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Sample records for adsorption reaction probing

  1. Probing adsorption sites for CO on ceria.

    PubMed

    Mudiyanselage, Kumudu; Kim, Hyun You; Senanayake, Sanjaya D; Baber, Ashleigh E; Liu, Ping; Stacchiola, Dario

    2013-10-14

    Ceria based catalysts show remarkable activity for CO conversion reactions such as CO oxidation and the water-gas shift reaction. The identification of adsorption sites on the catalyst surfaces is essential to understand the reaction mechanisms of these reactions, but the complexity of heterogeneous powder catalysts and the propensity of ceria to easily change oxidation states in the presence of small concentrations of either oxidizing or reducing agents make the process difficult. In this study, the adsorption of CO on CuOx/Cu(111) and CeOx/Cu(111) systems has been studied using infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. IR peaks for the adsorbed CO on O/Cu(111) with only chemisorbed oxygen, well-ordered Cu2O/Cu(111) and disordered copper oxide [CuOx/Cu(111)] were observed at 2070-2072, 2097-2098 and 2101-2111 cm(-1), respectively. On CeOx/Cu(111) systems CO chemisorbs at 90 K only on Cu sites under ultra-high vacuum (UHV) conditions, whereas at elevated CO pressures and low temperatures adsorption of CO on Ce(3+) is observed, with a corresponding IR peak at 2162 cm(-1). These experimental results are further supported by DFT calculations, and help to unequivocally distinguish the presence of Ce(3+) cations on catalyst samples by using CO as a probe molecule. PMID:23942870

  2. Adsorption Isotherms and Surface Reaction Kinetics

    ERIC Educational Resources Information Center

    Lobo, L. S.; Bernardo, C. A.

    1974-01-01

    Explains an error that occurs in calculating the conditions for a maximum value of a rate expression for a bimolecular reaction. The rate expression is derived using the Langmuir adsorption isotherm to relate gas pressures and corresponding surface coverages. (GS)

  3. Probing the pore wall structure of nanoporous carbons using adsorption.

    PubMed

    Nguyen, Thanh X; Bhatia, Suresh K

    2004-04-27

    Hitherto, adsorption has been traditionally used to study only the porous structure in disordered materials, while the structure of the solid phase skeleton has been probed by crystallographic methods such as X-ray diffraction. Here we show that for carbons density functional theory, suitably adapted to consider heterogeneity of the pore walls, can be reliably used to probe features of the solid structure hitherto accessibly only approximately even by crystallographic methods. We investigate a range of carbons and determine pore wall thickness distributions using argon adsorption, with results corroborated by X-ray diffraction.

  4. CONTAMINANT ADSORPTION AND OXIDATION VIA FENTON REACTION

    EPA Science Inventory

    A ground water treatment process is proposed involving two cgemical processes: adsorption and oxidation. Adsorption of an organic compound onto granulated activated carbon (GAC) containing iron conveniently results in immobilizing and concentrating contaminants from the ground w...

  5. Study of char gasification in a reaction/adsorption apparatus

    SciTech Connect

    Sotirchos, S.V.; Crowley, J.A.

    1987-09-01

    The reaction of an activated carbon (coconut char) with CO/sub 2/ was studied in a reaction/adsorption apparatus which allows successive reactivity and physical adsorption measurements to be made on the same solid sample. Reaction and surface area evolution data were obtained in the temperature range from 800 to 900/sup 0/C. All reaction rate trajectories obtained in this study showed a maximum in the reaction rate, 2-3 times higher than the initial rate, at about 85% conversion. There was no correlation between these results and the evolution of the internal surface area although the reaction appeared to take place initially in the kinetically controlled regime.

  6. Adsorption and catalysis: The effect of confinement on chemical reactions

    NASA Astrophysics Data System (ADS)

    Santiso, Erik E.; George, Aaron M.; Turner, C. Heath; Kostov, Milen K.; Gubbins, Keith E.; Buongiorno-Nardelli, Marco; Sliwinska-Bartkowiak, Małgorzata

    2005-10-01

    Confinement within porous materials can affect chemical reactions through a host of different effects, including changes in the thermodynamic state of the system due to interactions with the pore walls, selective adsorption, geometrical constraints that affect the reaction mechanism, electronic perturbation due to the substrate, etc. In this work, we present an overview of some of our recent research on some of these effects, on chemical equilibrium, kinetic rates and reaction mechanisms. We also discuss our current and future directions for research in this area.

  7. Surface sampling concentration and reaction probe

    SciTech Connect

    Van Berkel, Gary J; Elnaggar, Mariam S

    2013-07-16

    A method of analyzing a chemical composition of a specimen is described. The method can include providing a probe comprising an outer capillary tube and an inner capillary tube disposed co-axially within the outer capillary tube, where the inner and outer capillary tubes define a solvent capillary and a sampling capillary in fluid communication with one another at a distal end of the probe; contacting a target site on a surface of a specimen with a solvent in fluid communication with the probe; maintaining a plug volume proximate a solvent-specimen interface, wherein the plug volume is in fluid communication with the probe; draining plug sampling fluid from the plug volume through the sampling capillary; and analyzing a chemical composition of the plug sampling fluid with an analytical instrument. A system for performing the method is also described.

  8. Adsorption of 2-propanol on ice probed by ambient pressure X-ray photoelectron spectroscopy

    DOE PAGES

    Newberg, John T.; Bluhm, Hendrik

    2015-08-18

    The interaction of 2-propanol with ice was examined via ambient pressure X-ray photoelectron spectroscopy (APXPS), a surface sensitive technique that probes the adsorbed 2-propanol directly with submonolayer resolution. Isothermal uptake experiments were performed on vapor deposited ice at 227 K in the presence of the equilibrium water vapor pressure of 0.05 Torr and 2-propanol partial pressures ranging from 5 × 10-5 to 2 × 10-3 Torr. The C 1s APXPS spectra of adsorbed 2-propanol showed two characteristic peaks associated with the COH alcohol group and CMe methyl groups in a 1 : 2 ratio, respectively. Coverage increased with 2-propanol partialmore » pressure and followed first order Langmuir kinetics with a Langmuir constant of K = 6.3 × 103 Torr-1. The 1 : 2 ratio of COH : CMe remained constant with increasing coverage, indicating there is no chemical reaction upon adsorption. The observed Langmuir kinetics using APXPS is consistent with previous observations of other small chain alcohols via indirect adsorption methods using, e.g., Knudsen cell and coated wall flow tube reactors.« less

  9. Adsorption of 2-propanol on ice probed by ambient pressure X-ray photoelectron spectroscopy

    SciTech Connect

    Newberg, John T.; Bluhm, Hendrik

    2015-08-18

    The interaction of 2-propanol with ice was examined via ambient pressure X-ray photoelectron spectroscopy (APXPS), a surface sensitive technique that probes the adsorbed 2-propanol directly with submonolayer resolution. Isothermal uptake experiments were performed on vapor deposited ice at 227 K in the presence of the equilibrium water vapor pressure of 0.05 Torr and 2-propanol partial pressures ranging from 5 × 10-5 to 2 × 10-3 Torr. The C 1s APXPS spectra of adsorbed 2-propanol showed two characteristic peaks associated with the COH alcohol group and CMe methyl groups in a 1 : 2 ratio, respectively. Coverage increased with 2-propanol partial pressure and followed first order Langmuir kinetics with a Langmuir constant of K = 6.3 × 103 Torr-1. The 1 : 2 ratio of COH : CMe remained constant with increasing coverage, indicating there is no chemical reaction upon adsorption. The observed Langmuir kinetics using APXPS is consistent with previous observations of other small chain alcohols via indirect adsorption methods using, e.g., Knudsen cell and coated wall flow tube reactors.

  10. Adsorption of 2-propanol on ice probed by ambient pressure X-ray photoelectron spectroscopy.

    PubMed

    Newberg, John T; Bluhm, Hendrik

    2015-09-28

    The interaction of 2-propanol with ice was examined via ambient pressure X-ray photoelectron spectroscopy (APXPS), a surface sensitive technique that probes the adsorbed 2-propanol directly with submonolayer resolution. Isothermal uptake experiments were performed on vapor deposited ice at 227 K in the presence of the equilibrium water vapor pressure of 0.05 Torr and 2-propanol partial pressures ranging from 5 × 10(-5) to 2 × 10(-3) Torr. The C 1s APXPS spectra of adsorbed 2-propanol showed two characteristic peaks associated with the COH alcohol group and CMe methyl groups in a 1 : 2 ratio, respectively. Coverage increased with 2-propanol partial pressure and followed first order Langmuir kinetics with a Langmuir constant of K = 6.3 × 10(3) Torr(-1). The 1 : 2 ratio of COH : CMe remained constant with increasing coverage, indicating there is no chemical reaction upon adsorption. The observed Langmuir kinetics using APXPS is consistent with previous observations of other small chain alcohols via indirect adsorption methods using, e.g., Knudsen cell and coated wall flow tube reactors. PMID:26299301

  11. Study of enzyme adsorption and reaction kinetics for cellulose hydrolysis

    SciTech Connect

    Gilbert, I.G.

    1982-01-01

    Enzymatic hydrolysis of cellulose occurs due to the combined catalytic action of two types of cellulase components commonly referred to as C/sub 1/ and C/sub x/. However, before the hydrolysis reaction can begin, it is necessary for these enzymes to first adsorb onto the accessible surfaces of the insoluble cellulose substrate. The objective of the study was to gain a better understanding of the relationships between the adsorption of these enzyme components, the hydrolysis kinetics, the cellulosic surface area accessible to the enzymes, and the cellulose crystallinity. These relationships were investigated by passing a Trichoderma viride cellulase solution through columns of cellulose powder having different accessibility and crystallinity, and then analyzing the quantities of the different enzyme components and the hydrolysis product in the effluent. The amounts of the different cellulase components were analyzed using high-performance anion-exchange chromatography. Additional adsorption and hydrolysis experiments were done using columns of cellulose beads specially developed to provide amodel substrate for this analysis. A mathematical model has been formulated to describe the kinetics of enzyme adsorption and the resultant, initial hydrolysis rate in cellulose column. The analytical solutions obtained have been linearized into a convenient form so that the kinetic parameters of the model can be readily determined from experimental breakthrough curves.

  12. Adsorption of probe molecules in pillared interlayered clays: Experiment and computer simulation

    SciTech Connect

    Gallardo, A. Guil, J. M.; Lomba, E.; Almarza, N. G.; Khatib, S. J.; Cabrillo, C.; Sanz, A.; Pires, J.

    2014-06-14

    In this paper we investigate the adsorption of various probe molecules in order to characterize the porous structure of a series of pillared interlayered clays (PILC). To that aim, volumetric and microcalorimetric adsorption experiments were performed on various Zr PILC samples using nitrogen, toluene, and mesitylene as probe molecules. For one of the samples, neutron scattering experiments were also performed using toluene as adsorbate. Various structural models are proposed and tested by means of a comprehensive computer simulation study, using both geometric and percolation analysis in combination with Grand Canonical Monte Carlo simulations in order to model the volumetric and microcalorimetric isotherms. On the basis of this analysis, we propose a series of structural models that aim at accounting for the adsorption experimental behavior, and make possible a microscopic interpretation of the role played by the different interactions and steric effects in the adsorption processes in these rather complex disordered microporous systems.

  13. Mechanisms, kinetics, and dynamics of oxidation and reactions on oxide surfaces investigated by scanning probe microscopy.

    PubMed

    Altman, Eric I; Schwarz, Udo D

    2010-07-20

    Advances in scanning probe microscopies (SPM) have allowed the mechanisms and rates of adsorption, diffusion and reactions on surfaces to be characterized by directly observing the motions of the individual atoms and molecules involved. The importance of oxides as thermal and photocatalysts, chemical sensors, and substrates for epitaxial growth has motivated dynamical SPM studies of oxide surfaces and their formation. Work on the TiO(2) (110) surface is reviewed as an example of how dynamic SPM studies have revealed unexpected interactions between adsorbates and defects that influence macroscopic reaction rates. Studies following diffusion, adsorption and phase transitions on bulk and surface oxides are also discussed. A perspective is provided on advanced SPM techniques that hold great promise for yielding new insights into the mechanisms and rates of elemental processes that take place either during oxidation or on oxide surfaces, with particular emphasis on methods that extend the time and chemical resolution of dynamical SPM measurements.

  14. Two-color emissive probes for click reactions.

    PubMed

    Wirtz, Marcel; Grüter, Andreas; Rebmann, Philipp; Dier, Tobias; Volmer, Dietrich A; Huch, Volker; Jung, Gregor

    2014-10-28

    Cu(I)-catalyzed azide-alkyne cyclization (CuAAC) is the paradigmatic click reaction of continuous interest. Especially fluorogenic and FRET probes have become indispensable tools for life sciences. Here, we present a fluorescent alkyne for monitoring CuAAC, which undergoes a bathochromic shift upon reaction. Application in single-molecule and catalysis research is foreseen. PMID:25200167

  15. Immobilization of ɛ-polylysine onto the probe surface for molecular adsorption type endotoxin detection system

    NASA Astrophysics Data System (ADS)

    Ooe, Katsutoshi; Tsuji, Akihito; Nishishita, Naoki; Hirano, Yoshiaki

    2007-04-01

    adsorption reaction between ɛ-polylysine and endotoxin. ɛ-polylysine has the structure of straight chain molecule composed by 25-30 residues made by lysine, and it is used as an antimicrobial agent, moreover, cellulose beads with immobilized ɛ-polylysine is used as the barrier filter for endotoxin removal. Therefore, it is expected that the endotoxin be adsorbed to the immobilized ɛ-polylysine onto the probe. As the result of this reaction, the mass of the probe is increased, and endotoxin can be detected by using of Quartz Crystal Microbalance (QCM). In our previous research, we have already acquired the proteins immobilization technique onto Au and Si surface. In this report, the proposal of molecular adsorption type endotoxin detection system, and the immobilization of ɛ-polylysine onto the probe are described. We use X-ray Photoelectron Spectroscopy (XPS) to confirm the ɛ-polylysine immobilization, and the adsorptive activity of immobilized ɛ-polylysine is measured by XPS and AFM. The purpose of this study is to bring about the realization of "Real-time endotoxin detection system".

  16. Molecular Adsorption on Nano Colloidal Particles Probed by Second Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Jen, Shih-Hui; Dai, Hai-Lung

    2006-03-01

    It is shown that second-harmonic generation (SHG), detected at 90 degree angle from the fundamental beam propagation direction, can be used to probe molecular adsorption on spherical nano colloidal particles with diameter as small as 50 nm. Measurements done with the malachite green dye adsorbed on polystyrene particles with diameters ranging from 50 to 250 nm show that the SHG signal from these surface adsorbed molecules tilts toward larger scattering angles when the particle size becomes smaller. This phenomenon can be rigorously described by the nonlinear Rayleigh-Gans-Debye theory and used for measuring the density and adsorption free energy of molecules adsorbed on nanometer size colloidal particles.

  17. Modeling adsorption and reactions of organic molecules at metal surfaces.

    PubMed

    Liu, Wei; Tkatchenko, Alexandre; Scheffler, Matthias

    2014-11-18

    CONSPECTUS: The understanding of adsorption and reactions of (large) organic molecules at metal surfaces plays an increasingly important role in modern surface science and technology. Such hybrid inorganic/organic systems (HIOS) are relevant for many applications in catalysis, light-emitting diodes, single-molecule junctions, molecular sensors and switches, and photovoltaics. Obviously, the predictive modeling and understanding of the structure and stability of such hybrid systems is an essential prerequisite for tuning their electronic properties and functions. At present, density-functional theory (DFT) is the most promising approach to study the structure, stability, and electronic properties of complex systems, because it can be applied to both molecules and solids comprising thousands of atoms. However, state-of-the-art approximations to DFT do not provide a consistent and reliable description for HIOS, which is largely due to two issues: (i) the self-interaction of the electrons with themselves arising from the Hartree term of the total energy that is not fully compensated in approximate exchange-correlation functionals, and (ii) the lack of long-range part of the ubiquitous van der Waals (vdW) interactions. The self-interaction errors sometimes lead to incorrect description of charge transfer and electronic level alignment in HIOS, although for molecules adsorbed on metals these effects will often cancel out in total energy differences. Regarding vdW interactions, several promising vdW-inclusive DFT-based methods have been recently demonstrated to yield remarkable accuracy for intermolecular interactions in the gas phase. However, the majority of these approaches neglect the nonlocal collective electron response in the vdW energy tail, an effect that is particularly strong in condensed phases and at interfaces between different materials. Here we show that the recently developed DFT+vdW(surf) method that accurately accounts for the collective electronic

  18. Modeling adsorption and reactions of organic molecules at metal surfaces.

    PubMed

    Liu, Wei; Tkatchenko, Alexandre; Scheffler, Matthias

    2014-11-18

    CONSPECTUS: The understanding of adsorption and reactions of (large) organic molecules at metal surfaces plays an increasingly important role in modern surface science and technology. Such hybrid inorganic/organic systems (HIOS) are relevant for many applications in catalysis, light-emitting diodes, single-molecule junctions, molecular sensors and switches, and photovoltaics. Obviously, the predictive modeling and understanding of the structure and stability of such hybrid systems is an essential prerequisite for tuning their electronic properties and functions. At present, density-functional theory (DFT) is the most promising approach to study the structure, stability, and electronic properties of complex systems, because it can be applied to both molecules and solids comprising thousands of atoms. However, state-of-the-art approximations to DFT do not provide a consistent and reliable description for HIOS, which is largely due to two issues: (i) the self-interaction of the electrons with themselves arising from the Hartree term of the total energy that is not fully compensated in approximate exchange-correlation functionals, and (ii) the lack of long-range part of the ubiquitous van der Waals (vdW) interactions. The self-interaction errors sometimes lead to incorrect description of charge transfer and electronic level alignment in HIOS, although for molecules adsorbed on metals these effects will often cancel out in total energy differences. Regarding vdW interactions, several promising vdW-inclusive DFT-based methods have been recently demonstrated to yield remarkable accuracy for intermolecular interactions in the gas phase. However, the majority of these approaches neglect the nonlocal collective electron response in the vdW energy tail, an effect that is particularly strong in condensed phases and at interfaces between different materials. Here we show that the recently developed DFT+vdW(surf) method that accurately accounts for the collective electronic

  19. Modeling Adsorption and Reactions of Organic Molecules at Metal Surfaces

    PubMed Central

    2014-01-01

    Conspectus The understanding of adsorption and reactions of (large) organic molecules at metal surfaces plays an increasingly important role in modern surface science and technology. Such hybrid inorganic/organic systems (HIOS) are relevant for many applications in catalysis, light-emitting diodes, single-molecule junctions, molecular sensors and switches, and photovoltaics. Obviously, the predictive modeling and understanding of the structure and stability of such hybrid systems is an essential prerequisite for tuning their electronic properties and functions. At present, density-functional theory (DFT) is the most promising approach to study the structure, stability, and electronic properties of complex systems, because it can be applied to both molecules and solids comprising thousands of atoms. However, state-of-the-art approximations to DFT do not provide a consistent and reliable description for HIOS, which is largely due to two issues: (i) the self-interaction of the electrons with themselves arising from the Hartree term of the total energy that is not fully compensated in approximate exchange-correlation functionals, and (ii) the lack of long-range part of the ubiquitous van der Waals (vdW) interactions. The self-interaction errors sometimes lead to incorrect description of charge transfer and electronic level alignment in HIOS, although for molecules adsorbed on metals these effects will often cancel out in total energy differences. Regarding vdW interactions, several promising vdW-inclusive DFT-based methods have been recently demonstrated to yield remarkable accuracy for intermolecular interactions in the gas phase. However, the majority of these approaches neglect the nonlocal collective electron response in the vdW energy tail, an effect that is particularly strong in condensed phases and at interfaces between different materials. Here we show that the recently developed DFT+vdWsurf method that accurately accounts for the collective electronic

  20. Particle-scale CO2 adsorption kinetics modeling considering three reaction mechanisms

    SciTech Connect

    Suh, Dong-Myung; Sun, Xin

    2013-09-01

    In the presence of water (H2O), dry and wet adsorptions of carbon dioxide (CO2) and physical adsorption of H2O happen concurrently in a sorbent particle. The three reactions depend on each other and have a complicated, but important, effect on CO2 capturing via a solid sorbent. In this study, transport phenomena in the sorbent were modeled, including the tree reactions, and a numerical solving procedure for the model also was explained. The reaction variable distribution in the sorbent and their average values were calculated, and simulation results were compared with experimental data to validate the proposed model. Some differences, caused by thermodynamic parameters, were observed between them. However, the developed model reasonably simulated the adsorption behaviors of a sorbent. The weight gained by each adsorbed species, CO2 and H2O, is difficult to determine experimentally. It is known that more CO2 can be captured in the presence of water. Still, it is not yet known quantitatively how much more CO2 the sorbent can capture, nor is it known how much dry and wet adsorptions separately account for CO2 capture. This study addresses those questions by modeling CO2 adsorption in a particle and simulating the adsorption process using the model. As adsorption temperature changed into several values, the adsorbed amount of each species was calculated. The captured CO2 in the sorbent particle was compared quantitatively between dry and wet conditions. As the adsorption temperature decreased, wet adsorption increased. However, dry adsorption was reduced.

  1. Coherent population trapping probed by charge exchange reactions

    NASA Astrophysics Data System (ADS)

    Gieler, M.; Aumayr, F.; Windholz, L.

    1992-12-01

    Coherent trapping of atomic population in sodium induced by two-frequency laser light has been studied by using a charge exchange reaction for probing the upper level population. When the two-photon resonance condition occurs, the signal due to electron capture from excited Na*(3p) atoms by He2+ projectile ions exhibits the characteristic ``black resonance'' dip, indicating (by nonoptical means) that the fraction of Na atoms in the excited state actually drops to zero.

  2. Mechanism of cis-prenyltransferase reaction probed by substrate analogues

    SciTech Connect

    Lu, Yen-Pin; Liu, Hon-Ge; Teng, Kuo-Hsun; Liang, Po-Huang

    2010-10-01

    Research highlights: {yields} The extremely slow trans-OPPS reaction using 2-Fluoro-FPP supports the sequential mechanism with the carbocation intermediate. {yields} The similar UPPS reaction rate under single turnover supports the concerted mechanism, without the carbocation intermediate. {yields} The secondary kinetic isotope effect also supports associate transition state for UPPS reaction, without the carbocation intermediate. -- Abstract: Undecaprenyl pyrophosphate synthase (UPPS) is a cis-type prenyltransferases which catalyzes condensation reactions of farnesyl diphosphate (FPP) with eight isopentenyl pyrophosphate (IPP) units to generate C{sub 55} product. In this study, we used two analogues of FPP, 2-fluoro-FPP and [1,1-{sup 2}H{sub 2}]FPP, to probe the reaction mechanism of Escherichia coli UPPS. The reaction rate of 2-fluoro-FPP with IPP under single-turnover condition is similar to that of FPP, consistent with the mechanism without forming a farnesyl carbocation intermediate. Moreover, the deuterium secondary KIE of 0.985 {+-} 0.022 measured for UPPS reaction using [1,1-{sup 2}H{sub 2}]FPP supports the associative transition state. Unlike the sequential mechanism used by trans-prenyltransferases, our data demonstrate E. coli UPPS utilizes the concerted mechanism.

  3. Probing Adsorption / Desorption Processes at the Liquid / Solid Interface: Thiols and Proteins

    NASA Astrophysics Data System (ADS)

    Campbell, Charles; Jung, Linda S.; Shumaker-Parry, Jennifer; Nelsen, K. E.; Stayton, P. S.; Gelb, M. H.; Aebersold, R.

    2001-03-01

    The adsorption of molecules from liquid solutions onto solid surfaces can be monitored with high sensitivity and fast time response by following changes in the angle or wavelength at which the surface plasmon resonance (SPR) of a thin metal film is optically excited. Simple methods convert these measured changes into adsorbate concentrations. We report here the adsorption and desorption kinetics and equilibrium coverages of a variety of species on well-characterized surfaces as determined by SPR techniques. When the diffusion constant of the adsorbing species is known in the liquid phase, the intrinsic rate constants can be determined from the kinetic results. The sticking probability, defined as the rate of adsorption per molecular collision with the surface, directly expresses the difficulty encountered by a molecule in scaling the barrier to adsorption. Its prior use has been restricted to adsorption of gases. A method extending this concept to adsorption from liquid solutions is applied to transient measurements of alkylthiol adsorption onto gold from ethanol solutions. The initial sticking probability increases from 10-8 to 10-6 with alkyl chain length, implying a stabilization of the transition state by 0.65 kJ/mol per CH_2. Since their sticking probabilities in gas phase are 1.0, the solvent increases the activation free energy by 40 kJ/mol. Applications of gold-thin-film SPR sensors in quantifying biological interactions will be described also. A gold surface containing a few biotin headgroups in a self assembled alkylthiolate monolayer of mainly oligo(ethylene glycol) (OEG) headgroups selectively adsorbs the protein streptavidin with a structure that depends on the biotin / OEG ratio. The free biotin sites in the resulting streptavidin monolayer have been used as strong linker sites for further attachment of intact, biotinylated lipid vesicles and biotinylated, double-stranded oligonucleotides to the surface. These complex biological films then provide a

  4. Role of catechol structure in the adsorption and transformation reactions of L-DOPA in soils.

    PubMed

    Furubayashi, Akihiro; Hiradate, Syuntaro; Fujii, Yoshiharu

    2007-02-01

    3-(3',4'-Dihydroxyphenyl)-L-alanine (L-DOPA), which is synthesized in velvet bean (Mucuna pruriens), inhibits plant growth. The concentration of L-DOPA in soil is reduced by adsorption and transformation reactions, which can result in the reduction of its plant-growth-inhibitory activity. To determine which part of the L-DOPA structure is involved in the adsorption and soil transformation reactions, we compared the kinetics of L-DOPA disappearance in a volcanic ash soil with that of L-phenylalanine (3-phenyl-L-alanine) and L-tyrosine (3-(4'-hydroxyphenyl)-L-alanine), compounds that are similar in structure to L-DOPA but do not have a catechol (o-dihydroxybenzene) moiety. L-Phenylalanine and L-tyrosine were not adsorbed and transformed in the soil at equilibrium pH values between 4 and 7. These results suggest that the adsorption and transformation reactions of L-DOPA in the soil involve the catechol moiety and not the amino and carboxylic acid groups, which are common to all three compounds. Like L-DOPA, (+)-catechin, another allelochemical that contains a catechol moiety, underwent adsorption and soil transformation reactions. Thus, we concluded that the concentrations of allelochemicals bearing a catechol moiety in soils will decrease rapidly owing to adsorption and transformation reactions, and this decrease will be faster in soils with a high pH value or high adsorption ability. Owing to this decrease in concentration, allelopathic phenomena may not occur.

  5. Protein adsorption properties of OEG monolayers and dense PNIPAM brushes probed by neutron reflectivity

    NASA Astrophysics Data System (ADS)

    Brouette, N.; Xue, C.; Haertlein, M.; Moulin, M.; Fragneto, G.; Leckband, D. E.; Halperin, A.; Sferrazza, M.

    2012-11-01

    The structure of dense poly(N-isopropylacrylamide) (PNIPAM) brushes and oligo(ethylene glycol) (OEG) monolayers has been probed using neutron reflectometry and ellipsometry. The PNIPAM brush is swollen below the Lower Critical Solution Temperature (LCST) of 32 ∘C and is collapsed at 37 ∘C. Neutron reflectivity shows that below the LCST, the brush is described by a two-layer model: an inner dense layer and a hydrated outer layer. Above the LCST the collapsed brush forms a homogenous layer. With a fully deuterated myoglobin protein to increase the neutron scattering length density contrast, the reflectivity data show no detectable primary adsorption on the grafted OEG surface. A bound on the ternary adsorption onto PNIPAM chains forming dense brushes below and above the LCST is obtained.

  6. Volatile emission in dry seeds as a way to probe chemical reactions during initial asymptomatic deterioration

    PubMed Central

    Mira, Sara; Hill, Lisa M.; González-Benito, M. Elena; Ibáñez, Miguel Angel; Walters, Christina

    2016-01-01

    The nature and kinetics of reactions in dry seeds determines how long the seeds survive. We used gas chromatography to assay volatile organic compounds (VOCs) emitted from seeds of three unrelated species as a means to non-invasively probe chemical changes during very dry, dry, and humid storage (seeds were dried to 5.5, 33, and 75% relative humidity at room temperature). VOCs emitted from seeds stored in humid conditions reflected fermentation-type reactions, with methanol and ethanol being predominant in Lactuca sativa and Carum carvi, and acetaldehyde and acetone being predominant in Eruca vesicaria. Dried C. carvi seeds continued to emit fermentation-type products, although at slower rates than the seeds stored in humid conditions. In contrast, drying caused a switch in VOC emission in L. sativa and E. vesicaria seeds towards higher emission of pentane and hexanal, molecules considered to be byproducts from the peroxidation of polyunsaturated fatty acids. Longevity correlated best with the rate of fermentation-type reactions and appeared unrelated to the rate of lipid peroxidation. Emission of VOCs decreased when seed species were mixed together, indicating that seeds adsorbed VOCs. Adsorption of VOCs did not appear to damage seeds, as longevity was not affected in seed mixtures. Collectively, the study shows similarity among species in the types of reactions that occur in dry seeds, but high diversity in the substrates, and hence the byproducts, of the reactions. Moreover, the study suggests that the most abundant VOCs arise from degradation of storage reserves within seed cells, and that these reactions and their byproducts are not, in themselves, damaging. PMID:26956506

  7. Volatile emission in dry seeds as a way to probe chemical reactions during initial asymptomatic deterioration.

    PubMed

    Mira, Sara; Hill, Lisa M; González-Benito, M Elena; Ibáñez, Miguel Angel; Walters, Christina

    2016-03-01

    The nature and kinetics of reactions in dry seeds determines how long the seeds survive. We used gas chromatography to assay volatile organic compounds (VOCs) emitted from seeds of three unrelated species as a means to non-invasively probe chemical changes during very dry, dry, and humid storage (seeds were dried to 5.5, 33, and 75% relative humidity at room temperature). VOCs emitted from seeds stored in humid conditions reflected fermentation-type reactions, with methanol and ethanol being predominant in Lactuca sativa and Carum carvi, and acetaldehyde and acetone being predominant in Eruca vesicaria. Dried C. carvi seeds continued to emit fermentation-type products, although at slower rates than the seeds stored in humid conditions. In contrast, drying caused a switch in VOC emission in L. sativa and E. vesicaria seeds towards higher emission of pentane and hexanal, molecules considered to be byproducts from the peroxidation of polyunsaturated fatty acids. Longevity correlated best with the rate of fermentation-type reactions and appeared unrelated to the rate of lipid peroxidation. Emission of VOCs decreased when seed species were mixed together, indicating that seeds adsorbed VOCs. Adsorption of VOCs did not appear to damage seeds, as longevity was not affected in seed mixtures. Collectively, the study shows similarity among species in the types of reactions that occur in dry seeds, but high diversity in the substrates, and hence the byproducts, of the reactions. Moreover, the study suggests that the most abundant VOCs arise from degradation of storage reserves within seed cells, and that these reactions and their byproducts are not, in themselves, damaging. PMID:26956506

  8. Volatile emission in dry seeds as a way to probe chemical reactions during initial asymptomatic deterioration.

    PubMed

    Mira, Sara; Hill, Lisa M; González-Benito, M Elena; Ibáñez, Miguel Angel; Walters, Christina

    2016-03-01

    The nature and kinetics of reactions in dry seeds determines how long the seeds survive. We used gas chromatography to assay volatile organic compounds (VOCs) emitted from seeds of three unrelated species as a means to non-invasively probe chemical changes during very dry, dry, and humid storage (seeds were dried to 5.5, 33, and 75% relative humidity at room temperature). VOCs emitted from seeds stored in humid conditions reflected fermentation-type reactions, with methanol and ethanol being predominant in Lactuca sativa and Carum carvi, and acetaldehyde and acetone being predominant in Eruca vesicaria. Dried C. carvi seeds continued to emit fermentation-type products, although at slower rates than the seeds stored in humid conditions. In contrast, drying caused a switch in VOC emission in L. sativa and E. vesicaria seeds towards higher emission of pentane and hexanal, molecules considered to be byproducts from the peroxidation of polyunsaturated fatty acids. Longevity correlated best with the rate of fermentation-type reactions and appeared unrelated to the rate of lipid peroxidation. Emission of VOCs decreased when seed species were mixed together, indicating that seeds adsorbed VOCs. Adsorption of VOCs did not appear to damage seeds, as longevity was not affected in seed mixtures. Collectively, the study shows similarity among species in the types of reactions that occur in dry seeds, but high diversity in the substrates, and hence the byproducts, of the reactions. Moreover, the study suggests that the most abundant VOCs arise from degradation of storage reserves within seed cells, and that these reactions and their byproducts are not, in themselves, damaging.

  9. Studies on adsorption, reaction mechanisms and kinetics for photocatalytic degradation of CHD, a pharmaceutical waste.

    PubMed

    Sarkar, Santanu; Bhattacharjee, Chiranjib; Curcio, Stefano

    2015-11-01

    The photocatalytic degradation of chlorhexidine digluconate (CHD), a disinfectant and topical antiseptic and adsorption of CHD catalyst surface in dark condition has been studied. Moreover, the value of kinetic parameters has been measured and the effect of adsorption on photocatalysis has been investigated here. Substantial removal was observed during the photocatalysis process, whereas 40% removal was possible through the adsorption route on TiO2 surface. The parametric variation has shown that alkaline pH, ambient temperature, low initial substrate concentration, high TiO2 loading were favourable, though at a certain concentration of TiO2 loading, photocatalytic degradation efficiency was found to be maximum. The adsorption study has shown good confirmation with Langmuir isotherm and during the reaction at initial stage, it followed pseudo-first-order reaction, after that Langmuir Hinshelwood model was found to be appropriate in describing the system. The present study also confirmed that there is a significant effect of adsorption on photocatalytic degradation. The possible mechanism for adsorption and photocatalysis has been shown here and process controlling step has been identified. The influences of pH and temperature have been explained with the help of surface charge distribution of reacting particles and thermodynamic point of view respectively.

  10. Correlations probed in direct two-nucleon removal reactions

    SciTech Connect

    Simpson, E. C.; Tostevin, J. A.

    2010-10-15

    Final-state-exclusive momentum distributions of fast, forward-traveling residual nuclei, following two-nucleon removal from fast secondary radioactive beams of projectile nuclei, can and have now been measured. Assuming that the most important reaction mechanism is the sudden direct removal of a pair of nucleons from a set of relatively simple, active shell-model orbital configurations, such distributions were predicted to depend strongly on the total angular momentum I carried by the two nucleons--the final-state spin for spin 0{sup +} projectiles. The sensitivity of these now-accessible observables to specific details of the (correlated) two-nucleon wave functions is of importance. We clarify that it is the total orbital angular momentum L of the two nucleons that is the primary factor in determining the shapes and widths of the calculated momentum distributions. It follows that, with accurate measurements, this dependence upon the L makeup of the two-nucleon wave functions could be used to assess the accuracy of (shell- or many-body-) model predictions of these two-nucleon configurations. By using several tailored examples, with specific combinations of active two-nucleon orbitals, we demonstrate that more-subtle structure aspects may be observed, allowing such reactions to probe and/or confirm the details of theoretical model wave functions.

  11. Probing protein adsorption on a nanoparticle surface using second harmonic light scattering.

    PubMed

    Das, A; Chakrabarti, A; Das, P K

    2016-09-21

    A new application of second harmonic light scattering to probe protein physisorption on a gold nanoparticle surface in aqueous buffer is reported. The free energies of adsorption, the number of protein molecules adsorbed on the surface and the binding affinity of a moderate size protein, alcohol dehydrogenase (ADH), and a small protein, insulin, have been determined using the change in the second harmonic scattered light signal as a function of binding. Four different size gold nanoparticles from 15 to 60 nm were used to determine the effect of size on the free energy change, the affinity constant and the number of protein molecules adsorbed on the surface. All were shown to increase with an increase in size. The binding can be reversed by centrifugation, and the protein molecules can be desorbed quantitatively. The application of this method for studying thermodynamic parameters of weakly interacting biomolecules with nanoparticles for nanoparticle based diagnostic and therapeutic formulations is important. PMID:27530608

  12. The immediate effects of keyboard-based music therapy on probe reaction time.

    PubMed

    Zhang, Xiaoying; Zhou, Yue; Liu, Songhuai

    2016-07-01

    [Purpose] This study examined the immediate effects of keyboard-based music therapy on Probe Reaction Time. [Subjects and Methods] Probe Reaction Time was determined in 10 subjects by self-evaluation before and after music therapy intervention. The Probe Reaction Time was separately measured 4 times. [Results] After completion of music therapy intervention, the Probe Reaction Time in the 10 subjects was significantly decreased. [Conclusion] The results suggest that keyboard-based music therapy is an effective and novel treatment, and should be applied in clinical practice.

  13. The immediate effects of keyboard-based music therapy on probe reaction time.

    PubMed

    Zhang, Xiaoying; Zhou, Yue; Liu, Songhuai

    2016-07-01

    [Purpose] This study examined the immediate effects of keyboard-based music therapy on Probe Reaction Time. [Subjects and Methods] Probe Reaction Time was determined in 10 subjects by self-evaluation before and after music therapy intervention. The Probe Reaction Time was separately measured 4 times. [Results] After completion of music therapy intervention, the Probe Reaction Time in the 10 subjects was significantly decreased. [Conclusion] The results suggest that keyboard-based music therapy is an effective and novel treatment, and should be applied in clinical practice. PMID:27512274

  14. The immediate effects of keyboard-based music therapy on probe reaction time

    PubMed Central

    Zhang, Xiaoying; Zhou, Yue; Liu, Songhuai

    2016-01-01

    [Purpose] This study examined the immediate effects of keyboard-based music therapy on Probe Reaction Time. [Subjects and Methods] Probe Reaction Time was determined in 10 subjects by self-evaluation before and after music therapy intervention. The Probe Reaction Time was separately measured 4 times. [Results] After completion of music therapy intervention, the Probe Reaction Time in the 10 subjects was significantly decreased. [Conclusion] The results suggest that keyboard-based music therapy is an effective and novel treatment, and should be applied in clinical practice. PMID:27512274

  15. Direct coupling between stress, strain and adsorption reactions - A study on coal-CO2 systems

    NASA Astrophysics Data System (ADS)

    Hol, S.; Peach, C. J.; Spiers, C. J.

    2012-12-01

    Though it is well-known that adsorption reactions frequently assist deformation of porous rocks, very little understanding exists on the direct coupling with stress state and strain. One of the materials in which adsorption plays a large role is coal, as is observed in the particular case of Enhanced Coalbed Methane Production (ECBM), which involves the geological storage of CO2 and the recovery of CH4. In this case, adsorption and the associated swelling cause significant injectivity problems, which is experienced in almost all pilot field projects to date. This suggests that indeed a strong fundamental coupling exists between CO2 sorption, changes in the mechanical state of the coal matrix and changes in the transport properties of the system, and illustrates the need to understand coupled stress-strain-sorption behaviour. In this contribution, we describe several important observations made on coal-CO2 systems that can learn us about many other natural, stressed adsorbate-adsorbent systems. In our experiments, first of all, the adsorption of CO2 in the coal matrix gave rise to swelling. Although this is well-known, we found that the total volumetric strain occurring under unconfined conditions can be realistically modelled (up to at least 100 MPa) as the sum of an adsorption-related expansion term and an elastic compression term. Second, effective in situ stresses will directly reduce the sorption capacity, and associated swelling of the coal matrix significantly. Our general thermodynamic model for the effect of a 3D stress state on adsorbed CO2 concentration supports this observation, and also shows that "self-stressing", as a result of CO2 adsorption occurring under conditions of restricted or zero strain (i.e. fully constrained conditions), will more than double the expected in situ stresses. A constitutive equation was developed to describe the full coupling between stress state, total strain (i.e. combined strain of adsorption processes and poroelasticity

  16. Space and time-resolved probing of heterogeneous catalysis reactions using lab-on-a-chip

    NASA Astrophysics Data System (ADS)

    Navin, Chelliah V.; Krishna, Katla Sai; Theegala, Chandra S.; Kumar, Challa S. S. R.

    2016-03-01

    Probing catalytic reactions on a catalyst surface in real time is a major challenge. Herein, we demonstrate the utility of a continuous flow millifluidic chip reactor coated with a nanostructured gold catalyst as an effective platform for in situ investigation of the kinetics of catalytic reactions by taking 5-(hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic acid (FDCA) conversion as a model reaction. The idea conceptualized in this paper can not only dramatically change the ability to probe the time-resolved kinetics of heterogeneous catalysis reactions but also used for investigating other chemical and biological catalytic processes, thereby making this a broad platform for probing reactions as they occur within continuous flow reactors.Probing catalytic reactions on a catalyst surface in real time is a major challenge. Herein, we demonstrate the utility of a continuous flow millifluidic chip reactor coated with a nanostructured gold catalyst as an effective platform for in situ investigation of the kinetics of catalytic reactions by taking 5-(hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic acid (FDCA) conversion as a model reaction. The idea conceptualized in this paper can not only dramatically change the ability to probe the time-resolved kinetics of heterogeneous catalysis reactions but also used for investigating other chemical and biological catalytic processes, thereby making this a broad platform for probing reactions as they occur within continuous flow reactors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06752a

  17. Modelling active sites for the Beckmann rearrangement reaction in boron-containing zeolites and their interaction with probe molecules.

    PubMed

    Lezcano-González, Inés; Vidal-Moya, Alejandro; Boronat, Mercedes; Blasco, Teresa; Corma, Avelino

    2010-06-28

    Theoretical calculations and in situ solid state NMR spectroscopy have been combined to get insight on the nature of the active sites for the Beckmann rearrangement reaction in borosilicate zeolites. The interaction of a B site in zeolite Beta with a series of probe molecules (ammonia, pyridine, acetone and water) has been modelled and the (15)N and (11)B NMR isotropic chemical shift of the resulting complexes calculated and compared with experimental in situ NMR results. This approach has allowed validation of the methodology to model the adsorption on a zeolite boron site of molecules of varying basicity which are either protonated or non-protonated. The limitation is that theoretical calculations overestimate the effect of molecular adsorption through hydrogen bonds on the calculated isotropic (11)B NMR chemical shift.Theoretical and experimental results on the adsorption of acetophenone and cyclohexanone oximes on zeolite B-Beta indicate that Brønsted acid sites protonate the oximes, changing the boron coordination from trigonal to tetrahedral. Comparison of theoretical and experimental (15)N NMR chemical shifts of the adsorbed amides (acetanilide and epsilon-caprolactam) indicates that they are non-protonated, and the (11)B NMR spectra show that, as expected, boron remains in trigonal coordination with an isotropic delta(11)B(exp) which differs from the calculated value delta(11)B(calc).

  18. Modelling active sites for the Beckmann rearrangement reaction in boron-containing zeolites and their interaction with probe molecules.

    PubMed

    Lezcano-González, Inés; Vidal-Moya, Alejandro; Boronat, Mercedes; Blasco, Teresa; Corma, Avelino

    2010-06-28

    Theoretical calculations and in situ solid state NMR spectroscopy have been combined to get insight on the nature of the active sites for the Beckmann rearrangement reaction in borosilicate zeolites. The interaction of a B site in zeolite Beta with a series of probe molecules (ammonia, pyridine, acetone and water) has been modelled and the (15)N and (11)B NMR isotropic chemical shift of the resulting complexes calculated and compared with experimental in situ NMR results. This approach has allowed validation of the methodology to model the adsorption on a zeolite boron site of molecules of varying basicity which are either protonated or non-protonated. The limitation is that theoretical calculations overestimate the effect of molecular adsorption through hydrogen bonds on the calculated isotropic (11)B NMR chemical shift.Theoretical and experimental results on the adsorption of acetophenone and cyclohexanone oximes on zeolite B-Beta indicate that Brønsted acid sites protonate the oximes, changing the boron coordination from trigonal to tetrahedral. Comparison of theoretical and experimental (15)N NMR chemical shifts of the adsorbed amides (acetanilide and epsilon-caprolactam) indicates that they are non-protonated, and the (11)B NMR spectra show that, as expected, boron remains in trigonal coordination with an isotropic delta(11)B(exp) which differs from the calculated value delta(11)B(calc). PMID:20454729

  19. Probing effects of polymer adsorption in colloidal particle suspensions by light scattering as relevant for the aquatic environment: An overview.

    PubMed

    Tiraferri, Alberto; Borkovec, Michal

    2015-12-01

    Modification of particle surfaces by adsorption of polymers is a process that governs particle behavior in aqueous environmental systems. The present article briefly reviews the current understanding of the adsorption mechanisms and the properties of the resulting layers, and it discusses two environmentally relevant cases of particle modification by polymers. In particular, the discussion focuses on the usefulness of methods based on light scattering to probe such adsorbed layers together with the resulting properties of the particle suspensions, and it highlights advantages and disadvantages of these techniques. Measurement of the electrophoretic mobility allows to follow the development of the adsorption layer and to characterize the charge of the modified particles. At saturation, the surface charge is governed by the charge of the adsorbed film. Dynamic light scattering provides information on the film thickness and on the behavior of the modified suspensions. The charge and the structure of the adsorbed layer influence the stability of the particles, as well as the applicability of the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO). This fundamental knowledge is presented in the light of environmental systems and its significance for applied systems is underlined. In particular, the article discusses two examples of environmental processes involving adsorption of polymers, namely, the modification of particles by natural adsorption of humic substances and the tailoring of surface properties of iron-based particles used to remediate contaminated aquifers.

  20. Monte Carlo Simulations Probing the Adsorptive Separation of Hydrogen Sulfide/Methane Mixtures Using All-Silica Zeolites.

    PubMed

    Shah, Mansi S; Tsapatsis, Michael; Siepmann, J Ilja

    2015-11-10

    Selective removal of hydrogen sulfide (H2S) from sour natural gas mixtures is one of the key challenges facing the natural gas industry. Adsorption and pervaporation processes utilizing nanoporous materials, such as zeolites, can be alternatives to highly energy-intensive amine-based absorption processes. In this work, the adsorption behavior of binary mixtures containing H2S and methane (CH4) in seven different all-silica zeolite frameworks (CHA, DDR, FER, IFR, MFI, MOR, and MWW) is investigated using Gibbs ensemble Monte Carlo simulations at two temperatures (298 and 343 K) and pressures ranging from 1 to 50 bar. The simulations demonstrate high selectivities that, with the exception of MOR, increase with increasing H2S concentration due to favorable sorbate-sorbate interactions. The simulations indicate significant inaccuracies of predictions using unary adsorption data and ideal adsorbed solution theory. In addition, the adsorption of binary H2S/H2O mixtures in MFI is considered to probe whether the presence of H2S induces coadsorption and reduces the hydrophobic character of all-silica zeolites. The simulations show preferential adsorption of H2S from moist gases with a selectivity of about 18 over H2O.

  1. Protein Adsorption and Reorganization on Nanoparticles Probed by the Coffee-Ring Effect: Application to Single Point Mutation Detection.

    PubMed

    Devineau, Stéphanie; Anyfantakis, Manos; Marichal, Laurent; Kiger, Laurent; Morel, Mathieu; Rudiuk, Sergii; Baigl, Damien

    2016-09-14

    The coffee-ring effect denotes the accumulation of particles at the edge of an evaporating sessile drop pinned on a substrate. Because it can be detected by simple visual inspection, this ubiquitous phenomenon can be envisioned as a robust and cost-effective diagnostic tool. Toward this direction, here we systematically analyze the deposit morphology of drying drops containing polystyrene particles of different surface properties with various proteins (bovine serum albumin (BSA) and different forms of hemoglobin). We show that deposit patterns reveal information on both the adsorption of proteins onto particles and their reorganization following adsorption. By combining pattern analysis with adsorption isotherm and zeta potential measurements, we show that the suppression of the coffee-ring effect and the formation of a disk-shaped pattern is primarily associated with particle neutralization by protein adsorption. However, our findings also suggest that protein reorganization following adsorption can dramatically invert this tendency. Exposure of hydrophobic (respectively charged) residues can lead to disk (respectively ring) deposit morphologies independently of the global particle charge. Surface tension measurements and microscopic observations of the evaporating drops show that the determinant factor of the deposit morphology is the accumulation of particles at the liquid/gas interface during evaporation. This general behavior opens the possibility to probe protein adsorption and reorganization on particles by the analysis of the deposit patterns, the formation of a disk being the robust signature of particles rendered hydrophobic by protein adsorption. We show that this method is sensitive enough to detect a single point mutation in a protein, as demonstrated here by the distinct patterns formed by human native hemoglobin h-HbA and its mutant form h-HbS, which is responsible for sickle cell anemia. PMID:27562632

  2. Probing Isotope Effects in Chemical Reactions Using Single Ions

    SciTech Connect

    Staanum, Peter F.; Hoejbjerre, Klaus; Drewsen, Michael; Wester, Roland

    2008-06-20

    Isotope effects in reactions between Mg{sup +} in the 3p {sup 2}P{sub 3/2} excited state and molecular hydrogen at thermal energies are studied through single reaction events. From only {approx}250 reactions with HD, the branching ratio between formation of MgD{sup +} and MgH{sup +} is found to be larger than 5. From an additional 65 reactions with H{sub 2} and D{sub 2} we find that the overall fragmentation probability of the intermediate MgH{sub 2}{sup +}, MgHD{sup +}, or MgD{sub 2}{sup +} complexes is the same. Our study shows that few single ion reactions can provide quantitative information on ion-neutral reactions. Hence, the method is well suited for reaction studies involving rare species, e.g., rare isotopes or short-lived unstable elements.

  3. Probing Isotope Effects in Chemical Reactions Using Single Ions

    NASA Astrophysics Data System (ADS)

    Staanum, Peter F.; Højbjerre, Klaus; Wester, Roland; Drewsen, Michael

    2008-06-01

    Isotope effects in reactions between Mg+ in the 3p P3/22 excited state and molecular hydrogen at thermal energies are studied through single reaction events. From only ˜250 reactions with HD, the branching ratio between formation of MgD+ and MgH+ is found to be larger than 5. From an additional 65 reactions with H2 and D2 we find that the overall fragmentation probability of the intermediate MgH2+, MgHD+, or MgD2+ complexes is the same. Our study shows that few single ion reactions can provide quantitative information on ion-neutral reactions. Hence, the method is well suited for reaction studies involving rare species, e.g., rare isotopes or short-lived unstable elements.

  4. Reaction-based two-photon probes for mercury ions: fluorescence imaging with dual optical windows.

    PubMed

    Rao, Alla Sreenivasa; Kim, Dokyoung; Wang, Taejun; Kim, Ki Hean; Hwang, Sekyu; Ahn, Kyo Han

    2012-05-18

    For fluorescent imaging of mercury ions in living species, two-photon probes with dual optical windows are in high demand but remain unexplored. Several dithioacetals were evaluated, and a probe was found, which, upon reaction with mercury species, yielded a two-photon dye; this conversion accompanies ratiometric emission changes with a 97-nm shift, enabling fluorescent imaging of both the probe and mercury ions in cells by one- and two-photon microscopy for the first time.

  5. Space and time-resolved probing of heterogeneous catalysis reactions using lab-on-a-chip.

    PubMed

    Navin, Chelliah V; Krishna, Katla Sai; Theegala, Chandra S; Kumar, Challa S S R

    2016-03-14

    Probing catalytic reactions on a catalyst surface in real time is a major challenge. Herein, we demonstrate the utility of a continuous flow millifluidic chip reactor coated with a nanostructured gold catalyst as an effective platform for in situ investigation of the kinetics of catalytic reactions by taking 5-(hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic acid (FDCA) conversion as a model reaction. The idea conceptualized in this paper can not only dramatically change the ability to probe the time-resolved kinetics of heterogeneous catalysis reactions but also used for investigating other chemical and biological catalytic processes, thereby making this a broad platform for probing reactions as they occur within continuous flow reactors.

  6. Effect of UV and electrochemical surface treatments on the adsorption and reaction of linear alcohols on non-porous carbon fibre

    NASA Astrophysics Data System (ADS)

    Osbeck, S.; Ward, S.; Idriss, H.

    2013-04-01

    The adsorption properties of untreated, electrochemically treated and ultra-violet/ozone treated polyacrylonitrile based carbon fibres were investigated using temperature programmed desorption (TPD) on a series of linear alcohols as probes in order to understand its surface properties. Surface uptake was found to be sensitive to both the surface treatment and the nature of the adsorbates. Surface coverage increased with increasing alcohol chain due to the increase in their polarizability. It also increased with the level of surface oxygen of the fibres most likely because it facilitates the Osbnd H bond dissociation of the alcohol functional group. In addition, the desorption temperature (during TPD) tracked the surface oxygen levels (as determined from XPS O1s signal) suggesting increasing in the adsorption energy. The reactions of C1-C4 linear alcohols were also investigated on the surface of the fibre carbon. The main reaction was dehydrogenation to the corresponding aldehydes; the dehydration reaction to olefins was not observed. The dehydrogenation reaction was sensitive to the length of the alky chain. It was highest for methanol (to formaldehyde) and decreased with increasing the carbon number. Overall TPD of linear alcohols was shown to be a promising method for quantifying the level and strength of bonding occurring on carbon fibre surfaces.

  7. Probing cluster structures through sub-barrier transfer reactions

    NASA Astrophysics Data System (ADS)

    Rafferty, D. C.; Dasgupta, M.; Hinde, D. J.; Simenel, C.; Simpson, E. C.; Williams, E.; Carter, I. P.; Cook, K. J.; Luong, D. H.; McNeil, S. D.; Ramachandran, K.; Vo-Phuoc, K.; Wakhle, A.

    2016-09-01

    Multinucleon transfer probabilities and excitation energy distributions have been measured in 16,18O, 19F + 208Pb at energies between 90% - 100% of the Coulomb barrier. A strong 2p2n enhancement is observed for all reactions, though most spectacularly in the 18O induced reaction. Results are interpreted in terms of the Semiclassical model, which seems to suggest α-cluster transfer in all studied systems. The relation to cluster-states in the projectile is discussed, with the experimental results consistent with previous structure studies. Dissipation of energy in the collisions of 18O is compared between different reaction modes, with cluster transfer associated with dissipation over a large number of internal states. Cluster transfer is shown to be a long range dissipation mechanism, which will inform the development of future models to treat these dynamic processes in reactions.

  8. Probing of Competitive Displacement Adsorption of Casein at Oil-in-Water Interface Using Equilibrium Force Distance Measurements.

    PubMed

    Mahendran, V; Sangeetha, J; Philip, John

    2015-06-01

    The equilibrium force distance measurement is employed for the first time to probe the competitive and displacement adsorption of casein at an oil-water (O/W) emulsion interface that was initially adsorbed with either a diblock polymer or an anionic surfactant. A significant change in the force-distance profile was observed under the competitive displacement adsorption of casein, which is further confirmed from the hydrodynamic diameter and zeta potential measurements. A decrease in the onset of repulsion and decay length are observed on competitive adsorption of smaller size casein molecules at O/W interface. With addition of casein in PVA-vac diblock polymer stabilized emulsion, the onset of repulsion decreases from 88 to 48 nm whereas the magnitude of force increases from 1 to 19 nN. The force decay length is reduced from 10.5 to 4.5 nm upon addition of casein. Our results suggest the complete replacement of adsorbed diblock polymers by casein molecules. The hydrodynamic diameter and zeta potential measurements corroborate the casein mediated polymer displacement and the competitive adsorption of casein at the O/W interface. In the case of anionic surfactant covered O/W interfaces, casein molecules weakly associate at the interface without displacing the smaller size surfactant molecules where no significant changes in the onset repulsion and force profiles are observed. These results suggest that the casein molecules are effective displacers for replacement of adsorbed macromolecules from formulations, which has several important practical applications.

  9. Acetaldehyde Adsorption and Reaction onCeO2(100) Thin Films

    SciTech Connect

    Mullins, David R; Albrecht, Peter M

    2013-01-01

    This study reports and compares the adsorption and dissociation of acetaldehyde on oxidized and reduced CeOX(100) thin films. Acetaldehyde reacts and decomposes on fully oxidized CeO2(100) whereas it desorbs molecularly at low temperature on CeO2(111). The primary products are CO, CO2 and water along with trace amounts of crotonaldehyde and acetylene. The acetaldehyde adsorbs as the 2-acetaldehyde species, dioxyethylene. Decomposition proceeds by dehydrogenation through acetate and enolate intermediates. The reaction pathway is similar on the reduced CeO2-X(100) surface however the inability to react with surface O on the reduced surface results in H2 rather than H2O desorption and C is left on the surface rather than producing CO and CO2. C-O bond cleavage in the enolate intermediate followed by reaction with surface H results in ethylene desorption.

  10. Adsorption and Reaction of Acetaldehyde on Stoichiometric and Defective SrTiO₃(100) Surfaces

    SciTech Connect

    Wang, Li Q.; Ferris, Kim F.; Azad, Samina; Engelhard, Mark H.; Peden, Charles HF.

    2004-02-05

    The adsorption and reaction of acetaldehyde (CH{sub 3}CHO), on stoichiometric (TiO{sub 2}-terminated) and reduced SrTiO{sub 3}(100) surfaces, have been investigated using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Acetaldehyde adsorbs molecularly on the stoichiometric SrTiO{sub 3}(100) surface that contains predominantly Ti{sup 4+} cations. The Ti{sup 4+} sites on the stoichiometric SrTiO{sub 3}(100) surface are not sufficiently active for surface reactions such as aldol condensation, as opposed to the Ti{sup 4+} ions on the TiO{sub 2}(001) surface. However, decomposition and redox reactions of acetaldehyde occur in the presence of surface defects created by Ar{sup +} sputtering. The decomposition products following reactions of acetaldehyde on the defective surface include H{sub 2}, C{sub 2}H{sub 4}, CO, C{sub 4}H{sub 6}, and C{sub 4}H{sub 8}. Reductive coupling, to produce C{sub 2}H{sub 4} and C{sub 4}H{sub 8} is the main reaction pathway for decomposition of acetaldehyde on the sputter reduced SrTiO{sub 3}(100) surface.

  11. Probing the nuclear structure with heavy-ion reactions

    SciTech Connect

    Broglia, R.A.

    1982-01-01

    Nuclei display distortions in both ordinary space and in gauge space. It is suggested that it is possible to learn about the spatial distribution of the Nilsson orbitals and about the change of the pairing gap with the rotational frequency through the analysis of one- and two-nucleon transfer reactions induced in heavy-ion collisions.

  12. Adsorption and reactions of atmospheric constituents and pollutants on ice particles: an FTIR study

    NASA Astrophysics Data System (ADS)

    Rudakova, A. V.; Marinov, I. L.; Poretskiy, M. S.; Tsyganenko, A. A.

    2009-04-01

    Processes on icy particles attract much attention due to their importance for atmospheric science, ecology and astrophysics. In this work, adsorption and ecologically important reactions of some molecules on pure and mixed water icy films by means of FTIR spectroscopy have been investigated. The cell for spectral studies of adsorbed molecules at variable temperatures (55-370 K), described elsewhere1, enables one to run the spectra in the presence of gaseous adsorbate, and even to perform adsorption from the solution in some cryogenic solvents. For the studies of ice films, it was equipped with a device for water vapour sputtering from the heated capillaries and deposition onto the inner BaF2 or ZnSe windows of the cell, cooled by liquid nitrogen. Lower temperatures were obtained by pumping off evaporating nitrogen from the coolant volume. The estimated specific surface area of freshly deposited at 77 K water ice film was about 160 m2/g and decreases on raising the temperature together with the diminishing intensity of the bands of dangling OH (OD) groups at 3696 (2727) cm-1 until the latter disappear at 130 - 160 K when the changes of bulk absorption provide evidence for a phase transition from amorphous to polycrystalline ice. CO adsorption at 77 K results in two bands at 2153 and 2137 cm-1 assigned to molecules forming weak H-bond with the dangling hydroxyl groups and bound to unsaturated surface oxygen atoms, respectively2. The band of dangling hydroxyl groups moves to lower wavenumbers on adsorption of different molecules (hydrogen, nitrogen, methane, ozone, NO, ethane or chlorinated ethenes, etc.). The shift value depends on the nature of adsorbate. Besides this shift, spectra of adsorbed nitrogen and methane registered at 55 K reveal the adsorption intensity decrease at ~ 2650 cm-1 at the high-frequency slope of bulk adsorption, and increase at about 25 cm-1 below. We interpret this perturbation as a strengthening of H-bonds between surface water molecules

  13. Thermostatted micro-reactor NMR probe head for monitoring fast reactions.

    PubMed

    Brächer, A; Hoch, S; Albert, K; Kost, H J; Werner, B; von Harbou, E; Hasse, H

    2014-05-01

    A novel nuclear magnetic resonance (NMR) probe head for monitoring fast chemical reactions is described. It combines micro-reaction technology with capillary flow NMR spectroscopy. Two reactants are fed separately into the probe head where they are effectively mixed in a micro-mixer. The mixed reactants then pass through a capillary NMR flow cell that is equipped with a solenoidal radiofrequency coil where the NMR signal is acquired. The whole flow path of the reactants is thermostatted using the liquid FC-43 (perfluorotributylamine) so that exothermic and endothermic reactions can be studied under almost isothermal conditions. The set-up enables kinetic investigation of reactions with time constants of only a few seconds. Non-reactive mixing experiments carried out with the new probe head demonstrate that it facilitates the acquisition of constant highly resolved NMR signals suitable for quantification of different species in technical mixtures. Reaction kinetic measurements on a test system are presented that prove the applicability of the novel NMR probe head for monitoring fast reactions.

  14. Thermostatted micro-reactor NMR probe head for monitoring fast reactions

    NASA Astrophysics Data System (ADS)

    Brächer, A.; Hoch, S.; Albert, K.; Kost, H. J.; Werner, B.; von Harbou, E.; Hasse, H.

    2014-05-01

    A novel nuclear magnetic resonance (NMR) probe head for monitoring fast chemical reactions is described. It combines micro-reaction technology with capillary flow NMR spectroscopy. Two reactants are fed separately into the probe head where they are effectively mixed in a micro-mixer. The mixed reactants then pass through a capillary NMR flow cell that is equipped with a solenoidal radiofrequency coil where the NMR signal is acquired. The whole flow path of the reactants is thermostatted using the liquid FC-43 (perfluorotributylamine) so that exothermic and endothermic reactions can be studied under almost isothermal conditions. The set-up enables kinetic investigation of reactions with time constants of only a few seconds. Non-reactive mixing experiments carried out with the new probe head demonstrate that it facilitates the acquisition of constant highly resolved NMR signals suitable for quantification of different species in technical mixtures. Reaction kinetic measurements on a test system are presented that prove the applicability of the novel NMR probe head for monitoring fast reactions.

  15. Low Energy Electrons as Probing Tool for Astrochemical Reaction Mechanisms

    NASA Astrophysics Data System (ADS)

    Hendrik Bredehöft, Jan; Swiderek, Petra; Hamann, Thorben

    The complexity of molecules found in space varies widely. On one end of the scale of molecular complexity is the hydrogen molecule H2 . Its formation from H atoms is if not understood than at least thoroughly investigated[1]. On the other side of said spectrum the precursors to biopolymers can be found, such as amino acids[2,3], sugars[4], lipids, cofactors[5], etc, and the kerogen-like organic polymer material in carbonaceous meteorites called "black stuff" [6]. These have also received broad attention in the last decades. Sitting in the middle between these two extremes are simple molecules that are observed by radio astronomy throughout the Universe. These are molecules like methane (CH4 ), methanol (CH3 OH), formaldehyde (CH2 O), hydrogen cyanide (HCN), and many many others. So far more than 40 such species have been identified.[7] They are often used in laboratory experiments to create larger complex molecules on the surface of simulated interstellar dust grains.[2,8] The mechanisms of formation of these observed starting materials for prebiotic chemistry is however not always clear. Also the exact mechanisms of formation of larger molecules in photochemical experiments are largely unclear. This is mostly due to the very complex chemistry going on which involves many different radicals and ions. The creation of radicals and ions can be studied in detail in laboratory simulations. They can be created in a setup mimicking interstellar grain chemistry using slow electrons. There is no free electron radiation in space. What can be found though is a lot of radiation of different sorts. There is electromagnetic radiation (UV light, X-Rays, rays, etc.) and there is particulate radiation as well in the form of high energy ions. This radiation can provide energy that drives chemical reactions in the ice mantles of interstellar dust grains. And while the multitude of different kinds of radiation might be a little confusing, they all have one thing in common: Upon

  16. Theory of quasicrystal surfaces: Probing the chemical reactivity by atomic and molecular adsorption

    NASA Astrophysics Data System (ADS)

    Krajčí, M.; Hafner, J.

    The adsorption of oxygen and carbon atoms and of carbon monoxide molecules on a fivefold surface of icosahedral Al-Pd-Mn quasicrystals has been investigated using ab initio density-functional calculations. The quasicrystalline surface has been modeled by periodically repeated slabs cut from rational approximants to the quasicrystalline structure. Atomic and molecular adsorption have been studied for a large number of possible adsorption sites by performing three-dimensional static relaxations of the adsorbate/substrate complex. Four different scenarios for the dissociative adsorption of the CO molecule have been investigated via nudged-elastic band calculations of the transition states. Al and Mn-metal atoms present at the surface bind C and O atoms rather strongly, while Pd atoms are unstable adsorption sites: during relaxation, the adsorbate drifts to the nearest strong-binding site. The chemical reactivity with respect to a CO molecule varies very strongly across the surface. The adsorption close to Mn sites is promoted by rather strong covalent effects, but CO is only physisorbed at Al sites via weak polarization forces. On the basis of the observed local variations of the adsorption strength, we develop scenarios for dissociation and determine the potential energy barriers for this processes. We find that CO adsorbed close to a transition-metal atom can dissociate via an activated process, but the dissociation rate is expected to be rather low because of a high dissociation barrier and a "late" transition state. CO adsorbed close to Al atoms will desorb before dissociation. Surface vacancies present as a consequence of the irregular coordination of the Mackay cluster in the quasiperiodic structure will act as strongly attractive traps for diffusing molecules. Mn surface atoms are located in the center of truncated Mackay clusters. In scanning tunneling electron microscopy (STM) these truncated clusters are imaged as "white flowers". Surface vacancies are

  17. Polymerase Chain Reaction-based Suppression of Repetitive Sequences in Whole Chromosome Painting Probes for FISH

    SciTech Connect

    Dugan, L C; Pattee, M; Williams, J; Eklund, M; Bedford, J S; Christian, A T

    2004-04-21

    We have developed a method to suppress the PCR amplification of repetitive sequences in whole chromosome painting probes by adding Cot-1 DNA to the amplification mixture. The repetitive sequences in the Cot-1 DNA bind to their homologous sequences in the probe library, prevent the binding of primers, and interfere with extension of the probe sequences, greatly decreasing PCR efficiency selectively across these blocked regions. A second labeling reaction is then done and this product is resuspended in FISH hybridization mixture without further addition of blocking DNA. The hybridization produces little if any non-specific binding on any other chromosomes. We have been able to successfully use this procedure with both human and rat chromosome probes. This technique should be applicable in producing probes for CGH, M-FISH and SKY, as well as reducing the presence of repetitive DNA in genomic libraries.

  18. Adsorption, Ordering, and Local Environments of Surfactant-Encapsulated Polyoxometalate Ions Probed at the Air–Water Interface

    DOE PAGES

    Doughty, Benjamin; Yin, Panchao; Ma, Ying-Zhong

    2016-07-23

    The continued development and application of surfactant-encapsulated polyoxometalates (SEPs) relies on understanding the ordering and organization of species at their interface and how these are impacted by the various local environments to which they are exposed. In this paper, we report on the equilibrium properties of two common SEPs adsorbed to the air–water interface and probed with surface-specific vibrational sum-frequency generation (SFG) spectroscopy. These results reveal clear shifts in vibrational band positions, the magnitude of which scales with the charge of the SEP core, which is indicative of a static field effect on the surfactant coating and the associated localmore » chemical environment. This static field also induces ordering in surrounding water molecules that is mediated by charge screening via the surface-bound surfactants. From these SFG measurements, we are able to show that Mo132-based SEPs are more polar than Mo72V30 SEPs. Disorder in the surfactant chain packing at the highly curved SEP surfaces is attributed to large conic volumes that can be sampled without interactions with neighboring chains. Measurements of adsorption isotherms yield free energies of adsorption to the air–water interface of -46.8 ± 0.4 and -44.8 ± 1.2 kJ/mol for the Mo132 and Mo72V30 SEPs, respectively, indicating a strong propensity for the fluid surface. Finally, the influence of intermolecular interactions on the surface adsorption energies is discussed.« less

  19. Adsorption, Ordering, and Local Environments of Surfactant-Encapsulated Polyoxometalate Ions Probed at the Air-Water Interface.

    PubMed

    Doughty, Benjamin; Yin, Panchao; Ma, Ying-Zhong

    2016-08-16

    The continued development and application of surfactant-encapsulated polyoxometalates (SEPs) relies on understanding the ordering and organization of species at their interface and how these are impacted by the various local environments to which they are exposed. Here, we report on the equilibrium properties of two common SEPs adsorbed to the air-water interface and probed with surface-specific vibrational sum-frequency generation (SFG) spectroscopy. These results reveal clear shifts in vibrational band positions, the magnitude of which scales with the charge of the SEP core, which is indicative of a static field effect on the surfactant coating and the associated local chemical environment. This static field also induces ordering in surrounding water molecules that is mediated by charge screening via the surface-bound surfactants. From these SFG measurements, we are able to show that Mo132-based SEPs are more polar than Mo72V30 SEPs. Disorder in the surfactant chain packing at the highly curved SEP surfaces is attributed to large conic volumes that can be sampled without interactions with neighboring chains. Measurements of adsorption isotherms yield free energies of adsorption to the air-water interface of -46.8 ± 0.4 and -44.8 ± 1.2 kJ/mol for the Mo132 and Mo72V30 SEPs, respectively, indicating a strong propensity for the fluid surface. The influence of intermolecular interactions on the surface adsorption energies is discussed. PMID:27452922

  20. Passivation effects on quantum dots prepared by successive ionic layer adsorption and reaction.

    PubMed

    Dai, Qilin; Maloney, Scott; Chen, Weimin; Poudyal, Uma; Wang, Wenyong

    2016-06-01

    ZnS is typically used to passivate semiconductor quantum dots (QDs) prepared by the successive ionic layer adsorption and reaction (SILAR) method for solar cell applications, while for colloidal QDs, organic ligands are usually used for this passivation purpose. In this study we utilized oleylamine and oleic acid ligands, besides ZnS, to passivate QDs prepared by the SILAR approach, and investigated their effects on the incident photon-to-current efficiency (IPCE) performance of the solar cells. It was observed that oleylamine passivation decreased device performance, while oleic acid passivation improved the IPCE of the cells. Redshift of the IPCE onset wavelength was also observed after oleic acid coating, which was attributed to the delocalization of excitons in the CdS QDs. PMID:27103144

  1. Growth of polyaniline nanofibers for supercapacitor applications using successive ionic layer adsorption and reaction (SILAR) method

    NASA Astrophysics Data System (ADS)

    Deshmukh, P. R.; Pusawale, S. N.; Shinde, N. M.; Lokhande, C. D.

    2014-07-01

    We report the synthesis of polyaniline nanofibers using the successive ionic layer adsorption and reaction (SILAR) method. The structural study shows the amorphous nature of polyaniline. The formation of polyaniline nanofibers has been revealed by scanning electron microscopy (SEM) whereas the confirmation of polyaniline material is obtained from Fourier transform infrared (FT-IR) spectroscopy. A plausible explanation illustrating the growth mechanism is presented. A maximum specific capacitance of 1078 F.g-1 at a scan rate of 5 mV.s-1 is obtained. The charge-discharge behavior shows a maximum specific power of 1.2 kW.kg-1 and specific energy of 64 Wh.kg-1. The ease of the synthesis and the interesting electrochemical properties indicate that polyaniline nanofibers are promising materials for supercapacitor applications.

