established a microfluidic system to study the activation of human umbilical vein endothelial cells by conditioned medium containing plasma from lipopolysaccharide-stimulated whole blood or from septic blood and to investigate the effect of adsorption of inflammatory mediators on endothelial activation. Treatment of stimulated whole blood with polystyrene-divinylbenzene-based cytokine adsorbents (average pore sizes 15 or 30 nm) prior to passage over the endothelial layer resulted in significantly reduced endothelial cytokine and chemokine release, plasminogen activator inhibitor-1 secretion, adhesion molecule expression, and in diminished monocyte adhesion. Plasma samples from sepsis patients differed substantially in their potential to induce endothelial activation and monocyte adhesion despite their almost identical interleukin-6 and tumor necrosis factor-alpha levels. Pre-incubation of the plasma samples with a polystyrene-divinylbenzene-based adsorbent (30 nm average pore size) reduced endothelial intercellular adhesion molecule-1 expression to baseline levels, resulting in significantly diminished monocyte adhesion. Our data support the potential of porous polystyrene-divinylbenzene-based adsorbents to reduce endothelial activation under septic conditions by depletion of a broad range of inflammatory mediators.

Structure of adsorbed monolayers. The surface chemical bond

International Nuclear Information System (INIS)

Somorjai, G.A.; Bent, B.E.

1984-06-01

This paper attempts to provide a summary of what has been learned about the structure of adsorbed monolayers and about the surface chemical bond from molecular surface science. While the surface chemical bond is less well understood than bonding of molecules in the gas phase or in the solid state, our knowledge of its properties is rapidly accumulating. The information obtained also has great impact on many surface science based technologies, including heterogeneous catalysis and electronic devices. It is hoped that much of the information obtained from studies at solid-gas interfaces can be correlated with molecular behavior at solid-liquid interfaces. 31 references, 42 figures, 1 table

Arbuscular mycorrhizal wheat inoculation promotes alkane and polycyclic aromatic hydrocarbon biodegradation: Microcosm experiment on aged-contaminated soil.

Science.gov (United States)

Ingrid, Lenoir; Lounès-Hadj Sahraoui, Anissa; Frédéric, Laruelle; Yolande, Dalpé; Joël, Fontaine

2016-06-01

Very few studies reported the potential of arbuscular mycorrhizal symbiosis to dissipate hydrocarbons in aged polluted soils. The present work aims to study the efficiency of arbuscular mycorrhizal colonized wheat plants in the dissipation of alkanes and polycyclic aromatic hydrocarbons (PAHs). Our results demonstrated that the inoculation of wheat with Rhizophagus irregularis allowed a better dissipation of PAHs and alkanes after 16 weeks of culture by comparison to non-inoculated condition. These dissipations observed in the inoculated soil resulted from several processes: (i) a light adsorption on roots (0.5% for PAHs), (ii) a bioaccumulation in roots (5.7% for PAHs and 6.6% for alkanes), (iii) a transfer in shoots (0.4 for PAHs and 0.5% for alkanes) and mainly a biodegradation. Whereas PAHs and alkanes degradation rates were respectively estimated to 12 and 47% with non-inoculated wheat, their degradation rates reached 18 and 48% with inoculated wheat. The mycorrhizal inoculation induced an increase of Gram-positive and Gram-negative bacteria by 56 and 37% compared to the non-inoculated wheat. Moreover, an increase of peroxidase activity was assessed in mycorrhizal roots. Taken together, our findings suggested that mycorrhization led to a better hydrocarbon biodegradation in the aged-contaminated soil thanks to a stimulation of telluric bacteria and hydrocarbon metabolization in mycorrhizal roots. Copyright © 2016 Elsevier Ltd. All rights reserved.

Low-cost adsorbent prepared from sewage sludge and corn stalk for the removal of COD in leachate.

Science.gov (United States)

He, Ying; Liao, Xiaofeng; Liao, Li; Shu, Wei

2014-01-01

Sewage sludge (SS) with corn stalk (CS) was used to prepare SS-based activated carbon (SAC) by pyrolysis with ZnCl2. The effects of mixing ratio on surface area and pore size distribution, elemental composition, surface chemistry, and morphology were investigated. The results demonstrated that the addition of CS into SS samples improved the surface area (from 92 to 902 m(2)/g) and the microporosity (from 1.2 to 4.1%) of the adsorbents and, therefore, enhancing the adsorption performance. The removal of leachate chemical oxygen demand (COD) was also determined. It was found that the COD removal rate reached 85% at pH 4 with the SAC (90 wt% CS) dosage of 2% (g/mL) and an adsorption time of 40 min. The adsorption experimental data were fitted by both Langmuir and Freundlich adsorption isotherms. Long-chain alkanes and refractory organics were found in raw leachate, but could be removed by SAC largely.

Motion of Adsorbed Nano-Particles on Azobenzene Containing Polymer Films

Directory of Open Access Journals (Sweden)

Sarah Loebner

2016-12-01

Full Text Available We demonstrate in situ recorded motion of nano-objects adsorbed on a photosensitive polymer film. The motion is induced by a mass transport of the underlying photoresponsive polymer material occurring during irradiation with interference pattern. The polymer film contains azobenzene molecules that undergo reversible photoisomerization reaction from trans- to cis-conformation. Through a multi-scale chain of physico-chemical processes, this finally results in the macro-deformations of the film due to the changing elastic properties of polymer. The topographical deformation of the polymer surface is sensitive to a local distribution of the electrical field vector that allows for the generation of dynamic changes in the surface topography during irradiation with different light interference patterns. Polymer film deformation together with the motion of the adsorbed nano-particles are recorded using a homemade set-up combining an optical part for the generation of interference patterns and an atomic force microscope for acquiring the surface deformation. The particles undergo either translational or rotational motion. The direction of particle motion is towards the topography minima and opposite to the mass transport within the polymer film. The ability to relocate particles by photo-induced dynamic topography fluctuation offers a way for a non-contact simultaneous manipulation of a large number of adsorbed particles just in air at ambient conditions.

Theory and Monte-Carlo simulation of adsorbates on corrugated surfaces

DEFF Research Database (Denmark)

Vives, E.; Lindgård, P.-A.

1993-01-01

-phase between the commensurate and incommensurate phase stabilized by defects. Special attention has been given to the study of the epitaxial rotation angles of the different phases. Available experimental data is in agreement with the simulations and with a general theory for the epitaxial rotation which takes......Phase transitions in systems of adsorbed molecules on corrugated surfaces are studied by means of Monte Carlo simulation. Particularly, we have studied the phase diagram of D2 on graphite as a function of coverage and temperature. We have demonstrated the existence of an intermediate gamma...

Conductance of single atoms and molecules studied with a scanning tunnelling microscope

International Nuclear Information System (INIS)

Neel, N; Kroeger, J; Limot, L; Berndt, R

2007-01-01

The conductance of single atoms and molecules is investigated with a low-temperature scanning tunnelling microscope. In a controlled and reproducible way, clean Ag(111) surfaces, individual silver atoms on Ag(111) as well as individual C 60 molecules adsorbed on Cu(100) are contacted with the tip of the microscope. Upon contact the conductance changes discontinuously in the case of the tip-surface junction while the tip-atom and tip-molecule junctions exhibit a continuous transition from the tunnelling to the contact regime

Toluene and acetaldehyde removal from air on to graphene-based adsorbents with microsized pores.

Science.gov (United States)

Kim, Ji Min; Kim, Ji Hoon; Lee, Chang Yeon; Jerng, Dong Wook; Ahn, Ho Seon

2018-02-15

Volatile organic compound (VOC) gases can cause harm to the human body with exposure over the long term even at very low concentrations (ppmv levels); thus, effective absorbents for VOC gas removal are an important issue. In this study, accordingly, graphene-based adsorbents with microsized pores were used as adsorbents to remove toluene and acetaldehyde gases at low concentrations (30ppm). Sufficient amounts of the adsorbents were prepared for use on filters and were loaded uniformly at 0.1-0.5g on a 50×50mm 2 area, to evaluate their adsorption features with low gas concentrations. The morphology and chemical composition of the adsorbents were characterized using scanning electron microscopy, N 2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and Raman spectroscopy. Microwave irradiation and heat treatment near 800°C under KOH activation resulted in enlargement of the pristine graphene surface and its specific surface area; maximum volume capacities of 3510m 3 /g and 630m 3 /g were observed for toluene and acetaldehyde gas. The high removal efficiency for toluene (98%) versus acetaldehyde (30%) gas was attributed to π-π interactions between the pristine graphene surface and toluene molecules. Copyright © 2017 Elsevier B.V. All rights reserved.

Cluster Formation of Polyphilic Molecules Solvated in a DPPC Bilayer

Directory of Open Access Journals (Sweden)

Xiang-Yang Guo

2017-10-01

Full Text Available We analyse the initial stages of cluster formation of polyphilic additive molecules which are solvated in a dipalmitoylphosphatidylcholine (DPPC lipid bilayer. Our polyphilic molecules comprise an aromatic (trans-bilayer core domain with (out-of-bilayer glycerol terminations, complemented with a fluorophilic and an alkyl side chain, both of which are confined within the aliphatic segment of the bilayer. Large-scale molecular dynamics simulations (1 μ s total duration of a set of six of such polyphilic additives reveal the initial steps towards supramolecular aggregation induced by the specific philicity properties of the molecules. For our intermediate system size of six polyphiles, the transient but recurrent formation of a trimer is observed on a characteristic timescale of about 100 ns. The alkane/perfluoroalkane side chains show a very distinct conformational distribution inside the bilayer thanks to their different philicity, despite their identical anchoring in the trans-bilayer segment of the polyphile. The diffusive mobility of the polyphilic additives is about the same as that of the surrounding lipids, although it crosses both bilayer leaflets and tends to self-associate.

Expansion Hamiltonian model for a diatomic molecule adsorbed on a surface: Vibrational states of the CO/Cu(100) system including surface vibrations

Energy Technology Data Exchange (ETDEWEB)

Meng, Qingyong, E-mail: mengqingyong@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, 116023 Dalian (China); Meyer, Hans-Dieter, E-mail: hans-dieter.meyer@pci.uni-heidelberg.de [Theoretische Chemie, Physikalisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany)

2015-10-28

Molecular-surface studies are often done by assuming a corrugated, static (i.e., rigid) surface. To be able to investigate the effects that vibrations of surface atoms may have on spectra and cross sections, an expansion Hamiltonian model is proposed on the basis of the recently reported [R. Marquardt et al., J. Chem. Phys. 132, 074108 (2010)] SAP potential energy surface (PES), which was built for the CO/Cu(100) system with a rigid surface. In contrast to other molecule-surface coupling models, such as the modified surface oscillator model, the coupling between the adsorbed molecule and the surface atoms is already included in the present expansion SAP-PES model, in which a Taylor expansion around the equilibrium positions of the surface atoms is performed. To test the quality of the Taylor expansion, a direct model, that is avoiding the expansion, is also studied. The latter, however, requests that there is only one movable surface atom included. On the basis of the present expansion and direct models, the effects of a moving top copper atom (the one to which CO is bound) on the energy levels of a bound CO/Cu(100) system are studied. For this purpose, the multiconfiguration time-dependent Hartree calculations are carried out to obtain the vibrational fundamentals and overtones of the CO/Cu(100) system including a movable top copper atom. In order to interpret the results, a simple model consisting of two coupled harmonic oscillators is introduced. From these calculations, the vibrational levels of the CO/Cu(100) system as function of the frequency of the top copper atom are discussed.

Driving force behind adsorption-induced protein unfolding: a time-resolved X-ray reflectivity study on lysozyme adsorbed at an air/water interface.

Science.gov (United States)

Yano, Yohko F; Uruga, Tomoya; Tanida, Hajime; Toyokawa, Hidenori; Terada, Yasuko; Takagaki, Masafumi; Yamada, Hironari

2009-01-06

Time-resolved X-ray reflectivity measurements for lysozyme (LSZ) adsorbed at an air/water interface were performed to study the mechanism of adsorption-induced protein unfolding. The time dependence of the density profile at the air/water interface revealed that the molecular conformation changed significantly during adsorption. Taking into account previous work using Fourier transform infrared (FTIR) spectroscopy, we propose that the LSZ molecules initially adsorbed on the air/water interface have a flat unfolded structure, forming antiparallel beta-sheets as a result of hydrophobic interactions with the gas phase. In contrast, as adsorption continues, a second layer forms in which the molecules have a very loose structure having random coils as a result of hydrophilic interactions with the hydrophilic groups that protrude from the first layer.

Functionalized molecules studied by STM: motion, switching and reactivity

International Nuclear Information System (INIS)

Grill, Leonhard

2008-01-01

Functionalized molecules represent the central issue of molecular nanotechnology. Scanning tunnelling microscopy (STM) is a powerful method to investigate such molecules, because it allows us to image them with sub-molecular resolution when adsorbed on a surface and can be used at the same time as a tool to manipulate single molecules in a controlled way. Such studies permit deep insight into the conformational, mechanical and electronic structure and thus functionalities of the molecules. In this review, recent experiments on specially designed molecules, acting as model systems for molecular nanotechnology, are reviewed. The presented studies focus on key functionalities: lateral rolling and hopping motion on a supporting surface, the switching behaviour of azobenzene derivatives by using the STM tip and the controlled reactivity of molecular side groups, which enable the formation of covalently bound molecular nanoarchitectures. (topical review)

Density functional study the interaction of oxygen molecule with defect sites of graphene

Energy Technology Data Exchange (ETDEWEB)

Qi Xuejun [State Key Laboratory of Coal Combustion, Wuhan 430074 (China); Guo Xin, E-mail: guoxin@mail.hust.edu.cn [State Key Laboratory of Coal Combustion, Wuhan 430074 (China); Zheng Chuguang [State Key Laboratory of Coal Combustion, Wuhan 430074 (China)

2012-10-15

Highlights: Black-Right-Pointing-Pointer The defect sites existed on the graphite surface create active sites and enhance the reactivity of carbonaceous material. Black-Right-Pointing-Pointer Oxygen molecule more favor chemisorbed on the graphene surface contains defect sites than the perfect surface. Black-Right-Pointing-Pointer The single active oxygen atom adsorbed on the defect surfaces, it completely insert into the surface. - Abstract: The present article reports a theoretical study of oxygen interacted with graphene surface containing defect sites on the atomic level by employing the density functional theory combined with the graphene cluster model. It was founded that oxygen molecule prefers to be chemisorbed on the graphene surface containing defect sites compared to the perfect surface. The adsorption energy of O{sub 2} on the double defect site is about 2.5 times as large as that on the perfect graphene surface. Moreover, the oxygen molecule interacts with S-W defect site gives rise to stable epoxy structure, which pulling the carbon atom outward from the original site in the direction perpendicular to the surface. If the oxygen molecule is adsorbed on the single vacancy site, two C-O bonds are formed on the graphene surface. However, when the oxygen molecule is chemisorbed on the double vacancy site, the oxygen atoms substitute the missing carbon atom's position in the carbon plane and form a hexagonal structure on the graphene network. The results indicate that single active oxygen atom approaches the defect site, it's completely adsorbed in the plane and high energy is released. In all cases, the interaction of an oxygen atom with defect surface involves an exothermic process. The defect site creates active sites on the surface of graphene and produces catalytic effects during the process of oxidation of carbonaceous materials.

Adsorption of polar organic molecules on sediments: Case-study on Callovian-Oxfordian claystone.

Science.gov (United States)

Rasamimanana, S; Lefèvre, G; Dagnelie, R V H

2017-08-01

The release and transport of anthropogenic organic matter through the geosphere is often an environmental criterion of safety. Sedimentary rocks are widely studied in this context as geological barriers for waste management. It is the case of Callovian-Oxfordian claystone (COx), for which several studies report adsorption of anthropogenic organic molecules. In this study, we evaluated and reviewed adsorption data of polar organic molecules on COx claystone. Experiments were performed on raw claystone, decarbonated and clay fractions. Adsorption isotherms were measured with adsorbates of various polarities: adipate, benzoate, ortho-phthalate, succinate, gluconate, oxalate, EDTA, citrate. A significant adsorption was observed for multidentate polycarboxylic acids as evidenced with phthalate, succinate, oxalate, gluconate, EDTA and citrate (R d  = 1.53, 3.52, 8.4, 8.8, 12.4, 54.7 L kg -1 respectively). Multiple linear regression were performed as a statistical analysis to determine the predictors from these adsorption data. A linear correlation between adsorption data (R d ) and dipole moment (μ) of adsorbates was evidenced (R 2  = 0.91). Molecules with a high dipole moment, μ(D) > 2.5, displayed a significant adsorption, R d ≫1 L kg -1 . A qualitative correlation can be easily estimated using the water/octanol partition coefficient, P ow , of adsorbates (R 2  = 0.77). In this case, two opposite trends were distinguished for polar and apolar molecules. The use of organic carbon content in sediments is relevant for predicting adsorption of apolar compounds, log (P ow )>+1. The oxides/clays contents may be relevant regarding polar molecules, log ( apparent P ow )<-1. The proposed scheme offers a general methodology for investigation of geo-barriers towards heterogeneous organic plumes. Copyright © 2017 Elsevier Ltd. All rights reserved.

A surprising way to control the charge transport in molecular electronics: the subtle impact of the coverage of self-assembled monolayers of floppy molecules adsorbed on metallic electrodes.

Science.gov (United States)

Bâldea, Ioan

2017-10-26

Inspired by earlier attempts in organic electronics aiming at controlling charge injection from metals into organic materials by manipulating the Schottky energy barrier using self-assembled monolayers (SAMs), recent experimental and theoretical work in molecular electronics showed that metal-organic interfaces can be controlled via changes in the metal work function that are induced by SAMs. In this paper we indicate a different route to achieve interface-driven control over the charge transfer/transport at the molecular scale. It is based on the fact that, in floppy molecule based SAMs, the molecular conformation can be tuned by varying the coverage of the adsorbate. We demonstrate this effect with the aid of benchmark molecules that are often used to fabricate nanojunctions and consist of two rings that can easily rotate relative to each other. We show that, by varying the coverage of the SAM, the twisting angle φ of the considered molecular species can be modified by a factor of two. Given the fact that the low bias conductance G scales as cos 2  φ, this results in a change in G of over one order of magnitude for the considered molecular species. Tuning the twisting angle by controlling the SAM coverage may be significant, e.g., for current efforts to fabricate molecular switches. Conversely, the lack of control over the local SAM coverage may be problematic for the reproducibility and interpretation of the STM (scanning tunneling microscope) measurements on repeatedly forming single molecule break junctions.

Positronium chemistry in porous adsorbents

International Nuclear Information System (INIS)

Foti, G.; Nagy, L.G.; Moravcsik, G.; Schay, G.

1981-01-01

Kinetic studies on the annihilation of orthopositronium in porous adsorbents have been performed using lifetime spectroscopy. The positron source applied was 22 Na with 0.2 MBq activity. The adsorbents investigated were silica gels of different particle size and pore structure. The appearance of the long-lived component in the lifetime spectra can be explained by the diffusion of the orthopositronium into the pores affected by the particle size and the pore size of the adsorbent, the coverage on it and the chemical nature of the adsorbate. The long-term aim of the work is to determine and to explain these effects. (author)

Experimental measurements and prediction of liquid densities for n-alkane mixtures

International Nuclear Information System (INIS)

Ramos-Estrada, Mariana; Iglesias-Silva, Gustavo A.; Hall, Kenneth R.

2006-01-01

We present experimental liquid densities for n-pentane, n-hexane and n-heptane and their binary mixtures from (273.15 to 363.15) K over the entire composition range (for the mixtures) at atmospheric pressure. A vibrating tube densimeter produces the experimental densities. Also, we present a generalized correlation to predict the liquid densities of n-alkanes and their mixtures. We have combined the principle of congruence with the Tait equation to obtain an equation that uses as variables: temperature, pressure and the equivalent carbon number of the mixture. Also, we present a generalized correlation for the atmospheric liquid densities of n-alkanes. The average absolute percentage deviation of this equation from the literature experimental density values is 0.26%. The Tait equation has an average percentage deviation of 0.15% from experimental density measurements

Influence of Adsorbed Water on the Oxygen Evolution Reaction on Oxides

DEFF Research Database (Denmark)

Siahrostami, Samira; Vojvodic, Aleksandra

2015-01-01

We study the interface between adsorbed water and stoichiometric, defect-free (110) rutile oxide surfaces of TiO2, RuO2, and IrO2 in order to understand how water influences the stabilities of the intermediates of the oxygen evolution reaction (OER). In our model the water is treated as explicitly...... molecules binding to bridging oxygens. The third chain interacts weakly and predominantly with the H2O molecules of the second layer, resembling bulk water. We find that the stability of the water layer close to the oxide surface is almost the same as the one found on flat metal surfaces, such as the Pt(111...... of RuO2 and IrO2, while it is increased by similar to 0.4 eV for TiO2....

Adsorptionof polar organic molecules at oil/water interfaces

Energy Technology Data Exchange (ETDEWEB)

Aveyard, R; Chapman, J

1975-03-15

A study has been made of the adsorption of several esters of dicarboxylic acids at the alkane/water and the air/water interface. The adsorption of n-butanol and n-heptanol at the air/water surface also has been investigated. The surface pressure (pi) -surface area (A) isotherms are compared for the various films, and standard free energies of adsorption have been determined. Attempts have been made to fit the pi, A isotherms using surface equations of state based on the models, of both a 2-dimensional gas and a 2-dimensional solution. The solution model has proved reasonably successful for fairly dilute films at the air/water surface. At higher coverages, an equation derived by Smith for liquid expanded monolayers gives a moderately good description of films of heptanol on water. A simple application of the solution model on adsorbed monolayers at the liquid; liquid interface met with little success. However, it is found that 2-dimensional gas equations describe such systems surprisingly well for fairly low surface concentrations. (20 refs.)

Modeling of Alkane Oxidation Using Constituents and Species

Science.gov (United States)

Bellan, Jasette; Harstad, Kenneth G.