  2. Kinetic adsorption profile and conformation evolution at the DNA-gold nanoparticle interface probed by dynamic light scattering.

    PubMed

    Wang, Wenjie; Ding, XiaoFan; He, Miao; Wang, Jing; Lou, Xinhui

    2014-10-21

    The kinetic adsorption profile at the DNA-gold nanoparticle (AuNP) interface is probed by following the binding and organization of thiolated linear DNA and aptamers of varying chain lengths (15, 30, 44, and 51 mer) to the surface of AuNPs (13.0 ± 1.0 nm diameter). A systematic investigation utilizing dynamic light scattering has been performed to directly measure the changes in particle size during the course of a typical aging-salting thiolated DNA/AuNP preparation procedure. We discuss the effect of DNA chain length, composition, salt concentration, and secondary structure on the kinetics and conformation at the DNA-AuNP interface. The adsorption kinetics are chain-length dependent, composition independent, and not diffusion rate limited for the conditions we report here. The kinetic data support a mechanism of stepwise adsorption of thiols to the surface of AuNPs and reorganization of the thiols at the interface. Very interestingly, the kinetic increases of the particle sizes are modeled accurately by the pseudo-second-order rate model, suggesting that DNA could possess the statistically well-defined conformational evolution. Together with other experimental evidence, we propose a dynamic inner-layer and outer-tail (DILOT) model to describe the evolution of the DNA conformation after the initial adsorption of a single oligonucleotide layer. According to this model, the length of the tails that extend from the surface of AuNPs, capable for hybridization or molecular recognition, can be conveniently calculated. Considering the wide applications of DNA/AuNPs, the results should have important implications in sensing and DNA-directed nanoparticle assembly.

  3. Kinetic Adsorption Profile and Conformation Evolution at the DNA-Gold Nanoparticle Interface Probed by Dynamic Light Scattering

    PubMed Central

    2015-01-01

    The kinetic adsorption profile at the DNA–gold nanoparticle (AuNP) interface is probed by following the binding and organization of thiolated linear DNA and aptamers of varying chain lengths (15, 30, 44, and 51 mer) to the surface of AuNPs (13.0 ± 1.0 nm diameter). A systematic investigation utilizing dynamic light scattering has been performed to directly measure the changes in particle size during the course of a typical aging-salting thiolated DNA/AuNP preparation procedure. We discuss the effect of DNA chain length, composition, salt concentration, and secondary structure on the kinetics and conformation at the DNA–AuNP interface. The adsorption kinetics are chain-length dependent, composition independent, and not diffusion rate limited for the conditions we report here. The kinetic data support a mechanism of stepwise adsorption of thiols to the surface of AuNPs and reorganization of the thiols at the interface. Very interestingly, the kinetic increases of the particle sizes are modeled accurately by the pseudo-second-order rate model, suggesting that DNA could possess the statistically well-defined conformational evolution. Together with other experimental evidence, we propose a dynamic inner-layer and outer-tail (DILOT) model to describe the evolution of the DNA conformation after the initial adsorption of a single oligonucleotide layer. According to this model, the length of the tails that extend from the surface of AuNPs, capable for hybridization or molecular recognition, can be conveniently calculated. Considering the wide applications of DNA/AuNPs, the results should have important implications in sensing and DNA-directed nanoparticle assembly. PMID:25222203

  4. Structure of 13Be probed via secondary-beam reactions

    NASA Astrophysics Data System (ADS)

    Randisi, G.; Leprince, A.; Al Falou, H.; Orr, N. A.; Marqués, F. M.; Achouri, N. L.; Angélique, J.-C.; Ashwood, N.; Bastin, B.; Bloxham, T.; Brown, B. A.; Catford, W. N.; Curtis, N.; Delaunay, F.; Freer, M.; de Góes Brennand, E.; Haigh, P.; Hanappe, F.; Harlin, C.; Laurent, B.; Lecouey, J.-L.; Ninane, A.; Patterson, N.; Price, D.; Stuttgé, L.; Thomas, J. S.

    2014-03-01

    The low-lying level structure of the unbound neutron-rich nucleus 13Be has been investigated via breakup on a carbon target of secondary beams of 14,15B at 35 MeV/nucleon. The coincident detection of the beam velocity 12Be fragments and neutrons permitted the invariant mass of the 12Be+n and 12Be+n+n systems to be reconstructed. In the case of the breakup of 15B, a very narrow structure at threshold was observed in the 12Be+n channel. Analysis of the 12Be+n+n events demonstrated that this resulted from the sequential decay of the unbound 14Be(2+) state rather than a strongly interacting s-wave virtual state in 13Be, as had been surmised in stable beam fragmentation studies. Single-proton removal from 14B was found to populate a broad low-lying structure some 0.7 MeV above the neutron-decay threshold, in addition to a less prominent feature at around 2.4 MeV. Based on the selectivity of the reaction and a comparison with (0-3)ℏω shell-model calculations, the low-lying structure is concluded to arise from closely spaced Jπ=1/2+ and 5/2+ resonances (Er=0.40±0.03 and 0.85-0.11+0.15 MeV), while the broad higher-lying feature is a second 5/2+ level (Er=2.35±0.14 MeV). Taken in conjunction with earlier studies, the results suggest that the lowest 1/2+ and 1/2- levels lie relatively close together below 1 MeV.

  5. Intramolecular anodic olefin coupling reactions: using competition studies to probe the mechanism of oxidative cyclization reactions.

    PubMed

    Xu, Hai-Chao; Moeller, Kevin D

    2010-04-16

    A competition experiment was designed so that the relative rates of anodic cyclization reactions under various electrolysis conditions can be determined. Reactions with ketene dithioacetal and enol ether-based substrates that use lithium methoxide as a base were shown to proceed through radical cation intermediates that were trapped by a sulfonamide anion. Results for the oxidative coupling of a vinyl sulfide with a sulfonamide anion using the same conditions were consistent with the reaction proceeding through a nitrogen-radical.

  6. Probing Intramolecular versus Intermolecular CO2 Adsorption on Amine-Grafted SBA-15.

    PubMed

    Yoo, Chun-Jae; Lee, Li-Chen; Jones, Christopher W

    2015-12-15

    A mesoporous silica SBA-15 is modified with an array of amine-containing organosilanes including (i) propylamine, SiCH2CH2CH2NH2 (MONO), (ii) propylethylenediamine, SiCH2CH2CH2NHCH2CH2NH2 (DI), (iii) propyldiethylenetriamine, SiCH2CH2CH2NHCH2CH2NHCH2CH2NH2 (TRI), and (iv) propyltriethylenetetramine, SiCH2CH2CH2NHCH2CH2N(CH2CH2NH2)2 (TREN) and the low loading silane adsorbents (∼0.45 mmol silane/g) are evaluated for their CO2 adsorption properties, with a focus on gaining insight into the propensity for intramolecular vs intermolecular CO2 adsorption. Adsorption isotherms at low CO2 coverages are measured while simultaneously recording the heat evolved via a Tian-Calvet calorimeter. The results are compared on a silane molecule efficiency basis (mol CO2 adsorbed/mol silane) to assess the potential for intramolecular CO2 adsorption, employing two amine groups in a single silane molecule. As the number of amines in the silane molecule increases (MONO < DI < TREN ∼ TRI), the silane molecule efficiency is enhanced owing to the ability to intramolecularly capture CO2. Analysis of the CO2 uptake for samples with the surface silanols removed by capping demonstrates that cooperative uptake due to amine-CO2-silanol interactions is also possible over these adsorbents and is the primary mode of sorption for the MONO material at the studied low silane loading. As the propensity for intramolecular CO2 capture increases due to the presence of multiple amines in a single silane molecule (MONO < DI < TREN ∼ TRI), the measured heat of adsorption also increases. This study of various amine-containing silanes at low coverage is the first to provide significant, direct evidence for intramolecular CO2 capture in a single silane molecule. Furthermore, it provides evidence for the relative heats of adsorption for physisorption on a silanol laden surface (ca. 37 kJ/mol), a silanol-capped surface (ca. 25 kJ/mol), via amine-CO2-silanol interactions (ca. 46 kJ/mol), and via amine-CO2

  7. Volatile emission in dry seeds as a way to probe chemical reactions during initial asymptomatic deterioration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The nature and kinetics of reactions in dry seeds determines how long they survive. We used gas chromatography to assay volatile organic compounds (VOC) emitted from seeds of three unrelated species as a means to non-invasively probe chemical changes during very dry, dry and humid (15, 33 and 75% RH...

  8. Elementary Steps of Syngas Reactions on Mo2C(001): Adsorption Thermochemistry and Bond Dissociation

    SciTech Connect

    Medford, Andrew

    2012-02-16

    Density functional theory (DFT) and ab initio thermodynamics are applied in order to investigate the most stable surface and subsurface terminations of Mo{sub 2}C(001) as a function of chemical potential and in the presence of syngas. The Mo-terminated (001) surface is then used as a model surface to evaluate the thermochemistry and energetic barriers for key elementary steps in syngas reactions. Adsorption energy scaling relations and Broensted-Evans-Polanyi relationships are established and used to place Mo{sub 2}C into the context of transition metal surfaces. The results indicate that the surface termination is a complex function of reaction conditions and kinetics. It is predicted that the surface will be covered by either C{sub 2}H{sub 2} or O depending on conditions. Comparisons to transition metals indicate that the Mo-terminated Mo{sub 2}C(001) surface exhibits carbon reactivity similar to transition metals such as Ru and Ir, but is significantly more reactive towards oxygen.

  9. Adsorption structure, thermal reaction and initial pathways of 1,2-benzyne on Cu(100)

    NASA Astrophysics Data System (ADS)

    Lin, Jong-Liang; Lin, Yi-Shiue; Lin, Bo-Chiuan; Liao, Yuan-Hsuan; Chen, Yi-Ting; Chen, Shang-Wei; Jhuang, Jyun-Yi; Lee, Yarong; Lin, Jiing-Chyuan

    2016-10-01

    1,2-C6H4I2 is used as precursor to generate 1,2-C6H4 (ortho-C6H4) on Cu(100). The reflection-absorption infrared spectroscopy (RAIRS) confirms the vertical adsorption geometry of 1,2-C6H4 on Cu(100), which agrees with that predicted theoretically. H2 evolving between 620 K and 870 K is the only reaction product detected from the 1,2-C6H4 decomposition in temperature-programmed reaction/desorption (TPR/D). Our calculations indicate that the 1,2-C6H4 primarily undergoes C3-H bond scission, forming 1,2,3-C6H3, with distorted C6 ring, and H atom on the surface without ring rupture (C1-C2 bond dissociation) prior to H loss. Furthermore, isomerization of the 1,2-C6H4, if it does occur, may proceed via dehydrogenation-hydrogenation, instead of H-shift.

  10. Water adsorption on TiO2 surfaces probed by soft X-ray spectroscopies: bulk materials vs. isolated nanoparticles

    PubMed Central

    Benkoula, Safia; Sublemontier, Olivier; Patanen, Minna; Nicolas, Christophe; Sirotti, Fausto; Naitabdi, Ahmed; Gaie-Levrel, François; Antonsson, Egill; Aureau, Damien; Ouf, François-Xavier; Wada, Shin-Ichi; Etcheberry, Arnaud; Ueda, Kiyoshi; Miron, Catalin

    2015-01-01

    We describe an experimental method to probe the adsorption of water at the surface of isolated, substrate-free TiO2 nanoparticles (NPs) based on soft X-ray spectroscopy in the gas phase using synchrotron radiation. To understand the interfacial properties between water and TiO2 surface, a water shell was adsorbed at the surface of TiO2 NPs. We used two different ways to control the hydration level of the NPs: in the first scheme, initially solvated NPs were dried and in the second one, dry NPs generated thanks to a commercial aerosol generator were exposed to water vapor. XPS was used to identify the signature of the water layer shell on the surface of the free TiO2 NPs and made it possible to follow the evolution of their hydration state. The results obtained allow the establishment of a qualitative determination of isolated NPs’ surface states, as well as to unravel water adsorption mechanisms. This method appears to be a unique approach to investigate the interface between an isolated nano-object and a solvent over-layer, paving the way towards new investigation methods in heterogeneous catalysis on nanomaterials. PMID:26462615

  11. Surface adsorption and hopping cause probe-size-dependent microrheology of actin networks

    NASA Astrophysics Data System (ADS)

    He, Jun; Tang, Jay X.

    2011-04-01

    A network of filaments formed primarily by the abundant cytoskeletal protein actin gives animal cells their shape and elasticity. The rheological properties of reconstituted actin networks have been studied by tracking micron-sized probe beads embedded within the networks. We investigate how microrheology depends on surface properties of probe particles by varying the stickiness of their surface. For this purpose, we chose carboxylate polystyrene (PS) beads, silica beads, bovine serum albumin (BSA) -coated PS beads, and polyethylene glycol (PEG) -grafted PS beads, which show descending stickiness to actin filaments, characterized by confocal imaging and microrheology. Probe size dependence of microrheology is observed for all four types of beads. For the slippery PEG beads, particle-tracking microrheology detects weaker networks using smaller beads, which tend to diffuse through the network by hopping from one confinement “cage” to another. This trend is reversed for the other three types of beads, for which microrheology measures stiffer networks for smaller beads due to physisorption of nearby filaments to the bead surface. We explain the probe size dependence with two simple models. We also evaluate depletion effect near nonadsorption bead surface using quantitative image analysis and discuss the possible impact of depletion on microrheology. Analysis of these effects is necessary in order to accurately define the actin network rheology both in vitro and in vivo.

  12. Adsorption, Coadsorption and Reaction of Acetaldehyde and NO₂ on Na-Y,FAU: an in situ FTIR Investigation

    SciTech Connect

    Szanyi, Janos; Kwak, Ja Hun; Moline, Ryan A.; Peden, Charles HF

    2004-11-04

    The adsorption of acetaldehyde and its co-adsorption and reaction with NO₂ were investigated on a Na-Y, FAU zeolite using in situ FTIR spectroscopy. Acetaldehyde adsorbs strongly over Na-Y and desorbs molecularly at around 400K with very limited extent of condensation or polymerization. Reaction between CH₃CHO and NO₂ takes place in co-adsorption experiments even at 300K. In the initial step, acetaldehyde is oxidized to acetic acid accompanied by the formation of NO, which can be observed as N2O₃ formed via a further reaction between NO and NO₂. The key intermediates in the overall NOx reduction in this process are nitro- and nitrosomethane, which form in the next step. Their decomposition and further reaction with adsorbed NOx species lead to the formation of HCN, HNCO, N₂O, CO₂ and organic nitrile species identified by their characteristic IR vibrational signatures. At 473K, the reaction between adsorbed CH₃CHO and NO₂ is very fast. The results seem to suggest a mechanism in which N-N bond formation takes place among ionic nitrogen containing species (NO⁺ and CN⁻ or NCO⁻). No evidence has been found to suggest the participation of NHx⁺NOy⁻ type species in the N⁻N bond formation under the experimental conditions of this study.

  13. Adsorption of acridine on silver electrode: SERS spectra potential dependence as a probe of adsorbate state

    NASA Astrophysics Data System (ADS)

    Solovyeva, Elena V.; Myund, Liubov A.; Dem'yanchuk, Evgeniya M.; Makarov, Artiom A.; Denisova, Anna S.

    2013-02-01

    This work investigates acridine adsorption on the silver electrode surface. The dependence of the acridine SERS spectra on the electrode potential proved to be quite different for azaheterocycle molecules, while the pH effect as expected. The changes in the acridine SERS spectrum caused by the double electric layer (DEL) rearrangement can be explained by sorption/desorption rather than the adsorbate molecule reorientation. The presence of chloride anions close to the silver surface is important not only for the SERS-active properties but for the formation of the stabilised surface complexes of the protonated acridine as well.

  14. Probing thyroglobulin in undiluted human serum based on pattern recognition and competitive adsorption of proteins

    NASA Astrophysics Data System (ADS)

    Wang, Ran; Huang, Shuai; Li, Jing; Chae, Junseok

    2014-10-01

    Thyroglobulin (Tg) is a sensitive indicator of persistent or recurrent differentiated thyroid cancer of follicular cell origin. Detection of Tg in human serum is challenging as bio-receptors, such as anti-Tg, used in immunoassay have relatively weak binding affinity. We engineer sensing surfaces using the competitive adsorption of proteins, termed the Vroman Effect. Coupled with Surface Plasmon Resonance, the "cross-responsive" interactions of Tg on the engineered surfaces produce uniquely distinguishable multiple signature patterns, which are discriminated using Linear Discriminant Analysis. Tg-spiked samples, down to 2 ng/ml Tg in undiluted human serum, are sensitively and selectively discriminated from the control (undiluted human serum).

  15. A highly sensitive aptasensor for OTA detection based on hybridization chain reaction and fluorescent perylene probe.

    PubMed

    Wang, Bin; Wu, Yuanya; Chen, Yanfen; Weng, Bo; Xu, Liqun; Li, Changming

    2016-07-15

    An optical aptasensor was developed for ultrasensitive detection of ochratoxin A (OTA) based on hybridization chain reaction (HCR) amplification strategy and fluorescent perylene probe (PAPDI)/DNA composites. Dendritic DNA concatamers were synthesized by HCR strategy and modified on magnetic nanoparticles through aptamer as medium. A large amount of PAPDI probe aggregated under the induction of DNA concatamers and caused fluorescence quenching. In the presence of OTA, the PAPDI/DNA composites were released from magnetic nanoparticles due to the strong affinity between aptamer and OTA. In ethanol, PAPDI monomers disaggregated and produced strong fluorescence. The present method displays excellent sensitivity and selectivity towards OTA.

  16. Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution: II. Polycondensations

    NASA Technical Reports Server (NTRS)

    Kolb, V.; Orgel, L. E.

    1995-01-01

    We have prepared a [32P]-labeled oligonucleotide probe carrying a ureido (-NH-CO-NH2) function at its 3'-terminus. This labeled oligomer was used to study polycondensations of urea and formaldehyde and of various phenols and formaldehyde in aqueous solution. The formation of formaldehyde copolymers attached to the amido-function of the probe was monitored by gel electrophoresis. Our results are generally in agreement with those obtained using conventional techniques. Our method is suitable for monitoring potentially prebiotic polycondensation reactions involving formaldehyde.

  17. Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution. 2: Polycondensations

    NASA Technical Reports Server (NTRS)

    Kolb, Vera; Orgel, Leslie E.

    1995-01-01

    We have prepared a (P-32)-labeled oligonucleotide probe carrying a ureido (-NH-CO-NH2) function at its 3'-terminus. This labeled oligomer was used to study polycondensations of urea and formaldehyde and of various phenols and formaldehyde in aqueous solution. The formation of formaldehyde copolymers attached to the amido-function of the probe was monitored by gel electrophoresis. Our results are generally in agreement with those obtained using conventional techniques. Our method is suitable for monitoring potentially prebiotic polycondensation reactions involving formaldehyde.

  18. Probing the contribution of different intermolecular forces to the adsorption of spheroproteins onto hydrophilic surfaces.

    PubMed

    Borges, João; Campiña, José M; Silva, A Fernando

    2013-12-27

    Protein adsorption is a delicate process, which results from the balance between the properties of proteins and their solid supports. Although the relevance of some of these parameters has been already unveiled, the precise involvement of electrostatics and other weaker intermolecular forces requires further comprehension. Aiming to contribute to this task, this work explores the attachment, rearrangement, and surface aggregation of a model spheroprotein, such as bovine β-lactoglobulin (β-LG), onto hydrophilic substrates prefunctionalized with different alkylthiol films. Thereby, a variety of electrostatic scenarios for the adsorption of β-LG could be recreated through the variation of the pH and the functional chemistry of the surfaces. The changes in surface mass density (plus associated water) and film flexibility were followed in situ with quartz crystal microbalance with dissipation monitoring. Film packing and aggregation were assessed by faradaic electrochemical measurements and ex situ atomic force microscopy and field effect scanning electron microscopy. In contrast to previous hypotheses arguing that electrostatic interactions between charged substrates and proteins would be the only driving force, a complex interplay between Coulombic and non-Coulombic intermolecular forces (which would depend upon the experimental conditions) has been suggested to explain the results.

  19. Facile Synthesis of Prussian Blue Derivate-Modified Mesoporous Material via Photoinitiated Thiol-Ene Click Reaction for Cesium Adsorption.

    PubMed

    Qian, Jun; Ma, Jiaqi; He, Weiwei; Hua, Daoben

    2015-08-01

    A novel strategy to synthesize a functional mesoporous material for efficient removal of cesium is reported. Specifically, Prussian blue derivate-modified SBA-15 (SBA-15@FC) was prepared by photoinitiated thiol-ene reaction between thiol-modified SBA-15 and pentacyano(4-vinyl pyridine)ferrate complex. The effects of weight percentage of the Prussian blue derivate, pH, adsorbent dose, co-existing ions, and initial concentration were evaluated on the adsorption of cesium ions. The adsorption kinetically follows a pseudo-second-order model and reaches equilibrium within 2 h with a high adsorption capacity of about 13.90 mg Cs g(-1) , which indicates that SBA-15@FC is a promising adsorbent to effectively remove cesium from aqueous solutions.

  20. ZnS nanostructured thin-films deposited by successive ionic layer adsorption and reaction

    NASA Astrophysics Data System (ADS)

    Deshmukh, S. G.; Jariwala, Akshay; Agarwal, Anubha; Patel, Chetna; Panchal, A. K.; Kheraj, Vipul

    2016-04-01

    ZnS thin films were grown on glass substrate using successive ionic layer adsorption and reaction (SILAR) technique at room temperature. Aqueous solutions of ZnCl2 and Na2S were used as precursors. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy and optical absorption measurements were applied to study the structural, surface morphology and optical properties of as-deposited ZnS thin films. The X-ray diffraction profiles revealed that ZnS thin films consist of crystalline grains with cubic phase. Spherical nano grains of random size and well covered on the glass substrate were observed from FESEM. The average grain size were found to be 77 nm, 100 nm and 124 nm for 20 cycles, 40 cycles and 60 cycles samples respectively. For 60 cycle sample, Raman spectra show two prominent peaks at 554 cm-1 and 1094 cm-1. The optical band gap values were found to be 3.76 eV, 3.72 eV and 3.67 eV for 20 cycle, 40 cycle and 60 cycle samples respectively.

  1. Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution

    NASA Technical Reports Server (NTRS)

    Kolb, V.; Orgel, L. E.; Miller, S. L. (Principal Investigator)

    1994-01-01

    We have prepared a [32P]-labled oligonucleotide probe carrying a free primary amine at its 3'-terminus. This probe is used to initiate polymerization of aziridine (ethyleneimine) in aqueous solution. The nature of the oligomeric products and the kinetics of their formation are then monitored by gel electrophoresis. Our results are generally consistent with those obtained using conventional techniques. We have also investigated the effect of polyanionic templates on the rate of oligomerization of aziridine. We find that water-soluble polyanions generally accelerate the polymerization. The sodium salt of polymethacrylic acid is the most effective of the templates that we studied. The methods introduced in this paper should be applicable to a variety of polymerization reactions in aqueous solution. They should greatly simplify the screening of potentially prebiotic polymerization reactions.

  2. A simple RNA probe system for analysis of Listeria monocytogenes polymerase chain reaction products.

    PubMed Central

    Blais, B W; Phillippe, L M

    1993-01-01

    The synthesis of an RNA probe specific for the hlyA gene of Listeria monocytogenes by in vitro transcription from a polymerase chain reaction (PCR)-generated template incorporating bacteriophage T7 promoter sequences is described. This simple method produced a high yield of RNA which hybridized specifically with hlyA PCR products on a membrane, resulting in RNA-DNA hybrids which were detected by an immunoenzymatic assay with an anti-RNA-DNA hybrid antibody. The RNA probe hybridization system was more sensitive in the analysis of the PCR products than was the conventional agarose gel electrophoresis method. When applied to the analysis of PCR samples from cultures of various Listeria and non-Listeria organisms, the RNA probe was reactive in the assay of 62 different L. monocytogenes isolates but not other Listeria species. Among the non-Listeria organisms tested, only Enterococcus faecalis gave a weak positive reaction with more than 10(9) cells per ml. This reactivity disappeared at lower cell densities. This strategy for the synthesis and application of RNA probes should facilitate the analysis of PCR products in the detection of L. monocytogenes and possibly other food pathogens. Images PMID:8215354

  3. Chemical Probes Allow Structural Insight into the Condensation Reaction of Nonribosomal Peptide Synthetases.

    PubMed

    Bloudoff, Kristjan; Alonzo, Diego A; Schmeing, T Martin

    2016-03-17

    Nonribosomal peptide synthetases (NRPSs) synthesize a vast variety of small molecules, including antibiotics, antitumors, and immunosuppressants. The NRPS condensation (C) domain catalyzes amide bond formation, the central chemical step in nonribosomal peptide synthesis. The catalytic mechanism and substrate determinants of the reaction are under debate. We developed chemical probes to structurally study the NRPS condensation reaction. These substrate analogs become covalently tethered to a cysteine introduced near the active site, to mimic covalent substrate delivery by carrier domains. They are competent substrates in the condensation reaction and behave similarly to native substrates. Co-crystal structures show C domain-substrate interactions, and suggest that the catalytic histidine's principle role is to position the α-amino group for nucleophilic attack. Structural insight provided by these co-complexes also allowed us to alter the substrate specificity profile of the reaction with a single point mutation.

  4. Multifragment azimuthal correlation functions: Probes for reaction dynamics in collisions of intermediate energy heavy ions

    SciTech Connect

    Lacey, R.A.; Elmaani, A.; Lauret, J.; Li, T.; Bauer, W.; Craig, D.; Cronqvist, M.; Gualtieri, E.; Hannuschke, S.; Reposeur, T.; Vander Molen, A.; Westfall, G.D.; Wilson, W.K.; Winfield, J.S.; Yee, J.; Yennello, S.; Nadasen, A.; Tickle, R.S.; Norbeck, E. National Superconducting Cyclotron Laboratory Department of Physics, Michigan State University, East Lansing, Michigan 48824-1321 Department of Physics, University of Michigan at Dearborn, Dearborn, Michigan 48128 Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1120 Department of Physics, University of Iowa, Iowa City, Iowa 52242 )

    1993-03-01

    Multifragment azimuthal correlation functions have been measured as a function of beam energy and impact parameter for the Ar+Sc system ([ital E]/[ital A]=35 to 115 MeV). The observed azimuthal correlation functions---which do not require corrections for dispersion of the reaction plane---exhibit strong asymmetries which are dependent on impact parameter and beam energy. Rotational collective motion and flow seem to dominate the correlation functions at low beam energies. It is proposed that multifragment azimuthal correlation functions can provide a useful probe for intermediate energy heavy ion reaction dynamics.

  5. Surface reactions of iron - enriched smectites: adsorption and transformation of hydroxy fatty acids and phenolic acids

    NASA Astrophysics Data System (ADS)

    Polubesova, Tamara; Olshansky, Yaniv; Eldad, Shay; Chefetz, Benny

    2014-05-01

    Iron-enriched smectites play an important role in adsorption and transformation of soil organic components. Soil organo-clay complexes, and in particular humin contain hydroxy fatty acids, which are derived from plant biopolymer cutin. Phenolic acids belong to another major group of organic acids detected in soil. They participate in various soil processes, and are of concern due to their allelopathic activity. We studied the reactivity of iron-enriched smectites (Fe(III)-montmorillonite and nontronite) toward both groups of acids. We used fatty acids- 9(10),16-dihydroxypalmitic acid (diHPA), isolated from curtin, and 9,10,16-trihydroxypalmitic acid (triHPA); the following phenolic acids were used: ferulic, p-coumaric, syringic, and vanillic. Adsorption of both groups of acids was measured. The FTIR spectra of fatty acid-mineral complexes indicated inner-sphere complexation of fatty acids with iron-enriched smectites (versus outer-sphere complexation with Ca(II)-montmorillonite). The LC-MS results demonstrated enhanced esterification of fatty acids on the iron-enriched smectite surfaces (as compared to Ca(II)-montmorillonite). This study suggests that fatty acids can be esterified on the iron-enriched smectite surfaces, which results in the formation of stable organo-mineral complexes. These complexes may serve as a model for the study of natural soil organo-clay complexes and humin. The reaction of phenolic acids with Fe(III)-montmorillonite demonstrated their oxidative transformation by the mineral surfaces, which was affected by molecular structure of acids. The following order of their transformation was obtained: ferulic >syringic >p-coumaric >vanillic. The LC-MS analysis demonstrated the presence of dimers, trimers, and tetramers of ferulic acid on the surface of Fe(III)-montmorillonite. Oxidation and transformation of ferulic acid were more intense on the surface of Fe(III)-montmorillonite as compared to Fe(III) in solution due to stronger complexation on

  6. Adsorption of 4-picoline and piperidine to the hydrated SiO2 surface: probing the surface acidity with vibrational sum frequency generation spectroscopy.

    PubMed

    Liu, Dingfang; Ma, Gang; Allen, Heather C

    2005-04-01

    Vapor adsorption is an important process influencing the migration and the fate of many organic pollutants in the environment. In this study, vibrational sum frequency generation (SFG) spectroscopy was used to study the adsorption of two surface acidity probe molecules, 4-picoline (pKa = 5.94) and piperidine (pKa = 11.24), onto the amorphous SiO2 surface. The adsorption of 4-picoline onto the silica surface occurs by forming weak hydrogen bonds between the nitrogen atoms of 4-picoline molecules and the hydrogen atoms of surface silanol OH groups. Piperidine molecules are strongly chemisorbed onto the SiO2 surface through the protonation of piperidine molecules by surface silanol OH groups. The SFG results indicate that the surface acidity constant of silanol OH groups (pKa-(HOSi triple bond)) is in the range of 5.94-11.24 at the air/solid interface. Although this range of surface acidity constants is quite wide, it is possible to narrow it by choosing probe molecules with a smaller pKa range. Together with theoretical prediction methods, adsorption studies using vibrational SFG spectroscopy are capable of quantifying the surface acidity of mineral oxides by carefully choosing the acidity probe molecules.

  7. Probing the resonance potential in the F atom reaction with hydrogen deuteride with spectroscopic accuracy

    PubMed Central

    Ren, Zefeng; Che, Li; Qiu, Minghui; Wang, Xingan; Dong, Wenrui; Dai, Dongxu; Wang, Xiuyan; Yang, Xueming; Sun, Zhigang; Fu, Bina; Lee, Soo-Y.; Xu, Xin; Zhang, Dong H.

    2008-01-01

    Reaction resonances are transiently trapped quantum states along the reaction coordinate in the transition state region of a chemical reaction that could have profound effects on the dynamics of the reaction. Obtaining an accurate reaction potential that holds these reaction resonance states and eventually modeling quantitatively the reaction resonance dynamics is still a great challenge. Up to now, the only viable way to obtain a resonance potential is through high-level ab initio calculations. Through highly accurate crossed-beam reactive scattering studies on isotope-substituted reactions, the accuracy of the resonance potential could be rigorously tested. Here we report a combined experimental and theoretical study on the resonance-mediated F + HD → HF + D reaction at the full quantum state resolved level, to probe the resonance potential in this benchmark system. The experimental result shows that isotope substitution has a dramatic effect on the resonance picture of this important system. Theoretical analyses suggest that the full-dimensional FH2 ground potential surface, which was believed to be accurate in describing the resonance picture of the F + H2 reaction, is found to be insufficiently accurate in predicting quantitatively the resonance picture for the F + HD → HF + D reaction. We constructed a global potential energy surface by using the CCSD(T) method that could predict the correct resonance peak positions as well as the dynamics for both F + H2 → HF + H and F + HD → HF + D, providing an accurate resonance potential for this benchmark system with spectroscopic accuracy. PMID:18687888

  8. Nonlinear optical property of hemicyanine self-assembled monolayers on gold and its adsorption kinetics probed by optical second-harmonic generation and surface plasmon resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Naraoka, Ryo; Kaise, Go; Kajikawa, Kotaro; Okawa, Haruki; Ikezawa, Hiroki; Hashimoto, Kazuhiko

    2002-08-01

    We have prepared the organosulfur self-assembled monolayer (SAM) containing hemicyanine on gold. It shows a large second-order nonlinear optical susceptibility χzzz=58 pm/V. The adsorption kinetics of the SAM on gold was also probed by the in situ real time measurements of second-harmonic generation (SHG) and surface plasmon resonance (SPR) spectroscopy. While the SHG kinetics was saturated immediately after the immersion of the gold substrate in the solution, the SPR kinetics showed additional slow adsorption for more than 20 000 s. This means that rapid formation of the well-ordered hemicyanine SAM is followed by gradual physisorption where the molecules are disordered.

  9. Low energy electron induced reactions in fluorinated acetamide - probing negative ions and neutral stable counterparts*

    NASA Astrophysics Data System (ADS)

    Kopyra, Janina; König-Lehmann, Constanze; Illenberger, Eugen; Warneke, Jonas; Swiderek, Petra

    2016-06-01

    Electron impact to trifluoroacetamide (CF3CONH2, TFAA) in the energy range 0-12 eV leads to a variety of negative fragment ions which are formed via dissociative electron attachment (DEA). The underlying reactions range from single bond cleavages to remarkably complex reactions that lead to loss of the neutral units HF, H2O and HNCO as deduced from their directly observed ionic counterparts (M - H2O)-, (M - HF)- and (M - HNCO)-. Also formed are the pseudo-halogen ions CN- and OCN-. All these reactions proceed dominantly via a resonance located near 1 eV, i.e., electrons at subexcitation energies trigger reactions involving multiple bond cleavages. The electron induced generation of the neutral molecules HF, H2O and HNCO in condensed TFAA films is probed by temperature controlled thermal desorption spectrometry (TDS) which can be viewed as a complementary techniques to gas-phase experiments in DEA to directly probe the neutral counterparts. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  10. Bordetella pertussis detection by spectrofluorometry using polymerase chain reaction (PCR) and a molecular beacon probe.

    PubMed

    Poddar, S K; Le, C T

    2001-06-01

    Bordetella pertussis was detected by spectrofluorometry following PCR incorporating a molecular beacon probe in the reaction. A DNA fragment from the tandem repeat sequence region (IS 481) of the genome of B. pertussis was amplified in presence of the probe complementary to an internal segment of the amplified DNA fragment. Fluorescein (FAM) and DABCYL were used as the fluorophore and quencher in the probe. The probe was characterized for its signal to noise ratio by homogeneous solution hybridization with a complementary oligonucleotide. Measurement of fluorescent signal at the emission maxima of FAM, immediately after a PCR was used to detect the B. pertussis target, with no additional steps. Presence of B. pertussis in a sample was also examined by agarose gel electrophoresis of the PCR product. A serial diluted stock of B. pertussis (ATCC strain #9797) and fourteen clinical isolates of B. pertussis were examined. The sensitivity of detection by fluorescent measurement was found to be at least in the range of 0.01-0.1 CFU per 10 microl of the sample and was equal to or better than that detected by agarose gel analysis.

  11. Molecular probes and the polymerase chain reaction for detection and typing of Leishmania species in Mexico.

    PubMed

    Monroy-Ostria, Amalia; Sanchez-Tejeda, Gustavo

    2002-04-01

    Leishmaniasis in Mexico is a public health problem because all the clinical forms have been recorded in most Mexican states. We studied patients showing clinical symptoms of any form of leishmaniasis, from several endemic areas. Bone marrow samples, aspirates or skin biopsies were taken and deoxyribonucleic acid (DNA) was extracted and amplified by the polymerase chain reaction (PCR) with universal primers AJS1 and DeB8, specific for the Leishmania subgenus Leishmania. The PCR products were then hybridized by dot- or Southern blotting and probed with probe 9.2, specific for the L. mexicana complex. If hybridization did not occur, the DNA was amplified with primers D1 and D2, specific for members of the L. donovani complex, and PCR products were hybridized with probe B4Rsa, also specific for the L. donovani complex. DNA was also amplified with primers B1 and B2, specific for the subgenus Viannia, and the PCR products were hybridized with probe B18, specific for the L. braziliensis complex. It was found that in Tabasco and Veracruz, Mexico, localized cutaneous leishmaniasis (LCL) is caused by infection with members of the L. mexicana complex, whereas in the states of Nayarit and Campeche it was due to infection with the L. mexicana and/or L. braziliensis complexes. Visceral leishmaniasis was caused by L. (L.) chagasi, mainly in the states of Chiapas and Guerrero, and by L. (L.) mexicana in one immunocompromised patient from Tabasco.

  12. Picosecond infrared spectroscopy as probe for photochemical or thermal reactions in solid matrices

    SciTech Connect

    Lippert, T.; Funk, D.J.; Strauss, C.E.M.; Stoutland, P.O.

    1998-08-01

    Spectroscopy in the mid-IR on timescales from pico to milliseconds has been developed for the study of laser-material interactions over broad timescales. To reach these timescales the authors have employed two configurations: (1) for the ps to ns timescale a one and a two stage difference frequency mixing setup is employed, (2) for the longer timescale, CW mid-IR laser diodes have been used. In general, they excite the sample with one pulse at 1064/266/355 nm and probe some time later in the mid IR (2900--800 cm{sup {minus}1}). In the case of photochemical reaction, they excite the sample directly in the UV. Alternatively, they initiate thermal reactions by pumping a heater dye at 1.064 {micro}m, which quickly converts the photon energy into heat. The potential of this technique to study reactions in the solid state was demonstrated for a photochemically induced (266 nm) reaction (Wolff rearrangement of a {alpha}-diazo-ketone to {alpha}-keto-ketene) in a polymer matrix. Thermal initiation resulted in a similar reaction. The position, amplitude and width of the product bands changed, they believe due to additional side reactions and temperature effects.

  13. Reaction-based fluorescent probes for selective imaging of hydrogen sulfide in living cells.

    PubMed

    Lippert, Alexander R; New, Elizabeth J; Chang, Christopher J

    2011-07-01

    Hydrogen sulfide (H(2)S) is emerging as an important mediator of human physiology and pathology but remains difficult to study, in large part because of the lack of methods for selective monitoring of this small signaling molecule in live biological specimens. We now report a pair of new reaction-based fluorescent probes for selective imaging of H(2)S in living cells that exploit the H(2)S-mediated reduction of azides to fluorescent amines. Sulfidefluor-1 (SF1) and Sulfidefluor-2 (SF2) respond to H(2)S by a turn-on fluorescence signal enhancement and display high selectivity for H(2)S over other biologically relevant reactive sulfur, oxygen, and nitrogen species. In addition, SF1 and SF2 can be used to detect H(2)S in both water and live cells, providing a potentially powerful approach for probing H(2)S chemistry in biological systems.

  14. Changes in Practice Schedule and Functional Task Difficulty: a Study Using the Probe Reaction Time Technique

    PubMed Central

    Akizuki, Kazunori; Ohashi, Yukari

    2013-01-01

    [Purpose] Motor learning is accelerated most by optimized task difficulty. When task difficulty is optimized, the amount of information required to complete the task matches the learner's information processing abilities. The practice schedule is one of the factors which changes the amount of task information. We investigated the influence of changes in practice schedule on the amount of task information using the probe reaction time technique. [Methods] Fourteen young male subjects were randomly assigned to a blocked or random practice group. They were required to perform two tasks simultaneously. The primary task consisted of treadmill walking with specific step lengths, and the secondary task consisted of a probe reaction time task. [Results] The blocked practice group was superior to the random practice group in performance during the acquisition phase. In contrast, the random practice group was superior to the blocked practice group in performance during the retention phase. Furthermore, the random practice group had a longer reaction time than the blocked practice group. [Conclusion] From the standpoint of the challenge point framework, motor learning may be accelerated by random practice because random practice probably elicits greater attentional demand than blocked practice. PMID:24259863

  15. A sensitive DNA biosensor based on a facile sulfamide coupling reaction for capture probe immobilization.

    PubMed

    Wang, Qingxiang; Ding, Yingtao; Gao, Feng; Jiang, Shulian; Zhang, Bin; Ni, Jiancong; Gao, Fei

    2013-07-25

    A novel DNA biosensor was fabricated through a facile sulfamide coupling reaction. First, the versatile sulfonic dye molecule of 1-amino-2-naphthol-4-sulfonate (AN-SO3(-)) was electrodeposited on the surface of a glassy carbon electrode (GCE) to form a steady and ordered AN-SO3(-) layer. Then the amino-terminated capture probe was covalently grafted to the surface of SO3(-)-AN deposited GCE through the sulfamide coupling reaction between the amino groups in the probe DNA and the sulfonic groups in the AN-SO3(-). The step-by-step modification process was characterized by electrochemistry and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Using Ru(NH3)6(3+) as probe, the probe density and the hybridization efficiency of the biosensor were determined to be 3.18×10(13) strands cm(-2) and 86.5%, respectively. The hybridization performance of the biosensor was examined by differential pulse voltammetry using Co(phen)3(3+/2+) (phen=1,10-phenanthroline) as the indicator. The selectivity experiments showed that the biosensor presented distinguishable response after hybridization with the three-base mismatched, non-complementary and complementary sequences. Under the optimal conditions, the oxidation peak currents of Co(phen)3(3+/2+) increased linearly with the logarithm values of the concentration of the complementary sequences in the range from 1.0×10(-13)M to 1.0×10(-8)M with a regression coefficient of 0.9961. The detection limit was estimated to be 7.2×10(-14)M based on 3σ. PMID:23845495

  16. The influence of the ``hot''-dimer adsorption mechanism on the kinetics of a monomer-dimer surface reaction

    NASA Astrophysics Data System (ADS)

    Pereyra, V. D.; Albano, E. V.

    1993-09-01

    “Hot” dimers are molecules which after adsorption dissociate and each of the remaining “hot” monomers fly apart up to a maximum distance R from the original adsorption site. The influence of the “hot”-dimer adsorption mechanism on relevant aspects of the bimolecular catalyzed reaction of the type A - (1/2) B 2(“hot”) → AB is studied by means of the Monte-Carlo simulation technique. The temporal evolution of both the reactant's coverages as well as the rate of AB-production is evaluated and discussed. Due to the enhanced probability of “hot” species for encounters with other adsorbed particles, the rate of AB-production becomes faster when increasing R. This behavior may be relevant in the dynamic of some catalyzed reactions such as for example the oxidation of carbon monoxide on transition metal surfaces, i.e. A≡CO, B 2≡O2, and AB≡CO2. Also the sticking coefficient of “hot” dimers and the average distance traveled by the “hot” monomers are evaluated and discussed.

  17. Effect of Fluorescently Labeling Protein Probes on Kinetics of Protein-Ligand Reactions

    PubMed Central

    Sun, Y.S.; Landry, J.P.; Fei, Y.Y.; Luo, J.T.; Wang, X.B.; Lam, K.S.

    2009-01-01

    We studied the effect of fluorescently labeling proteins on protein-ligand reactions. Un-labeled ligands (streptavidin-binding peptides and rabbit immunoglobulin G (IgG) as antigen targets) are immobilized on epoxy-functionalized glass slides. Unlabeled and Cy3-labeled protein probes from the same batch (streptavidin and goat antibodies) subsequently react with the surface-immobilized targets. By monitoring in situ the surface mass density change using an oblique-incidence reflectivity difference scanning microscope (a label-free detector), we measured kon and koff for streptavidin-peptide reactions and antibody-antigen reaction. We found that (1) equilibrium dissociation constants, defined as KD = koff/kon, for streptavidin-peptide reactions increases by a factor of 3 ~ 4 when the solution-phase streptavidin is labeled with Cy3 dye; and (2) KD for reactions of solution-phase goat anti-rabbit antibodies with rabbit IgG targets also change significantly when the goat antibodies are labeled with Cy3 dye. PMID:18991423

  18. Effect of fluorescently labeling protein probes on kinetics of protein-ligand reactions.

    PubMed

    Sun, Y S; Landry, J P; Fei, Y Y; Zhu, X D; Luo, J T; Wang, X B; Lam, K S

    2008-12-01

    We studied the effect of fluorescently labeling proteins on protein-ligand reactions. Unlabeled ligands (streptavidin-binding peptides and rabbit immunoglobulin G (IgG) as antigen targets) are immobilized on epoxy-functionalized glass slides. Unlabeled and Cy3-labeled protein probes from the same batch (streptavidin and goat antibodies) subsequently react with the surface-immobilized targets. By monitoring in situ the surface mass density change using an oblique-incidence reflectivity difference scanning microscope (a label-free detector), we measured k(on) and k(off) for streptavidin-peptide reactions and antibody-antigen reaction. We found that (1) equilibrium dissociation constants, defined as K(D) = k(off)/k(on), for streptavidin-peptide reactions increases by a factor of 3-4 when the solution-phase streptavidin is labeled with Cy3 dye and (2) K(D) for reactions of solution-phase goat anti-rabbit antibodies with rabbit IgG targets also change significantly when the goat antibodies are labeled with Cy3 dye. PMID:18991423

  19. Single-particle states in ^112Cd probed with the ^111Cd(d,p) reaction

    NASA Astrophysics Data System (ADS)

    Garrett, P. E.; Jamieson, D.; Demand, G. A.; Finlay, P.; Green, K. L.; Leach, K. G.; Phillips, A. A.; Sumithrarachchi, C. S.; Svensson, C. E.; Triambak, S.; Wong, J.; Ball, G. C.; Hertenberger, R.; Wirth, H.-F.; Kr"Ucken, R.; Faestermann, T.

    2009-10-01

    As part of a program of detailed spectroscopy of the Cd isotopes, the single-particle neutron states in ^112Cd have been probed with the ^111Cd(d,p) reaction. Beams of polarized 22 MeV deuterons, obtained from the LMU/TUM Tandem Accelerator, bombarded a target of ^111Cd. The protons from the reaction, corresponding to excitation energies up to 3 MeV in ^112Cd, were momentum analyzed with the Q3D spectrograph. Cross sections and analyzing powers were fit to results of DWBA calculations, and spectroscopic factors were determined. The results from the experiment, and implications for the structure of ^112Cd, will be presented.

  20. Adsorption and reaction of trace gas-phase organic compounds on atmospheric water film surfaces: a critical review.

    PubMed

    Donaldson, D J; Valsaraj, Kalliat T

    2010-02-01

    The air-water interface in atmospheric water films of aerosols and hydrometeors (fog, mist, ice, rain, and snow) presents an important surface for the adsorption and reaction of many organic trace gases and gaseous reactive oxidants (hydroxyl radical (OH(.)), ozone (O(3)), singlet oxygen (O(2)((1)Delta(g))), nitrate radicals (NO(3)(.)), and peroxy radicals (RO(2)(.)). Knowledge of the air-water interface partition constant of hydrophobic organic species is necessary for elucidating the significance of the interface in atmospheric fate and transport. Various methods of assessing both experimental and theoretical values of the thermodynamic partition constant and adsorption isotherm are described in this review. Further, the reactivity of trace gases with gas-phase oxidants (ozone and singlet oxygen) at the interface is summarized. Oxidation products are likely to be more water-soluble and precursors for secondary organic aerosols in hydrometeors. Estimation of characteristic times shows that heterogeneous photooxidation in water films can compete effectively with homogeneous gas-phase reactions for molecules in the atmosphere. This provides further support to the existing thesis that reactions of organic compounds at the air-water interface should be considered in gas-phase tropospheric chemistry.

  1. In situ temperature measurements of reaction spaces under microwave irradiation using photoluminescent probes.

    PubMed

    Ano, Taishi; Kishimoto, Fuminao; Sasaki, Ryo; Tsubaki, Shuntaro; Maitani, Masato M; Suzuki, Eiichi; Wada, Yuji

    2016-05-11

    We demonstrate two novel methods for the measurement of the temperatures of reaction spaces locally heated by microwaves, which have been applied here to two example systems, i.e., BaTiO3 particles covered with a SiO2 shell (BaTiO3-SiO2) and layered tungstate particles. Photoluminescent (PL) probes showing the temperature-sensitivity in their PL lifetimes are located in the nanospaces of the above systems. In the case of BaTiO3-SiO2 core-shell particles, rhodamine B is loaded into the mesopores of the SiO2 shell covering the BaTiO3 core, which generates the heat through the dielectric loss of microwaves. The inner nanospace temperature of the SiO2 shell is determined to be 28 °C higher than the bulk temperature under microwave irradiation at 24 W. On the other hand, Eu(3+) is immobilized in the interlayer space of layered tungstate as the PL probe, showing that the nanospace temperature of the interlayer is only 4 °C higher than the bulk temperature. This method for temperature-measurement is powerful for controlling microwave heating and elucidates the ambiguous mechanisms of microwave special effects often observed in chemical reactions, contributing greatly to the practical application of microwaves in chemistry and materials sciences. PMID:27136754

  2. Adsorption and reaction of sulfur dioxide on alumina and sodium-impregnated alumina

    SciTech Connect

    Mitchell, M.B.; Sheinker, V.N.; White, M.G.

    1996-05-02

    The adsorption and oxidation of SO{sub 2} on alumina and sodium-impregnated alumina has been examined using thermogravimetric analysis and diffuse reflectance infrared Fourier transform spectroscopy. Sulfur dioxide chemisorbs initially at basic sites to form an adsorbed sulfite, which is quantitatively converted to sulfate on oxidation. It has been observed that at low coverages, nearly 2.6 {mu}mol/m{sup 2}, sodium acts as a promoter for the formation of an adsorbed sulfite and sulfate which have structures similar to those of aluminum sulfite and sulfate, respectively. At higher sodium loadings, a second type of adsorbed SO{sub 2} is formed, similar to sodium sulfite and sulfate. The species with the aluminum sulfate structure appears to be more easily decomposed than does the sodium sulfate species and accounts for the regenerable adsorption capacity. Formation of the sodium sulfate species appears to account for the loss of adsorption capacity as the number of adsorption/regeneration cycles increases. Oxidation of the sulfite form to the sulfate form can occur in the absence of added oxygen, but it is an activated process and begins to occur in measurable amounts at temperatures between 150 and 300{degree}C. Partitioning of adsorbed SO{sub 2} between aluminum and sodium forms is not a function of temperature and depends on only sodium loading. 32 refs., 14 figs., 1 tab.

  3. The adsorption, reaction and decomposition of propylene on a clean Mo(100) surface

    NASA Astrophysics Data System (ADS)

    Wang, Luping; Tysoe, W. T.

    1991-04-01

    Propylene adsorbs onto Mo(100) at 110 K via precursor-state kinetics to saturate at a coverage, θ sat(C 3H 6) = 0.63 ± 0.05. Adsorption at lower temperatures results in multilayer adsorption. In contrast to ethylene, which rehybridizes to ~ sp 3 following adsorption at 80 K on Mo(100), propylene adsorbs molecularly at this temperature, rehybridizing only after heating to between 100 and 140 K. Further heating to between 180 and 200 K results in loss of hydrogen from the surface propylenic species and the formation of an aliene- or methylacetylene-like adsorbate which appears to be oriented so that the C-C-C axis is essentially parallel to the surface. Photoelectron spectroscopic data suggests significant carbon-carbon bond cleavage in the adsorbed C 3 species is underway by ~ 270 K. on Mo(100), resulting finally in the formation of adsorbed CH x species on heating the Mo(100) surface to room temperature. This chemistry is closely analogous to that observed following ethylene adsorption onto Mo(100) where a similar carbon-carbon bond cleavage was noted, and is in accord with the catalytic chemistry of molybdenum which catalyzes both olefin metathesis and hydrogenolysis. Further heating to above 400 K completely dehydrogenates the surface leaving chemisorbed, atomic carbon.

  4. Probing Photochemically and Thermally Induced Isomerization Reactions in α-Pyrone.

    PubMed

    Murdock, Daniel; Clark, Ian P; Ashfold, Michael N R

    2016-09-22

    The isomerization dynamics of α-pyrone dissolved in CH3CN have been probed by femtosecond 267 nm pump/broadband infrared (IR) probe spectroscopy. A novel experimental setup allowed the populations of the parent molecule and ring-opened photoproducts to be monitored over pump/probe time delays ranging between 2 ps and 100 μs within a single experiment, and at 5 different temperatures between 0 and 40 °C. The photochemically prepared α-pyrone(S1) molecules decay rapidly (<10 ps) through internal conversion to the S0 potential energy surface, with an initial quantum yield for parent molecule re-formation of ∼60%. Probing the antisymmetric ketene stretch region (2100-2150 cm(-1)) confirms the presence of at least two ring-opened photoproducts, which are assumed to have an E-configuration with respect to the central C═C double bond. These ketenes are observed to undergo two distinct, thermally driven, isomerization processes which occur on the nanosecond and microsecond time scales, respectively. The former reaction is ascribed to thermalization of the initially prepared E-isomer populations, while the slower (microsecond) process involves rotation around the central C═C double bond leading to formation of Z-isomers. Subsequent rapid Z → Z isomerizations (occurring on a nanosecond time scale) result in ring-closure and a second, longer time recovery of parent molecule population. By determining rates as a function of the sample temperature, barrier heights of 0.23(3) eV and 0.43(2) eV are obtained for the E → E and E → Z transformations, respectively. PMID:27584030

  5. Ratiometric fluorescent probe for rapid detection of bisulfite through 1,4-addition reaction in aqueous solution.

    PubMed

    Sun, Yue; Zhao, Dong; Fan, Shanwei; Duan, Lian; Li, Ruifeng

    2014-04-16

    A ratiometric fluorescent probe based on a positively charged benzo[e]indolium moiety for bisulfite is reported. The bisulfite underwent a 1,4-addition reaction with the C-4 atom in the ethylene group. This reaction resulted in a large emission wavelength shift (Δλ = 106 nm) and an observable fluorescent color change from orange to cyan. The reaction could be completed in 90 s in a PBS buffer solution and displayed high selectivity and sensitivity for bisulfite. A simple paper test strip system was developed to detect bisulfite rapidly. Probe 1 was used to detect bisulfite in real samples with good recovery.

  6. [Influence of reaction time of urea hydrolysis-based co-precipitation on the structure of ZnAl layered double hydroxides and the phosphate adsorption].

    PubMed

    Lu, Ying; Cheng, Xiang; Xing, Bo; Sun, Zhong-en; Sun, De-zhi

    2012-08-01

    A series of ZnAl layered double hydroxides (LDHs) were prepared by urea hydrolysis-based homogeneous co-precipitation for studying their structure and phosphate adsorption capacities. The results show that all the samples exhibited a typical layered structure as the reaction time extended from 12 h to 96 h, whereas Zn/Al molar ratio in the ZnAls decreased from 2.06 to 0.70 and the specific surface area markedly increased to be 7.6-fold higher than that of ZnAl-12. Phosphate adsorption capacity of the ZnAl was in general increased gradually with the reaction time extension, which can be attributed to the surface area rising as well as the increased positive charge of LDHs layer caused by a higher proportion of Al. This reveals that physicochemical adsorption on LDHs surface would have played an important role during the phosphate adsorption. With a reaction time of 24 h, a high amount of exchangeable interlayer anions was observed, giving rise to a highest phosphate uptake of 34.1 mg x g(-1) by the ZnAl-24. It indicates the ion exchange was another major pathway for the phosphate removal. For all the ZnAls with different reaction times, the phosphate adsorption isotherms fit well with Langmuir-type equations; the adsorption kinetics followed pseudo-second-order models.

  7. Unravelling RNA-substrate interactions in a ribozyme-catalysed reaction using fluorescent turn-on probes.

    PubMed

    Gaffarogullari, Ece Cazibe; Greulich, Peter; Kobitski, Andrei Yu; Nierth, Alexander; Nienhaus, G Ulrich; Jäschke, Andres

    2015-04-01

    The Diels-Alder reaction is one of the most important C-C bond-forming reactions in organic chemistry, and much effort has been devoted to controlling its enantio- and diastereoselectivity. The Diels-Alderase ribozyme (DAse) catalyses the reaction between anthracene dienes and maleimide dienophiles with multiple-turnover, stereoselectivity, and up to 1100-fold rate acceleration. Here, a new generation of anthracene-BODIPY-based fluorescent probes was developed to monitor catalysis by the DAse. The brightness of these probes increases up to 93-fold upon reaction with N-pentylmaleimide (NPM), making these useful tools for investigating the stereochemistry of the ribozyme-catalysed reaction. With these probes, we observed that the DAse catalyses the reaction with >91% de and >99% ee. The stereochemistry of the major product was determined unambiguously by rotating-frame nuclear Overhauser NMR spectroscopy (ROESY-NMR) and is in agreement with crystallographic structure information. The pronounced fluorescence change of the probes furthermore allowed a complete kinetic analysis, which revealed an ordered bi uni type reaction mechanism, with the dienophile binding first.

  8. Adsorption and Reaction of Acetaldehyde on Stoichiometric and Defective SrTiO{sub 3}(100) Surfaces

    SciTech Connect

    Wang, Li Q.; Ferris, Kim F.; Azad, Samina; Engelhard, Mark H.; Peden, Charles HF.

    2004-02-05

    The adsorption and reaction of acetaldehyde (CH{sub 3}CHO), on stoichiometric (TiO{sub 2}-terminated) and reduced SrTiO{sub 3}(100) surfaces, have been investigated using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Acetaldehyde adsorbs molecularly on the stoichiometric SrTiO{sub 3}(100) surface that contains predominantly Ti{sup 4+} cations. The Ti{sup 4+} sites on the stoichiometric SrTiO{sub 3}(100) surface are not sufficiently active for surface reactions such as aldol condensation, as opposed to the Ti{sup 4+} ions on the TiO{sub 2}(001) surface. However, decomposition and redox reactions of acetaldehyde occur in the presence of surface defects created by Ar{sup +} sputtering. The decomposition products following reactions of acetaldehyde on the defective surface include H{sub 2}, C{sub 2}H{sub 4}, CO, C{sub 4}H{sub 6} and C{sub 4}H{sub 8}. Reductive coupling, to produce C{sub 2}H{sub 4} and C{sub 4}H{sub 8}, is the main reaction pathway for decomposition of acetaldehyde on the sputter reduced SrTiO{sub 3}(100) surface.

  9. Adsorptive capacity and evolution of the pore structure of alumina on reaction with gaseous hydrogen fluoride.

    PubMed

    McIntosh, Grant J; Agbenyegah, Gordon E K; Hyland, Margaret M; Metson, James B

    2015-05-19

    Brunauer-Emmet-Teller (BET) specific surface areas are generally used to gauge the propensity of uptake on adsorbents, with less attention paid to kinetic considerations. We explore the importance of such parameters by modeling the pore size distributions of smelter grade aluminas following HF adsorption, an industrially important process in gas cleaning at aluminum smelters. The pore size distributions of industrially fluorinated aluminas, and those contacted with HF in controlled laboratory trials, are reconstructed from the pore structure of the untreated materials when filtered through different models of adsorption. These studies demonstrate the presence of three distinct families of pores: those with uninhibited HF uptake, kinetically limited porosity, and pores that are surface blocked after negligible scrubbing. The surface areas of the inaccessible and blocked pores will overinflate estimates of the adsorption capacity of the adsorbate. We also demonstrate, contrary to conventional understanding, that porosity changes are attributed not to monolayer uptake but more reasonably to pore length attenuation. The model assumes nothing specific regarding the Al2O3-HF system and is therefore likely general to adsorbate/adsorbent phenomena.

  10. Photosynthetic oxygen evolution in mesoporous silica material: adsorption of photosystem II reaction center complex into 23 nm nanopores in SBA.

    PubMed

    Noji, Tomoyasu; Kamidaki, Chihiro; Kawakami, Keisuke; Shen, Jian-Ren; Kajino, Tsutomu; Fukushima, Yoshiaki; Sekitoh, Takeshi; Itoh, Shigeru

    2011-01-18

    An oxygen-evolving photosynthetic reaction center complex (PSII) was adsorbed into nanopores in SBA, a mesoporous silica compound. We purified the dimer of PSII complex from a thermophilic cyanobacterium, Thermosynechococcus vulcanus, which grows optimally at 57 °C. The thermally stable PSII dimeric complex has a diameter of 20 nm and a molecular mass of 756 kDa and binds more than 60 chlorophylls. The SBA particles, with average internal pore diameters of 15 nm (SBA(15)) and 23 nm (SBA(23)), adsorbed 4.7 and 15 mg of PSII/g SBA, respectively. Measurement with a confocal laser-scanning microscope indicated the adsorption of PSII to the surface and the inner space of the SBA(23) particles, indicating the adsorption of PSII into the 23 nm silica nanopores. PSII did not bind to the inner pores of SBA(15). PSII bound to SBA(23) showed the high and stable activity of a photosynthetic oxygen-evolving reaction, indicating the light-driven electron transport from water to the quinone molecules added in the outer medium. The PSII-SBA conjugate can be a new material for photosensors and artificial photosynthetic systems.

  11. Three model space experiments on chemical reactions. [Gibbs adsorption, equilibrium shift and electrodeposition

    NASA Technical Reports Server (NTRS)

    Grodzka, P.; Facemire, B.

    1977-01-01

    Three investigations conducted aboard Skylab IV and Apollo-Soyuz involved phenomena that are of interest to the biochemistry community. The formaldehyde clock reaction and the equilibrium shift reaction experiments conducted aboard Apollo Soyuz demonstrate the effect of low-g foams or air/liquid dispersions on reaction rate and chemical equilibrium. The electrodeposition reaction experiment conducted aboard Skylab IV demonstrate the effect of a low-g environment on an electrochemical displacement reaction. The implications of the three space experiments for various applications are considered.

  12. Probing Surface Sites of TiO2: Reactions with [HRe(CO)5] and [CH3Re(CO)5

    SciTech Connect

    Lobo-Lapidus, R.; Gates, B

    2010-01-01

    Two carbonyl complexes of rhenium, [HRe(CO){sub 5}] and [CH{sub 3}Re(CO){sub 5}], were used to probe surface sites of TiO{sub 2} (anatase). These complexes were adsorbed from the gas phase onto anatase powder that had been treated in flowing O{sub 2} or under vacuum to vary the density of surface OH sites. Infrared (IR) spectra demonstrate the variation in the number of sites, including Ti{sup +3} {double_bond} OH and Ti{sup +4} {double_bond} OH. IR and extended X-ray absorption fine structure (EXAFS) spectra show that chemisorption of the rhenium complexes led to their decarbonylation, with formation of surface-bound rhenium tricarbonyls, when [HRe(CO){sub 5}] was adsorbed, or rhenium tetracarbonyls, when [CH{sub 3}Re(CO){sub 5}] was adsorbed. These reactions were accompanied by the formation of water and surface carbonates and removal of terminal hydroxyl groups associated with Ti{sup +3} and Ti{sup +4} ions on the anatase. Data characterizing the samples after adsorption of [HRe(CO){sub 5}] or [CH{sub 3}Re(CO){sub 5}] determined a ranking of the reactivity of the surface OH sites, with the Ti{sup +3}OH groups being the more reactive towards the rhenium complexes but the less likely to be dehydroxylated. The two rhenium pentacarbonyl probes provided complementary information, suggesting that the carbonate species originate from carbonyl ligands initially bonded to the rhenium and from hydroxyl groups of the titania surface, with the reaction leading to the formation of water and bridging hydroxyl groups on the titania. The results illustrate the value of using a family of organometallic complexes as probes of oxide surface sites.

  13. Synthesis of a non-radioactive hepatitis B virus DNA probe from human serum by the polymerase chain reaction.

    PubMed

    Rodríguez-Frías, F; Arranz, J A; Buti, M; Esteban, R; Jardí, R

    1994-05-01

    A method for synthesizing probes for detecting hepatitis B virus DNA in serum was developed. It uses DNA extracted from the serum of an hepatitis B virus carrier as target, and digoxigenin-11-dUTP incorporated in DNA sequences during the polymerase chain reaction as tracer. Using a spot hybridization assay, the sensitivity and specificity of the digoxigenin-labelled DNA probe were compared with two standard hepatitis B virus DNA probes, synthesized with cloned hepatitis B virus DNA and labelled either with digoxigenin or 32P by random priming. Data obtained from the three methods showed an excellent correlation. Thus, hepatitis B virus DNA extracted from human serum and labelled by polymerase chain reaction may be considered a suitable alternative to cloned DNA. It provides reliable probes and eliminates the need for facilities and personnel dedicated to the manipulation of clones. These advantages will allow a wider application of hepatitis B virus DNA testing in clinical practice.

  14. Isotope Effects as Probes for Enzyme Catalyzed Hydrogen-Transfer Reactions

    PubMed Central

    Roston, Daniel; Islam, Zahidul; Kohen, Amnon

    2015-01-01

    Kinetic Isotope effects (KIEs) have long served as a probe for the mechanisms of both enzymatic and solution reactions. Here, we discuss various models for the physical sources of KIEs, how experimentalists can use those models to interpret their data, and how the focus of traditional models has grown to a model that includes motion of the enzyme and quantum mechanical nuclear tunneling. We then present two case studies of enzymes, thymidylate synthase and alcohol dehydrogenase, and discuss how KIEs have shed light on the C-H bond cleavages those enzymes catalyze. We will show how the combination of both experimental and computational studieshas changed our notion of how these enzymes exert their catalytic powers. PMID:23673528

  15. ZnS quantum dots as pH probes for study of enzyme reaction kinetics.

    PubMed

    Wu, Dudu; Chen, Zhi

    2012-06-10

    Water soluble ZnS quantum dots (QDs) modified by mercaptoacetic acid (MAA) were used to determinate proton concentration in aqueous solutions by fluorescence spectroscopic technique. The results showed that the fluorescence of the water-soluble QDs could be quenched by proton concentration and the fluorescence intensity of the water-soluble QDs decreased linearly as the pH varied from 4.5 to 7.0. Based on this phenomenon, a convenient, rapid and specific method to determine of enzyme reaction kinetics was proposed. The modified ZnS QDs were successfully used as pH probes in monitoring the hydrolysis of glycidyl butyrate catalyzed by porcine pancreatic lipase (PPL). The proposed method was found to improve stability, sensitivity and a monitoring range for determination proton concentration as compared to the already described analytical methods based on p-Nitrophenoxide (PNP).

  16. Polymerase chain reaction as a tool for developing stress protein probes

    SciTech Connect

    Cochrane, B.J.; Mattley, Y.D. . Dept. of Biology); Snell, T.W. . Div. of Biology)

    1994-08-01

    Because of the high degree of evolutionary conservation of stress proteins, potential exists for the development of nucleic acid probes from particular species that could be used to monitor stress-related changes in mRNA abundance. The polymerase chain reaction (PCR) is a powerful tool that can be applied to the generation of these probes, provided that primer sequences can be identified that specifically amplify sequences of interest from a wide variety of organisms. The authors identified such sequences from multiple alignments of published chaperonin and stress-70 sequences, and tested their ability to amplify appropriately sized fragments from genomic DNA from a variety of vertebrates and invertebrates. Although no primer pair could be used successfully with all species, the authors were able to derive specific products from most species by testing different pairs. One primer pair for chaperonin proved particularly useful. Products were obtained from all tested species, and with a single exception (human), these primers appeared to amplify a single copy sequence. The authors determined the nucleotide sequence of the product obtained from the rotifer Brachionus plicatilis and determined by phylogenetic analysis of the inferred protein product that the product obtained is most likely derived from a rotifer DNA template. Finally, the authors show that this product can be used to detect changes in abundance of homologous mRNA in heat-stressed rotifers.

  17. Probing the adsorption of weak acids on graphite using amplitude modulation-frequency modulation atomic force microscopy.

    PubMed

    Moustafa, Ahmed M A; Huang, Jun; McPhedran, Kerry N; Zeng, Hongbo; El-Din, Mohamed Gamal

    2015-03-17

    Recent thermodynamics calculations and adsorption isotherms showed that the adsorption of a self-assembled layer (SAL) of ionized weak acids to carbon was attributed to the negatively charged hydrogen bonding (-CAHB), yet the direct visualization and characterization of this adsorption behavior have not been reported. Here, an amplitude modulation-frequency modulation atomic force microscopy (AM-FM AFM) technique was applied to discriminate the adsorption of decanoic acids (DA) on highly ordered pyrolytic graphite (HOPG). Thermodynamics calculations revealed that the adsorption of SAL was driven by the formation of -CAHB with negatively charged functional groups of HOPG. Multilayer adsorption could occur over the adsorbed ionized SAL, leading to the development of aggregates. AM-FM AFM imaging showed that the adsorption of the DA molecules forming aggregates occurred only for the HOPG-functionalized steps, while DA molecules were found to adsorb over the entire functionalized HOPG surface after water-plasma treatment, as evident from the frequency shifts identified in AFM images. PMID:25710305

  18. Probing the adsorption of weak acids on graphite using amplitude modulation-frequency modulation atomic force microscopy.

    PubMed

    Moustafa, Ahmed M A; Huang, Jun; McPhedran, Kerry N; Zeng, Hongbo; El-Din, Mohamed Gamal

    2015-03-17

    Recent thermodynamics calculations and adsorption isotherms showed that the adsorption of a self-assembled layer (SAL) of ionized weak acids to carbon was attributed to the negatively charged hydrogen bonding (-CAHB), yet the direct visualization and characterization of this adsorption behavior have not been reported. Here, an amplitude modulation-frequency modulation atomic force microscopy (AM-FM AFM) technique was applied to discriminate the adsorption of decanoic acids (DA) on highly ordered pyrolytic graphite (HOPG). Thermodynamics calculations revealed that the adsorption of SAL was driven by the formation of -CAHB with negatively charged functional groups of HOPG. Multilayer adsorption could occur over the adsorbed ionized SAL, leading to the development of aggregates. AM-FM AFM imaging showed that the adsorption of the DA molecules forming aggregates occurred only for the HOPG-functionalized steps, while DA molecules were found to adsorb over the entire functionalized HOPG surface after water-plasma treatment, as evident from the frequency shifts identified in AFM images.

  19. Irreversible adsorption-driven assembly of nanoparticles at fluid interfaces revealed by a dynamic surface tension probe.

    PubMed

    Bizmark, Navid; Ioannidis, Marios A; Henneke, Dale E

    2014-01-28

    Adsorption-driven self-assembly of nanoparticles at fluid interfaces is a promising bottom-up approach for the preparation of advanced functional materials and devices. Full realization of its potential requires quantitative understanding of the parameters controlling the self-assembly, the structure of nanoparticles at the interface, the barrier properties of the assembly, and the rate of particle attachment. We argue that models of dynamic surface or interfacial tension (DST) appropriate for molecular species break down when the adsorption energy greatly exceeds the mean energy of thermal fluctuations and validate alternative models extending the application of generalized random sequential adsorption theory to nanoparticle adsorption at fluid interfaces. Using a model colloidal system of hydrophobic, charge-stabilized ethyl cellulose nanoparticles at neutral pH, we demonstrate the potential of DST measurements to reveal information on the energy of adsorption, the adsorption rate constant, and the energy of particle-interface interaction at different degrees of nanoparticle coverage of the interface. These findings have significant implications for the quantitative description of nanoparticle adsorption at fluid interfaces.

  20. A kinetic study on the adsorption and reaction of hydrogen over silica-supported ruthenium and silver-ruthenium catalysts during the hydrogenation of carbon monoxide

    SciTech Connect

    VanderWiel, D.P.

    1999-02-12

    Although the catalytic hydrogenation of carbon monoxide has been a subject of considerable investigation for many years, its increasing economical attractiveness as an industrial source of hydrocarbons has recently led to a search for more active and selective catalysts. A fundamental problem in the development of such catalysts is an incomplete knowledge of the operative surface processes, due in large part to the inability to accurately measure surface concentrations of reactant species during reaction. Specifically, the concentration of surface hydrogen proves difficult to estimate using normally revealing techniques such as transient isotopic exchange due to kinetic isotope effects. Knowledge of such concentrations is essential to the determination of the mechanisms of adsorption and reaction, since many kinetic parameters are concentration dependent. It is the aim of this research to investigate the mechanism and kinetics of the adsorption and reaction of hydrogen on silica-supported ruthenium and silver-ruthenium catalysts during the hydrogenation of carbon monoxide. By preadsorbing carbon monoxide onto the surface of ruthenium and silver-ruthenium catalysts, the kinetics of hydrogen adsorption and reaction can be monitored upon exposure of this surface to ambient hydrogen gas. This is accomplished by conducting identical experiments on two separate systems. First, the formation of methane is monitored using mass spectroscopy, and specific reaction rates and apparent activation energies are measured. Next, in situ {sup 1}H-NMR is used to monitor the amount of hydrogen present on the catalyst surface during adsorption and reaction. The results for these two sets of experiments are then combined to show a correlation between the rate of reaction and the surface hydrogen concentration. Finally, transition state theory is applied to this system and is used to explain the observed change in the apparent activation energy. The structure sensitivity of hydrogen

  1. Polymerase chain reaction-gene probe detection system specific for pathogenic strains of Yersinia enterocolitica.

    PubMed

    Ibrahim, A; Liesack, W; Stackebrandt, E

    1992-08-01

    The polymerase chain reaction technique was used to develop a rapid diagnostic assay for detection of pathogenic Yersinia enterocolitica strains. The assay targeted a stretch of 163 bp of the yst gene and could be applied to both pure cultures and crude DNA extracted from feces. The defined primer pair amplified the targeted sequence from only pathogenic strains and fecal samples seeded with the serotype O:3 strain of Y. enterocolitica, whereas neither nonpathogenic strains nor normal stools yielded any amplified fragments. Of the other Yersinia species and non-Yersinia species tested, only two strains of Y. kristensenii yielded the same amplified product. A 20-mer oligonucleotide probe specifically hybridized within the amplified yst fragment of Y. enterocolitica but did not hybridize with the amplified yst fragment of Y. kristensenii by Southern and dot blot hybridizations. This confirms the reliability of this diagnostic assay in both clinical and epidemiological studies. The availability of the extracted DNA for the polymerase chain reaction was checked by simultaneous amplification of a part of the 16S rDNA and the yst gene. The entire diagnostic assay, including a simplified technique for DNA extraction, the amplification process, and gel electrophoresis, could be completed within 1 working day, which is better than the time required for the time-consuming traditional techniques used in clinical laboratories.

  2. In situ probing of the active site geometry of ultrathin nanowires for the oxygen reduction reaction

    DOE PAGES

    Liu, Haiqing; Wong, Stanislaus S.; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I.; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M.; Crooks, Richard M.; et al

    2015-09-24

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (~2 nm) core–shell Pt~Pd9Au nanowires, which have been previously shownmore » to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu~Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Thus, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.« less

  3. In situ probing of the active site geometry of ultrathin nanowires for the oxygen reduction reaction

    SciTech Connect

    Liu, Haiqing; Wong, Stanislaus S.; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I.; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M.; Crooks, Richard M.; Adzic, Radoslav R.; Liu, Ping

    2015-09-24

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (~2 nm) core–shell Pt~Pd9Au nanowires, which have been previously shown to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu~Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Thus, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.

  4. Tryptophan as a probe of photosystem I electron transfer reactions: a UV resonance Raman study.

    PubMed

    Chen, Jun; Bender, Shana L; Keough, James M; Barry, Bridgette A

    2009-08-20

    Photosystem I (PSI) is one of the two membrane-associated reaction centers involved in oxygenic photosynthesis. In photosynthesis, solar energy is converted to chemical energy in the form of a transmembrane charge separation. PSI oxidizes cytochrome c(6) or plastocyanin and reduces ferredoxin. In cyanobacterial PSI, there are 10 tryptophan residues with indole side chains located less than 10 A from the electron transfer cofactors. In this study, we apply pump-probe difference UV resonance Raman (UVRR) spectroscopy to acquire the spectrum of aromatic amino acids in cyanobacterial PSI. This UVRR technique allows the use of the tryptophan vibrational spectrum as a reporter for structural changes, which are linked to PSI electron transfer reactions. Our results show that photo-oxidation of the chlorophyll a/a' heterodimer, P(700), causes shifts in the vibrational frequencies of two or more tryptophan residues. Similar perturbations of tryptophan are observed when P(700) is chemically oxidized. The observed spectral frequencies suggest that the perturbed tryptophan side chains are only weakly or not hydrogen bonded and are located in an environment in which there is steric repulsion. The direction of the spectral shifts is consistent with an oxidation-induced increase in dielectric constant or a change in hydrogen bonding. To explain our results, the perturbation of tryptophan residues must be linked to a PSI conformational change, which is, in turn, driven by P(700) oxidation.

  5. Evanescent wave cavity ring-down spectroscopy (EW-CRDS) as a probe of macromolecule adsorption kinetics at functionalized interfaces.

    PubMed

    O'Connell, Michael A; de Cuendias, Anne; Gayet, Florence; Shirley, Ian M; Mackenzie, Stuart R; Haddleton, David M; Unwin, Patrick R

    2012-05-01

    Evanescent wave cavity ring-down spectroscopy (EW-CRDS) has been employed to study the interfacial adsorption kinetics of coumarin-tagged macromolecules onto a range of functionalized planar surfaces. Such studies are valuable in designing polymers for complex systems where the degree of interaction between the polymer and surface needs to be tailored. Three tagged synthetic polymers with different functionalities are examined: poly(acrylic acid) (PAA), poly(3-sulfopropyl methacrylate, potassium salt) (PSPMA), and a mannose-modified glycopolymer. Adsorption transients at the silica/water interface are found to be characteristic for each polymer, and kinetics are deduced from the initial rates. The chemistry of the adsorption interfaces has been varied by, first, manipulation of silica surface chemistry via the bulk pH, followed by surfaces modified by poly(L-glutamic acid) (PGA) and cellulose, giving five chemically different surfaces. Complementary atomic force microscopy (AFM) imaging has been used for additional surface characterization of adsorbed layers and functionalized interfaces to allow adsorption rates to be interpreted more fully. Adsorption rates for PSPMA and the glycopolymer are seen to be highly surface sensitive, with significantly higher rates on cellulose-modified surfaces, whereas PAA shows a much smaller rate dependence on the nature of the adsorption surface. PMID:22489550

  6. Evanescent wave cavity ring-down spectroscopy (EW-CRDS) as a probe of macromolecule adsorption kinetics at functionalized interfaces.

    PubMed

    O'Connell, Michael A; de Cuendias, Anne; Gayet, Florence; Shirley, Ian M; Mackenzie, Stuart R; Haddleton, David M; Unwin, Patrick R

    2012-05-01

    Evanescent wave cavity ring-down spectroscopy (EW-CRDS) has been employed to study the interfacial adsorption kinetics of coumarin-tagged macromolecules onto a range of functionalized planar surfaces. Such studies are valuable in designing polymers for complex systems where the degree of interaction between the polymer and surface needs to be tailored. Three tagged synthetic polymers with different functionalities are examined: poly(acrylic acid) (PAA), poly(3-sulfopropyl methacrylate, potassium salt) (PSPMA), and a mannose-modified glycopolymer. Adsorption transients at the silica/water interface are found to be characteristic for each polymer, and kinetics are deduced from the initial rates. The chemistry of the adsorption interfaces has been varied by, first, manipulation of silica surface chemistry via the bulk pH, followed by surfaces modified by poly(L-glutamic acid) (PGA) and cellulose, giving five chemically different surfaces. Complementary atomic force microscopy (AFM) imaging has been used for additional surface characterization of adsorbed layers and functionalized interfaces to allow adsorption rates to be interpreted more fully. Adsorption rates for PSPMA and the glycopolymer are seen to be highly surface sensitive, with significantly higher rates on cellulose-modified surfaces, whereas PAA shows a much smaller rate dependence on the nature of the adsorption surface.

  7. Adsorption and reaction of maleic anhydride on Mo(110), monolayer Pd(111)/Mo(110), and multilayer Pd(111)/Mo(110)

    SciTech Connect

    Xu, C.; Goodman, D.W.

    1996-04-03

    The adsorption and reaction of maleic anhydride and deuterated maleic anhydride on Mo(110), monolayer Pd/Mo(110), and multilayer Pd(111)/Mo(110) surfaces have been studied using temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). Maleic anhydride adsorbs irreversibly on the Mo(110) surface at 100 K. Heating to 1200 K yields adsorbed carbon (C{sub ads}) and gas-phase CO and H{sub 2}. In contrast, the adsorption of maleic anhydride on monolayer Pd(111)/Mo(110) and multilayer Pd(111)/Mo(110) surfaces is largely reversible with the chemisorbed maleic anhydride desorbing at 365 and 375 K, respectively. Approximately 15% of the chemisorbed maleic anhydride decomposes upon heating to 400K, forming CO, CO{sub 2} and C{sub 2}H{sub 2}; C{sub 2}H{sub 2} further dehydrogenates upon heating to C{sub ads} and gas-phase H{sub 2}. The HREELS measurements indicate that maleic anhydride is bonded to multilayer Pd(111)/Mo(110) through the olefin bond in a di-{sigma} configuration, while on monolayer Pd(111)/Mo(110), the maleic anhydride is bonded to the surface through the olefin via a {pi}-bond. On the Mo(110) surface, maleic anhydride is bonded to the surface through the ring oxygen with the molecular plane perpendicular to the surface. As a result of this modified adsorption geometry, the carbonyl stretching mode is red-shifted nearly 150 cm{sup -1} on the monolayer Pd(111)/Mo(110) surface, unshifted on the multilayer Pd(111)/Mo(110) surface, and blue-shifted by nearly 100 cm{sup -1} on the Mo(110) surface. 31 refs., 14 figs., 3 tabs.

  8. Room temperature deposition of ZnSe thin films by successive ionic layer adsorption and reaction (SILAR) method

    SciTech Connect

    Kale, R.B.; Lokhande, C.D. . E-mail: rb_kale@yahoo.co.in

    2004-10-04

    The zinc selenide (ZnSe) thin films are deposited onto glass substrate using relatively simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method. The films are deposited using zinc acetate sodium selenosulphate precursors. The concentration, pH, immersion and rinsing times and number of immersion cycles have been optimized to obtain good quality ZnSe thin films. The X-ray diffraction (XRD) study and scanning electron microscopy (SEM) studies reveals nanocrystalline nature alongwith some amorphous phase present in ZnSe thin films. Energy dispersive X-ray (EDAX) analysis shows that the films are Se deficient. From optical absorption data, the optical band gap 'E{sub g}' for as-deposited thin film was found to be 2.8 eV and electrical resistivity in the order of 10{sup 7} {omega} cm.

  9. Uptake of gaseous formaldehyde by soil surfaces: a combination of adsorption/desorption equilibrium and chemical reactions

    NASA Astrophysics Data System (ADS)

    Li, Guo; Su, Hang; Li, Xin; Kuhn, Uwe; Meusel, Hannah; Hoffmann, Thorsten; Ammann, Markus; Pöschl, Ulrich; Shao, Min; Cheng, Yafang

    2016-08-01

    Gaseous formaldehyde (HCHO) is an important precursor of OH radicals and a key intermediate molecule in the oxidation of atmospheric volatile organic compounds (VOCs). Budget analyses reveal large discrepancies between modeled and observed HCHO concentrations in the atmosphere. Here, we investigate the interactions of gaseous HCHO with soil surfaces through coated-wall flow tube experiments applying atmospherically relevant HCHO concentrations of ˜ 10 to 40 ppbv. For the determination of uptake coefficients (γ), we provide a Matlab code to account for the diffusion correction under laminar flow conditions. Under dry conditions (relative humidity = 0 %), an initial γ of (1.1 ± 0.05) × 10-4 is determined, which gradually drops to (5.5 ± 0.4) × 10-5 after 8 h experiments. Experiments under wet conditions show a smaller γ that drops faster over time until reaching a plateau. The drop of γ with increasing relative humidity as well as the drop over time can be explained by the adsorption theory in which high surface coverage leads to a reduced uptake rate. The fact that γ stabilizes at a non-zero plateau suggests the involvement of irreversible chemical reactions. Further back-flushing experiments show that two-thirds of the adsorbed HCHO can be re-emitted into the gas phase while the residual is retained by the soil. This partial reversibility confirms that HCHO uptake by soil is a complex process involving both adsorption/desorption and chemical reactions which must be considered in trace gas exchange (emission or deposition) at the atmosphere-soil interface. Our results suggest that soil and soil-derived airborne particles can either act as a source or a sink for HCHO, depending on ambient conditions and HCHO concentrations.

  10. Effects of Zeolite Structural Confinement on Adsorption Thermodynamics and Reaction Kinetics for Monomolecular Cracking and Dehydrogenation of n-Butane.

    PubMed

    Janda, Amber; Vlaisavljevich, Bess; Lin, Li-Chiang; Smit, Berend; Bell, Alexis T

    2016-04-13

    The effects of zeolite structure on the kinetics of n-butane monomolecular cracking and dehydrogenation are investigated for eight zeolites differing in the topology of channels and cages. Monte Carlo simulations are used to calculate enthalpy and entropy changes for adsorption (ΔHads-H+ and ΔSads-H+) of gas-phase alkanes onto Brønsted protons. These parameters are used to extract intrinsic activation enthalpies (ΔHint‡), entropies (ΔSint‡), and rate coefficients (kint) from measured data. As ΔSads-H+ decreases (i.e., as confinement increases), ΔHint‡ and ΔSint‡ for terminal cracking and dehydrogenation decrease for a given channel topology. These results, together with positive values observed for ΔSint‡, indicate that the transition states for these reactions resemble products. For central cracking (an earlier transition state), ΔHint‡ is relatively constant, while ΔSint‡ increases as ΔSads-H+ decreases because less entropy is lost upon protonation of the alkane. Concurrently, selectivities to terminal cracking and dehydrogenation decrease relative to central cracking because ΔSint‡ decreases for the former reactions. Depending on channel topology, changes in the measured rate coefficients (kapp) with confinement are driven by changes in kint or by changes in the adsorption equilibrium constant (Kads-H+). Values of ΔSint‡ and ΔHint‡ are positively correlated, consistent with weaker interactions between the zeolite and transition state and with the greater freedom of movement of product fragments within more spacious pores. These results differ from earlier reports that ΔHint‡ and ΔSint‡ are structure-insensitive and that kapp is dominated by Kads-H+. They also suggest that ΔSads-H+ is a meaningful descriptor of confinement for zeolites having similar channel topologies. PMID:26909765

  11. Surface pump-probe femtosecond-laser mass spectrometry: Time-, mass-, and velocity-resolved detection of surface reaction dynamics

    SciTech Connect

    Vaida, Mihai E.; Bernhardt, Thorsten M.

    2010-10-15

    A detailed account of the experimental methodology of surface pump-probe femtosecond-laser mass spectrometry is presented. This recently introduced technique enables the direct time-resolved investigation of surface reaction dynamics by monitoring the mass and the relative velocity of intermediates and products of a photoinduced surface reaction via multiphoton ionization. As a model system, the photodissociation dynamics of methyl iodide adsorbed at submonolayer coverage on magnesia ultrathin films is investigated. The magnesia surface preparation and characterization as well as the pulsed deposition of methyl iodide are described. The femtosecond-laser excitation (pump) and, in particular, the resonant multiphoton ionization surface detection (probe) schemas are discussed in detail. Results of pump-probe time-resolved methyl and iodine atom detection experiments are presented and the potential of this method for velocity-resolved photofragment analysis is evaluated.

  12. Probing adsorption of polyacrylamide-based polymers on anisotropic Basal planes of kaolinite using quartz crystal microbalance.

    PubMed

    Alagha, Lana; Wang, Shengqun; Yan, Lujie; Xu, Zhenghe; Masliyah, Jacob

    2013-03-26

    Quartz crystal microbalance with dissipation (QCM-D) was applied to investigate the adsorption characteristics of polyacrylamide-based polymers (PAMs) on anisotropic basal planes of kaolinite. Kaolinite basal planes were differentiated by depositing kaolinite nanoparticles (KNPs) on silica and alumina sensors in solutions of controlled pH values. Adsorption of an in-house synthesized organic-inorganic Al(OH)3-PAM (Al-PAM) as an example of cationic hybrid PAM and a commercially available partially hydrolyzed polyacrylamide (MF1011) as an example of anionic PAM was studied. Cationic Al-PAM was found to adsorb irreversibly and preferentially on tetrahedral silica basal planes of kaolinite. In contrast, anionic MF1011 adsorbed strongly on aluminum-hydroxy basal planes, while its adsorption on tetrahedral silica basal planes was weak and reversible. Adsorption study revealed that both electrostatic attraction and hydrogen-bonding mechanisms contribute to adsorption of PAMs on kaolinite. The adsorbed Al-PAM layer was able to release trapped water overtime and became more compact, while MF1011 film became more dissipative as backbones stretched out from kaolinite surface with minimal overlapping. Experimental results obtained from this study provide clear insights into the phenomenon that governs flocculation-based solid-liquid separation processes using multicomponent flocculants of anionic and cationic nature.

  13. Probing adsorption of polyacrylamide-based polymers on anisotropic Basal planes of kaolinite using quartz crystal microbalance.

    PubMed

    Alagha, Lana; Wang, Shengqun; Yan, Lujie; Xu, Zhenghe; Masliyah, Jacob

    2013-03-26

    Quartz crystal microbalance with dissipation (QCM-D) was applied to investigate the adsorption characteristics of polyacrylamide-based polymers (PAMs) on anisotropic basal planes of kaolinite. Kaolinite basal planes were differentiated by depositing kaolinite nanoparticles (KNPs) on silica and alumina sensors in solutions of controlled pH values. Adsorption of an in-house synthesized organic-inorganic Al(OH)3-PAM (Al-PAM) as an example of cationic hybrid PAM and a commercially available partially hydrolyzed polyacrylamide (MF1011) as an example of anionic PAM was studied. Cationic Al-PAM was found to adsorb irreversibly and preferentially on tetrahedral silica basal planes of kaolinite. In contrast, anionic MF1011 adsorbed strongly on aluminum-hydroxy basal planes, while its adsorption on tetrahedral silica basal planes was weak and reversible. Adsorption study revealed that both electrostatic attraction and hydrogen-bonding mechanisms contribute to adsorption of PAMs on kaolinite. The adsorbed Al-PAM layer was able to release trapped water overtime and became more compact, while MF1011 film became more dissipative as backbones stretched out from kaolinite surface with minimal overlapping. Experimental results obtained from this study provide clear insights into the phenomenon that governs flocculation-based solid-liquid separation processes using multicomponent flocculants of anionic and cationic nature. PMID:23398356

  14. Adsorption and oxidation of formaldehyde on a polycrystalline Pt film electrode: An in situ IR spectroscopy search for adsorbed reaction intermediates.

    PubMed

    Jusys, Zenonas; Behm, R Jürgen

    2014-01-01

    As part of a mechanistic study of the electrooxidation of C1 molecules we have systematically investigated the dissociative adsorption/oxidation of formaldehyde on a polycrystalline Pt film electrode under experimental conditions optimizing the chance for detecting weakly adsorbed reaction intermediates. Employing in situ IR spectroscopy in an attenuated total reflection configuration (ATR-FTIRS) with p-polarized IR radiation to further improve the signal-to-noise ratio, and using low reaction temperatures (3 °C) and deuterium substitution to slow down the reaction kinetics and to stabilize weakly adsorbed reaction intermediates, we could detect an IR absorption band at 1660 cm(-1) characteristic for adsorbed formyl intermediates. This assignment is supported by an isotope shift in wave number. Effects of temperature, potential and deuterium substitution on the formation and disappearance of different adsorbed species (COad, adsorbed formate, adsorbed formyl), are monitored and quantified. Consequences on the mechanism for dissociative adsorption and oxidation of formaldehyde are discussed.

  15. Probing systematic model dependence of complete fusion for reactions with the weakly bound projectiles Li,76

    NASA Astrophysics Data System (ADS)

    Kundu, A.; Santra, S.; Pal, A.; Chattopadhyay, D.; Nayak, B. K.; Saxena, A.; Kailas, S.

    2016-07-01

    Background: Complete fusion cross section measurements involving weakly bound projectiles show suppression at above-barrier energies compared to coupled-channels (CC) calculations, but no definite conclusion could be drawn for sub-barrier energies. Different CC models often lead to contrasting results. Purpose: We aim to investigate the differences in the fusion cross sections predicted by commonly used CC calculations, using codes such as fresco and ccfull, when compared to experimental data. Methods: The fusion cross sections are normalized to a dimensionless form by isolating the effect of only dynamic channel couplings calculated by both fresco and ccfull, by the method of fusion functions, and compared to a universal fusion function. This acts as a probe for obtaining the model dependence of fusion. Results: A difference is observed between the predictions of fresco and ccfull for all the reactions involving Li,76 as projectiles, and it is noticeably more for systems involving 7Li. Conclusions: With the theoretical foundations of the two CC models being different, their calculation of fusion is different even for the same system. The conclusion about the enhancement or suppression of fusion cross sections is model dependent.

  16. Local traps as nanoscale reaction-diffusion probes: B clustering in c-Si

    SciTech Connect

    Pawlak, B. J.; Cowern, N. E. B.; Ahn, C.; Vandervorst, W.; Gwilliam, R.; Berkum, J. G. M. van

    2014-12-01

    A series of B implantation experiments into initially amorphized and not fully recrystallized Si, i.e., into an existing a/c-Si bi-layer material, have been conducted. We varied B dose, energy, and temperature during implantation process itself. Significant B migration has been observed within c-Si part near the a/c-interface and near the end-of-range region before any activation annealing. We propose a general concept of local trapping sites as experimental probes of nanoscale reaction-diffusion processes. Here, the a/c-Si interface acts as a trap, and the process itself is explored as the migration and clustering of mobile BI point defects in nearby c-Si during implantation at temperatures from 77 to 573 K. We find that at room temperature—even at B concentrations as high as 1.6 atomic %, the key B-B pairing step requires diffusion lengths of several nm owing to a small, ∼0.1 eV, pairing energy barrier. Thus, in nanostructures doped by ion implantation, the implant distribution can be strongly influenced by thermal migration to nearby impurities, defects, and interfaces.

  17. Initial dynamics of the Norrish Type I reaction in acetone: probing wave packet motion.

    PubMed

    Brogaard, Rasmus Y; Sølling, Theis I; Møller, Klaus B

    2011-02-10

    The Norrish Type I reaction in the S(1) (nπ*) state of acetone is a prototype case of ketone photochemistry. On the basis of results from time-resolved mass spectrometry (TRMS) and photoelectron spectroscopy (TRPES) experiments, it was recently suggested that after excitation the wave packet travels toward the S(1) minimum in less than 30 fs and stays there for more than 100 picoseconds [Chem. Phys. Lett.2008, 461, 193]. In this work we present simulated TRMS and TRPES signals based on ab initio multiple spawning simulations of the dynamics during the first 200 fs after excitation, getting quite good agreement with the experimental signals. We can explain the ultrafast decay of the experimental signals in the following manner: the wave packet simply travels, mainly along the deplanarization coordinate, out of the detection window of the ionizing probe. This window is so narrow that subsequent revival of the signal due to the coherent deplanarization vibration is not observed, meaning that from the point of view of the experiment the wave packets travels directly to the S(1) minimum. This result stresses the importance of pursuing a closer link to the experimental signal when using molecular dynamics simulations in interpreting experimental results.

  18. Cantilevered probe detector with piezoelectric element

    SciTech Connect

    Adams, Jesse D; Sulchek, Todd A; Feigin, Stuart C

    2014-04-29

    A disclosed chemical detection system for detecting a target material, such as an explosive material, can include a cantilevered probe, a probe heater coupled to the cantilevered probe, and a piezoelectric element disposed on the cantilevered probe. The piezoelectric element can be configured as a detector and/or an actuator. Detection can include, for example, detecting a movement of the cantilevered probe or a property of the cantilevered probe. The movement or a change in the property of the cantilevered probe can occur, for example, by adsorption of the target material, desorption of the target material, reaction of the target material and/or phase change of the target material. Examples of detectable movements and properties include temperature shifts, impedance shifts, and resonant frequency shifts of the cantilevered probe. The overall chemical detection system can be incorporated, for example, into a handheld explosive material detection system.

  19. Cantilevered probe detector with piezoelectric element

    SciTech Connect

    Adams, Jesse D; Sulchek, Todd A; Feigin, Stuart C

    2013-04-30

    A disclosed chemical detection system for detecting a target material, such as an explosive material, can include a cantilevered probe, a probe heater coupled to the cantilevered probe, and a piezoelectric element disposed on the cantilevered probe. The piezoelectric element can be configured as a detector and/or an actuator. Detection can include, for example, detecting a movement of the cantilevered probe or a property of the cantilevered probe. The movement or a change in the property of the cantilevered probe can occur, for example, by adsorption of the target material, desorption of the target material, reaction of the target material and/or phase change of the target material. Examples of detectable movements and properties include temperature shifts, impedance shifts, and resonant frequency shifts of the cantilevered probe. The overall chemical detection system can be incorporated, for example, into a handheld explosive material detection system.

  20. Cantilevered probe detector with piezoelectric element

    DOEpatents

    Adams, Jesse D.; Sulchek, Todd A.; Feigin, Stuart C.

    2010-04-06

    A disclosed chemical detection system for detecting a target material, such as an explosive material, can include a cantilevered probe, a probe heater coupled to the cantilevered probe, and a piezoelectric element disposed on the cantilevered probe. The piezoelectric element can be configured as a detector and/or an actuator. Detection can include, for example, detecting a movement of the cantilevered probe or a property of the cantilevered probe. The movement or a change in the property of the cantilevered probe can occur, for example, by adsorption of the target material, desorption of the target material, reaction of the target material and/or phase change of the target material. Examples of detectable movements and properties include temperature shifts, impedance shifts, and resonant frequency shifts of the cantilevered probe. The overall chemical detection system can be incorporated, for example, into a handheld explosive material detection system.

  1. Cantilevered probe detector with piezoelectric element

    DOEpatents

    Adams, Jesse D.; Sulchek, Todd A.; Feigin, Stuart C.

    2012-07-10

    A disclosed chemical detection system for detecting a target material, such as an explosive material, can include a cantilevered probe, a probe heater coupled to the cantilevered probe, and a piezoelectric element disposed on the cantilevered probe. The piezoelectric element can be configured as a detector and/or an actuator. Detection can include, for example, detecting a movement of the cantilevered probe or a property of the cantilevered probe. The movement or a change in the property of the cantilevered probe can occur, for example, by adsorption of the target material, desorption of the target material, reaction of the target material and/or phase change of the target material. Examples of detectable movements and properties include temperature shifts, impedance shifts, and resonant frequency shifts of the cantilevered probe. The overall chemical detection system can be incorporated, for example, into a handheld explosive material detection system.

  2. All-oxide Raman-active traps for light and matter: probing redox homeostasis model reactions in aqueous environment.

    PubMed

    Alessandri, Ivano; Depero, L E

    2014-04-01

    Core-shell colloidal crystals can act as very efficient traps for light and analytes. Here it is shown that Raman-active probes can be achieved using SiO2-TiO2 core-shell beads. These systems are successfully tested in monitoring of glutathione redox cycle at physiological concentration in aqueous environment, without need of any interfering enhancers. These materials represent a promising alternative to conventional, metal-based SERS probes for investigating chemical and biochemical reactions under real working conditions.

  3. Fluorescent labelling of in situ hybridisation probes through the copper-catalysed azide-alkyne cycloaddition reaction.

    PubMed

    Hesse, Susann; Manetto, Antonio; Cassinelli, Valentina; Fuchs, Jörg; Ma, Lu; Raddaoui, Nada; Houben, Andreas

    2016-09-01

    In situ hybridisation is a powerful tool to investigate the genome and chromosome architecture. Nick translation (NT) is widely used to label DNA probes for fluorescence in situ hybridisation (FISH). However, NT is limited to the use of long double-stranded DNA and does not allow the labelling of single-stranded and short DNA, e.g. oligonucleotides. An alternative technique is the copper(I)-catalysed azide-alkyne cycloaddition (CuAAC), at which azide and alkyne functional groups react in a multistep process catalysed by copper(I) ions to give 1,4-distributed 1,2,3-triazoles at a high yield (also called 'click reaction'). We successfully applied this technique to label short single-stranded DNA probes as well as long PCR-derived double-stranded probes and tested them by FISH on plant chromosomes and nuclei. The hybridisation efficiency of differently labelled probes was compared to those obtained by conventional labelling techniques. We show that copper(I)-catalysed azide-alkyne cycloaddition-labelled probes are reliable tools to detect different types of repetitive sequences on chromosomes opening new promising routes for the detection of single copy gene. Moreover, a combination of FISH using such probes with other techniques, e.g. immunohistochemistry (IHC) and cell proliferation assays using 5-ethynyl-deoxyuridine, is herein shown to be easily feasible. PMID:27095480

  4. Ethylene Glycol Adsorption and Reaction over CeOX(111) Thin Films

    SciTech Connect

    T Chen; D Mullins

    2011-12-31

    This study reports the interaction of ethylene glycol with well-ordered CeO{sub x}(111) thin film surfaces. Ethylene glycol initially adsorbs on fully oxidized CeO{sub 2}(111) and reduced CeO{sub 2-x}(111) through the formation of one C-O-Ce bond and then forms a second alkoxy bond after annealing. On fully oxidized CeO{sub 2}(111) both recombination of ethylene glycol and water desorption occur at low temperature leaving stable -OCH{sub 2}CH{sub 2}O- (ethylenedioxy) intermediates and oxygen vacancies on the surface. This ethylenedioxy intermediate goes through C-C bond scission to produce formate species which then react to produce CO and CO{sub 2}. The formation of water results in the reduction of the ceria. On a reduced CeO{sub 2-x}(111) surface the reaction selectivity shifts toward a dehydration process. The ethylenedioxy intermediate decomposes by breaking a C-O bond and converts into an enolate species. Similar to the reaction of acetaldehyde on reduced CeO{sub 2-x}(111), the enolate reacts to produce acetaldehyde, acetylene, and ethylene. The loss of O from ethylene glycol leads to a small amount of oxidation of the reduced ceria.

  5. Ethylene Glycol Adsorption and Reaction over CeOX(111) Thin Films

    SciTech Connect

    Mullins, David R; Chen, Tsung-Liang

    2011-01-01

    This study reports the interaction of ethylene glycol with well-ordered CeO{sub x}(111) thin film surfaces. Ethylene glycol initially adsorbs on fully oxidized CeO{sub 2}(111) and reduced CeO{sub 2-x}(111) through the formation of one C-O-Ce bond and then forms a second alkoxy bond after annealing. On fully oxidized CeO{sub 2}(111) both recombination of ethylene glycol and water desorption occur at low temperature leaving stable -OCH{sub 2}CH{sub 2}O- (ethylenedioxy) intermediates and oxygen vacancies on the surface. This ethylenedioxy intermediate goes through C-C bond scission to produce formate species which then react to produce CO and CO{sub 2}. The formation of water results in the reduction of the ceria. On a reduced CeO{sub 2-x}(111) surface the reaction selectivity shifts toward a dehydration process. The ethylenedioxy intermediate decomposes by breaking a C-O bond and converts into an enolate species. Similar to the reaction of acetaldehyde on reduced CeO{sub 2-x}(111), the enolate reacts to produce acetaldehyde, acetylene, and ethylene. The loss of O from ethylene glycol leads to a small amount of oxidation of the reduced ceria.

  6. Intermediates in the cation reactions in solution probed by an in situ surface enhanced Raman scattering method

    NASA Astrophysics Data System (ADS)

    Tan, Chih-Shan; Chen, Hung-Ying; Chen, Hsueh-Szu; Gwo, Shangjr; Chen, Lih-Juann

    2015-09-01

    For chemical reactions in liquid state, such as catalysis, understanding of dynamical changes is conducive to practical applications. Solvation of copper salts in aqueous solution has implications for life, the environment, and industry. In an ongoing research, the question arises that why the color of aqueous CuCl2 solution changes with solution concentration? In this work, we have developed a convenient and efficient in situ surface enhanced Raman scattering technique to probe the presence of many intermediates, some of them are responsible for color change, in crystallization of aqueous copper chloride solution. The versatility of the novel technique was confirmed in the identification of five intermediates states in the transition from CdS to MoS2 nanowires in solution. The facile in situ method is expected to be widely applicable in probing intermediate states in a variety of chemical reactions in solution.

  7. Intermediates in the cation reactions in solution probed by an in situ surface enhanced Raman scattering method.

    PubMed

    Tan, Chih-Shan; Chen, Hung-Ying; Chen, Hsueh-Szu; Gwo, Shangjr; Chen, Lih-Juann

    2015-01-01

    For chemical reactions in liquid state, such as catalysis, understanding of dynamical changes is conducive to practical applications. Solvation of copper salts in aqueous solution has implications for life, the environment, and industry. In an ongoing research, the question arises that why the color of aqueous CuCl2 solution changes with solution concentration? In this work, we have developed a convenient and efficient in situ surface enhanced Raman scattering technique to probe the presence of many intermediates, some of them are responsible for color change, in crystallization of aqueous copper chloride solution. The versatility of the novel technique was confirmed in the identification of five intermediates states in the transition from CdS to MoS2 nanowires in solution. The facile in situ method is expected to be widely applicable in probing intermediate states in a variety of chemical reactions in solution. PMID:26333518

  8. Photochemical primary process of photo-Fries rearrangement reaction of 1-naphthyl acetate as studied by MFE probe.

    PubMed

    Gohdo, Masao; Takamasu, Tadashi; Wakasa, Masanobu

    2011-01-14

    Photo-Fries rearrangement reactions of 1-naphthyl acetate (NA) in n-hexane and in cyclohexane were studied by the magnetic field effect probe (MFE probe) under magnetic fields (B) of 0 to 7 T. Transient absorptions of the 1-naphthoxyl radical, T-T absorption of NA, and a short-lifetime intermediate (τ = 24 ns) were observed by a nanosecond laser flash photolysis technique. In n-hexane, the yield of escaped 1-naphthoxyl radicals dropped dramatically upon application of a 3 mT field, but then the yield increased with increasing B for 3 mT < B≤ 7 T. These observed MFEs can be explained by the hyperfine coupling and the Δg mechanisms through the singlet radical pair. The fact that MFEs were observed for the present photo-Fries rearrangement reaction indicates the presence of a singlet radical pair intermediate with a lifetime as long as several tens of nanoseconds.

  9. Intermediates in the cation reactions in solution probed by an in situ surface enhanced Raman scattering method

    PubMed Central

    Tan, Chih-Shan; Chen, Hung-Ying; Chen, Hsueh-Szu; Gwo, Shangjr; Chen, Lih-Juann

    2015-01-01

    For chemical reactions in liquid state, such as catalysis, understanding of dynamical changes is conducive to practical applications. Solvation of copper salts in aqueous solution has implications for life, the environment, and industry. In an ongoing research, the question arises that why the color of aqueous CuCl2 solution changes with solution concentration? In this work, we have developed a convenient and efficient in situ surface enhanced Raman scattering technique to probe the presence of many intermediates, some of them are responsible for color change, in crystallization of aqueous copper chloride solution. The versatility of the novel technique was confirmed in the identification of five intermediates states in the transition from CdS to MoS2 nanowires in solution. The facile in situ method is expected to be widely applicable in probing intermediate states in a variety of chemical reactions in solution. PMID:26333518

  10. Non-Covalent Fluorescent Labeling of Hairpin DNA Probe Coupled with Hybridization Chain Reaction for Sensitive DNA Detection.

    PubMed

    Song, Luna; Zhang, Yonghua; Li, Junling; Gao, Qiang; Qi, Honglan; Zhang, Chengxiao

    2016-04-01

    An enzyme-free signal amplification-based assay for DNA detection was developed using fluorescent hairpin DNA probes coupled with hybridization chain reaction (HCR). The hairpin DNAs were designed to contain abasic sites in the stem moiety. Non-covalent labeling of the hairpin DNAs was achieved when a fluorescent ligand was bound to the abasic sites through hydrogen bonding with the orphan cytosine present on the complementary strand, accompanied by quench of ligand fluorescence. As a result, the resultant probes, the complex formed between the hairpin DNA and ligand, showed almost no fluorescence. Upon hybridization with target DNA, the probe underwent a dehybridization of the stem moiety containing an abasic site. The release of ligand from the abasic site to the solution resulted in an effective fluorescent enhancement, which can be used as a signal. Compared with a sensing system without HCR, a 20-fold increase in the sensitivity was achieved using the sensing system with HCR. The fluorescent intensity of the sensing system increased with the increase in target DNA concentration from 0.5 nM to 100 nM. A single mismatched target ss-DNA could be effectively discriminated from complementary target DNA. Genotyping of a G/C single-nucleotide polymorphism of polymerase chain reaction (PCR) products was successfully demonstrated with the sensing system. Therefore, integrating HCR strategy with non-covalent labeling of fluorescent hairpin DNA probes provides a sensitive and cost-effective DNA assay.

  11. A Fluorescent Molecular Probe for the Detection of Hydrogen Based on Oxidative Addition Reactions with Crabtree-Type Hydrogenation Catalysts.

    PubMed

    Kos, Pavlo; Plenio, Herbert

    2015-11-01

    A Crabtree-type Ir(I) complex tagged with a fluorescent dye (bodipy) was synthesized. The oxidative addition of H2 converts the weakly fluorescent Ir(I) complex (Φ=0.038) into a highly fluorescent Ir(III) species (Φ=0.51). This fluorogenic reaction can be utilized for the detection of H2 and to probe the oxidative addition step in the catalytic hydrogenation of olefins.

  12. Search for mycobacteria in interstitial cystitis using mycobacteria-specific DNA probes with signal amplification by polymerase chain reaction.

    PubMed

    Hampson, S J; Christmas, T J; Moss, M T

    1993-09-01

    The aetiology of interstitial cystitis is not known. Various infective agents have been postulated and although recognised as perpetrators of chronic inflammatory conditions, mycobacteria have never been satisfactorily excluded from interstitial cystitis. If present in interstitial cystitis tissue, mycobacteria exist either in very small numbers or in forms which contemporary staining techniques fail to recognise. We used a polymerase chain reaction with mycobacteria-specific DNA probes and found no evidence of mycobacterial involvement in 8 cases of proven interstitial cystitis.

  13. Adsorption and Reaction of C1-C3 Alcohols over CeOx(111) Thin Films

    SciTech Connect

    D Mullins; S Senanayake; T Chen

    2011-12-31

    This study reports the interaction of methanol, ethanol, 1-propanol, and 2-propanol with well-ordered CeO{sub 2}(111) thin film surfaces. All of the alcohols adsorb at low temperature by forming alkoxy and hydroxyl species on the surface. On fully oxidized CeO{sub 2}(111), recombination occurs between some of the alkoxys and hydroxyls, resulting in alcohol desorption near 220 K. At the same temperature, some of the surface hydroxyls disproportionate to produce water and the loss of lattice O. The remaining alkoxys react above 550 K. The primary alcohols favor dehydrogenation products (aldehydes). There is a net loss of O from the system, resulting in a reduction of the ceria. The secondary alcohol, 2-propanol, undergoes primarily dehydration, producing propene with no net change in the cerium oxidation state. Reduced CeO{sub x}(111) competes with the gaseous products for available O. Little or no water is produced. The reaction selectivity for the C{sub 2} and C{sub 3} alcohols shifts toward favoring dehydration products. The loss of O from the alcohols leads to oxidation of the reduced ceria. Compared with the oxidized surface, the alkene desorption shifts to lower temperature, whereas the aldehyde desorption shifts to higher temperature. This indicates that, on the reduced surface, it is easier to break the C-O bond but more difficult to break the O-substrate bond.

  14. Probing the low temperature initiation sites in Fe-, Mn-promoted sulfated zirconia via CO and H{sub 2} adsorption

    SciTech Connect

    Sayari, A.; Yang, Y.

    1999-10-01

    Exposure of freshly activated Fe-, Mn-promoted sulfated zirconia (SFMZ) to carbon monoxide at temperatures up to 50 C induced permanent loss of activity, while the addition of CO after the beginning of the reaction had a reversible effect, regardless of whether the butane flow has been interrupted or not. Similar experiments using dissociated hydrogen instead of CO led to irreversible poisoning in all cases. These findings were interpreted based on (1) the occurrence of initiation sites that are consumed stoichiometrically and very rapidly upon exposure to butane, (2) such initiation sites which are also consumed by CO or dissociated hydrogen, (3) CO which competes effectively for adsorption sites without affecting accumulated reaction intermediates, and (4) such intermediates that are removed in the presence of dissociated hydrogen.

  15. FTIR/TDS studies of reaction paths and surface intermediates following multilayer adsorption of formamide on Ni(111)

    SciTech Connect

    Gao, Quanyin; Hemminger, J.C. ); Erley, W.; Sander, D.; Ibach, H. )

    1991-01-10

    The adsorption and reaction of HCONH{sub 2} and HCOND{sub 2} molecules on Ni(111) were studied following initial multilayer exposures with thermal desorption spectroscopy (TDS) and reflection absorption infrared spectroscopy (RAIR). At 90 K, formamide molecules (HCONH{sub 2}) adsorb on Ni(111) forming multilayers. Three molecular desorption peaks were observed at 160, 170, and 190 K, respectively. Heating this system to above 220 K leads to the decomposition of formamide molecules. Two parallel decomposition paths were observed. One path leads to the production of NH{sub 3}, H{sub 2}, and CO. The other path, which is first reported here, gives HNCO and H{sub 2}. Possible surface precursors for the two decomposition paths are discussed. The temperature-dependent RAIR spectra indicated that ammonia (NH{sub 3(a)}) was formed at about 230 K, isocyanic acid (HNCO{sub (a)}) at about 285 K, and CO at about 285 K. The observed desorption temperature from TDS are 260 K for ammonia (NH{sub 3}) 325 K for isocyanic acid (HNCO), 340 K for hydrogen (H{sub 2}), and 410 K for carbon monoxide (CO). The competing route for formamide decomposition that leads to HNCO production on Ni(111) has not been reported on other transition-metal substrates.

  16. Cation location in microporous zeolite, SSZ-13, probed with xenon adsorption measurement and 129Xe NMR spectrum.

    PubMed

    Shin, Na Ra; Kim, Su Hyun; Shin, Hye Sun; Jang, Ik Jun; Cho, Sung June

    2013-06-01

    The location of metal ion, Ag2+, Ca2+, Cu2+ and Y3+ in the SSZ-13 has been investigated with xenon adsorption measurement and 129Xe NMR spectrum. It was referred that the location of the metal ion varies depending on the corresponding charge. The ion-exchanged Ag ion was located in the alpha-cage to interact directly with xenon. Others multivalent cation contributed little with xenon because these were present near the six membered rings where xenon cannot access. PMID:23862500

  17. Probing the adsorption mechanism in thiamazole bound to the silver surface with Surface-enhanced Raman Scattering and DFT

    NASA Astrophysics Data System (ADS)

    Biswas, Nandita; Thomas, Susy; Sarkar, Anjana; Mukherjee, Tulsi; Kapoor, Sudhir

    2009-09-01

    Surface-enhanced Raman scattering (SERS) of thiamazole have been investigated in aqueous solution. Thiamazole is an important anti-thyroid drug that is used in the treatment of hyperthyroidism (over activity of the thyroid gland). Due to its medicinal importance, the surface adsorption properties of thiamazole have been studied. The experimental Raman and SERS data are supported with DFT calculations using B3LYP functional with LANL2DZ basis set. From the SERS spectra as well as theoretical calculations, it has been inferred that thiamazole is chemisorbed to the silver surface directly through the sulphur atom and the ring N atom, with a tilted orientation.

  18. A mechanistic study of H2S adsorption and dissociation on Cu2O(1 1 1) surfaces: Thermochemistry, reaction barrier

    NASA Astrophysics Data System (ADS)

    Zhang, Riguang; Liu, Hongyan; Li, Jingrui; Ling, Lixia; Wang, Baojun

    2012-10-01

    The interaction mechanism of H2S with different Cu2O(1 1 1) surfaces, including perfect, oxygen-vacancy and sulfur-containing surfaces, have been systematically studied using periodic density functional calculations. Different kinds of possible modes of H2S, as well as the resultant SH and S species adsorbed on these surfaces are identified. Two types of pathways via molecular and dissociative adsorption processes are mapped out. Our results show that sulfur species (H2S, SH and S) interact with surface Cu centers; H2S exists in the form of molecular adsorption on perfect and sulfur-containing surfaces; the dissociative adsorption of H2S occurs predominantly on oxygen-vacancy surface, suggesting that oxygen-vacancy exhibits a strong catalytic activity toward the dissociation of H2S. On the other hand, the dissociation processes of the molecular and dissociative adsorption H2S, leading to final product S species on these Cu2O(1 1 1) surfaces, show that the overall dissociation process is exothermic. Meanwhile, with respect to molecular adsorption H2S, the activation barrier and reaction energy of the overall dissociation process on perfect and oxygen-vacancy surfaces indicate that H2S can easily dissociate into S species. Importantly, in the case of dissociative adsorption of H2S, the dissociation of H2S into S species is a spontaneous process with respect to molecular adsorption H2S. However, on sulfur-containing surface, the presence of surface S atom goes against the Hsbnd S bond-breaking process both thermodynamically and kinetically. Finally, the vibrational frequencies for the adsorbed H2S, SH and S species on these surfaces have been obtained, which can be applied to guide surface vibrational spectroscopy in experiment.

  19. Reaction-based small-molecule fluorescent probes for chemoselective bioimaging

    NASA Astrophysics Data System (ADS)

    Chan, Jefferson; Dodani, Sheel C.; Chang, Christopher J.

    2012-12-01

    The dynamic chemical diversity of elements, ions and molecules that form the basis of life offers both a challenge and an opportunity for study. Small-molecule fluorescent probes can make use of selective, bioorthogonal chemistries to report on specific analytes in cells and in more complex biological specimens. These probes offer powerful reagents to interrogate the physiology and pathology of reactive chemical species in their native environments with minimal perturbation to living systems. This Review presents a survey of tools and tactics for using such probes to detect biologically important chemical analytes. We highlight design criteria for effective chemical tools for use in biological applications as well as gaps for future exploration.

  20. The Effect of Simulated Microgravity Environment of RWV Bioreactors on Surface Reactions and Adsorption of Serum Proteins on Bone-bioactive Microcarriers

    NASA Technical Reports Server (NTRS)

    Radin, Shula; Ducheyne, P.; Ayyaswamy, P. S.

    2003-01-01

    Biomimetically modified bioactive materials with bone-like surface properties are attractive candidates for use as microcarriers for 3-D bone-like tissue engineering under simulated microgravity conditions of NASA designed rotating wall vessel (RWV) bioreactors. The simulated microgravity environment is attainable under suitable parametric conditions of the RWV bioreactors. Ca-P containing bioactive glass (BG), whose stimulatory effect on bone cell function had been previously demonstrated, was used in the present study. BG surface modification via reactions in solution, resulting formation of bone-like minerals at the surface and adsorption of serum proteins is critical for obtaining the stimulatory effect. In this paper, we report on the major effects of simulated microgravity conditions of the RWV on the BG reactions surface reactions and protein adsorption in physiological solutions. Control tests at normal gravity were conducted at static and dynamic conditions. The study revealed that simulated microgravity remarkably enhanced reactions involved in the BG surface modification, including BG dissolution, formation of bone-like minerals at the surface and adsorption of serum proteins. Simultaneously, numerical models were developed to simulate the mass transport of chemical species to and from the BG surface under normal gravity and simulated microgravity conditions. The numerical results showed an excellent agreement with the experimental data at both testing conditions.

  1. Adsorption and Reaction of Acetaldehyde on Shape-Controlled CeO2 Nanocrystals: Elucidation of Structure-function Relationships

    SciTech Connect

    Mann, Amanda K; Wu, Zili; Calaza, Florencia; Overbury, Steven {Steve} H

    2014-01-01

    CeO2 cubes with {100} facets, octahedra with {111} facets, and wires with highly defective structures were utilized to probe the structure-dependent reactivity of acetaldehyde. Using temperature-programmed desorption (TPD), temperature-programmed surface reactions (TPSR), and in situ infrared spectroscopy it was found that acetaldehyde desorbs unreacted or undergoes reduction, coupling, or C-C bond scission reactions depending on the surface structure of CeO2. Room temperature FTIR indicates that acetaldehyde binds primarily as 1-acetaldehyde on the octahedra, in a variety of conformations on the cubes, including coupling products and acetate and enolate species, and primarily as coupling products on the wires. The percent consumption of acetaldehyde follows the order of wires > cubes > octahedra. All the nanoshapes produce the coupling product crotonaldehyde; however, the selectivity to produce ethanol follows the order wires cubes >> octahedra. The selectivity and other differences can be attributed to the variation in the basicity of the surfaces, defects densities, coordination numbers of surface atoms, and the reducibility of the nanoshapes.

  2. A Chemical-Adsorption Strategy to Enhance the Reaction Kinetics of Lithium-Rich Layered Cathodes via Double-Shell Surface Modification.

    PubMed

    Guo, Lichao; Li, Jiajun; Cao, Tingting; Wang, Huayu; Zhao, Naiqin; He, Fang; Shi, Chunsheng; He, Chunnian; Liu, Enzuo

    2016-09-21

    Sluggish surface reaction kinetics hinders the power density of Li-ion battery. Thus, various surface modification techniques have been applied to enhance the electronic/ionic transfer kinetics. However, it is challenging to obtain a continuous and uniform surface modification layer on the prime particles with structure integration at the interface. Instead of classic physical-adsorption/deposition techniques, we propose a novel chemical-adsorption strategy to synthesize double-shell modified lithium-rich layered cathodes with enhanced mass transfer kinetics. On the basis of experimental measurement and first-principles calculation, MoO2S2 ions are proved to joint the layered phase via chemical bonding. Specifically, the Mo-O or Mo-S bonds can flexibly rotate to bond with the cations in the layered phase, leading to the good compatibility between the thiomolybdate adsorption layer and layered cathode. Followed by annealing treatment, the lithium-excess-spinel inner shell forms under the thiomolybdate adsorption layer and functions as favorable pathways for lithium and electron. Meanwhile, the nanothick MoO3-x(SO4)x outer shell protects the transition metal from dissolution and restrains electrolyte decomposition. The double-shell modified sample delivers an enhanced discharge capacity almost twice as much as that of the unmodified one at 1 A g(-1) after 100 cycles, demonstrating the superiority of the surface modification based on chemical adsorption. PMID:27582053

  3. A Chemical-Adsorption Strategy to Enhance the Reaction Kinetics of Lithium-Rich Layered Cathodes via Double-Shell Surface Modification.

    PubMed

    Guo, Lichao; Li, Jiajun; Cao, Tingting; Wang, Huayu; Zhao, Naiqin; He, Fang; Shi, Chunsheng; He, Chunnian; Liu, Enzuo

    2016-09-21

    Sluggish surface reaction kinetics hinders the power density of Li-ion battery. Thus, various surface modification techniques have been applied to enhance the electronic/ionic transfer kinetics. However, it is challenging to obtain a continuous and uniform surface modification layer on the prime particles with structure integration at the interface. Instead of classic physical-adsorption/deposition techniques, we propose a novel chemical-adsorption strategy to synthesize double-shell modified lithium-rich layered cathodes with enhanced mass transfer kinetics. On the basis of experimental measurement and first-principles calculation, MoO2S2 ions are proved to joint the layered phase via chemical bonding. Specifically, the Mo-O or Mo-S bonds can flexibly rotate to bond with the cations in the layered phase, leading to the good compatibility between the thiomolybdate adsorption layer and layered cathode. Followed by annealing treatment, the lithium-excess-spinel inner shell forms under the thiomolybdate adsorption layer and functions as favorable pathways for lithium and electron. Meanwhile, the nanothick MoO3-x(SO4)x outer shell protects the transition metal from dissolution and restrains electrolyte decomposition. The double-shell modified sample delivers an enhanced discharge capacity almost twice as much as that of the unmodified one at 1 A g(-1) after 100 cycles, demonstrating the superiority of the surface modification based on chemical adsorption.

  4. Stigmatellin Probes the Electrostatic Potential in the QB Site of the Photosynthetic Reaction Center

    PubMed Central

    Gerencsér, László; Boros, Bogáta; Derrien, Valerie; Hanson, Deborah K.; Wraight, Colin A.; Sebban, Pierre; Maróti, Péter

    2015-01-01

    The electrostatic potential in the secondary quinone (QB) binding site of the reaction center (RC) of the photosynthetic bacterium Rhodobacter sphaeroides determines the rate and free energy change (driving force) of electron transfer to QB. It is controlled by the ionization states of residues in a strongly interacting cluster around the QB site. Reduction of the QB induces change of the ionization states of residues and binding of protons from the bulk. Stigmatellin, an inhibitor of the mitochondrial and photosynthetic respiratory chain, has been proven to be a unique voltage probe of the QB binding pocket. It binds to the QB site with high affinity, and the pK value of its phenolic group monitors the local electrostatic potential with high sensitivity. Investigations with different types of detergent as a model system of isolated RC revealed that the pK of stigmatellin was controlled overwhelmingly by electrostatic and slightly by hydrophobic interactions. Measurements showed a high pK value (>11) of stigmatellin in the QB pocket of the dark-state wild-type RC, indicating substantial negative potential. When the local electrostatics of the QB site was modulated by a single mutation, L213Asp→Ala, or double mutations, L213Asp-L212Glu→Ala-Ala (AA), the pK of stigmatellin dropped to 7.5 and 7.4, respectively, which corresponds to a >210 mV increase in the electrostatic potential relative to the wild-type RC. This significant pK drop (ΔpK > 3.5) decreased dramatically to (ΔpK > 0.75) in the RC of the compensatory mutant (AA+M44Asn→AA+M44Asp). Our results indicate that the L213Asp is the most important actor in the control of the electrostatic potential in the QB site of the dark-state wild-type RC, in good accordance with conclusions of former studies using theoretical calculations or light-induced charge recombination assay. PMID:25606686

  5. PbS Quantum Dots Sensitized TiO2 Solar Cells Prepared by Successive Ionic Layer Absorption and Reaction with Different Adsorption Layers.

    PubMed

    Yi, Jie; Duan, Yanfang; Liu, Chunxia; Gao, Shaohong; Han, Xueting; An, Limin

    2016-04-01

    Lead sulfide (PbS) quantum dots (QDs) have been synthesized via successive ionic layer adsorption and reaction (SILAR) on a titanium dioxide (TiO2) nanoporous film for the fabrication of quantum dot-sensitized solar cells (QDSCs). The reaction is environmental friendly and energy saving. The green synthesized PbS QDs match the maximum remittance region of the solar spectrum and are suitable as sensitizers for TiO2 electrodes for cell devices application. PbS QDs were adsorbed in different adsorption layers in order to improve the solar cell performance. The optical properties of PbS sensitized TiO2 films were studied by scanning electron microscopy and UV-Vis absorbance spectroscopy. The photovoltaic characteristics of the PbS QDSCs were analyzed by I-V characteristics and electrochemical impedance spectroscopy. As a result, the light harvesting was enhanced with increasing SILAR adsorption layers. The maximum photovoltaic conversion efficiency of the PbS QDSCs (3.14%) was obtained at the 12 adsorption layers with the highest short circuit current density and lowest charge transfer resistance. PMID:27451735

  6. Surface sampling concentration and reaction probe with controller to adjust sampling position

    DOEpatents

    Van Berkel, Gary J.; ElNaggar, Mariam S.

    2016-07-19

    A method of analyzing a chemical composition of a specimen is described. The method can include providing a probe comprising an outer capillary tube and an inner capillary tube disposed co-axially within the outer capillary tube, where the inner and outer capillary tubes define a solvent capillary and a sampling capillary in fluid communication with one another at a distal end of the probe; contacting a target site on a surface of a specimen with a solvent in fluid communication with the probe; maintaining a plug volume proximate a solvent-specimen interface, wherein the plug volume is in fluid communication with the probe; draining plug sampling fluid from the plug volume through the sampling capillary; and analyzing a chemical composition of the plug sampling fluid with an analytical instrument. A system for performing the method is also described.

  7. Development of optical probes for in vivo imaging of polarized macrophages during foreign body reactions

    PubMed Central

    Tsai, Yi-Ting; Patty, Kaitlen M; Weng, Hong; Tang, Ewin N.; Nair, Ashwin; Hu, Wen-Jing; Tang, Liping

    2014-01-01

    Plasticity of macrophages (MΦ) phenotypes exist in a spectrum from classically activated (M1) cells, to alternatively activated (M2) cells, contributing to both the normal healing of tissues and the pathogenesis of implant failure. Here, folate- and mannose-based optical probes were fabricated to simultaneously determine the degree of MΦ polarization. In vitro tests show the ability of these probes to specifically target M1 and M2 cells. In an in vivo murine model, they were able to distinguish between M1-dominated inflammatory response to infection and M2-dominated regenerative response to particle implants. Finally, the probes were used to assess the inflammatory/ regenerative property of biomaterial implants. Our results show that these probes can be used to monitor and quantify the dynamic processes of MΦ polarization and their role in cellular responses in real time. PMID:24726956

  8. SpiroZin1: a reversible and pH-Insensitive, reaction-based, red-fluorescent probe for imaging biological mobile zinc.

    PubMed

    Rivera-Fuentes, Pablo; Lippard, Stephen J

    2014-06-01

    A reversible, reaction-based sensor for biological mobile zinc was designed, prepared, and characterized. The sensing mechanism of this probe is based on the zinc-induced, ring-opening reaction of spirobenzopyran to give a cyanine fluorophore that emits in the deep-red region of the electromagnetic spectrum. This probe is not activated by protons and operates efficiently in aqueous solution at pH 7 and high ionic strength. The mechanism of this reaction was studied by using a combination of kinetics experiments and DFT calculations. The biocompatibility of the probe was demonstrated in live HeLa cells.

  9. A Class of Multiresponsive Colorimetric and Fluorescent pH Probes via Three Different Reaction Mechanisms of Salen Complexes: A Selective and Accurate pH Measurement.

    PubMed

    Cheng, Jinghui; Gou, Fei; Zhang, Xiaohong; Shen, Guangyu; Zhou, Xiangge; Xiang, Haifeng

    2016-09-19

    We report a class of multiresponsive colorimetric and fluorescent pH probes based on three different reaction mechanisms including cation exchange, protonation, and hydrolysis reaction of K(I), Ca(II), Zn(II), Cu(II), Al(III), and Pd(II) Salen complexes. Compared with traditional pure organic pH probes, these complex-based pH probes exhibited a much better selectivity due to the shielding function of the filled-in metal ion in the complex. Their pH sensing performances were affected by the ligand structure and the central metal ion. This work is the first report of "off-on-on'-off" colorimetric and fluorescent pH probes that possess three different reaction mechanisms and should inspire the design of multiple-responsive probes for important analytes in biological systems.

  10. Infrared study of the adsorption and reaction of methyl chloride and methyl iodide on silica-supported Pt catalysts

    SciTech Connect

    McGee, K.C.; Driessen, M.D.; Grassian, V.H.

    1996-03-01

    The low-temperature adsorption of methyl chloride and methyl iodide on silica-supported Pt catalysts has been investigated by transmission Fourier transform infrared spectroscopy. The IR data show that methyl chloride and methyl iodide dissociate at low temperatures (near 200 K) to form an adsorbed hydrocarbon fragment on the surface, identified as methyl groups. Methyl groups are characterized by a single infrared absorption band near 2965 cm{sup -1}. Methyl groups react with hydrogen to form gas-phase methane as the sample is warmed between 200 and 473 K. Reaction of approximately 10 Torr of methyl chloride at 473 K over a Pt/SiO{sub 2} catalyst shows that only 20% of the methyl chloride decomposes to form gas-phase methane and hydrogen chloride in the absence of hydrogen. However, in the presence of an equal amount of hydrogen, all of the methyl chloride is converted to methane and hydrogen chloride. In contrast to the quantitative conversion of methyl chloride, less than 10% of the initial 10 Torr of methyl iodide forms methane at 473 K and no hydrogen iodide forms in the presence or absence of hydrogen gas. Although the activation barrier for C-Cl bond dissociation in adsorbed methyl chloride is higher than the barrier for C-I bond dissociation in adsorbed methyl iodide, the lower energy barrier for removal of adsorbed chlorine compared to adsorbed iodine is the cause of the higher catalytic activity of Pt/SiO{sub 2} toward methyl chloride decomposition. In addition to the thermal decomposition of CH{sub 3}Cl, the authors have investigated the possibility of using solar radiation for the decomposition of CH{sub 3}Cl on Pt/SiO{sub 2}. The results for the photo-assisted decomposition of CH{sub 3}Cl adsorbed on Pt/SiO{sub 2} are presented and discussed. 39 refs., 12 figs., 3 tabs.

  11. Wet chemical synthesis of quantum confined nanostructured tin oxide thin films by successive ionic layer adsorption and reaction technique

    SciTech Connect

    Murali, K.V.; Ragina, A.J.; Preetha, K.C.; Deepa, K.; Remadevi, T.L.

    2013-09-01

    Graphical abstract: - Highlights: • Quantum confined SnO{sub 2} thin films were synthesized at 80 °C by SILAR technique. • Film formation mechanism is discussed. • Films with snow like crystallite morphology offer high specific surface area. • The blue-shifted value of band gap confirmed the quantum confinement effect. • Present synthesis has advantages – low cost, low temperature and green friendly. - Abstract: Quantum confined nanostructured SnO{sub 2} thin films were synthesized at 353 K using ammonium chloride (NH{sub 4}Cl) and other chemicals by successive ionic layer adsorption and reaction technique. Film formation mechanism is discussed. Structural, morphological, optical and electrical properties were investigated and compared with the as-grown and annealed films fabricated without NH{sub 4}Cl solution. SnO{sub 2} films were polycrystalline with crystallites of tetragonal structure with grain sizes lie in the 5–8 nm range. Films with snow like crystallite morphology offer high specific surface area. The blue-shifted value of band gap of as-grown films confirmed the quantum confinement effect of grains. Refractive index of the films lies in the 2.1–2.3 range. Films prepared with NH{sub 4}Cl exhibit relatively lower resistivity of the order of 10{sup 0}–10{sup −1} Ω cm. The present synthesis has advantages such as low cost, low temperature and green friendly, which yields small particle size, large surface–volume ratio, and high crystallinity SnO{sub 2} films.

  12. Reaction-based small-molecule fluorescent probes for chemoselective bioimaging

    PubMed Central

    Chan, Jefferson; Dodani, Sheel C.; Chang, Christopher J.

    2014-01-01

    The dynamic chemical diversity of elements, ions and molecules that form the basis of life offers both a challenge and an opportunity for study. Small-molecule fluorescent probes can make use of selective, bioorthogonal chemistries to report on specific analytes in cells and in more complex biological specimens. These probes offer powerful reagents to interrogate the physiology and pathology of reactive chemical species in their native environments with minimal perturbation to living systems. This Review presents a survey of tools and tactics for using such probes to detect biologically important chemical analytes. We highlight design criteria for effective chemical tools for use in biological applications as well as gaps for future exploration. PMID:23174976

  13. Probing Defect Sites on CeO2 Nanocrystals with Well-Defined Surface Planes by Raman Spectroscopy and O2 Adsorption

    SciTech Connect

    Wu, Zili; Li, Meijun; Howe, Jane Y; Meyer III, Harry M; Overbury, Steven {Steve} H

    2010-01-01

    Defect sites play an essential role in ceria catalysis. In this study, ceria nanocrystals with well defined surface planes have been synthesized and utilized for studying defect sites with both Raman spectroscopy and O2 adsorption. Ceria nanorods ({110} + {100}), nanocubes ({100}), and nano-octahedrons ({111}) are employed to analyze the quantity and quality of defect sites on different ceria surfaces. On oxidized surface, nanorods have the most abundant intrinsic defect sites, followed by nanocubes and nano-octahedrons. When reduced, the induced defect sites are more clustered on nanorods than on nanocubes although similar amount (based on surface area) of such defect sites are produced on the two surfaces. Very few defect sites can be generated on the nano-octahedrons due to the least reducibility. These differences can be rationalized by the crystallographic surface terminations of the ceria nanocrystals. The different defect sites on these nanocrystals lead to the adsorption of different surface dioxygen species. Superoxide on one-electron defect sites and peroxide on two-electron defect sites with different clustering degree are identified on the ceria nanocrystals depending on their morphology. Furthermore, the stability and reactivity of these oxygen species are also found to be surface-dependent, which is of significance for ceria-catalyzed oxidation reactions.

  14. Carbon-13 Labeling Used to Probe Cure and Degradation Reactions of High- Temperature Polymers

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Johnston, J. Christopher

    1998-01-01

    High-temperature, crosslinked polyimides are typically insoluble, intractible materials. Consequently, in these systems it has been difficult to follow high-temperature curing or long-term degradation reactions on a molecular level. Selective labeling of the polymers with carbon-13, coupled with solid nuclear magnetic resonance spectrometry (NMR), enables these reactions to be followed. We successfully employed this technique to provide insight into both curing and degradation reactions of PMR-15, a polymer matrix resin used extensively in aircraft engine applications.

  15. Tailoring the chain packing in ultrathin polyelectrolyte films formed by sequential adsorption: nanoscale probing by positron annihilation spectroscopy.

    PubMed

    Quinn, John F; Pas, Steven J; Quinn, Anthony; Yap, Heng Pho; Suzuki, Ryoichi; Tuomisto, Filip; Shekibi, Bijan S; Mardel, James I; Hill, Anita J; Caruso, Frank

    2012-12-01

    Depth profiling experiments by positron annihilation spectroscopy have been used to investigate the free volume element size and concentration in films assembled using the layer-by-layer (LbL) adsorption method. Films prepared from strong polyelectrolytes, weak polyelectrolytes, hydrogen-bonding polymers, and blended polyelectrolyte multilayers have different chain packing that is reflected in the free volume characteristics. The influence of various parameters on free volume, such as number of bilayers, salt concentration, solution pH, and molecular weight, has been systematically studied. The free volume cavity diameters vary from 4 to 6 Å, and the free volume concentrations vary from (1.1-4.3) × 10(20) cm(-3), depending on the choice of assembly polymers and conditions. Films assembled from strong polyelectrolytes have fewer free volume cavities with a larger average size than films prepared from weak polyelectrolytes. Blending the weak polyanion poly(acrylic acid), PAA, with the strong polyanion poly(styrene sulfonate), PSS, to layer alternately with the polycation poly(allyamine hydrochloride), PAH, is shown to be a viable method to achieve intermediate free volume characteristics in these LbL films. An increase in salt concentration of the adsorption solutions for films prepared from strong polyelectrolytes makes these films tend toward weaker polyelectrolyte free volume characteristics. Hydrogen-bonded layered films show larger free volume element size and concentration than do their electrostatically bonded counterparts, while reducing the molecular weight of these hydrogen-bonded polymers results in slightly reduced free volume size and concentration. A study of the effect of solution pH on films prepared from weak polyelectrolytes shows that when both polyelectrolytes are substantially charged in solution (assembly pH = 7.5), the chains pack similarly to strong polyelectrolytes (i.e., lower free volume concentration), but with smaller average cavity

  16. Modulation of the Foreign Body Reaction for Implants in the Subcutaneous Space: Microdialysis Probes as Localized Drug Delivery/Sampling Devices

    PubMed Central

    Mou, Xiaodun; Lennartz, Michelle R; Loegering, Daniel J; Stenken, Julie A

    2011-01-01

    Modulation of the foreign body reaction is considered to be an important step toward creation of implanted sensors with reliable long-term performance. In this work, microdialysis probes were implanted into the subcutaneous space of Sprague-Dawley rats. The probe performance was evaluated by comparing collected endogenous glucose concentrations with internal standard calibration (2-deoxyglucose, antipyrine, and vitamin B12). Probes were tested until failure, which for this work was defined as loss of fluid flow. In order to determine the effect of fibrous capsule formation on probe function, monocyte chemoattractant protein-1/CC chemokine ligand 2 (MCP-1/CCL2) was delivered locally via the probe to increase capsule thickness and dexamethasone 21-phosphate was delivered to reduce capsule thickness. Probes delivering MCP-1 had a capsule that was twice the thickness (500–600 μm) of control probes (200–225 μm) and typically failed 2 days earlier than control probes. Probes delivering dexamethasone 21-phosphate had more fragile capsules and the probes typically failed 2 days later than controls. Unexpectedly, extraction efficiency and collected glucose concentrations exhibited minor differences between groups. This is an interesting result in that the foreign body capsule formation was related to the duration of probe function but did not consistently relate to probe calibration. PMID:21722577

  17. Fluorescent probes for tracking the transfer of iron-sulfur cluster and other metal cofactors in biosynthetic reaction pathways.

    PubMed

    Vranish, James N; Russell, William K; Yu, Lusa E; Cox, Rachael M; Russell, David H; Barondeau, David P

    2015-01-14

    Iron-sulfur (Fe-S) clusters are protein cofactors that are constructed and delivered to target proteins by elaborate biosynthetic machinery. Mechanistic insights into these processes have been limited by the lack of sensitive probes for tracking Fe-S cluster synthesis and transfer reactions. Here we present fusion protein- and intein-based fluorescent labeling strategies that can probe Fe-S cluster binding. The fluorescence is sensitive to different cluster types ([2Fe-2S] and [4Fe-4S] clusters), ligand environments ([2Fe-2S] clusters on Rieske, ferredoxin (Fdx), and glutaredoxin), and cluster oxidation states. The power of this approach is highlighted with an extreme example in which the kinetics of Fe-S cluster transfer reactions are monitored between two Fdx molecules that have identical Fe-S spectroscopic properties. This exchange reaction between labeled and unlabeled Fdx is catalyzed by dithiothreitol (DTT), a result that was confirmed by mass spectrometry. DTT likely functions in a ligand substitution reaction that generates a [2Fe-2S]-DTT species, which can transfer the cluster to either labeled or unlabeled Fdx. The ability to monitor this challenging cluster exchange reaction indicates that real-time Fe-S cluster incorporation can be tracked for a specific labeled protein in multicomponent assays that include several unlabeled Fe-S binding proteins or other chromophores. Such advanced kinetic experiments are required to untangle the intricate networks of transfer pathways and the factors affecting flux through branch points. High sensitivity and suitability with high-throughput methodology are additional benefits of this approach. We anticipate that this cluster detection methodology will transform the study of Fe-S cluster pathways and potentially other metal cofactor biosynthetic pathways.

  18. Probing the neutron-skin thickness by photon production from reactions induced by intermediate-energy protons

    NASA Astrophysics Data System (ADS)

    Wei, Gao-Feng

    2015-07-01

    The photon from neutron-proton bremsstrahlung in p +Pb reactions is examined as a potential probe of the neutron-skin thickness in different centralities and at different proton incident energies. It is shown that the best choice of reaction environment is about 140 MeV for the incident proton and the 95%-100% centrality for the reaction system since the incident proton mainly interacts with neutrons inside the skin of the target and thus leads to different photon production to a maximal extent. Moreover, considering two main uncertainties from both photon production probability and nucleon-nucleon cross section in the reaction, I propose to use the ratio of photon production from two reactions to measure the neutron-skin thickness because of its cancellation effects on these uncertainties simultaneously, but preserved about 13%-15% sensitivities on the varied neutron-skin thickness from 0.1 to 0.3 fm within the current experimental uncertainty range of the neutron-skin size in 208Pb.

  19. A Partially Fluorinated, Water-Stable Cu(II)-MOF Derived via Transmetalation: Significant Gas Adsorption with High CO2 Selectivity and Catalysis of Biginelli Reactions.