2010-01-01

It is currently not possible to perform simulations of turbulent reactive flows due in particular to complex chemistry, which may contain thousands of reactions and hundreds of species. This complex chemistry results in additional differential equations, making the numerical solution of the equation set computationally prohibitive. Reducing the chemical kinetics mathematical description is one of several important goals in turbulent reactive flow modeling. A chemical kinetics reduction model is proposed for alkane oxidation in air that is based on a parallel methodology to that used in turbulence modeling in the context of the Large Eddy Simulation. The objective of kinetic modeling is to predict the heat release and temperature evolution. This kinetic mechanism is valid over a pressure range from atmospheric to 60 bar, temperatures from 600 K to 2,500 K, and equivalence ratios from 0.125 to 8. This range encompasses diesel, HCCI, and gas-turbine engines, including cold ignition. A computationally efficient kinetic reduction has been proposed for alkanes that has been illustrated for n-heptane using the LLNL heptane mechanism. This model is consistent with turbulence modeling in that scales were first categorized into either those modeled or those computed as progress variables. Species were identified as being either light or heavy. The heavy species were decomposed into defined 13 constituents, and their total molar density was shown to evolve in a quasi-steady manner. The light species behave either in a quasi-steady or unsteady manner. The modeled scales are the total constituent molar density, Nc, and the molar density of the quasi-steady light species. The progress variables are the total constituent molar density rate evolution and the molar densities of the unsteady light species. The unsteady equations for the light species contain contributions of the type gain/loss rates from the heavy species that are modeled consistent with the developed mathematical

Variation in the Apparent Biosynthetic Fractionation for N-alkane δD Among Terrestrial Plants: Patterns, Mechanisms, and Implications

Science.gov (United States)

Johnson, J. E.; Tipple, B. J.; Betancourt, J. L.; Ehleringer, J. R.; Leavitt, S. W.; Monson, R. K.

2016-12-01

Long-chain normal alkanes (n-alkanes) are a component of the leaf cuticle of all terrestrial plants. Since the hydrogen in the n-alkanes is derived from the hydrogen in plants' water sources and is non-exchangeable, the stable hydrogen isotopic composition (δD) of the n-alkanes provides information about the δD of environmental waters. While this relationship creates opportunities for using n-alkane δD for process-based reconstructions of δD of environmental waters, progress in this direction is currently constrained by the observation that terrestrial plants exhibit a startlingly wide range of apparent biosynthetic fractionations. To understand the mechanisms responsible for variation in the apparent biosynthetic fractionations, we compared measurements and models of δD for n-C29 in a water-limited ecosystem where the timing of primary and secondary cuticle deposition is closely coupled to water availability (Tumamoc Hill, Tucson, Arizona, USA). During the 2014-2015 hydrologic year, the most widespread and abundant plant species at this site exhibited δD for n-C29 varying over a total range of 102‰. Discrete samples of leaf water collected at the same time as the n-C29 samples exhibited δD varying over a total range of only 53‰, but a continuous model of leaf water through the annual cycle predicted δD varying over a total range of 190‰. These results indicate that the observed variation in the apparent biosynthetic fractionation for n-C29 δD could be primarily attributable to leaf water dynamics that are temporally uncoupled from primary and secondary cuticle deposition. If a single biosynthetic fractionation does describe the relationship between the δD of n-alkanes and leaf water during intervals of cuticle deposition, it will facilitate process-based interpretations of n-alkane δD values in ecological, hydrological, and climatological studies of modern and ancient terrestrial environments.

Density Functional Investigation of Graphene Doped with Amine-Based Organic Molecules

Directory of Open Access Journals (Sweden)

Yeun Hee Hwang

2015-01-01

Full Text Available To improve the electronic properties of graphene, many doping techniques have been studied. Herein, we investigate the electronic and molecular structure of doped graphene using density functional theory, and we report the effects of amine-based benzene dopants adsorbed on graphene. Density functional theory (DFT calculations were performed to determine the role of amine-based aromatic compounds in graphene doping. These organic molecules bind to graphene through long-range interactions such as π-π interactions and C-H⋯π hydrogen bonding. We compared the electronic structures of pristine graphene and doped graphene to understand the electronic structure of doped graphene at the molecular level. Also, work functions of doped graphene were obtained from electrostatic potential calculations. A decrease in the work function was observed when the amine-based organic compounds were adsorbed onto graphene. Because these systems are based on physisorption, there was no obvious band structure change at point K at the Fermi level after doping. However, the amine-based organic dopants did change the absolute Fermi energy levels. In this study, we showed that the Fermi levels of the doped graphene were affected by the HOMO energy level of the dopants and by the intermolecular charge transfer between the adsorbed molecules and graphene.

Organized single-molecule magnets: direct observation of new Mn{sub 12} derivatives on gold

Energy Technology Data Exchange (ETDEWEB)

Cornia, A.; Fabretti, A.C.; Pacchioni, M.; Zobbi, L. E-mail: lzobbi@unimo.it; Bonacchi, D.; Caneschi, A.; Gatteschi, D.; Biagi, R.; Del Pennino, U.; De Renzi, V.; Gurevich, L.; Zant, H.S.J. van der

2004-05-01

Gold adsorbates of the dodecamanganese(III,IV) single-molecule magnet (SMM) [Mn{sub 12}O{sub 12}(L){sub 16}(H{sub 2}O){sub 4}] where L=16-(acetylthio)hexadecanoate have been prepared and investigated by X-ray photoelectron spectroscopy and scanning tunneling microscopy (STM). The successful imaging of Mn{sub 12} molecules by STM represents a first step toward the magnetic addressing of individual SMMs and the development of molecule-based devices for magnetic information storage.

QSPR models based on molecular mechanics and quantum chemical calculations. 1. Construction of Boltzmann averaged descriptors for alkanes, alcohols, diols, ethers and cyclic compounds

DEFF Research Database (Denmark)

Dyekjær, Jane Dannow; Rasmussen, Kjeld; Jonsdottir, Svava Osk

2002-01-01

Values for nine descriptors for QSPR (quantitative structure-property relationships) modeling of physical properties of 96 alkanes, alcohols, ethers, diols, triols and cyclic alkanes and alcohols in conjunction with the program Codessa are presented. The descriptors are Boltzmann-averaged by sele......Values for nine descriptors for QSPR (quantitative structure-property relationships) modeling of physical properties of 96 alkanes, alcohols, ethers, diols, triols and cyclic alkanes and alcohols in conjunction with the program Codessa are presented. The descriptors are Boltzmann...

Iodine removal adsorbent histories, aging and regeneration

International Nuclear Information System (INIS)

Hunt, J.R.; Rankovic, L.; Lubbers, R.; Kovach, J.L.

1976-01-01

The experience of efficiency changes with life under various test conditions is described. The adsorbents were periodically removed from both standby and continuously operating systems and tested under various test methods for residual iodine adsorption efficiency. Adsorbent from several conventional ''sampler'' cartridges versus the bulk adsorbent was also tested showing deficiency in the use of cartridge type sampling. Currently required test conditions were found inadequate to follow the aging of the adsorbent because pre-equilibration of the sample acts as a regenerant and the sample is not tested in the ''as is'' condition. The most stringent test was found to be the ambient temperature, high humidity test to follow the aging of the adsorbent. Several methods were evaluated to regenerate used adsorbents; of these high temperature steaming and partial reimpregnation were found to produce adsorbents with near identical properties of freshly prepared adsorbents

Theoretical Insight of Physical Adsorption for a Single-Component Adsorbent + Adsorbate System: I. Thermodynamic Property Surfaces

KAUST Repository

Chakraborty, Anutosh

2009-02-17

Thermodynamic property surfaces for a single-component adsorbent + adsorbate system are derived and developed from the viewpoint of classical thermodynamics, thermodynamic requirements of chemical equilibrium, Gibbs law, and Maxwell relations. They enable us to compute the entropy and enthalpy of the adsorbed phase, the isosteric heat of adsorption, specific heat capacity, and the adsorbed phase volume thoroughly. These equations are very simple and easy to handle for calculating the energetic performances of any adsorption system. We have shown here that the derived thermodynamic formulations fill up the information gap with respect to the state of adsorbed phase to dispel the confusion as to what is the actual state of the adsorbed phase. We have also discussed and established the temperature-entropy diagrams of (i) CaCl 2-in-silica gel + water system for cooling applications, and (ii) activated carbon (Maxsorb III) + methane system for gas storage. © Copyright 2009 American Chemical Society.

Exploration of sensing of nitrogen dioxide and ozone molecules using novel TiO2/Stanene heterostructures employing DFT calculations

Science.gov (United States)

Abbasi, Amirali; Sardroodi, Jaber Jahanbin

2018-06-01

Based on the density functional theory (DFT) calculations, we explored the sensing capabilities and electronic structures of TiO2/Stanene heterostructures as novel and highly efficient materials for detection of toxic NO2 and O3 molecules in the environment. Studied gas molecules were positioned at different sites and orientations towards the nanocomposite, and the adsorption process was examined based on the most stable structures. We found that both of these molecules are chemically adsorbed on the TiO2/Stanene heterostructures. The calculations of the adsorption energy indicate that the fivefold coordinated titanium sites of the TiO2/Stanene are the most stable sites for the adsorption of NO2 and O3 molecules. The side oxygen atoms of the gas molecules were found to be chemically bonded to these titanium atoms. The adsorption of gas molecules is an exothermic process, and the adsorption on the pristine nanocomposite is more favorable in energy than that on the nitrogen-doped nanocomposite. The effects of van der Waals interactions were taken into account, which indicate the adsorption energies were increased for the most sable configurations. The gas sensing response and charge transfers were analyzed in detail. The pristine nanocomposites have better sensing response than the doped ones. The spin density distribution plots indicate that the magnetization was mainly located over the adsorbed gas molecules. Mulliken charge analysis reveals that both NO2 and O3 molecules behave as charge acceptors, as evidenced by the accumulation of electronic charges on the adsorbed molecules predicted by charge density difference calculations. Our DFT results provide a theoretical basis for an innovative gas sensor system designed from a sensitive TiO2/Stanene heterostructures for efficient detection of harmful air pollutants such as NO2 and O3.

Development and characterization of activated hydrochars from orange peels as potential adsorbents for emerging organic contaminants.

Science.gov (United States)

Fernandez, M E; Ledesma, B; Román, S; Bonelli, P R; Cukierman, A L

2015-05-01

Activated hydrochars obtained from the hydrothermal carbonization of orange peels (Citrus sinensis) followed by various thermochemical processing were assessed as adsorbents for emerging contaminants in water. Thermal activation under flows of CO2 or air as well as chemical activation with phosphoric acid were applied to the hydrochars. Their characteristics were analyzed and related to their ability to uptake three pharmaceuticals (diclofenac sodium, salicylic acid and flurbiprofen) considered as emerging contaminants. The hydrothermal carbonization and subsequent activations promoted substantial chemical transformations which affected the surface properties of the activated hydrochars; they exhibited specific surface areas ranging from 300 to ∼620 m(2)/g. Morphological characterization showed the development of coral-like microspheres dominating the surface of most hydrochars. Their ability to adsorb the three pharmaceuticals selected was found largely dependent on whether the molecules were ionized or in their neutral form and on the porosity developed by the new adsorbents. Copyright © 2015 Elsevier Ltd. All rights reserved.

Catalytic conversion of light alkanes. Quarterly progress report, April 1--June 30, 1992

Energy Technology Data Exchange (ETDEWEB)

Lyons, J.E.

1992-06-30

The second Quarterly Report of 1992 on the Catalytic Conversion of Light Alkanes reviews the work done between April 1, 1992 and June 31, 1992 on the Cooperative Agreement. The mission of this work is to devise a new catalyst which can be used in a simple economic process to convert the light alkanes in natural gas to oxygenate products that can either be used as clean-burning, high octane liquid fuels, as fuel components or as precursors to liquid hydrocarbon uwspomdon fuel. During the past quarter we have continued to design, prepare, characterize and test novel catalysts for the mild selective reaction of light hydrocarbons with air or oxygen to produce alcohols directly. These catalysts are designed to form active metal oxo (MO) species and to be uniquely active for the homolytic cleavage of the carbon-hydrogen bonds in light alkanes producing intermediates which can form alcohols. We continue to investigate three molecular environments for the active catalytic species that we are trying to generate: electron-deficient macrocycles (PHASE I), polyoxometallates (PHASE II), and regular oxidic lattices including zeolites and related structures as well as other molecular surface structures having metal oxo groups (PHASE I).

The metrics of surface adsorbed small molecules on the Young's fringe dual-slab waveguide interferometer

International Nuclear Information System (INIS)

Cross, Graham H; Reeves, Andrew; Brand, Stuart; Swann, Marcus J; Peel, Louise L; Freeman, Neville J; Lu, Jian R

2004-01-01

A method for analysing thin films using a dual-waveguide interferometric technique is described. Alternate dual polarization addressing of the interferometer sensor using a ferroelectric liquid crystal polarization switch allowed the opto-geometrical properties (density and thickness) of adsorbed layers at a solid-liquid interface to be determined. Differences in the waveguide mode dispersion between the transverse electric and transverse magnetic modes allowed unique combinations of layer thickness and refractive index to be determined at all stages of the layer formation process. The technique has been verified by comparing the analysis of the surface adsorption of surfactants with data obtained using neutron scattering techniques, observing their behaviour on trimethylsilane coated silicon oxynitride surfaces. The data obtained were found to be in excellent agreement with analogous neutron scattering experiments and the precision of the measurements taken to be of the order of 40 pm with respect to adsorbed layer thicknesses. The study was extended to a series of surfactants whose layer morphology could be correlated with their hydrophilicity/lipophilicity balance. Those in the series with longer alkyl chains were observed to form thinner, denser layers at the hydrophobic solid/aqueous liquid interface and the degree of order attained at sub-critical micelle concentrations to be correlated with molecular fluidity. The technique is expected to find utility with those interested in thin film analysis. An important and growing area of application is within the life sciences, especially in the field of protein structure and function

Stable hydrogen isotopic composition of n-alkanes in atmospheric aerosols as a tracer for the source region of terrestrial plant waxes

Science.gov (United States)

Yamamoto, S.; Kawamura, K.

2009-12-01

Studies on molecular composition and compound-specific carbon isotopic ratio (δ13C) of leaf wax n-alkanes in atmospheric aerosols have revealed a long-range atmospheric transport of terrestrial higher plant materials over the south Atlantic and western Pacific oceans. However, molecular and δ13C compositions of terrestrial plant waxes in the eastern part of the Asian continent are relatively constant reflecting C3-dominated vegetation, which makes it difficult to specify the source regions of plant materials in the atmospheric aerosols over the East Asia and northwest Pacific regions. Recent observation displays a large (>100‰) spatial variation in hydrogen isotopic composition (δD) of rainwater in East Asia. Because δD values of terrestrial higher plants sensitively reflect those of precipitation waters, δD of leaf waxes are expected to provide information on their source region. In this study, we measured the δD of n-alkanes in atmospheric aerosols from Tokyo to better understand the origin of leaf wax n-alkanes in atmospheric aerosols. The δD values of fossil fuel n-alkanes (C21 to C24) in Tokyo aerosols range from -65 to -94‰, which are in a range of those reported in marine crude oils. In contrast, the δD of higher molecular weight (C29 and C31) n-alkanes (δDHMW) show much larger values by ~70‰ than those of fossil fuel n-alkanes. Their values were found to exhibit concomitant variations with carbon preference index (CPI), suggesting that the δDHMW reflect the δD of leaf wax n-alkanes with a variable contribution from fossil fuel n-alkanes. Nevertheless, good positive correlation (r = 0.89, p < 0.01) between the δDHMW and CPI values enable us to remove the contribution of fossil fuels using a mass balance approach by assuming that CPI of fossil fuel is 1 and CPI of plant waxes is 5-15. Calculated n-alkane δD values averaged from -170 to -185‰ for C29 and from -155 to -168‰ for C31. These values are consistent with those reported from

Hindered rotation of a copper phthalocyanine molecule on C60 : Experiments and molecular mechanics calculations

NARCIS (Netherlands)

Fendrich, M.; Wagner, Th.; Stöhr, M.; Möller, R.

2006-01-01

If copper phthalocyanine (CuPc) molecules are deposited on a Au(111) surface covered with a monolayer of C60, the molecules are found to adsorb individually onto the close-packed layer of C60. As the adsorption site of the CuPc is not symmetric with respect to the underlying C60 layer, the CuPc

Experimental demonstration of a single-molecule electric motor.

Science.gov (United States)

Tierney, Heather L; Murphy, Colin J; Jewell, April D; Baber, Ashleigh E; Iski, Erin V; Khodaverdian, Harout Y; McGuire, Allister F; Klebanov, Nikolai; Sykes, E Charles H

2011-09-04

For molecules to be used as components in molecular machines, methods that couple individual molecules to external energy sources and that selectively excite motion in a given direction are required. Significant progress has been made in the construction of molecular motors powered by light and by chemical reactions, but electrically driven motors have not yet been built, despite several theoretical proposals for such motors. Here we report that a butyl methyl sulphide molecule adsorbed on a copper surface can be operated as a single-molecule electric motor. Electrons from a scanning tunnelling microscope are used to drive the directional motion of the molecule in a two-terminal setup. Moreover, the temperature and electron flux can be adjusted to allow each rotational event to be monitored at the molecular scale in real time. The direction and rate of the rotation are related to the chiralities of both the molecule and the tip of the microscope (which serves as the electrode), illustrating the importance of the symmetry of the metal contacts in atomic-scale electrical devices.

Milestone Report - Complete New Adsorbent Materials for Marine Testing to Demonstrate 4.5 g-U/kg Adsorbent

Energy Technology Data Exchange (ETDEWEB)

Janke, Christopher James [ORNL; Das, Sadananda [ORNL; Oyola, Yatsandra [ORNL; Mayes, Richard T. [ORNL; Saito, Tomonori [ORNL; Brown, Suree [ORNL; Gill, Gary [PNNL; Kuo, Li-Jung [PNNL; Wood, Jordana [PNNL

2014-08-01

This report describes work on the successful completion of Milestone M2FT-14OR03100115 (8/20/2014) entitled, “Complete new adsorbent materials for marine testing to demonstrate 4.5 g-U/kg adsorbent”. This effort is part of the Seawater Uranium Recovery Program, sponsored by the U.S. Department of Energy, Office of Nuclear Energy, and involved the development of new adsorbent materials at the Oak Ridge National Laboratory (ORNL) and marine testing at the Pacific Northwest National Laboratory (PNNL). ORNL has recently developed two new families of fiber adsorbents that have demonstrated uranium adsorption capacities greater than 4.5 g-U/kg adsorbent after marine testing at PNNL. One adsorbent was synthesized by radiation-induced graft polymerization of itaconic acid and acrylonitrile onto high surface area polyethylene fibers followed by amidoximation and base conditioning. This fiber showed a capacity of 4.6 g-U/kg adsorbent in marine testing at PNNL. The second adsorbent was prepared by atom-transfer radical polymerization of t-butyl acrylate and acrylonitrile onto halide-functionalized round fibers followed by amidoximation and base hydrolysis. This fiber demonstrated uranium adsorption capacity of 5.4 g-U/kg adsorbent in marine testing at PNNL.

High performance Mo adsorbent PZC

Energy Technology Data Exchange (ETDEWEB)

Anon,

1998-10-01

We have developed Mo adsorbents for natural Mo(n, {gamma}){sup 99}Mo-{sup 99m}Tc generator. Among them, we called the highest performance adsorbent PZC that could adsorb about 250 mg-Mo/g. In this report, we will show the structure, adsorption mechanism of Mo, and the other useful properties of PZC when you carry out the examination of Mo adsorption and elution of {sup 99m}Tc. (author)

Direct observation of solid-phase adsorbate concentration profile in powdered activated carbon particle to elucidate mechanism of high adsorption capacity on super-powdered activated carbon.

Science.gov (United States)

Ando, Naoya; Matsui, Yoshihiko; Matsushita, Taku; Ohno, Koichi

2011-01-01

Decreasing the particle size of powdered activated carbon (PAC) by pulverization increases its adsorption capacities for natural organic matter (NOM) and polystyrene sulfonate (PSS, which is used as a model adsorbate). A shell adsorption mechanism in which NOM and PSS molecules do not completely penetrate the adsorbent particle and instead preferentially adsorb near the outer surface of the particle has been proposed as an explanation for this adsorption capacity increase. In this report, we present direct evidence to support the shell adsorption mechanism. PAC particles containing adsorbed PSS were sectioned with a focused ion beam, and the solid-phase PSS concentration profiles of the particle cross-sections were directly observed by means of field emission-scanning electron microscopy/energy-dispersive X-ray spectrometry (FE-SEM/EDXS). X-ray emission from sulfur, an index of PSS concentration, was higher in the shell region than in the inner region of the particles. The X-ray emission profile observed by EDXS did not agree completely with the solid-phase PSS concentration profile predicted by shell adsorption model analysis of the PSS isotherm data, but the observed and predicted profiles were not inconsistent when the analytical errors were considered. These EDXS results provide the first direct evidence that PSS is adsorbed mainly in the vicinity of the external surface of the PAC particles, and thus the results support the proposition that the increase in NOM and PSS adsorption capacity with decreasing particle size is due to the increase in external surface area on which the molecules can be adsorbed. Copyright © 2010 Elsevier Ltd. All rights reserved.

Electrochemical Properties of Alkanethiol Monolayers Adsorbed on Nanoporous Au Surfaces

International Nuclear Information System (INIS)

Chu, Yeon Yi; Seo, Bora; Kim, Jong Won

2010-01-01

We investigated the electrochemical properties of alkanethiol monolayers adsorbed on NPG surfaces by cyclic voltammetry and electrochemical impedance spectroscopy, and the results are compared to those on flat Au surfaces. The reductive desorption of alkanethiols on NPG surfaces is observed in more negative potential regions than that on flat Au surfaces due the stronger S-Au interaction on NPG surfaces. While the electron transfer through alkanethiol monolayers on flat Au surfaces occurs via a tunneling process through the monolayer films, the redox species can permeate through the monolayers on NPG surfaces to transfer the electrons to the Au surfaces. The results presented here will help to elucidate the intrinsic electrochemical properties of alkanethiol monolayers adsorbed on curved Au surfaces, particularly on the surface of AuNPs. Self-assembled monolayers (SAMs) of thiolate molecules on Au surfaces have been the subject of intensive research for the last few decades due to their unique physical and chemical properties. The well-organized surface structures of thiolate SAMs with various end-group functionalities can be further utilized for many applications in biology and nanotechnology. In addition to the practical applications, SAMs of thiolate molecules on Au surfaces also provide unique opportunities to address fundamental issues in surface chemistry such as self-organized surface structures, electron transfer behaviors, and moleculesubstrate interactions. Although there have been numerous reports on the fundamental physical and chemical properties of thiolate SAMs on Au surfaces, most of them were investigated on flat Au surfaces, typically on well-defined Au(111) surfaces

Vibrations of a molecule in an external force field.