    PubMed

    Pal, Tapan K; De, Dinesh; Senthilkumar, S; Neogi, Subhadip; Bharadwaj, Parimal K

    2016-08-15

    A partially fluorinated, angular tetracarboxylic acid linker (H4L) incorporating a pendant amine moiety forms a three-dimensional Zn(II) framework, 1. The structure consists of paddle-wheel Zn2(CO2)4 secondary building units (SBUs) and Zn12(CO2)24 supramolecular building blocks (SBBs). Thermal stability of 1 is found to be low. However, it undergoes transmetalation reaction with Cu(II) at room temperature without losing crystallinity affording an isostructural framework, 1Cu. Framework 1Cu is thermally robust and allows generation of the solvent-free porous framework 1Cu' upon activation with coordinatively unsaturated metal centers. Framework 1Cu' exhibits water stability and at 77 K, adsorbs 2.56 wt % of H2 up to 1 bar that significantly increases to 4.01 wt % at 13 bar. Also, this framework gives a high adsorption of 164.70 cc/g of CH4 (11.7 wt %) at 303 K and 60 bar. The channel surfaces decorated with -NH2 group and unsaturated metal centers in 1Cu' allow a promising 36.4 wt % of CO2 adsorption at 1 bar and 273 K. Moreover, it exhibits pronounced selectivity of CO2 adsorption over N2 and H2 at 273 K. Finally, the versatility of 1Cu' is shown by its excellent heterogeneous catalytic activity in the Biginelli coupling reactions involving an aldehyde, urea, and ethylacetoacetate to afford dihydroprimidinones. PMID:27459252

  20. Adsorption and oxidation of formaldehyde on a polycrystalline Pt film electrode: An in situ IR spectroscopy search for adsorbed reaction intermediates

    PubMed Central

    Behm, R Jürgen

    2014-01-01

    Summary As part of a mechanistic study of the electrooxidation of C1 molecules we have systematically investigated the dissociative adsorption/oxidation of formaldehyde on a polycrystalline Pt film electrode under experimental conditions optimizing the chance for detecting weakly adsorbed reaction intermediates. Employing in situ IR spectroscopy in an attenuated total reflection configuration (ATR-FTIRS) with p-polarized IR radiation to further improve the signal-to-noise ratio, and using low reaction temperatures (3 °C) and deuterium substitution to slow down the reaction kinetics and to stabilize weakly adsorbed reaction intermediates, we could detect an IR absorption band at 1660 cm−1 characteristic for adsorbed formyl intermediates. This assignment is supported by an isotope shift in wave number. Effects of temperature, potential and deuterium substitution on the formation and disappearance of different adsorbed species (COad, adsorbed formate, adsorbed formyl), are monitored and quantified. Consequences on the mechanism for dissociative adsorption and oxidation of formaldehyde are discussed. PMID:24991512

  1. Reaction-Based Probes for Imaging Mobile Zinc in Live Cells and Tissues

    PubMed Central

    2015-01-01

    Chelatable, or mobile, forms of zinc play critical signaling roles in numerous biological processes. Elucidating the action of mobile Zn(II) in complex biological environments requires sensitive tools for visualizing, tracking, and manipulating Zn(II) ions. A large toolbox of synthetic photoinduced electron transfer (PET)-based fluorescent Zn(II) sensors are available, but the applicability of many of these probes is limited by poor zinc sensitivity and low dynamic ranges owing to proton interference. We present here a general approach for acetylating PET-based probes containing a variety of fluorophores and zinc-binding units. The new sensors provide substantially improved zinc sensitivity and allow for incubation of live cells and tissue slices with nM probe concentrations, a significant improvement compared to the μM concentrations that are typically required for a measurable fluorescence signal. Acetylation effectively reduces or completely quenches background fluorescence in the metal-free sensor. Binding of Zn(II) selectively and quickly mediates hydrolytic cleavage of the acetyl groups, providing a large fluorescence response. An acetylated blue coumarin-based sensor was used to carry out detailed analyses of metal binding and metal-promoted acetyl hydrolysis. Acetylated benzoresorufin-based red-emitting probes with different zinc-binding sites are effective for sensing Zn(II) ions in live cells when applied at low concentrations (∼50–100 nM). We used green diacetylated Zinpyr1 (DA-ZP1) to image endogenous mobile Zn(II) in the molecular layer of mouse dorsal cochlear nucleus (DCN), confirming that acetylation is a suitable approach for preparing sensors that are highly specific and sensitive to mobile zinc in biological systems. PMID:26878065

  2. Metal-Catalyzed Chemical Reaction of Single Molecules Directly Probed by Vibrational Spectroscopy.

    PubMed

    Choi, Han-Kyu; Park, Won-Hwa; Park, Chan-Gyu; Shin, Hyun-Hang; Lee, Kang Sup; Kim, Zee Hwan

    2016-04-01

    The study of heterogeneous catalytic reactions remains a major challenge because it involves a complex network of reaction steps with various intermediates. If the vibrational spectra of individual molecules could be monitored in real time, one could characterize the structures of the intermediates and the time scales of reaction steps without ensemble averaging. Surface-enhanced Raman scattering (SERS) spectroscopy does provide vibrational spectra with single-molecule sensitivity, but typical single-molecule SERS signals exhibit spatial heterogeneities and temporal fluctuations, making them difficult to be used in single-molecule kinetics studies. Here we show that SERS can monitor the single-molecule catalytic reactions in real time. The surface-immobilized reactants placed at the junctions of well-defined nanoparticle-thin film structures produce time-resolved SERS spectra with discrete, step-transitions of photoproducts. We interpret that such SERS-steps correspond to the reaction events of individual molecules occurring at the SERS hotspot. The analyses of the yield, dynamics, and the magnitude of such SERS steps, along with the associated spectral characteristics, fully support our claim. In addition, a model that is based on plasmonic field enhancement and surface photochemistry reproduces the key features of experimental observation. Overall, the result demonstrates that it is possible, under well-controlled conditions, to differentiate the chemical and physical processes contributing to the single-molecule SERS signals, and thus shows the use of single-molecule SERS as a tool for studying the metal-catalyzed organic reactions.

  3. Probing dynamics of fusion reactions through cross-section and spin distribution measurement

    NASA Astrophysics Data System (ADS)

    Kaur, Maninder; Behera, B. R.; Singh, Gulzar; Singh, Varinderjit; Madhavan, N.; Muralithar, S.; Nath, S.; Gehlot, J.; Mohanto, G.; Mukul, Ish; Siwal, D.; Thakur, M.; Kapoor, K.; Sharma, P.; Banerjee, T.; Jhingan, A.; Varughese, T.; Bala, Indu; Nayak, B. K.; Saxena, A.; Chatterjee, M. B.; Stevenson, P. D.

    2016-05-01

    Present work aims to explicate the effect of entrance channel mass asymmetry on fusion dynamics for the Compound Nucleus 80Sr populated through two different channels, 16O+64Zn and 32S+48Ti, using cross-section and spin distribution measurements as probes. The evaporation spectra studies for these systems, reported earlier indicate the presence of dynamical effects for mass symmetric 32S+48Ti system.The CCDEF and TDHF calculations have been performed for both the systems and an attempt has been made to explain the reported deviations in the α-particle spectrum for the mass symmetric system.

  4. Use of an osmium complex as a universal luminescent probe for enzymatic reactions.

    PubMed

    Virel, Ana; Sanchez-Lopez, Jose; Saa, Laura; García, Ana Carla; Pavlov, Valeri

    2009-06-15

    The water-soluble bis(bipyridine)chloro(4-picolinic acid) osmium complex, [Os(III)(bpy)2Cl(PyCOOH)]2+ (bpy=2,2'-bipyridine, Py=pyridine), is fluorescent in aqueous solution, whereas the reduced form of the complex, [Os(II)(bpy)2Cl(PyCOOH)]+, shows no significant fluorescence under the same conditions. Such reversible redox control of the fluorescence of the complex can be easily adapted to follow any enzymatic reaction to yield oxidising or reducing products that are capable of interacting with [Os(III)(bpy)2Cl(PyCOOH)]2+ or [Os(II)(bpy)2Cl(PyCOOH)]+. Based on the redox reaction between products of biocatalytic reactions and the osmium complex, we have designed a simple bioanalytical assay for the detection of nerve gases, alpha-ketoglutarate, hydrogen peroxide and glucose.

  5. Trichloroethene and tetrachloroethene: tropospheric probes for Cl- and Br-atom reactions during the polar sunrise

    NASA Astrophysics Data System (ADS)

    Ariya, P. A.; Catoire, V.; Sander, R.; Niki, H.; Harris, G. W.

    1997-11-01

    We report the results of laboratory and modeling investigations of the atmospheric fate of chlorinated ethenes and their rôle as indicators of halogen reactions in the springtime Arctic troposphere. The kinetics and mechanism of the gas-phase reactions of Cl- and Br-atoms with tetrachloroethene were studied using a Fourier transform infrared spectrometer (FTIR) in 93.3kPa air and T = 296± 2 K. Along with our previous study on Cl and Br atom reactions of trichloroethene, using the known rate of the Cl + ethane reaction as reference, the values of 7.2±0.2×10-11 and 3.8±0.2×10-11 cm3 molecule-1 s-1 were obtained for the Cl-atom reaction rate constants of tri- and tetrachloroethene, respectively. For the Br-atom reactions, using ethene and propane as the reference molecules, we report the absolute values of 1.1±0.1×10-13 and 9.0±0.1×10-17 cm3 molecule-1 s-1 for the rates of Br attack on tri- and tetrachloroethene. The major products were XCl2C-C(O)Cl (X = H in trichloroethene and X = Cl in tetrachloroethene) and XBrClC-C(O)Cl in Cl-atom and Br-atom initiated reactions, respectively. We also observed phosgene and formyl chloride in the reactions of trichloroethene and phosgene in the tetrachloroethene reactions and report the branching ratios for these

  6. A study of the OMVPE growth mechanisms using internal reflectance spectroscopy to examine adsorption of TMGa and NH3 and surface reactions between them

    NASA Astrophysics Data System (ADS)

    Tripathi, A.; Mazzarese, D.; Conner, W. C.; Jones, K. A.

    1989-01-01

    Internal reflection spectroscopy spectra show that NH3 and ND3 chemisorb onto (100) and (111)A GaAs surfaces. Adsorption occurs by the formation of Ga—N bonds via Lewis acid-base reactions which are identified by an absorption band between 1325 and 1100 cm-1 with peaks near 1285, 1220 and 1150 cm-1. No NH3 absorption bands are detected when the (111)B surface is exposed. TMGa also chemisorbs onto the (100) GaAs surface. The adsorption spectra of NH3 + TMGa is a function of the order in which the reactants are introduced. When NH3 is introduced first, the reactivity is much greater as is evidenced by the almost total elimination of absorption peaks associated with N—H and CH3 peaks which suggests that the reactions are surface catalyzed methane elimination reactions. Implications of the requirement that the hydride be adsorbed and the methyls react with the hydrogen atoms from the hydride to ALE and MOMBE growth are discussed. Also, consistent explanations are presented for why growth on the (111)B surface is difficult, the growth rate is independent of the hydride partial pressure under normal growth conditions, the incorporation of C into GaAs has an orientational dependence, and As is more preferentially incorporated into GaAsP at the lower growth temperatures.

  7. Reaction ({gamma},2e) and (e,3e) as probe of electron correlation in atoms

    SciTech Connect

    Amusia, M.Y.

    1995-08-01

    Cross sections of the ({gamma},2e) and (e,3e) reactions contain information about the two vacancy-energy spectrum and electron-pair correlations in initial and final states of the target atom. Physical pictures of these processes are presented for two- and many-electron atoms. The simplest mechanisms are discussed, demonstrating some features which await experimental confirmation. Attention is given to high photon energy and the relativistic energy region of these reactions. The energy distribution of outgoing relativistic electrons is qualitatively different from the nonrelativistic case. The origin and types of corrections to the simplest mechanisms, and possible means of their detection, are discussed. In addition, the role of different resonances: shape, giant, autoionizational, and Feshbach-type are considered. Results of calculations are compared with experimental data, mainly on double photoionization cross sections. Different possible objects as targets for the reactions are considered, including negative ions, excited atoms, molecules, and clusters. The modification of these reactions due to photon emission is discussed. The future of the domain is outlined.

  8. Probing the Rate-Determining Step of the Claisen-Schmidt Condensation by Competition Reactions

    ERIC Educational Resources Information Center

    Mak, Kendrew K. W.; Chan, Wing-Fat; Lung, Ka-Ying; Lam, Wai-Yee; Ng, Weng-Cheong; Lee, Siu-Fung

    2007-01-01

    Competition experiments are a useful tool for preliminary study of the linear free energy relationship of organic reactions. This article describes a physical organic experiment for upper-level undergraduates to identify the rate-determining step of the Claisen-Schmidt condensation of benzaldehyde and acetophenone by studying the linear free…

  9. Detection of untreated mycobacteria by using polymerase chain reaction and specific DNA probes.

    PubMed Central

    Fries, J W; Patel, R J; Piessens, W F; Wirth, D F

    1991-01-01

    A method for specific identification of mycobacteria by using the polymerase chain reaction on organisms taken from liquid cultures, frozen suspensions, or colonies grown on Lowenstein-Jensen slants is presented. This direct detection of mycobacterial organisms has important implications for strain typing and diagnosis. Images PMID:1761699

  10. A computational study on the adsorption configurations and reactions of SiHx(x = 1-4) on clean and H-covered Si(100) surfaces

    NASA Astrophysics Data System (ADS)

    Le, Thong N.-M.; Raghunath, P.; Huynh, Lam K.; Lin, M. C.

    2016-11-01

    Possible adsorption configurations of H and SiHx (x = 1 - 4) on clean and H-covered Si(100) surfaces are determined by using spin-polarized DFT calculations. The results show that, on the clean surface, the gas-phase hydrogen atom and SiH3 radicals effectively adsorb on the top sites, while SiH and SiH2 prefer the bridge sites of the first layer. Another possibility for SiH is to reside on the hollow sites with a triple-bond configuration. For a partially H-coverd Si(100) surface, the mechanism is similar but with higher adsorption energies in most cases. This suggests that the surface species become more stable in the presence of surface hydrogens. The minimum energy paths for the adsorption/migration and reactions of H/SiHx species on the surfaces are explored using the climbing image-nudged elastic band method. The competitive surface processes for Si thin-film formation from SiHx precursors are also predicted. The study reveals that the migration of hydrogen adatom is unimportant with respect to leaving open surface sites because of its high barriers (>29.0 kcal/mol). Alternatively, the abstraction of hydrogen adatoms by H/SiHx radicals is more favorable. Moreover, the removal of hydrogen atoms from adsorbed SiHx, an essential step for forming Si layers, is dominated by abstraction rather than the decomposition processes.

  11. Probing Complex Free-Radical Reaction Pathways of Fuel Model Compounds

    SciTech Connect

    Buchanan III, A C; Kidder, Michelle; Beste, Ariana; Britt, Phillip F

    2012-01-01

    Fossil (e.g. coal) and renewable (e.g. woody biomass) organic energy resources have received considerable attention as possible sources of liquid transportation fuels and commodity chemicals. Knowledge of the reactivity of these complex materials has been advanced through fundamental studies of organic compounds that model constituent substructures. In particular, an improved understanding of thermochemical reaction pathways involving free-radical intermediates has arisen from detailed experimental kinetic studies and, more recently, advanced computational investigations. In this presentation, we will discuss our recent investigations of the fundamental pyrolysis pathways of model compounds that represent key substructures in the lignin component of woody biomass with a focus on molecules representative of the dominant beta-O-4 aryl ether linkages. Additional mechanistic insights gleaned from DFT calculations on the kinetics of key elementary reaction steps will also be presented, as well as a few thoughts on the significant contributions of Jim Franz to this area of free radical chemistry.

  12. Probing the interplay between factors determining reaction rates on silica gel using termolecular systems.

    PubMed

    Kirkpatrick, Iain; Worrall, David R; Williams, Siân L; Buck, Craig J T; Meseguer, Rafael G

    2012-10-01

    In this study we have compared energy and electron transfer reactions in termolecular systems using a nanosecond diffuse reflectance laser flash photolysis technique. We have previously investigated these processes on silica gel surfaces for bimolecular systems and electron transfer in termolecular systems. The latter systems involved electron transfer between three arene molecules with azulene acting as a molecular shuttle. In this study we present an alternative electron transfer system using trans β-carotene as an electron donor in order to effectively immobilise all species except the shuttle, providing the first unambiguous evidence for radical ion mobility. In the energy transfer system we use naphthalene, a structural isomer of azulene, as the shuttle, facilitating energy transfer from a selectively excited benzophenone sensitiser to 9-cyanoanthracene. Bimolecular rate constants for all of these processes have been measured and new insights into the factors determining the rates of these reactions on silica gel have been obtained.

  13. Kinetics of the reaction between H and superheated water probed with muonium

    NASA Astrophysics Data System (ADS)

    Alcorn, Chris D.; Brodovitch, Jean-Claude; Percival, Paul W.; Smith, Marisa; Ghandi, Khashayar

    2014-05-01

    Safe operation of supercritical water-cooled reactors requires knowledge of the kinetics of transient species formed by the radiolysis of water in the range 300-650 °C. Using muonium, it is possible to study aqueous H atom chemistry over this temperature range. An important reaction to study is that of the H atom with water itself, because it is a potential source of molecular H2. The concentration of H2 is important to plant coolant chemistry, as H2 is currently added to suppress oxidative corrosion in CANDU reactors. The reaction of muonium with H2O and D2O was studied experimentally up to 450 °C, and also via quantum chemical computations to investigate possible isotope effects. Our results suggest that although the H atom abstraction from H2O is important at temperatures above 300 °C, the electron-producing channel (H + H2O ⇌ H3O+ + eaq-) is significant at temperatures up to 300 °C, and becomes the dominant reaction channel at lower temperatures.

  14. Probing the Reaction Mechanism of Aluminum/Poly(vinylidene fluoride) Composites.

    PubMed

    DeLisio, Jeffery B; Hu, Xiuli; Wu, Tao; Egan, Garth C; Young, Gregory; Zachariah, Michael R

    2016-06-23

    Energetic thin films with high mass loadings of nanosized components have been recently fabricated using electrospray deposition. These films are composed of aluminum nanoparticles (nAl) homogeneously dispersed in an energetic fluoropolymer binder, poly(vinylidene fluoride) (PVDF). The nascent oxide shell of the nAl has been previously shown to undergo a preignition reaction (PIR) with fluoropolymers such as polytetrafluoroethylene (PTFE). This work examines the PIR between alumina and PVDF to further explain the reaction mechanism of the Al/PVDF system. Temperature jump (T-jump) ignition experiments in air, argon, and vacuum environments showed that the nAl is fluorinated by gas phase species due to a decrease in reactivity in a vacuum. Thermogravimetric analysis coupled with differential scanning calorimetry (TGA/DSC) was used to confirm the occurrence of a PIR, and gas phase products during the PIR and fluorination of nAl were investigated with temperature jump time-of-flight mass spectrometry (T-jump TOFMS). Results show a direct correlation between the amount of alumina in the PVDF film and the relative signal intensity of hydrogen fluoride release (HF). Although the PIR between alumina and PVDF plays an important role in the Al/PVDF reaction mechanism, burn speeds of Al/PVDF films containing additional pure alumina particles showed no burn speed enhancement. PMID:27228361

  15. Short-range plasmonic nanofocusing within submicron regimes facilitates in situ probing and promoting of interfacial reactions

    NASA Astrophysics Data System (ADS)

    Yu, Chen-Chieh; Lin, Keng-Te; Su, Pao-Yun; Wang, En-Yun; Yen, Yu-Ting; Chen, Hsuen-Li

    2016-02-01

    In this study, a simple configuration, based on high-index dielectric nanoparticles (NPs) and plasmonic nanostructures, is employed for the nanofocusing of submicron-short-range surface plasmon polaritons (SPPs). The excited SPPs are locally bound and focused at the interface between the dielectric NPs and the underlying metallic nanostructures, thereby greatly enhancing the local electromagnetic field. Taking advantage of the surface properties of the dielectric NPs, this system performs various functions. For example, the nanofocusing of submicron-short-range SPPs is used to enhance the Raman signals of gas molecules adsorbed on the dielectric NPs. In addition, the presence of the local strong electromagnetic field accelerates the rates of interfacial reactions on the surfaces of the dielectric NPs. Therefore, the proposed nanofocusing configuration can both promote and probe interfacial reactions simultaneously. Herein, the promotion and probing of the desorption of EtOH vapor are described, as well as the photodegradation of methylene blue. Moreover, the nanofocusing of SPPs is demonstrated on an aluminum surface in both the visible and UV regimes, a process that has not been achieved using conventional tapered waveguide nanofocusing structures. Therefore, the nanofocusing of submicron-short-range SPPs by dielectric NPs on plasmonic nanostructures is not limited to low-loss noble metals. Accordingly, this system has potential for use in light management and on-chip green devices and sensors.In this study, a simple configuration, based on high-index dielectric nanoparticles (NPs) and plasmonic nanostructures, is employed for the nanofocusing of submicron-short-range surface plasmon polaritons (SPPs). The excited SPPs are locally bound and focused at the interface between the dielectric NPs and the underlying metallic nanostructures, thereby greatly enhancing the local electromagnetic field. Taking advantage of the surface properties of the dielectric NPs, this

  16. Coke Formation in a Zeolite Crystal During the Methanol-to-Hydrocarbons Reaction as Studied with Atom Probe Tomography.

    PubMed

    Schmidt, Joel E; Poplawsky, Jonathan D; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D A Matthijs; Meirer, Florian; Bare, Simon R; Weckhuysen, Bert M

    2016-09-01

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using (13) C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30-60 (13) C atoms. These clusters correlate with local increases in Brønsted acid site density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. This nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation.

  17. Coke formation in a zeolite crystal during the methanol-to-hydrocarbons reaction as studied with atom probe tomography

    DOE PAGES

    Schmidt, Joel E.; Poplawsky, Jonathan D.; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D. A. Matthijs; Meirer, Florian; Bare, Simon R.; Weckhuysen, Bert M.

    2016-08-03

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using 13C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30–60 13C atoms. These clusters correlate with local increases in Brønsted acid sitemore » density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. Here, this nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation.« less

  18. Coke Formation in a Zeolite Crystal During the Methanol-to-Hydrocarbons Reaction as Studied with Atom Probe Tomography.

    PubMed

    Schmidt, Joel E; Poplawsky, Jonathan D; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D A Matthijs; Meirer, Florian; Bare, Simon R; Weckhuysen, Bert M

    2016-09-01

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using (13) C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30-60 (13) C atoms. These clusters correlate with local increases in Brønsted acid site density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. This nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation. PMID:27485276

  19. TaqMan probe real-time polymerase chain reaction assay for the quantification of canine DNA in chicken nugget.

    PubMed

    Rahman, Md Mahfujur; Hamid, Sharifah Bee Abd; Basirun, Wan Jefrey; Bhassu, Subha; Rashid, Nur Raifana Abdul; Mustafa, Shuhaimi; Mohd Desa, Mohd Nasir; Ali, Md Eaqub

    2016-01-01

    This paper describes a short-amplicon-based TaqMan probe quantitative real-time PCR (qPCR) assay for the quantitative detection of canine meat in chicken nuggets, which are very popular across the world, including Malaysia. The assay targeted a 100-bp fragment of canine cytb gene using a canine-specific primer and TaqMan probe. Specificity against 10 different animals and plants species demonstrated threshold cycles (Ct) of 16.13 ± 0.12 to 16.25 ± 0.23 for canine DNA and negative results for the others in a 40-cycle reaction. The assay was tested for the quantification of up to 0.01% canine meat in deliberately spiked chicken nuggets with 99.7% PCR efficiency and 0.995 correlation coefficient. The analysis of the actual and qPCR predicted values showed a high recovery rate (from 87% ± 28% to 112% ± 19%) with a linear regression close to unity (R(2) = 0.999). Finally, samples of three halal-branded commercial chicken nuggets collected from different Malaysian outlets were screened for canine meat, but no contamination was demonstrated. PMID:26458055

  20. Surface sites on Pt-CeO2 mixed oxide catalysts probed by CO adsorption: a synchrotron radiation photoelectron spectroscopy study.

    PubMed

    Neitzel, Armin; Lykhach, Yaroslava; Skála, Tomáš; Tsud, Nataliya; Vorokhta, Mykhailo; Mazur, Daniel; Prince, Kevin C; Matolín, Vladimír; Libuda, Jörg

    2014-12-01

    By means of synchrotron radiation photoemission spectroscopy, we have investigated Pt-CeO2 mixed oxide films prepared on CeO2(111)/Cu(111). Using CO molecules as a probe, we associate the corresponding surface species with specific surface sites. This allows us to identify the changes in the composition and morphology of Pt-CeO2 mixed oxide films caused by annealing in an ultrahigh vacuum. Specifically, two peaks in C 1s spectra at 289.4 and 291.2 eV, associated with tridentate and bidentate carbonate species, are formed on the nanostructured stoichiometric CeO2 film. The peak at 290.5-291.0 eV in the C 1s spectra indicates the onset of restructuring, i.e. coarsening, of the Pt-CeO2 film. This peak is associated with a carbonate species formed near an oxygen vacancy. The onset of cerium oxide reduction is indicated by the peak at 287.8-288.0 eV associated with carbonite species formed near Ce(3+) cations. The development of surface species on the Pt-CeO2 mixed oxides suggests that restructuring of the films occurs above 300 K irrespective of Pt loadings. We do not find any adsorbed CO species associated with Pt(4+) or Pt(2+). The onset of Pt(2+) reduction is indicated by the peak at 286.9 eV in the C 1s spectra due to CO adsorption on metallic Pt particles. The thermal stability of Pt(2+) in Pt-CeO2 mixed oxide depends on Pt loading. We find excellent stability of Pt(2+) for 12% Pt content in the CeO2 film, whereas at a Pt concentration of 25% in the CeO2 film, a large fraction of the Pt(2+) is converted into metallic Pt particles above 300 K.

  1. Electron transfer in reactions of ketones with organolithium reagents. A carbon-14 kinetic isotope effect probe

    SciTech Connect

    Yamataka, H.; Fujimura, N.; Kawafuji, Y.; Hanafusa, T.

    1987-07-08

    Kinetic isotope effects have been determined for reactions of ketones labeled with carbon-14 at the carbonyl carbon with MeLi and Me/sub 2/CuLi in diethyl ether at 0/sup 0/C. Observed isotope effects were as follows: (C/sub 6/H/sub 5/)/sub 2/C double bonds O + MeLi, /sup 12/k//sup 14/k = 1.000 +/- 0.002; (C/sub 6/H/sub 5/)/sub 2/C double bonds O + Me/sub 2/CuLi, 1.029 +/- 0.005; 2,4,6-Me/sub 3/C/sub 6/H/sub 2/COC/sub 6/H/sub 5/ + MeLi, 1.023 +/- 0.004. The relative reactivities of ortho-, meta-, and para-substituted benzophenones with these reagents were also determined by the competition experiments. These results are consistent with an electron-transfer step which is followed by a carbon-carbon bond-forming step that is or is not rate determining depending on the structure of ketones and reagents. The reaction of benzophenone with MeLi proceeds via rate-determining electron transfer; the change in nucleophile from MeLi to Me/sub 2/CuLi shifts the rate-determining step from electron transfer to recombination; the change in ketone from benzophenone to 2,4,6-trimethylbenzophenone also shifts the rate-determining step from electron transfer to recombination because the latter step becomes slower for the more hindered ketone. The extent of the geometrical change of the substrate at the electron-transfer transition state of the reaction of benzophenone with MeLi was estimated to be small on the basis of the magnitude of the KIE and the rho value of the Hammett correlation.

  2. Simultaneous evaluation of one-electron reducing systems and radical reactions in cells by nitroxyl biradical as probe.

    PubMed

    Araki, Yoko; Koshiishi, Ichiro

    2016-07-01

    In the present study, a novel probe for the simultaneous evaluation of one-electron reducing systems (electron transport chain) and one-electron oxidizing systems (free radical reactions) in cells by electron chemical detection was developed. Six-membered cyclic nitroxyl radicals (2,2,6,6-tetramethylpiperidine-1-oxyl; TEMPO series) are sensitive to one-electron redox systems, generating the hydroxylamine form [TEMPO(H)] via one-electron reduction, and the secondary amine form [TEMPO(N)] via one-electron oxidation in the presence of thiols. In contrast, the sensitivities of five-membered cyclic nitroxyl radicals (2,2,5,5-tetramethylpyrrolidine-1-oxyl; PROXYL series) to the one-electron redox systems are comparatively low. The electron chemical detector can detect 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), TEMPO(H) and PROXYL but not TEMPO(N). Therefore, nitroxyl biradical, TEMPO-PROXYL, as a probe for the evaluation of one-electron redox systems was employed. TEMPO-PROXYL was synthesized by the conjunction of 4-amino-TEMPO with 3-carboxyl-PROXYL via the conventional dicyclohexyl carbodiimide reaction. TEMPO-PROXYL, TEMPO(H)-PROXYL and TEMPO(N)-PROXYL were simultaneously quantified by HPLC with Coularray detection. Calibration curves for the quantification of TEMPO-PROXYL, TEMPO(H)-PROXYL and TEMPO(N)-PROXYL were linear in the range from 80 nm to 80 μm, and the lowest quantification limit of each molecule was estimated to be <80 nm. The relative standard deviations at 0.8 and 80 μm were within 10% (n = 5). Copyright © 2015 John Wiley & Sons, Ltd. PMID:26613564

  3. New prediction model for probe specificity in an allele-specific extension reaction for haplotype-specific extraction (HSE) of Y chromosome mixtures.

    PubMed

    Rothe, Jessica; Watkins, Norman E; Nagy, Marion

    2012-01-01

    Allele-specific extension reactions (ASERs) use 3' terminus-specific primers for the selective extension of completely annealed matches by polymerase. The ability of the polymerase to extend non-specific 3' terminal mismatches leads to a failure of the reaction, a process that is only partly understood and predictable, and often requires time-consuming assay design. In our studies we investigated haplotype-specific extraction (HSE) for the separation of male DNA mixtures. HSE is an ASER and provides the ability to distinguish between diploid chromosomes from one or more individuals. Here, we show that the success of HSE and allele-specific extension depend strongly on the concentration difference between complete match and 3' terminal mismatch. Using the oligonucleotide-modeling platform Visual Omp, we demonstrated the dependency of the discrimination power of the polymerase on match- and mismatch-target hybridization between different probe lengths. Therefore, the probe specificity in HSE could be predicted by performing a relative comparison of different probe designs with their simulated differences between the duplex concentration of target-probe match and mismatches. We tested this new model for probe design in more than 300 HSE reactions with 137 different probes and obtained an accordance of 88%.

  4. Effect of natural organic substances on the surface and adsorptive properties of environmental black carbon (char): pseudo pore blockage by model lipid components and its implications for N2-probed surface properties of natural sorbents.

    PubMed

    Kwon, Seokjoon; Pignatello, Joseph J

    2005-10-15

    Black carbon (BC; char and soot) particles emitted to the environment typically are formed with high microporosity and surface area, properties that are responsible for their presumed important role in adsorption of anthropogenic organic compounds in soils and sediments. An issue that has received little direct attention is the possibility that naturally occurring organic matter attenuates the surface activity of BC. We found that simulated "aging" of prepared wood char particles in a soil-water suspension leads to a strong decline in char total surface area (TSA) by N2 adsorption at 77 K with BET analysis and a more modest decline in affinity for dissolved benzene. To help determine the underlying cause, we measured the effects of adsorbed natural lipids or lipid fractions of humic substances, modeled by triglycerides of a commercial vegetable oil. With increasing lipid loading (up to 40% by char weight) from aqueous mixtures, N2 TSA was strongly suppressed (up to 100-fold), while CO2 cumulative surface area (CSA, 0-1.4 nm) at 273 K and benzene adsorption at 293 K were hardly affected. In addition, the rate of CO2 adsorption was retarded. We propose that externally adsorbed lipid molecules occupy pore throats with access to interior pore networks. At 77 K, as opposed to the higher temperatures, lipid chains are too inflexible to allow passage of adsorbate. It is concluded that benzene adsorption to char predominates at interior pore sites and does not correlate with N2-probed micropore properties when the char accrues pore-blocking substances from the surroundings. The findings question the suitability of N2 for probing hydrophobic microporosity of BC in soils and sediments.

  5. Probing Nonadiabaticity in the Proton-Coupled Electron Transfer Reaction Catalyzed by Soybean Lipoxygenase

    PubMed Central

    2014-01-01

    Proton-coupled electron transfer (PCET) plays a vital role in many biological and chemical processes. PCET rate constant expressions are available for various well-defined regimes, and determining which expression is appropriate for a given system is essential for reliable modeling. Quantitative diagnostics have been devised to characterize the vibronic nonadiabaticity between the electron–proton quantum subsystem and the classical nuclei, as well as the electron–proton nonadiabaticity between the electrons and proton(s) within the quantum subsystem. Herein these diagnostics are applied to a model of the active site of the enzyme soybean lipoxygenase, which catalyzes a PCET reaction that exhibits unusually high deuterium kinetic isotope effects at room temperature. Both semiclassical and electronic charge density diagnostics illustrate vibronic and electron–proton nonadiabaticity for this PCET reaction, supporting the use of the Golden rule nonadiabatic rate constant expression with a specific form of the vibronic coupling. This type of characterization will be useful for theoretical modeling of a broad range of PCET processes. PMID:25258676

  6. Reactions of unsaturated oxygenates on rhodium(111) as probes of multiple coordination of adsorbates

    SciTech Connect

    Brown, N.F.; Barteau, M.A.

    1992-05-20

    The interactions of acrolein, CH{sub 2}=CHCHO, and allyl alcohol, CH{sub 2}=CHCH{sub 2}OH, with the Rh(111) surface are dominated at low temperatures by the oxygen function of each molecule. Acrolein is bound initially in an {eta}{sup 2}(C,O) configuration; allyl alcohol dissociates to form an allyl alkoxide. For both species, vibrational spectra show significant rehybridization of the olefinic groups upon heating to 200 K and suggest that the surface intermediates are {eta}{sup 4}(C,C,CO)-acrolein and {eta}{sup 3} (C,CO)-allyl alkoxide. Both intermediates eliminate CO between 200 and 300 K. However, like that of their aliphatic analogues, decarbonylation of acrolein and allyl alcohol does not proceed via a common pathway. Acrolein decomposes to C{sub 2}H{sub 6}, C{sub 2}H{sub 4}, CO, H{sub 2}, and surface ethylidyne intermediates, but neither allyl alcohol nor any primary alcohol examined on Rh(111) to date produces volatile hydrocarbon products. Thus, although inclusion of the C=C group in the molecules alters the stability of the corresponding surface intermediates, the divergence of reaction pathways for alcohols and aldehydes is unaffected. These results suggest that surface reaction pathways for CO insertion and elimination are considerably more complex than previously recognized. 32 refs., 9 figs., 2 tabs.

  7. F-18 Labeled RGD Probes Based on Bioorthogonal Strain-Promoted Click Reaction for PET Imaging.

    PubMed

    Kim, Hye Lan; Sachin, Kalme; Jeong, Hyeon Jin; Choi, Wonsil; Lee, Hyun Soo; Kim, Dong Wook

    2015-04-01

    A series of fluorine-substituted monomeric and dimeric cRGD peptide derivatives, such as cRGD-ADIBOT-F (ADIBOT = azadibenzocyclooctatriazole), di-cRGD-ADIBOT-F, cRGD-PEG5-ADIBOT-F, and di-cRGD-PEG5-ADIBOT-F, were prepared by strain-promoted alkyne azide cycloaddition (SPAAC) reaction of the corresponding aza-dibenzocyclooctyne (ADIBO) substituted peptides with a fluorinated azide 3. Among these cRGD derivatives, di-cRGD-PEG5-ADIBOT-F had the highest binding affinity in a competitive binding assay compared to other derivatives and even the original cRGDyk. On the basis of the in vitro study results, di-cRGD-PEG5-ADIBOT-(18)F was prepared from a SPAAC reaction with (18)F-labeled azide and subsequent chemo-orthogonal scavenger-assisted separation without high performance liquid chromatography (HPLC) purification in 92% decay-corrected radiochemical yield (dcRCY) with high specific activity for further in vivo positron emission tomography (PET) imaging study. In vivo PET imaging study and biodistribution data showed that this radiotracer allowed successful visualization of tumors with good tumor-to-background contrast and significantly higher tumor uptake compared to other major organs.

  8. Characterization of nanostructured photosensitive (NiS){sub x}(CdS){sub (1-x)} composite thin films grown by successive ionic layer adsorption and reaction (SILAR) route

    SciTech Connect

    Ubale, A.U.; Bargal, A.N.

    2011-07-15

    Highlights: {yields} Thin films of (NiS){sub x}(CdS){sub (1-x)} with variable composition (x = 1 to 0) were deposited onto glass substrates by the successive ionic layer adsorption and reaction (SILAR) method. {yields} The structural, surface morphological and electrical characterizations of the as deposited and annealed films were studied. {yields} The bandgap and activation energy of annealed (NiS){sub x}(CdS){sub (1-x)} film decrease with improvement in photosensitive nature. -- Abstract: Recently ternary semiconductor nanostructured composite materials have attracted the interest of researchers because of their photovoltaic applications. Thin films of (NiS){sub x}(CdS){sub (1-x)} with variable composition (x = 1-0) had been deposited onto glass substrates by the successive ionic layer adsorption and reaction (SILAR) method. As grown and annealed films were characterised by X-ray diffraction, scanning electron microscopy and EDAX to investigate structural and morphological properties. The (NiS){sub x}(CdS){sub (1-x)} films were polycrystalline in nature having mixed phase of rhombohedral and hexagonal crystal structure due to NiS and CdS respectively. The optical and electrical properties of (NiS){sub x}(CdS){sub (1-x)} thin films were studied to determine compsition dependent bandgap, activation energy and photconductivity. The bandgap and activation energy of annealed (NiS){sub x}(CdS){sub (1-x)} film decrease with improvement in photosensitive nature.

  9. Probing Quark-Gluon Structure of Matter with e-p and e-A Reactions

    SciTech Connect

    Jian-Ping Chen

    2011-11-01

    Understanding the strong interaction (QCD) in the truly strong ('non-perturbative') region remains a major challenge in modern physics. Nucleon and nuclei provide natural laboratories to study the strong interaction. The quark-gluon structure of the nucleon and nuclei are important by themselves since they are the main (>99%) part of the visible world. With electroweak interaction well-understood, e-p and e-A are clean means to probe the nucleon and nuclear structure and to study the strong interaction (QCD). Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinally-polarized parton (quark and gluon) distributions (PDFs). It has becoming clear that transverse spin and transverse structure (both transverse spatial structure via generalized parton distributions (GPDs) and transverse momentum structure via transverse- momentum-dependent distributions (TMDs)) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction(QCD). The transverse spin, GPDs and TMDs have been the subjects of increasingly intense theoretical and experimental study recently. With 12 GeV energy upgrade, Jefferson Lab (JLab) will provide the most precise multi-dimensional map of the TMDs and GPDs in the valence quark region through Semi-Inclusive DIS (SIDIS) and Deep-Exclusive experiments, providing a 3-d partonic picture of the nucleon in momentum and spatial spaces. The precision information on TMDs and GPDs will provide access to the quark orbital angular momentum and its correlation with the quark and the nucleon spins. The planned future Electron-Ion Collider (EIC) will enable a precision study of the TMDs and GPDs of the sea quarks and gluons, in addition to completing the study in the valence region. The EIC will also open a new window to study the role of gluons in nuclei.

  10. Microfluidic technology platforms for synthesizing, labeling and measuring the kinetics of transport and biochemical reactions for developing molecular imaging probes

    SciTech Connect

    Phelps, Michael E.

    2009-09-01

    Radiotracer techniques are used in environmental sciences, geology, biology and medicine. Radiotracers with Positron Emission Tomography (PET) provided biological examinations of ~3 million patients 2008. Despite the success of positron labeled tracers in many sciences, there is limited access in an affordable and convenient manner to develop and use new tracers. Integrated microfluidic chips are a new technology well matched to the concentrations of tracers. Our goal is to develop microfluidic chips and new synthesis approaches to enable wide dissemination of diverse types of tracers at low cost, and to produce new generations of radiochemists for which there are many unfilled jobs. The program objectives are to: 1. Develop an integrated microfluidic platform technology for synthesizing and 18F-labeling diverse arrays of different classes of molecules. 2. Incorporate microfluidic chips into small PC controlled devices (“Synthesizer”) with a platform interfaced to PC for electronic and fluid input/out control. 3. Establish a de-centralized model with Synthesizers for discovering and producing molecular imaging probes, only requiring delivery of inexpensive [18F]fluoride ion from commercial PET radiopharmacies vs the centralized approach of cyclotron facilities synthesizing and shipping a few different types of 18F-probes. 4. Develop a position sensitive avalanche photo diode (PSAPD) camera for beta particles embedded in a microfluidic chip for imaging and measuring transport and biochemical reaction rates to valid new 18F-labeled probes in an array of cell cultures. These objectives are met within a research and educational program integrating radio-chemistry, synthetic chemistry, biochemistry, engineering and biology in the Crump Institute for Molecular Imaging. The Radiochemistry Training Program exposes PhD and post doctoral students to molecular imaging in vitro in cells and microorganisms in microfluidic chips and in vivo with PET, from new technologies

  11. Styrene oligomerization as a molecular probe reaction for Brønsted acidity at the nanoscale.

    PubMed

    Aramburo, Luis R; Wirick, Sue; Miedema, Piter S; Buurmans, Inge L C; de Groot, Frank M F; Weckhuysen, Bert M

    2012-05-21

    The Brønsted acid-catalyzed oligomerization of 4-fluorostyrene has been studied on a series of H-ZSM-5 zeolite powders, steamed under different conditions, with a combination of UV-Vis micro-spectroscopy and Scanning Transmission X-ray Microscopy (STXM). UV-Vis micro-spectroscopy and STXM have been used to monitor the relative formation of cyclic and linear dimeric carbocations as a function of the steaming post-treatment (i.e., parent vs. steaming at 600, 700 and 800 °C). It was found that the UV-Vis band intensity ratios of linear to cyclic dimeric species increase from 0.79 (parent H-ZSM-5) over 1.41 (H-ZSM-5 steamed at 600 °C) and 1.88 (H-ZSM-5 steamed at 700 °C) to 2.33 (H-ZSM-5 steamed at 800 °C). STXM confirms this trend in reaction product selectivity, as the relative intensities of the transitions attributed to the presence of the cyclic dimer in the carbon K-edge spectra decrease with increasing severity of the steaming post-treatment. Furthermore, STXM reveals spatial heterogeneities in reaction product formation within the H-ZSM-5 zeolite powders at the nanoscale. More specifically, a shrinking carbon core-shell distribution was detected within the zeolite aggregates, in which the relative amount of cyclic dimeric species is higher in the core relative to the shell of the zeolite aggregate and the relative amount of cyclic dimeric species in the zeolite core gradually decreases with increasing severity of the steaming post-treatment. These differences are rationalized in terms of spatial differences in Brønsted acidity within H-ZSM-5 zeolite powders as well as by changes in the formation process of linear and dimeric carbocations within H-ZSM-5 micro- and mesopores.

  12. Probing the reaction mechanism of IspH protein by x-ray structure analysis

    PubMed Central

    Gräwert, Tobias; Span, Ingrid; Eisenreich, Wolfgang; Rohdich, Felix; Eppinger, Jörg; Bacher, Adelbert; Groll, Michael

    2010-01-01

    Isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) represent the two central intermediates in the biosynthesis of isoprenoids. The recently discovered deoxyxylulose 5-phosphate pathway generates a mixture of IPP and DMAPP in its final step by reductive dehydroxylation of 1-hydroxy-2-methyl-2-butenyl 4-diphosphate. This conversion is catalyzed by IspH protein comprising a central iron-sulfur cluster as electron transfer cofactor in the active site. The five crystal structures of IspH in complex with substrate, converted substrate, products and PPi reported in this article provide unique insights into the mechanism of this enzyme. While IspH protein crystallizes with substrate bound to a [4Fe-4S] cluster, crystals of IspH in complex with IPP, DMAPP or inorganic pyrophosphate feature [3Fe-4S] clusters. The IspH:substrate complex reveals a hairpin conformation of the ligand with the C(1) hydroxyl group coordinated to the unique site in a [4Fe-4S] cluster of aconitase type. The resulting alkoxide complex is coupled to a hydrogen-bonding network, which serves as proton reservoir via a Thr167 proton relay. Prolonged x-ray irradiation leads to cleavage of the C(1)-O bond (initiated by reducing photo electrons). The data suggest a reaction mechanism involving a combination of Lewis-acid activation and proton coupled electron transfer. The resulting allyl radical intermediate can acquire a second electron via the iron-sulfur cluster. The reaction may be terminated by the transfer of a proton from the β-phosphate of the substrate to C(1) (affording DMAPP) or C(3) (affording IPP). PMID:20080550

  13. Probing a chemical compass: novel variants of low-frequency reaction yield detected magnetic resonance.

    PubMed

    Maeda, Kiminori; Storey, Jonathan G; Liddell, Paul A; Gust, Devens; Hore, P J; Wedge, C J; Timmel, Christiane R

    2015-02-01

    We present a study of a carotenoid-porphyrin-fullerene triad previously shown to function as a chemical compass: the photogenerated carotenoid-fullerene radical pair recombines at a rate sensitive to the orientation of an applied magnetic field. To characterize the system we develop a time-resolved Low-Frequency Reaction Yield Detected Magnetic Resonance (tr-LF-RYDMR) technique; the effect of varying the relative orientation of applied static and 36 MHz oscillating magnetic fields is shown to be strongly dependent on the strength of the oscillating magnetic field. RYDMR is a diagnostic test for involvement of the radical pair mechanism in the magnetic field sensitivity of reaction rates or yields, and has previously been applied in animal behavioural experiments to verify the involvement of radical-pair-based intermediates in the magnetic compass sense of migratory birds. The spectroscopic selection rules governing RYDMR are well understood at microwave frequencies for which the so-called 'high-field approximation' is valid, but at lower frequencies different models are required. For example, the breakdown of the rotating frame approximation has recently been investigated, but less attention has so far been given to orientation effects. Here we gain physical insights into the interplay of the different magnetic interactions affecting low-frequency RYDMR experiments performed in the challenging regime in which static and oscillating applied magnetic fields as well as internal electron-nuclear hyperfine interactions are of comparable magnitude. Our observations aid the interpretation of existing RYDMR-based animal behavioural studies and will inform future applications of the technique to verify and characterize further the biological receptors involved in avian magnetoreception. PMID:25537133

  14. Probing a chemical compass: novel variants of low-frequency reaction yield detected magnetic resonance.

    PubMed

    Maeda, Kiminori; Storey, Jonathan G; Liddell, Paul A; Gust, Devens; Hore, P J; Wedge, C J; Timmel, Christiane R

    2015-02-01

    We present a study of a carotenoid-porphyrin-fullerene triad previously shown to function as a chemical compass: the photogenerated carotenoid-fullerene radical pair recombines at a rate sensitive to the orientation of an applied magnetic field. To characterize the system we develop a time-resolved Low-Frequency Reaction Yield Detected Magnetic Resonance (tr-LF-RYDMR) technique; the effect of varying the relative orientation of applied static and 36 MHz oscillating magnetic fields is shown to be strongly dependent on the strength of the oscillating magnetic field. RYDMR is a diagnostic test for involvement of the radical pair mechanism in the magnetic field sensitivity of reaction rates or yields, and has previously been applied in animal behavioural experiments to verify the involvement of radical-pair-based intermediates in the magnetic compass sense of migratory birds. The spectroscopic selection rules governing RYDMR are well understood at microwave frequencies for which the so-called 'high-field approximation' is valid, but at lower frequencies different models are required. For example, the breakdown of the rotating frame approximation has recently been investigated, but less attention has so far been given to orientation effects. Here we gain physical insights into the interplay of the different magnetic interactions affecting low-frequency RYDMR experiments performed in the challenging regime in which static and oscillating applied magnetic fields as well as internal electron-nuclear hyperfine interactions are of comparable magnitude. Our observations aid the interpretation of existing RYDMR-based animal behavioural studies and will inform future applications of the technique to verify and characterize further the biological receptors involved in avian magnetoreception.

  15. Probing the Additional Capacity and Reaction Mechanism of the RuO2 Anode in Lithium Rechargeable Batteries.

    PubMed

    Kim, Yunok; Muhammad, Shoaib; Kim, Hyunchul; Cho, Yong-Hun; Kim, Hansu; Kim, Ji Man; Yoon, Won-Sub

    2015-07-20

    The structural changes and electrochemical behavior of RuO2 are investigated by using in situ XRD, X-ray absorption spectroscopy, and electrochemical techniques to understand the electrochemical reaction mechanism of this metal oxide anode material. Intermediate phase-assisted transformation of RuO2 to LiRuO2 takes place at the start of discharge. Upon further lithiation, LiRuO2 formed by intercalation decomposes to nanosized Ru metal and Li2 O by a conversion reaction. A reversible capacity in addition to its theoretical capacity is observed on discharging below 0.5 V during which no redox activity involving Ru is observed. TEM, X-ray photoelectron spectroscopy, and the galvanostatic intermittent titration technique are used to probe this additional capacity. The results show that the additional capacity is a result of Li storage in the grain boundary between nanosized Ru metal and Li2 O. Findings of this study provide a better understanding of the quantitative share of capacity by a unique combination of intercalation, conversion, and interfacial Li storage in a RuO2 anode.

  16. Developing Activity Localization Fluorescence Peptide Probe Using Thiol-Ene Click Reaction for Spatially Resolved Imaging of Caspase-8 in Live Cells.

    PubMed

    Liu, Wei; Liu, Si-Jia; Kuang, Yong-Qing; Luo, Feng-Yan; Jiang, Jian-Hui

    2016-08-01

    Small molecule probes suitable for high-resolution fluorescence imaging of enzyme activity pose a challenge in chemical biology. We developed a novel design of activity localization fluorescence (ALF) peptide probe, which enables spatially resolved, highly sensitive imaging of peptidase in live cells. The ALF probe was synthesized by a facile thiol-ene click reaction of a cysteine-appended peptide with an acryloylated fluorophore. Upon cleavage by peptidase, the probe undergoes a seven-membered intramolecular cyclization and releases the fluorophore with the excited-state intramolecular photon transfer (ESIPT) effect. A highly fluorescent, insoluble aggregate was formed around the enzyme, which facilitates high-sensitivity and high-resolution imaging. This design is demonstrated for detection of caspase-8 activation. The results show that our design allows easy, high-yield synthesis of the probe, and the probe affords high sensitivity for caspase-8 detection. Live cell imaging reveals that the probe is able to render highly localized and high-contrast fluorescence signal for caspase-8. Our design holds the potential as a generally applicable strategy for developing high-sensitivity and high-resolution imaging peptide probes in cell biology and diagnostics. PMID:27388162

  17. Hybrid adsorptive membrane reactor

    NASA Technical Reports Server (NTRS)

    Tsotsis, Theodore T. (Inventor); Sahimi, Muhammad (Inventor); Fayyaz-Najafi, Babak (Inventor); Harale, Aadesh (Inventor); Park, Byoung-Gi (Inventor); Liu, Paul K. T. (Inventor)

    2011-01-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  18. Hybrid adsorptive membrane reactor

    DOEpatents

    Tsotsis, Theodore T.; Sahimi, Muhammad; Fayyaz-Najafi, Babak; Harale, Aadesh; Park, Byoung-Gi; Liu, Paul K. T.

    2011-03-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  19. Passivation Layer and Cathodic Redox Reactions in Sodium-Ion Batteries Probed by HAXPES.

    PubMed

    Doubaji, Siham; Philippe, Bertrand; Saadoune, Ismael; Gorgoi, Mihaela; Gustafsson, Torbjorn; Solhy, Abderrahim; Valvo, Mario; Rensmo, Håkan; Edström, Kristina

    2016-01-01

    The cathode material P2-Nax Co2/3 Mn2/9 Ni1/9 O2, which could be used in Na-ion batteries, was investigated through synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). Nondestructive analysis was made through the electrode/electrolyte interface of the first electrochemical cycle to ensure access to information not only on the active material, but also on the passivation layer formed at the electrode surface and referred to as the solid permeable interface (SPI). This investigation clearly shows the role of the SPI and the complexity of the redox reactions. Cobalt, nickel, and manganese are all electrochemically active upon cycling between 4.5 and 2.0 V; all are in the 4+ state at the end of charging. Reduction to Co(3+), Ni(3+), and Mn(3+) occurs upon discharging and, at low potential, there is partial reversible reduction to Co(2+) and Ni(2+). A thin layer of Na2 CO3 and NaF covers the pristine electrode and reversible dissolution/reformation of these compounds is observed during the first cycle. The salt degradation products in the SPI show a dependence on potential. Phosphates mainly form at the end of the charging cycle (4.5 V), whereas fluorophosphates are produced at the end of discharging (2.0 V).

  20. Femtosecond real-time probing of reactions. IX. Hydrogen-atom transfer

    NASA Astrophysics Data System (ADS)

    Herek, J. L.; Pedersen, S.; Bañares, L.; Zewail, A. H.

    1992-12-01

    The real-time dynamics of hydrogen-atom-transfer processes under collisionless conditions are studied using femtosecond depletion techniques. The experiments focus on the methyl salicylate system, which exhibits ultrafast hydrogen motion between two oxygen atoms due to molecular tautomerization, loosely referred to as intramolecular ``proton'' transfer. To test for tunneling and mass effects on the excited potential surface, we also studied deuterium and methyl-group substitutions. We observe that the motion of the hydrogen, under collisionless conditions, takes place within 60 fs. At longer times, on the picosecond time scale, the hydrogen-transferred form decays with a threshold of 15.5 kJ/mol; this decay behavior was observed up to a total vibrational energy of ˜7200 cm-1. The observed dynamics provide the global nature of the motion, which takes into account bonding before and after the motion, and the evolution of the wave packet from the initial nonequilibrium state to the transferred form along the O-H—O reaction coordinate. The vibrational periods (2π/ω) of the relevant modes range from 13 fs (the OH stretch) to 190 fs (the low-frequency distortion) and the motion involves (in part) these coordinates. The intramolecular vibrational-energy redistribution dynamics at longer times are important to the hydrogen-bond dissociation and to the nonradiative decay of the hydrogen-transferred form.

  1. The ({sup 18}O, {sup 16}O) reaction as a probe for nuclear spectroscopy

    SciTech Connect

    Cappuzzello, F.; Bondì, M.; Nicolosi, D.; Tropea, S.; Agodi, A.; Carbone, D.; Cavallaro, M.; Cunsolo, A.; Borello-Lewin, T.; Rodrigues, M. R. D.; De Napoli, M.; Linares, R.

    2014-11-11

    The response of nuclei to the ({sup 18}O, {sup 16}O) two-neutron transfer reaction at 84 MeV incident energy has been systematically studied at the Catania INFN-LNS laboratory. The experiments were performed using several solid targets from light ({sup 9}Be, {sup 11}B, {sup 12,13}C, {sup 16}O, {sup 28}Si) to heavy ones ({sup 58,64}Ni, {sup 120}Sn, {sup 208}Pb). The {sup 16}O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer. Exploiting the large momentum acceptance (−10%, +14%) and solid angle (50 msr) of the spectrometer, energy spectra were obtained with a relevant yield up to about 20 MeV excitation energy. The application of the powerful trajectory reconstruction technique did allow to get energy spectra with energy resolution of about 150 keV and angular distributions with angular resolution better than 0.3°. A common feature observed with light nuclei is the appearance of unknown resonant structures at high excitation energy. The strong population of these latter together with the measured width can reveal the excitation of a collective mode connected with the transfer of a pair.

  2. 40 CFR Appendix E to Part 58 - Probe and Monitoring Path Siting Criteria for Ambient Air Quality Monitoring

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... capture rate. (d) For near-road NO2 monitoring stations, the monitor probe shall have an unobstructed air...) Trees can provide surfaces for SO2, O3, or NO2 adsorption or reactions, and surfaces for particle... desorption reactions on the FEP Teflon ®. Borosilicate glass, stainless steel, or its equivalent are...

  3. 40 CFR Appendix E to Part 58 - Probe and Monitoring Path Siting Criteria for Ambient Air Quality Monitoring

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... capture rate. (d) For near-road NO2 monitoring stations, the monitor probe shall have an unobstructed air...) Trees can provide surfaces for SO2, O3, or NO2 adsorption or reactions, and surfaces for particle... desorption reactions on the FEP Teflon®. Borosilicate glass, stainless steel, or its equivalent are...

  4. Impedance spectroscopy and conductometric biosensing for probing catalase reaction with cyanide as ligand and inhibitor.

    PubMed

    Bouyahia, Naima; Hamlaoui, Mohamed Larbi; Hnaien, Mouna; Lagarde, Florence; Jaffrezic-Renault, Nicole

    2011-02-01

    In this work, a new biosensor was prepared through immobilization of bovine liver catalase in a photoreticulated poly (vinyl alcohol) membrane at the surface of a conductometric transducer. This biosensor was used to study the kinetics of catalase-H(2)0(2) reaction and its inhibition by cyanide. Immobilized catalase exhibited a Michaelis-Menten behaviour at low H(2)0(2) concentrations (<100mM) with apparent constant K(M)(app)=84±3mM and maximal initial velocity V(M)(app)=13.4μS min(-1). Inhibition by cyanide was found to be non-competitive and inhibition binding constant K(i) was 13.9±0.3μM. The decrease of the biosensor response by increasing cyanide concentration was linear up to 50μM, with a cyanide detection limit of 6μM. In parallel, electrochemical characteristics of the catalase/PVA biomembrane and its interaction with cyanide were studied by cyclic voltammetry and impedance spectroscopy. Addition of the biomembrane onto the gold electrodes induced a significant increase of the interfacial polarization resistance R(P). On the contrary, cyanide binding resulted in a decrease of Rp proportional to KCN concentration in the 4 to 50μM range. Inhibition coefficient I(50) calculated by this powerful label-free and substrate-free technique (24.3μM) was in good agreement with that determined from the substrate-dependent conductometric biosensor (24.9μM).

  5. Impedance spectroscopy and conductometric biosensing for probing catalase reaction with cyanide as ligand and inhibitor.

    PubMed

    Bouyahia, Naima; Hamlaoui, Mohamed Larbi; Hnaien, Mouna; Lagarde, Florence; Jaffrezic-Renault, Nicole

    2011-02-01

    In this work, a new biosensor was prepared through immobilization of bovine liver catalase in a photoreticulated poly (vinyl alcohol) membrane at the surface of a conductometric transducer. This biosensor was used to study the kinetics of catalase-H(2)0(2) reaction and its inhibition by cyanide. Immobilized catalase exhibited a Michaelis-Menten behaviour at low H(2)0(2) concentrations (<100mM) with apparent constant K(M)(app)=84±3mM and maximal initial velocity V(M)(app)=13.4μS min(-1). Inhibition by cyanide was found to be non-competitive and inhibition binding constant K(i) was 13.9±0.3μM. The decrease of the biosensor response by increasing cyanide concentration was linear up to 50μM, with a cyanide detection limit of 6μM. In parallel, electrochemical characteristics of the catalase/PVA biomembrane and its interaction with cyanide were studied by cyclic voltammetry and impedance spectroscopy. Addition of the biomembrane onto the gold electrodes induced a significant increase of the interfacial polarization resistance R(P). On the contrary, cyanide binding resulted in a decrease of Rp proportional to KCN concentration in the 4 to 50μM range. Inhibition coefficient I(50) calculated by this powerful label-free and substrate-free technique (24.3μM) was in good agreement with that determined from the substrate-dependent conductometric biosensor (24.9μM). PMID:20813591

  6. Hydrogen Surface Reactions and Adsorption Studied on Y2O3, YSZ, and ZrO2

    PubMed Central

    2014-01-01

    The surface reactivity of Y2O3, YSZ, and ZrO2 polycrystalline powder samples toward H2 has been comparatively studied by a pool of complementary experimental techniques, comprising volumetric methods (temperature-programmed volumetric adsorption/oxidation and thermal desorption spectrometry), spectroscopic techniques (in situ electric impedance and in situ Fourier-transform infrared spectroscopy), and eventually structural characterization methods (X-ray diffraction and scanning electron microscopy). Reduction has been observed on all three oxides to most likely follow a surface or near-surface-limited mechanism involving removal of surface OH-groups and associated formation of water without formation of a significant number of anionic oxygen vacancies. Partly reversible adsorption of H2 was proven on the basis of molecular H2 desorption. Dictated by the specific hydrophilicity of the oxide, readsorption of water eventually takes place. The inference of this surface-restricted mechanism is further corroborated by the fact that no bulk structural and/or morphological changes were observed upon reduction even at the highest reduction temperatures (1173 K). We anticipate relevant implications for the use of especially YSZ in fuel cell research, since in particular the chemical state and structure of the surface under typical reducing high-temperature conditions affects the operation of the entire cell. PMID:24791182

  7. Hydrogen Surface Reactions and Adsorption Studied on Y2O3, YSZ, and ZrO2.

    PubMed

    Kogler, Michaela; Köck, Eva-Maria; Bielz, Thomas; Pfaller, Kristian; Klötzer, Bernhard; Schmidmair, Daniela; Perfler, Lukas; Penner, Simon

    2014-04-24

    The surface reactivity of Y2O3, YSZ, and ZrO2 polycrystalline powder samples toward H2 has been comparatively studied by a pool of complementary experimental techniques, comprising volumetric methods (temperature-programmed volumetric adsorption/oxidation and thermal desorption spectrometry), spectroscopic techniques (in situ electric impedance and in situ Fourier-transform infrared spectroscopy), and eventually structural characterization methods (X-ray diffraction and scanning electron microscopy). Reduction has been observed on all three oxides to most likely follow a surface or near-surface-limited mechanism involving removal of surface OH-groups and associated formation of water without formation of a significant number of anionic oxygen vacancies. Partly reversible adsorption of H2 was proven on the basis of molecular H2 desorption. Dictated by the specific hydrophilicity of the oxide, readsorption of water eventually takes place. The inference of this surface-restricted mechanism is further corroborated by the fact that no bulk structural and/or morphological changes were observed upon reduction even at the highest reduction temperatures (1173 K). We anticipate relevant implications for the use of especially YSZ in fuel cell research, since in particular the chemical state and structure of the surface under typical reducing high-temperature conditions affects the operation of the entire cell.

  8. The distinct effects of Mn substitution on the reactivity of magnetite in heterogeneous Fenton reaction and Pb(II) adsorption.

    PubMed

    Liang, Xiaoliang; He, Zisen; Wei, Gaoling; Liu, Peng; Zhong, Yuanhong; Tan, Wei; Du, Peixin; Zhu, Jianxi; He, Hongping; Zhang, Jing

    2014-07-15

    In this study, a series of Mn substituted magnetites were synthesized and used in catalyzing the heterogeneous Fenton degradation of acid orange II and Pb(II) adsorption, in order to investigate the effect of Mn substitution on the reactivity of magnetite. The valence and local environment of both Fe and Mn in the spinel structure of magnetite were investigated by X-ray absorption fine structure (XAFS) spectroscopy. The incorporation of Mn did not change the valence and local structure of Fe in the synthetic magnetite, while Mn was in the valences of +2 and +3. The Mn distribution on the octahedral sites of magnetite surface increased with the increase in Mn content. The Mn introduction led to an improvement of catalytic activity of magnetite. The sample with the minimum Mn content displayed the best efficiency in OH production and the degradation of acid orange II, while the other substituted samples did not show obvious difference in their catalytic performance. The adsorption capacity of magnetite samples toward Pb(II) gradually increased with the increase in Mn content. The above influences of Mn substitution on the reactivity of magnetite were discussed in views of the variations in microstructural environment and physicochemical properties.

  9. Modification of 1,2,4,5-tetrazine with cationic rhenium(I) polypyridine units to afford phosphorogenic bioorthogonal probes with enhanced reaction kinetics.

    PubMed

    Choi, Alex Wing-Tat; Tso, Karson Ka-Shun; Yim, Vicki Man-Wai; Liu, Hua-Wei; Lo, Kenneth Kam-Wing

    2015-02-25

    New phosphorogenic bioorthogonal probes derived from mononuclear and binuclear rhenium(I) polypyridine complexes containing a 1,2,4,5-tetrazine moiety were designed; these complexes displayed substantial dienophile-induced emission enhancement, and accelerated reaction kinetics and could target a protein conjugate in living cells.

  10. A simple naphthalene-based fluorescent probe for high selective detection of formaldehyde in toffees and HeLa cells via aza-Cope reaction.

    PubMed

    Xu, Junchao; Zhang, Yue; Zeng, Lintao; Liu, Jinbiao; Kinsella, Joseph M; Sheng, Ruilong

    2016-11-01

    A simple naphthalene-based fluorescent probe (AENO) for formaldehyde (FA) was successfully synthesized, which exhibited a significant fluorescence turn-on response towards FA in aqueous solution. The probe could quantitatively determine the concentration of FA (0-1.0mM) with excellent selectivity, high sensitivity and low limit of detection (0.57µM). The sensing mechanism was proposed as 2-aza-Cope rearrangement for AENO after reaction with FA, which was confirmed by (1)H NMR, HR-MS, FT-IR, UV-vis and fluorescence spectra. The probe has been employed to determine the FA contents in several commercially available toffee samples with satisfactory performance. Thus, AENO might be used as a promising tool for quantitative detection of FA in food. Furthermore, fluorescence imaging of HeLa cells indicated that the probe was cell membrane permeable and could be used for visualizing/imaging the FA trace/transportation in cancer cells.

  11. Theoretical and Experimental Investigation of Thermodynamics and Kinetics of Thiol-Michael Addition Reactions: A Case Study of Reversible Fluorescent Probes for Glutathione Imaging in Single Cells.

    PubMed

    Chen, Jianwei; Jiang, Xiqian; Carroll, Shaina L; Huang, Jia; Wang, Jin

    2015-12-18

    Density functional theory (DFT) was applied to study the thermodynamics and kinetics of reversible thiol-Michael addition reactions. M06-2X/6-31G(d) with the SMD solvation model can reliably predict the Gibbs free energy changes (ΔG) of thiol-Michael addition reactions with an error of less than 1 kcal·mol(-1) compared with the experimental benchmarks. Taking advantage of this computational model, the first reversible reaction-based fluorescent probe was developed that can monitor the changes in glutathione levels in single living cells.

  12. Adsorption, Coadsorption, and Reaction of Acetaldehyde and NO2 on Na-Y,FAU: An In Situ FTIR Investigation

    SciTech Connect

    János, Szanyi; Ja Hun, Kwak; Ryan A.,Moline; Charles H. F.,Peden

    2004-11-01

    The adsorption of acetaldehyde and its coadsorption and reaction with NO2 were investigated on a Na-Y,FAU zeolite using in situ FTIR spectroscopy. Acetaldehyde adsorbs strongly over Na-Y and desorbs molecularly at around 400 K with very limited extent of condensation or polymerization. Reaction between CH3CHO and NO2 takes place in coadsorption experiments even at 300 K. In the initial step, acetaldehyde is oxidized to acetic acid accompanied by the formation of NO, which can be observed as N2O3 formed via a further reaction between NO and NO2. The key intermediates in the overall NOx reduction in this process are nitromethane and, possibly, nitrosomethane, which form in the next step. Their decomposition and further reaction with adsorbed NOx species lead to the formation of HCN, HNCO, N2O, CO2, and organic nitrile species identified by their characteristic IR vibrational signatures. At 473 K, the reaction between adsorbed CH3CHO and NO2 is very fast. The results seem to suggest a mechanism in which N-N bond formation takes place among ionic nitrogen containing species (NO+ and CN- or NCO-). Finally, no evidence has been found to suggest the participation of NHx+NOy- type species in the N-N bond formation under the experimental conditions of this study, although their role in the overall N2 formation process cannot be ruled out under realistic catalytic conditions.

  13. A novel near-infrared fluorescent platform with good photostability and the application for a reaction-based Cu(2+) probe in living cells.

    PubMed

    Liu, Keyin; Shang, Huiming; Meng, Fangfang; Liu, Yong; Lin, Weiying

    2016-01-15

    Most of the near-infrared (NIR) fluorescent copper ion probes are coordination-based, and the fluorescence enhancement is between 10 and 20 folds. Herein, a novel NIR fluorescent dye named CSCN with excellent photostability and a reaction-based Cu(2+) NIR probe named CSCN-Cu were reported. CSCN exhibited good photostability toward photo irradiation. CSCN-Cu showed lower background fluorescent interference and over 40-fold fluorescence enhancement in NIR region, it also exhibited good selectivity toward Cu(2+) in Hepes solution. Biotic experiments demonstrated that CSCN-Cu possessed low toxicity and successfully imaged Cu(2+) in living cells under the conditions performed. PMID:26592595

  14. Identification of human rotavirus serotype by hybridization to polymerase chain reaction-generated probes derived from a hyperdivergent region of the gene encoding outer capsid protein VP7

    SciTech Connect

    Flores, J.; Sears, J.; Schael, I.P.; White, L.; Garcia, D.; Lanata, C.; Kapikian, A.Z. )

    1990-08-01

    We have synthesized {sup 32}P-labeled hybridization probes from a hyperdivergent region (nucleotides 51 to 392) of the rotavirus gene encoding the VP7 glycoprotein by using the polymerase chain reaction method. Both RNA (after an initial reverse transcription step) and cloned cDNA from human rotavirus serotypes 1 through 4 could be used as templates to amplify this region. High-stringency hybridization of each of the four probes to rotavirus RNAs dotted on nylon membranes allowed the specific detection of corresponding sequences and thus permitted identification of the serotype of the strains dotted. The procedure was useful when applied to rotaviruses isolated from field studies.

  15. Enhanced Colloidal Stability of CeO2 Nanoparticles by Ferrous Ions: Adsorption, Redox Reaction, and Surface Precipitation.

    PubMed

    Liu, Xuyang; Ray, Jessica R; Neil, Chelsea W; Li, Qingyun; Jun, Young-Shin

    2015-05-01

    Due to the toxicity of cerium oxide (CeO2) nanoparticles (NPs), a better understanding of the redox reaction-induced surface property changes of CeO2 NPs and their transport in natural and engineered aqueous systems is needed. This study investigates the impact of redox reactions with ferrous ions (Fe2+) on the colloidal stability of CeO2 NPs. We demonstrated that under anaerobic conditions, suspended CeO2 NPs in a 3 mM FeCl2 solution at pH 4.8 were much more stable against sedimentation than those in the absence of Fe2+. Redox reactions between CeO2 NPs and Fe2+ lead to the formation of 6-line ferrihydrite on the CeO2 surfaces, which enhanced the colloidal stability by increasing the zeta potential and hydrophilicity of CeO2 NPs. These redox reactions can affect the toxicity of CeO2 NPs by increasing cerium dissolution, and by creating new Fe(III) (hydr)oxide reactive surface layers. Thus, these findings have significant implications for elucidating the phase transformation and transport of redox reactive NPs in the environment.

  16. Graphene-based porous materials with tunable surface area and CO2 adsorption properties synthesized by fluorine displacement reaction with various diamines.

    PubMed

    Li, Baoyin; Fan, Kun; Ma, Xin; Liu, Yang; Chen, Teng; Cheng, Zheng; Wang, Xu; Jiang, Jiaxing; Liu, Xiangyang

    2016-09-15

    A mild, operationally simple and controllable protocol for preparing graphene-based porous materials is essential to achieve a good pore-design development. In this paper, graphene-based porous materials with tunable surface area were constructed by the intercalation of fluorinated graphene (FG) based on the reaction of reactive CF bonds attached to graphene sheets with various amine-terminated molecules. In the porous materials, graphene sheets are like building blocks, and the diamines covalently grafted onto graphene framework act as pillars. Various diamines are successfully grafted onto graphene sheets, but the grafting ratio of diamines and reduction degree of FG differ greatly and depend on the chemical reactivity of diamines. Pillared diamine molecules chemically anchor at one end and are capable of undergoing a different reaction on the other end, resulting in three different conformations of graphene derivatives. Nitrogen sorption isotherms revealed that the surface area and pore distribution of the obtained porous materials depend heavily on the size and structure of diamine pillars. CO2 uptake capacity characterization showed that ethylenediamine intercalated FG achieved a high CO2 uptake density of 18.0 CO2 molecules per nm(2) at 0°C and 1.1bars, and high adsorption heat, up to 46.1kJmol(-1) at zero coverage. PMID:27280538

  17. Graphene-based porous materials with tunable surface area and CO2 adsorption properties synthesized by fluorine displacement reaction with various diamines.

    PubMed

    Li, Baoyin; Fan, Kun; Ma, Xin; Liu, Yang; Chen, Teng; Cheng, Zheng; Wang, Xu; Jiang, Jiaxing; Liu, Xiangyang

    2016-09-15

    A mild, operationally simple and controllable protocol for preparing graphene-based porous materials is essential to achieve a good pore-design development. In this paper, graphene-based porous materials with tunable surface area were constructed by the intercalation of fluorinated graphene (FG) based on the reaction of reactive CF bonds attached to graphene sheets with various amine-terminated molecules. In the porous materials, graphene sheets are like building blocks, and the diamines covalently grafted onto graphene framework act as pillars. Various diamines are successfully grafted onto graphene sheets, but the grafting ratio of diamines and reduction degree of FG differ greatly and depend on the chemical reactivity of diamines. Pillared diamine molecules chemically anchor at one end and are capable of undergoing a different reaction on the other end, resulting in three different conformations of graphene derivatives. Nitrogen sorption isotherms revealed that the surface area and pore distribution of the obtained porous materials depend heavily on the size and structure of diamine pillars. CO2 uptake capacity characterization showed that ethylenediamine intercalated FG achieved a high CO2 uptake density of 18.0 CO2 molecules per nm(2) at 0°C and 1.1bars, and high adsorption heat, up to 46.1kJmol(-1) at zero coverage.

  18. Ozone adsorption on carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Chassard, Guillaume; Gosselin, Sylvie; Visez, Nicolas; Petitprez, Denis

    2014-05-01

    Carbonaceous particles produced by incomplete combustion or thermal decomposition of hydrocarbons are ubiquitous in the atmosphere. On these particles are adsorbed hundreds of chemical species. Those of great concern to health are polycyclic aromatic hydrocarbons (PAHs). During atmospheric transport, particulate PAHs react with gaseous oxidants. The induced chemical transformations may change toxicity and hygroscopicity of these potentially inhalable particles. The interaction between ozone and carbon particles has been extensively investigated in literature. However ozone adsorption and surface reaction mechanisms are still ambiguous. Some studies described a fast catalytic decomposition of ozone initiated by an atomic oxygen chemisorption followed by a molecular oxygen release [1-3]. Others suggested a reversible ozone adsorption according to Langmuir-type behaviour [4,5]. The aim of this present study is a better understanding of ozone interaction with carbon surfaces. An aerosol of carbon nanoparticles was generated by flowing synthetic air in a glass tube containing pure carbon (primary particles < 50 nm), under magnetic stirring. The aerosol was then mixed with ozone in an aerosol flow tube. Ozone uptake experiments were performed with different particles concentrations with a fixed ozone concentration. The influence of several factors on kinetics was examined: initial ozone concentration, particle size (50 nm ≤ Dp ≤ 200 nm) and competitive adsorption (with probe molecule and water). The effect of initial ozone concentration was first studied. Accordingly to literature, it has been observed that the number of gas-phase ozone molecules lost per unit particle surface area tends towards a plateau for high ozone concentration suggesting a reversible ozone adsorption according to a Langmuir mechanism. We calculated the initial reaction probability between O3 and carbon particles.An initial uptake coefficient of 1.10-4 was obtained. Similar experiments were

  19. A DFT study of the acid-base properties of anatase TiO2 and tetragonal ZrO2 by adsorption of CO and CO2 probe molecules

    NASA Astrophysics Data System (ADS)

    Chen, Hsin-Yi Tiffany; Tosoni, Sergio; Pacchioni, Gianfranco

    2016-10-01

    We have performed a comparative study of the acid-base characteristics of the surfaces of anatase TiO2 and tetragonal ZrO2. To this end we performed DFT + U calculations on CO and CO2 probe molecules adsorbed both on terraces and steps of the two oxides. For titania, CO adsorption results in a moderate adsorption energy (about - 0.3 eV) and in a positive shift of the Csbnd O stretching frequency (about + 40 cm- 1), typical of Lewis acid sites, with no clear difference in the acidity between terraces or steps. For zirconia we found a similar CO binding energy as for titania, and a CO vibrational shift that depends on the location of the Zr cation: negligible on terraces, similar to TiO2 on steps. We conclude that the acidic properties are similar in the two oxide surfaces. Things are different for CO2 adsorption. On titania the interaction is weak and surface carbonates compete with physisorbed CO2, indicating a weak basic character. On the contrary, on zirconia three types of stable carbonates have been identified. Their vibrational frequencies are consistent with IR measurements reported in the literature. The most stable species forms on steps of the t-ZrO2 surface and consists of a CO32 - unit which lies flat on the surface with the O atoms pointing towards three Zr ions. The species forms spontaneously by extraction of a lattice oxygen by an incoming CO2 molecule. The different reactivity points towards a much more pronounced basic character of zirconia compared to titania, at least if measured by CO2 adsorption.

  20. Free radicals: how do we stand them? Anaerobic and aerobic free radical (chain) reactions involved in the use of fluorogenic probes and in biological systems.

    PubMed

    Liochev, Stefan I

    2014-01-01

    Biologically significant conclusions have been based on the use of fluorogenic and luminogenic probes for the detection of reactive species. The basic mechanisms of the processes involved have not been satisfactorily elucidated. In the present work, the mechanism of the enzyme and photosensitized oxidation of NAD(P)H by resorufin is analyzed and appears to involve both aerobic and anaerobic free radical chain reactions. There are two major fallouts of this analysis. Many of the conclusions about the participation of radicals based on the use of probes such as resorufin and Amplex red need reevaluation. It is also concluded that anaerobic free radical reactions may be biologically significant, and the possible existence of enzymatic systems to eliminate certain free radicals is discussed.

  1. Adsorption and Reaction of C(1)-C(3) Alcohols over CeO(x)(111) Thin Films

    SciTech Connect

    Mullins, David R; Senanayake, Sanjaya D; Chen, Tsung-Liang

    2010-01-01

    This study reports the interaction of methanol, ethanol, 1-propanol, and 2-propanol with well-ordered CeO{sub 2}(111) thin film surfaces. All of the alcohols adsorb at low temperature by forming alkoxy and hydroxyl species on the surface. On fully oxidized CeO{sub 2}(111), recombination occurs between some of the alkoxys and hydroxyls, resulting in alcohol desorption near 220 K. At the same temperature, some of the surface hydroxyls disproportionate to produce water and the loss of lattice O. The remaining alkoxys react above 550 K. The primary alcohols favor dehydrogenation products (aldehydes). There is a net loss of O from the system, resulting in a reduction of the ceria. The secondary alcohol, 2-propanol, undergoes primarily dehydration, producing propene with no net change in the cerium oxidation state. Reduced CeO{sub X}(111) competes with the gaseous products for available O. Little or no water is produced. The reaction selectivity for the C{sub 2} and C{sub 3} alcohols shifts toward favoring dehydration products. The loss of O from the alcohols leads to oxidation of the reduced ceria. Compared with the oxidized surface, the alkene desorption shifts to lower temperature, whereas the aldehyde desorption shifts to higher temperature. This indicates that, on the reduced surface, it is easier to break the C-O bond but more difficult to break the O-substrate bond.

  2. A potential fluorescent probe: Maillard reaction product from glutathione and ascorbic acid for rapid and label-free dual detection of Hg(2+) and biothiols.

    PubMed

    Dong, Jiang Xue; Song, Xiao Fang; Shi, Yan; Gao, Zhong Feng; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

    2016-07-15

    Maillard reactions and their fluorescent products have drawn much attention in the fields of food and life science, however, the application of fluorescent products separated from the reaction as an indicator for detection of certain substances in sensor field has not been mentioned. In this article, we report on an easy-to-synthesize and water-soluble fluorescent probe separated from the typical Maillard reaction products of glutathione and ascorbic acid, with excellent stability and high quantum yield (18.2%). The further application of the probe has been explored for dual detection of Hg(2+) and biothiols including cysteine, homocysteine, and glutathione, which is based on Hg(2+)-induced fluorescence quenching of the Maillard reaction fluorescent products (MRFPs) and the fluorescence recovery as the introduction of biothiols. This sensing system exhibits a good selectivity and sensitivity, and the linear ranges for Hg(2+), cysteine, homocysteine, and glutathione are 0.05-12, 0.5-10, 0.3-20, and 0.3-20μM, respectively. The detection limits for Hg(2+), cysteine, homocysteine, and glutathione are 22, 47, 96, and 30nM at a signal-to-noise ratio of 3, respectively. Furthermore, the practical applications of this sensor for Hg(2+) and biothiols determination in water samples and human plasma sample have been demonstrated with satisfactory results. PMID:27015151

  3. A potential fluorescent probe: Maillard reaction product from glutathione and ascorbic acid for rapid and label-free dual detection of Hg(2+) and biothiols.

    PubMed

    Dong, Jiang Xue; Song, Xiao Fang; Shi, Yan; Gao, Zhong Feng; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

    2016-07-15

    Maillard reactions and their fluorescent products have drawn much attention in the fields of food and life science, however, the application of fluorescent products separated from the reaction as an indicator for detection of certain substances in sensor field has not been mentioned. In this article, we report on an easy-to-synthesize and water-soluble fluorescent probe separated from the typical Maillard reaction products of glutathione and ascorbic acid, with excellent stability and high quantum yield (18.2%). The further application of the probe has been explored for dual detection of Hg(2+) and biothiols including cysteine, homocysteine, and glutathione, which is based on Hg(2+)-induced fluorescence quenching of the Maillard reaction fluorescent products (MRFPs) and the fluorescence recovery as the introduction of biothiols. This sensing system exhibits a good selectivity and sensitivity, and the linear ranges for Hg(2+), cysteine, homocysteine, and glutathione are 0.05-12, 0.5-10, 0.3-20, and 0.3-20μM, respectively. The detection limits for Hg(2+), cysteine, homocysteine, and glutathione are 22, 47, 96, and 30nM at a signal-to-noise ratio of 3, respectively. Furthermore, the practical applications of this sensor for Hg(2+) and biothiols determination in water samples and human plasma sample have been demonstrated with satisfactory results.

  4. Effect of sodium acetate additive in successive ionic layer adsorption and reaction on the performance of CdS quantum-dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Liu, I.-Ping; Chen, Liang-Yih; Lee, Yuh-Lang

    2016-09-01

    Sodium acetate (NaAc) is utilized as an additive in cationic precursors of the successive ionic layer adsorption and reaction (SILAR) process to fabricate CdS quantum-dot (QD)-sensitized photoelectrodes. The effects of the NaAc concentration on the deposition rate and distribution of QDs in mesoporous TiO2 films, as well as on the performance of CdS-sensitized solar cells are studied. The experimental results show that the presence of NaAc can significantly accelerate the deposition of CdS, improve the QD distribution across photoelectrodes, and thereby, increase the performance of solar cells. These results are mainly attributed to the pH-elevation effect of NaAc to the cationic precursors which increases the electrostatic interaction of the TiO2 film to cadmium ions. The light-to-energy conversion efficiency of the CdS-sensitized solar cell increases with increasing concentration of the NaAc and approaches a maximum value (3.11%) at 0.05 M NaAc. Additionally, an ionic exchange is carried out on the photoelectrode to transform the deposited CdS into CdS1-xSex ternary QDs. The light-absorption range of the photoelectrode is extended and an exceptional power conversion efficiency of 4.51% is achieved due to this treatment.

  5. Adsorption and reactions on a surface alloy: CO, NO, O 2 and CO 2 on Pd(100)-Mn-c(2×2)

    NASA Astrophysics Data System (ADS)

    Sandell, A.; Jaworowski, A. J.; Beutler, A.; Wiklund, M.

    1999-02-01

    The adsorption properties of the Pd(100)-Mn-c(2×2) surface alloy have been investigated using photoemission of both core and valence levels. CO adsorbs in a molecular form without affecting the alloy structure. Two CO species were found, one bonded to Pd, which desorbs upon heating to 270 K , and one bonded to Mn, which desorbs when heating to 400 K. O 2 destroys the alloy, leading to a disordered surface with MnO x complexes. The MnO x aggregates stabilize adsorbed CO 2 and act as active sites for the following oxidation reactions at 110 K: CO+O→CO 2, CO+2O→CO 3δ- and CO 2+O→CO 3δ-. The CO 2 species desorbs upon heating to 170 K , whereas the CO 3δ- species is stable up to temperatures between 300 and 500 K. When exposed to low amounts of NO at 110 K, the major part of the molecules dissociates in order to form MnO x, thereby destroying the alloy. Larger NO doses yield an increasing amount of molecular NO, which dissociate upon heating to 300 K. CO can react with the dissociated NO to form CO 2 and another species with a C 1s binding energy and thermal stability similar to that of CO 3δ-. This species was tentatively identified as -NCO or -NCO 2.

  6. Enhanced super-hydrophobic and switching behavior of ZnO nanostructured surfaces prepared by simple solution--immersion successive ionic layer adsorption and reaction process.

    PubMed

    Suresh Kumar, P; Sundaramurthy, J; Mangalaraj, D; Nataraj, D; Rajarathnam, D; Srinivasan, M P

    2011-11-01

    A simple and cost-effective successive ionic layer adsorption and reaction (SILAR) method was adopted to fabricate hydrophobic ZnO nanostructured surfaces on transparent indium-tin oxide (ITO), glass and polyethylene terephthalate (PET) substrates. ZnO films deposited on different substrates show hierarchical structures like spindle, flower and spherical shape with diameters ranging from 30 to 300 nm. The photo-induced switching behaviors of ZnO film surfaces between hydrophobic and hydrophilic states were examined by water contact angle and X-ray photoelectron spectroscopy (XPS) analysis. ZnO nanostructured films had contact angles of ~140° and 160°±2 on glass and PET substrates, respectively, exhibiting hydrophobic behavior without any surface modification or treatment. Upon exposure to ultraviolet (UV) illumination, the films showed hydrophilic behavior (contact angle: 15°±2), which upon low thermal stimuli revert back to its original hydrophobic nature. Such reversible and repeatable switching behaviors were observed upon cyclical exposure to ultraviolet radiation. These biomimetic ZnO surfaces exhibit good anti-reflective properties with lower reflectance of 9% for PET substrates. Thus, the present work is significant in terms of its potential application in switching devices, solar coatings and self-cleaning smart windows.

  7. Efficient CdSe quantum dot-sensitized solar cells prepared by an improved successive ionic layer adsorption and reaction process.

    PubMed

    Lee, Hyojoong; Wang, Mingkui; Chen, Peter; Gamelin, Daniel R; Zakeeruddin, Shaik M; Grätzel, Michael; Nazeeruddin, Md K

    2009-12-01

    In pursuit of efficient quantum dot (QD)-sensitized solar cells based on mesoporous TiO(2) photoanodes, a new procedure for preparing selenide (Se(2-)) was developed and used for depositing CdSe QDs in situ over TiO(2) mesopores by the successive ionic layer adsorption and reaction (SILAR) process in ethanol. The sizes and density of CdSe QDs over TiO(2) were controlled by the number of SILAR cycles applied. After some optimization of these QD-sensitized TiO(2) films in regenerative photoelectrochemical cells using a cobalt redox couple [Co(o-phen)(3)(2+/3+)], including addition of a final layer of CdTe, over 4% overall efficiencies were achieved at 100 W/m(2) with about 50% IPCE at its maximum. Light-harvesting properties and transient voltage decay/impedance measurements confirmed that CdTe-terminated CdSe QD cells gave better charge-collection efficiencies and kinetic parameters than corresponding CdSe QD cells. In a preliminary study, a CdSe(Te) QD-sensitized TiO(2) film was combined with an organic hole conductor, spiro-OMeTAD, and shown to exhibit a promising efficiency of 1.6% at 100 W/m(2) in inorganic/organic hybrid all-solid-state cells.

  8. Process optimization of deposition conditions of PbS thin films grown by a successive ionic layer adsorption and reaction (SILAR) method using response surface methodology

    NASA Astrophysics Data System (ADS)

    Yücel, Ersin; Yücel, Yasin; Beleli, Buse

    2015-07-01

    In this study, lead sulfide (PbS) thin films were synthesized by a successive ionic layer adsorption and reaction (SILAR) method with different pH, dipping time and dipping cycles. Response surface methodology (RSM) and central composite design (CCD) were successfully used to optimize the PbS films deposition parameters and understand the significance and interaction of the factors affecting the film quality. 5-level-3-factor central composite design was employed to evaluate the effects of the deposition parameters (pH, dipping time and dipping cycles) on the response (the optical band gap of the films). Data obtained from RSM were subjected to the analysis of variance (ANOVA) and analyzed using a second order polynomial equation. The optimal conditions for the PbS films deposition have been found to be: pH of 9.1, dipping time of 10 s and dipping cycles of 10 cycles. The predicted band gap of PbS film was 2.13 eV under the optimal conditions. Verification experiment (2.24 eV) confirmed the validity of the predicted model. The film structures were characterized by X-ray diffractometer (XRD). Morphological properties of the films were studied with a scanning electron microscopy (SEM). The optical properties of the films were investigated using a UV-visible spectrophotometer.

  9. Successive ionic layer adsorption and reaction deposited kesterite Cu{sub 2}ZnSnS{sub 4} nanoflakes counter electrodes for efficient dye-sensitized solar cells

    SciTech Connect

    Mali, Sawanta S.; Shim, Chang Su; Hong, Chang Kook

    2014-11-15

    Highlights: • Cu{sub 2}ZnSnS{sub 4} nanoflakes by SILAR technique. • Hydrothermal synthesis of TiO{sub 2}. • Counter electrode for DSSC application. • 4.48% conversion efficiency. - Abstract: In this investigation, we have successfully synthesized Cu{sub 2}ZnSnS{sub 4} (CZTS) nanoflakes by successive ionic layer adsorption and reaction (SILAR) method and used as a counter electrode in the hydrothermally grown TiO{sub 2} based dye sensitized solar cells (DSSCs). The prepared CZTS nanoflakes were characterized using X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), micro Raman spectroscopy and energy dispersive analysis. Our DSSCs results revealed that, compared with conventional Pt/FTO counter electrode DSSCs, nanoflakes of p-type CZTS as the photocathode and n-type TiO{sub 2} thin films as the photoanode shows an increased short circuit current (13.35 mA/cm{sup 2}) with 4.84% power conversion efficiency. The detailed interface properties of were analyzed by electrochemical impedance spectroscopy (EIS) measurements.

  10. Reactivity of a Thick BaO Film Supported on Pt(111): Adsorption and Reaction of NO2, H2O and CO2

    SciTech Connect

    Mudiyanselage, Kumudu; Yi, Cheol-Woo W.; Szanyi, Janos

    2009-09-15

    Reactions of NO2, H2O, and CO2 with a thick (> 20 MLE) BaO film supported on Pt(111) were studied with temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). NO2 reacts with a thick BaO to form surface nitrite-nitrate ion pairs at 300 K, while only nitrates form at 600 K. In the thermal decomposition process of nitrite–nitrate ion pairs, first nitrites decompose and desorb as NO. Then nitrates decompose in two steps : at lower temperature with the release of NO2 and at higher temperature, nitrates dissociate to NO + O2. The thick BaO layer converts completely to Ba(OH)2 following the adsorption of H2O at 300 K. Dehydration/dehydroxylation of this hydroxide layer can be fully achieved by annealing to 550 K. CO2 also reacts with BaO to form BaCO3 that completely decomposes to regenerate BaO upon annealing to 825 K. However, the thick BaO film cannot be converted completely to Ba(NOx)2 or BaCO3 under the experimental conditions employed in this study.

  11. First-principles calculations of the adsorption and hydrogenation reactions of CHx(x=0,4) species on a Fe(100) surface

    SciTech Connect

    Sorescu, D.C.

    2006-04-01

    A previous set of investigations related to adsorption, diffusion, and dissociation properties of CO [D. C. Sorescu, D. L. Thompson, M. M. Hurley, and C. F. Chabalowski, Phys. Rev. B 66, 035416 (2002)] and H2 [D. C. Sorescu, Catal. Today 105, 44 (2005)] on Fe(100) surface have been extended to the case of chemisorption properties of CHx (x=0,4) species on the same surface. Similar to our previous studies, the current work is based on first-principles plane-wave calculations using spin-polarized density functional theory (DFT) and the generalized gradient approximation (GGA). The calculations employ slab geometry and periodic boundary conditions. It was determined that CHx (x=0,2) species preferentially adsorb at the four-folded sites while the CH3 species prefer the binding at the bridge site. In contradistinction, the CH4 molecule is only weakly physisorbed on the surface, independent of surface site or molecular orientation. In the case of the C atom, the adsorption investigations have been extended to include both the coverage effects as well as the possibility for absorption at subsurface sites. The presence of the C atom at either hollow or subsurface sites was found to increase the stability of the other atomic (C, H, O) and molecular or radical species [CO, CHx (x=1,4)] adsorbed on the surface. Beside chemisorption properties, the activation energies for surface diffusion have been determined for all individual CHx (x=0,3)species while in the case of C atom diffusion to subsurface sites have also been considered. Finally, we have determined the minimum energy path for the elementary hydrogenation reactions of CHx (x=0,3) species. We found that for the ensemble of surface processes involving dissociation of CO and H2 on Fe(100) surface followed by hydrogenation of CHx (x=0,3) species with formation of CH4, the CO dissociation is the rate determining step with an activation energy of 24.5 kcal/mol.

  12. A simple naphthalene-based fluorescent probe for high selective detection of formaldehyde in toffees and HeLa cells via aza-Cope reaction.

    PubMed

    Xu, Junchao; Zhang, Yue; Zeng, Lintao; Liu, Jinbiao; Kinsella, Joseph M; Sheng, Ruilong

    2016-11-01

    A simple naphthalene-based fluorescent probe (AENO) for formaldehyde (FA) was successfully synthesized, which exhibited a significant fluorescence turn-on response towards FA in aqueous solution. The probe could quantitatively determine the concentration of FA (0-1.0mM) with excellent selectivity, high sensitivity and low limit of detection (0.57µM). The sensing mechanism was proposed as 2-aza-Cope rearrangement for AENO after reaction with FA, which was confirmed by (1)H NMR, HR-MS, FT-IR, UV-vis and fluorescence spectra. The probe has been employed to determine the FA contents in several commercially available toffee samples with satisfactory performance. Thus, AENO might be used as a promising tool for quantitative detection of FA in food. Furthermore, fluorescence imaging of HeLa cells indicated that the probe was cell membrane permeable and could be used for visualizing/imaging the FA trace/transportation in cancer cells. PMID:27591661

  13. Probe-free real-time reverse transcription polymerase chain reaction assays for the detection and typing of porcine reproductive and respiratory syndrome virus in Canada

    PubMed Central

    Eschbaumer, Michael; Li, Wansi (May); Wernike, Kerstin; Marshall, Frank; Czub, Markus

    2015-01-01

    Porcine reproductive and respiratory syndrome (PRRS) has tremendous impact on the pork industry in North America. The molecular diagnosis of infection with PRRS virus (PRRSV) is hampered by its considerable strain diversity. In this study, 43 previously published or newly developed primers for probe-free real-time reverse transcription polymerase chain reaction (RT-PCR) were evaluated on their sensitivity, specificity, reproducibility, and repeatability, using a diverse panel of 36 PRRSV strains as well as other arteriviruses and unrelated porcine viruses. Three primer pairs had excellent diagnostic and analytical sensitivity on par with a probe-based reference assay, absolute specificity to virus genotype and species, as well as over 95% reproducibility and repeatability across a wide dynamic range. PMID:26130848

  14. RADMAP: Simple probes for rapid assessment of complex reactivity: A method and case studies on the reaction of hydrogen atoms with unsaturated organic molecules.

    PubMed

    Long, Andrew K; Fawcett, Jason A; Clyburne, Jason A C; Pye, Cory C

    2016-03-01

    RADMAP, an open source program, allows for rapid analysis and visualization of the earliest stages of reactions between any molecule and a monoatomic probe (i.e., H*, H(+), H(-), Br*, or any other monoatomic species) using ab initio methods. This program creates non-planar potential energy surfaces of the initial interaction between a molecule of interest and the monoatomic probe. These surfaces can be used to both predict the site of addition as well as provide a qualitative estimate for the relative proportion of the formation of adducts; therefore, it gives insight into both the reactivity and the kinetic stability of a molecule. The program presents a way to quickly predict the number of signals anticipated in transverse field muon spin resonance spectra as well as their relative intensities. PMID:26851865

  15. Probe-free real-time reverse transcription polymerase chain reaction assays for the detection and typing of porcine reproductive and respiratory syndrome virus in Canada.

    PubMed

    Eschbaumer, Michael; Li, Wansi May; Wernike, Kerstin; Marshall, Frank; Czub, Markus

    2015-07-01

    Porcine reproductive and respiratory syndrome (PRRS) has tremendous impact on the pork industry in North America. The molecular diagnosis of infection with PRRS virus (PRRSV) is hampered by its considerable strain diversity. In this study, 43 previously published or newly developed primers for probe-free real-time reverse transcription polymerase chain reaction (RT-PCR) were evaluated on their sensitivity, specificity, reproducibility, and repeatability, using a diverse panel of 36 PRRSV strains as well as other arteriviruses and unrelated porcine viruses. Three primer pairs had excellent diagnostic and analytical sensitivity on par with a probe-based reference assay, absolute specificity to virus genotype and species, as well as over 95% reproducibility and repeatability across a wide dynamic range.

  16. Probing the Structure, Stability and Hydrogen Adsorption of Lithium Functionalized Isoreticular MOF-5 (Fe, Cu, Co, Ni and Zn) by Density Functional Theory

    PubMed Central

    Venkataramanan, Natarajan Sathiyamoorthy; Sahara, Ryoji; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2009-01-01

    Li adsorption on isoreticular MOFs with metal Fe, Cu, Co, Ni and Zn was studied using density function theory. Li functionalization shows a considerable structural change associated with a volume change in isoreticular MOF-5 except for the Zn metal center. Hydrogen binding energies on Li functionalized MOFs are seen to be in the range of 0.2 eV, which is the desired value for an ideal reversible storage system. This study has clearly shown that Li doping is possible only in Zn-based MOF-5, which would be better candidate to reversibly store hydrogen. PMID:19468328

  17. Probing Reaction Dynamics of Transition-Metal Complexes in Solution via Time-Resolved Soft X-ray Spectroscopy

    SciTech Connect

    Huse, Nils; Kim, Tae Kyu; Khalil, Munira; Jamula, Lindsey; McCusker, James K.; Schoenlein, Robert W.

    2010-05-02

    We report the first time-resolved soft x-ray measurements of solvated transition-metal complexes. L-edge spectroscopy directly probes dynamic changes in ligand-field splitting of 3d orbitals associated with the spin transition, and mediated by changes in ligand-bonding.

  18. Acid base reactions, phosphate and arsenate complexation, and their competitive adsorption at the surface of goethite in 0.7 M NaCl solution

    NASA Astrophysics Data System (ADS)

    Gao, Yan; Mucci, Alfonso

    2001-07-01

    Potentiometric titrations of the goethite-water interface were carried out at 25°C in 0.1, 0.3 and 0.7 M NaCl solutions. The acid/base properties of goethite at pH > 4 in a 0.7 M NaCl solution can be reproduced successfully using either the Constant Capacitance (CCM), the Basic Stern (BSM) or the Triple Layer models (TLM) when two surface acidity constants are considered. Phosphate and arsenate complexation at the surface of goethite was studied in batch adsorption experiments. The experiments were conducted in 0.7 mol/L NaCl solutions at 25°C in the pH range of 3.0 to 10.0. Phosphate shows a strong affinity for the goethite surface and the amount of phosphate adsorbed decreases with increasing pH. Phosphate complexation is described using a model consisting of three monodentate surface complexes. Arsenate shows a similar adsorption pattern on goethite but a higher affinity than phosphate. A model including three surface complexation constants describes the arsenate adsorption at [AsO 4] init = 23 and 34 μmol/L. The model prediction, however, overestimates arsenate adsorption at [AsO 4] init = 8.8 μmol/L. The goethite surface acidity constants as well as the preceding phosphate and arsenate surface complexation constants were evaluated by the CCM and BSM with the aid of the computer program FITEQL, version 2.0. The experimental investigation of phosphate and arsenate competitive adsorption in 0.7 mol/L NaCl was performed at [PO 4]/[AsO 4] ratios of 1:1, 2.5:1 and 5:1 with [AsO 4] init = 9.0 μmol/L and at a [PO 4]/[AsO 4] ratio of 1:1 with [AsO 4] init = 22 μmol/L. The surface complexation of arsenate decreases significantly in competitive adsorption experiments and the decrease is proportional to the amount of phosphate present. Phosphate adsorption is also reduced but less drastically in competitive adsorption and is not affected significantly by incremental additions of arsenate at pH > 7. The equilibrium model derived by combining the single oxyanion

  19. Chemical sensing flow probe

    DOEpatents

    Laguna, George R.; Peter, Frank J.; Butler, Michael A.

    1999-01-01

    A new chemical probe determines the properties of an analyte using the light absorption of the products of a reagent/analyte reaction. The probe places a small reaction volume in contact with a large analyte volume. Analyte diffuses into the reaction volume. Reagent is selectively supplied to the reaction volume. The light absorption of the reaction in the reaction volume indicates properties of the original analyte. The probe is suitable for repeated use in remote or hostile environments. It does not require physical sampling of the analyte or result in significant regent contamination of the analyte reservoir.

  20. Chemical sensing flow probe

    DOEpatents

    Laguna, G.R.; Peter, F.J.; Butler, M.A.

    1999-02-16

    A new chemical probe determines the properties of an analyte using the light absorption of the products of a reagent/analyte reaction. The probe places a small reaction volume in contact with a large analyte volume. Analyte diffuses into the reaction volume. Reagent is selectively supplied to the reaction volume. The light absorption of the reaction in the reaction volume indicates properties of the original analyte. The probe is suitable for repeated use in remote or hostile environments. It does not require physical sampling of the analyte or result in significant regent contamination of the analyte reservoir. 7 figs.

  1. Coherence motion of photoinduced nonadiabatic charge transfer reaction in solution: A numerical study of pump-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Sheu, Sheh-Yi; Yang, Dah-Yen

    1998-10-01

    We study the photoinduced charge separation processes in solution through a pump-probe spectroscopy theory [Dah-Yen Yang and Sheh-Yi Sheu, J. Chem. Phys. 106, 9427 (1997)] numerically. We investigate the detailed mechanism of nonadiabatic transition processes via the transition differential flux analysis. For the harmonic potential surfaces, an electronic coherence motion is observed in the overdamped exothermic activationless and inverted regimes.

  2. Comparative study on the effect of H2 pre-adsorption on CO oxidation in O2-poor atmosphere over Au/TiO2 and TiO2: Temperature programmed surface reaction by a multiplexed mass spectrometer testing

    NASA Astrophysics Data System (ADS)

    Si, Ruiru; Liu, Junfeng; Zhang, Yujuan; Chen, Xun; Dai, Wenxin; Fu, Xianzhi

    2016-11-01

    The behaviors of H2 pre-adsorption on CO oxidation in an O2-poor stream containing a trace H2O over Au/TiO2 and TiO2 have been investigated by a temperature programmed surface reaction testing, respectively. It was found that the H2 pre-adsorption could keep CO oxidation without H2O consumption over Au/TiO2, but suppress CO oxidation over TiO2. The chemisorption testing showed that the H2 adsorption at Au/TiO2 could benefit to the formation of Ti-bonded hydroxyl species (Ti4+-OH), while the H2 adsorption at TiO2 would consume the Ti-bonded hydroxyl species and form the bridge hydroxyl species (Ti4+-OH-Ti4+). These results show that only the Ti-bonded hydroxyl species (not all kinds of hydroxyl species) could act as the active species of oxidizing CO. Furthermore, it is suggested that the dissociative hydrogen adsorbed at Au sites could activate the lattice oxygen of TiO2 to form the active Ti-bonded hydroxyl species (hydrogen spillover from Au to TiO2), which exhibit a strong reducibility than the H directly adsorbed at TiO2.

  3. Development of an on-site rapid real-time polymerase chain reaction system and the characterization of suitable DNA polymerases for TaqMan probe technology.

    PubMed

    Furutani, Shunsuke; Naruishi, Nahoko; Hagihara, Yoshihisa; Nagai, Hidenori

    2016-08-01

    On-site quantitative analyses of microorganisms (including viruses) by the polymerase chain reaction (PCR) system are significantly influencing medical and biological research. We have developed a remarkably rapid and portable real-time PCR system that is based on microfluidic approaches. Real-time PCR using TaqMan probes consists of a complex reaction. Therefore, in a rapid real-time PCR, the optimum DNA polymerase must be estimated by using actual real-time PCR conditions. In this study, we compared the performance of three DNA polymerases in actual PCR conditions using our rapid real-time PCR system. Although KAPA2G Fast HS DNA Polymerase has the highest enzymatic activity among them, SpeedSTAR HS DNA Polymerase exhibited better performance to rapidly increase the fluorescence signal in an actual real-time PCR using TaqMan probes. Furthermore, we achieved rapid detection of Escherichia coli in 7 min by using SpeedSTAR HS DNA Polymerase with the same sensitivity as that of a conventional thermal cycler.

  4. Development of an on-site rapid real-time polymerase chain reaction system and the characterization of suitable DNA polymerases for TaqMan probe technology.

    PubMed

    Furutani, Shunsuke; Naruishi, Nahoko; Hagihara, Yoshihisa; Nagai, Hidenori

    2016-08-01

    On-site quantitative analyses of microorganisms (including viruses) by the polymerase chain reaction (PCR) system are significantly influencing medical and biological research. We have developed a remarkably rapid and portable real-time PCR system that is based on microfluidic approaches. Real-time PCR using TaqMan probes consists of a complex reaction. Therefore, in a rapid real-time PCR, the optimum DNA polymerase must be estimated by using actual real-time PCR conditions. In this study, we compared the performance of three DNA polymerases in actual PCR conditions using our rapid real-time PCR system. Although KAPA2G Fast HS DNA Polymerase has the highest enzymatic activity among them, SpeedSTAR HS DNA Polymerase exhibited better performance to rapidly increase the fluorescence signal in an actual real-time PCR using TaqMan probes. Furthermore, we achieved rapid detection of Escherichia coli in 7 min by using SpeedSTAR HS DNA Polymerase with the same sensitivity as that of a conventional thermal cycler. PMID:27271319

  5. Probing chain-end functionalization reactions in living anionic polymerization via matrix-assisted laser desorption ionization time-of-flight mass spectrometry

    NASA Astrophysics Data System (ADS)

    Arnould, Mark A.; Polce, Michael J.; Quirk, Roderic P.; Wesdemiotis, Chrys

    2004-11-01

    Matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) is applied to examine the products arising upon the preparation of chain-end functional polymers via living anionic polymerization techniques. Both post-polymerization functionalizations as well as the use of functionalized initiators are investigated. MALDI-TOF MS is shown to be a sensitive probe for the qualitative analysis of the major and minor oligomers from novel functionalization reactions whose mechanisms are not yet well established. The method is particularly valuable for the identification of the end groups of the minor, and often unexpected, distributions that may be undetectable by other analytical means. Complete characterization of all oligomers generated during functionalization reactions provides an essential tool to the synthetic chemist for understanding the corresponding mechanisms. This insight is necessary for selecting alternative routes or making modifications to the reaction conditions. It is demonstrated that MALDI-TOF MS can convey quantitative information about the yields of the chain-end groups introduced during functionalization. From the cases presented it is evident that post-polymerization reactions allow for better control of chain-end functionality and molecular weight than functionalization with the limited number of currently available protected functionalized initiators.

  6. PROBING REACTIVITY OF DISSOLVED ORGANIC MATTER FOR DISINFECTION BY-PRODUCT FORMATION USING XAD-8 RESIN ADSORPTION AND ULTRAFILTRATION FRACTIONATION. (R828045)

    EPA Science Inventory

    The disinfection by-product (DBP) reactivity (yield and speciation upon reaction with chlorine) of dissolved organic matter (DOM) isolated from two surface waters was investigated. The source waters, each having significantly different specific ultraviolet absorbance (SUVA

  7. Experimental probe for the production of 97Ru from the 7Li+93Nb reaction: A study of precompound emissions

    NASA Astrophysics Data System (ADS)

    Kumar, Deepak; Maiti, Moumita; Lahiri, Susanta

    2016-10-01

    Background: Interaction of weakly bound heavy ions with an intermediate or heavy target is not yet understood completely due to the scarcity of experimental data. In order to develop a clear understanding of breakup fusion or preequilibrium emission even in the low energy range, 3-10 MeV/nucleon, more experimental investigations are necessary. Purpose: We aim to study the reaction mechanisms involved in the weakly bound heavy-ion induced reaction 7Li+93Nb at low energies by measuring the production cross sections of the residual radionuclides. Method: Natural niobium (93Nb) foil, backed by an aluminum (Al) catcher, arranged in a stack was bombarded by 7Li ions of 20-45 MeV energy. Activity of the residues produced in each 93Nb target was measured by off line γ -ray spectrometry after the end of bombardment (EOB) and cross sections were calculated. Experimental cross sections were compared with those computed using compound and precompound models. Results: In general, measured excitation functions of all residues produced in the 7Li+93Nb reaction showed good agreement with the model calculations based on the Hauser-Feshbach formalism and the exciton model for compound and precompound processes, respectively. Significant preequilibrium emission of neutrons was observed at the relatively high energy tail of the excitation function of 97Ru. Conclusions: Preequilibrium processes played an important role in the enhancement of the cross section in the x n reaction channel over the compound reaction mechanism at higher energies for the 7Li+93Nb reaction. Additionally, indirect evidence of incomplete or breakup fusion was also perceived.

  8. Quantitative detection of chloroethene-reductive bacteria Dehalococcoides spp. using alternately binding probe competitive Polymerase Chain Reaction.

    PubMed

    Miyata, Ryo; Adachi, Ken; Tani, Hidenori; Kurata, Shinya; Nakamura, Kazunori; Tsuneda, Satoshi; Sekiguchi, Yuji; Noda, Naohiro

    2010-06-01

    Dehalococcoides spp. are responsible for the reductive dehalogenation of environmental contaminants and are candidates for engineered bioremediation. The development of a sensitive, reliable, and rapid method for the quantification of Dehalococcoides spp. is required for the effective use of the organisms in bioremediation sites. Here, we describe the quantification of the 16S rRNA gene of Dehalococcoides spp. using a recently developed quantification method named alternately binding probe competitive PCR (ABC-PCR). The primers and probe sets that were newly designed for ABC-PCR were found to have a high specificity for Dehalococcoides spp. The standard curve of ABC-PCR had a good fitting (R = 0.999), and the lower detection limit was 10 copies/microl of template DNA. We also investigated the effects of inherent PCR-inhibiting compounds in an environmental sample on the quantification using ABC-PCR or real-time PCR by adding the soil extraction solution to PCR mixtures. ABC-PCR was more robust against the PCR amplification inhibitors than real-time PCR. The copy number of the 16S rRNA gene of Dehalococcoides spp. in soil and groundwater samples was successfully quantified using ABC-PCR. In conclusion, ABC-PCR is useful for the quantification of Dehalococcoides spp. populations and dynamics at bioremediation sites.

  9. Probing reaction dynamics of transition-metal complexes in solution via time-resolved soft x-ray spectroscopy

    SciTech Connect

    Huse, N.; Kim, T.-K.; Khalil, M.; Jamula, L.; McCusker, J.K.; Schoenlein, R.W.

    2008-08-01

    We report the first time-resolved soft x-ray measurements of solvated transition-metal complexes. L-edge spectroscopy directly probes dynamic changes in ligand-field splitting of 3d orbitals associated with the spin transition, and mediated by changes in ligand-bonding. We report the first time-resolved soft x-ray spectroscopy of solution-phase molecular dynamics. Changes in ligand-field splitting and spin-state populations in 3d orbitals of the Fe{sup II} complex are directly probed via transient absorption changes of the Fe L{sub 2} and L{sub 3} edges following photo-induced metal-to-ligand charge transfer. With the emergence of high-flux ultrafast soft x-ray sources, details on interplay between atomic structure, electronic states, and spin contributions will be revealed. Our experimental approach opens the door to femtosecond soft x-ray investigations of liquid phase chemistry that have previously been inaccessible.

  10. Detection of Citrus leprosis virus C using specific primers and TaqMan probe in one-step real-time reverse-transcription polymerase chain reaction assays.

    PubMed

    Choudhary, Nandlal; Wei, G; Govindarajulu, A; Roy, Avijit; Li, Wenbin; Picton, Deric D; Nakhla, M K; Levy, L; Brlansky, R H

    2015-11-01

    Citrus leprosis virus C (CiLV-C), a causal agent of the leprosis disease in citrus, is mostly present in the South and Central America and spreading toward the North America. To enable better diagnosis and inhibit the further spread of this re-emerging virus a quantitative (q) real-time reverse transcription polymerase chain reaction (qRT-PCR) assay is needed for early detection of CiLV-C when the virus is present in low titer in citrus leprosis samples. Using the genomic sequence of CiLV-C, specific primers and probe were designed and synthesized to amplify a 73 nt amplicon from the movement protein (MP) gene. A standard curve of the 73 nt amplicon MP gene was developed using known 10(10)-10(1) copies of in vitro synthesized RNA transcript to estimate the copy number of RNA transcript in the citrus leprosis samples. The one-step qRT-PCR detection assays for CiLV-C were determined to be 1000 times more sensitive when compared to the one-step conventional reverse transcription polymerase chain reaction (RT-PCR) CiLV-C detection method. To evaluate the quality of the total RNA extracts, NADH dehydrogenase gene specific primers (nad5) and probe were included in reactions as an internal control. The one-step qRT-PCR specificity was successfully validated by testing for the presence of CiLV-C in the total RNA extracts of the citrus leprosis samples collected from Belize, Costa Rica, Mexico and Panama. Implementation of the one-step qRT-PCR assays for CiLV-C diagnosis should assist regulatory agencies in surveillance activities to monitor the distribution pattern of CiLV-C in countries where it is present and to prevent further dissemination into citrus growing countries where there is no report of CiLV-C presence. PMID:26341059

  11. Detection of Citrus leprosis virus C using specific primers and TaqMan probe in one-step real-time reverse-transcription polymerase chain reaction assays.

    PubMed

    Choudhary, Nandlal; Wei, G; Govindarajulu, A; Roy, Avijit; Li, Wenbin; Picton, Deric D; Nakhla, M K; Levy, L; Brlansky, R H

    2015-11-01

    Citrus leprosis virus C (CiLV-C), a causal agent of the leprosis disease in citrus, is mostly present in the South and Central America and spreading toward the North America. To enable better diagnosis and inhibit the further spread of this re-emerging virus a quantitative (q) real-time reverse transcription polymerase chain reaction (qRT-PCR) assay is needed for early detection of CiLV-C when the virus is present in low titer in citrus leprosis samples. Using the genomic sequence of CiLV-C, specific primers and probe were designed and synthesized to amplify a 73 nt amplicon from the movement protein (MP) gene. A standard curve of the 73 nt amplicon MP gene was developed using known 10(10)-10(1) copies of in vitro synthesized RNA transcript to estimate the copy number of RNA transcript in the citrus leprosis samples. The one-step qRT-PCR detection assays for CiLV-C were determined to be 1000 times more sensitive when compared to the one-step conventional reverse transcription polymerase chain reaction (RT-PCR) CiLV-C detection method. To evaluate the quality of the total RNA extracts, NADH dehydrogenase gene specific primers (nad5) and probe were included in reactions as an internal control. The one-step qRT-PCR specificity was successfully validated by testing for the presence of CiLV-C in the total RNA extracts of the citrus leprosis samples collected from Belize, Costa Rica, Mexico and Panama. Implementation of the one-step qRT-PCR assays for CiLV-C diagnosis should assist regulatory agencies in surveillance activities to monitor the distribution pattern of CiLV-C in countries where it is present and to prevent further dissemination into citrus growing countries where there is no report of CiLV-C presence.

  12. Probing the Energy Transfer Dynamics of Photosynthetic Reaction Center Complexes Through Hole-Burning and Single-Complex Spectroscopy

    SciTech Connect

    Riley, Kerry Joseph

    2007-01-01

    Photosynthesis is the process by which light energy is used to drive reactions that generate sugars to supply energy for cellular processes. It is one of the most important fundamental biological reactions and occurs in both prokaryotic (e.g. bacteria) and eukaryotic (e.g. plants and algae) organisms. Photosynthesis is also remarkably intricate, requiring the coordination of many different steps and reactions in order to successfully transform absorbed solar energy into a biochemical usable form of energy. However, the net reaction for all photosynthetic organisms can be reduced to the following, deceptively general, equation developed by Van Niel[1] H2 - D + Aimplieshv A - H2 + D where H2-D is the electron donor, e.g. H2O, H2S. A is the electron acceptor, e.g. CO2, and A-H2 is the synthesized sugar. Amazingly, this simple net equation is responsible for creating the oxidizing atmosphere of Earth and the recycling of CO2, both of which are necessary for the sustainment of the global ecosystem.

  13. Probing Nucleon-Nucleon Correlations via the (e,e'p) and (e,e'pN) Reactions

    SciTech Connect

    Douglas Higinbotham

    2005-09-01

    Probing nucleon-nucleon correlations has proven to be difficult due to competing mechanisms, such as final state rescattering and two-body currents, which can produce the same final state as one would expect from correlations. Recent A(e,e'p) and A(e,e'pN) measurements have sought to minimize the effects of competing mechanisms by going to special kinematics. For example going to kinematics where the particle with most of the kinetic energy is parallel to the momentum transfer vector, going to high momentum transfers, and/or going to large Bjorken x. The results of these measurements will be presented along with state-of-the-art theoretical calculations.

  14. Gas-phase reactions of doubly charged actinide cations with alkanes and alkenes--probing the chemical activity of 5f electrons from Th to Cm.

    PubMed

    Marçalo, Joaquim; Santos, Marta; Gibson, John K

    2011-11-01

    Small alkanes (methane, ethane, propane, n-butane) and alkenes (ethene, propene, 1-butene) were used to probe the gas-phase reactivity of doubly charged actinide cations, An(2+) (An = Th, Pa, U, Np, Pu, Am, Cm), by means of Fourier transform ion cyclotron resonance mass spectrometry. Different combinations of doubly and singly charged ions were observed as reaction products, comprising species formed via metal-ion induced eliminations of small molecules, simple adducts and ions resulting from electron, hydride or methide transfer channels. Th(2+), Pa(2+), U(2+) and Np(2+) preferentially yielded doubly charged products of hydrocarbon activation, while Pu(2+), Am(2+) and Cm(2+) reacted mainly through transfer channels. Cm(2+) was also capable of forming doubly charged products with some of the hydrocarbons whereas Pu(2+) and Am(2+) were not, these latter two ions conversely being the only for which adduct formation was observed. The product distributions and the reaction efficiencies are discussed in relation to the electronic configurations of the metal ions, the energetics of the reactions and similar studies previously performed with doubly charged lanthanide and transition metal cations. The conditions for hydrocarbon activation to occur as related to the accessibility of electronic configurations with one or two 5f and/or 6d unpaired electrons are examined and the possible chemical activity of the 5f electrons in these early actinide ions, particularly Pa(2+), is considered.

  15. Adsorption and reaction of acetylene on clean and oxygen-precovered Pd(100) studied with high-resolution X-ray photoelectron spectroscopy.

    PubMed

    Höfert, O; Lorenz, M P A; Streber, R; Zhao, W; Bayer, A; Steinrück, H-P; Papp, C

    2013-10-28

    We investigated the adsorption and thermal evolution of acetylene on clean Pd(100) and Pd(100) precovered with 0.25 ML oxygen. The measurements were performed in situ by fast XPS at the synchrotron radiation facility BESSY II. On Pd(100) acetylene molecularly adsorbs at 130 K. Upon heating transformation to a CCH species occurs around 390 K along with the formation of a completely dehydrogenated carbon species. On the oxygen-precovered surface partial CCH formation already occurs upon adsorption at 130 K, and the dehydrogenation temperature and the stability range of CCH are shifted to lower temperatures by ∼200 K. PMID:24182063

  16. Probing the chemical structure of monolayer covalent-organic frameworks grown via Schiff-base condensation reactions.

    PubMed

    Hu, Ya; Goodeal, Niall; Chen, Ying; Ganose, Alex M; Palgrave, Robert G; Bronstein, Hugo; Blunt, Matthew O

    2016-08-01

    Two-dimensional covalent-organic frameworks (2D-COFs) on surfaces offer a facile route to new 2D materials. Schiff-base condensation reactions have proven to be an effective fabrication route for such materials. We present scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) studies of porphyrin 2D-COFs grown at a solid-vapour interface. XPS shows that covalent links between porphyrins consist of a mixture of imines and hemiaminals, a non-conjugated intermediate in the Schiff-base condensation reaction. These results demonstrate that environmental conditions during growth can have an important impact on the chemical composition of Schiff-base 2D-COFs.

  17. Probing the Statistical Decay and α-clustering effects in 12C + 12C and 14N + 10B reactions

    NASA Astrophysics Data System (ADS)

    Morelli, L.; Baiocco, G.; D'Agostino, M.; Bruno, M.; Gulminelli, F.; Cinausero, M.; Degerlier, M.; Fabris, D.; Gramegna, F.; Marchi, T.; Barlini, S.; Bini, M.; Casini, G.; Gelli, N.; Lopez, A.; Pasquali, G.; Piantelli, S.; Valdrè, S.

    2014-03-01

    An experimental campaign has been undertaken at Laboratori Nazionali di Legnaro (LNL INFN), Italy, in order to progress in our understanding of the statistical properties of light nuclei at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation reactions. On the experimental side, a first reaction: 12C+12C at 95 MeV beam energy has been measured, using the GARFIELD + Ring Counter (RCo) apparatuses. Fusion-evaporation events have been exclusively selected out of the entire data set. The comparison to a dedicated Hauser-Feshbach calculation allows us to give constraints on the nuclear level density at high excitation energy for light systems ranging from C up to Mg. Out-of-equilibrium aα emission has been evidenced and attributed both to an entrance channel effect (favoured by the cluster nature of reaction partners), and, in more dissipative events, to the persistence of cluster correlations well above the 24Mg threshold for 6 α's decay. In order to study the same 24Mg compound nucleus at similar excitation energy with respect to this first reaction a new measurement, 14N + 10B at 5.7 A.MeV, was performed at LNL laboratories with the same experimental setup. The comparison between the two systems would allow us to further constrain the level density of light nuclei in the mass-excitation energy range of interest. In this perspective, deviations from a statistical behaviour can be used as a tool to get information on nuclear clustering, both in the ground-state for projectile and target and in the hot source formed in the collision.

  18. Genetic probes of structure/function relationships in the Q{sub B} binding site of the photosynthetic reaction center

    SciTech Connect

    Hanson, D.K.; Tiede, D.M.; Nance, S.L.; Chang, Chong-Hwan; Schiffer, M.

    1991-06-25

    In photosynthetic reaction centers, a quinone molecule, Q{sub B}, is the terminal acceptor in light-induced electron transfer. The crystal structure of the reaction center implicates the protonatable amiho acid residues L212Glu and L213Asp in the binding of Q{sub B} to the reaction center and in proton transfer to the anionic forms of Q{sub B} generated by electron transfer from Q{sub A}. Here we report the construction of the double mutant L212Ala-L213Ala by site-specific mutagenesis, and the isolation and preliminary biophysical characterization of revertant and suppressor strains that have regained the ability to grow under photosynthetic conditions. Our results show that neither L212Glu nor L213Asp is essential for efficient light-induced electron or proton transfer in Rhodobacter capsulatus and that second-site mutations, located within the QB binding pocket or at a more distant site, can compensate for mutations at L212 and L213. Acquisition of a single negatively charged residue (at position L213, or on the other side of the binding pocket at position L225) or loss of a positively charged residue (at position M231) is sufficient to restore activity to the complex.

  19. Catalyst Chemical State during CO Oxidation Reaction on Cu(111) Studied with Ambient-Pressure X-ray Photoelectron Spectroscopy and Near Edge X-ray Adsorption Fine Structure Spectroscopy.

    PubMed

    Eren, Baran; Heine, Christian; Bluhm, Hendrik; Somorjai, Gabor A; Salmeron, Miquel

    2015-09-01

    The chemical structure of a Cu(111) model catalyst during the CO oxidation reaction in the CO+O2 pressure range of 10-300 mTorr at 298-413 K was studied in situ using surface sensitive X-ray photoelectron and adsorption spectroscopy techniques [X-ray photoelectron spectroscopy (XPS) and near edge X-ray adsorption fine structure spectroscopy (NEXAFS)]. For O2:CO partial pressure ratios below 1:3, the surface is covered by chemisorbed O and by a thin (∼1 nm) Cu2O layer, which covers completely the surface for ratios above 1:3 between 333 and 413 K. The Cu2O film increases in thickness and exceeds the escape depth (∼3-4 nm) of the XPS and NEXAFS photoelectrons used for analysis at 413 K. No CuO formation was detected under the reaction conditions used in this work. The main reaction intermediate was found to be CO2(δ-), with a coverage that correlates with the amount of Cu2O, suggesting that this phase is the most active for CO oxidation.

  20. Optically probing Al—O and O—H vibrations to characterize water adsorption and surface reconstruction on α-alumina: An experimental and theoretical study

    SciTech Connect

    Tong, Yujin Kirsch, Harald; Wolf, Martin; Campen, R. Kramer; Wirth, Jonas; Saalfrank, Peter

    2015-02-07

    Oxide/water interfaces are ubiquitous in a wide variety of applications and the environment. Despite this ubiquity, and attendant decades of study, gaining molecular level insight into water/oxide interaction has proven challenging. In part, this challenge springs from a lack of tools to concurrently characterize changes in surface structure (i.e., water/oxide interaction from the perspective of the solid) and O—H population and local environment (i.e., water/oxide interaction from the water perspective). Here, we demonstrate the application of surface specific vibrational spectroscopy to the characterization of the interaction of the paradigmatic α-Al{sub 2}O{sub 3}(0001) surface and water. By probing both the interfacial Al—O (surface phonon) and O—H spectral response, we characterize this interaction from both perspectives. Through electronic structure calculation, we assign the interfacial Al—O response and rationalize its changes on surface dehydroxylation and reconstruction. Because our technique is all-optical and interface specific, it is equally applicable to oxide surfaces in vacuum, ambient atmospheres and at the solid/liquid interface. Application of this approach to additional alumina surfaces and other oxides thus seems likely to significantly expand our understanding of how water meets oxide surfaces and thus the wide variety of phenomena this interaction controls.

  1. Facile Synthesis of Silica-Encapsulated Gold Nanoflowers as Surface-Enhanced Raman Scattering Probes Using Silane-Mediated Sol-Gel Reaction.

    PubMed

    Yoo, Jihye; Park, Sang-Joon; Lee, Sang-Wha

    2016-06-01

    Flower-like gold nanoparticles, so called gold nanoflowers (AuNFs), were synthesized through the reduction of HAuC4 with ascorbic acid in the presence of chitosan polymers. Chitosan-mediated AuNFs exhibited the distinct SERS signals of 2-chlorothiophenol (CTP) due to the presence of many interstitial gaps (so called hot spots) on the surface. For the facile silica coating, the AuNFs were conjugated with terminal carboxylate groups of (3-glycidyloxypropyl)trimethoxysilane (GPTMS), consequently forming alkoxy-terminated AuNFs which could facilely participate in the sol-gel reaction for silica coating. The resulting core-shell particles, i.e., CTP-adsorbed AuNFs with silica coating, exhibited the distinct SERS signals of CTP embedded within silica layer, warranting the effectiveness of this chemical strategy for spectroscopic labeling of Raman probes. PMID:27427704

  2. Facile Synthesis of Silica-Encapsulated Gold Nanoflowers as Surface-Enhanced Raman Scattering Probes Using Silane-Mediated Sol-Gel Reaction.

    PubMed

    Yoo, Jihye; Park, Sang-Joon; Lee, Sang-Wha

    2016-06-01

    Flower-like gold nanoparticles, so called gold nanoflowers (AuNFs), were synthesized through the reduction of HAuC4 with ascorbic acid in the presence of chitosan polymers. Chitosan-mediated AuNFs exhibited the distinct SERS signals of 2-chlorothiophenol (CTP) due to the presence of many interstitial gaps (so called hot spots) on the surface. For the facile silica coating, the AuNFs were conjugated with terminal carboxylate groups of (3-glycidyloxypropyl)trimethoxysilane (GPTMS), consequently forming alkoxy-terminated AuNFs which could facilely participate in the sol-gel reaction for silica coating. The resulting core-shell particles, i.e., CTP-adsorbed AuNFs with silica coating, exhibited the distinct SERS signals of CTP embedded within silica layer, warranting the effectiveness of this chemical strategy for spectroscopic labeling of Raman probes.

  3. Photosynthetic reaction center functionalized nano-composite films: effective strategies for probing and exploiting the photo-induced electron transfer of photosensitive membrane protein.

    PubMed

    Lu, Yidong; Xu, Jingjing; Liu, Baohong; Kong, Jilie

    2007-02-15

    Photosynthetic reaction center (RC), a robust transmembrane pigment-protein complex, works as the crucial component participating the primary event of the photo-electrochemical conversion in bacteria. Sparked by the high photo-induced charge separation yield (ca. 100%) of RC, great interests have been aroused to fabricate versatile RC-functionalized nano-composite films for exploring the initial photosynthetic electron transfer (ET) of RC, and thus exploiting well-designed bio-photoelectric converters. In this review, we classify and summarize the current status about the concepts and methods of constructing RC-immobilized nano-composite films or devices for probing the photo-induced ET, and applying to novel bioelectronics if it is possible.

  4. Real-time polymerase chain reaction (PCR) quantitative detection of Brassica napus using a locked nucleic acid TaqMan probe.

    PubMed

    Schmidt, Anna-Mary; Rott, Michael E

    2006-02-22

    Several countries have introduced mandatory labeling requirements on foods derived from genetically modified organisms. Real-time quantitative Polymerase Chain Reaction (PCR) has quickly become the method of choice in support of these regulations and requires the development of separate PCR assays targeting the transgenic sequence as well as a specific endogenous gene sequence. To develop a Brassica napus-specific PCR assay, partial sequences of the acetyl-CoA carboxylase BnACCg8 gene from B. napus and the closely related Brassica rapa were determined and compared, and a region of unique nucleotide sequence was identified. Universal amplification primers were designed to either side of this region, and a locked nucleic acid TaqMan probe was designed to the B. napus-specific sequence. Evaluation of this primer/probe combination indicated a high level of specificity to B. napus: no amplification signal was observed with any other species tested, including five closely related Brassica species. The method was assayed with 14 different B. napus cultivars, and comparable amplification curves were consistently obtained for all. The assay was highly sensitive, with a limit of detection between 1 and 10 haploid copies. Practically, the method was demonstrated to be effective for the detection of processed food samples and for the quantification of Roundup Ready canola content in mixed samples.

  5. Development of an event-specific hydrolysis probe quantitative real-time polymerase chain reaction assay for Embrapa 5.1 genetically modified common bean (Phaseolus vulgaris).

    PubMed

    Treml, Diana; Venturelli, Gustavo L; Brod, Fábio C A; Faria, Josias C; Arisi, Ana C M

    2014-12-10

    A genetically modified (GM) common bean event, namely Embrapa 5.1, resistant to the bean golden mosaic virus (BGMV), was approved for commercialization in Brazil. Brazilian regulation for genetically modified organism (GMO) labeling requires that any food containing more than 1% GMO be labeled. The event-specific polymerase chain reaction (PCR) method has been the primary trend for GMO identification and quantitation because of its high specificity based on the flanking sequence. This work reports the development of an event-specific assay, named FGM, for Embrapa 5.1 detection and quantitation by use of SYBR Green or hydrolysis probe. The FGM assay specificity was tested for Embrapa 2.3 event (a noncommercial GM common bean also resistant to BGMV), 46 non-GM common bean varieties, and other crop species including maize, GM maize, soybean, and GM soybean. The FGM assay showed high specificity to detect the Embrapa 5.1 event. Standard curves for the FGM assay presented a mean efficiency of 95% and a limit of detection (LOD) of 100 genome copies in the presence of background DNA. The primers and probe developed are suitable for the detection and quantitation of Embrapa 5.1.

  6. Development and validation of a novel hydrolysis probe real-time polymerase chain reaction for agamid adenovirus 1 in the central bearded dragon (Pogona vitticeps).

    PubMed

    Fredholm, Daniel V; Coleman, James K; Childress, April L; Wellehan, James F X

    2015-03-01

    Agamid adenovirus 1 (AgAdv-1) is a significant cause of disease in bearded dragons (Pogona sp.). Clinical manifestations of AgAdv-1 infection are variable and often nonspecific; the manifestations range from lethargy, weight loss, and inappetence, to severe enteritis, hepatitis, and sudden death. Currently, diagnosis of AgAdv-1 infection is achieved through a single published method: standard nested polymerase chain reaction (nPCR) and sequencing. Standard nPCR with sequencing provides reliable sensitivity, specificity, and validation of PCR products. However, this process is comparatively expensive, laborious, and slow. Probe hybridization, as used in a TaqMan assay, represents the best option for validating PCR products aside from the time-consuming process of sequencing. This study developed a real-time PCR (qPCR) assay using a TaqMan probe-based assay, targeting a highly conserved region of the AgAdv-1 genome. Standard curves were generated, detection results were compared with the gold standard conventional PCR and sequencing assay, and limits of detection were determined. Additionally, the qPCR assay was run on samples known to be positive for AgAdv-1 and samples known to be positive for other adenoviruses. Based on the results of these evaluations, this assay allows for a less expensive, rapid, quantitative detection of AgAdv-1 in bearded dragons.

  7. Microbead-based ligase detection reaction assay using a molecular beacon probe for the detection of low-abundance point mutations.

    PubMed

    Watanabe, Sho; Hagihara, Kenta; Tsukagoshi, Kazuhiko; Hashimoto, Masahiko

    2014-01-01

    A microbead-based ligase detection reaction (LDR) assay using a molecular beacon probe was developed for the facile and rapid detection of point mutations present in low copy numbers in a mixed population of wild-type DNA. Biotin-tagged ligation products generated in the LDR were captured on the surface of streptavidin-modified magnetic beads for purification and concentration. The resulting product-tethered microbeads were combined with a molecular beacon probe solution, and the suspension was directly flowed into a capillary. The microbeads were accumulated in a confined space within the capillary using a bar magnet. The packed bead sample was then scanned by a fluorescence scanning imager to detect the presence of any mutations. With the developed methodology, we were able to successfully detect one cancer mutation in a mixture of 400 wild-type templates (t test at 95% confidence level). Furthermore, the post-LDR processing, typically the most laborious and time-consuming step in LDR-based mutation detection assays, could be carried out much more rapidly (approximately 20 min). This was enabled by the simple bead and fluid manipulations involved in the present assay.

  8. Polymer adsorption

    NASA Astrophysics Data System (ADS)

    Joanny, Jean-Francois

    2008-03-01

    The aim of this talk is to review Pierre-Gilles deGennes' work on polymer adsorption and the impact that it has now in our understanding of this problem. We will first present the self-consistent mean-field theory and its applications to adsorption and depletion. De Gennes most important contribution is probably the derivation of the self-similar power law density profile for adsorbed polymer layers that we will present next, emphasizing the differences between the tail sections and the loop sections of the adsorbed polymers. We will then discuss the kinetics of polymer adsorption and the penetration of a new polymer chain in an adsobed layer that DeGennes described very elegantly in analogy with a quantum tunneling problem. Finally, we will discuss the role of polymer adsorption for colloid stabilization.

  9. Reactions between vanadium ions and biogenic reductants of tunicates: Spectroscopic probing for complexation and redox products in vitro

    SciTech Connect

    Ryan, D.E.; Grant, K.B.; Nakanishi, K.

    1996-07-02

    Several species of marine tunicates store oxygen-sensitive V{sup III} in blood cells. A sensitive colorimetric V{sup III} assay was used t survey the leading candidates for the native reducing agent of vanadate in tunicates (i.e., An-type tunichromes, glutathione, NADPH, and H{sub 2}S) in reactions with V{sup V} or V{sup IV} ions under anaerobic, aqueous conditions at acidic or neutral pH. Except for the case of An-1 and V{sup V} ions in pH 7 buffer, the assay results for the biogenic reducing agents clearly showed that appreciable quantities of V{sup III} products were not generated under the conditions tested. Therefore, the assay results place new limits on hypothetical mechanisms of V{sup III} formation in vivo. For reactions between An-1 and V{sup V} ions in pH 7 buffer, low levels of V{sup III} products could not be ruled out because of an interfering peak in the colorimetric assays. For similar reactions between V{sup V} ions and An-1, or an An-1,2 mixture, in mildly to moderately basic media, the product mixtures precipitated as greenish black solids. Analyses of the precipitated V/An mixtures using vanadium K-edge X-ray absorption spectroscopy (XAS) showed that the major products were tris(catecholate)-type V{sup IV} complexes (65 {plus_minus} 6%) and bis(catecholate)-type V{sup IV}O complexes (20 {plus_minus} 4%). XAS analysis of the V/An-1 product mixture also provided evidence of a minor V{sup III} component (9 {plus_minus} 5% of total V), notable for possible relevance to tunicate biochemistry. The combined results of XAS studies, spectrophotometric studies, and EPR studies consistently establish that reactions between tunichromes (Mm-1 or An-1) and V{sup V} ions generate predominantly V{sup IV}-tunichrome complexes in neutral to moderately basic aqueous media. 53 refs., 4 figs., 3 tabs.

  10. Estimation of free energy barriers in the cytoplasmic and mitochondrial aspartate aminotransferase reactions probed by hydrogen-exchange kinetics of C alpha-labeled amino acids with solvent

    SciTech Connect

    Julin, D.A.; Wiesinger, H.; Toney, M.D.; Kirsch, J.F. )

    1989-05-02

    The existence of the postulated quinonoid intermediate in the cytoplasmic aspartate amino-transferase catalyzed transamination of aspartate to oxaloacetate was probed by determining the extent of transfer of tritium from the C alpha position of tritiated L-aspartate to pyridoxamine 5'-phosphate in single turnover experiments in which washout from the back-reaction was obviated by product trapping. The maximum amount of transferred tritium observed was 0.7%, consistent either with a mechanism in which a fraction of the net transamination reaction proceeds through a quinonoid intermediate or with a mechanism in which this intermediate is formed off the main reaction pathway. It is shown that transfer of labeled hydrogen from the amino acid to cofactor cannot be used to differentiate a stepwise from a concerted transamination mechanism. The amount of tritium transferred is a function of the rate constant for torsional equilibration about the epsilon-amino group of Lys-258, the presumptive abstractor of the C alpha proton; the relative rate constants for hydrogen exchange with solvent versus cofactor protonation; and the tritium isotope effect on this ratio. The free energy barriers facing the covalent intermediate between aldimine and keto acid product (i.e., ketimine and possibly quinonoid) were evaluated relatively by comparing the rates of C alpha-hydrogen exchange in starting amino acid with the rates of keto acid formation. The value of theta (= kexge/kprod) was found to be 2.6 for the reaction of cytoplasmic isozyme with aspartate and ca. 0.5 for that of the mitochondrial form with glutamate.

  11. Lipid Peroxides Promote Large Rafts: Effects of Excitation of Probes in Fluorescence Microscopy and Electrochemical Reactions during Vesicle Formation

    PubMed Central

    Ayuyan, Artem G.; Cohen, Fredric S.

    2006-01-01

    Raft formation and enlargement was investigated in liposomes and supported bilayers prepared from sphingomyelin (SM), cholesterol, and unsaturated phospholipids; NBD-DPPE and rhodamine-(DOPE) were employed as fluorescent probes. Rafts were created by lowering temperature. Maintaining 20 mol % SM, fluorescence microscopy showed that, in the absence of photooxidation, large rafts did not form in giant unilamellar vesicles (GUVs) containing 20 or more mol % cholesterol. But if photooxidation was allowed to proceed, large rafts were readily observed. In population, cuvette experiments, small rafts formed without photooxidation at high cholesterol concentrations. Thus, photooxidation was the cause of raft enlargement during microscopy experiments. Because photooxidation results in peroxidation at lipid double bonds, photosensitization experiments were performed to explicitly produce peroxides of SM and an unsaturated phospholipid. GUVs of high cholesterol content containing the breakdown products of SM-peroxide, but not phospholipid-peroxide, resulted in large rafts after lowering temperature. In addition, GUV production by electroswelling can result in peroxides that cause large raft formation. The use of titanium electrodes eliminates this problem. In conclusion, lipid peroxides and their breakdown products are the cause of large raft formation in GUVs containing biological levels of cholesterol. It is critical that experiments investigating rafts in bilayer membranes avoid the production of peroxides. PMID:16815906

  12. Multistep atomic reaction enhanced by an atomic force microscope probe on Si(111) and Ge(111) surfaces

    NASA Astrophysics Data System (ADS)

    Enkhtaivan, Batnyam; Oshiyama, Atsushi

    2016-08-01

    We present first-principles total-energy electronic-structure calculations that provide the microscopic mechanism of the adatom interchange reaction on the Sn- and Pb-covered Ge(111)-(2 ×8 ) and the Sb-covered Si(111)-(7 ×7 ) surfaces with and without the tip of the atomic force microscope (AFM). We find that, without the presence of the AFM tip on the Ge surface, the adatom interchange occurs through the migration of the adatom, the spontaneous formation of the dimer structures of the two adatoms, the dimer-dimer structural transitions that induce the exchange of the positions of the two adatoms, and then the backward migration of the adatom. We also find that the dimer structure is unfeasible at room temperature on the Si surface and the adatom interchange are hereby unlikely. With the presence of the tip, we find that the reaction pathways are essentially the same for the Ge surface but that the energy barriers of the migration and the exchange processes are substantially reduced by the AFM tip. We further find that the AFM tip induces the spontaneous formation of the dimer structure even on the Si surface, hereby opening a channel of the interchange of the adatoms. Our calculations show that the bond formation between the AFM tip atom and the surface adatom is essential for the atom manipulation using the AFM tip.

  13. Molecular beam studies of unimolecular and bimolecular chemical reaction dynamics using VUV synchrotron radiation as a product probe

    SciTech Connect

    Blank, D.A.

    1997-08-01

    This dissertation describes the use of a new molecular beam apparatus designed to use tunable VUV synchrotron radiation for photoionization of the products from scattering experiments. The apparatus was built at the recently constructed Advanced Light Source at Lawrence Berkeley National Laboratory, a third generation 1-2 GeV synchrotron radiation source. The new apparatus is applied to investigations of the dynamics of unimolecular reactions, photodissociation experiments, and bimolecular reactions, crossed molecular beam experiments. The first chapter describes the new apparatus and the VUV radiation used for photoionization. This is followed by a number of examples of the many advantages provided by using VUV photoionization in comparison with the traditional technique of electron bombardment ionization. At the end of the chapter there is a discussion of the data analysis employed in these scattering experiments. The remaining four chapters are complete investigations of the dynamics of four chemical systems using the new apparatus and provide numerous additional examples of the advantages provided by VUV photoionizaiton of the products. Chapters 2-4 are photofragment translational spectroscopy studies of the photodissociation dynamics of dimethyl sulfoxide, acrylonitrile, and vinyl chloride following absorption at 193 mn. All of these systems have multiple dissociation channels and provide good examples of the ability of the new apparatus to unravel the complex UV photodissociation dynamics that can arise in small polyatomic molecules.

  14. Utilization of Microwave Spectroscopy to Identify and Probe Reaction Dynamics of Hsno, a Crucial Biological Signaling Molecule

    NASA Astrophysics Data System (ADS)

    Nava, Matthew; Martin-Drumel, Marie-Aline; Stanton, John F.; Cummins, Christopher; McCarthy, Michael C.

    2016-06-01

    Thionitrous acid (HSNO), a potential key intermediate in biological signaling pathways, has been proposed to link NO and H2S biochemistries. Its existence and stability in vivo, however, remain controversial. By means of Fourier-transform microwave spectroscopy, we establish that HSNO is spontaneously formed in high concentration when NO and H2S gases are simply mixed at room temperature in the presence of metallic surfaces. Our measurements reveal that HSNO is formed with high efficiency by the reaction H2S and N2O3 to produce HSNO and HNO2, where N2O3 is a product of NO disproportionation. These studies also suggest that further reaction of HSNO with H2S may form HNO and HSSH. The length of the S--N bond has been derived to high precision from isotopic studies, and is found to be unusually long, 1.84 Å -- the longest S--N bond reported to date for an SNO compound. The present structural and reactivity investigations of this elusive molecule provide a firm fundation to better understand its physiological chemistry and propensity to undergo S--N bond homolysis in vivo.