Science.gov (United States)

Okabayashi, Norio; Peronio, Angelo; Paulsson, Magnus; Arai, Toyoko; Giessibl, Franz J

2018-05-01

The oscillation frequencies of a molecule on a surface are determined by the mass distribution in the molecule and the restoring forces that occur when the molecule bends. The restoring force originates from the atomic-scale interaction within the molecule and with the surface, which plays an essential role in the dynamics and reactivity of the molecule. In 1998, a combination of scanning tunneling microscopy with inelastic tunneling spectroscopy revealed the vibrational frequencies of single molecules adsorbed on a surface. However, the probe tip itself exerts forces on the molecule, changing its oscillation frequencies. Here, we combine atomic force microscopy with inelastic tunneling spectroscopy and measure the influence of the forces exerted by the tip on the lateral vibrational modes of a carbon monoxide molecule on a copper surface. Comparing the experimental data to a mechanical model of the vibrating molecule shows that the bonds within the molecule and with the surface are weakened by the proximity of the tip. This combination of techniques can be applied to analyze complex molecular vibrations and the mechanics of forming and loosening chemical bonds, as well as to study the mechanics of bond breaking in chemical reactions and atomic manipulation.

Theoretical Insight of Physical Adsorption for a Single Component Adsorbent + Adsorbate System: II. The Henry Region

KAUST Repository

Chakraborty, Anutosh

2009-07-07

The Henry coefficients of a single component adsorbent + adsorbate system are calculated from experimentally measured adsorption isotherm data, from which the heat of adsorption at zero coverage is evaluated. The first part of the papers relates to the development of thermodynamic property surfaces for a single-component adsorbent + adsorbate system1 (Chakraborty, A.; Saha, B. B.; Ng, K. C.; Koyama, S.; Srinivasan, K. Langmuir 2009, 25, 2204). A thermodynamic framework is presented to capture the relationship between the specific surface area (Ai) and the energy factor, and the surface structural and the surface energy heterogeneity distribution factors are analyzed. Using the outlined approach, the maximum possible amount of adsorbate uptake has been evaluated and compared with experimental data. It is found that the adsorbents with higher specific surface areas tend to possess lower heat of adsorption (ΔH°) at the Henry regime. In this paper, we have established the definitive relation between Ai and ΔH° for (i) carbonaceous materials, metal organic frameworks (MOFs), carbon nanotubes, zeolites + hydrogen, and (ii) activated carbons + methane systems. The proposed theoretical framework of At and AH0 provides valuable guides for researchers in developing advanced porous adsorbents for methane and hydrogen uptake. © 2009 American Chemical Society.

High Selectivity of Alkanes Production by Calcium Basic Soap Thermal Decarboxylation

Directory of Open Access Journals (Sweden)

Neonufa Godlief F.

2018-01-01

Full Text Available Renewable fuel production from vegetable oil and fat or its fatty acids by direct decarboxylation has been widely reported. An innovative approach to produce drop-in fuel via thermal catalytic decarboxylation of basic soap derived from palm stearin reported in this research. The catalytic effect of the calcium and magnesium metals in the basic soap and its decarboxylation on drop-in fuel yield and product distribution was studied. The catalytic effect was tested in the temperature range up to 370°C and atmospheric pressure for 5 hours in a batch reactor. It has been proved that the calcium basic soap decarboxylation, effectively produce the drop-in fuel in carbon ranges C8 – C20, in which more than 78% selectivity toward alkane. Whereas, only 70% selectivity toward alkane has been resulted from the magnesium basic soap decarboxylation.

Biodegradation of crude oil and n-alkanes by fungi isolated from Oman

Energy Technology Data Exchange (ETDEWEB)

Elshafie, Abdulkadir [Department of Biology, College of Science, Sultan Qaboos University, P.O. Box 36 Al Khod, Muscat (Oman)], E-mail: Elshafie@squ.edu.om; AlKindi, Abdulaziz Yahya [Department of Biology, College of Science, Sultan Qaboos University, P.O. Box 36 Al Khod, Muscat (Oman); Al-Busaidi, Sultan [Oman Refinery Company Laboratories, LLC, P.O. Box 3568 Ruwi PC112 (Oman); Bakheit, Charles [Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, P.O. Box 36 Al Khod, Muscat (Oman); Albahry, S.N. [Department of Biology, College of Science, Sultan Qaboos University, P.O. Box 36 Al Khod, Muscat (Oman)

2007-11-15

Ten fungal species isolated from tar balls collected from the beaches of Oman were tested for their abilities to grow and degrade n-alkanes and crude oil. The abilities of Aspergillus niger, A. ochraceus and Penicillium chrysogenum to degrade n-alkanes (C13-C18), crude oil were compared and their mycelial biomass was measured. Significant differences were found in the utilization of C15, C16, C17 and C18 by the three fungi. Similarly, significant differences we found in the amount of biomass produced by the three fungi growing on C13, C17, C18 and crude oil. The correlation coefficient of biomass and oil utilization was not statistically significant for Aspergillus niger, significant for Aspergillus terreus and highly significant for P. chrysogenum.

Biodegradation of crude oil and n-alkanes by fungi isolated from Oman

International Nuclear Information System (INIS)

Elshafie, Abdulkadir; AlKindi, Abdulaziz Yahya; Al-Busaidi, Sultan; Bakheit, Charles; Albahry, S.N.

2007-01-01

Ten fungal species isolated from tar balls collected from the beaches of Oman were tested for their abilities to grow and degrade n-alkanes and crude oil. The abilities of Aspergillus niger, A. ochraceus and Penicillium chrysogenum to degrade n-alkanes (C13-C18), crude oil were compared and their mycelial biomass was measured. Significant differences were found in the utilization of C15, C16, C17 and C18 by the three fungi. Similarly, significant differences we found in the amount of biomass produced by the three fungi growing on C13, C17, C18 and crude oil. The correlation coefficient of biomass and oil utilization was not statistically significant for Aspergillus niger, significant for Aspergillus terreus and highly significant for P. chrysogenum

Mass and Force Sensing of an Adsorbate on a Beam Resonator Sensor

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Yin Zhang

2015-06-01

Full Text Available The mass sensing superiority of a micro-/nano-mechanical resonator sensor over conventional mass spectrometry has been, or at least is being firmly established. Because the sensing mechanism of a mechanical resonator sensor is the shifts of resonant frequencies, how to link the shifts of resonant frequencies with the material properties of an analyte formulates an inverse problem. Besides the analyte/adsorbate mass, many other factors, such as position and axial force, can also cause the shifts of resonant frequencies. The in situ measurement of the adsorbate position and axial force is extremely difficult if not impossible, especially when an adsorbate is as small as a molecule or an atom. Extra instruments are also required. In this study, an inverse problem of using three resonant frequencies to determine the mass, position and axial force is formulated and solved. The accuracy of the inverse problem solving method is demonstrated, and how the method can be used in the real application of a nanomechanical resonator is also discussed. Solving the inverse problem is helpful to the development and application of a mechanical resonator sensor for two reasons: reducing extra experimental equipment and achieving better mass sensing by considering more factors.

Mobility of adsorbed Cry1Aa insecticidal toxin from Bacillus thuringiensis (Bt) on montmorillonite measured by fluorescence recovery after photobleaching (FRAP)

Science.gov (United States)

Helassa, Nordine; Daudin, Gabrielle; Noinville, Sylvie; Janot, Jean-Marc; Déjardin, Philippe; Staunton, Siobhán; Quiquampoix, Hervé

2010-06-01

The insecticidal toxins produced by genetically modified Bt crops are introduced into soil through root exudates and tissue decomposition and adsorb readily on soil components, especially on clays. This immobilisation and the consequent concentration of the toxins in "hot spots" could increase the exposure of soil organisms. Whereas the effects on non-target organisms are well documented, few studies consider the migration of the toxin in soil. In this study, the residual mobility of Bt Cry1Aa insecticidal toxin adsorbed on montmorillonite was assessed using fluorescence recovery after photobleaching (FRAP). This technique, which is usually used to study dynamics of cytoplasmic and membrane molecules in live cells, was applied for the first time to a protein adsorbed on a finely divided swelling clay mineral, montmorillonite. No mobility of adsorbed toxin was observed at any pH and at different degrees of surface saturation.

Packaging of single DNA molecules by the yeast mitochondrial protein Abf2p: reinterpretation of recent single molecule experiments.

Science.gov (United States)

Stigter, Dirk

2004-07-01

Brewer et al. (Biophys. J. 85 (2003) 2519-2524) have studied the compaction of dsDNA in a double flow cell by observing the extension of stained DNA tethered in buffer solutions with or without Abf2p. They use a Langmuir adsorption model in which one Abf2p molecule adsorbs on one site on the DNA, and the binding constant, K, is given as the ratio of the experimental rates of adsorption and desorption. This paper presents an improved interpretation. Instead of Langmuir adsorption we use the more appropriate McGhee-von Hippel (J. Mol. Biol. 86 (1974) 469-489) theory for the adsorption of large ligands to a one-dimensional lattice. We assume that each adsorbed molecule shortens the effective contour length of DNA by the foot print of Abf2p of 27 base pairs. When Abf2p adsorbs to DNA stretched in the flowing buffer solution, we account for a tension effect that decreases the adsorption rate and the binding constant by a factor of 2 to 4. The data suggest that the accessibility to Abf2p decreases significantly with increasing compaction of DNA, resulting in a lower adsorption rate and a lower binding constant. The kinetics reported by Brewer et al. (Biophys. J. 85 (2003) 2519-2524) lead to a binding constant K=3.6 x 10(6) M(-1) at the beginning, and to K=5 x 10(5) M(-1) near the end of a compaction run, more than an order of magnitude lower than the value K=2.57 x 10(7) M(-1) calculated by Brewer et al. (Biophys. J. 85 (2003) 2519-2524).

First-principle study of structural, electronic, vibrational and magnetic properties of HCN adsorbed graphene doped with Cr, Mn and Fe

International Nuclear Information System (INIS)

Shi, Li Bin; Wang, Yong Ping; Dong, Hai Kuan

2015-01-01

Graphical abstract: - Highlights: • Cr, Mn and Fe doped graphene is more active to adsorb HCN molecule than pristine graphene. • The conductivity of Fe and Mn doped graphene hardly changes after adsorption HCN molecule. • The conductivity of Cr doped graphene can be affected significantly due to HCN adsorption. • The Cr, Mn and Fe may destroy the long range order in graphene. • Phonon density of states suggests that Cr doped graphene is stable. - Abstract: The adsorption energy, electronic structure, lattice vibration and magnetic properties of Cr, Mn and Fe doped graphene with and without HCN adsorption are investigated by the first principles based on density functional theory. The physisorption and chemisorption have been identified. In the paper, Cr-NG, Mn-NG and Fe-NG denote HCN adsorption on Cr, Mn and Fe doped graphene with N atom toward the adsorption site. It is found that the adsorption energy is −1.36 eV for Fe-NG, −0.60 eV for Mn-NG and −0.86 eV for Cr-NG. The Cr-NG will convert from half-metallic behavior to semiconductor after adsorbing HCN molecule, which indicates that the conductivity changes significantly. Phonon density of states (PDOS) shows that the long range order in graphene can be destroyed by doping Fe, Mn and Cr. The imaginary frequency mode in PDOS suggests that Fe and Mn doped graphene is unstable, while Cr doped graphene is stable. The electronic properties are sensitive toward adsorbing HCN, indicating that Cr doped graphene is a promising sensor for detecting HCN molecule. This study provides a useful basis for understanding of a wide variety of physical properties on graphene

New type of amidoxime-group-containing adsorbent for the recovery of uranium from seawater. III. Recycle use of adsorbent

International Nuclear Information System (INIS)

Omichi, H.; Katakai, A.; Sugo, T.; Okamoto, J.

1986-01-01

An amidoxime-group adsorbent for recovering uranium from seawater was made by radiation-induced graft polymerization of acrylonitrile onto polymeric fiber, followed by amidoximation. Uranium adsorption of the adsorbent contacted with seawater in a column increased with the increase in flow rate, then leveled off. The relationship between uranium adsorption in a batch process and the ratio of the amount of seawater to that of adsorbent was found to be effective in evaluating adsorbent contacted with any amount of seawater. The conditioning of the adsorbent with an alkaline solution at higher temperature (∼80 0 C) after the acid desorption recovered the adsorption ability to the original level. This made it possible to apply the adsorbent to recycle use. On the other hand, the adsorbent conditioned at room temperature or that without conditioning lost adsorption ability during recycle use. The increase in water uptake was observed as one of the physical changes produced during recycle use of the alkaline-conditioned adsorbent, while the decrease in water uptake was observed with the unconditioned adsorbent. The IR spectra of the adsorbent showed a probability of reactions of amidoxime groups with acid and alkaline solutions, which can explain the change in uranium adsorption during the adsorption-desorption cycle

Study of composite adsorbent synthesis and characterization for the removal of Cs in the high-salt and high-radioactive wastewater

Energy Technology Data Exchange (ETDEWEB)

Kim, Jimin; Lee, Keun Young; Kim, Kwang Wook; Lee, Eil Hee; Chung, Dong Yong; Moon, Jei Kwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Hyun, Jae Hyuk [Chungnam National University, Daejeon (Korea, Republic of)

2017-03-15

For the removal of cesium (Cs) from high radioactive/high salt-laden liquid waste, this study synthesized a highly efficient composite adsorbent (potassium cobalt ferrocyanide (PCFC)-loaded chabazite (CHA)) and evaluated its applicability. The composite adsorbent used CHA, which could accommodate Cs as well as other molecules, as a supporting material and was synthesized by immobilizing the PCFC in the pores of CHA through stepwise impregnation/precipitation with CoCl{sub 2} and K{sub 4}Fe (CN){sub 6} solutions. When CHA, with average particle size of more than 10 μm, is used in synthesizing the composite adsorbent, the PCFC particles were immobilized in a stable form. Also, the physical stability of the composite adsorbent was improved by optimizing the washing methodology to increase the purity of the composite adsorbent during the synthesis. The composite adsorbent obtained from the optimal synthesis showed a high adsorption rate of Cs in both fresh water (salt-free condition) and seawater (high-salt condition), and had a relatively high value of distribution coefficient (larger than 10{sup 4} mL·g{sup -1}) regardless of the salt concentration. Therefore, the composite adsorbent synthesized in this study is an optimized material considering both the high selectivity of PCFC on Cs and the physical stability of CHA. It is proved that this composite adsorbent can remove rapidly Cs contained in high radioactive/high salt-laden liquid waste with high efficiency.

Possible pore size effects on the state of tris(8-quinolinato)aluminum(III) (Alq3) adsorbed in mesoporous silicas and their temperature dependence.

Science.gov (United States)

Tagaya, Motohiro; Ogawa, Makoto

2008-12-07

The states of tris(8-quinolinato)aluminum(III) (Alq3) adsorbed in mesoporous silicas with different pore sizes (2.5, 3.1 and 5.0 nm) were investigated. Alq3 was successfully occluded into the mesoporous silicas from solution and the adsorbed amount of Alq3 per BET surface area was effectively controlled by changing the added amount Alq3 to the solution. The state of Alq3 in the mesopore varied depending on the pore size as well as the adsorbed amount of Alq3 as revealed by variation of the photoluminescence spectra. The luminescence of the adsorbed Alq3 was found to be temperature-dependent, indicating the mobility of the adsorbed Alq3 to temperature variations. The temperature-dependence also depended on the pore size. The guest-guest interactions between Alq3 molecules as well as the host-guest interactions between Alq3 and the mesopore were controlled by the pore size.

Crystallisation and chain conformation of long chain n-alkanes

International Nuclear Information System (INIS)

Gorce, J.

2000-06-01

Hydrocarbon chains are a basic component in a number of systems as diverse as biological membranes, phospholipids and polymers. A better understanding of the physical properties of n-alkane chains should provide a better understanding of these more complex systems. With this aim, vibrational spectroscopy has been extensively used. This technique, sensitive to molecular details, is the only one able to both identify and quantify conformational disorder present in paraffinic systems. To achieve this, methyl deformations have been widely used as ''internal standards'' for the normalisation of peak areas. However, in the case of n-alkanes with short chain length, such as n-C 44 H 90 for example, the infrared spectra recorded at liquid nitrogen temperature and reported here show the sensitivity of these latter peaks to the various crystal structures formed. Indeed, the main frequencies of the symmetric methyl bending mode were found between 1384 cm -1 and 1368 cm -1 as a function of the crystal form. Changes in the frequency of the first order of the L.A.M. present in the Raman spectra were also observed. At higher temperatures, non all-trans conformers, inferred from different infrared bands present in the wagging mode region, were found to be essentially placed at the end of the n-alkane chains. At the monoclinic phase transition, the concentration of end-gauche conformers, proportional to the area of the infrared band at 1342 cm -1 , increases abruptly. On the contrary, in the spectra recorded at liquid nitrogen temperature no such band is observed. We also studied the degree of disorder in two purely monodisperse long chain n-alkanes, namely n-C 198 H 398 and n-C 246 H 494 . The chain conformation as well as the tilt angle of the chains from the crystal surfaces were determined by means of low frequency Raman spectroscopy and S.A.X.S. measurements on solution-crystallised samples. The increase in the number of end-gauche conformers which was expected to occur with

The condensation of water on adsorbed viruses.

Science.gov (United States)

Alonso, José María; Tatti, Francesco; Chuvilin, Andrey; Mam, Keriya; Ondarçuhu, Thierry; Bittner, Alexander M

2013-11-26

The wetting and dewetting behavior of biological nanostructures and to a greater degree single molecules is not well-known even though their contact with water is the basis for all biology. Here, we show that environmental electron microscopy (EM) can be applied as a means of imaging the condensation of water onto viruses. We captured the formation of submicrometer water droplets and filaments on single viral particles by environmental EM and by environmental transmission EM. The condensate structures are compatible with capillary condensation between adsorbed virus particles and with known droplet shapes on patterned surfaces. Our results confirm that such droplets exist down to condensation/evaporation cycle as expected from their stability in air and water. Moreover we developed procedures that overcome problems of beam damage and of resolving structures with a low atomic number.

Solvent-free synthesis of C10 and C11 branched alkanes from furfural and methyl isobutyl ketone.

Science.gov (United States)

Yang, Jinfan; Li, Ning; Li, Guangyi; Wang, Wentao; Wang, Aiqin; Wang, Xiaodong; Cong, Yu; Zhang, Tao

2013-07-01

Our best results jet: C10 and C11 branched alkanes, with low freezing points, are synthesized through the aldol condensation of furfural and methyl isobutyl ketone from lignocellulose, which is then followed by hydrodeoxygenation. These jet-fuel-range alkanes are obtained in high overall yields (≈90%) under solvent-free conditions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption of aromatic compounds by carbonaceous adsorbents: a comparative study on granular activated carbon, activated carbon fiber, and carbon nanotubes.

Science.gov (United States)

Zhang, Shujuan; Shao, Ting; Kose, H Selcen; Karanfil, Tanju

2010-08-15

Adsorption of three aromatic organic compounds (AOCs) by four types of carbonaceous adsorbents [a granular activated carbon (HD4000), an activated carbon fiber (ACF10), two single-walled carbon nanotubes (SWNT, SWNT-HT), and a multiwalled carbon nanotube (MWNT)] with different structural characteristics but similar surface polarities was examined in aqueous solutions. Isotherm results demonstrated the importance of molecular sieving and micropore effects in the adsorption of AOCs by carbonaceous porous adsorbents. In the absence of the molecular sieving effect, a linear relationship was found between the adsorption capacities of AOCs and the surface areas of adsorbents, independent of the type of adsorbent. On the other hand, the pore volume occupancies of the adsorbents followed the order of ACF10 > HD4000 > SWNT > MWNT, indicating that the availability of adsorption site was related to the pore size distributions of the adsorbents. ACF10 and HD4000 with higher microporous volumes exhibited higher adsorption affinities to low molecular weight AOCs than SWNT and MWNT with higher mesopore and macropore volumes. Due to their larger pore sizes, SWNTs and MWNTs are expected to be more efficient in adsorption of large size molecules. Removal of surface oxygen-containing functional groups from the SWNT enhanced adsorption of AOCs.

Electronic spectral properties of surfaces and adsorbates and atom-adsorbate van der Waals interactions

International Nuclear Information System (INIS)

Lovric, D.; Gumhalter, B.

1988-01-01

The relevance of van der Waals interactions in the scattering of neutral atoms from adsorbates has been recently confirmed by highly sensitive molecular-beam techniques. The theoretical descriptions of the collision dynamics which followed the experimental studies have necessitated very careful qualitative and quantitative examinations and evaluations of the properties of atom-adsorbate van der Waals interactions for specific systems. In this work we present a microscopic calculation of the strengths and reference-plane positions for van der Waals potentials relevant for scattering of He atoms from CO adsorbed on various metallic substrates. In order to take into account the specificities of the polarization properties of real metals (noble and transition metals) and of chemisorbed CO, we first calculate the spectra of the electronic excitations characteristic of the respective electronic subsystems by using various data sources available and combine them with the existing theoretical models. The reliability of the calculated spectra is then verified in each particular case by universal sum rules which may be established for the electronic excitations of surfaces and adsorbates. The substrate and adsorbate polarization properties which derive from these calculations serve as input data for the evaluation of the strengths and reference-plane positions of van der Waals potentials whose computed values are tabulated for a number of real chemisorption systems. The implications of the obtained results are discussed in regard to the atom-adsorbate scattering cross sections pertinent to molecular-beam scattering experiments

A novel superparamagnetic surface molecularly imprinted nanoparticle adopting dummy template: an efficient solid-phase extraction adsorbent for bisphenol A.

Science.gov (United States)

Lin, Zhenkun; Cheng, Wenjing; Li, Yanyan; Liu, Zhiren; Chen, Xiangping; Huang, Changjiang

2012-03-30

Leakage of the residual template molecules is one of the biggest challenges for application of molecularly imprinted polymer (MIP) in solid-phase extraction (SPE). In this study, bisphenol F (BPF) was adopted as a dummy template to prepare MIP of bisphenol A (BPA) with a superparamagnetic core-shell nanoparticle as the supporter, aiming to avoid residual template leakage and to increase the efficiency of SPE. Characterization and test of the obtained products (called mag-DMIP beads) revealed that these novel nanoparticles not only had excellent magnetic property but also displayed high selectivity to the target molecule BPA. As mag-DMIP beads were adopted as the adsorbents of solid-phase extraction for detecting BPA in real water samples, the recoveries of spiked samples ranged from 84.7% to 93.8% with the limit of detection of 2.50 pg mL(-1), revealing that mag-DMIP beads were efficient SPE adsorbents. Copyright © 2012 Elsevier B.V. All rights reserved.

Thermodynamic Studies of Decane on Boron Nitride and Graphite Substrates Using Synchrotron Radiation and Molecular Dynamics Simulations

Science.gov (United States)

Strange, Nicholas; Arnold, Thomas; Forster, Matthew; Parker, Julia; Larese, J. Z.; Diamond Light Source Collaboration; University of Tennessee Team

2014-03-01

Hexagonal boron nitride (hBN) has a lattice structure similar to that of graphite with a slightly larger lattice parameter in the basal plane. This, among other properties, makes it an excellent substrate in place of graphite, eliciting some important differences. This work is part of a larger effort to examine the interaction of alkanes with magnesium oxide, graphite, and boron nitride surfaces. In our current presentation, we will discuss the interaction of decane with these surfaces. Decane exhibits a fully commensurate structure on graphite and hBN at monolayer coverages. In this particular experiment, we have examined the monolayer structure of decane adsorbed on the basal plane of hBN using synchrotron x-ray radiation at Diamond Light Source. Additionally, we have examined the system experimentally with volumetric isotherms as well as computationally using molecular dynamics simulations. The volumetric isotherms allow us to calculate properties which provide important information about the adsorbate's interaction with not only neighboring molecules, but also the interaction with the adsorbent boron nitride.

Electrons, Photons, and Force: Quantitative Single-Molecule Measurements from Physics to Biology

Science.gov (United States)

2011-01-01

Single-molecule measurement techniques have illuminated unprecedented details of chemical behavior, including observations of the motion of a single molecule on a surface, and even the vibration of a single bond within a molecule. Such measurements are critical to our understanding of entities ranging from single atoms to the most complex protein assemblies. We provide an overview of the strikingly diverse classes of measurements that can be used to quantify single-molecule properties, including those of single macromolecules and single molecular assemblies, and discuss the quantitative insights they provide. Examples are drawn from across the single-molecule literature, ranging from ultrahigh vacuum scanning tunneling microscopy studies of adsorbate diffusion on surfaces to fluorescence studies of protein conformational changes in solution. PMID:21338175

Effect of Thermal Maturation on n-alkanes and Kerogen in Preserved Organic Matter: Implications for Paleoenvironment Biomarkers

Science.gov (United States)

Craven, O. D.; Longbottom, T. L.; Hockaday, W. C.; Blackaby, E.

2017-12-01

Understanding the effects of maturity on biomarkers is vital in assessing biomarker reliability in mature sediments. It is well known for n-alkanes that increased maturity shortens chain lengths and decreases the odd over even preference however, the amount of change in these variables has not been determined for different maturities and types of preserved organic matter. For this reason, it is difficult to judge the trustworthiness of even lightly matured samples for paleoenvironment reconstruction. Another complication is the difficulty of accurately determining maturity as many maturity indicators are error-prone or not appropriate at low maturities. Using hydrous pyrolysis, we artificially matured black shale samples with type I (lacustrine) and type II (marine) kerogen to measure changes in n-alkane length and odd over even preference. Whole rock samples underwent hydrous pyrolysis for 72 hours, at 250 °C, 300 °C, 325 °C, 350 °C, and 375 °C to cover a wide maturity range. From the immature and artificially matured samples, the bitumen was extracted and the saturate fraction was separated using column chromatography. The saturate fraction was analyzed for n-alkanes using gas chromatography-mass spectroscopy. Kerogen structural changes were also measured using solid-state 13C NMR to relate changes in n-alkane biomarkers to changes in kerogen structure. Results show that for type I bitumen the n-alkanes did not change at low maturities considered premature in terms of oil generation (<325 °C). The NMR spectra of the type I kerogen support the lack of change, at low maturities no changes in the aliphatic portion (Fal) were observed, however, after 325 °C Fal decreased with increasing maturity. The loss of Fal indicates kerogen contributing hydrocarbons to bitumen that cause changes in n-alkane measurements. The type II kerogen's Fal also decreased with increasing maturity, but unlike the type I kerogen Fal loss started at low maturities. The differences

Krypton retention on solid adsorbents

International Nuclear Information System (INIS)

Monson, P.R. Jr.

1980-01-01

Radioactive krypton-85 is released to the atmosphere in the off-gas from nuclear reprocessing plants. Three main methods have been suggested for removal of krypton from off-gas streams: cryogenic distillation; fluorocarbon absorption; and adsorption on solid sorbents. Use of solid adsorbents is the least developed of these methods, but offers the potential advantages of enhanced safety and lower operating costs. An experimental laboratory program was developed that will be used to investigate systematically many solid adsorbents (such as zeolites, i.e., mordenites) for trapping krypton in air. The objective of this investigation is to find an adsorbent that is more economical than silver-exchanged mordenite. Various physical and chemical characteristics such as adsorption isotherms, decontamination factors, co-adsorption, regeneration, and the mechanism and kinetics of noble gas adsorption were used to characterize the adsorbents. In the experimental program, a gas chromatograph using a helium ionization detector was used to measure the krypton in air before and after the adsorbent bed. This method can determine directly decontamination factors greater than 100

Study of Liquid Alkanes Production from Biomass-Derived Carbohydrates by Aldol-Condensation and Hydrogenation Processes

Directory of Open Access Journals (Sweden)

Navadol Laosiripojana

2010-10-01

Full Text Available This research aims to synthesis liquid alkanes from biomass-derived hydroxyl methyl furfural (HMF and furfural by aldol-condensation and hydrogenation processes over several catalysts i.e. TiO2, TiO2-ZrO2, Pd/Al2O3 and Pd/CeO2. It was found that the catalysts make significant impact on the selectivity and yield of alkanes product. It is noted that Pd/Al2O3 provided the highest alkane yield and selectivity. The aldol-condensation and hydrogenation of HMF over Pd/Al2O3 provide high C12 selectivity whereas the aldol-condensation and hydrogenation of furfural over Pd/Al2O3 provide high C8 selectivity. The effects of reaction temperature, reaction pressure and reaction time were then studied. The effect of inlet furfural to acetone molar ratio was also determined. It was also found that the optimized conditions to maximize the yield of alkane production from the aldol-condensation/hydrogenation of HMF and furfural are (i at 53oC and 24 hr for aldol-condenstation of HMF, (ii 80oC and 24 hr for aldol-condenstation of furfural, and (iii 120oC for 6 hr with HMF to acetone molar ratio of 3:1 and furfural to acetone molar ratio of 4:1 in the presence of Pd/Al2O3 (calcined at 500oC for hydrogenation reaction.

Adsorption and dissociation of oxygen molecules on Si(111)-(7×7) surface

International Nuclear Information System (INIS)

Niu, Chun-Yao; Wang, Jian-Tao

2013-01-01

The adsorption and dissociation of O 2 molecules on Si(111)-(7×7) surface have been studied by first-principles calculations. Our results show that all the O 2 molecular species adsorbed on Si(111)-(7×7) surface are unstable and dissociate into atomic species with a small energy barrier about 0.1 eV. The single O 2 molecule adsorption tends to form an ins×2 or a new metastable ins×2* structure on the Si adatom sites and the further coming O 2 molecules adsorb on those structures to produce an ad-ins×3 structure. The ad-ins×3 structure is indeed highly stable and kinetically limited for diving into the subsurface layer to form the ins×3-tri structure by a large barrier of 1.3 eV. Unlike the previous views, we find that all the ad-ins, ins×2, and ad-ins×3 structures show bright images, while the ins×2*, ins×3, and ins×3-tri structures show dark images. The proposed oxidation pathways and simulated scanning tunneling microscope images account well for the experimental results and resolve the long-standing confusion and issue about the adsorption and reaction of O 2 molecules on Si(111) surface

Cell for studying electron-adsorbed gas interactions; Cellule d'etudes des interactions electron-gaz adsorbe

Energy Technology Data Exchange (ETDEWEB)

Golowacz, H; Degras, D A [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires, Deptartement de Physique des Plasmas et de la Fusion Controlee, Service de Physique Appliquee, Service de Physique des Interractions Electroniques, Section d' Etude des Interactions Gaz-Solides

1967-07-01

The geometry and the technology of a cell used for investigations on electron-adsorbed gas interactions are described. The resonance frequencies of the surface ions which are created by the electron impact on the adsorbed gas are predicted by simplified calculations. The experimental data relative to carbon monoxide and neon are in good agreement with these predictions. (authors) [French] Les caracteristiques geometriques et technologiques generales d'une cellule d'etude des interactions entre un faisceau d'electrons et un gaz adsorbe sont donnees. Un calcul simplifie permet de prevoir les frequences de resonance des ions de surface crees par l'impact des electrons sur le gaz adsorbe. Les donnees experimentales sur l'oxyde de carbone et le neon confirment les previsions du calcul. (auteurs)

Characterization and two-dimensional crystallization of membrane component AlkB of the medium-chain alkane hydroxylase system from Pseudomonas putida GPo1.

Science.gov (United States)

Alonso, Hernan; Roujeinikova, Anna

2012-11-01

The alkane hydroxylase system of Pseudomonas putida GPo1 allows it to use alkanes as the sole source of carbon and energy. Bacterial alkane hydroxylases have tremendous potential as biocatalysts for the stereo- and regioselective transformation of a wide range of chemically inert unreactive alkanes into valuable reactive chemical precursors. We have produced and characterized the first 2-dimensional crystals of the integral membrane component of the P. putida alkane hydroxylase system, the nonheme di-iron alkane monooxygenase AlkB. Our analysis reveals for the first time that AlkB reconstituted into a lipid bilayer forms trimers. Addition of detergents that do not disrupt the AlkB oligomeric state (decyl maltose neopentyl glycol [DMNG], lauryl maltose neopentyl glycol [LMNG], and octaethylene glycol monododecyl ether [C(12)E(8)]) preserved its activity at a level close to that of the detergent-free control sample. In contrast, the monomeric form of AlkB produced by purification in n-decyl-β-D-maltopyranoside (DM), n-dodecyl-β-D-maltopyranoside (DDM), octyl glucose neopentyl glycol (OGNG), and n-dodecyl-N,N-dimethylamine-N-oxide (LDAO) was largely inactive. This is the first indication that the physiologically active form of membrane-embedded AlkB may be a multimer. We present for the first time experimental evidence that 1-octyne acts as a mechanism-based inhibitor of AlkB. Therefore, despite the lack of any significant full-length sequence similarity with members of other monooxygenase classes that catalyze the terminal oxidation of alkanes, AlkB is likely to share a similar catalytic mechanism.

Molecular sieve isolation technique for use in stable carbon isotope analysis of individual long-chain n-alkanes in crude oil

International Nuclear Information System (INIS)

Yamada, Keita; Kon, Makoto; Naraoka, Hiroshi; Ishiwatari, Ryoshi; Uzaki, Minoru.

1994-01-01

An isolation procedure of microgram amounts of long-chain n-alkanes from crude oil using molecular sieve was examined for its applicability to stable carbon isotope analysis by gas chromatography/isotope ratio mass spectrometry (GC/IRMS). The procedure examined is as follows: molecular sieve (type 5A, 200 mg) in 1 ml of isooctane solvent are mixed with a saturated hydrocarbon fraction extracted from an appropriate amount (approx. 20 mg) of crude oil and stayed at room temperatures for more than 3 hours. Long-chain n-alkanes are isolated by extraction with n-hexane after dissolution of the resulting molecular sieve with 47% hydrofluoric acid solution. The recoveries were 90±6% for C 15 -C 34 n-alkanes when their total amounts applied do not exceed 1.4 mg. No effect of the isolation procedure on carbon isotope ratios of n-alkanes was observed. (author)

Bioavailability of Carbon Nanomaterial-Adsorbed Polycyclic Aromatic Hydrocarbons to Pimphales promelas: Influence of Adsorbate Molecular Size and Configuration.

Science.gov (United States)

Linard, Erica N; Apul, Onur G; Karanfil, Tanju; van den Hurk, Peter; Klaine, Stephen J

2017-08-15

Despite carbon nanomaterials' (CNMs) potential to alter the bioavailability of adsorbed contaminants, information characterizing the relationship between adsorption behavior and bioavailability of CNM-adsorbed contaminants is still limited. To investigate the influence of CNM morphology and organic contaminant (OC) physicochemical properties on this relationship, adsorption isotherms were generated for a suite of polycyclic aromatic hydrocarbons (PAHs) on multiwalled carbon nanotubes (MWCNTs) and exfoliated graphene (GN) in conjunction with determining the bioavailability of the adsorbed PAHs to Pimphales promelas using bile analysis via fluorescence spectroscopy. Although it appeared that GN adsorbed PAHs indiscriminately compared to MWCNTs, the subsequent bioavailability of GN-adsorbed PAHs was more sensitive to PAH morphology than MWCNTs. GN was effective at reducing bioavailability of linear PAHs by ∼70%, but had little impact on angular PAHs. MWCNTs were sensitive to molecular size, where bioavailability of two-ringed naphthalene was reduced by ∼80%, while bioavailability of the larger PAHs was reduced by less than 50%. Furthermore, the reduction in bioavailability of CNM-adsorbed PAHs was negatively correlated with the amount of CNM surface area covered by the adsorbed-PAHs. This study shows that the variability in bioavailability of CNM-adsorbed PAHs is largely driven by PAH size, configuration and surface area coverage.

Ligand-accelerated activation of strong C-H bonds of alkanes by a (salen)ruthenium(VI)-nitrido complex.

Science.gov (United States)

Man, Wai-Lun; Lam, William W Y; Kwong, Hoi-Ki; Yiu, Shek-Man; Lau, Tai-Chu

2012-09-03

Kinetic and mechanistic studies on the intermolecular activation of strong C-H bonds of alkanes by a (salen)ruthenium(VI) nitride were performed. The initial, rate-limiting step, the hydrogen atom transfer (HAT) from the alkane to Ru(VI)≡N, generates Ru(V)=NH and RC·HCH(2)R. The following steps involve N-rebound and desaturation. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural Exploration of the Two HBI Alkanes in the Chinese Maoming Oil Shale

Science.gov (United States)

Liao, J.; Lu, H.; Wang, Q.; Zhou, Y., Sr.

2017-12-01

The Maoming oil shale is notable for its high rate of oil production and abundant biomarker compounds. Apart from the odd-numbered C31 and C33botryococcanes dominant and characteristic, two highly branched isoprenoid (HBI) alkanes (Fig. 1) were exclusively occurred (Brassell et al., 1986). The first identification of the two HBI alkanes in the Maoming oil shale was based on a comparison with the mass spectrum of C20 HBI (2,6,10-trimethyl-7-(3-methylbutyl)dodecane) (Yon et al., 1982; Rowland et al., 1985 ) from Rozel Point crude oil. Brassell et al (1986) thought that the characteristic ions at m/z 308 and 336 could be indicative of an additional C10 alkyl side chain on top of the characteristic ions of m/z 168 and 197 for the C20-HBI. However, the structural speculation seemed suspicious for not only their mass spectrum but also their co-chromatography results were not identical to the later synthesized C30 HBI alkane (Rowland and Robson, 1990). In addition, the source attribution of diatoms indicated by two C30 HBIs was inconsistent with the species of B race of Botryococcus braunii indicated by the dominant distribution of botryococcanes. Thus, the thirty-year-old structural assignment of the two C30 HBI alkanes may require confirmation. At first, the monomers of two HBIs were prepared by preparative gas chromatography. The HR-EI MS (436.5003) illustrated a formula of C31H64 rather than carbon numbered C30 HBIs. Moreover, two novel polymethyl alkane structures (I, II) could be yielded by 1D and 2D NMR results (Fig. 2), which completely different from that of previously speculated C30-HBIs (Fig. 2). According to the elucidated structure, the characteristic ions at m/z 308, 336, 434 and other irons at m/z 127, 211, 225, 281, 336 were mainly corresponded to relevant cleavages. Hence, their mass spectra were basically consistent with the structure determined from the NMR data. The new structural skeleton in our results for the two compounds does not support the

Slow Diffusive Motions in a Monolayer of Tetracosane Molecules Adsorbed on Graphite

DEFF Research Database (Denmark)

Taub, H.; Hansen, Flemming Yssing; Criswell, L.

2004-01-01

to a temperature of similar to230 K, we observe the QNS energy width to be dispersionless, consistent with molecular dynamics simulations showing rotational motion of the molecules about their long axis. At 260 K, the QNS energy width begins to increase with wave vector transfer, suggesting onset of nonuniaxial...

3D Oxidized Graphene Frameworks: An Efficient Adsorbent for Methylene Blue

Science.gov (United States)

Pandey, Abhishek; Deb, Madhurima; Tiwari, Shreya; Pawar, Pranav Bhagwan; Saxena, Sumit; Shukla, Shobha

2018-04-01

Extraordinary properties of graphene and its derivatives have found application in varied areas such as energy, electronics, optical devices and sensors, to name a few. Large surface area along with specialized functional groups make these materials attractive for removal of dye molecules in solution via adsorption. Industrial effluents contain large amounts of toxic chemicals resulting in pollution of water bodies, which pose environmental hazards in general. Here we report application of 3D oxidized graphene frameworks in the efficient removal of cationic dye molecules such as methylene blue via adsorption. Systematic parametric studies investigating the effect of the initial dye concentration, pH and contact time have been performed. Spectroscopic analysis of the filtrate suggests that tortuous paths in 3D oxidized graphene frameworks result in efficient removal of dye molecules due to enhanced interaction. The hydroxyl groups retained in these 3D oxidized graphene frameworks facilitate adsorption of the dye molecules while passing through the adsorbent. pH studies suggest that maximum removal efficiency for methylene blue was achieved at pH value of 9. The results suggest that these 3D oxidized graphene frameworks can be used for purification of large volumes of contaminated water from cationic dyes in waste water treatment plants.

Potential Energy Surface of NO on Pt(997: Adsorbed States and Surface Diffusion

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N. Tsukahara

2012-01-01

Full Text Available The potential energy surface (PES of NO on Pt(997 has been elucidated: the adsorption states and diffusion processes of NO on Pt(997 at low coverage were investigated by using infrared reflection absorption spectroscopy (IRAS and scanning tunneling microscopy (STM. When NO molecules adsorb on a surface at a low temperature (11 K, each molecule transiently migrates on the surface from the first impact point to a possible adsorption site. We found that there are four stable adsorption sites for NO on Pt(997: a bridge site of the upper step, an fcc- (or hcp- hollow site of the terrace, an on-top site of the terrace, and an fcc-hollow site of the lower step. At higher temperatures above 45 K, NO molecules start to migrate thermally to more stable adsorption sites on a terrace, and they are finally trapped at the bridge sites of the step, which are the most stable among the four sites.

Single NdPc2 molecules on surfaces. Adsorption, interaction, and molecular magnetism

International Nuclear Information System (INIS)

Fahrendorf, Sarah

2013-01-01

They have huge potential for application in molecular-spin-transistors, molecular-spinvalves, and molecular quantum computing. SMMs are characterized by high spin ground states with zero-field splitting leading to high relaxation barriers and long relaxation times. A relevant class of molecules are the lanthanide double-decker phthalocyanines (LaPc 2 ) with only one metal atom sandwiched between two organic phthalocyanine (Pc) ligands. For envisaged spintronic applications it is important to understand the interaction between the molecules and the substrate and its influence on the electronic and magnetic properties. The subject of this thesis is the investigation of the adsorbed neodymium double-decker phthalocyanine (NdPc 2 ) by means of low temperature scanning tunneling microscopy and spectroscopy (STM and STS). The molecules are deposited by sublimation onto different substrates. It is observed that a large fraction of the double-decker molecules decomposes during deposition. The decomposition probability strongly depends on the chosen substrate. Therefore it is concluded that the substrate modifies the electronic structure of the molecule leading to a stabilization or destabilization of the molecular entity. Charge transfer from the surface to the molecule is identified as a potential stabilizing mechanism. The electronic and magnetic properties are investigated in detail for adsorbed NdPc 2 molecules on Cu(100). The results of the experimental study are compared to state-of-the-art density functional theory calculations performed by our colleagues from the Peter Gruenberg Institute (PGI-1) at the Forschungszentrum Juelich. Interestingly, the lower Pc ring of the molecule hybridizes intensely with the substrate leading to strong chemisorption of the molecule, while the upper Pc ring keeps its molecular type electronic states, which can be energetically shifted by an external electric field. Importantly, it is possible to get direct access to the spin

The adsorber loop concept for the contact between seawater and adsorber granulate

International Nuclear Information System (INIS)

Koske, P.H.; Ohlrogge, K.

1984-01-01

The present paper deals with the so-called ''adsorber loop concept'' in which the adsorber granulate is carried along with the seawater to be processed in a loop-like configuration and is separated again from the depleted water before this is leaving the adsorption unit. This concept enables high seawater velocities thus reducing the required bed area. Theoretical considerations are presented together with experimental results from field tests. (orig.) [de

A Novel Nanohybrid Nanofibrous Adsorbent for Water Purification from Dye Pollutants

Directory of Open Access Journals (Sweden)

Shahin Homaeigohar

2016-10-01

Full Text Available In this study, we devised a novel nanofibrous adsorbent made of polyethersulfone (PES for removal of methylene blue (MB dye pollutant from water. The polymer shows a low isoelectric point thus at elevated pHs and, being nanofibrous, can offer a huge highly hydroxylated surface area for adsorption of cationic MB molecules. As an extra challenge, to augment the adsorbent’s properties in terms of adsorption capacity in neutral and acidic conditions and thermal stability, vanadium pentoxide (V2O5 nanoparticles were added to the nanofibers. Adsorption data were analyzed according to the Freundlich adsorption model. The thermodynamic parameters verified that only at basic pH is the adsorption spontaneous and in general the process is entropy-driven and endothermic. The kinetics of the adsorption process was evaluated by the pseudo-first- and pseudo-second-order models. The latter model exhibited the highest correlation with data. In sum, the adsorbent showed a promising potential for dye removal from industrial dyeing wastewater systems, especially when envisaging their alkaline and hot conditions.

Process for producing zeolite adsorbent and process for treating radioactive liquid waste with the zeolite adsorbent

International Nuclear Information System (INIS)

Motojima, K.; Kawamura, F.