  15. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) for measurement of cytokine and growth factor mRNA expression with fluorogenic probes or SYBR Green I.

    PubMed

    Yin, J L; Shackel, N A; Zekry, A; McGuinness, P H; Richards, C; Putten, K V; McCaughan, G W; Eris, J M; Bishop, G A

    2001-06-01

    Real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) is the method of choice for rapid and reproducible measurements of cytokine or growth factor expression in small samples. Fluorescence detection methods for monitoring real-time PCR include fluorogenic probes labelled with reporter and quencher dyes, such as Taqman probes or Molecular Beacons and the dsDNA-binding dye SYBR Green I. Fluorogenic (Taqman) probes for a range of human and rat cytokines and growth factors were tested for sensitivity and compared with an assay for SYBR Green I quantification using real-time fluorescence monitoring (PE Applied Biosystems Model 7700 sequence detector). SYBR Green I detection involved analysis of the melting temperature of the PCR product and measurement of fluorescence at the optimum temperature. Fluorogenic probes provided sensitive and reproducible detection of targets that ranged from low (<10 copies/reaction) to high (>107 copies/ reaction) expression. SYBR Green I gave reproducible quantification when the target gene was expressed at moderate to high levels (> or =1000 copies/reaction), but did not give consistently reproducible quantification when the target gene was expressed at low levels. Although optimization of melting temperature improved the specificity of SYBR Green I detection, in our hands it did not equal the reproducible sensitivity and specificity of fluorogenic probes. The latter method is the first choice for measurement of low-level gene expression, although SYBR Green I is a simple and reproducible means to quantify genes that are expressed at moderate to high levels.

  16. Probing the Time Scale of FPOP (Fast Photochemical Oxidation of Proteins): Radical Reactions Extend Over Tens of Milliseconds

    NASA Astrophysics Data System (ADS)

    Vahidi, Siavash; Konermann, Lars

    2016-07-01

    Hydroxyl radical (ṡOH) labeling with mass spectrometry detection reports on protein conformations and interactions. Fast photochemical oxidation of proteins (FPOP) involves ṡOH production via H2O2 photolysis by UV laser pulses inside a flow tube. The experiments are conducted in the presence of a scavenger (usually glutamine) that shortens the ṡOH lifetime. The literature claims that FPOP takes place within 1 μs. This ultrafast time scale implies that FPOP should be immune to labeling-induced artifacts that may be encountered with other techniques. Surprisingly, the FPOP time scale has never been validated in direct kinetic measurements. Here we employ flash photolysis for probing oxidation processes under typical FPOP conditions. Bleaching of the reporter dye cyanine-5 (Cy5) served as readout of the time-dependent radical milieu. Surprisingly, Cy5 oxidation extends over tens of milliseconds. This time range is four orders of magnitude longer than expected from the FPOP literature. We demonstrate that the glutamine scavenger generates metastable secondary radicals in the FPOP solution, and that these radicals lengthen the time frame of Cy5 oxidation. Cy5 and similar dyes are widely used for monitoring the radical dose experienced by proteins in solution. The measured Cy5 kinetics thus strongly suggest that protein oxidation in FPOP extends over a much longer time window than previously thought (i.e., many milliseconds instead of one microsecond). The optical approach developed here should be suitable for assessing the performance of future FPOP-like techniques with improved temporal labeling characteristics.

  17. Probing the Time Scale of FPOP (Fast Photochemical Oxidation of Proteins): Radical Reactions Extend Over Tens of Milliseconds.

    PubMed

    Vahidi, Siavash; Konermann, Lars

    2016-07-01

    Hydroxyl radical (⋅OH) labeling with mass spectrometry detection reports on protein conformations and interactions. Fast photochemical oxidation of proteins (FPOP) involves ⋅OH production via H2O2 photolysis by UV laser pulses inside a flow tube. The experiments are conducted in the presence of a scavenger (usually glutamine) that shortens the ⋅OH lifetime. The literature claims that FPOP takes place within 1 μs. This ultrafast time scale implies that FPOP should be immune to labeling-induced artifacts that may be encountered with other techniques. Surprisingly, the FPOP time scale has never been validated in direct kinetic measurements. Here we employ flash photolysis for probing oxidation processes under typical FPOP conditions. Bleaching of the reporter dye cyanine-5 (Cy5) served as readout of the time-dependent radical milieu. Surprisingly, Cy5 oxidation extends over tens of milliseconds. This time range is four orders of magnitude longer than expected from the FPOP literature. We demonstrate that the glutamine scavenger generates metastable secondary radicals in the FPOP solution, and that these radicals lengthen the time frame of Cy5 oxidation. Cy5 and similar dyes are widely used for monitoring the radical dose experienced by proteins in solution. The measured Cy5 kinetics thus strongly suggest that protein oxidation in FPOP extends over a much longer time window than previously thought (i.e., many milliseconds instead of one microsecond). The optical approach developed here should be suitable for assessing the performance of future FPOP-like techniques with improved temporal labeling characteristics. Graphical Abstract ᅟ. PMID:27067899

  18. Pd0-mediated rapid cross-coupling reactions, the rapid C-[11C]methylations, revolutionarily advancing the syntheses of short-lived PET molecular probes.

    PubMed

    Suzuki, Masaaki; Doi, Hisashi; Koyama, Hiroko; Zhang, Zhouen; Hosoya, Takamitsu; Onoe, Hirotaka; Watanabe, Yasuyoshi

    2014-06-01

    Positron emission tomography is a noninvasive method for monitoring drug (or diagnostic) behavior and its localization on the target molecules in the living systems, including the human body, using a short-lived positron-emitting radionuclide. New methodologies for introducing representative short-lived radionuclides, (11)C and (18)F, into the carbon frameworks of biologically active organic compounds have been established by developing rapid C-[(11)C]methylations and C-[(18)F]fluoromethylations using rapid Pd(0)-mediated cross-coupling reactions between [(11)C]methyl iodide (sp(3)-hybridized carbon) and an excess amount of organotributylstannane or organoboronic acid ester having sp(2) (phenyl, heteroaromatic, or alkenyl), sp(alkynyl), or sp(3) (benzyl and cinnamyl)-hybridized carbons; and [(18)F]fluoromethyl halide (iodide or bromide) and an organoboronic acid ester, respectively. These rapid reactions provide a firm foundation for an efficient and general synthesis of short-lived (11)C- or (18)F-labeled PET molecular probes to promote in vivo molecular imaging studies.

  19. Glycolaldehyde as a probe molecule for biomass derivatives: reaction of C-OH and C═O functional groups on monolayer Ni surfaces.

    PubMed

    Yu, Weiting; Barteau, Mark A; Chen, Jingguang G

    2011-12-21

    Controlling the activity and selectivity of converting biomass derivatives to syngas (H(2) and CO) is critical for the utilization of biomass feedstocks as renewable sources for chemicals and fuels. One key chemistry in the conversion is the selective bond scission of the C-OH and C═O functionalities, which are present in many biomass derivatives. Because of the high molecular weight and low vapor pressure, it is relatively difficult to perform fundamental surface science studies of C6 sugars, such as glucose and fructose, using ultrahigh vacuum techniques. Glycolaldehyde (HOCH(2)CH═O) is the smallest molecule that contains both the C-OH and C═O functional groups, as well as the same C/O ratio as C6 sugars, and thus is selected as a probe molecule in the current study to determine how the presence of the C═O bond affects the reaction mechanism. Using a combination of density functional theory calculations and experimental measurements, our results indicate that the reaction pathway of glycolaldehyde to produce syngas can be enhanced by supporting monolayer Ni on a Pt substrate, which shows higher activity than either of the parent metals. Furthermore, the Pt substrate can be replaced by tungsten monocarbide to achieve similar activity and selectivity, indicating the possibility of using Ni/WC to replace Ni/Pt as active and selective catalysts with higher stability and lower cost. PMID:22066750

  20. Manipulating the charge state of Au clusters on rutile TiO2(110) single crystal surfaces through molecular reactions probed by infrared spectroscopy.

    PubMed

    Cao, Yunjun; Hu, Shujun; Yu, Min; Wang, Tingting; Huang, Shiming; Yan, Shishen; Xu, Mingchun

    2016-07-14

    The charge state of Au clusters deposited on rutile TiO2(110) single crystal surfaces was studied by UHV-FTIRS using CO as a probe. The as-deposited Au clusters on oxidized TiO2(110) surfaces are electrically neutral and are identified by the 2105-2112 cm(-1) vibrational frequency of adsorbed CO depending on Au coverage. Annealing Au/TiO2(110) in a moderate O2 atmosphere at 400 K blue shifts the CO vibrational frequency by only 2-3 cm(-1) both on bare TiO2(110) surfaces and on Au clusters. However, NO exposure blue shifts the CO vibrational frequency by 16-26 cm(-1) for CO adsorbed on Au atoms near the interface and by 3-4 cm(-1) for CO adsorbed on top of Au clusters. As the acceptors of the intense charge transfer from Au, the Oa atoms generated through (NO)2→ N2O + Oa reactions on the small fraction of the bare TiO2(110) surface reside around the Au/TiO2(110) interface perimeter, causing the neutral Au(0) to be cationic Au(δ+) states. This is a new approach to manipulate the charge state of Au clusters on oxide surfaces, which may be helpful in regulating the catalytic redox reactions on oxide supported metal systems.

  1. Glycolaldehyde as a Probe Molecule for Biomass Derivatives: Reaction of C-OH and C=O Functional Groups on Monolayer Ni Surfaces

    SciTech Connect

    Yu, Weiting; Barteau, Mark A.; Chen, Jingguang G.

    2011-12-21

    Controlling the activity and selectivity of converting biomass derivatives to syngas (H₂ and CO) is critical for the utilization of biomass feedstocks as renewable sources for chemicals and fuels. One key chemistry in the conversion is the selective bond scission of the C—OH and C=O functionalities, which are present in many biomass derivatives. Because of the high molecular weight and low vapor pressure, it is relatively difficult to perform fundamental surface science studies of C6 sugars, such as glucose and fructose, using ultrahigh vacuum techniques. Glycolaldehyde (HOCH₂CH=O) is the smallest molecule that contains both the C—OH and C=O functional groups, as well as the same C/O ratio as C6 sugars, and thus is selected as a probe molecule in the current study to determine how the presence of the C=O bond affects the reaction mechanism. Using a combination of density functional theory calculations and experimental measurements, our results indicate that the reaction pathway of glycolaldehyde to produce syngas can be enhanced by supporting monolayer Ni on a Pt substrate, which shows higher activity than either of the parent metals. Furthermore, the Pt substrate can be replaced by tungsten monocarbide to achieve similar activity and selectivity, indicating the possibility of using Ni/WC to replace Ni/Pt as active and selective catalysts with higher stability and lower cost.

  2. Time- and angle-resolved x-ray diffraction to probe structural and chemical evolution during Al-Ni intermetallic reactions.

    PubMed

    Yoo, Choong-Shik; Wei, Haoyan; Chen, Jing-Yin; Shen, Guoyin; Chow, Paul; Xiao, Yuming

    2011-11-01

    We present novel time- and angle-resolved x-ray diffraction (TARXD) capable of probing structural and chemical evolutions during rapidly propagating exothermic intermetallic reactions between Ni-Al multilayers. The system utilizes monochromatic synchrotron x-rays and a two-dimensional (2D) pixel array x-ray detector in combination of a fast-rotating diffraction beam chopper, providing a time (in azimuth) and angle (in distance) resolved x-ray diffraction image continuously recorded at a time resolution of ~30 μs over a time period of 3 ms. Multiple frames of the TARXD images can also be obtained with time resolutions between 30 and 300 μs over three to several hundreds of milliseconds. The present method is coupled with a high-speed camera and a six-channel optical pyrometer to determine the reaction characteristics including the propagation speed of 7.6 m/s, adiabatic heating rate of 4.0 × 10(6) K/s, and conductive cooling rate of 4.5 × 10(4) K/s. These time-dependent structural and temperature data provide evidences for the rapid formation of intermetallic NiAl alloy within 45 μs, thermal expansion coefficient of 1.1 × 10(-6) K for NiAl, and crystallization of V and Ag(3)In in later time. PMID:22128990

  3. Time- and angle-resolved x-ray diffraction to probe structural and chemical evolution during Al-Ni intermetallic reactions

    SciTech Connect

    Yoo, Choong-Shik; Wei, Haoyan; Chen, Jing-Yin; Shen, Guoyin; Chow, Paul; Xiao, Yuming

    2011-12-09

    We present novel time- and angle-resolved x-ray diffraction (TARXD) capable of probing structural and chemical evolutions during rapidly propagating exothermic intermetallic reactions between Ni-Al multilayers. The system utilizes monochromatic synchrotron x-rays and a two-dimensional (2D) pixel array x-ray detector in combination of a fast-rotating diffraction beam chopper, providing a time (in azimuth) and angle (in distance) resolved x-ray diffraction image continuously recorded at a time resolution of {approx}30 {micro}s over a time period of 3 ms. Multiple frames of the TARXD images can also be obtained with time resolutions between 30 and 300 {micro}s over three to several hundreds of milliseconds. The present method is coupled with a high-speed camera and a six-channel optical pyrometer to determine the reaction characteristics including the propagation speed of 7.6 m/s, adiabatic heating rate of 4.0 x 10{sup 6} K/s, and conductive cooling rate of 4.5 x 10{sup 4} K/s. These time-dependent structural and temperature data provide evidences for the rapid formation of intermetallic NiAl alloy within 45 {micro}s, thermal expansion coefficient of 1.1 x 10{sup -6} K for NiAl, and crystallization of V and Ag{sub 3}In in later time.

  4. IMPACT OF OXYGEN MEDIATED OXIDATIVE COUPLING ON ADSORPTION KINETICS

    EPA Science Inventory

    The presence of molecular oxygen in the test environment promotes oxidative coupling (polymer formation) of phenolic compounds on the surface of granular activated carbon (GAC). Both adsorption equilibria and adsorption kinetics are affected by these chemical reactions. Lack of...

  5. Polymerase chain reaction (PCR) and sequence specific oligonucleotide probes (SSOP) genotyping assay for detection of genes associated with rheumatoid arthritis and multiple sclerosis.

    PubMed

    Nikolaou, Konstantina; Kalatzis, Fanis G; Giannakeas, Nikolaos; Markoula, Sofia; Chatzikyriakidou, Anthi; Georgiou, Ioannis; Fotiadis, Dimitrios I

    2010-01-01

    In this paper an assay for the detection of genes associated with rheumatoid arthritis (RA) and multiple sclerosis, using polymerase chain reaction (PCR) and sequence specific oligonucleotide probes (SSOP) is presented, in order to be further applied in a portable Lab-On-Chip (LOC) device. A substantial part of these reagents were based on the literature (11th International Histocompatibility Workshop, IHW), bearing the advantage of proven successful implementation in genotyping, while others were designed for this study. More precisely, our methodology discriminates HLA-DRB1 as DRB1*01, *04 and *10, which include shared epitope (SE) alleles associated with RA and additionally DRB1*15 allele, including DRB1*1501 associated with MS (broad genotyping method). To further present the basic elements of the assay for high resolution genotyping of SE DRB1 alleles, we provide as an example the case of HLA-DRB1*10 alleles (HLADRB1* 100101, *100102, *100103, *1002 and *1003). Regarding the methodology for developing a detection assay, for SNPs associated with RA or MS the basic steps are presented. DNA sequence data are obtained from IMGT/HLA and SNP database. Online software tools are used to define hybridization specificity of primers and probes towards human DNA, leading to hybridization patterns that uniquely designate a target allele and evaluate parameters influencing PCR efficiency. Respecting current technological limitations of autonomous molecular-based LOC systems the approach of broad genotyping of HLA-DRB1*01/*04/*10/*15 genes, is intended to be initially used, leaving, high resolution genotyping of SE alleles for future implementations. This method is easy to be updated and extended to detect additional associated loci with RA or MS.

  6. Lowest Q2 Measurement of the γ*p→ Δ Reaction: Probing the Pionic Contribution

    SciTech Connect

    Stave, Sean C.

    2006-06-01

    The first excited state of the proton, the Delat, can be reached through a magnetic dipole spin flip of one of the quarks (M1) or through electric and Coulomb quadrupole terms (E2 and C2) which indicate a deviation from spherical symmetry. The quark models using the color hyperfine interaction underestimate the size of the quadrupole terms by more than an order of magnitude. Models using the pion cloud do a much better job of describing the data. This is expected due to the spontaneous breaking of chiral symmetry which leads to a cloud of virtual p wave pions which introduce the non-spherical amplitudes. The data presented in this work fill gaps in the low Q², long distance region where the pion cloud is expected to dominate and to produce significant Q2 variation. The p(e¯, ép)π° reaction was measured in the Δ region at Q² = 0.060 (GeV/c)², the lowest Q² to date for pion electroproduction, utilizing out-of-plane magnetic spectrometers at the Mainz Microtron in Germany. This work reports results for the dominant transition magnetic dipole amplitude and the quadrupole to dipole ratios obtained from fitting the new data with models using a three parameter, resonant multipole fit: M³/²1+ = (40.33 +- 0.63stat+syst +-model)(10-³/mπ+), E2/M1=Re(E³/²1+M³/²1+) = (-2.28+- 0.29stat+syst +- 0.20model)%, and C2/M1 =Re(S³/²1+/M³/²1+) poles disagree with predictions of the quark models but are in reasonable agreement with a chiral extrapolation of lattice QCD, chiral effective field theory and dynamical model results confirming the dominance and general Q² variation of the long range pionic contribution. While there is qualitative agreement with the models, there is no quantitative agreement thus indicating the need for further improvement of the models.

  7. Isolation of a Pseudomonas solanacearum-specific DNA probe by subtraction hybridization and construction of species-specific oligonucleotide primers for sensitive detection by the polymerase chain reaction.

    PubMed Central

    Seal, S E; Jackson, L A; Daniels, M J

    1992-01-01

    A subtraction hybridization technique was employed to make a library enriched for Pseudomonas solanacearum-specific sequences. One cloned fragment, PS2096, hybridized under stringent conditions to DNA of 82 P. solanacearum strains representing all subgroups of the species. Other plant-associated bacteria, including closely related species such as Pseudomonas capacia, Pseudomonas picketti, or Pseudomonas syzygii, did not hybridize to PS2096. A minimum number of between 4 x 10(5) and 4 x 10(6) P. solanacearum cells could routinely be detected with PS2096 labelled either with [32P]dCTP or with digoxigenin-11-dUTP. To improve the sensitivity of detection, PS2096 was sequenced to allow the construction of specific oligonucleotide primers to be used for polymerase chain reaction (PCR) amplification. After 50 cycles of amplification, 5 to 116 cells, depending on the strain, could reproducibly be detected by visualization of a 148-bp PCR product on an agarose gel. A preliminary field trial in Burundi with the probe and PCR primers has confirmed that they are sensitive tools for specifically detecting low-level infections of P. solanacearum in potato tubers. Images PMID:1482193

  8. Development of a TaqMan Probe-Based Insulated Isothermal Polymerase Chain Reaction (iiPCR) Assay for Detection of Fusarium oxysporum f. sp. cubense Race 4.

    PubMed

    Lin, Ying-Hong; Lin, Yi-Jia; Chang, Tsai-De; Hong, Li-Ling; Chen, Tzu-Yu; Chang, Pi-Fang Linda

    2016-01-01

    This study developed a novel and inexpensive detection method based on a TaqMan probe-based insulated isothermal polymerase chain reaction (iiPCR) method for the rapid detection of Panama disease caused by Fusarium oxysporum f. sp. cubense (Foc) race 4, which is currently among the most serious fungal vascular diseases worldwide. By using the portable POCKIT™ device with the novel primer set iiFoc-1/iiFoc-2, the Foc race 4 iiPCR assay (including DNA amplification and signal monitoring) could be completed within one hour. The developed Foc race 4 iiPCR assay is thus a user-friendly and efficient platform designed specifically for the detection of Foc race 4. The detection limit of this optimized Foc iiPCR system was estimated to be 1 copy of the target standard DNA as well as 1 fg of the Foc genomic DNA. This approach can serve as a rapid detection method for in planta detection of Foc race 4 in field-infected banana. It was concluded that this molecular detection procedure based on iiPCR has good potential for use as an efficient detection method. PMID:27448242

  9. Development of a TaqMan Probe-Based Insulated Isothermal Polymerase Chain Reaction (iiPCR) Assay for Detection of Fusarium oxysporum f. sp. cubense Race 4

    PubMed Central

    Lin, Yi-Jia; Chang, Tsai-De; Hong, Li-Ling; Chen, Tzu-Yu; Chang, Pi-Fang Linda

    2016-01-01

    This study developed a novel and inexpensive detection method based on a TaqMan probe-based insulated isothermal polymerase chain reaction (iiPCR) method for the rapid detection of Panama disease caused by Fusarium oxysporum f. sp. cubense (Foc) race 4, which is currently among the most serious fungal vascular diseases worldwide. By using the portable POCKIT™ device with the novel primer set iiFoc-1/iiFoc-2, the Foc race 4 iiPCR assay (including DNA amplification and signal monitoring) could be completed within one hour. The developed Foc race 4 iiPCR assay is thus a user-friendly and efficient platform designed specifically for the detection of Foc race 4. The detection limit of this optimized Foc iiPCR system was estimated to be 1 copy of the target standard DNA as well as 1 fg of the Foc genomic DNA. This approach can serve as a rapid detection method for in planta detection of Foc race 4 in field-infected banana. It was concluded that this molecular detection procedure based on iiPCR has good potential for use as an efficient detection method. PMID:27448242

  10. Facile synthesis of N-rich carbon quantum dots by spontaneous polymerization and incision of solvents as efficient bioimaging probes and advanced electrocatalysts for oxygen reduction reaction.

    PubMed

    Lei, Zhouyue; Xu, Shengjie; Wan, Jiaxun; Wu, Peiyi

    2016-01-28

    In this study, uniform nitrogen-doped carbon quantum dots (N-CDs) were synthesized through a one-step solvothermal process of cyclic and nitrogen-rich solvents, such as N-methyl-2-pyrrolidone (NMP) and dimethyl-imidazolidinone (DMEU), under mild conditions. The products exhibited strong light blue fluorescence, good cell permeability and low cytotoxicity. Moreover, after a facile post-thermal treatment, it developed a lotus seedpod surface-like structure of seed-like N-CDs decorating on the surface of carbon layers with a high proportion of quaternary nitrogen moieties that exhibited excellent electrocatalytic activity and long-term durability towards the oxygen reduction reaction (ORR). The peak potential was -160 mV, which was comparable to or even lower than commercial Pt/C catalysts. Therefore, this study provides an alternative facile approach to the synthesis of versatile carbon quantum dots (CDs) with widespread commercial application prospects, not only as bioimaging probes but also as promising electrocatalysts for the metal-free ORR.

  11. Deuterated carbohydrate probes as ‘label-free’ substrates for probing nutrient uptake in mycobacteria by nuclear reaction analysis† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c4cc09588j Click here for additional data file.

    PubMed Central

    Lowery, R.; Gibson, M. I.; Thompson, R. L.

    2015-01-01

    Understanding and probing small molecule uptake in cells is challenging, requiring sterically large chemical labels, or radioactive isotopes. Here, the uptake of deuterated sugars by Mycobacterium smegmatis, a non-pathogenic model of Mycobacterium tuberculosis, has been investigated using ion-beam (nuclear reaction) analysis demonstrating a new technique for label-free nutrient acquisition measurement. PMID:25695462

  12. A comprehensive comparative DFT study on adsorption and reactions involved in vinyl acetate synthesis from acetoxylation of ethylene on pure Pd(100) and Pd-Au(100): Elucidating the role of Au

    NASA Astrophysics Data System (ADS)

    Huang, Yanping; Dong, Xiuqin; Yu, Yingzhe; Zhang, Minhua

    2016-11-01

    Firstly, with DFT, electronic properties of Pd(100) and Pd-Au(100) were examined and it was found that addition of Au into Pd increases the electron density of Pd d-band. Besides, adsorption of relevant species involved in Samanos mechanism and Moiseev mechanism on Pd(100) and Pd-Au(100) was investigated and it was discovered that addition of Au impairs adsorption of species on metal surfaces. Finally, activation energies of all the reactions on Pd(100) and Pd-Au(100) were compared. Our calculations suggested that the rate-limiting step of the Samanos pathway on Pd(100) and Pd-Au(100) is the dehydrogenation of hydrogenated vinyl acetate. The rate-limiting step of the Moiseev pathway on Pd(100) is the coupling of vinyl with acetate, while that on Pd-Au(100) is the dehydrogenation of ethylene. The activation energies that are only involved in the Samanos mechanism become higher on Pd-Au(100) than on pure Pd(100), suggesting that alloying of Au is kinetically unfavorable for Samonos mechanism. Alloying of Au changes the rate-limiting step of Moiseev pathway, and Moiseev mechanism is preferred on Pd-Au(100).

  13. Determination of glyphosate and aminomethylphosphonic acid in aqueous soil matrices: a critical analysis of the 9-fluorenylmethyl chloroformate derivatization reaction and application to adsorption studies.

    PubMed

    Báez, María E; Fuentes, Edwar; Espina, María José; Espinoza, Jeannette

    2014-11-01

    The assessment of the environmental fate of glyphosate and its degradation product (aminomethylphosphonic acid) is of great interest given the widespread use of the herbicide. Studies of adsorption-desorption and transport processes in soils require analytical methods with sensitivity, accuracy, and precision suitable for determining the analytes in aqueous equilibrium solutions of varied complexity. In this work, the effect of factors on the yield of the derivatization of both compounds with 9-fluorenylmethyl chloroformate for applying in aqueous solutions derived from soils was evaluated through factorial experimental designs. Interference effects coming from background electrolytes and soil matrices were established. The whole method had a linear response up to 640 ng/mL (R(2) > 0.999) under optimized conditions for high-performance liquid chromatography with fluorescence detection. Limits of detection were 0.6 and 0.4 ng/mL for glyphosate and aminomethylphosphonic acid, respectively. The relative standard deviation was 4.4% for glyphosate (20 ng/mL) and 5.9% for aminomethylphosphonic acid (10 ng/mL). Adsorption of compounds on four different soils was assessed. Isotherm data fitted well the Freundlich model (R(2) > 0.97). Kf constants varied between 93 ± 3.1 and 2045 ± 157 for glyphosate and between 99 ± 4.1 and 1517 ± 56 (μg(1-1/) (n)  mL(1/) (n) ( ) g(-1) ) for aminomethylphosphonic acid, showing the broad range of applicability of the proposed method. PMID:25137606

  14. Determination of glyphosate and aminomethylphosphonic acid in aqueous soil matrices: a critical analysis of the 9-fluorenylmethyl chloroformate derivatization reaction and application to adsorption studies.

    PubMed

    Báez, María E; Fuentes, Edwar; Espina, María José; Espinoza, Jeannette

    2014-11-01

    The assessment of the environmental fate of glyphosate and its degradation product (aminomethylphosphonic acid) is of great interest given the widespread use of the herbicide. Studies of adsorption-desorption and transport processes in soils require analytical methods with sensitivity, accuracy, and precision suitable for determining the analytes in aqueous equilibrium solutions of varied complexity. In this work, the effect of factors on the yield of the derivatization of both compounds with 9-fluorenylmethyl chloroformate for applying in aqueous solutions derived from soils was evaluated through factorial experimental designs. Interference effects coming from background electrolytes and soil matrices were established. The whole method had a linear response up to 640 ng/mL (R(2) > 0.999) under optimized conditions for high-performance liquid chromatography with fluorescence detection. Limits of detection were 0.6 and 0.4 ng/mL for glyphosate and aminomethylphosphonic acid, respectively. The relative standard deviation was 4.4% for glyphosate (20 ng/mL) and 5.9% for aminomethylphosphonic acid (10 ng/mL). Adsorption of compounds on four different soils was assessed. Isotherm data fitted well the Freundlich model (R(2) > 0.97). Kf constants varied between 93 ± 3.1 and 2045 ± 157 for glyphosate and between 99 ± 4.1 and 1517 ± 56 (μg(1-1/) (n)  mL(1/) (n) ( ) g(-1) ) for aminomethylphosphonic acid, showing the broad range of applicability of the proposed method.

  15. Growth of Cu2ZnSnS4 Nanocrystallites on TiO2 Nanorod Arrays as Novel Extremely Thin Absorber Solar Cell Structure via the Successive-Ion-Layer-Adsorption-Reaction Method.

    PubMed

    Wang, Zhuoran; Demopoulos, George P

    2015-10-21

    Cu2ZnSnS4 (CZTS) is an environmentally benign semiconductor with excellent optoelectronic properties that attracts a lot of interest in thin film photovoltaics. In departure from that conventional configuration, we fabricate and test a novel absorber-conductor structure featuring in situ successive-ion-layer-adsorption-reaction (SILAR)-deposited CZTS nanocrystallites as a light absorber on one-dimensional TiO2 (rutile) nanorods as an electron conductor. The effectiveness of the nanoscale heterostructure in visible light harvesting and photoelectron generation is demonstrated with an initial short circuit current density of 3.22 mA/cm(2) and an internal quantum efficiency of ∼60% at the blue light region, revealing great potential in developing CZTS extremely thin absorber (ETA) solar cells. PMID:26422062

  16. Probing the orientation of electrostatically immobilized Protein G B1 by time-of-flight secondary ion spectrometry, sum frequency generation, and near-edge X-ray adsorption fine structure spectroscopy.

    PubMed

    Baio, Joe E; Weidner, Tobias; Baugh, Loren; Gamble, Lara J; Stayton, Patrick S; Castner, David G

    2012-01-31

    To fully develop techniques that provide an accurate description of protein structure at a surface, we must start with a relatively simple model system before moving to increasingly complex systems. In this study, X-ray photoelectron spectroscopy (XPS), sum frequency generation spectroscopy (SFG), near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to probe the orientation of Protein G B1 (6 kDa) immobilized onto both amine (NH(3)(+)) and carboxyl (COO(-)) functionalized gold. Previously, we have shown that we could successfully control orientation of a similar Protein G fragment via a cysteine-maleimide bond. In this investigation, to induce opposite end-on orientations, a charge distribution was created within the Protein G B1 fragment by first substituting specific negatively charged amino acids with neutral amino acids and then immobilizing the protein onto two oppositely charged self-assembled monolayer (SAM) surfaces (NH(3)(+) and COO(-)). Protein coverage, on both surfaces, was monitored by the change in the atomic % N, as determined by XPS. Spectral features within the SFG spectra, acquired for the protein adsorbed onto a NH(3)(+)-SAM surface, indicates that this electrostatic interaction does induce the protein to form an oriented monolayer on the SAM substrate. This corresponded to the polarization dependence of the spectral feature related to the NEXAFS N(1s)-to-π* transition of the β-sheet peptide bonds within the protein layer. ToF-SIMS data demonstrated a clear separation between the two samples based on the intensity differences of secondary ions stemming from amino acids located asymmetrically within Protein G B1 (methionine: 62 and 105 m/z; tyrosine: 107 and 137 m/z; leucine: 86 m/z). For a more quantitative examination of orientation, we developed a ratio comparing the sum of the intensities of secondary-ions stemming from the amino acid residues at either end

  17. Facile synthesis of N-rich carbon quantum dots by spontaneous polymerization and incision of solvents as efficient bioimaging probes and advanced electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Lei, Zhouyue; Xu, Shengjie; Wan, Jiaxun; Wu, Peiyi

    2016-01-01

    In this study, uniform nitrogen-doped carbon quantum dots (N-CDs) were synthesized through a one-step solvothermal process of cyclic and nitrogen-rich solvents, such as N-methyl-2-pyrrolidone (NMP) and dimethyl-imidazolidinone (DMEU), under mild conditions. The products exhibited strong light blue fluorescence, good cell permeability and low cytotoxicity. Moreover, after a facile post-thermal treatment, it developed a lotus seedpod surface-like structure of seed-like N-CDs decorating on the surface of carbon layers with a high proportion of quaternary nitrogen moieties that exhibited excellent electrocatalytic activity and long-term durability towards the oxygen reduction reaction (ORR). The peak potential was -160 mV, which was comparable to or even lower than commercial Pt/C catalysts. Therefore, this study provides an alternative facile approach to the synthesis of versatile carbon quantum dots (CDs) with widespread commercial application prospects, not only as bioimaging probes but also as promising electrocatalysts for the metal-free ORR.In this study, uniform nitrogen-doped carbon quantum dots (N-CDs) were synthesized through a one-step solvothermal process of cyclic and nitrogen-rich solvents, such as N-methyl-2-pyrrolidone (NMP) and dimethyl-imidazolidinone (DMEU), under mild conditions. The products exhibited strong light blue fluorescence, good cell permeability and low cytotoxicity. Moreover, after a facile post-thermal treatment, it developed a lotus seedpod surface-like structure of seed-like N-CDs decorating on the surface of carbon layers with a high proportion of quaternary nitrogen moieties that exhibited excellent electrocatalytic activity and long-term durability towards the oxygen reduction reaction (ORR). The peak potential was -160 mV, which was comparable to or even lower than commercial Pt/C catalysts. Therefore, this study provides an alternative facile approach to the synthesis of versatile carbon quantum dots (CDs) with widespread

  18. Adsorption kinetics of methyl violet onto perlite.

    PubMed

    Doğan, Mehmet; Alkan, Mahir

    2003-01-01

    This study examines adsorption kinetics and activation parameters of methyl violet on perlite. The effect of process parameters like contact time, concentration of dye, temperature and pH on the extent of methyl violet adsorption from solution has been investigated. Results of the kinetic studies show that the adsorption reaction is first order with respect to dye solution concentration with activation energy of 13.2 kJ mol(-1). This low activation energy value indicates that the adsorption reaction is diffusion controlled. The activation parameters using Arrhenius and Eyring equations have been calculated. Adsorption increases with increase of variables such as contact time, initial dye concentration, temperature and pH.

  19. Investigation of the electrochemical reactions at a limited-contact La1-xSrxMnO3/Y-doped ZrO2 interface with a rod-type ionic-probe

    NASA Astrophysics Data System (ADS)

    Ji, Ho-Il; Hong, Jongsup; Yoon, Kyung Joong; Son, Ji-Won; Kim, Byung-Kook; Lee, Hae-Weon; Lee, Jong-Ho

    2016-10-01

    A more quantitatively controllable triple phase boundary (TPB) of a lanthanum strontium manganite/yttria-stabilized zirconia (LSM/YSZ) interface was constructed by using an YSZ ionic probe with well-defined dimensions. A bar-shaped, dense YSZ sintered body was employed as an ionic probe and embedded in the pellet-shaped, dense LSM bulk. The TPB length of the LSM/YSZ interface can be simply determined from the circumference of the YSZ bars. To identify the reaction mechanism of the oxygen reduction reaction (ORR) at the TPB of the LSM/YSZ interface, limited-contact AC impedance spectroscopy was used; this distinguished the LSM/YSZ interface related polarization from other polarizations present in the Pt/LSM/YSZ/Pt electrochemical cell. By analyzing the electrode-related polarizations in the electrochemical cell with the geometrically quantified YSZ ionic probe, the rate determining step of the ORR was the diffusion of adsorbed oxygen along the LSM bulk surface. In this paper, emphasis is placed on the experimental versatility and the limitations of our designed electrochemical analysis with bar-shaped ionic probes.

  20. Adsorption of phenolic compound by aged-refuse.

    PubMed

    Xiaoli, Chai; Youcai, Zhao

    2006-09-01

    The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic.

  1. Protein Adsorption in Three Dimensions

    PubMed Central

    Vogler, Erwin A.

    2011-01-01

    Recent experimental and theoretical work clarifying the physical chemistry of blood-protein adsorption from aqueous-buffer solution to various kinds of surfaces is reviewed and interpreted within the context of biomaterial applications, especially toward development of cardiovascular biomaterials. The importance of this subject in biomaterials surface science is emphasized by reducing the “protein-adsorption problem” to three core questions that require quantitative answer. An overview of the protein-adsorption literature identifies some of the sources of inconsistency among many investigators participating in more than five decades of focused research. A tutorial on the fundamental biophysical chemistry of protein adsorption sets the stage for a detailed discussion of the kinetics and thermodynamics of protein adsorption, including adsorption competition between two proteins for the same adsorbent immersed in a binary-protein mixture. Both kinetics and steady-state adsorption can be rationalized using a single interpretive paradigm asserting that protein molecules partition from solution into a three-dimensional (3D) interphase separating bulk solution from the physical-adsorbent surface. Adsorbed protein collects in one-or-more adsorbed layers, depending on protein size, solution concentration, and adsorbent surface energy (water wettability). The adsorption process begins with the hydration of an adsorbent surface brought into contact with an aqueous-protein solution. Surface hydration reactions instantaneously form a thin, pseudo-2D interface between the adsorbent and protein solution. Protein molecules rapidly diffuse into this newly-formed interface, creating a truly 3D interphase that inflates with arriving proteins and fills to capacity within milliseconds at mg/mL bulk-solution concentrations CB. This inflated interphase subsequently undergoes time-dependent (minutes-to-hours) decrease in volume VI by expulsion of either-or-both interphase water and

  2. Degradation of methyl bromide and methyl chloride in soil microcosms: Use of stable C isotope fractionation and stable isotope probing to identify reactions and the responsible microorganisms

    NASA Astrophysics Data System (ADS)

    Miller, Laurence G.; Warner, Karen L.; Baesman, Shaun M.; Oremland, Ronald S.; McDonald, Ian R.; Radajewski, Stefan; Murrell, J. Colin

    2004-08-01

    Bacteria in soil microcosm experiments oxidized elevated levels of methyl chloride (MeCl) and methyl bromide (MeBr), the former compound more rapidly than the latter. MeBr was also removed by chemical reactions while MeCl was not. Chemical degradation dominated the early removal of MeBr and accounted for more than half of its total loss. Fractionation of stable carbon isotopes during chemical degradation of MeBr resulted in a kinetic isotope effect (KIE) of 59 ± 7‰. Soil bacterial oxidation dominated the later removal of MeBr and MeCl and was characterized by different KIEs for each compound. The KIE for MeBr oxidation was 69 ± 9‰ and the KIE for MeCl oxidation was 49 ± 3‰. Stable isotope probing revealed that different populations of soil bacteria assimilated added 13C-labeled MeBr and MeCl. The identity of the active MeBr and MeCl degrading bacteria in soil was determined by analysis of 16S rRNA gene sequences amplified from 13C-DNA fractions, which identified a number of sequences from organisms not previously thought to be involved in methyl halide degradation. These included Burkholderia, the major clone type in the 13C-MeBr fraction, and Rhodobacter, Lysobacter and Nocardioides the major clone types in the 13C-MeCl fraction. None of the 16S rRNA gene sequences for methyl halide oxidizing bacteria currently in culture (including Aminobacter strain IMB-1 isolated from fumigated soil) were identified. Functional gene clone types closely related to Aminobacter spp. were identified in libraries containing the sequences for the cmuA gene, which codes for the enzyme known to catalyze the initial step in the oxidation of MeBr and MeCl. The cmuA gene was limited to members of the alpha-Proteobacteria whereas the greater diversity demonstrated by the 16S rRNA gene may indicate that other enzymes catalyze methyl halide oxidation in different groups of bacteria.

  3. Degradation of methyl bromide and methyl chloride in soil microcosms: Use of stable C isotope fractionation and stable isotope probing to identify reactions and the responsible microorganisms

    USGS Publications Warehouse

    Miller, L.G.; Warner, K.L.; Baesman, S.M.; Oremland, R.S.; McDonald, I.R.; Radajewski, S.; Murrell, J.C.

    2004-01-01

    Bacteria in soil microcosm experiments oxidized elevated levels of methyl chloride (MeCl) and methyl bromide (MeBr), the former compound more rapidly than the latter. MeBr was also removed by chemical reactions while MeCl was not. Chemical degradation dominated the early removal of MeBr and accounted for more than half of its total loss. Fractionation of stable carbon isotopes during chemical degradation of MeBr resulted in a kinetic isotope effect (KIE) of 59 ?? 7???. Soil bacterial oxidation dominated the later removal of MeBr and MeCl and was characterized by different KIEs for each compound. The KIE for MeBr oxidation was 69 ?? 9??? and the KIE for MeCl oxidation was 49 ?? 3???. Stable isotope probing revealed that different populations of soil bacteria assimilated added 13C-labeled MeBr and MeCl. The identity of the active MeBr and MeCl degrading bacteria in soil was determined by analysis of 16S rRNA gene sequences amplified from 13C-DNA fractions, which identified a number of sequences from organisms not previously thought to be involved in methyl halide degradation. These included Burkholderia , the major clone type in the 13C-MeBr fraction, and Rhodobacter, Lysobacter and Nocardioides the major clone types in the 13C-MeCl fraction. None of the 16S rRNA gene sequences for methyl halide oxidizing bacteria currently in culture (including Aminobacter strain IMB-1 isolated from fumigated soil) were identified. Functional gene clone types closely related to Aminobacter spp. were identified in libraries containing the sequences for the cmuA gene, which codes for the enzyme known to catalyze the initial step in the oxidation of MeBr and MeCl. The cmuA gene was limited to members of the alpha-Proteobacteria whereas the greater diversity demonstrated by the 16S rRNA gene may indicate that other enzymes catalyze methyl halide oxidation in different groups of bacteria. Copyright ?? 2004 Elsevier Ltd.

  4. Characterization of micro- and mesoporous materials using accelerated dynamics adsorption.

    PubMed

    Qajar, Ali; Peer, Maryam; Rajagopalan, Ramakrishnan; Foley, Henry C

    2013-10-01

    Porosimetry is a fundamental characterization technique used in development of new porous materials for catalysis, membrane separation, and adsorptive gas storage. Conventional methods like nitrogen and argon adsorption at cryogenic temperatures suffer from slow adsorption dynamics especially for microporous materials. In addition, CO2, the other common probe, is only useful for micropore characterization unless being compressed to exceedingly high pressures to cover all required adsorption pressures. Here, we investigated the effect of adsorption temperature, pressure, and type of probe molecule on the adsorption dynamics. Methyl chloride (MeCl) was used as the probe molecule, and measurements were conducted near room temperature under nonisothermal condition and subatmospheric pressure. A pressure control algorithm was proposed to accelerate adsorption dynamics by manipulating the chemical potential of the gas. Collected adsorption data are transformed into pore size distribution profiles using the Horvath-Kavazoe (HK), Saito-Foley (SF), and modified Kelvin methods revised for MeCl. Our study shows that the proposed algorithm significantly speeds up the rate of data collection without compromising the accuracy of the measurements. On average, the adsorption rates on carbonaceous and aluminosilicate samples were accelerated by at least a factor of 4-5. PMID:23919893

  5. XPS, EXAFS, and FTIR as tools to probe the unexpected adsorption-coupled reduction of U(VI) to U(V) and U(IV) on Borassus flabellifer-based adsorbents.

    PubMed

    Kushwaha, S; Sreedhar, B; Padmaja, P

    2012-11-20

    Palm shell-based adsorbents prepared under five different thermochemical conditions and palm shell powder have been shown to be quite effective for removal of uranium from aqueous solutions. X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and Fourier transform infrared spectroscopy (FTIR) have been used to determine information about the speciation and binding of uranium on the adsorbents under study. Studies indicate that the uranium which is present as uranyl ion in aqueous solution is present in mixed valence states (U(IV), U(V), and U(VI)) when it is bound to the adsorbents. The mechanism of adsorption is likely to be adsorption-coupled reduction as well as complexation. Adsorption of uranium, cesium, and iron was found to be quantitative in binary as well as ternary mixtures.

  6. The adsorption of NO and reaction of NO with O{sub 2} on H-, NaH-, CuH-, and Cu-ZSM-5: An in situ FTIR investigation

    SciTech Connect

    Szanyi, J.; Paffett, M.T.

    1996-11-01

    The adsorption of NO and the reaction of NO with O{sub 2} on H-, NaH-, CuH-, and Cu-ZSM-5 zeolites were studied at 300 K using in situ Fourier transform infrared spectroscopy (FTIR). At this temperature, NO readily adsorbs on the Cu{sup +} sites of CuH- and Cu-ZSM-5 catalysts and decomposition of NO is observed for all catalysts, although the rate of decomposition is vastly different on these materials. In comparison, this reaction is negligible over the H- and NaH-ZSM-5 samples. The time evolution of several nitrogen-containing molecules after controlled O{sub 2} exposure to the NO/ZSM-5 systems has allowed the spectral correlation of these species. These nitrogen-containing species can interact with either the protonic sites of bridging hydroxyls forming hydrogen bonding complexes or the metal cations producing primarily surface nitrates and nitrites. The hydrogen bonded N{sub x}O{sub y} complexes were characterized with their IR absorption features: (1) NO{sub 2}, 2133 cm{sup {minus}1}; (b) N{sub 2}O{sub 3}, 1875 and 1587 cm{sup {minus}1}; and (c) N{sub 2}O{sub 4}, 2185 and 1745 cm{sup {minus}1}. The stretching vibrational frequency of the acidic OH groups of ZSM-5 red-shifts due to the interaction with nitrogen-containing molecules and forms {open_quotes}ABC{close_quotes} band structures characteristic of medium and strong hydrogen bonding complexes. Although the adsorbed N{sub x}O{sub y} species (N{sub 2}O{sub 3}, N{sub 2}O{sub 4}) interacting with the Bronsted protons exhibit characteristics of a strong Lewis base, adsorption enthalpies are sufficiently weak that their existence is not observed even after brief evacuation. Nitric oxide, oxygen coadsorption produces metal cation (Na{sup +} and Cu{sup n+}) bonded surface species possessing IR absorption bands between 1400 and 1650 cm{sup {minus}1} characteristic of nitrite and nitrate species. 46 refs., 9 figs.

  7. Universal tight binding model for chemical reactions in solution and at surfaces. III. Stoichiometric and reduced surfaces of titania and the adsorption of water

    SciTech Connect

    Lozovoi, A. Y.; Sheppard, T. J.; Kohanoff, J. J.; Pashov, D. L.; Paxton, A. T.

    2014-07-28

    We demonstrate a model for stoichiometric and reduced titanium dioxide intended for use in molecular dynamics and other atomistic simulations and based in the polarizable ion tight binding theory. This extends the model introduced in two previous papers from molecular and liquid applications into the solid state, thus completing the task of providing a comprehensive and unified scheme for studying chemical reactions, particularly aimed at problems in catalysis and electrochemistry. As before, experimental results are given priority over theoretical ones in selecting targets for model fitting, for which we used crystal parameters and band gaps of titania bulk polymorphs, rutile and anatase. The model is applied to six low index titania surfaces, with and without oxygen vacancies and adsorbed water molecules, both in dissociated and non-dissociated states. Finally, we present the results of molecular dynamics simulation of an anatase cluster with a number of adsorbed water molecules and discuss the role of edge and corner atoms of the cluster.

  8. Universal tight binding model for chemical reactions in solution and at surfaces. III. Stoichiometric and reduced surfaces of titania and the adsorption of water

    NASA Astrophysics Data System (ADS)

    Lozovoi, A. Y.; Pashov, D. L.; Sheppard, T. J.; Kohanoff, J. J.; Paxton, A. T.

    2014-07-01

    We demonstrate a model for stoichiometric and reduced titanium dioxide intended for use in molecular dynamics and other atomistic simulations and based in the polarizable ion tight binding theory. This extends the model introduced in two previous papers from molecular and liquid applications into the solid state, thus completing the task of providing a comprehensive and unified scheme for studying chemical reactions, particularly aimed at problems in catalysis and electrochemistry. As before, experimental results are given priority over theoretical ones in selecting targets for model fitting, for which we used crystal parameters and band gaps of titania bulk polymorphs, rutile and anatase. The model is applied to six low index titania surfaces, with and without oxygen vacancies and adsorbed water molecules, both in dissociated and non-dissociated states. Finally, we present the results of molecular dynamics simulation of an anatase cluster with a number of adsorbed water molecules and discuss the role of edge and corner atoms of the cluster.

  9. Mechanism of the reaction, CH4+O(1D2)→CH3+OH, studied by ultrafast and state-resolved photolysis/probe spectroscopy of the CH4ṡO3 van der Waals complex

    NASA Astrophysics Data System (ADS)

    Miller, C. Cameron; van Zee, Roger D.; Stephenson, John C.

    2001-01-01

    The mechanism of the reaction CH4+O(1D2)→CH3+OH was investigated by ultrafast, time-resolved and state-resolved experiments. In the ultrafast experiments, short ultraviolet pulses photolyzed ozone in the CH4ṡO3 van der Waals complex to produce O(1D2). The ensuing reaction with CH4 was monitored by measuring the appearance rate of OH(v=0,1;J,Ω,Λ) by laser-induced fluorescence, through the OH A←X transition, using short probe pulses. These spectrally broad pulses, centered between 307 and 316 nm, probe many different OH rovibrational states simultaneously. At each probe wavelength, both a fast and a slow rise time were evident in the fluorescence signal, and the ratio of the fast-to-slow signal varied with probe wavelength. The distribution of OH(v,J,Ω,Λ) states, Pobs(v,J,Ω,Λ), was determined by laser-induced fluorescence using a high-resolution, tunable dye laser. The Pobs(v,J,Ω,Λ) data and the time-resolved data were analyzed under the assumption that different formation times represent different reaction mechanisms and that each mechanism produces a characteristic rovibrational distribution. The state-resolved and the time-resolved data can be fit independently using a two-mechanism model: Pobs(v,J,Ω,Λ) can be decomposed into two components, and the appearance of OH can be fit by two exponential rise times. However, these independent analyses are not mutually consistent. The time-resolved and state-resolved data can be consistently fit using a three-mechanism model. The OH appearance signals, at all probe wavelengths, were fit with times τfast≈0.2 ps, τinter≈0.5 ps and τslow≈5.4 ps. The slowest of these three is the rate for dissociation of a vibrationally excited methanol intermediate (CH3OH*) predicted by statistical theory after complete intramolecular energy redistribution following insertion of O(1D2) into CH4. The Pobs(v,J,Ω,Λ) was decomposed into three components, each with a linear surprisal, under the assumption that the

  10. Adsorption kinetics and dynamics in Si(100) epitaxial growth and oxidation

    NASA Astrophysics Data System (ADS)

    Ferguson, Bradley Alan

    Molecular beam surface science techniques have been employed to probe the adsorption kinetics and dynamics of disilane and oxygen on Si(100)-2 x 1. In particular, the beam reflectivity method of King and Wells was used to measure reaction probabilities over a wide range of incident translational energies, incident angles, and surface temperatures. Oxygen is shown to chemisorb on Si(100) via two distinct adsorption mechanisms: trapping-mediated and direct chemisorption. In the low kinetic energy range, the adsorption probability is found to decrease strongly with increasing surface temperature and kinetic energy, which are trends consistent with a trapping-mediated mechanism. A simple mathematical model for trapping-mediated chemisorption fits the data in this range quite well. Trapping probabilities can be estimated from the data using the model, and decrease with increasing kinetic energy, as would be expected. In the high kinetic energy range, the chemisorption probability increases strongly with increasing kinetic energy, which is a defining characteristic of direct chemisorption. The molecular beam adsorption probability measurements are convoluted with a Maxwell-Boltzmann distribution of incident kinetic energies and angles to predict the average adsorption probability of a thermalized gas. From these calculations, the trapping-mediated mechanism dominates adsorption at low temperatures, while the direct mechanism takes over as the temperature is raised. The adsorption probability of disilane was measured over a wide range of conditions as well. The trapping-mediated and direct chemisorption mechanisms are also shown to be active in this system. However, the trapping probability in this system is much higher over a wider range of kinetic energies, primarily due to an increased physical adsorption binding energy. Also, the effect of surface hydrogen coverage on the chemisorption probability was investigated, and was found to obey a simple second order kinetic

  11. Protein Adsorption in Three Dimensions

    PubMed Central

    Vogler, Erwin A.

    2011-01-01

    Recent experimental and theoretical work clarifying the physical chemistry of blood-protein adsorption from aqueous-buffer solution to various kinds of surfaces is reviewed and interpreted within the context of biomaterial applications, especially toward development of cardiovascular biomaterials. The importance of this subject in biomaterials surface science is emphasized by reducing the “protein-adsorption problem” to three core questions that require quantitative answer. An overview of the protein-adsorption literature identifies some of the sources of inconsistency among many investigators participating in more than five decades of focused research. A tutorial on the fundamental biophysical chemistry of protein adsorption sets the stage for a detailed discussion of the kinetics and thermodynamics of protein adsorption, including adsorption competition between two proteins for the same adsorbent immersed in a binary-protein mixture. Both kinetics and steady-state adsorption can be rationalized using a single interpretive paradigm asserting that protein molecules partition from solution into a three-dimensional (3D) interphase separating bulk solution from the physical-adsorbent surface. Adsorbed protein collects in one-or-more adsorbed layers, depending on protein size, solution concentration, and adsorbent surface energy (water wettability). The adsorption process begins with the hydration of an adsorbent surface brought into contact with an aqueous-protein solution. Surface hydration reactions instantaneously form a thin, pseudo-2D interface between the adsorbent and protein solution. Protein molecules rapidly diffuse into this newly-formed interface, creating a truly 3D interphase that inflates with arriving proteins and fills to capacity within milliseconds at mg/mL bulk-solution concentrations CB. This inflated interphase subsequently undergoes time-dependent (minutes-to-hours) decrease in volume VI by expulsion of either-or-both interphase water and

  12. Identification of tuna species in commercial cans by minor groove binder probe real-time polymerase chain reaction analysis of mitochondrial DNA sequences.

    PubMed

    Terio, Valentina; Di Pinto, Pietro; Decaro, Nicola; Parisi, Antonio; Desario, Costantina; Martella, Vito; Buonavoglia, Canio; Tantillo, Marilia Giuseppina

    2010-12-01

    Three different minor groove binder (MGB) probe assays have been developed for rapid and accurate identification of the species commonly used for production of canned tuna, i.e. yellowfin (Thunnus albacares), bluefin (Thunnus thynnus) and albacore (Thunnus alalunga) tunas. The assays targeting the mitochondrial cytochrome b gene were able to discriminate efficiently between the three species contained in fresh or canned tunas and did not react with other Scombroidei that were tested. A correct species prediction was obtained even from artificial mixtures prepared with different amounts of the reference tuna species and subjected to the sterilisation treatment. Testing of 27 commercial canned tunas by PCR-RFLP, MGB probe assays and sequence analysis showed a concordance of 100% between the last two techniques, whereas by using PCR-RFLP several samples were uncharacterised or mischaracterised. These results make the established MGB probe assays an attractive tool for direct and rapid species identification in canned tuna. PMID:20691254

  13. Adsorption of thorium from aqueous solutions by perlite.

    PubMed

    Talip, Z; Eral, M; Hiçsönmez, U

    2009-02-01

    The use of expanded perlite for the adsorption of thorium from aqueous solution by batch technique is presented. The effects of particle size, pH of the solution, initial thorium concentration, shaking time, V/m ratio and temperature were determined. It was found that the adsorption capacity increases by the increase in the pH of the suspensions. The rate of thorium adsorption on expanded perlite was observed to be fast in the first hour of the reaction time. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models and the adsorption experiments conducted at 30 +/- 1 degrees C showed that the adsorption isotherms correlated well with the Langmuir model. From the adsorption data, thermodynamic parameters such as DeltaG(o), DeltaH(o) and DeltaS(o) were calculated as a function of temperature.

  14. The reaction of atomic oxygen with Si(100) and Si(111). II. Adsorption, passive oxidation and the effect of coincident ion bombardment

    NASA Astrophysics Data System (ADS)

    Engstrom, J. R.; Bonser, D. J.; Engel, Thomas

    The reactions of atomic oxygen with the (100) and (111) surfaces of silicon have been investigated by employing supersonic molecular beam techniques, X-ray photoelectron spectroscopy (XPS), and low-energy ion scattering spectroscopy (ISS). Atomic oxygen adsorbs with unit probability on the clean silicon surface, independent of substrate temperature (110-800 K) and incident mean translational energy (3-16 kcal mol -1). Oxidation of clean silicon with an oxygen atom beam is characterized by wo stages: a "fast" stage that corresponds to oxygen chemisorption in the topmost 2-3 silicon layers; and a "slow" stage that corresponds to oxygen incorporation and oxide film growth. The chemisorption stage is described by first-order Langmuirian kinetics with an apparent saturation coverage of approximately 4 ML O(a), the oxide growth stage by lddirect" logarithmic kinetics, where d x/d t = α exp(- x/ L), where x is the oxide thickness. Observation of significant oxidation at substrate temperatures of 110 K suggests that oxie growth in the slow stage may occur bya field-assisted mechanism, where an internal electric field aids transport of oxygen to the underlying silicon substrate layers. XPS and ISS results support a two-dimensional layer-by-layer growth mechanism for oxidation at substrate temperatures below 900 K. At higher temperatures, T ≥ 1050 K, oxide growth is three-dimensional involving nucleation and growth of bulk-like oxide islands even for mean coverages as low as 3 ML O(a). ISS results lend support to the formation of "on-top" adsorbed oxygen atoms that cap silicon dangling bonds at the oxide/gas interface. Coincident bombardment of the silicon substrate with an Ar - ion beam leads to an enhanced rate of oxidation. The enhancement can be understood in terms of a model involving secondary implantation of adsorbed oxygen atoms, coupled with the simultaneous formation of reactive sites (e.g., dangling bonds, vacancies) for oxygen chemisorption. The effect of

  15. Al atom on MoO3(010) surface: adsorption and penetration using density functional theory.

    PubMed

    Wu, Hong-Zhang; Bandaru, Sateesh; Wang, Da; Liu, Jin; Lau, Woon Ming; Wang, Zhenling; Li, Li-Li

    2016-03-14

    Interfacial issues, such as the interfacial structure and the interdiffusion of atoms at the interface, are fundamental to the understanding of the ignition and reaction mechanisms of nanothermites. This study employs first-principle density functional theory to model Al/MoO3 by placing an Al adatom onto a unit cell of a MoO3(010) slab, and to probe the initiation of interfacial interactions of Al/MoO3 nanothermite by tracking the adsorption and subsurface-penetration of the Al adatom. The calculations show that the Al adatom can spontaneously go through the topmost atomic plane (TAP) of MoO3(010) and reach the 4-fold hollow adsorption-site located below the TAP, with this subsurface adsorption configuration being the most preferred one among all plausible adsorption configurations. Two other plausible configurations place the Al adatom at two bridge sites located above the TAP of MoO3(010) but the Al adatom can easily penetrate below this TAP to a relatively more stable adsorption configuration, with a small energy barrier of merely 0.2 eV. The evidence of subsurface penetration of Al implies that Al/MoO3 likely has an interface with intermixing of Al, Mo and O atoms. These results provide new insights on the interfacial interactions of Al/MoO3 and the ignition/combustion mechanisms of Al/MoO3 nanothermites.

  16. Probing of enzyme reactions by the biocatalyst-induced association or dissociation of redox labels linked to monolayer-functionalized electrodes.

    PubMed

    Li, Di; Gill, Ron; Freeman, Ronit; Willner, Itamar

    2006-12-28

    The activities of the enzymes tyrosinase and thrombin are probed by the association of the ferrocene boronic acid label to the enzyme-generated catechol ligand, and by the cleavage of the ligand-redox complex tethered to a peptide, respectively.

  17. Adsorption of basic dyes from aqueous solution onto pumice powder.

    PubMed

    Akbal, Feryal

    2005-06-15

    The adsorption of methylene blue and crystal violet on pumice powder samples of varying compositions was investigated using a batch adsorption technique. The effects of various experimental parameters, such as adsorbent dosage, initial dye concentration, and contact time, were also investigated. The extent of dye removal increased with decreased initial concentration of the dye and also increased with increased contact time and amount of adsorbent used. Adsorption data were modeled using the Freundlich adsorption isotherm. The adsorption kinetic of methylene blue and crystal violet could be described by the pseudo-second-order reaction model.

  18. [Fluoride adsorption form drinking water by granular lanthanum alginate].

    PubMed

    Huo, Ya-Kun; Ding, Wen-Ming; Huang, Xia

    2010-11-01

    Granular lanthanum alginate was prepared by dripping solved sodium alginate into lanthanum chloride solution. After washed and dried, sorbent with 1-1.5 mm diameter, 25% (mass fraction) La content was made and applied for fluoride removal from drinking test. Adsorption performance such as adsorption rate, adsorption isotherm, pH and disturbing ions effects were tested in batch adsorption. The changes of adsorbent surface and the solution composition before and after adsorption were also studied. Results showed that the adsorption rate was fast, fluoride concentration trend to stable after 2h reaction, and the adsorption rate fit for pseudo second order equation. The adsorption was significantly affected by pH and some disturbing ions, optimum pH = 4, phosphate and carbonate reduced adsorption. Adsorption isotherm fitted Langmuir equation well; the max adsorption capacity was 197.2 mg x g(-1). SEM photographs of sorbent before and after adsorption showed significantly different surface morphology; EDX composition analysis of sorbent surface and solution concentration changes before and after adsorption showed that ion exchange take placed between solution F- and sorbent surface Cl- and OH-.

  19. Practical Prediction of Ten Common Streptococcus pneumoniae Serotypes/Serogroups in One PCR Reaction by Multiplex Ligation-Dependent Probe Amplification and Melting Curve (MLPA-MC) Assay in Shenzhen, China

    PubMed Central

    Zheng, Lei; Zou, Jianhua; Jin, Ping; Hu, Yanwei; Kudinha, Timothy; Kong, Fanrong; Chen, Xu; Wang, Qian

    2015-01-01

    Background Streptococcus pneumoniae has more than 95 distinct serotypes described to date. However, only certain serotypes are more likely to cause pneumococcal diseases. Thus serotype surveillance is important for vaccine formula design as well as in post-vaccine serotype shift monitor. The goal of this study was to develop a practical screening assay for ten Shenzhen China common pneumococcal serotypes/serogroups in one molecular reaction. Methods A molecular assay, based on multiplex ligation-dependent probe amplification (MLPA) and melting curve (MC) analysis, was developed in an integrated approach (MLPA-MC) for the detection of ten capsular serotypes/serogroups 4, 6 (6A/6B/6C/6D), 9V/9A, 14, 15F/15A, 15B/15C, 18 (18F/18A/18B/18C), 19F, 19A and 23F. We designed serotype/serogroup-specific MLPA probes and fluorescent detection probes to discriminate the different serotypes/serogroups in one molecular reaction. The three steps of MLPA-MC assay are continuous reactions in one well detected by LightCycler 480. A total of 210 S. pneumoniae isolates from our local Maternity and Child Health Hospital were randomly chosen to evaluate the assay against published multiplex PCR assays. Results Our results showed that 198 (94.3%) of S. pneumoniae isolates were type-able by our assays and the results were in complete concordance with the published multiplex PCRs. Using the MLPA-MC assay, 96 S. pneumoniae isolates could be typed within 3 hours with limited hands-on time. This serotype/serogroup-screening assay can be easily modified or extended by modification of the serotype/serogroup-specific MLPA probes combinations according to the needs of different laboratories. Conclusions We recommend use of this assay as a starting point for screening serotype/serogroup frequencies. There is a need for this assay to be combined with other molecular typing assays, like published serotype specific PCRs, or even the Quellung reaction for serotype confirmation. PMID:26151828

  20. Probing the Adsorption Behavior of 4,5-Diazafluoren-9-one and Its Schiff Base Derivatives on SIlver and Gold Nanosurfaces Using Raman Spectroscopy, Density Functional Theory and Potential Energy Distribution Calculations

    NASA Astrophysics Data System (ADS)

    McCoy, Rhonda Patrice

    from the center ring was shortened because of metal-ligand coordination. These observations are correlated to the shifts in Raman frequencies; a decrease in bond length resulted in a shift to a higher vibrational energy. The surface-enhanced Raman spectrum of DAFO was obtained on silver colloids and gold nanorods. The resulting SER spectra were compared to their corresponding normal Raman spectra, there were changes in relative band intensities and there were bands shifted because of adsorption; these observations were used to probe orientation. Orientation is determined by applying surface selections rules developed by both Creighton and Moskovits. The rules indicate, when the vibrational modes assigned to out-of-plane modes are observed as enhanced in the SER spectrum, the ligand is considered parallel relative to the metal surface, and when the vibrational modes assigned to in-plane modes are observed as enhanced, the ligand is not parallel relative to the metal surface. The relative surface enhancement factors were calculated by normalizing the spectra and then by taking the ratio of ISERS/INR. Based on the enhancement factors, the bands assigned to in-plane modes exhibited the highest enhancement factors on the Au and Ag SER spectra. This observation suggests that DAFO is not parallel to the metal nano-surfaces. In the Ag SERS spectrum the bands with the highest enhancement factors were assigned to quadrant ring stretching and cyclopentone bending. Analysis of the carbonyl stretching frequency on the Ag spectrum revealed the frequency shifted to a lower vibrational energy. This shift has been ascribed to the carbonyl bond losing double bond character, which permits the interaction between the metal and the carbonyl oxygen. It was proposed the DAFO ligand is sandwiched between the silver hydrosol. The TER spectrum of DAFO was obtained; analysis of the spectrum revealed similarities to the Ag SERS spectrum. The carbonyl stretching frequency was lowered, the bands

  1. Arsenic Adsorption Equilibrium Concentration and Adsorption Rate of Activated Carbon Coated with Ferric-Aluminum Hydroxides

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Sugita, H.; Oguma, T.; Hara, J.; Takahashi, S.

    2015-12-01

    In some areas of developing countries, ground or well water contaminated with arsenic has been reluctantly used as drinking water. It is highly desirable that effective and inexpensive arsenic removal agents should be developed and provided to reduce the potential health risk. Previous studies demonstrated that activated carbon coated with ferric-aluminum hydroxides (Fe-Al-C) has high adsorptive potential for removal of arsenic. In this study, a series of experiments using Fe-Al-C were carried to discuss adsorption equilibrium time, adsorption equilibrium concentration and adsorption rate of arsenic for Fe-Al-C. Fe-Al-C used in this study was provided by Astec Co., Ltd. Powder reagent of disodium hydrogen arsenate heptahydrate was dissolved into ion-exchanged water. The solution was then further diluted with ion-exchanged water to be 1 and 10 mg/L as arsenic concentration. The pH of the solution was adjusted to be around 7 by adding HCl and/or NaOH. The solution was used as artificial arsenic contaminated water in two types of experiments (arsenic adsorption equilibrium and arsenic adsorption rate tests). The results of the arsenic equilibrium tests were showed that a time period of about 3 days to reach apparent adsorption equilibrium for arsenic. The apparent adsorption equilibrium concentration and adsorbed amount of arsenic on Fe-Al-C adsorbent could be estimated by application of various adsorption isotherms, but the distribution coefficient of arsenic between solid and liquid varies with experimental conditions such as initial concentration of arsenic and addition concentration of adsorbent. An adsorption rate equation that takes into account the reduction in the number of effective adsorption sites on the adsorbent caused by the arsenic adsorption reaction was derived based on the data obtained from the arsenic adsorption rate tests.

  2. Spectrophotometric probe

    DOEpatents

    Prather, William S.; O'Rourke, Patrick E.

    1994-01-01

    A support structure bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe.

  3. Spectrophotometric probe

    DOEpatents

    Prather, W.S.; O'Rourke, P.E.

    1994-08-02

    A support structure is described bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe. 3 figs.

  4. Multi-platform comparison of ten commercial master mixes for probe-based real-time polymerase chain reaction detection of bioterrorism threat agents for surge preparedness.

    PubMed

    Buzard, Gregory S; Baker, Daniel; Wolcott, Mark J; Norwood, David A; Dauphin, Leslie A

    2012-11-30

    The Centers for Disease Control and Prevention and United States Army Research Institute for Infectious Diseases have developed real-time PCR assays for the detection of bioterrorism threat agents. These assays all rely on a limited number of approved real-time PCR master mixes. Because the availability of these reagents is a critical element of bioterrorism preparedness, we undertook a joint national preparedness exercise to address the potential surge needs resulting from a large-scale bio-emergency. We identified 9 commercially-available potential alternatives to an existing approved master mix (LightCycler FastStart DNA Master HybProbes): the TaqMan Fast Universal PCR master mix, OmniMix HS, FAST qPCR master mix, EXPRESS qPCR SuperMix kit, QuantiFast Probe PCR kit, LightCycler FastStart DNA Master(PLUS) HybProbe, Brilliant II FAST qPCR master mix, ABsolute Fast QPCR Mix and the HotStart IT Taq master mix. The performances of these kits were evaluated by the use of real-time PCR assays for four bioterrorism threat agents: Bacillus anthracis, Brucella melitensis, Burkholderia mallei and Francisella tularensis. The master mixes were compared for target-specific detection levels, as well as consistency of results among three different real-time PCR platforms (LightCycler, SmartCycler and 7500 Fast Dx). Real-time PCR analysis revealed that all ten kits performed well for agent detection on the 7500 Fast Dx instrument; however, the QuantiFast Probe PCR kit yielded the most consistently positive results across multiple real-time PCR platforms. We report that certain combinations of commonly used master mixes and instruments are not as reliable as others at detecting low concentrations of target DNA. Furthermore, our study provides laboratories the option to select from the commercial kits we evaluated to suit their preparedness needs. PMID:23107058

  5. Multi-platform comparison of ten commercial master mixes for probe-based real-time polymerase chain reaction detection of bioterrorism threat agents for surge preparedness.

    PubMed

    Buzard, Gregory S; Baker, Daniel; Wolcott, Mark J; Norwood, David A; Dauphin, Leslie A

    2012-11-30

    The Centers for Disease Control and Prevention and United States Army Research Institute for Infectious Diseases have developed real-time PCR assays for the detection of bioterrorism threat agents. These assays all rely on a limited number of approved real-time PCR master mixes. Because the availability of these reagents is a critical element of bioterrorism preparedness, we undertook a joint national preparedness exercise to address the potential surge needs resulting from a large-scale bio-emergency. We identified 9 commercially-available potential alternatives to an existing approved master mix (LightCycler FastStart DNA Master HybProbes): the TaqMan Fast Universal PCR master mix, OmniMix HS, FAST qPCR master mix, EXPRESS qPCR SuperMix kit, QuantiFast Probe PCR kit, LightCycler FastStart DNA Master(PLUS) HybProbe, Brilliant II FAST qPCR master mix, ABsolute Fast QPCR Mix and the HotStart IT Taq master mix. The performances of these kits were evaluated by the use of real-time PCR assays for four bioterrorism threat agents: Bacillus anthracis, Brucella melitensis, Burkholderia mallei and Francisella tularensis. The master mixes were compared for target-specific detection levels, as well as consistency of results among three different real-time PCR platforms (LightCycler, SmartCycler and 7500 Fast Dx). Real-time PCR analysis revealed that all ten kits performed well for agent detection on the 7500 Fast Dx instrument; however, the QuantiFast Probe PCR kit yielded the most consistently positive results across multiple real-time PCR platforms. We report that certain combinations of commonly used master mixes and instruments are not as reliable as others at detecting low concentrations of target DNA. Furthermore, our study provides laboratories the option to select from the commercial kits we evaluated to suit their preparedness needs.

  6. Imaging the O(1D) + CD4 → OD + CD3 reaction dynamics: Probing vibrationally and rotationally excited CD3 products

    NASA Astrophysics Data System (ADS)

    Shuai, Quan; Pan, Huilin; Yang, Jiayue; Zhang, Dong; Jiang, Bo; Dai, Dongxu; Yang, Xueming

    2012-12-01

    The dynamics of the O(1D) + CD4 → OD + CD3 reaction has been studied using the crossed molecular beam technique with sliced velocity map imaging. Internally excited CD3 products were detected using a (2+1) resonance-enhanced multiphoton ionization with state resolution. Dual reaction mechanisms, insertion and abstraction, were only observed for CD3 products with its umbrella mode (v2) excited or in its ground state, while CD3 products with other vibrational mode excited do not show any evidence of contributions from the abstraction pathway. Experimental results indicate that even though the insertion channel dominates the reaction, the abstraction channel contributes relatively more to vibrationally excited CD3 products. The state-to-state correlation between the two reaction products, OD and CD3, was determined for the abstraction channel at different collision energies. In addition, we measured rotationally hot CD3 products and found that these products are only produced via the insertion channel.