1984-01-01

Zeolite is contacted with an aqueous solution containing at least one of copper, nickel, cobalt, manganese and zinc salts, preferably copper and nickel salts, particularly preferably copper salt, in such a form as sulfate, nitrate, or chloride, thereby adsorbing the metal on the zeolite in its pores by ion exchange, then the zeolite is treated with a water-soluble ferrocyanide compound, for example, potassium ferrocyanide, thereby forming metal ferrocyanide on the zeolite in its pores. Then, the zeolite is subjected to ageing treatment, thereby producing a zeolite adsorbent impregnated with metal ferrocyanide in the pores of zeolite. The adsorbent can selectively recover cesium with a high percent cesium removal from a radioactive liquid waste containing at least radioactive cesium, for example, a radioactive liquid waste containing cesium and such coexisting ions as sodium, magnesium, calcium and carbonate ions at the same time at a high concentration. The zeolite adsorbent has a stable adsorbability for a prolonged time

Insights into the Anaerobic Biodegradation Pathway of n-Alkanes in Oil Reservoirs by Detection of Signature Metabolites

Science.gov (United States)

Bian, Xin-Yu; Maurice Mbadinga, Serge; Liu, Yi-Fan; Yang, Shi-Zhong; Liu, Jin-Feng; Ye, Ru-Qiang; Gu, Ji-Dong; Mu, Bo-Zhong

2015-01-01

Anaerobic degradation of alkanes in hydrocarbon-rich environments has been documented and different degradation strategies proposed, of which the most encountered one is fumarate addition mechanism, generating alkylsuccinates as specific biomarkers. However, little is known about the mechanisms of anaerobic degradation of alkanes in oil reservoirs, due to low concentrations of signature metabolites and lack of mass spectral characteristics to allow identification. In this work, we used a multidisciplinary approach combining metabolite profiling and selective gene assays to establish the biodegradation mechanism of alkanes in oil reservoirs. A total of twelve production fluids from three different oil reservoirs were collected and treated with alkali; organic acids were extracted, derivatized with ethanol to form ethyl esters and determined using GC-MS analysis. Collectively, signature metabolite alkylsuccinates of parent compounds from C1 to C8 together with their (putative) downstream metabolites were detected from these samples. Additionally, metabolites indicative of the anaerobic degradation of mono- and poly-aromatic hydrocarbons (2-benzylsuccinate, naphthoate, 5,6,7,8-tetrahydro-naphthoate) were also observed. The detection of alkylsuccinates and genes encoding for alkylsuccinate synthase shows that anaerobic degradation of alkanes via fumarate addition occurs in oil reservoirs. This work provides strong evidence on the in situ anaerobic biodegradation mechanisms of hydrocarbons by fumarate addition. PMID:25966798

Chemical wiring and soldering toward all-molecule electronic circuitry.

Science.gov (United States)

Okawa, Yuji; Mandal, Swapan K; Hu, Chunping; Tateyama, Yoshitaka; Goedecker, Stefan; Tsukamoto, Shigeru; Hasegawa, Tsuyoshi; Gimzewski, James K; Aono, Masakazu

2011-06-01

Key to single-molecule electronics is connecting functional molecules to each other using conductive nanowires. This involves two issues: how to create conductive nanowires at designated positions, and how to ensure chemical bonding between the nanowires and functional molecules. Here, we present a novel method that solves both issues. Relevant functional molecules are placed on a self-assembled monolayer of diacetylene compound. A probe tip of a scanning tunneling microscope is then positioned on the molecular row of the diacetylene compound to which the functional molecule is adsorbed, and a conductive polydiacetylene nanowire is fabricated by initiating chain polymerization by stimulation with the tip. Since the front edge of chain polymerization necessarily has a reactive chemical species, the created polymer nanowire forms chemical bonding with an encountered molecular element. We name this spontaneous reaction "chemical soldering". First-principles theoretical calculations are used to investigate the structures and electronic properties of the connection. We demonstrate that two conductive polymer nanowires are connected to a single phthalocyanine molecule. A resonant tunneling diode formed by this method is discussed. © 2011 American Chemical Society

Adsorbent Alkali Conditioning for Uranium Adsorption from Seawater. Adsorbent Performance and Technology Cost Evaluation

International Nuclear Information System (INIS)

Tsouris, Costas; Mayes, Richard T.; Janke, Christopher James; Dai, Sheng; Das, S.; Liao, W.P.; Kuo, Li-Jung; Wood, Jordana; Gill, Gary; Byers, Maggie Flicker; Schneider, Eric

2015-01-01

The Fuel Resources program of the Fuel Cycle Research and Development program of the Office of Nuclear Energy (NE) is focused on identifying and implementing actions to assure that nuclear fuel resources are available in the United States. An immense source of uranium is seawater, which contains an estimated amount of 4.5 billion tonnes of dissolved uranium. This unconventional resource can provide a price cap and ensure centuries of uranium supply for future nuclear energy production. NE initiated a multidisciplinary program with participants from national laboratories, universities, and research institutes to enable technical breakthroughs related to uranium recovery from seawater. The goal is to develop advanced adsorbents to reduce the seawater uranium recovery technology cost and uncertainties. Under this program, Oak Ridge National Laboratory (ORNL) has developed a new amidoxime-based adsorbent of high surface area, which tripled the uranium capacity of leading Japanese adsorbents. Parallel efforts have been focused on the optimization of the physicochemical and operating parameters used during the preparation of the adsorbent for deployment. A set of parameters that need to be optimized are related to the conditioning of the adsorbent with alkali solution, which is necessary prior to adsorbent deployment. Previous work indicated that alkali-conditioning parameters significantly affect the adsorbent performance. Initiated in 2014, this study had as a goal to determine optimal parameters such as base type and concentration, temperature, and duration of conditioning that maximize the uranium adsorption performance of amidoxime functionalized adsorbent, while keeping the cost of uranium production low. After base-treatment at various conditions, samples of adsorbent developed at ORNL were tested in this study with batch simulated seawater solution of 8-ppm uranium concentration, batch seawater spiked with uranium nitrate at 75-100 ppb uranium, and continuous

Adsorbent Alkali Conditioning for Uranium Adsorption from Seawater. Adsorbent Performance and Technology Cost Evaluation

Energy Technology Data Exchange (ETDEWEB)

Tsouris, Costas [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Mayes, Richard T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Janke, Christopher James [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Dai, Sheng [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Das, S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Liao, W. -P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kuo, Li-Jung [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wood, Jordana [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gill, Gary [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Byers, Maggie Flicker [Univ. of Texas, Austin, TX (United States); Schneider, Eric [Univ. of Texas, Austin, TX (United States)

2015-09-30

The Fuel Resources program of the Fuel Cycle Research and Development program of the Office of Nuclear Energy (NE) is focused on identifying and implementing actions to assure that nuclear fuel resources are available in the United States. An immense source of uranium is seawater, which contains an estimated amount of 4.5 billion tonnes of dissolved uranium. This unconventional resource can provide a price cap and ensure centuries of uranium supply for future nuclear energy production. NE initiated a multidisciplinary program with participants from national laboratories, universities, and research institutes to enable technical breakthroughs related to uranium recovery from seawater. The goal is to develop advanced adsorbents to reduce the seawater uranium recovery technology cost and uncertainties. Under this program, Oak Ridge National Laboratory (ORNL) has developed a new amidoxime-based adsorbent of high surface area, which tripled the uranium capacity of leading Japanese adsorbents. Parallel efforts have been focused on the optimization of the physicochemical and operating parameters used during the preparation of the adsorbent for deployment. A set of parameters that need to be optimized are related to the conditioning of the adsorbent with alkali solution, which is necessary prior to adsorbent deployment. Previous work indicated that alkali-conditioning parameters significantly affect the adsorbent performance. Initiated in 2014, this study had as a goal to determine optimal parameters such as base type and concentration, temperature, and duration of conditioning that maximize the uranium adsorption performance of amidoxime functionalized adsorbent, while keeping the cost of uranium production low. After base-treatment at various conditions, samples of adsorbent developed at ORNL were tested in this study with batch simulated seawater solution of 8-ppm uranium concentration, batch seawater spiked with uranium nitrate at 75-100 ppb uranium, and continuous

Catalytic Hydrodeoxygenation of High Carbon Furylmethanes to Renewable Jet-fuel Ranged Alkanes over a Rhenium-Modified Iridium Catalyst.

Science.gov (United States)

Liu, Sibao; Dutta, Saikat; Zheng, Weiqing; Gould, Nicholas S; Cheng, Ziwei; Xu, Bingjun; Saha, Basudeb; Vlachos, Dionisios G

2017-08-24

Renewable jet-fuel-range alkanes are synthesized by hydrodeoxygenation of lignocellulose-derived high-carbon furylmethanes over ReO x -modified Ir/SiO 2 catalysts under mild reaction conditions. Ir-ReO x /SiO 2 with a Re/Ir molar ratio of 2:1 exhibits the best performance, achieving a combined alkanes yield of 82-99 % from C 12 -C 15 furylmethanes. The catalyst can be regenerated in three consecutive cycles with only about 12 % loss in the combined alkanes yield. Mechanistically, the furan moieties of furylmethanes undergo simultaneous ring saturation and ring opening to form a mixture of complex oxygenates consisting of saturated furan rings, mono-keto groups, and mono-hydroxy groups. Then, these oxygenates undergo a cascade of hydrogenolysis reactions to alkanes. The high activity of Ir-ReO x /SiO 2 arises from a synergy between Ir and ReO x , whereby the acidic sites of partially reduced ReO x activate the C-O bonds of the saturated furans and alcoholic groups while the Ir sites are responsible for hydrogenation with H 2 . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

First principles study of the adsorption of a NO molecule on N-doped anatase nanoparticles

International Nuclear Information System (INIS)

Liu Juan; Liu Qin; Fang Pengfei; Pan Chunxu; Xiao Wei

2012-01-01

The adsorption of a NO molecule on 72 atom N-doped TiO 2 nanoparticles has been studied by first principles calculations. Two types of adsorption are considered in the calculations. In one type of the adsorption, the NO molecule forms one bond with the particle, while in the other type of adsorption, the NO molecule forms two bonds with the particle. The second type of adsorption is more energetic favorable. The adsorption energies, bond lengths, density of the states (DOSs), and the difference of the charge density are calculated to investigate the adsorption. In the adsorption process, the unpaired electron of the NO molecule transfers to the empty state of the particle, making the Fermi levels lower. As a result, the electrons of the N-doped system occupy lower energy states, making the system energy lower than that of the undoped particle. Since the adsorption of a NO molecule on N-doped nanoparticles is stronger than that on undoped particles, N-doped particles can adsorb more NO molecules on their surfaces than the undoped particles do. Meanwhile, there are more adsorption sites on the N-doped particles, on which the adsorption energies are much higher than that of the undoped particle, some of them are even higher than the highest adsorption energy of the undoped particle. It suggests that N-doped particles are more active and they can adsorb more small toxic gas molecules in the air. So, the doping method can be used to remove NO molecules for the air pollution control through the surface adsorption strategy.

A new and selective cycle for dehydrogenation of linear and cyclic alkanes under mild conditions using a base metal

Science.gov (United States)

Solowey, Douglas P.; Mane, Manoj V.; Kurogi, Takashi; Carroll, Patrick J.; Manor, Brian C.; Baik, Mu-Hyun; Mindiola, Daniel J.

2017-11-01

Selectively converting linear alkanes to α-olefins under mild conditions is a highly desirable transformation given the abundance of alkanes as well as the use of olefins as building blocks in the chemical community. Until now, this reaction has been primarily the remit of noble-metal catalysts, despite extensive work showing that base-metal alkylidenes can mediate the reaction in a stoichiometric fashion. Here, we show how the presence of a hydrogen acceptor, such as the phosphorus ylide, when combined with the alkylidene complex (PNP)Ti=CHtBu(CH3) (PNP=N[2-P(CHMe2)2-4-methylphenyl]2-), catalyses the dehydrogenation of cycloalkanes to cyclic alkenes, and linear alkanes with chain lengths of C4 to C8 to terminal olefins under mild conditions. This Article represents the first example of a homogeneous and selective alkane dehydrogenation reaction using a base-metal titanium catalyst. We also propose a unique mechanism for the transfer dehydrogenation of hydrocarbons to olefins and discuss a complete cycle based on a combined experimental and computational study.

Accelerator Analysis of Tributyltin Adsorbed onto the Surface of a Tributyltin Resistant Marine Pseudoalteromonas sp. Cell

Directory of Open Access Journals (Sweden)

Akira Kitamura

2008-10-01

Full Text Available Tributyltin (TBT released into seawater from ship hulls is a stable marine pollutant and obviously remains in marine environments. We isolated a TBT resistant marine Pseudoalteromonas sp. TBT1 from sediment of a ship’s ballast water. The isolate (109.3 ± 0.2 colony-forming units mL-1 adsorbed TBT in proportion to the concentrations of TBTCl externally added up to 3 mM, where the number of TBT adsorbed by a single cell was estimated to be 108.2. The value was reduced to about one-fifth when the lysozyme-treated cells were used. The surface of ethanol treated cells became rough, but the capacity of TBT adsorption was the same as that for native cells. These results indicate that the function of the cell surface, rather than that structure, plays an important role to the adsorption of TBT. The adsorption state of TBT seems to be multi-layer when the number of more than 106.8 TBT molecules is adsorbed by a single cell.

Transient TAP approach to investigate adsorption and diffusion of small alkanes in porous sulfated zirconia

Energy Technology Data Exchange (ETDEWEB)

Galinsky, M.; Breitkopf, C. [Technische Univ. Dresden (Germany). Inst. fuer Energietechnik

2011-07-01

Sulfated zirconias have attracted an interest as catalysts due to their ability to isomerize alkanes at low temperatures, e.g., under thermodynamically favored conditions. However, the fast deactivation during the reaction remains a problem. To improve the catalytic performance of such porous catalysts, it is necessary to understand all steps in the catalytic cycle, namely diffusion and adsorption in more detail. The transient TAP method was applied to investigate sorption and diffusion phenomena of different alkanes in three different morphologically structured sulfated zirconias to elucidate their catalytic performances in the n-butane isomerization. New theoretical models were developed to describe the experimental results of TAP single-pulse experiments. The application of these models to pulse response curves allowed the extraction of adsorption and desorption rate constants as well as diffusion coefficients. Via introducing a second sorption center, the new adsorption model is able to reproduce the sorption behavior for larger alkanes quantitatively better than former models, especially in the low-temperature region. Moreover, the heterogeneous distribution of active centers was taken into account. Temperature dependent measurements have been performed to calculate heats of adsorption for various alkanes at the two assumed adsorption sites. The impact of these values on the catalytic properties is discussed. With the help of the new diffusion model, the diffusion coefficients for the inter- and intrapellet volume could be determined. These values are used in a numerical simulation to check whether the reaction rate for the isomerization at the investigated sulfated zirconias is diffusion limited. (orig.)

Transport properties of mixtures by the soft-SAFT + free-volume theory: application to mixtures of n-alkanes and hydrofluorocarbons.

Science.gov (United States)

Llovell, F; Marcos, R M; Vega, L F

2013-05-02

In a previous paper (Llovell et al. J. Phys. Chem. B, submitted for publication), the free-volume theory (FVT) was coupled with the soft-SAFT equation of state for the first time to extend the capabilities of the equation to the calculation of transport properties. The equation was tested with molecular simulations and applied to the family of n-alkanes. The capability of the soft-SAFT + FVT treatment is extended here to other chemical families and mixtures. The compositional rules of Wilke (Wilke, C. R. J. Chem. Phys. 1950, 18, 517-519) are used for the diluted term of the viscosity, while the dense term is evaluated using very simple mixing rules to calculate the viscosity parameters. The theory is then used to predict the vapor-liquid equilibrium and the viscosity of mixtures of nonassociating and associating compounds. The approach is applied to determine the viscosity of a selected group of hydrofluorocarbons, in a similar manner as previously done for n-alkanes. The soft-SAFT molecular parameters are taken from a previous work, fitted to vapor-liquid equilibria experimental data. The application of FVT requires three additional parameters related to the viscosity of the pure fluid. Using a transferable approach, the α parameter is taken from the equivalent n-alkane, while the remaining two parameters B and Lv are fitted to viscosity data of the pure fluid at several isobars. The effect of these parameters is then investigated and compared to those obtained for n-alkanes, in order to better understand their effect on the calculations. Once the pure fluids are well characterized, the vapor-liquid equilibrium and the viscosity of nonassociating and associating mixtures, including n-alkane + n-alkane, hydrofluorocarbon + hydrofluorocarbon, and n-alkane + hydrofluorocarbon mixtures, are calculated. One or two binary parameters are used to account for deviations in the vapor-liquid equilibrium diagram for nonideal mixtures; these parameters are used in a

Manipulation of polyatomic molecules with the scanning tunnelling microscope at room temperature: chlorobenzene adsorption and desorption from Si(111)-(7 x 7)

International Nuclear Information System (INIS)

Sloan, P A; Palmer, R E

2006-01-01

We report the imaging of chlorobenzene molecules chemisorbed on the Si(111)-(7 x 7) surface at room temperature with the scanning tunnelling microscope, and the desorption of the molecules by the tunnelling current. Detailed voltage-dependent imaging (at positive bias) allows the elucidation of the number and orientation of all the adsorbate configurations in the 7 x 7 unit cell. At negative bias the adsorbate was observed to affect the imaging properties of neighbouring half unit cells. The threshold voltage required for desorption of the chlorobenzene molecules was invariant to small changes in the tip-state, the adsorption site (corner adatom, middle adatom, faulted or unfaulted half of the unit cell) and the kind of doping of the substrate (n or p type)

Heritability of the Structures and 13C Fractionation in Tomato Leaf Wax Alkanes: A Genetic Model System to Inform Paleoenvironmental Reconstructions

Directory of Open Access Journals (Sweden)

Amanda L. D. Bender

2017-06-01

Full Text Available Leaf wax n-alkanes are broadly used to reconstruct paleoenvironmental information. However, the utility of n-alkanes as a paleoenvironmental proxy may be modulated by the extent to which biological as well as environmental factors influence the structural and isotopic variability of leaf waxes. In paleoclimate applications, there is usually an implicit assumption that most variation of leaf wax traits through a time series can be attributed to environmental change and that biological sources of variability within plant communities are small. For example, changes in hydrology affect the δ2H of waxes via rainwater and the δ13C of leaf waxes by changing plant communities. We measured the degree of genetic control over δ13C variation in leaf waxes within closely related species with an experimental greenhouse growth study. We measured the proportion of variability in structural and isotopic leaf wax traits that is attributable to genetic variation using a set of 76 introgression lines (ILs between two interfertile Solanum (tomato species: S. lycopersicum cv M82 (hereafter cv M82 and S. pennellii. Leaves of S. pennellii, a wild desert tomato relative, produced significantly more iso-alkanes than cv M82, a domesticated tomato cultivar adapted to water-replete conditions. We report a methylation index to summarize the ratio of branched (iso- and anteiso- to total alkanes. Between Solanum pennellii and cv M82, the iso-alkanes were found to be enriched in 13C by 1.2–1.4‰ over n-alkanes. The broad-sense heritability values (H2 of leaf wax traits describe the degree to which genetic variation contributes to variation of these traits. Variation of individual carbon isotopic compositions of alkanes were of low heritability (H2 = 0.13–0.19, suggesting that most variation in δ13C of leaf waxes in this study can be attributed to environmental variance. This supports the interpretation that variation in the δ13C of wax compounds recorded in sediments

Heritability of the structures and 13C fractionation in tomato leaf wax alkanes: a genetic model system to inform paleoenvironmental reconstructions

Science.gov (United States)

Bender, Amanda L. D.; Chitwood, Daniel H.; Bradley, Alexander S.

2017-06-01

Leaf wax n-alkanes are broadly used to reconstruct paleoenvironmental information. However, the utility of n-alkanes as a paleoenvironmental proxy may be modulated by the extent to which biological as well as environmental factors influence the structural and isotopic variability of leaf waxes. In paleoclimate applications, there is usually an implicit assumption that most variation of leaf wax traits through a time series can be attributed to environmental change and that biological sources of variability within plant communities are small. For example, changes in hydrology affect the δ2H of waxes via rainwater and the δ13C of leaf waxes by changing plant communities. We measured the degree of genetic control over δ13C variation in leaf waxes within closely related species with an experimental greenhouse growth study. We measured the proportion of variability in structural and isotopic leaf wax traits that is attributable to genetic variation using a set of 76 introgression lines (ILs) between two interfertile Solanum (tomato) species: S. lycopersicum cv M82 (hereafter cv M82) and S. pennellii. Leaves of S. pennellii, a wild desert tomato relative, produced significantly more iso-alkanes than cv M82, a domesticated tomato cultivar adapted to water-replete conditions. We report a methylation index to summarize the ratio of branched (iso- and anteiso-) to total alkanes. Between S. pennellii and cv M82, the iso-alkanes were found to be enriched in 13C by 1.2-1.4‰ over n-alkanes. The broad-sense heritability values (H2) of leaf wax traits describe the degree to which genetic variation contributes to variation of these traits. Variation of individual carbon isotopic compositions of alkanes were of low heritability (H2 = 0.13-0.19), suggesting that most variation in δ13C of leaf waxes in this study can be attributed to environmental variance. This supports the interpretation that variation in the δ13C of wax compounds recorded in sediments reflects

Surface Chirality of Gly-Pro Dipeptide Adsorbed on a Cu(110) Surface.

Science.gov (United States)

Cruguel, Hervé; Méthivier, Christophe; Pradier, Claire-Marie; Humblot, Vincent

2015-07-01

The adsorption of chiral Gly-Pro dipeptide on Cu(110) has been characterized by combining in situ polarization modulation infrared reflection absorption spectroscopy (PM-RAIRS) and X-ray photoelectron spectroscopy (XPS). The chemical state of the dipeptide, and its anchoring points and adsorption geometry, were determined at various coverage values. Gly-Pro molecules are present on Cu(110) in their anionic form (NH2 /COO(-)) and adsorb under a 3-point binding via both oxygen atoms of the carboxylate group and via the nitrogen atom of the amine group. Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) have shown the presence of an extended 2D chiral array, sustained via intermolecular H-bonds interactions. Furthermore, due to the particular shape of the molecule, only one homochiral domain is formed, creating thus a truly chiral surface. © 2015 Wiley Periodicals, Inc.

Theoretical Insight of Physical Adsorption for a Single-Component Adsorbent + Adsorbate System: I. Thermodynamic Property Surfaces

KAUST Repository

Chakraborty, Anutosh; Saha, Bidyut Baran; Ng, Kim Choon; Koyama, Shigeru; Srinivasan, Kandadai

2009-01-01

Thermodynamic property surfaces for a single-component adsorbent + adsorbate system are derived and developed from the viewpoint of classical thermodynamics, thermodynamic requirements of chemical equilibrium, Gibbs law, and Maxwell relations

Understanding Trends in Catalytic Activity: The Effect of Adsorbate-Adsorbate Interactions for CO Oxidation Over Transition Metals

DEFF Research Database (Denmark)

Grabow, Lars; Larsen, Britt Hvolbæk; Nørskov, Jens Kehlet

2010-01-01

Using high temperature CO oxidation as the example, trends in the reactivity of transition metals are discussed on the basis of density functional theory (DFT) calculations. Volcano type relations between the catalytic rate and adsorption energies of important intermediates are introduced...... and the effect of adsorbate-adsorbate interaction on the trends is discussed. We find that adsorbate-adsorbate interactions significantly increase the activity of strong binding metals (left side of the volcano) but the interactions do not change the relative activity of different metals and have a very small...... influence on the position of the top of the volcano, that is, on which metal is the best catalyst....

Plasma regeneration of mineral adsorbents for the precipitation of formaldehyde from exhaust gases of biogas engines; Plasmaregeneration mineralischer Adsorbentien zur Formaldehydabscheidung aus Abgasen von Biogas-Motoren

Energy Technology Data Exchange (ETDEWEB)

Mueller, Siegfried; Saulich, Katja [Leibniz-Institut fuer Plasmaforschung und Technologie, Greifswald (Germany); Schomburg, Joachim [DURTEC, Neubrandenburg (Germany)

2013-10-01

Formaldehyde.is a harmful ambient air pollutant which can be produced by incomplete combustion processes, e.g. in power plants or combustion engines. Adsorbents are widely applied in the area of cleaning as well as enrichment of gas components. In this study, we designed a bench-scale experiment to investigate a gas pollution treatment technique, which integrated the adsorption process and the plasma treatment for formaldehyde removal from gas streams. The mineral granulate used consisted of 80% halloysite and showed a good adsorption capacity for formaldehyde. In the discharge step, the adsorbed formaldehyde molecules were decomposed to CO{sub 2}, CO and hydrocarbons. For the further optimization of the method the influence of the power and the pulse break ratio of sustaining voltage were tested. Further the decomposition performance on adsorbed formaldehyde molecules was studied depending on space-time, a 10% oxygen fraction of the carrier gas, and the influence of temperature. It was shown that with the chosen plasma method the absorber material could be loaded repeatedly and subsequently regenerated at a low input discharge power. (orig.)

On determination of the dynamics of hydrocarbon molecules on catalyst's surfaces by means of neutron scattering

International Nuclear Information System (INIS)

Stockmeyer, R.

1976-01-01

The intensity distribution of slow neutrons scattered by adsorbed hydrocarbon molecules contains information on the dynamics of the molecules. In this paper the scattering law for incoherently scattering molecules is derived taking into account the very different mobility perpendicular and parallel to the surface. In contrast to the well known scattering law of threedimensionally diffusing particles the scattering law for twodimensional diffusion diverges logarithmically at zero energy transfer. Conclusions relevant to the interpretation of neutron scattering data are discussed. (orig.) [de

Spin- and energy-dependent tunneling through a single molecule with intramolecular spatial resolution.

Science.gov (United States)

Brede, Jens; Atodiresei, Nicolae; Kuck, Stefan; Lazić, Predrag; Caciuc, Vasile; Morikawa, Yoshitada; Hoffmann, Germar; Blügel, Stefan; Wiesendanger, Roland

2010-07-23

We investigate the spin- and energy-dependent tunneling through a single organic molecule (CoPc) adsorbed on a ferromagnetic Fe thin film, spatially resolved by low-temperature spin-polarized scanning tunneling microscopy. Interestingly, the metal ion as well as the organic ligand show a significant spin dependence of tunneling current flow. State-of-the-art ab initio calculations including also van der Waals interactions reveal a strong hybridization of molecular orbitals and substrate 3d states. The molecule is anionic due to a transfer of one electron, resulting in a nonmagnetic (S=0) state. Nevertheless, tunneling through the molecule exhibits a pronounced spin dependence due to spin-split molecule-surface hybrid states.

Nanospectroscopy of thiacyanine dye molecules adsorbed on silver nanoparticle clusters

Science.gov (United States)

Ralević, Uroš; Isić, Goran; Anicijević, Dragana Vasić; Laban, Bojana; Bogdanović, Una; Lazović, Vladimir M.; Vodnik, Vesna; Gajić, Radoš

2018-03-01

The adsorption of thiacyanine dye molecules on citrate-stabilized silver nanoparticle clusters drop-cast onto freshly cleaved mica or highly oriented pyrolytic graphite surfaces is examined using colocalized surface-enhanced Raman spectroscopy and atomic force microscopy. The incidence of dye Raman signatures in photoluminescence hotspots identified around nanoparticle clusters is considered for both citrate- and borate-capped silver nanoparticles and found to be substantially lower in the former case, suggesting that the citrate anions impede the efficient dye adsorption. Rigorous numerical simulations of light scattering on random nanoparticle clusters are used for estimating the electromagnetic enhancement and elucidating the hotspot formation mechanism. The majority of the enhanced Raman signal, estimated to be more than 90%, is found to originate from the nanogaps between adjacent nanoparticles in the cluster, regardless of the cluster size and geometry.

Radiation-induced transformations of isolated organic molecules in solid rare gas matrices

International Nuclear Information System (INIS)

Feldman, V.I.

1998-01-01

Complete text of publication follows. The studies of radiation-chemical behaviour of isolated organic molecules in rigid inert media are of considerable interest for radiation chemistry and general structural chemistry. Previous efforts were limited to the ESR studies of radicals resulting from some small hydrocarbon molecules in frozen rare gas solutions. Recently, we developed an approach to the radiation chemistry of isolated organic molecules using classic matrix isolation procedure for sample preparation and a combination of ESR and IR spectroscopy for characterization of paramagnetic and diamagnetic species resulting form electron irradiation or organic molecules in solid rare gas matrices at 10-15 K. The results obtained reveal high efficiency of energy transfer from rare gas matrix to organic molecules. The total radiation-chemical yields of degradation of organic molecules in argon and xenon matrices were measured directly by IR spectroscopy. The studies of the effect of electron scavengers on the radiolysis of organic molecules in solid rare gases show that the main primary process is positive hole transfer from matrix to additive molecule. ESR spectra of a number of radical cations (alkanes, ethers, arenes) were first characterized in a low-disturbing environment. It was found that the electronic characteristics (IP, polarizability) of the matrix used had crucial effect on trapping and degradation of primary organic radical cations. Using matrices with various IP provides an unique possibility to examine the chemical meaning of excess energy resulting from exothermic positive hole transfer, that is, to follow the fate of excited cations in condensed phase

Adherence of platelets to in situ albumin-binding surfaces under flow conditions: role of surface-adsorbed albumin

International Nuclear Information System (INIS)

Guha Thakurta, Sanjukta; Miller, Robert; Subramanian, Anuradha

2012-01-01

Surfaces that preferentially bind human serum albumin (HSA) were generated by grafting albumin-binding linear peptide (LP1) onto silicon surfaces. The research aim was to evaluate the adsorption pattern of proteins and the adhesion of platelets from platelet-poor plasma and platelet-rich plasma, respectively, by albumin-binding surfaces under physiological shear rate (96 and 319 s −1 ) conditions. Bound proteins were quantified using enzyme-linked immunosorbent assays (ELISAs) and two-dimensional gel electrophoresis. A ratio of ∼1000:100:1 of adsorbed HSA, human immunoglobulin (HIgG) and human fibrinogen (HFib) was noted, respectively, on LP1-functionalized surfaces, and a ratio of ∼5:2:1 of the same was noted on control surfaces, as confirmed by ELISAs. The surface-adsorbed von Willebrand factor was undetectable by sensitive ELISAs. The amount of adhered platelets correlated with the ratio of adsorbed HSA/HFib. Platelet morphology was more rounded on LP1-functionalized surfaces when compared to control surfaces. The platelet adhesion response on albumin-binding surfaces can be explained by the reduction in the co-adsorption of other plasma proteins in a surface environment where there is an excess of albumin molecules, coupled with restrictions in the conformational transitions of other surface-adsorbed proteins into hemostatically active forms. (paper)

Intramolecular charge separation in spirobifluorene-based donor–acceptor compounds adsorbed on Au and indium tin oxide electrodes

International Nuclear Information System (INIS)

Heredia, Daniel; Otero, Luis; Gervaldo, Miguel; Fungo, Fernando; Dittrich, Thomas; Lin, Chih-Yen; Chi, Liang-Chen; Fang, Fu-Chuan; Wong, Ken-Tsung

2013-01-01

Surface photovoltage (SPV) measurements were performed with a Kelvin-probe in spirobifluorene-based donor (diphenylamine)–acceptor (dicyano or cyanoacrylic acid moieties) compounds adsorbed from highly diluted solutions onto Au and indium tin oxide electrode surfaces. Strong intramolecular charge separation (negative SPV signals up to more than 0.1 V) due to directed molecule adsorption was observed only for spirobifluorene donor–acceptor compounds with carboxylic acid moiety. SPV signals and onset energies of electronic transitions depended on ambience conditions. - Highlights: ► Fluorene donor–acceptor derivatives were adsorbed at Au and indium tin oxide. ► Surface photovoltage measurements were performed with a Kelvin-probe. ► Strong intra-molecular charge separation was observed. ► SPV signals depended on ambience conditions

SERS and in situ SERS spectroscopy of riboflavin adsorbed on silver, gold and copper substrates. Elucidation of variability of surface orientation based on both experimental and theoretical approach

Science.gov (United States)

Dendisová-Vyškovská, Marcela; Kokaislová, Alžběta; Ončák, Milan; Matějka, Pavel

2013-04-01

Surface-enhanced Raman scattering and in situ surface-enhanced Raman scattering spectra have been collected to study influences of (i) used metal and (ii) applied electrode potential on orientation of adsorbed riboflavin molecules. Special in situ SERS spectroelectrochemical cell was used to obtain in situ SERS spectra of riboflavin adsorbed on silver, gold and copper nanostructured surfaces. Varying electrode potential was applied in discrete steps forming a cycle from positive values to negative and backward. Observed spectral features in in situ SERS spectra, measured at alternate potentials, have been changing very significantly and the spectra have been compared with SERS spectra of riboflavin measured ex situ. Raman spectra of single riboflavin molecule in the vicinity to metal (Ag, Au and Cu) clusters have been calculated for different mutual positions. The results demonstrate significant changes of bands intensities which can be correlated with experimental spectra measured at different potentials. Thus, the orientation of riboflavin molecules adsorbed on metal surfaces can be elucidated. It is influenced definitely by the value of applied potential. Furthermore, the riboflavin adsorption orientation on the surface depends on the used metal. Adsorption geometries on the copper substrates are more diverse in comparison with the orientations on silver and gold substrates.

Mercury adsorption properties of sulfur-impregnated adsorbents

Science.gov (United States)

Hsi, N.-C.; Rood, M.J.; Rostam-Abadi, M.; Chen, S.; Chang, R.

2002-01-01

Carbonaceous and noncarbonaceous adsorbents were impregnated with elemental sulfur to evaluate the chemical and physical properties of the adsorbents and their equilibrium mercury adsorption capacities. Simulated coal combustion flue gas conditions were used to determine the equilibrium adsorption capacities for Hg0 and HgCl2 gases to better understand how to remove mercury from gas streams generated by coal-fired utility power plants. Sulfur was deposited onto the adsorbents by monolayer surface deposition or volume pore filling. Sulfur impregnation increased the total sulfur content and decreased the total and micropore surface areas and pore volumes for all of the adsorbents tested. Adsorbents with sufficient amounts of active adsorption sites and sufficient microporous structure had mercury adsorption capacities up to 4,509 ??g Hg/g adsorbent. Elemental sulfur, organic sulfur, and sulfate were formed on the adsorbents during sulfur impregnation. Correlations were established with R2>0.92 between the equilibrium Hg0/HgCl2 adsorption capacities and the mass concentrations of elemental and organic sulfur. This result indicates that elemental and organic sulfur are important active adsorption sites for Hg0 and HgCl2.

Single NdPc{sub 2} molecules on surfaces. Adsorption, interaction, and molecular magnetism

Energy Technology Data Exchange (ETDEWEB)

Fahrendorf, Sarah

2013-01-24

They have huge potential for application in molecular-spin-transistors, molecular-spinvalves, and molecular quantum computing. SMMs are characterized by high spin ground states with zero-field splitting leading to high relaxation barriers and long relaxation times. A relevant class of molecules are the lanthanide double-decker phthalocyanines (LaPc{sub 2}) with only one metal atom sandwiched between two organic phthalocyanine (Pc) ligands. For envisaged spintronic applications it is important to understand the interaction between the molecules and the substrate and its influence on the electronic and magnetic properties. The subject of this thesis is the investigation of the adsorbed neodymium double-decker phthalocyanine (NdPc{sub 2}) by means of low temperature scanning tunneling microscopy and spectroscopy (STM and STS). The molecules are deposited by sublimation onto different substrates. It is observed that a large fraction of the double-decker molecules decomposes during deposition. The decomposition probability strongly depends on the chosen substrate. Therefore it is concluded that the substrate modifies the electronic structure of the molecule leading to a stabilization or destabilization of the molecular entity. Charge transfer from the surface to the molecule is identified as a potential stabilizing mechanism. The electronic and magnetic properties are investigated in detail for adsorbed NdPc{sub 2} molecules on Cu(100). The results of the experimental study are compared to state-of-the-art density functional theory calculations performed by our colleagues from the Peter Gruenberg Institute (PGI-1) at the Forschungszentrum Juelich. Interestingly, the lower Pc ring of the molecule hybridizes intensely with the substrate leading to strong chemisorption of the molecule, while the upper Pc ring keeps its molecular type electronic states, which can be energetically shifted by an external electric field. Importantly, it is possible to get direct access to the

Method for modifying trigger level for adsorber regeneration

Science.gov (United States)

Ruth, Michael J.; Cunningham, Michael J.

2010-05-25

A method for modifying a NO.sub.x adsorber regeneration triggering variable. Engine operating conditions are monitored until the regeneration triggering variable is met. The adsorber is regenerated and the adsorbtion efficiency of the adsorber is subsequently determined. The regeneration triggering variable is modified to correspond with the decline in adsorber efficiency. The adsorber efficiency may be determined using an empirically predetermined set of values or by using a pair of oxygen sensors to determine the oxygen response delay across the sensors.

X-ray emission spectroscopy applied to glycine adsorbed on Cu(110): An atom and symmetry projected view

Energy Technology Data Exchange (ETDEWEB)

Hasselstroem, J.; Karis, O.; Weinelt, M. [Uppsala Univ. (Sweden)] [and others

1997-04-01

When a molecule is adsorbed on a metal surface by chemical bonding new electronic states are formed. For noble and transition metals these adsorption-induced states overlap with the much more intense metal d-valence band, making them difficult to probe by for instance direct photoemission. However, it has recently been shown that X-ray emission spectroscopy (XES) can be applied to adsorbate systems. Since the intermediate state involves a core hole, this technique has the power to project out the partial density of states around each atomic site. Both the excitation and deexcitation processes are in general governed by the dipole selection rules. For oriented system, it is hence possible to obtain a complete separation into 2p{sub x}, 2p{sub y} and 2p{sub z} contributions using angular resolved measurements. The authors have applied XES together with other core level spectroscopies to glycine adsorption on Cu(110). Glycine (NH{sub 2}CH{sub 2}COOH) is the smallest amino acid and very suitable to study by core level spectroscopy since it has several functional groups, all well separated in energy by chemical shifts. Its properties are futhermore of biological interest. In summary, the authors have shown that it is possible to apply XES to more complicated molecular adsorbates. The assignment of different electronic states is however not as straight forward as for simple diatomic molecules. For a complete understanding of the redistribution and formation of new electronic states associated with the surface chemical bond, experimental data must be compared to theoretical calculations.

A novel fiber-based adsorbent technology

Energy Technology Data Exchange (ETDEWEB)

Reynolds, T.A. [Chemica Technologies, Inc., Bend, OR (United States)

1997-10-01

In this Phase I Small Business Innovation Research program, Chemica Technologies, Inc. is developing an economical, robust, fiber-based adsorbent technology for removal of heavy metals from contaminated water. The key innovation is the development of regenerable adsorbent fibers and adsorbent fiber cloths that have high capacity and selectivity for heavy metals and are chemically robust. The process has the potential for widespread use at DOE facilities, mining operations, and the chemical process industry.

Conversion of raw lignocellulosic biomass into branched long-chain alkanes through three tandem steps.

Science.gov (United States)

Li, Chunrui; Ding, Daqian; Xia, Qineng; Liu, Xiaohui; Wang, Yanqin

2016-07-07

Synthesis of branched long-chain alkanes from renewable biomass has attracted intensive interest in recent years, but the feedstock for this synthesis is restricted to platform chemicals. Here, we develop an effective and energy-efficient process to convert raw lignocellulosic biomass (e.g., corncob) into branched diesel-range alkanes through three tandem steps for the first time. Furfural and isopropyl levulinate (LA ester) were prepared from hemicellulose and cellulose fractions of corncob in toluene/water biphasic system with added isopropanol, which was followed by double aldol condensation of furfural with LA ester into C15 oxygenates and the final hydrodeoxygenation of C15 oxygenates into branched long-chain alkanes. The core point of this tandem process is the addition of isopropanol in the first step, which enables the spontaneous transfer of levulinic acid (LA) into the toluene phase in the form of LA ester through esterification, resulting in LA ester co-existing with furfural in the same phase, which is the basis for double aldol condensation in the toluene phase. Moreover, the acidic aqueous phase and toluene can be reused and the residues, including lignin and humins in aqueous phase, can be separated and carbonized to porous carbon materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Degradability of n-alkanes during ex situ natural bioremediation of soil contaminated by heavy residual fuel oil (mazut

Directory of Open Access Journals (Sweden)

Ali Ramadan Mohamed Muftah

2013-01-01

Full Text Available It is well known that during biodegradation of oil in natural geological conditions, or oil pollutants in the environment, a degradation of hydrocarbons occurs according to the well defined sequence. For example, the major changes during the degradation process of n-alkanes occur in the second, slight and third, moderate level (on the biodegradation scale from 1 to 10. According to previous research, in the fourth, heavy level, when intensive changes of phenanthrene and its methyl isomers begin, n-alkanes have already been completely removed. In this paper, the ex situ natural bioremediation (unstimulated bioremediation, without addition of biomass, nutrient substances and biosurfactant of soil contaminated with heavy residual fuel oil (mazut was conducted during the period of 6 months. Low abundance of n-alkanes in the fraction of total saturated hydrocarbons in the initial sample (identification was possible only after concentration by urea adduction technique showed that the investigated oil pollutant was at the boundary between the third and the fourth biodegradation level. During the experiment, an intense degradation of phenanthrene and its methyl-, dimethyl-and trimethyl-isomers was not followed by the removal of the remaining n-alkanes. The abundance of n-alkanes remained at the initial low level, even at end of the experiment when the pollutant reached one of the highest biodegradation levels. These results showed that the unstimulated biodegradation of some hydrocarbons, despite of their high biodegradability, do not proceed completely to the end, even at final degradation stages. In the condition of the reduced availability of some hydrocarbons, microorganisms tend to opt for less biodegradable but more accessible hydrocarbons.

Novel Fiber-Based Adsorbent Technology; FINAL

International Nuclear Information System (INIS)

Nixon, P.G.; Tsukamoto, T.; Brose, D.J.

2001-01-01

The overall of this Department of Energy (DOE) Phase II SBIR program was to develop a new class of highly robust fiber-based adsorbents for recovery of heavy metals from aqueous waste-streams. The fiber-based adsorbents,when commercialized,will be used for clean up metals in aqueous waste-streams emanating from DOE facilities,industry,mining,and groundwater-cleanup operations.The amount of toxic waste released by these streams is of great significance.The U.S.Environment Protection Agency (EPA) reports that in 1990 alone,4.8 billion pounds of toxic chemicals were released into the environment.Of this waste,the metals-containing waste was the second largest contributor,representing 569 million pounds. This report presents the results of the Phase II program,which successfully synthesized noval fiber-based adsorbents for the removal of Group 12 metals(i.e.mercury),Group 14 metals (lead),and Group 10 metals(platinum and palladium) from contaminated groundwater and industrial waste streams.These fiber-based adsorbents are ideally suited for the recovery of metal ions from aqueous waste streams presently not treatable due to the degrading nature of corrosive chemicals or radioactive components in the feed stream. The adsorbents developed in this program rely on chemically resistant and robust carbon fibers and fabrics as supports for metal-ion selective ligands.These adsorbents demonstrate loading capacities and selectivities for metal ions exceeding those of conventional ion-exchange resins.The adsorbents were also used to construct filter modules that demonstrate minimal fouling,minimal compaction,chemical and physical robustness,and regeneration of metal loading capacity without loss of performance

Pd/NbOPO₄ multifunctional catalyst for the direct production of liquid alkanes from aldol adducts of furans.

Science.gov (United States)

Xia, Qi-Neng; Cuan, Qian; Liu, Xiao-Hui; Gong, Xue-Qing; Lu, Guan-Zhong; Wang, Yan-Qin

2014-09-08

Great efforts have been made to convert renewable biomass into transportation fuels. Herein, we report the novel properties of NbO(x)-based catalysts in the hydrodeoxygenation of furan-derived adducts to liquid alkanes. Excellent activity and stability were observed with almost no decrease in octane yield (>90% throughout) in a 256 h time-on-stream test. Experimental and theoretical studies showed that NbO(x) species play the key role in C-O bond cleavage. As a multifunctional catalyst, Pd/NbOPO4 plays three roles in the conversion of aldol adducts into alkanes: 1) The noble metal (in this case Pd) is the active center for hydrogenation; 2) NbO(x) species help to cleave the C-O bond, especially of the tetrahydrofuran ring; and 3) a niobium-based solid acid catalyzes the dehydration, thus enabling the quantitative conversion of furan-derived adducts into alkanes under mild conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Acidic ionic liquids for n-alkane isomerization in a liquid-liquid or slurry-phase reaction mode

Energy Technology Data Exchange (ETDEWEB)

Meyer, C.; Hager, V.; Geburtig, D.; Kohr, C.; Wasserscheid, P. [Erlangen-Nuernberg Univ. (Germany). Lehrstuhl fuer Chemische Reaktionstechnik; Haumann, M. [Chemical Reaction Engineering, FAU Busan Campus, Korea (Korea, Republic of)

2011-07-01

Highly acidic ionic liquid (IL) catalysts offer the opportunity to convert n-alkanes at very low reaction temperatures. The results of IL catalyzed isomerization and cracking reactions of pure n-octane are presented. Influence of IL composition, [C{sub 4}C{sub 1}Im]Cl / AlCl{sub 3} / H{sub 2}SO{sub 4} and [C{sub 4}C{sub 1}Im]Cl / AlCl{sub 3} / 1-chlorooctane, on catalyst activity and selectivities to branched alkanes was investigated. Acidic chloroaluminate IL catalysts form liquid-liquid biphasic systems with unpolar organic product mixtures. Thus, recycling of the acidic IL is enabled by simple phase separation in the liquid-liquid biphasic reaction mode or the IL can be immobilized on an inorganic support with a large specific surface area. These supported ionic liquid phase (SILP) catalysts offer the advantage to get a macroscopically heterogeneous system while still preserving all benefits of the homogeneous catalyst which can be used for the slurry-phase n-alkane isomerization. The interaction of the solid support and acidic IL influences strongly the catalytic activity. (orig.)

WGS-Adsorbent Reaction Studies at Laboratory Scale

International Nuclear Information System (INIS)

Marano, M.; Torreiro, Y.