  7. Understanding Ligand-Exchange Reactions on Thiolate-Protected Gold Clusters by Probing Isomer Distributions Using Reversed-Phase High-Performance Liquid Chromatography.

    PubMed

    Niihori, Yoshiki; Kikuchi, Yoshihiro; Kato, Ayano; Matsuzaki, Miku; Negishi, Yuichi

    2015-09-22

    Thiolate-protected gold clusters (Aun(SR)m) have attracted considerable attention as functional nanomaterials in a wide range of fields. A ligand-exchange reaction has long been used to functionalize these clusters. In this study, we separated products from a ligand-exchange reaction of phenylethanethiolate-protected Au24Pd clusters (Au24Pd(SC2H4Ph)18), in which Au25(SR)18 is doped with palladium, into each coordination isomer with high resolution by reversed-phase high-performance liquid chromatography. This success has enabled isomer distributions of the products to be quantitatively evaluated. We evaluated quantitatively the isomer distributions of products obtained by the reaction of Au24Pd(SC2H4Ph)18 with thiol, disulfide, or diselenide. The results revealed that the exchange reaction starts to occur preferentially at thiolates that are bound directly to the metal core (thiolates of a core site) in all reactions. Further study on the isomer-separated Au24Pd(SC2H4Ph)17(SC12H25) revealed that clusters vary the coordination isomer distribution in solution by the ligand-exchange reaction between clusters and that control of the coordination isomer distribution of the starting clusters enables control of the coordination isomer distribution of the products generated by ligand-exchange reactions between clusters. Au24Pd(SC2H4Ph)18 used in this study has a similar framework structure to Au25(SR)18, which is one of the most studied compounds in the Aun(SR)m clusters. Knowledge gained in this study is expected to enable further understanding of ligand-exchange reactions on Au25(SR)18 and other Aun(SR)m clusters.

  8. Structure-Activity Relationships in NH3-SCR over Cu-SSZ-13 as Probed by Reaction Kinetics and EPR Studies

    SciTech Connect

    Gao, Feng; Walter, Eric D.; Karp, Eric M.; Luo, Jin-Yong; Tonkyn, Russell G.; Kwak, Ja Hun; Szanyi, Janos; Peden, Charles HF

    2013-04-01

    Cu-SSZ-13 catalysts with various Cu loadings were prepared via solution ion exchange. The hydrated samples were studied with Electron Paramagnetic Resonance (EPR). Cu2+ ion coordination numbers were obtained by analyzing the hyperfine structures while Cu-Cu distances were estimated from line broadening of the EPR features. By coupling EPR and temperature-programmed reduction (TPR) results, two Cu2+ ion locations were suggested. Standard and fast NH3-SCR, as well as non-selective NH3 oxidation reactions were carried out over these catalysts at high space velocities. For the SCR reaction, intra-particle diffusion limitation was found throughout the reaction temperatures investigated. Although clear structure-activity relationships cannot be derived, the reaction results allow for reactant diffusivities and Cu2+ ion locations to be estimated. The slower NH3 oxidation reaction, on the other hand, is kinetically limited at low temperatures, and, therefore, allows for a correlation between Cu2+ ion location and reaction kinetics to be made. Furthermore, the dynamic Cu2+ ion motion as a function of temperature could also be derived from the NH3 oxidation kinetics.

  9. Adsorption of cadmium from aqueous solutions by perlite.

    PubMed

    Mathialagan, T; Viraraghavan, T

    2002-10-14

    The present study examined the use of perlite for the removal of cadmium from aqueous solutions. The effects of pH and contact time on the adsorption process were examined. The optimum pH for adsorption was found to be 6.0. Residual cadmium concentration reached equilibrium in 6h and the rate of cadmium adsorption by perlite was rapid in the first hour of the reaction time. Ho's pseudo-second-order model best described the kinetics of the reaction. Batch adsorption experiments conducted at room temperature (22+/-1 degrees C) showed that the adsorption pattern followed the Freundlich isotherm model. The maximum removal of cadmium obtained from batch studies was 55%. Thomas model was used to describe the adsorption data from column studies. The results generally showed that perlite could be considered as a potential adsorbent for cadmium removal from aqueous solutions.

  10. New approach to real-time nucleic acids detection: folding polymerase chain reaction amplicons into a secondary structure to improve cleavage of Forster resonance energy transfer probes in 5'-nuclease assays.

    PubMed

    Kutyavin, Igor V

    2010-03-01

    The article describes a new technology for real-time polymerase chain reaction (PCR) detection of nucleic acids. Similar to Taqman, this new method, named Snake, utilizes the 5'-nuclease activity of Thermus aquaticus (Taq) DNA polymerase that cleaves dual-labeled Förster resonance energy transfer (FRET) probes and generates a fluorescent signal during PCR. However, the mechanism of the probe cleavage in Snake is different. In this assay, PCR amplicons fold into stem-loop secondary structures. Hybridization of FRET probes to one of these structures leads to the formation of optimal substrates for the 5'-nuclease activity of Taq. The stem-loop structures in the Snake amplicons are introduced by the unique design of one of the PCR primers, which carries a special 5'-flap sequence. It was found that at a certain length of these 5'-flap sequences the folded Snake amplicons have very little, if any, effect on PCR yield but benefit many aspects of the detection process, particularly the signal productivity. Unlike Taqman, the Snake system favors the use of short FRET probes with improved fluorescence background. The head-to-head comparison study of Snake and Taqman revealed that these two technologies have more differences than similarities with respect to their responses to changes in PCR protocol, e.g. the variations in primer concentration, annealing time, PCR asymmetry. The optimal PCR protocol for Snake has been identified. The technology's real-time performance was compared to a number of conventional assays including Taqman, 3'-MGB-Taqman, Molecular Beacon and Scorpion primers. The test trial showed that Snake supersedes the conventional assays in the signal productivity and detection of sequence variations as small as single nucleotide polymorphisms. Due to the assay's cost-effectiveness and simplicity of design, the technology is anticipated to quickly replace all known conventional methods currently used for real-time nucleic acid detection.

  11. Probing the dynamics of polyatomic multichannel elementary reactions by crossed molecular beam experiments with soft electron-ionization mass spectrometric detection.

    PubMed

    Casavecchia, Piergiorgio; Leonori, Francesca; Balucani, Nadia; Petrucci, Raffaele; Capozza, Giovanni; Segoloni, Enrico

    2009-01-01

    In this Perspective we highlight developments in the field of chemical reaction dynamics. Focus is on the advances recently made in the investigation of the dynamics of elementary multichannel radical-molecule and radical-radical reactions, as they have become possible using an improved crossed molecular beam scattering apparatus with universal electron-ionization mass spectrometric detection and time-of-flight analysis. These improvements consist in the implementation of (a) soft ionization detection by tunable low-energy electrons which has permitted us to reduce interfering signals originating from dissociative ionization processes, usually representing a major complication, (b) different beam crossing-angle set-ups which have permitted us to extend the range of collision energies over which a reaction can be studied, from very low (a few kJ mol(-1), as of interest in astrochemistry or planetary atmospheric chemistry) to quite high energies (several tens of kJ mol(-1), as of interest in high temperature combustion systems), and (c) continuous supersonic sources for producing a wide variety of atomic and molecular radical reactant beams. Exploiting these new features it has become possible to tackle the dynamics of a variety of polyatomic multichannel reactions, such as those occurring in many environments ranging from combustion and plasmas to terrestrial/planetary atmospheres and interstellar clouds. By measuring product angular and velocity distributions, after having suppressed or mitigated, when needed, the problem of dissociative ionization of interfering species (reactants, products, background gases) by soft ionization detection, essentially all primary reaction products can be identified, the dynamics of each reaction channel characterized, and the branching ratios determined as a function of collision energy. In general this information, besides being of fundamental relevance, is required for a predictive description of the chemistry of these

  12. STM CONTROL OF CHEMICAL REACTIONS: Single-Molecule Synthesis

    NASA Astrophysics Data System (ADS)

    Hla, Saw-Wai; Rieder, Karl-Heinz

    2003-10-01

    The fascinating advances in single atom/molecule manipulation with a scanning tunneling microscope (STM) tip allow scientists to fabricate atomic-scale structures or to probe chemical and physical properties of matters at an atomic level. Owing to these advances, it has become possible for the basic chemical reaction steps, such as dissociation, diffusion, adsorption, readsorption, and bond-formation processes, to be performed by using the STM tip. Complete sequences of chemical reactions are able to induce at a single-molecule level. New molecules can be constructed from the basic molecular building blocks on a one-molecule-at-a-time basis by using a variety of STM manipulation schemes in a systematic step-by-step manner. These achievements open up entirely new opportunities in nanochemistry and nanochemical technology. In this review, various STM manipulation techniques useful in the single-molecule reaction process are reviewed, and their impact on the future of nanoscience and technology are discussed.

  13. Probing the Reaction Pathway of Dehydrogenation of the LiNH2 + LiH Mixture Using In Situ 1H NMR Spectroscopy

    SciTech Connect

    Hu, Jian Zhi; Kwak, Ja Hun; Yang, Zhenguo; osborn, william; Markmaitree, Tippawan; Shaw, Leonard D.

    2008-06-15

    Using variable temperature in situ 1H NMR spectroscopy on a mixture of LiNH2 + LiH that was mechanically activated using high energy ball milling, the dehydrogenation of the LiNH2 + LiH to Li2NH + H2 was investigated. The analysis indicates NH3 release at a temperature as low as 300C and rapid reaction between NH3 and LiH at ~ 1500C. The transition from NH3 release to H2 appearance accompanied by disappearance of NH3 confirms unambiguously the two-step elementary reaction pathway proposed by other workers.

  14. A Perspective on the Maillard Reaction and the Analysis of Protein Glycation by Mass Spectrometry: Probing the Pathogenesis of Chronic Disease

    SciTech Connect

    Zhang, Qibin; Ames, Jennifer M.; Smith, Richard D.; Baynes, John; Metz, Thomas O.

    2008-12-18

    The Maillard reaction, starting from the glycation of protein and progressing to the formation of advanced glycation end-products (AGEs), is implicated in the development of complications of diabetes mellitus, as well as in the pathogenesis of cardiovascular, renal, and neurodegenerative diseases. In this perspective review, we provide on overview on the relevance of the Maillard reaction in the pathogenesis of chronic disease and discuss traditional approaches and recent developments in the analysis of glycated proteins by mass spectrometry. We propose that proteomics approaches, particularly bottom-up proteomics, will play a significant role in analyses of clinical samples leading to the identification of new markers of disease development and progression.

  15. Probing the correlations between the defects in metal-organic frameworks and their catalytic activity by an epoxide ring-opening reaction.

    PubMed

    Liu, Yangyang; Klet, Rachel C; Hupp, Joseph T; Farha, Omar

    2016-06-14

    Seven Zr/Hf-based MOFs with different degrees of defects were obtained by modulating the synthetic conditions. The number of missing linkers in these MOFs was calculated based on potentiometric acid-base titration. The number of defects was found to correlate quantitatively with the catalytic activity of UiO-type MOFs for an acid-catalyzed epoxide ring-opening reaction. More importantly, we were able to identify a MOF with inherent defective Zr6 nodes, which showed great activity and regio-selectivity for the epoxide ring-opening reaction. PMID:27229848

  16. A molecular investigation of adsorption onto mineral pigments

    NASA Astrophysics Data System (ADS)

    Ninness, Brian J.

    Pigment suspensions are important in several processes such as ceramics, paints, inks, and coatings. In the wet state, pigments are combined with a variety of chemical species such as polymers, surfactants, and polyelectrolytes which produce a complex colloidal system. The adsorption, desorption, and redistribution of these species at the pigment-aqueous solution interface can have an impact on the behavior in both the wet state or its final dried state. The goal of this work is to establish a molecular picture of the adsorption properties of these pigmented systems. A novel in situ infrared technique has been developed which allows the detection of adsorbed surface species on pigment particles in an aqueous environment. The technique involves the use of a polymeric binder to anchor the colloidal pigment particles to the surface of an internal reflection element (IRE). The binder only weakly perturbs about 25% of the reactive surface sites (hydroxyl groups) on silica. The reaction of succinic anhydride with an aminosilanized silica surface has been quantified using this technique. The adsorption dynamics of the cationic surfactant cetyltrimethylammonium bromide (C16TAB) at the TiO2-aqueous solution interface has been investigated using Fourier transform infrared-attenuated total reflection spectroscopy (FTIR-ATR) and electrokinetic analysis. At low bulk concentrations, C16TAB is shown to adsorb as isolated islands with a "defective" bilayer structure. Anionic probe molecules are shown to effectively "tune" the adsorbed surfactant microstructure. The results indicate that the structure of the adsorbed surfactant layer, and not the amount of adsorbed surfactant, dictates the subsequent adsorption behavior of the system. Atomic Layer Deposition is used to deposit a TiO2 layer onto the surfaces of silica and kaolin pigments. The process involves the cyclic reaction sequence of the vapors of TiCl4 and H2O. Three complete deposition cycles are needed before the surfaces

  17. A comparison of two real-time polymerase chain reaction assays using hybridization probes targeting either 16S ribosomal RNA or a subsurface lipoprotein gene for detecting leptospires in canine urine.

    PubMed

    Gentilini, Fabio; Zanoni, Renato Giulio; Zambon, Elisa; Turba, Maria Elena

    2015-11-01

    Leptospires are excreted in the urine of infected animals, and the prompt detection of leptospiral DNA using polymerase chain reaction (PCR) is increasingly being used. However, contradictory data has emerged concerning the diagnostic accuracy of the most popular PCR assays that target either the 16S ribosomal RNA (rrs) or the subsurface lipoprotein (LipL32) genes. In order to clarify the effect of the gene target, a novel hydrolysis probe-based, quantitative real-time PCR (qPCR) assay targeting the LipL32 gene was developed, validated, and then compared directly to the previously described rrs hydrolysis probe-based qPCR using a convenience collection of canine urine samples. The novel LipL32 qPCR assay was linear from 5.9 × 10(6) to 59 genome equivalents per reaction. Both the LipL32 and the rrs qPCR assays showed a limit of detection of 10 target copies per reaction indicating an approximately equivalent analytical sensitivity. Both assays amplified all 20 pathogenic leptospiral strains tested but did not amplify a representative collection of bacteria commonly found in voided canine urine. When the field samples were assayed, 1 and 5 out of 184 samples yielded an amplification signal in the LipL32 and rrs assays, respectively. Nevertheless, when the limit of detection was considered as the cutoff for interpreting findings, the 4 discordant cases were judged as negative. In conclusion, our study confirmed that both LipL32 and rrs are suitable targets for qPCR for the detection of leptospiral DNA in canine urine. However, the rrs target requires the mandatory use of a cutoff value in order to correctly interpret spurious amplifications.

  18. A comparison of two real-time polymerase chain reaction assays using hybridization probes targeting either 16S ribosomal RNA or a subsurface lipoprotein gene for detecting leptospires in canine urine.

    PubMed

    Gentilini, Fabio; Zanoni, Renato Giulio; Zambon, Elisa; Turba, Maria Elena

    2015-11-01

    Leptospires are excreted in the urine of infected animals, and the prompt detection of leptospiral DNA using polymerase chain reaction (PCR) is increasingly being used. However, contradictory data has emerged concerning the diagnostic accuracy of the most popular PCR assays that target either the 16S ribosomal RNA (rrs) or the subsurface lipoprotein (LipL32) genes. In order to clarify the effect of the gene target, a novel hydrolysis probe-based, quantitative real-time PCR (qPCR) assay targeting the LipL32 gene was developed, validated, and then compared directly to the previously described rrs hydrolysis probe-based qPCR using a convenience collection of canine urine samples. The novel LipL32 qPCR assay was linear from 5.9 × 10(6) to 59 genome equivalents per reaction. Both the LipL32 and the rrs qPCR assays showed a limit of detection of 10 target copies per reaction indicating an approximately equivalent analytical sensitivity. Both assays amplified all 20 pathogenic leptospiral strains tested but did not amplify a representative collection of bacteria commonly found in voided canine urine. When the field samples were assayed, 1 and 5 out of 184 samples yielded an amplification signal in the LipL32 and rrs assays, respectively. Nevertheless, when the limit of detection was considered as the cutoff for interpreting findings, the 4 discordant cases were judged as negative. In conclusion, our study confirmed that both LipL32 and rrs are suitable targets for qPCR for the detection of leptospiral DNA in canine urine. However, the rrs target requires the mandatory use of a cutoff value in order to correctly interpret spurious amplifications. PMID:26450835

  19. Competitive adsorption of cellulase components and its significance in a synergistic mechanism

    SciTech Connect

    Ryu, D.D.Y.; Kim, C.; Mandels, M.

    1984-05-01

    Some studies on the adsorption of cellulase on cellulose revealed part of the mechanisms involved in the enzymatic hydrolysis of cellulose and provided some clues to the synergistic mechanism of cellulase complex. The adsorption of cellulase was significantly affected by the reaction conditions and physical chemical characteristics of cellulose. Endoglucanase consisted of adsorbable and nonadsorbable components. Cellobiohydrolase had the strongest adsorption affinity. Each cellulase component is postulated to have distinctly different adsorption sites on cellulose, corresponding to the active sites in the hydrolysis reaction. Competitive adsorption kinetics between cellulase components were also observed during the adsorption process. The degree of competitive adsorption was most remarkable when the composition of cellulase components was nearly the same as that in the crude cellulase complex. This seems to show the optimal relative composition of cellulase components. The synergism between cellobiohydrolase and endoglucananse could be elucidated more clearly by this competitive adsorption model of the reaction mechanism.

  20. Beta-decay of 31Cl: an indirect probe of the 30P(p,γ)31S reaction. Present status and future perspectives

    NASA Astrophysics Data System (ADS)

    Saastamoinen, Antti; Kankainen, Anu; Trache, Livius

    2016-08-01

    β-decay of 31Cl can be used as a selective tool for studying astrophysically relevant states in 31S. In this article we review the present status of the decay data. The implications for the 30P(p,γ)31S reaction rate at novae temperatures, and future experimental ideas are discussed.

  1. Adsorption of poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) polymers on zinc, zinc oxide, iron, and iron oxide surfaces.

    PubMed

    Seifert, Susan; Simon, Frank; Baumann, Giesela; Hietschold, Michael; Seifert, Andreas; Spange, Stefan

    2011-12-01

    The adsorption of poly(vinyl formamide) (PVFA) and the statistic copolymers poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) onto zinc and iron metal particles as well as their oxides was investigated. The adsorbates were characterized by means of XPS, DRIFT spectroscopy, wet chemical analysis, and solvatochromic probes. Dicyano-bis-(1,10-phenanthroline)-iron(II) (1), 3-(4-amino-3-methylphenyl)-7-phenyl-benzo-[1,2-b:4,5-b']difuran-2,6-dione (2), and 4-tert-butyl-2-(dicyano-methylene)-5-[4-(diethylamino)-benzylidene]-Δ(3)-thiazoline (3) as solvatochromic probes were coadsorbed onto zinc oxide to measure various effects of surface polarity. The experimental findings showed that the adsorption mechanism of PVFA and PVFA-co-PVAm strongly depends on the degree of hydrolysis of PVFA and pH values and also on the kind of metal or metal oxide surfaces that were employed as adsorbents. The adsorption mechanism of PVFA/PVFA-co-PVAm onto zinc oxide and iron oxide surfaces is mainly affected by electrostatic interactions. Particularly in the region of pH 5, the adsorption of PVFA/PVFA-co-PVAm onto zinc and iron metal particles is additionally influenced by redox processes, dissolution, and complexation reactions.

  2. Derivation of the Freundlich Adsorption Isotherm from Kinetics

    ERIC Educational Resources Information Center

    Skopp, Joseph

    2009-01-01

    The Freundlich adsorption isotherm is a useful description of adsorption phenomena. It is frequently presented as an empirical equation with little theoretical basis. In fact, a variety of derivations exist. Here a new derivation is presented using the concepts of fractal reaction kinetics. This derivation provides an alternative basis for…

  3. Use of H2S to Probe the Active Sites in FeNC Catalysts for the Oxygen Reduction Reaction (ORR) in Acidic Media

    SciTech Connect

    Singh, Deepika; Mamtani, Kuldeep; Bruening, Christopher R.; Miller, Jeffrey T.; Ozkan, Umit S.

    2014-10-01

    H2S has been used as a probe molecule both in an “in situ” poisoning experiment and in intermediate-temperature heat-treatment steps during and after the preparation of FeNC catalysts in an attempt to analyze its effect on their ORR activity. The heat treatments were employed either on the ball-milled precursor of FeNC or after the Ar-NH3 high temperature heat treatments. ORR activity of the H2S-treated catalysts was seen to be significantly lower than the sulfur-free catalysts, whether the sulfur exposure was during a half-cell testing, or as an intermediate-temperature exposure to H2S. The incorporation of sulfur species and interaction of Fe with sulfur were confirmed by characterization using XPS, EXAFS, TPO, and TPD. This study provides crucial evidence regarding differences in active sites in FeNC versus nitrogen-containing carbon nanostructured (CNx) catalysts.

  4. Detection of transgenes in soybean via a polymerase chain reaction and a simple bioluminometric assay based on a universal aequorin-labeled oligonucleotide probe.

    PubMed

    Glynou, Kyriaki; Ioannou, Penelope C; Christopoulos, Theodore K

    2004-04-01

    The recombinant photoprotein aequorin was used as a reporter in highly sensitive and automatable hybridization assays for the analysis of transgenic sequences in genetically modified organisms (GMO). The terminator of the nopaline synthase gene (NOS) from Agrobacterium tumefaciens and the 35S promoter sequence were detected in genetically modified soybean. The endogenous, soybean-specific, lectin gene was also detected for confirmation of the integrity of extracted DNA. A universal detection reagent was produced through conjugation of aequorin to the oligonucleotide (dA)(30). Biotinylated (through PCR) products for the three target sequences were captured onto streptavidin-coated wells, and one strand was removed by NaOH treatment. The immobilized single-stranded DNAs were then hybridized with oligonucleotide probes consisting of a target-specific segment and a poly(dT) tail. This allowed the subsequent determination of all hybrids through the use of the (dA)(30)-aequorin conjugate as a universal reagent. The bound aequorin was measured by adding Ca(2+) and integrating the light emission for 3 s. As low as 2 pM (100 amol per well) of amplified DNA was detectable for all three targets, with a signal-to-background ratio of about 2. The analytical range extended up to 2000 pM. As low as 0.05% GMO content in soybean can be detected with a signal-to-background ratio of 8.2. The overall repeatability of the proposed assay, including DNA extraction, PCR, and hybridization assay, ranged from 7.5-19.8%. The use of a (dA)(30)-aequorin conjugate renders the assay configuration general for any target DNA, provided that the specific probe carries a poly(dT) tail.

  5. Probing the reaction mechanism of the D-ala-D-ala dipeptidase, VanX, by using stopped-flow kinetic and rapid-freeze quench EPR studies on the Co(II)-substituted enzyme.

    PubMed

    Matthews, Megan L; Periyannan, Gopalraj; Hajdin, Christine; Sidgel, Tara K; Bennett, Brian; Crowder, Michael W

    2006-10-11

    In an effort to probe the reaction mechanism of VanX, the d-ala-d-ala dipeptidase required for high-level vancomycin resistance in bacteria, stopped-flow kinetic and rapid-freeze quench EPR studies were conducted on the Co(II)-substituted enzyme when reacted with d-ala-d-ala. The intensity of the Co(II) ligand field band at 550 nm decreased (epsilon550 = 140 to 18 M-1 cm-1) when VanX was reacted with substrate, suggesting that the coordination number of the metal increases from 5 to 6 upon substrate binding. The stopped-flow trace was fitted to a kinetic mechanism that suggests the presence of an intermediate whose breakdown is rate-limiting. Rapid-freeze quench EPR studies verified the presence of a reaction intermediate that exhibits an unusually low hyperfine constant (33 G), which suggests a bidentate coordination of the intermediate to the metal center. The EPR studies also identified a distinct enzyme product complex. The results were used to offer a detailed reaction mechanism for VanX that can be used to guide future inhibitor design efforts.

  6. Communication: probing the entrance channels of the X+CH4→HX+CH3 (X = F, Cl, Br, I) reactions via photodetachment of X(-)-CH4.

    PubMed

    Cheng, Min; Feng, Yuan; Du, Yikui; Zhu, Qihe; Zheng, Weijun; Czakó, Gábor; Bowman, Joel M

    2011-05-21

    The entrance channel potentials of the prototypical polyatomic reaction family X + CH(4) → HX + CH(3) (X = F, Cl, Br, I) are investigated using anion photoelectron spectroscopy and high-level ab initio electronic structure computations. The pre-reactive van der Waals (vdW) wells of these reactions are probed for X = Cl, Br, I by photodetachment spectra of the corresponding X(-)-CH(4) anion complex. For F-CH(4), a spin-orbit splitting (∼1310 cm(-1)) much larger than that of the F atom (404 cm(-1)) was observed, in good agreement with theory. This showed that in the case of the F-CH(4) system the vertical transition from the anion ground state to the neutral potentials accesses a region between the vdW valley and transition state of the early-barrier F + CH(4) reaction. The doublet splittings observed in the other halogen complexes are close to the isolated atomic spin-orbit splittings, also in agreement with theory.

  7. Modeling adsorption: Investigating adsorbate and adsorbent properties

    NASA Astrophysics Data System (ADS)

    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

  8. Surfaces of Microparticles in Colloids: Structure and Molecular Adsorption Kinetics

    NASA Astrophysics Data System (ADS)

    Dai, Hai-Lung

    2002-03-01

    Surfaces of micron and sub-micron size particles in liquid solution are probed by second harmonic generation (SHG) facilitated with femtosecond laser pulses. The particles probed include inorganic objects such as carbon black and color pigments, polymeric species like polystyrene beads, and biological systems such as blood cells and ecoli. In the experiments, dye molecules are first adsorbed onto the particle surface to allow generation of second harmonics upon light irradiation. Competition for adsorption between these surface dye molecules and the molecules of interest in the solution is then monitored by the SHG signal to reveal the molecular adsorption kinetics and surface structure. Specifically, surfactant adsorption on polymer surfaces, the structure of carbon black surface, and protein adsorption on biological surfaces, monitored by this technique, will be discussed.

  9. Kelvin probe force microscopy in nonpolar liquids.

    PubMed

    Domanski, Anna L; Sengupta, Esha; Bley, Karina; Untch, Maria B; Weber, Stefan A L; Landfester, Katharina; Weiss, Clemens K; Butt, Hans-Jürgen; Berger, Rüdiger

    2012-10-01

    Work function changes of Au were measured by Kelvin probe force microscopy (KPFM) in the nonpolar liquid decane. As a proof of principle for the measurement in liquids, we investigated the work function change of an Au substrate upon hexadecanethiol chemisorption. To relate the measured contact potential difference (CPD) during the chemisorption of alkanethiols to a change of the work function, the influence of physisorbed decane must be taken into account. It is crucial that either the work function of the scanning probe microscope (SPM) tip or the sample surface remains constant throughout the reaction, since both contribute to the CPD. We describe two routes for determining the work function shift of Au coated with a monolayer of alkanethiols: In the first route, the SPM tips were taken as reference surfaces (constant tip work function). For this approach, we used Au(111) surfaces and kept the SPM tip ex situ during the adsorption process. In the second route, structured surfaces with reactive and inert parts were studied by KPFM (constant reference work function). For this route, we prepared nanometer sized Au structures by nanosphere lithography on SiO(x) substrates. Now, the SiO(x) served as the inert reference surface. The shifts in the work function after exposure to the hexadecanethiol (HDT) solution were determined to be ΔΦ(Au+HDT,decane-Au,air) = -1.33 eV ± 0.07 eV (route I) and ΔΦ(Au+HDT,decane-Au,air) = -1.46 eV ± 0.04 eV (route II). Both values are in excellent agreement with the work function shifts determined by ultraviolet photoemission spectroscopy (UPS) reported in literature. The presented procedures of measuring work function changes in decane open new ways to study local reactions at solid-liquid interfaces.

  10. Experimental evidence for chair-like transition states in aldol reactions of methyl ketone lithium enolates: stereoselective synthesis and utilization of a deuterium-labeled enolate as a probe of reaction stereochemistry.

    PubMed

    Liu, Christopher M; Smith, William J; Gustin, Darin J; Roush, William R

    2005-04-27

    Aldol reactions of methyl ketone lithium enolates proceed via chairlike Zimmerman-Traxler transition states with 7:1 to 50:1 preference over alternative, boatlike transition structures, as determined by studies involving the configurationally stable deuterium-labeled enol silane 18 as the lithium enolate precursor.

  11. Ammonia Production Using Pressure Swing Adsorption

    SciTech Connect

    2009-02-01

    This factsheet describes a research project whose overall objective is to develop and demonstrate a technically feasible and commercially viable system that integrates reaction to produce ammonia along with recovery of the products by adsorption separation methods and significantly decrease the energy requirement in ammonia production.

  12. Enhancing the sensitivity of immunoassay procedures by use of antibodies directed to the product of a reaction between probe labels and assay substrates

    DOEpatents

    Erlanger, Bernard F.; Chen, Bi-Xing

    1999-01-01

    The subject invention provides an antibody which specifically binds to the product of a reaction between a labeling substance and a substrate. The subject invention also provides a method of making an immunogen used to produce the antibody of the subject invention. The invention further provides methods of using the subject antibody for detecting an antigen of interest in a sample, for example, detecting a protein comprising an amino acid sequence of interest and detecting a nucleic acid molecule comprising a nucleic acid sequence of interest, detecting a polypeptide such as those expressed by infectious agents, fungi or parasites.

  13. Enhancing the sensitivity of immunoassay procedures by use of antibodies directed to the product of a reaction between probe labels and assay substrates

    DOEpatents

    Erlanger, B.F.; Chen, B.

    1999-07-20

    The subject invention provides an antibody which specifically binds to the product of a reaction between a labeling substance and a substrate. The subject invention also provides a method of making an immunogen used to produce the antibody of the subject invention. The invention further provides methods of using the subject antibody for detecting an antigen of interest in a sample, for example, detecting a protein comprising an amino acid sequence of interest and detecting a nucleic acid molecule comprising a nucleic acid sequence of interest, detecting a polypeptide such as those expressed by infectious agents, fungi or parasites. 25 figs.

  14. Enhancing the sensitivity of immunoassay procedures by use of antibodies directed to the product of a reaction between probe labels and assay substrates

    DOEpatents

    Erlanger, Bernard F.; Chen, Bi-Xing

    1997-01-01

    The subject invention provides an antibody which specifically binds to the product of a reaction between a labeling substance and a substrate. The subject invention also provides a method of making an immunogen used to produce the antibody of the subject invention. The invention further provides methods of using the subject antibody for detecting an antigen of interest in a sample, for example detecting a protein comprising an amino acid sequence of interest and detecting a nucleic acid molecule comprising a nucleic acid sequence of interest.

  15. Enhancing the sensitivity of immunoassay procedures by use of antibodies directed to the product of a reaction between probe labels and assay substrates

    DOEpatents

    Erlanger, B.F.; Chen, B.X.

    1997-07-22

    The subject invention provides an antibody which specifically binds to the product of a reaction between a labeling substance and a substrate. The subject invention also provides a method of making an immunogen used to produce the antibody of the subject invention. The invention further provides methods of using the subject antibody for detecting an antigen of interest in a sample, for example detecting a protein comprising an amino acid sequence of interest and detecting a nucleic acid molecule comprising a nucleic acid sequence of interest. 8 figs.

  16. Chiroptical Probing of Lanthanide-Directed Self-Assembly Formation Using btp Ligands Formed in One-Pot Diazo-Transfer/Deprotection Click Reaction from Chiral Amines.

    PubMed

    Byrne, Joseph P; Martínez-Calvo, Miguel; Peacock, Robert D; Gunnlaugsson, Thorfinnur

    2016-01-11

    A series of enantiomeric 2,6-bis(1,2,3-triazol-4-yl)pyridines (btp)-containing ligands was synthesized by a one-pot two-step copper-catalyzed amine/alkyne click reaction. The Eu(III) - and Tb(III) -directed self-assembly formation of these ligands was studied in CH3 CN by monitoring their various photophysical properties, including their emerging circular dichroism and circularly polarized luminescence. The global analysis of the former enabled the determination of both the stoichiometry and the stability constants of the various chiral supramolecular species in solution. PMID:26555573

  17. Competitive C{double_bond}C and C{double_bond}O adsorption of {alpha}-{beta} unsaturated aldehydes on Pt and Pd surfaces in relation with the selectivity of hydrogenation reactions: A theoretical approach

    SciTech Connect

    Delbecq, F.; Sautet, P.

    1995-04-01

    The adsorption geometries of acrolein, crotonaldehyde, methylcrotonaldehyde (prenal), and cinnamaldehyde on Pt and Pd surfaces have been studied by means of semiempirical extended Hueckel calculations: Pt(111), Pt(100), Pt(110), and Pd(111) surfaces, and steps on Pt(111) have been compared. Depending on the face and the substituents of the organic molecule, the adsorption geometries are totally different: a di-{sigma} form is preferred on Pt(111), a planar {eta}{sub 4} one on Pd(111) and Pt(100), and a {pi}{sub cc} one on Pt(110) and on the step. These preferred adsorption modes allow one to explain the selectivity observed during the hydrogenation of prenal on these well-defined surfaces. The results obtained in this work also allow one to understand the behavior of different metal catalysts towards the hydrogenation of the {alpha}-{beta} unsaturated aldehydes. 32 refs., 8 figs., 8 tabs.

  18. A novel real-time reverse transcription-polymerase chain reaction assay with partially double-stranded linear DNA probe for sensitive detection of hepatitis C viral RNA.

    PubMed

    Liu, Tianfu; Wan, Zhenzhou; Liu, Jia; Zhang, Lingyi; Zhou, Yanheng; Lan, Ke; Hu, Yihong; Zhang, Chiyu

    2016-10-01

    The detection and quantification of HCV RNA is very helpful for the management and treatment of HCV related diseases. Detection of low HCV viral load is a great challenge in HCV RNA detection. Here, we developed a novel real-time RT-PCR assay with partially double-stranded linear DNA probe which can detect all HCV genotypes and improve the detection performance. The novel assay has a wide linear dynamic range of HCV RNA quantification (1×10(2)-1×10(11)IU/ml) and a limit of detection of 78IU/ml. The assay exhibits an excellent reproducibility with 2.52% and 1.33% coefficients of variations, for inter- and intra-assays, respectively. To evaluate the viability of the assay, a comparison with a commercial HCV RNA detection kit was performed using 106 serum samples. The lineared correlation coefficient between the novel assay and the commercial HCV RNA detection kit was 0.940. Meanwhile, the deviation between the two methods was tolerable. Therefore, the novel real-time RT-PCR assay was applicable for laboratory diagnosis and monitoring of HCV infection. PMID:27451264

  19. Pan-serotypic detection of foot-and-mouth disease virus using a minor groove binder probe reverse transcription polymerase chain reaction assay.

    PubMed

    McKillen, John; McMenamy, Michael; Reid, Scott M; Duffy, Catherine; Hjertner, Bernt; King, Donald P; Bélak, Sándor; Welsh, Michael; Allan, Gordon

    2011-06-01

    A novel assay for the pan-serotypic detection of foot-and-mouth disease virus (FMDV) was designed using a 5' conjugated minor groove binder (MGB) probe real-time RT-PCR system. This assay targets the 3D region of the FMDV genome and is capable of detecting 20 copies of a transcribed RNA standard. The linear range of the test was eight logs from 2 × 10¹ to 2 × 10⁸ copies and amplification time was approximately 2 h. Using a panel of 83 RNA samples from representative FMDV isolates, the diagnostic sensitivity of this test was shown to be equivalent to a TaqMan real-time RT-PCR that targets the 5' untranslated region of FMDV. Furthermore, the assay does not detect viruses causing similar clinical diseases in pigs such as swine vesicular disease virus and vesicular stomatitis virus, nor does it detect marine caliciviruses causing vesicular exanthema. The development of this assay provides a useful tool for the differential diagnosis of FMD, potentially for use in statutory or emergency testing programmes, or for detection of FMDV RNA in research applications. PMID:21419170

  20. Adsorption Refrigeration System

    SciTech Connect

    Wang, Kai; Vineyard, Edward Allan

    2011-01-01

    Adsorption refrigeration is an environmentally friendly cooling technology which could be driven by recovered waste heat or low-grade heat such as solar energy. In comparison with absorption system, an adsorption system has no problems such as corrosion at high temperature and salt crystallization. In comparison with vapor compression refrigeration system, it has the advantages of simple control, no moving parts and less noise. This paper introduces the basic theory of adsorption cycle as well as the advanced adsorption cycles such as heat and mass recovery cycle, thermal wave cycle and convection thermal wave cycle. The types, characteristics, advantages and drawbacks of different adsorbents used in adsorption refrigeration systems are also summarized. This article will increase the awareness of this emerging cooling technology among the HVAC engineers and help them select appropriate adsorption systems in energy-efficient building design.

  1. Intramolecular charge transfer of 4-(dimethylamino)benzonitrile probed by time-resolved fluorescence and transient absorption: No evidence for two ICT states and a pisigma( *) reaction intermediate.

    PubMed

    Zachariasse, Klaas A; Druzhinin, Sergey I; Kovalenko, Sergey A; Senyushkina, Tamara

    2009-12-14

    For the double exponential fluorescence decays of the locally excited (LE) and intramolecular charge transfer (ICT) states of 4-(dimethylamino)benzonitrile (DMABN) in acetonitrile (MeCN) the same times tau(1) and tau(2) are observed. This means that the reversible LE<==>ICT reaction, starting from the initially excited LE state, can be adequately described by a two state mechanism. The most important factor responsible for the sometimes experimentally observed differences in the nanosecond decay time, with tau(1)(LE)reaction of DMABN are discussed. From the appearance of an excited state absorption (ESA) band in the spectral region between 700 and 800 nm in MeCN for N,N-dimethylanilines with CN, Br, F, CF(3), and C(=O)OC(2)H(2) p-substituents, it is concluded that this ESA band cannot be attributed to a pisigma( *) state, as only the C-C[Triple Bond]N group can undergo the required 120 degrees bending. PMID:20001042

  2. Immobilised histidine tagged β2-adrenoceptor oriented by a diazonium salt reaction and its application in exploring drug-protein interaction using ephedrine and pseudoephedrine as probes.

    PubMed

    Li, Qian; Bian, Liujiao; Zhao, Xinfeng; Gao, Xiaokang; Zheng, Jianbin; Li, Zijian; Zhang, Youyi; Jiang, Ru; Zheng, Xiaohui

    2014-01-01

    A new oriented method using a diazonium salt reaction was developed for linking β2-adrenoceptor (β2-AR) on the surface of macroporous silica gel. Stationary phase containing the immobilised receptor was used to investigate the interaction between β2-AR and ephedrine plus pseudoephedrine by zonal elution. The isotherms of the two drugs best fit the Langmuir model. Only one type of binding site was found for ephedrine and pseudoephedrine targeting β2-AR. At 37 °C, the association constants during the binding were (5.94±0.05)×103/M for ephedrine and (3.80±0.02) ×103/M for pseudoephedrine, with the binding sites of (8.92±0.06) ×10-4 M. Thermodynamic studies showed that the binding of the two compounds to β2-AR was a spontaneous reaction with exothermal processes. The ΔGθ, ΔHθ and ΔSθ for the interaction between ephedrine and β2-AR were -(22.33±0.04) kJ/mol, -(6.51±0.69) kJ/mol and 50.94±0.31 J/mol·K, respectively. For the binding of pseudoephedrine to the receptor, these values were -(21.17±0.02) kJ/mol, -(7.48±0.56) kJ/mol and 44.13±0.01 J/mol·K. Electrostatic interaction proved to be the driving force during the binding of the two drugs to β2-AR. The proposed immobilised method will have great potential for attaching protein to solid substrates and realizing the interactions between proteins and drugs.

  3. Immobilised Histidine Tagged β2-Adrenoceptor Oriented by a Diazonium Salt Reaction and Its Application in Exploring Drug-Protein Interaction Using Ephedrine and Pseudoephedrine as Probes

    PubMed Central

    Li, Qian; Bian, Liujiao; Zhao, Xinfeng; Gao, Xiaokang; Zheng, Jianbin; Li, Zijian; Zhang, Youyi; Jiang, Ru; Zheng, Xiaohui

    2014-01-01

    A new oriented method using a diazonium salt reaction was developed for linking β2-adrenoceptor (β2-AR) on the surface of macroporous silica gel. Stationary phase containing the immobilised receptor was used to investigate the interaction between β2-AR and ephedrine plus pseudoephedrine by zonal elution. The isotherms of the two drugs best fit the Langmuir model. Only one type of binding site was found for ephedrine and pseudoephedrine targeting β2-AR. At 37 °C, the association constants during the binding were (5.94±0.05)×103/M for ephedrine and (3.80±0.02) ×103/M for pseudoephedrine, with the binding sites of (8.92±0.06) ×10−4 M. Thermodynamic studies showed that the binding of the two compounds to β2-AR was a spontaneous reaction with exothermal processes. The ΔGθ, ΔHθ and ΔSθ for the interaction between ephedrine and β2-AR were −(22.33±0.04) kJ/mol, −(6.51±0.69) kJ/mol and 50.94±0.31 J/mol·K, respectively. For the binding of pseudoephedrine to the receptor, these values were −(21.17±0.02) kJ/mol, −(7.48±0.56) kJ/mol and 44.13±0.01 J/mol·K. Electrostatic interaction proved to be the driving force during the binding of the two drugs to β2-AR. The proposed immobilised method will have great potential for attaching protein to solid substrates and realizing the interactions between proteins and drugs. PMID:24747442

  4. Optical probe

    DOEpatents

    Hencken, Kenneth; Flower, William L.

    1999-01-01

    A compact optical probe is disclosed particularly useful for analysis of emissions in industrial environments. The instant invention provides a geometry for optically-based measurements that allows all optical components (source, detector, rely optics, etc.) to be located in proximity to one another. The geometry of the probe disclosed herein provides a means for making optical measurements in environments where it is difficult and/or expensive to gain access to the vicinity of a flow stream to be measured. Significantly, the lens geometry of the optical probe allows the analysis location within a flow stream being monitored to be moved while maintaining optical alignment of all components even when the optical probe is focused on a plurality of different analysis points within the flow stream.

  5. Probing the Repulsive Core of the Nucleon-Nucleon Interaction via the 4He(e,e`pN) Triple-Coincidence Reaction

    SciTech Connect

    Korover, Igor; Muangma, Navaphon; Hen, Or; Shneor, Ran; Sulkosky, Vincent; Kelleher, Aidan; Gilad, Shalev; Higinbotham, Douglas; Piasetzky, Eliazer; Wood, Stephen; Rakhman, Abdurahim; Aguilera, Paula; Ahmed, Zafar; Albataineh, Hisham; Allada, Kalyan; Anderson, Bryon; Anez, David; Aniol, Konrad; Annand, John; Armstrong, Whitney; Arrington, John; Averett, Todd; Badman, Toby; Baghdasaryan, Hovhannes; Bai, Xinzhan; Beck, Arie; Beck, Sharon; Bellini, Vincenzo; Benmokhtar, Fatiha; Bertozzi, William; Bittner, James; Boeglin, Werner; Camsonne, Alexandre; Chen, Chunhua; Chen, Jian -Ping; Chirapatpimol, Khem; Cisbani, Evaristo; Dalton, Mark; Daniel, Aji; Day, Donal; De, Cornelis; de Jager, C. W.; De, Raffaele; Leo, R. De; Deconinck, Wouter; Defurne, Maxime; Flay, David; Fomin, Nadia; Friend, Megan; Frullani, Salvatore; Fuchey, Eric; Garibaldi, Franco; Gaskell, David; Gilman, Ronald; Glamazdin, Oleksandr; Gu, Chao; Gueye, Paul; Hamilton, David; Hanretty, Charles; Hansen, Jens-Ole; Shabestari, Mitra Hashemi; Holmstrom, Timothy; Huang, Min; Iqbal, Sophia; Jin, Ge; Kalantarians, Narbe; Kang, Hoyoung; Khandaker, Mahbubul; LeRose, John; Leckey, John; Lindgren, Richard; Long, Elena; Mammei, Juliette; Margaziotis, Demetrius; Markowitz, Pete; Meekins, David; Meziani, Zein -Eddine; Michaels, Robert; Mihovilovic, Miha; Monaghan, Peter; Munoz, Carlos; Camacho, C. Munoz; Norum, Blaine; Nuruzzaman, nfn; Pan, Kai; Phillips, Sarah; Pomerantz, Ishay; Posik, Matthew; Punjabi, Vina; Qian, Xin; Qiang, Yi; Qiu, Xiyu; Reimer, Paul; Riordan, Seamus; Ron, Guy; Rondon-Aramayo, Oscar; Saha, Arunava; Schulte, Elaine; Selvy, Lawrence; Shahinyan, Albert; Sirca, Simon; Sjoegren, Johan; Slifer, Karl; Solvignon-Slifer, Patricia; Sparveris, Nikolaos; Subedi, Ramesh; Tireman, William; Wang, Diancheng; Weinstein, Lawrence; Wojtsekhowski, Bogdan; Yan, Wenbiao; Yaron, Israel; Ye, Zhihong; Zhan, X.; Zhang, J.; Zhang, Yawei; Zhao, Bo; Zhao, Zhiwen; Zheng, Xiaochao; Zhu, Pengjia; Zielinski, Ryan; Watson, John

    2014-07-01

    We studied simultaneously the 4He(e,e'p), 4He(e,e'pp), and 4He(e,e'pn) reactions at Q2=2 [GeV/c]2 and xB >1, for a (e,e'p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum in a region where the nucleon-nucleon force is expected to change from predominantly tensor to repulsive. Neutron-proton pairs dominate the high-momentum tail of the nucleon momentum distributions, but their abundance is reduced as the nucleon momentum increases beyond ~500 MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum in the range we studied. Our data are compared with ab-initio calculations of two-nucleon momentum distributions in 4He.

  6. Electrospray ionization mass spectrometric investigations of [alpha]-dicarbonyl compounds--Probing intermediates formed in the course of the nonenzymatic browning reaction of l-ascorbic acid

    NASA Astrophysics Data System (ADS)

    Schulz, Anke; Trage, Claudia; Schwarz, Helmut; Kroh, Lothar W.

    2007-05-01

    A new method is presented which allows the simultaneous detection of various [alpha]-dicarbonyl compounds generated in the course of the nonenzymatic browning reaction initiated by thermal treatment of l-ascorbic acid, namely: glyoxal, methylglyoxal, diacetyl, 3-deoxy-l-pentosone, and l-threosoneE 3-Deoxy-l-threosone was successfully identified as a new C4-[alpha]-dicarbonyl structure for the first time in the degradation of Vitamin C by application of this non-chromatographic mass spectrometric approach. Moreover, a more detailed elucidation of the mechanistic scenario with respect to the oxidative and nonoxidative pathways is presented by using dehydro-l-ascorbic acid and 2,3-diketo-l-gulonic acid instead of l-ascorbic acid as a starting material. Furthermore, the postulated pathways are corroborated with the aid of 13C-isotopic labeling studies. The investigations were extended to baby food, and the successful detection of [alpha]-dicarbonyl compounds characteristic for Vitamin C degradation proved the matrix tolerance of the introduced method.

  7. Probing the Repulsive Core of the Nucleon-Nucleon Interaction via the 4He(e,e`pN) Triple-Coincidence Reaction

    DOE PAGES

    Korover, Igor; Muangma, Navaphon; Hen, Or; Shneor, Ran; Sulkosky, Vincent; Kelleher, Aidan; Gilad, Shalev; Higinbotham, Douglas; Piasetzky, Eliazer; Wood, Stephen; et al

    2014-07-01

    We studied simultaneously the 4He(e,e'p), 4He(e,e'pp), and 4He(e,e'pn) reactions at Q2=2 [GeV/c]2 and xB >1, for a (e,e'p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum in a region where the nucleon-nucleon force is expected to change from predominantly tensor to repulsive. Neutron-proton pairs dominate the high-momentum tail ofmore » the nucleon momentum distributions, but their abundance is reduced as the nucleon momentum increases beyond ~500 MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum in the range we studied. Our data are compared with ab-initio calculations of two-nucleon momentum distributions in 4He.« less

  8. A Simple Adsorption Experiment

    ERIC Educational Resources Information Center

    Guirado, Gonzalo; Ayllon, Jose A.

    2011-01-01

    The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent…

  9. Adsorption features of flavonoids on macroporous adsorption resins functionalized with ionic liquids.

    PubMed

    Lou, Song; Di, Duolong

    2012-10-01

    A series of macroporous adsorption resins (MARs) with novel structures is synthesized via Friedel-Crafts catalyzed reaction. The adsorption kinetics of the synthetic resins with respect to the purification effect is systematically investigated by means of the response surface methodology (RSM). The kinetic data cannot be fitted to the classical model because it does not take multicompartments and desorption rates into consideration. A new multicompartment louver-tide theory is thus developed considering that adsorption is an indefinite dynamic equilibrium process, which can be divided into innumerable ingredients with different desorption rates. This theory produces much better fits to the experimental data and provides a quantitative explanation with multicompartments and adsorption/desorption rates. PMID:22811393

  10. Evaluation of the adsorption capacity of alkali-treated waste materials for the adsorption of sulphamethoxazole.

    PubMed

    Kurup, Lisha

    2012-01-01

    The present work is to develop potential adsorbents from waste material and employ them for the removal of a hazardous antibacterial, sulphamethoxazole, from the wastewater by the Adsorption technique. The Adsorption technique was used to impound the dangerous antibiotics from wastewater using Deoiled Soya (DOS), an agricultural waste, and Water Hyacinth (WH), a prolific colonizer. The adsorption capacity of these adsorbents was further enhanced by treating them with sodium hydroxide solution and it was seen that the adsorption capacity increases by 10 to 25%. Hence a comparative account of the adsorption studies of all the four adsorbents, i.e. DOS, Alkali-treated DOS, WH and Alkali-treated Water Hyacinth has been discussed in this paper. Different isotherms like Freundlich, Langmuir and Dubinin-Radushkevich were also deduced from the adsorption data. Isotherm studies were in turn used in estimating the thermodynamic parameters. DOS showed sorption capacity of 0.0007 mol g(-1) while Alkali-treated Deoiled Soya exhibited 0.0011 mol g(-1) of sorption capacity, which reveals that the adsorption is higher in case of alkali-treated adsorbent. The mean sorption energy (E) was obtained between 9 and 12 kJ mol, which shows that the reaction proceeds by ion exchange reaction. Kinetic study reveals that the reaction follows pseudo-second-order rate equation. Moreover, mass transfer studies performed for the ongoing processes show that the mass transfer coefficient obtained for alkali-treated moieties was higher than the parent moieties. The breakthrough curves plotted from the column studies show percentage saturation of 90-98%. About 87-97% of sulphamethoxazole was recovered from column by desorption. PMID:22508113

  11. Adsorption and desorption characteristics of arsenic onto ceria nanoparticles

    PubMed Central

    2012-01-01

    The rapid increase in the use of engineered nanoparticles [ENPs] has resulted in an increasing concern over the potential impacts of ENPs on the environmental and human health. ENPs tend to adsorb a large variety of toxic chemicals when they are emitted into the environment, which may enhance the toxicity of ENPs and/or adsorbed chemicals. The study was aimed to investigate the adsorption and desorption behaviors of arsenic on ceria NPs in aqueous solution using batch technique. Results show that the adsorption behavior of arsenic on ceria NPs was strongly dependent on pH and independent of ionic strength, indicating that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical reactions. The adsorption isotherms fitted very well to both the Langmuir and Freundlich models. The thermodynamic parameters (ΔH0, ΔS0, and ΔG0) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment. PMID:22269298

  12. Surface-enhanced Raman scattering (SERS) dosimeter and probe

    DOEpatents

    Vo-Dinh, Tuan

    1995-01-01

    A dosimeter and probe for measuring exposure to chemical and biological compounds is disclosed. The dosimeter or probe includes a collector which may be analyzed by surface-enhanced Raman spectroscopy. The collector comprises a surface-enhanced Raman scattering-active material having a coating applied thereto to improve the adsorption properties of the collector. The collector may also be used in automated sequential devises, in probe array devices.

  13. Surface-enhanced Raman scattering (SERS) dosimeter and probe

    DOEpatents

    Vo-Dinh, T.

    1995-03-21

    A dosimeter and probe for measuring exposure to chemical and biological compounds is disclosed. The dosimeter or probe includes a collector which may be analyzed by surface-enhanced Raman spectroscopy. The collector comprises a surface-enhanced Raman scattering-active material having a coating applied thereto to improve the adsorption properties of the collector. The collector may also be used in automated sequential devices, in probe array devices. 10 figures.

  14. Thiol Reactive Probes and Chemosensors

    PubMed Central

    Peng, Hanjing; Chen, Weixuan; Cheng, Yunfeng; Hakuna, Lovemore; Strongin, Robert; Wang, Binghe

    2012-01-01

    Thiols are important molecules in the environment and in biological processes. Cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H2S) play critical roles in a variety of physiological and pathological processes. The selective detection of thiols using reaction-based probes and sensors is very important in basic research and in disease diagnosis. This review focuses on the design of fluorescent and colorimetric probes and sensors for thiol detection. Thiol detection methods include probes and labeling agents based on nucleophilic addition and substitution, Michael addition, disulfide bond or Se-N bond cleavage, metal-sulfur interactions and more. Probes for H2S are based on nucleophilic cyclization, reduction and metal sulfide formation. Thiol probe and chemosensor design strategies and mechanism of action are discussed in this review. PMID:23202239

  15. Molecular Imaging Probe Development using Microfluidics

    PubMed Central

    Liu, Kan; Wang, Ming-Wei; Lin, Wei-Yu; Phung, Duy Linh; Girgis, Mark D.; Wu, Anna M.; Tomlinson, James S.; Shen, Clifton K.-F.

    2012-01-01

    In this manuscript, we review the latest advancement of microfluidics in molecular imaging probe development. Due to increasing needs for medical imaging, high demand for many types of molecular imaging probes will have to be met by exploiting novel chemistry/radiochemistry and engineering technologies to improve the production and development of suitable probes. The microfluidic-based probe synthesis is currently attracting a great deal of interest because of their potential to deliver many advantages over conventional systems. Numerous chemical reactions have been successfully performed in micro-reactors and the results convincingly demonstrate with great benefits to aid synthetic procedures, such as purer products, higher yields, shorter reaction times compared to the corresponding batch/macroscale reactions, and more benign reaction conditions. Several ‘proof-of-principle’ examples of molecular imaging probe syntheses using microfluidics, along with basics of device architecture and operation, and their potential limitations are discussed here. PMID:22977436

  16. Conductivity Probe

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Thermal and Electrical Conductivity Probe (TECP) for NASA's Phoenix Mars Lander took measurements in Martian soil and in the air.

    The needles on the end of the instrument were inserted into the Martian soil, allowing TECP to measure the propagation of both thermal and electrical energy. TECP also measured the humidity in the surrounding air.

    The needles on the probe are 15 millimeters (0.6 inch) long.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  17. Adsorption behavior of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) on boehmite.

    PubMed

    Wang, Fei; Liu, Chengshuai; Shih, Kaimin

    2012-11-01

    Understanding the interaction of perfluorochemicals, persistent pollutants with known human health effects, with mineral compounds in surface water and groundwater environments is essential to determining their fate and transport. Kinetic experiments showed that adsorption equilibrium can be achieved within 48 h and the boehmite (AlOOH) surface is receptive to perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorption. The adsorption isotherms estimated the maximum adsorption capacities of PFOS and PFOA on boehmite as 0.877 μg m(-2) and 0.633 μg m(-2), respectively. Compared to the adsorption capacity on γ-alumina, the abundant hydroxyl groups on boehmite surfaces resulted in the 2-3 times higher adsorption of PFOS and PFOA. Increasing solution pH led to a moderate decrease in PFOS and PFOA adsorption, owing to an increase in ligand exchange reactions and the decrease of electrostatic interactions. The presence of NaCl and CaCl(2) in solution demonstrated negative effects for PFOS and PFOA adsorption on boehmite surfaces, with potential mechanisms being electrical double layer compression, competitive adsorption of chloride, and the Ca(2+) bridging effect between perfluorochemicals. PMID:22897837

  18. Pollution Probe.

    ERIC Educational Resources Information Center

    Chant, Donald A.

    This book is written as a statement of concern about pollution by members of Pollution Probe, a citizens' anti-pollution group in Canada. Its purpose is to create public awareness and pressure for the eventual solution to pollution problems. The need for effective government policies to control the population explosion, conserve natural resources,…

  19. Effects of adsorption and confinement on nanoporous electrochemistry.

    PubMed

    Bae, Je Hyun; Han, Ji-Hyung; Han, Donghyeop; Chung, Taek Dong

    2013-01-01

    Characteristic molecular dynamics of reactant molecules confined in the space of the nanometer scale augments the frequency of collisions with the electrified surface so that a given faradaic reaction can be enhanced at nanoporous electrodes, the so-called nano-confinement effect. Since this effect is grounded on diffusion inside nanopores, it is predicted that adsorption onto the surface will seriously affect the enhancement by nano-confinement. We experimentally explored the correlation between adsorption and the confinement effect by examining the oxidation of butanol isomers at platinum and gold nanoporous electrodes. The results showed that electrooxidation of 2-butanol, which is a non-adsorption reaction, was enhanced more than that of 1-butanol, which is an adsorption reaction, at nanoporous platinum in acidic media. In contrast, the nanoporous gold electrode, on which 1-butanol is less adsorptive than it is on platinum, enhanced the electrooxidation of 1-butanol greatly. Furthermore, the electrocatalytic activity of nanoporous gold for oxygen reduction reaction was improved so much as to be comparable with that of flat Pt. These findings show that the nano-confinement effect can be appreciable for electrocatalytic oxygen reduction as well as alcohol oxidation unless the adsorption is extensive, and suggests a new strategy in terms of material design for innovative non-noble metal electrocatalysts.

  20. Transient UV pump-IR probe investigation of heterocyclic ring-opening dynamics in the solution phase: the role played by nσ* states in the photoinduced reactions of thiophenone and furanone.

    PubMed

    Murdock, Daniel; Harris, Stephanie J; Luke, Joel; Grubb, Michael P; Orr-Ewing, Andrew J; Ashfold, Michael N R

    2014-10-21

    The heterocyclic ring-opening dynamics of thiophenone and furanone dissolved in CH3CN have been probed by ultrafast transient infrared spectroscopy. Following irradiation at 267 nm (thiophenone) or 225 nm (furanone), prompt (τ < 1 ps) ring-opening is confirmed by the appearance of a characteristic antisymmetric ketene stretching feature around 2150 cm(-1). The ring-opened product molecules are formed highly vibrationally excited, and cool subsequently on a ∼6.7 ps timescale. By monitoring the recovery of the parent (S0) bleach, it is found that ∼60% of the initially photoexcited thiophenone molecules reform the parent molecule, in stark contrast with the case in furanone where there is less than 10% parent bleach recovery. Complementary ab initio calculations of potential energy cuts along the S-C([double bond, length as m-dash]O) and O-C([double bond, length as m-dash]O) ring-opening coordinate reveals insights into the reaction mechanism, and the important role played by dissociative (n/π)σ* states in the UV-induced photochemistry of such heterocyclic systems. PMID:25175813

  1. Phase 2 Methyl Iodide Deep-Bed Adsorption Tests

    SciTech Connect

    Soelberg, Nick; Watson, Tony

    2014-09-01

    Nuclear fission produces fission products (FPs) and activation products, including iodine-129, which could evolve into used fuel reprocessing facility off-gas systems, and could require off-gas control to limit air emissions to levels within acceptable emission limits. Research, demonstrations, and some reprocessing plant experience have indicated that diatomic iodine can be captured with efficiencies high enough to meet regulatory requirements. Research on the capture of organic iodides has also been performed, but to a lesser extent. Several questions remain open regarding the capture of iodine bound in organic compounds. Deep-bed methyl iodide adsorption testing has progressed according to a multi-laboratory methyl iodide adsorption test plan. This report summarizes the second phase of methyl iodide adsorption work performed according to this test plan using the deep-bed iodine adsorption test system at the Idaho National Laboratory (INL), performed during the second half of Fiscal Year (FY) 2014. Test results continue to show that methyl iodide adsorption using AgZ can achieve total iodine decontamination factors (DFs, ratios of uncontrolled and controlled total iodine levels) above 1,000, until breakthrough occurred. However, mass transfer zone depths are deeper for methyl iodide adsorption compared to diatomic iodine (I2) adsorption. Methyl iodide DFs for the Ag Aerogel test adsorption efficiencies were less than 1,000, and the methyl iodide mass transfer zone depth exceeded 8 inches. Additional deep-bed testing and analyses are recommended to (a) expand the data base for methyl iodide adsorption under various conditions specified in the methyl iodide test plan, and (b) provide more data for evaluating organic iodide reactions and reaction byproducts for different potential adsorption conditions.

  2. Adsorption and regenerative oxidation of trichlorophenol with synthetic zeolite: Ozone dosage and its influence on adsorption performance.

    PubMed

    Zhang, Yongjun; Prigent, Bastien; Geißen, Sven-Uwe

    2016-07-01

    Regeneration of loaded adsorbents is a key step for the sustainability of an adsorption process. In this study, ozone was applied to regenerate a synthetic zeolite for the adsorption of trichlorophenol (TCP) as an organic model pollutant. Three initial concentrations of TCP in water phase were used in adsorption tests. After the equilibrium, zeolite loaded different amounts of TCP was dried and then regenerated with ozone gas. It was found that the adsorption capacity of zeolite was increased through three regeneration cycles. However, the adsorption kinetics was compromised after the regeneration with slightly declined 2nd order reaction constants. The ozone demand for the regeneration was highly dependent on the TCP mass loaded onto the zeolite. It was estimated that the mass ratio of ozone to TCP was 1.2 ± 0.3 g O3/g TCP. PMID:27043379

  3. Effect of Grain Size on Uranium(VI) Surface Complexation Kinetics and Adsorption Additivity

    SciTech Connect

    Shang, Jianying; Liu, Chongxuan; Wang, Zheming; Zachara, John M.

    2011-07-27

    Laboratory experiments were performed to investigate the contribution of variable grain sizes to uranium adsorption/desorption in a sediment collected from the US DOE Hanford site. The sediment was wet-sieved into four size fractions: coarse sand (1-2 mm), medium sand (0.2-1 mm), fine sand (0.05-0.2 mm), and clay/silt fraction (< 0.05mm). For each size fraction and their composite (sediment), batch experiments were performed to determine uranium adsorption isotherms, and stirred flow-cell experiments were conducted to derive kinetic data of uranium adsorption and subsequent desorption. The results showed that uranium adsorption isotherms and adsorption/desorption kinetics were size-specific, reflecting the effects of size-specific adsorption site concentration and kinetic rate constants. The larger-size fraction had a larger mass percentage in the sediment, but with a smaller adsorption site concentration and generally a slower uranium adsorption/desorption rate. The same equilibrium surface complexation reaction and reaction constant could describe uranium adsorption isotherms for all size fractions and the composite after accounting for the effect of adsorption site concentration. Mass-weighted, linear additivity was observed for both uranium adsorption isotherms and adsorption/desorption kinetics in the composite. Our analysis also showed that uranium adsorption site concentration estimated from the adsorption isotherms was 3 orders of magnitude less than a site concentration estimated from sediment surface area and generic site density. One important implication of this study is that grain size distribution may be used to estimate uranium adsorption site, and adsorption/desorption kinetic rates in heterogeneous sediments from a common location.

  4. Probing zeolites by vibrational spectroscopies.

    PubMed

    Bordiga, Silvia; Lamberti, Carlo; Bonino, Francesca; Travert, Arnaud; Thibault-Starzyk, Frédéric

    2015-10-21

    This review addresses the most relevant aspects of vibrational spectroscopies (IR, Raman and INS) applied to zeolites and zeotype materials. Surface Brønsted and Lewis acidity and surface basicity are treated in detail. The role of probe molecules and the relevance of tuning both the proton affinity and the steric hindrance of the probe to fully understand and map the complex site population present inside microporous materials are critically discussed. A detailed description of the methods needed to precisely determine the IR absorption coefficients is given, making IR a quantitative technique. The thermodynamic parameters of the adsorption process that can be extracted from a variable-temperature IR study are described. Finally, cutting-edge space- and time-resolved experiments are reviewed. All aspects are discussed by reporting relevant examples. When available, the theoretical literature related to the reviewed experimental results is reported to support the interpretation of the vibrational spectra on an atomic level.

  5. Neptunium(V) adsorption to calcite

    NASA Astrophysics Data System (ADS)

    Heberling, Frank; Brendebach, Boris; Bosbach, Dirk

    2008-12-01

    The migration behavior of the actinyl ions U(VI)O 22+, Np(V)O 2+ and Pu(V,VI)O 2(+,2+) in the geosphere is to a large extend controlled by sorption reactions (inner- or outer-sphere adsorption, ion-exchange, coprecipitation/structural incorporation) with minerals. Here NpO 2+ adsorption onto calcite is studied in batch type experiments over a wide range of pH (6.0-9.4) and concentration (0.4 μM-40 μM) conditions. pH is adjusted by variation of CO 2 partial pressure. Adsorption is found to be pH dependent with maximal adsorption at pH 8.3 decreasing with increasing and decreasing pH. pH dependence of adsorption decreases with increasing Np(V) concentration. EXAFS data of neptunyl adsorbed to calcite and neptunyl in the supernatant shows differences in the Np(V)-O-yl distance, 1.85 ± 0.01 Å for the adsorbed and 1.82 ± 0.01 Å for the solution species. The equatorial environment of the neptunyl in solution shows about 5 oxygen neighbours at 2.45 ± 0.02 Å. For adsorbed neptunyl there are also about 5 oxygen neighbours at 2.46 ± 0.01 Å. An additional feature in the adsorbed species' R-space spectrum can be related to carbonate neighbours, 3 to 6 carbon backscatterers (C-eq) at 3.05 ± 0.03 Å and 3 to 6 oxygen backscatterers (O-eq2) at 3.31 ± 0.02 Å. The differences in the Np(V)-O-yl distance and the C-eq and O-eq2 backscatterers which are only present for the adsorbed species indicate inner-sphere bonding of the adsorbed neptunyl species to the calcite surface. Experiments on adsorption kinetics indicate that after a fast surface adsorption process a continuous slow uptake occurs which may be explained by incorporation via surface dissolution and reprecipitation processes. This is also indicated by the part irreversibility of the adsorption as shown by increased KD values after desorption compared to adsorption.

  6. Alkali cation specific adsorption onto fcc(111) transition metal electrodes.

    PubMed

    Mills, J N; McCrum, I T; Janik, M J

    2014-07-21

    The presence of alkali cations in electrolyte solutions is known to impact the rate of electrocatalytic reactions, though the mechanism of such impact is not conclusively determined. We use density functional theory (DFT) to examine the specific adsorption of alkali cations to fcc(111) electrode surfaces, as specific adsorption may block catalyst sites or otherwise impact surface catalytic chemistry. Solvation of the cation-metal surface structure was investigated using explicit water models. Computed equilibrium potentials for alkali cation adsorption suggest that alkali and alkaline earth cations will specifically adsorb onto Pt(111) and Pd(111) surfaces in the potential range of hydrogen oxidation and hydrogen evolution catalysis in alkaline solutions.

  7. Probing charge screening dynamics and electrochemical processes at the solid-liquid interface with electrochemical force microscopy.

    PubMed

    Collins, Liam; Jesse, Stephen; Kilpatrick, Jason I; Tselev, Alexander; Varenyk, Oleksandr; Okatan, M Baris; Weber, Stefan A L; Kumar, Amit; Balke, Nina; Kalinin, Sergei V; Rodriguez, Brian J

    2014-05-20

    The presence of mobile ions complicates the implementation of voltage-modulated scanning probe microscopy techniques such as Kelvin probe force microscopy (KPFM). Overcoming this technical hurdle, however, provides a unique opportunity to probe ion dynamics and electrochemical processes in liquid environments and the possibility to unravel the underlying mechanisms behind important processes at the solid-liquid interface, including adsorption, electron transfer and electrocatalysis. Here we describe the development and implementation of electrochemical force microscopy (EcFM) to probe local bias- and time-resolved ion dynamics and electrochemical processes at the solid-liquid interface. Using EcFM, we demonstrate contact potential difference measurements, consistent with the principles of open-loop KPFM operation. We also demonstrate that EcFM can be used to investigate charge screening mechanisms and electrochemical reactions in the probe-sample junction. We further establish EcFM as a force-based imaging mode, allowing visualization of the spatial variability of sample-dependent local electrochemical properties.

  8. Adsorptive removal of PPCPs by biomorphic HAP templated from cotton.

    PubMed

    Huang, Bin; Xiong, Dan; Zhao, Tingting; He, Huan; Pan, Xuejun

    2016-01-01

    Biomorphic nano-hydroxyapatite (HAP) was fabricated by a co-precipitation method using cotton as bio-templates and employed in adsorptive removal of ofloxacin (OFL) and triclosan (TCS) that are two representative pharmaceuticals and personal care products (PPCPs). The surface area and porosity, crystal phase, functional group, morphology and micro-structure of the synthesized HAP were characterized by Brunauer-Emmett-Teller isotherm, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron macroscopic and transmission electron microscopy. The effects of initial pH, ionic strength, initial concentration, contact time and temperature on the removal of PPCPs were studied in a batch experiment. The adsorption of OFL and TCS was rapid and almost accomplished within 50 min. Kinetic studies indicated that the adsorption process of OFL and TCS followed the pseudo-first-order and pseudo-second-order models, respectively. The Freundlich isotherm described the OFL adsorption process well but the adsorption of TCS fitted the Langmuir isotherm better. Thermodynamics and isotherm parameters suggested that both OFL and TCS adsorption were feasible and spontaneous. Hydrogen bond and Lewis acid-base reaction may be the dominating adsorption mechanism of OFL and TCS, respectively. Compared to other adsorbents, biomorphic HAP is environmentally friendly and has the advantages of high adsorption capacity, exhibiting potential application for PPCPs removal. PMID:27387006

  9. Adsorption of mercury on laterite from Guizhou Province, China.

    PubMed

    Yu, Xiaohong; Zhu, Lijun; Guo, Baiwei; He, Shouyang

    2008-01-01

    The adsorption behaviors of Hg(II) on laterite from Guizhou Province, China, were studied and the adsorption mechanism was discussed. The results showed that different mineral compositons in the laterite will cause differences in the adsorption capacity of laterite to Hg(II). Illite and non-crystalloids are the main contributors to enhancing the adsorption capacity of laterite to Hg(II). The pH of the solution is an important factor affecting the adsorption of Hg(II) on laterite. The alkalescent environment (pH 7-9) is favorable to the adsorption of Hg(II). The amount of adsorbed Hg(II) increases with increasing pH. When the pH reaches a certain value, the amount of the adsorbed Hg(II) will reach the maximum level. The amount of adsorbed Hg(II) decreases with increasing pH. The optimal pHs of laterite and kaolinite are 9 and 8, respectively. The optimal initial concentrations of Hg(II) on laterite and kaolinite are 250 and 200 microg/ml, respectively. The adsorption isotherms were described by the Langmuir model. The adsorption of Hg(II) on laterite is a quick process while that of Hg(II) on kaolinite is a slow reaction. Laterite from Guizhou Province is a promising environmental material which can be used in the removal of Hg(II) from wastewater. PMID:19202872

  10. Adsorption of mercury on laterite from Guizhou Province, China.

    PubMed

    Yu, Xiaohong; Zhu, Lijun; Guo, Baiwei; He, Shouyang

    2008-01-01

    The adsorption behaviors of Hg(II) on laterite from Guizhou Province, China, were studied and the adsorption mechanism was discussed. The results showed that different mineral compositons in the laterite will cause differences in the adsorption capacity of laterite to Hg(II). Illite and non-crystalloids are the main contributors to enhancing the adsorption capacity of laterite to Hg(II). The pH of the solution is an important factor affecting the adsorption of Hg(II) on laterite. The alkalescent environment (pH 7-9) is favorable to the adsorption of Hg(II). The amount of adsorbed Hg(II) increases with increasing pH. When the pH reaches a certain value, the amount of the adsorbed Hg(II) will reach the maximum level. The amount of adsorbed Hg(II) decreases with increasing pH. The optimal pHs of laterite and kaolinite are 9 and 8, respectively. The optimal initial concentrations of Hg(II) on laterite and kaolinite are 250 and 200 microg/ml, respectively. The adsorption isotherms were described by the Langmuir model. The adsorption of Hg(II) on laterite is a quick process while that of Hg(II) on kaolinite is a slow reaction. Laterite from Guizhou Province is a promising environmental material which can be used in the removal of Hg(II) from wastewater.