2014-01-01

This document reports the most significant results obtained during the experimental work performed under task WGS adsorbent experimental studies within CAPHIGAS project (National Research Plan 2008-2011, ref: ENE2009-08002). The behavior of the binary adsorbent-catalyst system which will be used in the hybrid system is described in this document. Main results reported here were used during the design and development of the hybrid system adsorbent catalyst- membrane proposed in the CAPHIGAS project. The influence of main operating parameters and the optimized volume ratio adsorbent-catalyst are also presented in this report. (Author)

Seasonal variation of the particle size distribution of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) in urban aerosol of Guangzhou, China.

Science.gov (United States)

Tang, X L; Bi, X H; Sheng, G Y; Tan, J H; Fu, J M

2006-06-01

Seasonal aerosol samples have been collected by Andersen Hi-Vol pumping system equipped with a five stage cascade impactor and a backup filter (size range: 10-7.2 microm, 7.2-3.0 microm, 3.0-1.5 microm, 1.5-0.95 microm, 0.95-0.49 microm, gas chromatography and PAHs were measured using gas chromatography/mass spectrometry analysis. The bimodal log-normal distributions of n-alkanes and semi-volatile PAHs were found, while for non-volatile PAHs that was unimodal, so much as the mode of semi-volatile PAHs was similar with that of the particles. The n-alkanes and PAHs were preferably associated with fine particles. C (max) (carbon number maximum) (C(22)-C(26)), CPI (carbon preference index) (1.12-1.21), U/R (unresolved to resolved components ratio) (7.42-10.7), wax% (0.9-3.12%) and the diagnostic ratios for PAHs revealed that vehicular emission was the major source of these organic compounds during the study periods, while the contribution of epicuticular waxes emitted by terrestrial plants was minor. CPI(2) (values for petrogenic hydrocarbons), CPI(3) (values for biogenic n-alkanes) and wax% revealed that the natural preferentially accumulated in the larger aerosol while the anthropogenic in the smaller. In addition, the different MMDs (mass median diameters) for n-alkanes and PAHs were observed in different seasons. The MMDs for n-alkanes and PAHs were higher in autumn/winter than those in spring/summer. The seasonal effect was related to the hydrocarbon content in the individual particulate fractions, showing a preferential association of n-alkanes and PAHs with larger particles in the autumn/winter season.

First-principles study of SF_6 decomposed gas adsorbed on Au-decorated graphene

International Nuclear Information System (INIS)

Zhang, Xiaoxing; Yu, Lei; Gui, Yingang; Hu, Weihua

2016-01-01

Graphical abstract: - Highlights: • We theoretically investigated the decomposed gaseous components of sulfur hexafluoride (SF_6), namely, H_2S, SO_2, SOF_2, and SO_2F_2, adsorbed on pristine and Au-embedded graphene based on DFT-D, in which the van der Waals effect is considered. • H_2S, SO_2, SOF_2, and SO_2F_2 are chemisorption on Au-doped graphene, appreciably stronger than physisorption on pristine graphene in which the van der Waals dominates. • Only H_2S exhibits n-type doping to Au-graphene, whereas the rest gases exhibit p-type doping. The n-type and p-type sensing behaviors that Au-doped graphene displays to different gases play a crucial role in selective sensing application. • Magnetic moments fluctuate substantially in the original Au-graphene when H_2S and SO_2 are adsorbed. While the adsorption effects of SOF_2 and SO_2F_2 generate magnetism quenching. The different changes of magnetic moments in every adsorption system provide another approach to selective detection. • The charge transfer mechanism is deeply discussed in this paper. - Abstract: We theoretically investigated the decomposed gaseous components of sulfur hexafluoride (SF_6), namely, H_2S, SO_2, SOF_2, and SO_2F_2, adsorbed on pristine and Au-embedded graphene based on the revised Perdew–Burke–Ernzerhof calculation, which empirically includes a dispersion correction (DFT-D) for van der Waals interaction with standard generalized gradient approximation. Pristine graphene exhibits weak adsorption and absence of charge transfer, which indicates barely satisfactory sensing for decomposed components. The Au atom introduces magnetism to the pristine graphene after metal-embedded decoration as well as enhances conductivity. All four molecules induce certain hybridization between the molecules and Au-graphene, which results in chemical interactions. SOF_2 and SO_2F_2 exhibit a strong chemisorption interaction with Au-graphene, while H_2S and SO_2 exhibit quasi-molecular binding

Volumetric interpretation of protein adsorption: interfacial packing of protein adsorbed to hydrophobic surfaces from surface-saturating solution concentrations.

Science.gov (United States)

Kao, Ping; Parhi, Purnendu; Krishnan, Anandi; Noh, Hyeran; Haider, Waseem; Tadigadapa, Srinivas; Allara, David L; Vogler, Erwin A

2011-02-01

The maximum capacity of a hydrophobic adsorbent is interpreted in terms of square or hexagonal (cubic and face-centered-cubic, FCC) interfacial packing models of adsorbed blood proteins in a way that accommodates experimental measurements by the solution-depletion method and quartz-crystal-microbalance (QCM) for the human proteins serum albumin (HSA, 66 kDa), immunoglobulin G (IgG, 160 kDa), fibrinogen (Fib, 341 kDa), and immunoglobulin M (IgM, 1000 kDa). A simple analysis shows that adsorbent capacity is capped by a fixed mass/volume (e.g. mg/mL) surface-region (interphase) concentration and not molar concentration. Nearly analytical agreement between the packing models and experiment suggests that, at surface saturation, above-mentioned proteins assemble within the interphase in a manner that approximates a well-ordered array. HSA saturates a hydrophobic adsorbent with the equivalent of a single square or hexagonally-packed layer of hydrated molecules whereas the larger proteins occupy two-or-more layers, depending on the specific protein under consideration and analytical method used to measure adsorbate mass (solution depletion or QCM). Square or hexagonal (cubic and FCC) packing models cannot be clearly distinguished by comparison to experimental data. QCM measurement of adsorbent capacity is shown to be significantly different than that measured by solution depletion for similar hydrophobic adsorbents. The underlying reason is traced to the fact that QCM measures contribution of both core protein, water of hydration, and interphase water whereas solution depletion measures only the contribution of core protein. It is further shown that thickness of the interphase directly measured by QCM systematically exceeds that inferred from solution-depletion measurements, presumably because the static model used to interpret solution depletion does not accurately capture the complexities of the viscoelastic interfacial environment probed by QCM. Copyright © 2010

Nucleation, growth and habit modification of n-alkanes and homologous mixtures in the absence and presence of flow improving additives

International Nuclear Information System (INIS)

Taggart, Audrey M.

1996-01-01

A detailed study has been performed on the nucleation, growth and habit modification of n-alkanes and homologous mixtures in the absence and presence of flow improving additives in an attempt to gain a clearer appreciation of the interaction mechanisms behind wax / additive crystallisation. Kinetic and structural assessment of melt phase n-alkanes illustrate the different crystallographic forms present within the homologous series. Studies demonstrate the alternating behaviour of the even and odd numbered homologues which converges as a function of increasing molecular weight. Greater crystal lattice stabilities were found for those n-alkanes which have an even carbon number and which crystallise into the triclinic crystal structure. Solid state phase behaviour of the n-alkanes was found to vary depending on the number and parity of n. Nucleation kinetic studies of n-alkanes and homologous mixtures from model diesel fuel solvents (dodecane, m-xylene, decalin, pristane and a dewaxed fuel) are assessed using turbidity as the method of crystallite detection. Saturation temperatures are found to be related to both alkane structure and molecular chain length for all solvent systems. N-alkane solubilities are lower for n-alkane like solvents. The width of the meta stable zone varies as a function of solvent in order of dodecane ≅ pristane 19 H 40 and solvent m-xylene. Wax precipitation from distillate fuels in the presence of flow improving additives (di-alkyl di-amino xylene, phthalic acid and sulphobenzene acid derivatives and high molecular weight polymers) reveal responsive wax crystal nucleator and growth inhibitor additives. The crystal morphology of heptacosane, C 27 H 56 to simulate a model wax crystal is assessed in addition to its response to blocker 'tailor made' additives: methyl substituted C 27 H 56 and di-alkyl substituted phenyl additives [additive (A) and (B)]. Pure C 27 H 56 reveals a thin lozenge shaped platelet. All additives studied induce growth

In-situ quartz crystal microgravimetric studies of molecular adsorbates containing thiol and hydroquinone moieties bound to Au(111) surfaces in aqueous electrolytes

Energy Technology Data Exchange (ETDEWEB)

Mo, Y.; Sukenik, C.; Sandifer, M. [Case Western Univ., Cleveland, OH (United States); Barriga, R.J.; Soriaga, M.P.; Scherson, D. [Texas A& M Univ., College Station, TX (United States)

1995-12-01

The microgravimetric properties of monolayers of 2, 5-dihydroxythiophenol, 2,5-dihydroxybenzyl mercaptan, and 2, 5-dihydroxy-4-methylbenzyl mercaptan adsorbed on Au(111) single crystal electrodes were examined by in situ quartz crystal microbalance techniques in aqueous perchloric acid electrolytes. The results obtained are consistent with the reversible loss of an average of about three waters per adsorbed molecule as the layers are oxidized and subsequently reduced. These observations provide evidence for discrete changes in the extent of bound water within the hydroquinone/quinone layer as the oxidation state of the monolayer is changed. 9 refs., 4 figs.

Transport mechanisms and wetting dynamics in molecularly thin films of long-chain alkanes at solid/vapour interface : relation to the solid-liquid phase transition

OpenAIRE

Lazar, Paul

2005-01-01

Wetting and phase transitions play a very important role our daily life. Molecularly thin films of long-chain alkanes at solid/vapour interfaces (e.g. C30H62 on silicon wafers) are very good model systems for studying the relation between wetting behaviour and (bulk) phase transitions. Immediately above the bulk melting temperature the alkanes wet partially the surface (drops). In this temperature range the substrate surface is covered with a molecularly thin ordered, solid-like alkane film (...

Formation of C-C and C-O bonds and oxygen removal in reactions of alkanediols, alkanols, and alkanals on copper catalysts.

Science.gov (United States)

Sad, María E; Neurock, Matthew; Iglesia, Enrique

2011-12-21

This study reports evidence for catalytic deoxygenation of alkanols, alkanals, and alkanediols on dispersed Cu clusters with minimal use of external H(2) and with the concurrent formation of new C-C and C-O bonds. These catalysts selectively remove O-atoms from these oxygenates as CO or CO(2) through decarbonylation or decarboxylation routes, respectively, that use C-atoms present within reactants or as H(2)O using H(2) added or formed in situ from CO/H(2)O mixtures via water-gas shift. Cu catalysts fully convert 1,3-propanediol to equilibrated propanol-propanal intermediates that subsequently form larger oxygenates via aldol-type condensation and esterification routes without detectable involvement of the oxide supports. Propanal-propanol-H(2) equilibration is mediated by their chemisorption and interconversion at surfaces via C-H and O-H activation and propoxide intermediates. The kinetic effects of H(2), propanal, and propanol pressures on turnover rates, taken together with measured selectivities and the established chemical events for base-catalyzed condensation and esterification reactions, indicate that both reactions involve kinetically relevant bimolecular steps in which propoxide species, acting as the base, abstract the α-hydrogen in adsorbed propanal (condensation) or attack the electrophilic C-atom at its carbonyl group (esterification). These weakly held basic alkoxides render Cu surfaces able to mediate C-C and C-O formation reactions typically catalyzed by basic sites inherent in the catalyst, instead of provided by coadsorbed organic moieties. Turnover rates for condensation and esterification reactions decrease with increasing Cu dispersion, because low-coordination corner and edge atoms prevalent on small clusters stabilize adsorbed intermediates and increase the activation barriers for the bimolecular kinetically relevant steps required for both reactions. © 2011 American Chemical Society

Selective adsorption and release of cationic organic dye molecules on mesoporous borosilicates

International Nuclear Information System (INIS)

Paul, Manidipa; Pal, Nabanita; Bhaumik, Asim

2012-01-01

Mesoporous materials can play a pivotal role as a host material for delivery application to a specific part of a system. In this work we explore the selective adsorption and release of cationic organic dye molecules such as safranine T (ST) and malachite green (MG) on mesoporous borosilicate materials. The mesoporous silica SBA-15 and borosilicate materials (MBS) were prepared using non-ionic surfactant Pluronic P123 as template via evaporation induced self-assembly (EISA) method. After template removal the materials show high surface areas and in some cases ordered mesopores of dimensions ca. 6–7 nm. High surface area, mesoporosity and the presence of heteroatom (boron) help this mesoporous borosilicate material to adsorb high amount of cationic dye molecules at its surface from the respective aqueous solutions. Furthermore, the mesoporous borosilicate samples containing higher percentage adsorbed dyes show excellent release of ST or MG dye in simulated body fluid (SBF) solution at physiological pH = 7.4 and temperature 310 K. The adsorption and release efficiency of mesoporous borosilicate samples are compared with reference boron-free mesoporous pure silica material to understand the nature of adsorbate–adsorbent interaction at the surfaces. - Graphical abstract: Highly ordered 2D-hexagonal mesoporous borosilicate materials have been synthesized by using Pluronic P123 as template. The materials show very good adsorption and release of organic cationic dye molecules under physiological conditions. Highlights: ► Highly ordered 2D-hexagonal mesoporous borosilicate. ► Nonionic Pluoronic P123 templated mesoporous material. ► Adsorption of organic dyes at the mesopore surface. ► Controlled release of dyes under physiological pH and temperature. ► Release of safranine T (ST) and malachite green (MG) dyes in simulated body fluids.

Dissolved Air Flotation of arsenic adsorbent particles

Directory of Open Access Journals (Sweden)

Mario Enrique Santander Muñoz

2015-01-01

Full Text Available The removal of arsenic from synthetic effluent was studied using the adsorbent particle flotation technique (APF and dissolved air flotation (DAF. A sample of an iron mineral was used as adsorbent particles of arsenic, ferric chloride as coagulant, cationic poly-acrylamide (NALCO 9808 as flocculants, and sodium oleate as collector. Adsorption studies to determine the pH influence, contact time, and adsorbent particles concentration on the adsorption of arsenic were carried out along with flotation studies to determine the removal efficiency of adsorbents particles. The results achieved indicate that the adsorption kinetic of arsenic is very rapid and that in range of pH’s from 2 to 7 the adsorption percentages remain constant. The equilibrium conditions were achieved in 60 minutes and about 95% of arsenic was adsorbed when used an adsorbent concentration of 2 g/L and pH 6.3. The maximum adsorption capacity of adsorbent particles was 4.96 mg/g. The mean free energy of adsorption (E was found to be 2.63 kJ/mol, which suggests physisorption. The results of the flotation studies demonstrated that when synthetic effluents with 8.9 mg/L of arsenic were treated under the following experimental conditions; 2 g/L of adsorbent particles, 120 mg/L of Fe(III, 2 mg/L of Nalco 9808, 20 mg/L of sodium oleate, and 40% of recycle ratio in the DAF, it was possible to reach 98% of arsenic removal and 6.3 NTU of residual turbidity in clarified synthetic effluent.

Krypton retention on solid adsorbents

International Nuclear Information System (INIS)

Monson, P.R. Jr.

1982-01-01

An experimental laboratory program was conducted to develop economical solid adsorbents for the retention of krypton from a dissolver off-gas stream. The study indicates that a solid adsorbent system is feasible and competitive with other developing systems which utilize fluorocarbon absorption nd cryogenic distillation. This technology may have potential applications not only in nuclear fuel reprocessing plants, but also in nuclear reactors and in environmental monitoring. Of the 13 prospective adsorbents evaluated with respect to adsorption capacity and cost, the commercially available hydrogen mordenite was the most cost-effective material at subambient temperatures (-40 0 to -80 0 C). Silver mordenite has a higher capacity for krypton retention, but is 50 times more expensive than hydrogen mordenite

Raman spectroscopy of adsorbed water in clays: first attempt at band assignment

Energy Technology Data Exchange (ETDEWEB)

Ligny, Dominique de; Guillaud, Emmanuel [Institut Lumiere Matiere, CNRS, Universite Lyon 1, 12 rue Ada Byron, 69622 Villeurbanne (France); Gailhanou, Helene; Blanc, Philippe [BRGM, Service D3E, 3 avenue Claude Guillemin, 45000 Orleans (France)

2013-07-01

Raman spectroscopy can be a useful tool to determine water content within clays, or even in highly saturated solutions. The following assignment is proposed for the OH region of SAz-2: the two large bands at 3260 and 3475 cm{sup -1} are assigned to water in pores, the first one to water molecules coordinated to the interlayer cations, and the second one to structural Al-OH groups The band at 3600 cm{sup -1} is therefore more likely related to adsorbed water on the clay surface. Simple intensity ratios of these different bands give good estimates of water content. (authors)

Determination of molecular diffusion coefficient in n-alkane binary mixtures: empirical correlations.

Science.gov (United States)

De Mezquia, D Alonso; Bou-Ali, M Mounir; Larrañaga, M; Madariaga, J A; Santamaría, C

2012-03-08

In this work we have measured the molecular diffusion coefficient of the n-alkane binary series nC(i)-nC(6), nC(i)-nC(10), and nC(i)-nC(12) at 298 K and 1 atm and a mass fraction of 0.5 by using the so-called sliding symmetric tubes technique. The results show that the diffusion coefficient at this concentration is proportional to the inverse viscosity of the mixture. In addition, we have also measured the diffusion coefficient of the systems nC(12)-nC(6), nC(12)-nC(7), and nC(12)-nC(8) as a function of concentration. From the data obtained, it is shown that the diffusion coefficient of the n-alkane binary mixtures at any concentration can be calculated from the molecular weight of the components and the dynamic viscosity of the corresponding mixture at 50% mass fraction.

Light alkane (mixed feed selective dehydrogenation using bi-metallic zeolite supported catalyst

Directory of Open Access Journals (Sweden)

Zeeshan Nawaz

2009-12-01

Full Text Available Light alkanes are the important intermediates of many refinery processes and their catalytic dehydrogenation gives corresponding alkenes. The aim behind this experimentation is to investigate reaction behavior of mixed alkanes during direct catalytic dehydrogenation and emphasis has been given to enhance propene. Bi-metallic zeolite supported catalyst Pt-Sn/ZSM-5 was prepared by sequentional impregnation method and characterized by BET, EDS and XRD. Direct dehydrogenation reaction is highly endothermic and its conversion is thermodynamically limited. Results showed that the increase in temperature increases the conversion to some extent but there is no overall effect on selectivity of propene. Increase in time-on-stream (TOS remarkably improves propene selectivity at the expense of lower conversion. The performances of bi-metallic zeolite based catalyst largely affected by coke deposition. The presence of butane and ethane adversely affected propane conversion. Optimum propene selectivity is about 48 %, obtained at 600 oC and time-on-stream 10 h.

Catalytic oxidation of light alkanes (C1-C4) by heteropoly compounds

KAUST Repository

Sun, Miao; Zhang, Jizhe; Putaj, Piotr; Caps, Valerie; Lefè bvre, Fré dé ric; Pelletier, Jeremie; Basset, Jean-Marie

2014-01-01

Heteropoly compounds (HPC) have revealed their potential to generate catalyst for selectively converting light alkanes to oxygenated products. There are various structures in which they are active the primary structure being that of the heteropolyanion itself, the secondary structure is the three-dimensional arrangements of polyanions, and the tertiary structure representing the manner in which the secondary structure assembles into solid particles. There are also a huge variety of elements inside the HPA. The heteropoly acids can have acidity, which varies dramatically depending on composition. This complexity of situation makes it very difficult to really have a predictive vision of their ability to activate and functionalize alkanes. However, a large amount of data reported suggests that the initial formula of the precatalyst is pivotal to direct the selectivity of the reaction toward different oxygenates. Inclusion of alternative transition metal atoms as addenda is highly influential with iron, vanadium, and antimony being particularly outstanding.

Catalytic oxidation of light alkanes (C1-C4) by heteropoly compounds

KAUST Repository

Sun, Miao

2014-01-22

Heteropoly compounds (HPC) have revealed their potential to generate catalyst for selectively converting light alkanes to oxygenated products. There are various structures in which they are active the primary structure being that of the heteropolyanion itself, the secondary structure is the three-dimensional arrangements of polyanions, and the tertiary structure representing the manner in which the secondary structure assembles into solid particles. There are also a huge variety of elements inside the HPA. The heteropoly acids can have acidity, which varies dramatically depending on composition. This complexity of situation makes it very difficult to really have a predictive vision of their ability to activate and functionalize alkanes. However, a large amount of data reported suggests that the initial formula of the precatalyst is pivotal to direct the selectivity of the reaction toward different oxygenates. Inclusion of alternative transition metal atoms as addenda is highly influential with iron, vanadium, and antimony being particularly outstanding.

Design, construction and test run of a solid adsorption solar refrigerator using activated carbon/methanol, as adsorbent/adsorbate pair

International Nuclear Information System (INIS)

Anyanwu, E.E.; Ezekwe, C.I.

2003-01-01

The design, construction and test run of a solid adsorption solar refrigerator are presented. It used activated carbon/methanol as the adsorbent/adsorbate pair. The refrigerator has three major components: collector/generator/adsorber, condenser and evaporator. Its flat plate type collector/generator/adsorber used clear plane glass sheet of effective exposed area of 1.2 m 2 . The steel condenser tube with a square plan view was immersed in pool of stagnant water contained in a reinforced sandcrete tank. The evaporator is a spirally coiled copper tube immersed in stagnant water. Adsorbent cooling during the adsorption process is both by natural convection of air over the collector plate and tubes and night sky radiation facilitated by removing the collector box end cover plates. Ambient temperatures during the adsorbate generation and adsorption process varied over 18.5-34 deg. C. The refrigerator yielded evaporator temperatures ranging over 1.0-8.5 deg. C from water initially in the temperature range 24-28 deg. C. Accordingly, the maximum daily useful cooling produced was 266.8 kJ/m 2 of collector area

Study on the adsorption performance of composite adsorbent of CaCl2 and expanded graphite with ammonia as adsorbate

International Nuclear Information System (INIS)

Li, S.L.; Wu, J.Y.; Xia, Z.Z.; Wang, R.Z.

2009-01-01

A novel constant volume test unit was built to study the adsorption performance of a new type composite adsorbent. This test unit can measure the adsorption isosteres of the working pairs. The adsorption isosteres are the curves of the adsorption pressure variation with the adsorption temperatures at constant adsorption quantities. Compared to the former test results of isothermals and isobars, the isosteres are better for the calculation of the adsorption heat, desorption heat and the selection the adsorption working pairs. Three experimental results were obtained: the first result was that the expanded graphite powders were superior to the expandable graphite powders to facilitate the transportation of working fluid in the composite adsorbent. The second one was that the composite adsorbent treated by solution is more homogeneous than the simple mixed composite adsorbent and the treated composite adsorbent has a better mass transfer performance. The last one was that the adsorption isosteres was the same one not only in the heating process but also in the cooling process and this performance was not relevant to the homogeneity of the composite adsorbent

Hydrophilicity and Microsolvation of an Organic Molecule Resolved on the Sub-molecular Level by Scanning Tunneling Microscopy.

Science.gov (United States)

Lucht, Karsten; Loose, Dirk; Ruschmeier, Maximilian; Strotkötter, Valerie; Dyker, Gerald; Morgenstern, Karina

2018-01-26

Low-temperature scanning tunneling microscopy was used to follow the formation of a solvation shell around an adsorbed functionalized azo dye from the attachment of the first water molecule to a fully solvated molecule. Specific functional groups bind initially one water molecule each, which act as anchor points for additional water molecules. Further water attachment occurs in areas close to these functional groups even when the functional groups themselves are already saturated. In contrast, water molecules surround the hydrophobic parts of the molecule only when the two-dimensional solvation shell closes around them. This study thus traces hydrophilic and hydrophobic properties of an organic molecule down to a sub-molecular length scale. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Difference equation model for isothermal gas chromatography expresses retention behavior of homologues of n-alkanes excluding the influence of holdup time

Science.gov (United States)

Wu, Liejun; Chen, Yongli; Caccamise, Sarah A.L.; Li, Qing X.

2012-01-01

A difference equation (DE) model is developed using the methylene retention increment (Δtz) of n-alkanes to avoid the influence of gas holdup time (tM). The effects of the equation orders (1st–5th) on the accuracy of a curve fitting show that a linear equation (LE) is less satisfactory and it is not necessary to use a complicated cubic or higher order equation. The relationship between the logarithm of Δtz and the carbon number (z) of the n-alkanes under isothermal conditions closely follows the quadratic equation for C3–C30 n-alkanes at column temperatures of 24–260 °C. The first and second order forward differences of the expression (Δlog Δtz and Δ2log Δtz, respectively) are linear and constant, respectively, which validates the DE model. This DE model lays a necessary foundation for further developing a retention model to accurately describe the relationship between the adjusted retention time and z of n-alkanes. PMID:22939376

Nano-fabrication of molecular electronic junctions by targeted modification of metal-molecule bonds

Science.gov (United States)

Jafri, S. Hassan M.; Löfås, Henrik; Blom, Tobias; Wallner, Andreas; Grigoriev, Anton; Ahuja, Rajeev; Ottosson, Henrik; Leifer, Klaus

2015-09-01

Reproducibility, stability and the coupling between electrical and molecular properties are central challenges in the field of molecular electronics. The field not only needs devices that fulfill these criteria but they also need to be up-scalable to application size. In this work, few-molecule based electronics devices with reproducible electrical characteristics are demonstrated. Our previously reported 5 nm gold nanoparticles (AuNP) coated with ω-triphenylmethyl (trityl) protected 1,8-octanedithiol molecules are trapped in between sub-20 nm gap spacing gold nanoelectrodes forming AuNP-molecule network. When the trityl groups are removed, reproducible devices and stable Au-thiol junctions are established on both ends of the alkane segment. The resistance of more than 50 devices is reduced by orders of magnitude as well as a reduction of the spread in the resistance histogram is observed. By density functional theory calculations the orders of magnitude decrease in resistance can be explained and supported by TEM observations thus indicating that the resistance changes and strongly improved resistance spread are related to the establishment of reproducible and stable metal-molecule bonds. The same experimental sequence is carried out using 1,6-hexanedithiol functionalized AuNPs. The average resistances as a function of molecular length, demonstrated herein, are comparable to the one found in single molecule devices.

Experimental Determination of the Molar Absorption Coefficient of n-Hexane Adsorbed on High-Silica Zeolites.

Science.gov (United States)

Gatti, Giorgio; Olivas Olivera, Diana F; Sacchetto, Vittoria; Cossi, Maurizio; Braschi, Ilaria; Marchese, Leonardo; Bisio, Chiara

2017-09-06

Determination of the molar absorption coefficients of the CH 3 bending mode at ν˜ =1380 cm -1 (ϵ 1380 ) of n-hexane adsorbed from the gas phase on two different dealuminated zeolites is derived by a combination of IR spectroscopy and microgravimetric analysis. High-silica zeolite Y (HSZ-Y) and zeolite ZSM-5 (with SiO 2 /Al 2 O 3 ratios of 200 and 280, respectively) with different textural and surface features are selected to evaluate the effect of the pore structure and architecture on the value of ϵ 1380 of the adsorbed n-hexane. Experimental data indicate that the molecule experiences a different adsorption environment inside zeolites; thus resulting in a significant change of the dipole moment and very different ϵ 1380 values: (0.278±0.018) cm μmol -1 for HSZ-Y and (0.491±0.032) cm μmol -1 for ZSM-5. Experimental data are also supported by computational modeling, which confirms the effect of different matrices on the IR absorption intensity. This study reveals that the use of probe molecules for quantitative measurements of surface sites has to be judiciously adopted, especially if adsorption occurs in the restricted spaces of microporous materials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aromatization of alkanes over Pt promoted conventional and mesoporous gallosilicates of MEL zeolite

Czech Academy of Sciences Publication Activity Database

Akhtar, M. N.; Al-Yassir, N.; Al-Khattaf, S.; Čejka, Jiří

2012-01-01

Roč. 179, č. 1 (2012), s. 61-72 ISSN 0920-5861 Institutional research plan: CEZ:AV0Z40400503 Keywords : alkane aromatization * ZSM-11 * GaHZSM-11 Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.980, year: 2012

Adsorbent catalytic nanoparticles and methods of using the same

Energy Technology Data Exchange (ETDEWEB)

Slowing, Igor Ivan; Kandel, Kapil

2017-01-31

The present invention provides an adsorbent catalytic nanoparticle including a mesoporous silica nanoparticle having at least one adsorbent functional group bound thereto. The adsorbent catalytic nanoparticle also includes at least one catalytic material. In various embodiments, the present invention provides methods of using and making the adsorbent catalytic nanoparticles. In some examples, the adsorbent catalytic nanoparticles can be used to selectively remove fatty acids from feedstocks for biodiesel, and to hydrotreat the separated fatty acids.

Revisiting the Kinetics and Thermodynamics of the Low-Temperature Oxidation Pathways of Alkanes: A Case Study of the Three Pentane Isomers

KAUST Repository

Bugler, John

2015-07-16

© 2015 American Chemical Society. This paper describes our developing understanding of low-temperature oxidation kinetics. We have investigated the ignition of the three pentane isomers in a rapid compression machine over a wide range of temperatures and pressures, including conditions of negative temperature coefficient behavior. The pentane isomers are small alkanes, yet have structures that are complex enough to allow for the application of their kinetic and thermochemical rules to larger molecules. Updates to the thermochemistry of the species important in the low-temperature oxidation of hydrocarbons have been made based on a thorough literature review. An evaluation of recent quantum-chemically derived rate coefficients from the literature pertinent to important low-temperature oxidation reaction classes has been performed, and new rate rules are recommended for these classes. Several reaction classes have also been included to determine their importance with regard to simulation results, and we have found that they should be included when developing future chemical kinetic mechanisms. A comparison of the model simulations with pressure-time histories from experiments in a rapid compression machine shows very good agreement for both ignition delay time and pressure rise for both the first- and second-stage ignition events. We show that revisions to both the thermochemistry and the kinetics are required in order to replicate experiments well. A broader validation of the models with ignition delay times from shock tubes and a rapid compression machine is presented in an accompanying paper. The results of this study enhance our understanding of the combustion of straight- and branched-chained alkanes.

Desorption of large organic molecules induced by keV projectiles

International Nuclear Information System (INIS)

Delcorte, A.; Garrison, B.J.

2001-01-01

In order to understand the emission of organic molecules in sputtering, classical molecular dynamics (MD) is used to model the 5 keV Ar atom bombardment of polystyrene oligomers adsorbed on Ag{1 1 1}. The analysis of the results shows that a significant fraction of the trajectories generates high action events in the sample. These events are characterized by the simultaneous motion of several hundreds of substrate atoms and, oftentimes, by high emission yields of substrate atoms, clusters and polystyrene molecules. Collision trees representing the energetic part of the cascades confirm that high sputtering yields of molecules occur when a large portion of the primary particle energy is quickly dissipated in the upper layers of the silver substrate. This class of events where high action occurs in the surface region might explain the ejection of organic species with a mass of several kilodaltons such as biomolecules and synthetic polymers. In the simulation, these events are capable of desorbing polystyrene molecules of ∼2 kDa

Identification of isomers in the gas phase and as adsorbates by near-edge X-ray absorption fine structure spectroscopy: Cis- and trans-stilbene

International Nuclear Information System (INIS)

Püttner, Ralph; Schmidt-Weber, Philipp; Kampen, Thorsten; Kolczewski, Christine; Hermann, Klaus; Horn, Karsten

2017-01-01

Highlights: • NEXAFS spectra of the cis- and trans-isomer of stilbene reveal distinct differences by which the isomers can be distinguished. • DFT calculations using the transition potential approach assign specific transitions that are different in the two isomers. • On Si(100), these differences in NEXAFS are also observed, suggesting that their conformations survive in the bonding situation. • NEXAFS is thus shown to be a sensitive tool to distinguish isomers in adsorbed species. - Abstract: Near-edge x-ray absorption fine structure spectra of the cis- and trans-isomers of stilbene in the gas phase reveal clear differences, which are analyzed by results from density-functional theory calculations using the transition potential approach. The differences between the two species also occur in stilbene adsorbed on Si(100), opening the way towards studying structural changes in molecules in different surface environments, and configurational switching in organic molecules on surfaces in particular.

Identification of isomers in the gas phase and as adsorbates by near-edge X-ray absorption fine structure spectroscopy: Cis- and trans-stilbene

Energy Technology Data Exchange (ETDEWEB)

Püttner, Ralph [Department of Physics, Freie Universität Berlin, 14195 Berlin (Germany); Schmidt-Weber, Philipp [Fritz Haber Institute of the Max Planck Society, 14195 Berlin (Germany); Kampen, Thorsten [SPECS Surface Nano Analysis GmbH, 13355 Berlin (Germany); Kolczewski, Christine [Deutsches Museum München, 80538 Munich (Germany); Hermann, Klaus [Fritz Haber Institute of the Max Planck Society, 14195 Berlin (Germany); Horn, Karsten, E-mail: horn@fhi-berlin.mpg.de [Fritz Haber Institute of the Max Planck Society, 14195 Berlin (Germany)

2017-02-15

Highlights: • NEXAFS spectra of the cis- and trans-isomer of stilbene reveal distinct differences by which the isomers can be distinguished. • DFT calculations using the transition potential approach assign specific transitions that are different in the two isomers. • On Si(100), these differences in NEXAFS are also observed, suggesting that their conformations survive in the bonding situation. • NEXAFS is thus shown to be a sensitive tool to distinguish isomers in adsorbed species. - Abstract: Near-edge x-ray absorption fine structure spectra of the cis- and trans-isomers of stilbene in the gas phase reveal clear differences, which are analyzed by results from density-functional theory calculations using the transition potential approach. The differences between the two species also occur in stilbene adsorbed on Si(100), opening the way towards studying structural changes in molecules in different surface environments, and configurational switching in organic molecules on surfaces in particular.

Predominance of even carbon-numbered n-alkanes from lacustrine sediments in Linxia Basin, NE Tibetan Plateau: Implications for climate change

International Nuclear Information System (INIS)

Wang Yongli; Fang Xiaomin; Zhang Tongwei; Li Yuanmao; Wu Yingqin; He Daxiang; Wang Youxiao

2010-01-01

Research highlights: → This study reports the first observation of predominant even carbon-numbered n-alkanes of sediments in the continuous lacustrine-sedimentary section (Maogou) from the Late Miocene to the Early Pliocene (13-4.4 Ma) in the Linxia Basin, NE Tibetan Plateau. → Certain types of special autochthonous bacteria are a possible source for the special distribution of even carbon-numbered n-alkanes in lacustrine sediments. → These bacteria may have a high production rate in weak oxic-anoxic and arid depositional environments, in which a variety of geochemical parameters have recorded palaeoclimate change. → A close correspondence among the low ratio of n-C 27 /n-C 31 , the heavy δ 13 C values of TOC and a strong even carbon-number predominance (low OEP 16-20 values) from approximately 6.5 to 4.4 Ma and at approximately 8 Ma in the studied section suggests that n-alkanes with a high predominance of even carbon-numbers may be treated as geochemical proxies for arid climate. - Abstract: This study reports the first observation of predominant even C-numbered n-alkanes from sediments in the continuous lacustrine-sedimentary section (Maogou) from the Late Miocene to the Early Pliocene (13-4.4 Ma) in the Linxia Basin, NE Tibetan Plateau. The n-alkanes showed a bimodal distribution that is characterised by a centre at n-C 16 -n-C 20 with maximum values at n-C 18 and n-C 27 -n-C 31 as well as at n-C 29 . The first mode shows a strong even C-number predominance (OEP 16-20 0.34-0.66). In contrast, the second mode has a strong odd C-number predominance (OEP 27-31 1.20-2.45). Certain types of special autochthonous bacteria are a possible source for this distribution of even C-numbered n-alkanes in lacustrine sediments. These bacteria may have a high production rate in weak oxic-anoxic and arid depositional environments, in which a variety of geochemical parameters have recorded palaeoclimate change.

Anaerobic Coculture of Microalgae with Thermosipho globiformans and Methanocaldococcus jannaschii at 68°C Enhances Generation of n-Alkane-Rich Biofuels after Pyrolysis

Science.gov (United States)

Matsuyama, Shigeru; Igarashi, Kensuke; Utsumi, Motoo; Shiraiwa, Yoshihiro; Kuwabara, Tomohiko

2013-01-01

We tested different alga-bacterium-archaeon consortia to investigate the production of oil-like mixtures, expecting that n-alkane-rich biofuels might be synthesized after pyrolysis. Thermosipho globiformans and Methanocaldococcus jannaschii were cocultured at 68°C with microalgae for 9 days under two anaerobic conditions, followed by pyrolysis at 300°C for 4 days. Arthrospira platensis (Cyanobacteria), Dunaliella tertiolecta (Chlorophyta), Emiliania huxleyi (Haptophyta), and Euglena gracilis (Euglenophyta) served as microalgal raw materials. D. tertiolecta, E. huxleyi, and E. gracilis cocultured with the bacterium and archaeon inhibited their growth and CH4 production. E. huxleyi had the strongest inhibitory effect. Biofuel generation was enhanced by reducing impurities containing alkanenitriles during pyrolysis. The composition and amounts of n-alkanes produced by pyrolysis were closely related to the lipid contents and composition of the microalgae. Pyrolysis of A. platensis and D. tertiolecta containing mainly phospholipids and glycolipids generated short-carbon-chain n-alkanes (n-tridecane to n-nonadecane) and considerable amounts of isoprenoids. E. gracilis also produced mainly short n-alkanes. In contrast, E. huxleyi containing long-chain (31 and 33 carbon atoms) alkenes and very long-chain (37 to 39 carbon atoms) alkenones, in addition to phospholipids and glycolipids, generated a high yield of n-alkanes of various lengths (n-tridecane to n-pentatriacontane). The gas chromatography-mass spectrometry (GC-MS) profiles of these n-alkanes were similar to those of native petroleum crude oils despite containing a considerable amount of n-hentriacontane. The ratio of phytane to n-octadecane was also similar to that of native crude oils. PMID:23183975

Measurement and modelling of hydrogen bonding in 1-alkanol plus n-alkane binary mixtures

DEFF Research Database (Denmark)

von Solms, Nicolas; Jensen, Lars; Kofod, Jonas L.

2007-01-01

Two equations of state (simplified PC-SAFT and CPA) are used to predict the monomer fraction of 1-alkanols in binary mixtures with n-alkanes. It is found that the choice of parameters and association schemes significantly affects the ability of a model to predict hydrogen bonding in mixtures, eve...... studies, which is clarified in the present work. New hydrogen bonding data based on infrared spectroscopy are reported for seven binary mixtures of alcohols and alkanes. (C) 2007 Elsevier B.V. All rights reserved....... though pure-component liquid densities and vapour pressures are predicted equally accurately for the associating compound. As was the case in the study of pure components, there exists some confusion in the literature about the correct interpretation and comparison of experimental data and theoretical...

Development of adsorbents for recovery of uranium from seawater

International Nuclear Information System (INIS)

Egawa, Hiroaki; Furusaki, Shintaro.

1987-01-01

The largest subject for putting the extraction of uranium from seawater in practical use is the development of high performance adsorbents for uranium. In this paper, the way of thinking about the development of adsorbents for extracting uranium from seawater and the recent reports on this subject are described. Next, the research on the adsorbing capacity and adsorbing rate of the adsorbents developed so far is summarized, and the way of thinking about the evaluation of adsorbent performance which is the base of the design of a system for extracting uranium from seawater is explained, taking amidoxime type adsorbent as the example. For Japan where energy resources are scant, the uranium contained in seawater, which is estimated to be about 4.2 billion t, is the most luring important element. Uranium is contained in seawater is very low concentration of 3 ppb, and exists as anion complex salt. In 1960s, the Harwell Atomic Energy Research Establishment in UK found out that titanium oxide hydrate is the most promising as the adsorbent. Also a number of organic absorbents have been developed. In order to bring adsorbents in contact with seawater, pumping, ocean current and wave force are utilized. Adsorbents are in spherical, fiber and film forms, and held as fixed beds and fluidized beds. (Kako, I.) 48 refs

Developing Selective Oxidation Catalysts of Light Alkanes:. from Fundamental Understanding to Rational Design

Science.gov (United States)

Fu, Gang; Yi, Xiaodong; Huang, Chuanjing; Xu, Xin; Weng, Weizheng; Xia, Wensheng; Wan, Hui-Lin

Selective oxidation of light alkanes remains to be a great challenge for the wider use of alkanes as feedstocks. To achieve high activity and at the same time high selectivity, some key issues have to be addressed: (1) the stability of the desired products with respect to the reactants; (2) the roles of the active components in the catalysts, the structure and the functionality of the active centers; (3) the reducibility of the metal cations, the Lewis acid sites and their synergic effects with the basic sites of the lattice oxygen anions; (4) spatial isolation of the active centers; and (5) the mechanisms for the formation and transformation of the intermediates and their kinetic controls. In this contribution, we took selective oxidation of propane to acrolein as our target reaction, and reviewed mainly our own work, trying to provide some thinking and answers to these five questions.

Investigation of A-3 adsorbent-ditolylmethane two-phase system

International Nuclear Information System (INIS)

Ermakov, V.A.; Benderskaya, O.S.

1988-01-01

Compatibility of A-3 adsorbent, produced on the basis of palygoskite clay, with organic coolant of nuclear reactors-ditolylmethane (DTM)- and the possibility to use the given adsorbent for DTM purification from surfactant impurities are investigated. Compatibility of the adsorbent with DTM was evaluated by the concentration of its constituents in liquid phase. Sufactant adsorption was observed by the change in acid number of coolant, optical density at λ=396 nm and adsorbate mass in the adsorbent. From spent adsorbent the coolant was washed out by n-heptane, and the adsorbate - by methylene chloride, othanol and water in succession. On the basis of the results obtained the conclusion is made that A3 possesses a high chemical stability in DTM medium, i.e. it is compatible with DTM and can be used for its purification from surfactant impurities sorbed on heat-transferring surface

Heterogeneous Reactions of Limonene on Mineral Dust: Impacts of Adsorbed Water and Nitric Acid.

Science.gov (United States)

Lederer, Madeline R; Staniec, Allison R; Coates Fuentes, Zoe L; Van Ry, Daryl A; Hinrichs, Ryan Z

2016-12-08

Biogenic volatile organic compounds (BVOCs), including the monoterpene limonene, are a major source of secondary organic aerosol (SOA). While gas-phase oxidation initiates the dominant pathway for BVOC conversion to SOA, recent studies have demonstrated that biogenic hydrocarbons can also directly react with acidic droplets. To investigate whether mineral dust may facilitate similar reactive uptake of biogenic hydrocarbons, we studied the heterogeneous reaction of limonene with mineral substrates using condensed-phase infrared spectroscopy and identified the formation of irreversibly adsorbed organic products. For kaolinite, Arizona Test Dust, and silica at 30% relative humidity, GC-MS identified limonene-1,2-diol as the dominant product with total organic surface concentrations on the order of (3-5) × 10 18 molecules m -2 . Experiments with 18 O-labeled water support a mechanism initiated by oxidation of limonene by surface redox sites forming limonene oxide followed by water addition to the epoxide to form limonenediol. Limonene uptake on α-alumina, γ-alumina, and montmorillonite formed additional products in high yield, including carveol, carvone, limonene oxide, and α-terpineol. To model tropospheric processing of mineral aerosol, we also exposed each mineral substrate to gaseous nitric acid prior to limonene uptake and identified similar surface adsorbed products that were formed at rates 2 to 5 times faster than without nitrate coatings. The initial rate of reaction was linearly dependent on gaseous limonene concentration between 5 × 10 12 and 5 × 10 14 molecules cm -3 (0.22-20.5 ppm) consistent with an Eley-Rideal-type mechanism in which gaseous limonene reacts directly with reactive surface sites. Increasing relative humidity decreased the amount of surface adsorbed products indicating competitive adsorption of surface adsorbed water. Using a laminar flow tube reactor we measured the uptake coefficient for limonene on kaolinite at 25% RH to range from

Charge Transport in Metal-Molecule-Metal Junctions Probed by Conducting Atomic Force Microscopy

International Nuclear Information System (INIS)

Lee, Min Hyung; Song, Hyunwook

2013-01-01

We have demonstrated a proof of intrinsic charge transport properties in alkanedithiol molecular junctions using a multiprobe approach combining a variety of transport techniques. The temperature-independent I(V) behavior and the correct exponential decay of conductance with respect to molecular length shows that the dominant charge transport mechanism is off-resonant tunneling. Length-dependent TVS measurements for the saturated alkane-dithiol series indicate that we did indeed probe a molecular system with CAFM. These results can provide stringent criteria to establish a valid molecular transport junction via a probabilistic measurement technique. In this study, we report a study of charge transport in alkanedithiol SAMs formed in metal-molecule-metal junctions using CAFM in combination with a variety of molecular transport techniques including temperature-and length-variable transport measurements and transition voltage spectroscopy. The main goal of this study is to probe the intrinsic transport properties of component molecules using CAFM, but not parasitic or defect-related effects