  11. [Adsorption-desorption Characteristics of Fermented Rice Husk for Ferrous and Sulfur Ions].

    PubMed

    Xie, Xiao-mei; Liao, Min; Hua, Jia-yuan; Chen, Na; Zhang, Nan; Xu, Pei-zhi; Xie Kai-zhi; XU, Chang-xu; Liu, Guang-rong

    2015-10-01

    To understand the potential of rice husk to fix Fe2+ and S2- ions, the sorption of Fe2+ and S2- by fermented rice husk was studied by using batch incubation experiments in the present study. The effects of adsorption time, Fe2+ and S2- concentration, pH, the temperature and ionic strength in adsorption reaction solution on the sorption were investigated. Therefore, the stability of Fe2+ and S2- adsorbed by fermented rice husk was further validated by desorption experiments performed under similar conditions as adsorption. The results showed that, the adsorption kinetics of Fe2+ (r = 0.912 1) and S2- (r = 0.901 1) by fermented rice husk fits the Elovich kinetics equation, and Freundlich isotherm model could simulate the isotherm adsorption processes of Fe2+ (R2 = 0.965 1) and S2- (R2 = 0.936 6) on fermented rice husk was better than other models. The adsorption processes on fermented rice husk were non- preferential adsorption for Fe2+ and S2, while the adsorption process of Fe2+ on fermented rice husk was spontaneous reaction and the adsorption process of S2- was non-spontaneous reaction. The adsorption processes of Fe2+ and S2- on fermented rice husk were endothermic process since high temperature could benefit to the adsorption. The adsorption mechanism of Fe2+ on fermented rice husk was mainly controlled by coordination adsorption, the adsorption mechanism of S2- on fermented rice husk was mainly controlled by ligand exchange adsorption. The adsorption processes of Fe2+ and S2- on fermented rice husk showed greater pH adaptability which ranged from 1.50 to 11.50. With the increasing of ionic strength, the amount of adsorbed Fe2+ on fermented rice husk wasincreased in some extent, the amount of adsorbed S2- on fermented rice husk was slightly decreased, which further proved the adsorption of Fe2+ was major in inner sphere complexation and the adsorption of S2- was major in outer complexation. The desorption rates of Fe2+ and S2- which was adsorbed by fermented

  12. [Adsorption-desorption Characteristics of Fermented Rice Husk for Ferrous and Sulfur Ions].

    PubMed

    Xie, Xiao-mei; Liao, Min; Hua, Jia-yuan; Chen, Na; Zhang, Nan; Xu, Pei-zhi; Xie Kai-zhi; XU, Chang-xu; Liu, Guang-rong

    2015-10-01

    To understand the potential of rice husk to fix Fe2+ and S2- ions, the sorption of Fe2+ and S2- by fermented rice husk was studied by using batch incubation experiments in the present study. The effects of adsorption time, Fe2+ and S2- concentration, pH, the temperature and ionic strength in adsorption reaction solution on the sorption were investigated. Therefore, the stability of Fe2+ and S2- adsorbed by fermented rice husk was further validated by desorption experiments performed under similar conditions as adsorption. The results showed that, the adsorption kinetics of Fe2+ (r = 0.912 1) and S2- (r = 0.901 1) by fermented rice husk fits the Elovich kinetics equation, and Freundlich isotherm model could simulate the isotherm adsorption processes of Fe2+ (R2 = 0.965 1) and S2- (R2 = 0.936 6) on fermented rice husk was better than other models. The adsorption processes on fermented rice husk were non- preferential adsorption for Fe2+ and S2, while the adsorption process of Fe2+ on fermented rice husk was spontaneous reaction and the adsorption process of S2- was non-spontaneous reaction. The adsorption processes of Fe2+ and S2- on fermented rice husk were endothermic process since high temperature could benefit to the adsorption. The adsorption mechanism of Fe2+ on fermented rice husk was mainly controlled by coordination adsorption, the adsorption mechanism of S2- on fermented rice husk was mainly controlled by ligand exchange adsorption. The adsorption processes of Fe2+ and S2- on fermented rice husk showed greater pH adaptability which ranged from 1.50 to 11.50. With the increasing of ionic strength, the amount of adsorbed Fe2+ on fermented rice husk wasincreased in some extent, the amount of adsorbed S2- on fermented rice husk was slightly decreased, which further proved the adsorption of Fe2+ was major in inner sphere complexation and the adsorption of S2- was major in outer complexation. The desorption rates of Fe2+ and S2- which was adsorbed by fermented

  13. Modeling the Adsorption of Oxalate onto Montmorillonite.

    PubMed

    Ramos, M Elena; Emiroglu, Caglayan; García, David; Sainz-Díaz, C Ignacio; Huertas, F Javier

    2015-11-01

    In this work, a multiscale modeling of the interaction of oxalate with clay mineral surfaces from macroscale thermodynamic equilibria simulations to atomistic calculations is presented. Previous results from macroscopic adsorption data of oxalate on montmorillonite in 0.01 M KNO3 media at 25 °C within the pH range from 2.5 to 9 have been used to develop a surface complexation model. The experimental adsorption edge data were fitted using the triple-layer model (TLM) with the aid of the FITEQL 4.0 computer program. Surface complexation of oxalate is described by two reactions: >AlOH + Ox(2-) + 2H(+) = >AlOxH + H2O (log K = 14.39) and >AlOH + Ox(2-) + H(+) = >AlOx(-) + H2O (log K = 10.39). The monodentate complex >AlOxH dominated adsorption below pH 4, and the bidentate complex >AlOx(-) was predominant at higher pH values. Both of the proposed inner-sphere oxalate species are qualitatively consistent with previously published diffuse reflectance FTIR spectroscopic results for oxalate on montmorillonite edge surface (Chem. Geol. 2014, 363, 283-292). Atomistic computational studies have been performed to understand the interactions at the molecular level between adsorbates and mineral surface, showing the atomic structures and IR frequency shifts of the adsorption complexes of oxalate with the edge surface of a periodic montmorillonite model. PMID:26444928

  14. Equilibrium, kinetic and thermodynamic studies on the adsorption of phenol onto graphene

    SciTech Connect

    Li, Yanhui; Du, Qiuju; Liu, Tonghao; Sun, Jiankun; Jiao, Yuqin; Xia, Yanzhi; Xia, Linhua; Wang, Zonghua; Zhang, Wei; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai

    2012-08-15

    Graphical abstract: The effect of temperature on phenol adsorbed by graphene shows that the equilibrium adsorption capacity of phenol increases with the increase in temperature from 285 to 333 K. Increasing adsorption capacities with temperature indicates that the adsorption of phenol is controlled by an endothermic reaction. Highlights: ► The graphene has high phenol adsorption capacity. ► The graphene has a high specific surface area of 305 m{sup 2}/g. ► The adsorption capacity is high at acidic pH range. ► The graphene has rapid phenol adsorption rate. ► Phenol adsorption is a spontaneous and endothermic process. -- Abstract: Graphene, a new member of carbon family, has been prepared, characterized and used as adsorbent to remove phenol from aqueous solution. The effect parameters including pH, dosage, contact time, and temperature on the adsorption properties of phenol onto graphene were investigated. The results showed that the maximum adsorption capacity can reach 28.26 mg/g at the conditions of initial phenol concentration of 50 mg/L, pH 6.3 and 285 K. Adsorption data were well described by both Freundlich and Langmuir models. The kinetic study illustrated that the adsorption of phenol onto graphene fit the pseudo second-order model. The thermodynamic parameters indicated that the adsorption of phenol onto graphene was endothermic and spontaneous.

  15. Characterisation of the Ru/MgF2 catalyst with adsorbed O2, NO, CO probe molecules by EPR and IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Goslar, J.; Wojciechowska, M.; Zieliński, M.

    2006-07-01

    Electron paramagnetic resonance (EPR) and infrared (IR) spectroscopy were used to study the formation of ruthenium and adsorbed species appearing on the catalyst during O2, NO, and CO adsorption at room temperature on 1 wt% Ru/MgF2 catalysts prepared from Ru3(CO)12 . Both EPR and IR results provided clear evidence for the interaction between surface ruthenium and probe molecules. No EPR signals due to ruthenium (Ru) species were recorded at 300 and 77 K after H2-reduction of the catalyst at 673 K. However, at 4.2 K a very weak EPR spectrum due to low-spin (4d5) Ru3+ complexes was detected. A weak anisotropic O2 radicals signal with g∣∣=2.017 and g⊥=2.003 superimposed on a broad (ΔBpp=120 mT), slightly asymmetric line at g=2.45(1) was identified after O2 admission to the reduced sample. Adsorption of NO gives only a broad, Gaussian-shaped EPR line at g=2.43(1) indicating that the admission of NO, similarly to O2 adsorption, brings about an oxidation of Ru species in the course of the NO decomposition reaction. Introduction of NO over the CO preadsorbed catalyst leads to EPR spectrum with parameters g⊥=1.996, g∣∣=1.895, and A⊥N=2.9 mT assigned to surface NO species associated with Ru ions. The IR spectra recorded after adsorption of NO or CO probe molecules showed the bands in the range of frequency characteristic of ruthenium nitrosyl, nitro, and nitrate/nitrite species and the bands characteristic of ruthenium mono-and multicarbonyls, respectively. Addition of CO after NO admission to the catalyst leads to appearance in the IR spectrum, beside the ones characteristic of NO adsorption, the bands which can be attributed to Ru CO2 and Ru NCO species, indicating that the reaction between NO and CO occurs. These species were also detected after CO adsorption followed by NO adsorption, additionally to the band at 1850 cm-1 being due to cis type ▪ species.

  16. New Adsorption Methods.

    ERIC Educational Resources Information Center

    Wankat, Phillip C.

    1984-01-01

    Discusses a simple method for following the movement of a solute in an adsorption or ion exchange system. This movement is used to study a variety of operational methods, including continuous flow and pulsed flow counter-current operations and simulated counter-current systems. Effect of changing thermodynamic variables is also considered. (JM)

  17. Sulfate adsorption on goethite

    SciTech Connect

    Rietra, R.P.J.J.; Hiemstra, T.; Riemsdijk, W.H. van

    1999-10-15

    Recent spectroscopic work has suggested that only one surface species of sulfate is dominant on hematite. Sulfate is therefore a very suitable anion to test and develop adsorption models for variable charge minerals. The authors have studied sulfate adsorption on goethite covering a large range of sulfate concentrations, surface coverages, pH values, and electrolyte concentrations. Four different techniques were used to cover the entire range of conditions. For characterization at low sulfate concentrations, below the detection limit of sulfate with ICP-AES, the authors used proton-sulfate titrations at constant pH. Adsorption isotherms were studied for the intermediate sulfate concentration range. Acid-base titrations in sodium sulfate and electromobility were used for high sulfate concentrations. All the data can be modeled with one adsorbed species if it is assumed that the charge of adsorbed sulfate is spatially distributed in the interface. The charge distribution of sulfate follows directly from modeling the proton-sulfate adsorption stoichoimemtry sine this stoichiometry is independent of the intrinsic affinity constant of sulfate. The charge distribution can be related to the structure of the surface complex by use of the Pauling bond valence concept and is in accordance with the microscopic structure found by spectroscopy. The intrinsic affinity constant follows from the other measurements. Modeling of the proton-ion stoichoimetry with the commonly used 2-pK models, where adsorbed ions are treated as point charges, is possible only if at least two surface species for sulfate are used.

  18. SEPARATION BY ADSORPTION

    DOEpatents

    Lowe, C.S.

    1959-06-16

    Separation of Pu from fission products by adsorption on hydrous aluminum silicate is described. The Pu in a HNO/sub 3/ solution is oxidized to the hexavalent state and contacted with the silicate which adsorbs fission products. (T.R.H.)

  19. Enhanced adsorptive removal of toxic dyes using SiO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Batool, S. S.; Imran, Z.; Hassan, Safia; Rasool, Kamran; Ahmad, Mushtaq; Rafiq, M. A.

    2016-05-01

    Electrospinning method was used to synthesize porous SiO2 nanofibers. The adsorption of Methyl Orange and Safranin O by porous SiO2 nanofibers was carried out by varying the parameters such as pH, contact time, adsorbent dose, dye concentration, and temperature. Equilibrium adsorption data followed Langmuir isotherms. Kinetic adsorption followed second-order rate kinetics model. The maximum adsorption capacity for Methyl Orange and Safranin O was found to be 730.9 mg/g and 960.4 mg/g, respectively. Acidic pH was favorable for the adsorption of Methyl Orange while basic pH was favorable for the adsorptions of Safranin O. Modeling study suggested the major mode of adsorption, while thermodynamic study showed the endothermic reactions. This effort has pronounced impact on environmental applications of SiO2 nanofibers as auspicious adsorbent nanofibers for organic material from aqueous solution.

  20. Enhanced adsorptive removal of toxic dyes using SiO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Batool, S. S.; Imran, Z.; Hassan, Safia; Rasool, Kamran; Ahmad, Mushtaq; Rafiq, M. A.

    2016-05-01

    Electrospinning method was used to synthesize porous SiO2 nanofibers. The adsorption of Methyl Orange and Safranin O by porous SiO2 nanofibers was carried out by varying the parameters such as pH, contact time, adsorbent dose, dye concentration, and temperature. Equilibrium adsorption data followed Langmuir isotherms. Kinetic adsorption followed second-order rate kinetics model. The maximum adsorption capacity for Methyl Orange and Safranin O was found to be 730.9 mg/g and 960.4 mg/g, respectively. Acidic pH was favorable for the adsorption of Methyl Orange while basic pH was favorable for the adsorptions of Safranin O. Modeling study suggested the major mode of adsorption, while thermodynamic study showed the endothermic reactions. This effort has pronounced impact on environmental applications of SiO2 nanofibers as auspicious adsorbent nanofibers for organic material from aqueous solution.

  1. Adsorption and Separation Modeling of Porous Networks

    NASA Astrophysics Data System (ADS)

    Malanoski, Anthony; van Swol, Frank

    2001-03-01

    With the advent of self-assembly techniques has come the potential to tailor materials for adsorption and separation applications. For example, using surfactants as templating agents it is now feasible to finely control both the three-dimensional (3D) porosity as well as the surface chemistry. With an eye on assisting the emerging materials design we have embarked on a program that focuses on modeling adsorption/desorption, reactions and permeation phenomena in such structures. What makes the modeling particularly challenging is the coupling of length scales. The role of the atomic length scale features such as surface reactions and surface structure must be captured as well as the role of the network connectivity and other larger length scales. The latter include the pore shape and length, and the presence of external surfaces. This paper reports on how we employ refineable lattice models to tackle the modeling problems. We use both equilibrium and non-equilibrium Monte Carlo (MC) and 3D density functional theory (DFT) techniques to study the equilibrium and transport behavior in nanostructured porous materials. We will present 1) results of both adsorption/desorption hysteresis in large regular and random networks and 2) the results of using reactive sites in separation membranes, and compare these with experiments.

  2. Soft X-ray spectroscopy studies of adsorption and reaction of CO in the presence of H2 over 6 nm MnO nanoparticles supported on mesoporous Co3O4

    NASA Astrophysics Data System (ADS)

    Ralston, Walter T.; Musselwhite, Nathan; Kennedy, Griffin; An, Kwangjin; Horowitz, Yonatan; Cordones, Amy A.; Rude, Bruce; Ahmed, Musahid; Melaet, Gerome; Alayoglu, Selim

    2016-06-01

    MnO nanoparticles (6 nm) were supported on mesoporous spinel Co3O4 and studied using ambient pressure X-ray photoelectron spectroscopy (APXPS) and in situ X-ray absorption spectroscopy (XAS) during hydrogenation of CO. The nature and evolution of surface adsorbed species as well as the oxidation states of the metal oxide surfaces were evaluated under oxidizing, reducing, and H2 + CO (2:1) reaction atmospheres. From APXPS, MnO nanoparticle surfaces were found to be progressively reduced in H2 atmospheres with increasing temperature. Surface adsorbed CO was found to be formed at the expense of lattice O under H2 + CO reaction conditions. In situ XAS indicated that the dominant oxide species were Co(OH)2, Co (II) oxides, MnO, and Mn3O4 under reaction conditions. In situ XAS also indicated the formation of gas phase CO2, the disappearance of lattice O, and the further reduction of Mn3O4 to MnO upon prolonged reaction in H2 + CO. Mass spectroscopy measurements showed the formation of CO2 and hydrocarbons. The spent catalyst was investigated using scanning transmission X-ray microscopy and (scanning) transmission electron microscopy; the catalyst grains were found to be homogeneous.

  3. NO adsorption and dissociation on palladium clusters: The importance of charged state and metal doping

    NASA Astrophysics Data System (ADS)

    Gao, Yang; Zhang, Li Mei; Kong, Chun Cai; Yang, Zhi Mao; Chen, Yong Mei

    2016-08-01

    The NO adsorption and dissociation on neutral, charged and Ni-doped Pd13 clusters were studied by using density functional calculations. Our results revealed that NO always prefers to adsorb on the hollow site rather than the top or bridge sites. However, the charge state and Ni doping remarkably influence NO adsorption energy, dissociation barrier and reaction energy. The reaction on Pd13- has the lowest energy barrier and largest reaction energy. The Hirshfeld charge analysis discloses that the origin of the catalytic activity difference is the charge transfer from clusters to NO in the metastable NO adsorption state.

  4. Carbonaceous materials for adsorptive refrigerators

    NASA Astrophysics Data System (ADS)

    Buczek, B.; Wolak, E.

    2012-06-01

    Carbon monoliths prepared from hard coal precursors were obtained. The porous structure of the monoliths was evaluated on the basis of nitrogen adsorption — desorption equilibrium data. The investigated monoliths have a well-developed microporous structure with significant specific surface area (S BET ). Equilibrium studies of methanol vapour adsorption were used to characterize the methanol adsorptive capacity that was determined using a volumetric method. The heat of wetting by methanol was determined in order to estimate the energetic effects of the adsorption process. The results of the investigations show that all monoliths exhibit high adsorption capacity and high heat of wetting with methanol.

  5. Adsorption of Atmospheric Gases on Pu Surfaces

    SciTech Connect

    Nelson, A J; Holliday, K S; Stanford, J A; Grant, W K; Erler, R G; Allen, P G; McLean, W; Roussel, P

    2012-03-29

    Surface adsorption represents a competition between collision and scattering processes that depend on surface energy, surface structure and temperature. The surface reactivity of the actinides can add additional complexity due to radiological dissociation of the gas and electronic structure. Here we elucidate the chemical bonding of gas molecules adsorbed on Pu metal and oxide surfaces. Atmospheric gas reactions were studied at 190 and 300 K using x-ray photoelectron spectroscopy. Evolution of the Pu 4f and O 1s core-level states were studied as a function of gas dose rates to generate a set of Langmuir isotherms. Results show that the initial gas dose forms Pu{sub 2}O{sub 3} on the Pu metal surface followed by the formation of PuO{sub 2} resulting in a layered oxide structure. This work represents the first steps in determining the activation energy for adsorption of various atmospheric gases on Pu.

  6. Methylene blue adsorption on graphene oxide/calcium alginate composites.

    PubMed

    Li, Yanhui; Du, Qiuju; Liu, Tonghao; Sun, Jiankun; Wang, Yonghao; Wu, Shaoling; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

    2013-06-01

    Graphene oxide has been used as an adsorbent in wastewater treatment. However, the dispersibility in aqueous solution and the biotoxicity to human cells of graphene oxide limits its practical application in environmental protection. In this research, a novel environmental friendly adsorbent, calcium alginate immobilized graphene oxide composites was prepared. The effects of pH, contact time, temperature and dosage on the adsorption properties of methylene blue onto calcium alginate immobilized graphene oxide composites were investigated. The equilibrium adsorption data were described by the Langmuir and Freundlich isotherms. The maximum adsorption capacity obtained from Langmuir isotherm equation was 181.81 mg/g. The pseudo-first order, pseudo-second order, and intraparticle diffusion equation were used to evaluate the kinetic data. Thermodynamic analysis of equilibriums indicated that the adsorption reaction of methylene blue onto calcium alginate immobilized graphene oxide composites was exothermic and spontaneous in nature.

  7. Probing the transition state region in catalytic CO oxidation on Ru

    SciTech Connect

    Ostrom, H.; Oberg, H.; Xin, H.; LaRue, J.; Beye, M.; Dell'Angela, M.; Gladh, J.; Ng, M. L.; Sellberg, J. A.; Kaya, S.; Mercurio, G.; Nordlund, D.; Hantschmann, M.; Hieke, F.; Kuhn, D.; Schlotter, W. F.; Dakovski, G. L.; Turner, J. J.; Minitti, M. P.; Mitra, A.; Moeller, S. P.; Fohlisch, A.; Wolf, M.; Wurth, W.; Persson, M.; Norskov, J. K.; Abild-Pedersen, F.; Ogasawara, H.; Pettersson, L. G. M.; Nilsson, A.

    2015-02-12

    Femtosecond x-ray laser pulses are used to probe the CO oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and O on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the O K-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC–O bond lengths close to the transition state (TS). After 1 ps, 10% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model.

  8. Problems affecting the fidelity of pressure measuring instruments for planetary probes

    NASA Technical Reports Server (NTRS)

    Hudson, J. B.

    1972-01-01

    Determination is made of the nature and magnitude of surface-related effects that cause errors in pressure measuring instruments, with special reference being made to instruments intended for use in planetary probes. The interaction of gases with clean surfaces of metals likely to be used as gage construction materials was studied. Special emphasis was placed on the adsorption, chemical reaction, and electron-induced desorption processes. The results indicated that all metals tested were subject to surface processes which would degrade gage fidelity. It was also found, however, that the formation of inert adsorbed layers on these metal surfaces, such as carbon on platinum, greatly reduced or eliminated these effects. This process, combined with a system design which avoids contact between reactive gases and hot filaments, appears to offer the most promising solution to the gage fidelity problem.

  9. Adsorption edge study about cadmium, copper, nickel and zinc adsorption by variable charge soils

    NASA Astrophysics Data System (ADS)

    Casagrande, J. C.; Mouta, E. R.; Soares, M. R.

    2009-04-01

    The improper discharge of industrial and urban residues and the inadvertent use of fertilizers and pesticides can result in soil and water pollution and improve the potential of trace metals to enter in the human food chain. Adsorption reactions occur at the solid/liquid interface and are the most important mechanisms for controlling the activity of metal ions in soil solution. In a complex system with amphoteric behavior, the comprehension of the mobility, availability and fate of pollutants in the soil system is crucial for the prediction of the environmental consequences and for development of prevention/remediation strategies. A comparative study of cadmium (Cd), copper (Cu), nickel (Ni) and zinc (Zn) adsorption by highly weathered soils was carried out. Surface (0-0.2m) and subsoil (B horizon) samples were taken from a Rhodic Kandiudalf (RH), an Anionic "Xanthic" Acrudox (XA) and an Anionic "Rhodic" Acrudox (RA), located in brazilian humid tropical area. As the pH and the ionic strength are important environmental factors influencing the solution chemistry of heavy metals in variable charge systems, adsorption envelopes, in a batch adsorption experiment, were elaborated by reacting, for 24 h, soil samples with individual 0.01, 0.1 and 1.0 mol L-1 Ca(NO3)2 aqueous solutions containing nitrate salts of the adsorptive heavy metal (Cd, Cu, Ni and Zn) at the initial concentration of 5 mg L-1, with an increasing pH value from 3.0 to 8.0. pH50-100%, the difference between the pH of 100 and 50 percent metal adsorption was determined. A sharp increase of adsorption density (adsorption edge) was observed within a very narrow pH range, usually less than two pH units. Commonly, the relative affinity of a soil for a metal cation increases with the tendency of the cation to form inner-sphere surface complexes. This may be caused by differences in extent of hydrolysis of Cu ions and in affinity of adsorption sites for Cu. In general, subsurface samples showed low pH50

  10. Role of organic matter on boron adsorption-desorption hysteresis of soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study we evaluated the boron (B) adsorption/desorption reaction in six soils and examined the extent to which organic matter content, as well as incubation time affected B release. Six soils varying in initial pH, clay content, and were selected for the study. Adsorption experiments were c...

  11. Application of surface complexation models to anion adsorption by natural materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Various chemical models of ion adsorption will be presented and discussed. Chemical models, such as surface complexation models, provide a molecular description of anion adsorption reactions using an equilibrium approach. Two such models, the constant capacitance model and the triple layer model w...

  12. Comparisons of kinetics, thermodynamics and regeneration of tetramethylammonium hydroxide adsorption in aqueous solution with graphene oxide, zeolite and activated carbon

    NASA Astrophysics Data System (ADS)

    Chang, Shenteng; Lu, Chungsying; Lin, Kun-Yi Andrew

    2015-01-01

    Graphene oxide (GO), sodium Y-type zeolite (NaY) and granular activated carbon (GAC) are selected as adsorbents to study their kinetics, thermodynamics and regeneration of tetramethylammonium hydroxide (TMAH) adsorption from water. The adsorption kinetics follows the pseudo-second-order rate law while the adsorption thermodynamics shows an exothermic reaction with GO and GAC but displays an endothermic reaction with NaY. The adsorbed TMAH can be readily desorbed from the surface of GO and NaY by 0.05 M NaCl solution. A comparative study on the cyclic TMAH adsorption with GO, NaY and GAC is also conducted and the results reveal that GO exhibits the greatest TMAH adsorption capacity as well as superior reversibility of TMAH adsorption over 10 cycles of adsorption and desorption process. These features indicate that GO is a promising and efficient adsorbent for TMAH removal in wastewater treatment.

  13. Extracorporeal adsorption of endotoxin.

    PubMed

    Staubach, K H; Rosenfeldt, J A; Veit, O; Bruch, H P

    1997-02-01

    In a porcine endotoxin shock model using a continuous intravenous endotoxin infusion of 250 ng/kg body weight per hour, the cardiorespiratory and hematologic parameters were studied while applying a new on-line polymyxin B immobilized adsorption system. This preliminary report shows that the new adsorbent can remove endotoxin selectively from the circulation and confers a good amount of protection from endotoxin-induced cardiopulmonary decompensation as well as hematologic alterations. Survival time could be extended from 216 min to 313 min. Whereas cardiac output and mean arterial pressure declined critically after 3 h in the controls, the treated group remained stable for another 3 h. These data show that endotoxin adsorption by polymyxin B coupled covalently to acrylic spheres as an adjunctive on-line measure in the septic syndrome seems feasible. PMID:10225785

  14. Structural characteristics of modified activated carbons and adsorption of explosives.

    PubMed

    Tomaszewski, W; Gun'ko, V M; Skubiszewska-Zieba, J; Leboda, R

    2003-10-15

    Several series of activated carbons prepared by catalytic and noncatalytic gasification and subsequent deposition of pyrocarbon by pyrolysis of methylene chloride or n-amyl alcohol were studied by FTIR, chromatography, and adsorption methods using nitrogen and probe organics (explosives). The relationships between the textural characteristics of carbon samples and the recovery rates (eta) of explosives on solid-phase extraction (SPE) using different solvents for their elution after adsorption were analyzed using experimental and quantum chemical calculation results. The eta values for nitrate esters, cyclic nitroamines, and nitroaromatics only partially correlate with different adsorbent parameters (characterizing microporosity, mesoporosity, pore size distributions, etc.), polarity of eluting solvents, or characteristics of probe molecules, since there are many factors strongly affecting the recovery rates. Some of the synthesized carbons provide higher eta values than those for such commercial adsorbents as Hypercarb and Envicarb.

  15. Regenerable adsorption system

    NASA Technical Reports Server (NTRS)

    Roychoudhury, Subir (Inventor); Perry, Jay (Inventor); Walsh, Dennis (Inventor)

    2006-01-01

    A method for regenerable adsorption includes providing a substrate that defines at least one layer of ultra short channel length mesh capable of conducting an electrical current therethrough, coating at least a portion of the substrate with a desired sorbent for trace contaminant control or CO.sub.2 sorption, resistively heating the substrate, and passing a flowstream through the substrate and in contact with the sorbent.

  16. [Adsorption Characteristics of Norfloxacin by Biochars Derived from Reed Straw and Municipal Sludge].

    PubMed

    Zhang, Han-yu; Wang, Zhao-wei; Gao, Jun-hong; Zhu, Jun-min; Xie, Chao-ran; Xie, Xiao-yun

    2016-02-15

    Two types of biochars were prepared by pyrolyzing reed straw and municipal sludge at the temperature of 500 degrees C. The structure and properties of biochars were characterized by BET, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and fourier transform infrared spectroscopy ( FTIR ). The effects of pH value, adsorption time, temperature and initial concentration of norfloxacin (NOR) on the adsorption behaviors were determined by single factor experiments, which were used to preliminarily discuss adsorption mechanism. The results showed that the adsorption of NOR onto biochars derived from reed straw and municipal sludge could reach 70% and 60% of the total adsorption within 12 h, respectively; the maximum adsorption capacities of the two biochars were 2.13 mg x g(-1) (biochar derived from reed straw) and 2.09 mg x g(-1) (biochar derived from municipal sludge). The quantities of both absorptions increased with the decreasing solution pH. The two adsorption kinetics of NOR onto biochars followed the pseudo second order kinetic equations, and adsorption isotherms fitted well with the Langmuir equations. Adsorption thermodynamics parameters such as Gibbs free energy (AG), enthalpy (AH) and entropy (AS) indicated that the two adsorptions were endothermic reactions. Infrared spectroscopy analysis indicated that oxygen-containing functional groups on biochars provided NOR molecules with adsorptive sites, which facilitated the formation of hydrogen bonds between NOR and the biochars.

  17. Dynamics and thermodynamics of toxic metals adsorption onto soil-extracted humic acid.

    PubMed

    Shaker, Medhat A; albishri, Hassan M

    2014-09-01

    Humic acids, HA represent a large portion of natural organic matter in soils, sediments and waters. They are environmentally important materials due to their extensive ubiquity and strong complexation ability, which can influence heavy metal removal and transportation in waters. The thermodynamics and kinetics of the adsorption of Cd(II) and Cr(VI) onto solid soil-derived HA have been investigated at optimum conditions of pH (5.5±0.1), metal concentration (10-100mmolL(-1)) and different temperatures (293-323K). The suitability of adsorption models such as Freundlich and Langmuir to equilibrium data was investigated. The adsorption was well described by Langmuir isotherm model in multi-detectable steps. Adsorption sites, i (i=A, B, C) with different capacities, νi are characterized. The stoichiometric site capacity is independent of temperature and equilibrium constant, Ki. Adsorption sites A and B are selectively occupied by Cr(VI) cations while sites A and C are selectively occupied by Cd(II) cations. The thermodynamic parameters of adsorption systems are correlated for each adsorption step. The adsorption is endothermic, spontaneous and favorable. Different kinetic models are applied and the adsorption of these heavy metals onto HA follows pseudo-second-order kinetics and equilibrium is achieved within 24h. The adsorption reaction is controlled by diffusion processes and the type of the adsorption is physical. PMID:24997970

  18. Preparation of titanium peroxide and its selective adsorption property on cationic dyes

    NASA Astrophysics Data System (ADS)

    Zhao, Xiao-guang; Huang, Ji-guo; Wang, Bo; Bi, Qiang; Dong, Li-li; Liu, Xing-juan

    2014-02-01

    Titanium peroxide powder was prepared with the reaction of titanium sulfate and H2O2 and showed good selective adsorption property on cationic dyes. The obtained material was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric and differential scanning calorimetry (TG-DSC). The selective adsorption property was confirmed and evaluated by adsorption experiments of methyl orange (MO), phenol and three kinds of cationic dyes including methylene blue (MB), malachite green (MG) and neutral red (NR). The adsorption was very fast and adsorption equilibrium was reached in a very short time for all three cationic dyes. The adsorption kinetics of MB, MG and NR were studied then. It was found that the adsorption data fitted perfectly with the pseudo-second-order kinetics and the saturated adsorption capacities for MB, MG and NR were 224.37, 251.38 and 327.61 mg/g at 25 °C, respectively. The characterization and adsorption results indicated the controlling mechanism of adsorption processes could be electrostatic adsorption.

  19. [Adsorption Characteristics of Norfloxacin by Biochars Derived from Reed Straw and Municipal Sludge].

    PubMed

    Zhang, Han-yu; Wang, Zhao-wei; Gao, Jun-hong; Zhu, Jun-min; Xie, Chao-ran; Xie, Xiao-yun

    2016-02-15

    Two types of biochars were prepared by pyrolyzing reed straw and municipal sludge at the temperature of 500 degrees C. The structure and properties of biochars were characterized by BET, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and fourier transform infrared spectroscopy ( FTIR ). The effects of pH value, adsorption time, temperature and initial concentration of norfloxacin (NOR) on the adsorption behaviors were determined by single factor experiments, which were used to preliminarily discuss adsorption mechanism. The results showed that the adsorption of NOR onto biochars derived from reed straw and municipal sludge could reach 70% and 60% of the total adsorption within 12 h, respectively; the maximum adsorption capacities of the two biochars were 2.13 mg x g(-1) (biochar derived from reed straw) and 2.09 mg x g(-1) (biochar derived from municipal sludge). The quantities of both absorptions increased with the decreasing solution pH. The two adsorption kinetics of NOR onto biochars followed the pseudo second order kinetic equations, and adsorption isotherms fitted well with the Langmuir equations. Adsorption thermodynamics parameters such as Gibbs free energy (AG), enthalpy (AH) and entropy (AS) indicated that the two adsorptions were endothermic reactions. Infrared spectroscopy analysis indicated that oxygen-containing functional groups on biochars provided NOR molecules with adsorptive sites, which facilitated the formation of hydrogen bonds between NOR and the biochars. PMID:27363161

  20. Methods of producing adsorption media including a metal oxide

    DOEpatents

    Mann, Nicholas R; Tranter, Troy J

    2014-03-04

    Methods of producing a metal oxide are disclosed. The method comprises dissolving a metal salt in a reaction solvent to form a metal salt/reaction solvent solution. The metal salt is converted to a metal oxide and a caustic solution is added to the metal oxide/reaction solvent solution to adjust the pH of the metal oxide/reaction solvent solution to less than approximately 7.0. The metal oxide is precipitated and recovered. A method of producing adsorption media including the metal oxide is also disclosed, as is a precursor of an active component including particles of a metal oxide.

  1. On the physical adsorption of vapors by microporous carbons

    SciTech Connect

    Bradley, R.H. . Inst. of Surface Science and Technology); Rand, B. . Division of Ceramics)

    1995-01-01

    The physical adsorption of nonpolar and polar vapors by active carbons is discussed in relation to pore structure and pore wall chemistry. For nonpolar vapors the Dubinin-Radushkevich equation is used to derive micropore volumes (W[sub 0]), average adsorption energies (E[sub 0]), and micropore widths (L) for a number of systems. These parameters are used to interpret the adsorption behavior of nitrogen which, because it is a relatively small molecule, is frequently used at 77 K to probe porosity and surface area. Results are presented for three carbons from differing precursors, namely, coal, coconut shells, and polyvinylidene chloride (PVDC) to illustrate the applicability of the technique. For the latter carbon increases in micropore size, induced by activation in carbon dioxide, and reductions in accessible pore volume caused by heat treatment in argon are also characterized and related to structural changes. The approach is then extended to the adsorption of larger hydrogen vapors, where the resulting W[sub 0] values may require correction for molecular packing effects which occur in the lower relative pressure regions of the isotherms, i.e., during the filling of ultramicropores. These packing effects are shown to limit the use of the Polanyi characteristic curve for correlating isotherm data for several vapors, of differing molecular size, by one adsorbent. Data for the adsorption of water, which is a strongly polar liquid, have been interpreted using the Dubinin-Serpinsky equation.

  2. Cd adsorption onto Anoxybacillus flavithermus: Surface complexation modeling and spectroscopic investigations

    SciTech Connect

    Burnett, Peta-Gaye; Daughney, Christopher J.; Peak, Derek

    2008-06-09

    Several recent studies have applied surface complexation theory to model metal adsorption behaviour onto mesophilic bacteria. However, no investigations have used this approach to characterise metal adsorption by thermophilic bacteria. In this study, we perform batch adsorption experiments to quantify cadmium adsorption onto the thermophile Anoxybacillus flavithermus. Surface complexation models (incorporating the Donnan electrostatic model) are developed to determine stability constants corresponding to specific adsorption reactions. Adsorption reactions and stoichiometries are constrained using spectroscopic techniques (XANES, EXAFS, and ATR-FTIR). The results indicate that the Cd adsorption behaviour of A. flavithermus is similar to that of other mesophilic bacteria. At high bacteria-to-Cd ratios, Cd adsorption occurs by formation of a 1:1 complex with deprotonated cell wall carboxyl functional groups. At lower bacteria-to-Cd ratios, a second adsorption mechanism occurs at pH > 7, which may correspond to the formation of a Cd-phosphoryl, CdOH-carboxyl, or CdOH-phosphoryl surface complex. X-ray absorption spectroscopic investigations confirm the formation of the 1:1 Cd-carboxyl surface complex, but due to the bacteria-to-Cd ratio used in these experiments, other complexation mechanism(s) could not be unequivocally resolved by the spectroscopic data.

  3. Mechanisms of chromate adsorption on boehmite.

    PubMed

    Johnston, Chad P; Chrysochoou, Maria

    2015-01-01

    Adsorption reactions play an important role in the transport behavior of groundwater contaminants. Molecular-scale information is needed to elucidate the mechanisms by which ions coordinate to soil mineral surfaces. In this study, we characterized the mechanisms of chromate adsorption on boehmite (γ-AlOOH) using a combination of extended X-ray absorption fine structure (EXAFS) measurements, in situ attenuated total reflectance Fourier transform infrared spectroscopy, and quantum chemical calculations. The effects of pH, ionic strength, and aqueous chromate concentration were investigated. Our overall findings were that chromate primarily forms outer-sphere complexes on boehmite over a broad range of pH and aqueous concentrations. Additionally, a small fraction of monodentate and bidentate inner-sphere complexes are present under acidic conditions, as evidenced by two sets of chromate stretching vibrations at approximately 915, 870, and 780cm(-1), and 940, 890, 850, and 780cm(-1), respectively. The bidentate complex is supported by a best-fit CrAl distance in the EXAFS of 3.2Å. Results from DFT also support the formation of monodentate and bidentate complexes, which are predicted to results in Gibbs energy changes of -140.4 and -62.5kJmol(-1), respectively. These findings are consistent with the intermediate binding strength of chromate with respect to similar oxyanions such as sulfate and selenite. Overall, the surface species identified in this work can be used to develop a more accurate stoichiometric framework in mechanistic adsorption models. PMID:24938710

  4. Ultrasensitive, colorimetric detection of microRNAs based on isothermal exponential amplification reaction-assisted gold nanoparticle amplification.

    PubMed

    Li, Ru-Dong; Yin, Bin-Cheng; Ye, Bang-Ce

    2016-12-15

    MicroRNAs (miRNAs) play important roles in a wide range of biological processes, and their aberrant expressions are linked to a large number of human diseases and disorders. In this work, we developed a colorimetric method for rapid, ultrasensitive miRNA detection via isothermal exponential amplification reaction (EXPAR)-assisted gold nanoparticle (AuNP) amplification. The sensing probe designed with a tandem phosphorothioate modification in the backbone of the polyadenines at the 5' terminus was employed to directly assemble onto the surface of AuNP with high adsorption affinity. The recognition domain at the 3' terminus of the sensing probe hybridizes with target miRNAs to trigger EXPAR with exponential signal amplification. With the amplification reaction with the action of DNA polymerase, the sensing probe gradually detaches from the AuNP, resulting in the aggregation of bare AuNPs in the high-salt reaction environment due to lack of DNA protection. The presence of AuNP aggregation is conveniently measured by UV-vis spectroscopy. Our proposed method could provide a linear detection range from 50fM to 10nM with a detection limit of ∼46fM within 60min, and also discriminate a single-nucleotide difference between homologous miRNAs. PMID:27498329

  5. Hydrogen adsorption in metal-decorated silicon carbide nanotubes

    NASA Astrophysics Data System (ADS)

    Singh, Ram Sevak; Solanki, Ankit

    2016-09-01

    Hydrogen storage for fuel cell is an active area of research and appropriate materials with excellent hydrogen adsorption properties are highly demanded. Nanotubes, having high surface to volume ratio, are promising storage materials for hydrogen. Recently, silicon carbide nanotubes have been predicted as potential materials for future hydrogen storage application, and studies in this area are ongoing. Here, we report a systematic study on hydrogen adsorption properties in metal (Pt, Ni and Al) decorated silicon carbide nanotubes (SiCNTs) using first principles calculations based on density functional theory. The hydrogen adsorption properties are investigated by calculations of adsorption energy, electronic band structure, density of states (DOS) and Mulliken charge population analysis. Our findings show that hydrogen adsorptions on Pt, Ni and Al-decorated SiCNTs undergo spontaneous exothermic reactions with significant modulation of electronic structure of SiCNTs in all cases. Importantly, according to the Mulliken charge population analysis, dipole-dipole interaction causes chemisorptions of hydrogen in Pt, Ni and Al decorated SiCNTs with formation of chemical bonds. The study is a platform for the development of metal decorated SiCNTs for hydrogen adsorption or hydrogen storage application.

  6. Scaling Properties of Adsorption Energies for Hydrogen-Containing Molecules on Transition-Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Abild-Pedersen, F.; Greeley, J.; Studt, F.; Rossmeisl, J.; Munter, T. R.; Moses, P. G.; Skúlason, E.; Bligaard, T.; Nørskov, J. K.

    2007-07-01

    Density functional theory calculations are presented for CHx, x=0,1,2,3, NHx, x=0,1,2, OHx, x=0,1, and SHx, x=0,1 adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the adsorption energy of any of the molecules considered scales approximately with the adsorption energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions.

  7. Hydrodynamic ultrasonic probe

    DOEpatents

    Day, Robert A.; Conti, Armond E.

    1980-01-01

    An improved probe for in-service ultrasonic inspection of long lengths of a workpiece, such as small diameter tubing from the interior. The improved probe utilizes a conventional transducer or transducers configured to inspect the tubing for flaws and/or wall thickness variations. The probe utilizes a hydraulic technique, in place of the conventional mechanical guides or bushings, which allows the probe to move rectilinearly or rotationally while preventing cocking thereof in the tube and provides damping vibration of the probe. The probe thus has lower friction and higher inspection speed than presently known probes.

  8. Collagen fiber immobilized Myrica rubra tannin and its adsorption to UO2(2+).

    PubMed

    Liao, Xuepin; Lu, Zhongbi; Du, Xiao; Liu, Xin; Shi, Bi

    2004-01-01

    Tannins, which are rich in ortho-hydroxyl groups, have a high affinity for UO2(2+). In this paper, Myrica rubra tannin was immobilized on collagen fiber by an aldehydic cross-linking reaction to prepare a novel adsorbent for uranium (UO2(2+)) recovery from wastewater. The adsorption equilibrium, the adsorption kinetics, and the effects of temperature and pH on the adsorption equilibrium were investigated in detail. It was found that the Myrica rubra tannin immobilized on collagen fiber exhibits an excellent adsorption capacity for UO2(2+). The adsorption capacity at 293 K and pH 5.0 was as high as 1.19 mmol UO2(2+)/g (283.3 mgU/g) when the initial concentration of UO2(2+) in solution was 7.5 mmol/L. The adsorption isotherms could be described by the Freundlich equation, and the increase of temperature promoted the adsorption to UO2(2+) . The adsorption kinetics data were fitted very well by the pseudosecond-order rate model, and the equilibrium adsorption capacity calculated by the pseudo-second-order rate model was almost the same as that determined by the actual measurement with the error < or = 4%. The pH has a significant effect on the adsorption process. According to our experiments, the suitable pH scope should be 5-8.

  9. Co-adsorption of phosphate and zinc(II) on the surface of ferrihydrite.

    PubMed

    Liu, Jing; Zhu, Runliang; Xu, Tianyuan; Xu, Yin; Ge, Fei; Xi, Yunfei; Zhu, Jianxi; He, Hongping

    2016-02-01

    Ferrihydrite (Fh) is of great importance in affecting the migration and transformation of heavy-metal cations and oxyanions. To advance the understanding of co-adsorption reactions on Fh surface, the co-adsorption of phosphate and Zn(II) from aqueous solution to a synthesized Fh was determined. The batch experiments demonstrated a synergistic adsorption of phosphate and Zn(II) on Fh. In the pH range of 3.5-6, the adsorption of the two contaminants showed strong pH dependence in the single solute adsorption systems, but the dependence alleviated in the simultaneous adsorption system. X-ray photoelectron spectroscopy (XPS) revealed that the chemical shifts of Zn 2p1/2 and Zn 2p3/2 binding energies were more significant than that of P 2p in the single and simultaneous adsorption systems. On the other side, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) observed increased formation of outer- and inner-sphere complexes of phosphate in the simultaneous system. Thus, the synergistic adsorption of the two contaminants could be attributed to the formation of ternary complexes as well as electrostatic interactions, while surface precipitation could not be completely ruled out. On the basis of the results from both the batch adsorption experiments and structural characterization, these two contaminants were likely to form phosphate-bridged ternary complexes (≡Fe-P-Zn) in the simultaneous adsorption system.

  10. Atrazine adsorption removal with nylon6/polypyrrole core-shell nanofibers mat: possible mechanism and characteristics.

    PubMed

    Yang, Bi-Yi; Cao, Yang; Qi, Fei-Fei; Li, Xiao-Qing; Xu, Qian

    2015-01-01

    A functionalized nylon6/polypyrrole core-shell nanofibers mat (PA6/PPy NFM) was prepared via situ polymerization on nylon6 electrospun nanofibers mat (PA6 NFM) template and used as an adsorbent to remove atrazine from aqueous solutions. The core-shell structure of PA6/PPy NFM can be clearly proved under scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The effects of initial solution pH and ionic strength, as well as the comparison of the adsorption capacity of functionalized (PA6/PPy NFM) and non-functionalized (PA6 NFM) adsorbent, were examined to reveal the possible adsorption mechanism. The results indicated that π-π interaction and electrostatic interaction should play a key role in the adsorption process. The kinetics and thermodynamics studies also further elucidated the detailed adsorption characteristics of atrazine removal by PA6/PPy NFM. The adsorption of atrazine could be well described by the pseudo-second-order equation. The adsorption equilibrium data was well fitted with the Freundlich isotherm model with a maximum adsorption capacity value of 14.8 mg/g. In addition, the increase of adsorption rate caused by a temperature increase could be felicitously explained by the endothermic reaction. The desorption results showed that the adsorption capacity remained almost unchanged after six adsorption/desorption cycles. These results suggest that PA6/PPy NFM could be employed as an efficient adsorbent for removing atrazine from contaminated water sources. PMID:25991912

  11. Characteristics of simultaneous ammonium and phosphate adsorption from hydrolysis urine onto natural loess.

    PubMed

    Jiang, Shanqing; Wang, Xiaochang; Yang, Shengjiong; Shi, Honglei

    2016-02-01

    Nutrient recovery from human urine is a promising pretreatment of domestic wastewater and provides a sustainable recyclability of N and P. In this study, batch experiments were conducted to identify the characteristics of natural loess (NL) for the adsorption and recovery of ammonium and phosphate from hydrolysis urine (HU). The adsorption mechanisms, the adsorption kinetics and isotherms, as well as the major influencing factors, such as pH and temperature, were investigated. Results revealed that adsorption of ammonium occurred by means of ion exchange and molecule adsorption with the ≡ Si-OH groups, while phosphate adsorption was based on the calcium phosphate precipitation reaction and formation of inner-sphere complexes with ≡ M-OH groups. The adsorption processes of ammonium and phosphate were well described by the pseudo-second-order kinetic model and the Freundlich isotherm model. Adsorption of phosphate was endothermic, while ammonium adsorption was exothermic. Furthermore, the maximum ammonium and phosphate adsorption capacities of NL was 23.24 mg N g(-1) and 4.01 mg P g(-1) at an initial pH of 9 and 10, respectively. Results demonstrated that nutrient-adsorbed NL used as compound fertilizer or conventional fertilizer superaddition was feasible for its high contents of N and P as well as its environmental friendliness. PMID:26432267

  12. Co-adsorption of phosphate and zinc(II) on the surface of ferrihydrite.

    PubMed

    Liu, Jing; Zhu, Runliang; Xu, Tianyuan; Xu, Yin; Ge, Fei; Xi, Yunfei; Zhu, Jianxi; He, Hongping

    2016-02-01

    Ferrihydrite (Fh) is of great importance in affecting the migration and transformation of heavy-metal cations and oxyanions. To advance the understanding of co-adsorption reactions on Fh surface, the co-adsorption of phosphate and Zn(II) from aqueous solution to a synthesized Fh was determined. The batch experiments demonstrated a synergistic adsorption of phosphate and Zn(II) on Fh. In the pH range of 3.5-6, the adsorption of the two contaminants showed strong pH dependence in the single solute adsorption systems, but the dependence alleviated in the simultaneous adsorption system. X-ray photoelectron spectroscopy (XPS) revealed that the chemical shifts of Zn 2p1/2 and Zn 2p3/2 binding energies were more significant than that of P 2p in the single and simultaneous adsorption systems. On the other side, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) observed increased formation of outer- and inner-sphere complexes of phosphate in the simultaneous system. Thus, the synergistic adsorption of the two contaminants could be attributed to the formation of ternary complexes as well as electrostatic interactions, while surface precipitation could not be completely ruled out. On the basis of the results from both the batch adsorption experiments and structural characterization, these two contaminants were likely to form phosphate-bridged ternary complexes (≡Fe-P-Zn) in the simultaneous adsorption system. PMID:26461439

  13. Atrazine adsorption removal with nylon6/polypyrrole core-shell nanofibers mat: possible mechanism and characteristics

    NASA Astrophysics Data System (ADS)

    Yang, Bi-Yi; Cao, Yang; Qi, Fei-Fei; Li, Xiao-Qing; Xu, Qian

    2015-05-01

    A functionalized nylon6/polypyrrole core-shell nanofibers mat (PA6/PPy NFM) was prepared via situ polymerization on nylon6 electrospun nanofibers mat (PA6 NFM) template and used as an adsorbent to remove atrazine from aqueous solutions. The core-shell structure of PA6/PPy NFM can be clearly proved under scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The effects of initial solution pH and ionic strength, as well as the comparison of the adsorption capacity of functionalized (PA6/PPy NFM) and non-functionalized (PA6 NFM) adsorbent, were examined to reveal the possible adsorption mechanism. The results indicated that π-π interaction and electrostatic interaction should play a key role in the adsorption process. The kinetics and thermodynamics studies also further elucidated the detailed adsorption characteristics of atrazine removal by PA6/PPy NFM. The adsorption of atrazine could be well described by the pseudo-second-order equation. The adsorption equilibrium data was well fitted with the Freundlich isotherm model with a maximum adsorption capacity value of 14.8 mg/g. In addition, the increase of adsorption rate caused by a temperature increase could be felicitously explained by the endothermic reaction. The desorption results showed that the adsorption capacity remained almost unchanged after six adsorption/desorption cycles. These results suggest that PA6/PPy NFM could be employed as an efficient adsorbent for removing atrazine from contaminated water sources.

  14. Characteristics of simultaneous ammonium and phosphate adsorption from hydrolysis urine onto natural loess.

    PubMed

    Jiang, Shanqing; Wang, Xiaochang; Yang, Shengjiong; Shi, Honglei

    2016-02-01

    Nutrient recovery from human urine is a promising pretreatment of domestic wastewater and provides a sustainable recyclability of N and P. In this study, batch experiments were conducted to identify the characteristics of natural loess (NL) for the adsorption and recovery of ammonium and phosphate from hydrolysis urine (HU). The adsorption mechanisms, the adsorption kinetics and isotherms, as well as the major influencing factors, such as pH and temperature, were investigated. Results revealed that adsorption of ammonium occurred by means of ion exchange and molecule adsorption with the ≡ Si-OH groups, while phosphate adsorption was based on the calcium phosphate precipitation reaction and formation of inner-sphere complexes with ≡ M-OH groups. The adsorption processes of ammonium and phosphate were well described by the pseudo-second-order kinetic model and the Freundlich isotherm model. Adsorption of phosphate was endothermic, while ammonium adsorption was exothermic. Furthermore, the maximum ammonium and phosphate adsorption capacities of NL was 23.24 mg N g(-1) and 4.01 mg P g(-1) at an initial pH of 9 and 10, respectively. Results demonstrated that nutrient-adsorbed NL used as compound fertilizer or conventional fertilizer superaddition was feasible for its high contents of N and P as well as its environmental friendliness.

  15. Cd adsorption onto bacterial surfaces: A universal adsorption edge?

    NASA Astrophysics Data System (ADS)

    Yee, Nathan; Fein, Jeremy

    2001-07-01

    In this study, we measure the thermodynamic stability constants for proton and Cd binding onto the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, and the Gram-positive bacteria Bacillus megaturium, Streptococcus faecalis, Staphylococcus aureus, Sporosarcina ureae, and Bacillus cereus. Potentiometric titrations and Cd-bacteria adsorption experiments yield average values for the carboxyl site pK a, site concentration, and log stability constant for the bacterial surface Cd-carboxyl complex of 5.0, 2.0 × 10 -3 mol/g and 4.0 respectively. Our results indicate that a wide range of bacterial species exhibit nearly identical Cd adsorption behavior as a function of pH. We propose that metal-bacteria adsorption is not dependent on the bacterial species involved, and we develop a generalized adsorption model which may greatly simplify the task of quantifying the effects of bacterial adsorption on dissolved mass transport in realistic geologic systems.

  16. Insights into tetracycline adsorption onto kaolinite and montmorillonite: experiments and modeling.

    PubMed

    Zhao, Yanping; Gu, Xueyuan; Li, Shiyin; Han, Ruiming; Wang, Guoxiang

    2015-11-01

    Adsorption of tetracycline (TC) on kaolinite and montmorillonite was investigated using batch adsorption experiments with different pH, ionic strength, and surface coverage. As a result, pH and ionic strength-dependent adsorption of TC was observed for the two clay minerals. The adsorption of TC decreased with the increase of pH and ionic strength, and high initial TC concentration had high adsorption. In addition, a triple-layer model was used to predict the adsorption and surface speciation of TC on the two minerals. As a result, four complex species on kaolinite (≡X(-)∙H3TC(+), ≡X(-)∙H2TC(±), ≡SOH(0)∙H2TC(±), and ≡SOH(0)∙HTC(-)) and three species on montmorillonite (≡X(-)∙H3TC(+), ≡X(-)∙H2TC(±), and ≡SOH(0)∙HTC(-)) were structurally constrained by spectroscopy, and these species were also successfully fitted to the adsorption edges of TC. Three functional groups of TC were involved in these adsorption reactions, including the positively charged dimethylamino group, the C=O amide I group, and the C=O group at the C ring. Combining adsorption experiments and model in this study, the adsorption of TC on kaolinite and montmorillonite was mainly attributed to cation exchange on the surface sites (≡X(-)) compared to surface complexation on the edge sites (≡SOH) at natural soil pH condition. Moreover, the surface adsorption species, the corresponding adsorption modes, and the binding constants for the surface reactions were also estimated.

  17. Insights into tetracycline adsorption onto kaolinite and montmorillonite: experiments and modeling.

    PubMed

    Zhao, Yanping; Gu, Xueyuan; Li, Shiyin; Han, Ruiming; Wang, Guoxiang

    2015-11-01

    Adsorption of tetracycline (TC) on kaolinite and montmorillonite was investigated using batch adsorption experiments with different pH, ionic strength, and surface coverage. As a result, pH and ionic strength-dependent adsorption of TC was observed for the two clay minerals. The adsorption of TC decreased with the increase of pH and ionic strength, and high initial TC concentration had high adsorption. In addition, a triple-layer model was used to predict the adsorption and surface speciation of TC on the two minerals. As a result, four complex species on kaolinite (≡X(-)∙H3TC(+), ≡X(-)∙H2TC(±), ≡SOH(0)∙H2TC(±), and ≡SOH(0)∙HTC(-)) and three species on montmorillonite (≡X(-)∙H3TC(+), ≡X(-)∙H2TC(±), and ≡SOH(0)∙HTC(-)) were structurally constrained by spectroscopy, and these species were also successfully fitted to the adsorption edges of TC. Three functional groups of TC were involved in these adsorption reactions, including the positively charged dimethylamino group, the C=O amide I group, and the C=O group at the C ring. Combining adsorption experiments and model in this study, the adsorption of TC on kaolinite and montmorillonite was mainly attributed to cation exchange on the surface sites (≡X(-)) compared to surface complexation on the edge sites (≡SOH) at natural soil pH condition. Moreover, the surface adsorption species, the corresponding adsorption modes, and the binding constants for the surface reactions were also estimated. PMID:26122570

  18. Arsenate adsorption mechanisms at the allophane - Water interface

    USGS Publications Warehouse

    Arai, Y.; Sparks, D.L.; Davis, J.A.

    2005-01-01

    We investigated arsenate (As(V)) reactivity and surface speciation on amorphous aluminosilicate mineral (synthetic allophane) surfaces using batch adsorption experiments, powder X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). The adsorption isotherm experiments indicated that As(V) uptake increased with increasing [As(V)]0 from 50 to 1000 ??M (i.e., Langmuir type adsorption isotherm) and that the total As adsorption slightly decreased with increasing NaCl concentrations from 0.01 to 0.1 M. Arsenate adsorption was initially (0-10 h) rapid followed by a slow continuum uptake, and the adsorption processes reached the steady state after 720 h. X-ray absorption spectroscopic analyses suggest that As(V) predominantly forms bidentate binuclear surface species on aluminum octahedral structures, and these species are stable up to 11 months. Solubility calculations and powder XRD analyses indicate no evidence of crystalline AI-As(V) precipitates in the experimental systems. Overall, macroscopic and spectroscopic evidence suggest that the As(V) adsorption mechanisms at the allophane-water interface are attributable to ligand exchange reactions between As(V) and surface-coordinated water molecules and hydroxyl and silicate ions. The research findings imply that dissolved tetrahedral oxyanions (e.g., H2PO42- and H2AsO42-) are readily retained on amorphous aluminosilicate minerals in aquifer and soils at near neutral pH. The innersphere adsorption mechanisms might be important in controlling dissolved arsenate and phosphate in amorphous aluminosilicate-rich low-temperature geochemical environments. ?? 2005 American Chemical Society.

  19. Rethinking Critical Adsorption

    NASA Astrophysics Data System (ADS)

    Franck, Carl; Peach, Sarah; Polak, Robert D.

    1996-03-01

    Recent reflectivity experiments on near-critical mixtures of carbon disulfide and nitromethane contained in glass cells footnote Niraj S. Desai, Sarah Peach, and Carl Franck, Phys. Rev. E 52, 4129 (1995) have shown that preferential adsorption of one liquid component onto the wall can be controlled by chemical modification of the glass. The glass was treated with varying amounts of hexamethyldisilazane to decrease surface polarity and therefore enhance the adsorption of carbon disulfide in a surprisingly continuous way. The effect of the glass wall on the local liquid composition can be described by two different scaling hypotheses: using a short range field on the liquid closest to the wall, or pinning the amplitude of the order parameter at the surface. We have found that only the second approach is consistent with the experimental data, although this is difficult to reconcile with observed wetting critical phenomena. We also have reexamined the issue of substrate inhomogeneity and conclude that the substrates were indeed homogeneous on relevant length scales. Supported by the NSF under DMR-9320910 and the central facilities of the Materials Science Center at Cornell University.

  20. Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5.

    PubMed

    Ding, Wenjin; Baracchini, Giulia; Klumpp, Michael; Schwieger, Wilhelm; Dittmeyer, Roland

    2016-01-01

    We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 °C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 °C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 °C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 °C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example. PMID:27585356

  1. Basicity, Catalytic and Adsorptive Properties of Hydrotalcites

    NASA Astrophysics Data System (ADS)

    Figueras, Francois

    Solid bases have numerous potential applications, not only as catalyst for the manufacture of fine chemicals, in refining and petrochemistry, but also for adsorption and anion exchange. The present processes use liquid bases, typically alcoholic potash, and require neutralisation of the reaction medium at the end of the reaction, with production of salts. The substitution of these liquid bases by solids would provide cleaner and safer processes, due to the reduction of salts, and facilitate separation of the products and recycling of the catalyst. This chapter reviews the recent ideas on the modification of the basic properties of hydrotalcites by anion exchange and on the catalytic properties of solid bases as catalysts. Many examples of successful applications are given, with emphasis to industrial processes recently presented such as isomerisation of olefins. The basic properties of hydrotalcites can also be used to carry the exchange of toxic anions, humic acids or dyes, and have driven recent developments proposing HDT as drug carriers.

  2. Global versus local adsorption selectivity

    NASA Astrophysics Data System (ADS)

    Pauzat, Françoise; Marloie, Gael; Markovits, Alexis; Ellinger, Yves

    2015-10-01

    The origin of the enantiomeric excess found in the amino acids present in the organic matter of carbonaceous meteorites is still unclear. Selective adsorption of one of the two enantiomers existing after a racemic formation could be part of the answer. Hereafter we report a comparative study of the adsorption of the R and S enantiomers of α-alanine and lactic acid on the hydroxylated { } chiral surface of α-quartz using numerical simulation techniques. Structurally different adsorption sites were found with opposite R versus S selectivity for the same molecule-surface couple, raising the problem of whether to consider adsorption as a local property or as a global response characteristic of the whole surface. To deal with the second term of this alternative, a statistical approach was designed, based on the occurrence of each adsorption site whose energy was calculated using first principle periodic density functional theory. It was found that R-alanine and S-lactic acid are the enantiomers preferentially adsorbed, even if the adsorption process on the quartz { } surface stays with a disappointingly poor enantio-selectivity. Nevertheless, it highlighted the important point that considering adsorption as a global property changes perspectives in the search for more efficient enantio-selective supports and more generally changes the way to apprehend adsorption processes in astro-chemistry/biology.

  3. Design method for adsorption beds

    NASA Technical Reports Server (NTRS)

    Blakely, R. L.; Jackson, J. K.

    1970-01-01

    Regenerable adsorption beds for long-term life support systems include synthetic geolite to remove carbon dioxide and silica gel to dehumidify the atmospheric gas prior to its passage through the geolite beds. Bed performance is evaluated from adsorption characteristics, heat and mass transfer, and pressure drop.

  4. Liquid-Phase Adsorption Fundamentals.

    ERIC Educational Resources Information Center

    Cooney, David O.

    1987-01-01

    Describes an experiment developed and used in the unit operations laboratory course at the University of Wyoming. Involves the liquid-phase adsorption of an organic compound from aqueous solution on activated carbon, and is relevant to adsorption processes in general. (TW)

  5. Functional nucleic acid probes and uses thereof

    DOEpatents

    Nilsen-Hamilton, Marit

    2006-10-03

    The present invention provides functional nucleic acid probes, and methods of using functional nucleic acid probes, for binding a target to carry out a desired function. The probes have at least one functional nucleic acid, at least one regulating nucleic acid, and at least one attenuator. The functional nucleic acid is maintained in an inactive state by the attenuator and activated by the regulating nucleic acid only in the presence of a regulating nucleic acid target. In its activated state the functional nucleic acid can bind to its target to carry out a desired function, such as generating a signal, cleaving a nucleic acid, or catalyzing a reaction.

  6. Structural study of Fe (II) adsorption on hematite (1102)

    SciTech Connect

    Tanwar, K.S.; Petitto, S.C.; Ghose, S.K.; Eng, P.J.; Trainor, T.P.

    2008-07-15

    The structure of {alpha}-Fe{sub 2}O{sub 3}(1{bar 1}02) reacted with Fe(II) under anoxic conditions was studied using crystal truncation rod (CTR) diffraction. The CTR results show the crystalline termination of {alpha}-Fe{sub 2}O{sub 3}(1{bar 1}02) is modified due to adsorption of Fe(II) at crystallographic lattice sites. In addition, the binding sites for adsorbed Fe are similar for all studied conditions: reaction for 2 h at pH 5.0, for 34 d at pH 5.0, and for 5.5 h at pH 7.0. The occupancy of adsorbed Fe increases with both reaction time and pH, which is consistent with typical cation adsorption behavior on iron (hydr)oxide surfaces. The metal-oxygen bond lengths of the (ordered) surface Fe atoms are characteristic of Fe(III), which provides indirect evidence for oxidation of adsorbed Fe(II) and is consistent with recent studies indicating that Fe(III)-hydroxides are effective oxidants for dissolved ferrous iron. Grazing-incidence X-ray diffraction measurements indicate that no crystalline surface reaction products formed during the course of Fe(II) reaction. Overall, the structural characterization of the Fe(II) adsorption reaction results in an enhanced understanding of how reduced iron affects the structure, stability and reactivity of hematite.

  7. The unique probe selector: a comprehensive web service for probe design and oligonucleotide arrays

    PubMed Central

    Chen, Shu-Hwa; Lo, Chen-Zen; Tsai, Ming-Chi; Hsiung, Chao A; Lin, Chung-Yen

    2008-01-01

    Background Nucleic acid hybridization, a fundamental technique in molecular biology, can be modified into very effective and sensitive methods for detecting particular targets mixed with millions of non-target sequences. Therefore, avoiding cross-hybridization is the most crucial issue for developing diagnostic methods based on hybridization. Results To develop a probe with a high discriminating power, this study constructed a web service, the Unique Probe Selector (UPS), for customized probe design. The UPS service integrates a probe design mechanism and a scoring system for evaluating the performance of probe annealing and the uniqueness of a probe in a user-defined genetic background. Starting from an intuitive web interface, the UPS accepts a query with single or multiple sequences in fasta format. The best probe(s) for each sequence can be downloaded from result pages in a fasta or .csv format with a summary of probe characteristics. The option "Unique probe within group" selects the most unique probe for each target sequence with low probability to hybridize to the other sequences in the same submitted query. The option "Unique probe in the specific organism" devises probes for each submitted sequence to identify its target among selected genetic backgrounds based on Unigene. Conclusion The UPS evaluates probe-to-target hybridization under a user-defined condition in silico to ensure high-performance hybridization and minimizes the possibility of non-specific reactions. UPS has been applied to design human arrays for gene expression studies and to develop several small arrays of gene families that were inferred as molecular signatures of cancer typing/staging or pathogen signatures. Notably, UPS is freely accessible at . PMID:18315861

  8. Adsorption of polycyclic aromatic hydrocarbons by graphene and graphene oxide nanosheets.

    PubMed

    Wang, Jun; Chen, Zaiming; Chen, Baoliang

    2014-05-01

    The adsorption of naphthalene, phenanthrene, and pyrene onto graphene (GNS) and graphene oxide (GO) nanosheets was investigated to probe the potential adsorptive sites and molecular mechanisms. The microstructure and morphology of GNS and GO were characterized by elemental analysis, XPS, FTIR, Raman, SEM, and TEM. Graphene displayed high affinity to the polycyclic aromatic hydrocarbons (PAHs), whereas GO adsorption was significantly reduced after oxygen-containing groups were attached to GNS surfaces. An unexpected peak was found in the curve of adsorption coefficients (Kd) with the PAH equilibrium concentrations. The hydrophobic properties and molecular sizes of the PAHs affected the adsorption of G and GO. The high affinities of the PAHs to GNS are dominated by π-π interactions to the flat surface and the sieving effect of the powerful groove regions formed by wrinkles on GNS surfaces. In contrast, the adsorptive sites of GO changed to the carboxyl groups attaching to the edges of GO because the groove regions disappeared and the polar nanosheet surfaces limited the π-π interactions. The TEM and SEM images initially revealed that after loading with PAH, the conformation and aggregation of GNS and GO nanosheets dramatically changed, which explained the observations that the potential adsorption sites of GNS and GO were unusually altered during the adsorption process.

  9. High temperature adsorption measurements

    SciTech Connect

    Bertani, R.; Parisi, L.; Perini, R.; Tarquini, B.

    1996-12-31

    Adsorption phenomena are a rich and rather new field of study in geothermal research, in particular at very high temperature. ENEL is interested in the exploitation of geothermal regions with super-heated steam, and it is important to understand the behavior of water-rock interaction. We have analyzed in the 170-200{degrees}C temperature range four samples of Monteverdi cuttings; the next experimental effort will be at 220{degrees}C and over in 1996. The first results of the 1995 runs are collected in this paper. We can highlight four main items: (1) At relative pressures over 0.6 the capillarity forces are very important. (2) There is no significant temperature effect. (3) Adsorbed water can be present, and it is able to multiply by a factor of 15 the estimated reserve of super-heated steam only. (4) Pores smaller than 15 {Angstrom} do not contribute to the adsorbed mass.

  10. High temperature adsorption measurements

    SciTech Connect

    Bertani, R.; Parisi, L.; Perini, R.; Tarquini, B.

    1996-01-24

    Adsorption phenomena are a rich and rather new field of study in geothermal research, in particular at very high temperature. ENEL is interested in the exploitation of geothermal regions with superheated steam, and it is important to understand the behavior of water-rock interaction. We have analyzed in the 170-200 °C temperature range four samples of Monteverdi cuttings; the next experimental effort will be at 220 °C and over in 1996. The first results of the 1995 runs are collected in this paper. We can highlight four main items: 1. At relative pressures over 0.6 the capillarity forces are very important. 2. There is no significant temperature effect. 3. Adsorbed water can be present, and it is able to multiply by a factor of 15 the estimated reserve of super-heated steam only. 4. Pores smaller than 15 Å do not contribute to the adsorbed mass.

  11. Selective Filter Effect Induced by Cu(2+) Adsorption on the Fluorescence of a GdVO4:Eu Nanoprobe.

    PubMed

    Kim, Hyunsub; Jeong, Heejin; Byeon, Song-Ho

    2016-06-22

    Human blood contains substantial amounts of metal ions such as Mg(2+), Ca(2+), Fe(2+), Cu(2+), Zn(2+), Cd(2+), Pb(2+), and Al(3+). Most biomedical applications of nanoparticles require understanding the influence of these metal ions because adsorbed metal ions can affect the function of nanoparticles to limit their sensitivity, performance, stability, and/or resolution in applications. In the present work, the adsorption of various metal ions at the surface of GdVO4:Eu nanoparticles was studied to assess their spectral filter effect on the fluorescence of GdVO4:Eu. Due to the negative surface potential, the electrostatic attraction caused an intensive adsorption reaction of GdVO4:Eu nanoparticles with metal cations. Compared to the adsorption of other common metal ions in human blood, the distinct fluorescence quenching of GdVO4:Eu was induced in the presence of Cu(2+) ions. On the basis of the UV-vis absorption spectrum of an aqueous CuCl2 solution and reflectance spectrum of Cu(OH)2, in which the surroundings of Cu(2+) ions are supposedly similar to the hydroxylated surface of GdVO4:Eu nanoparticles, it is proposed that the complementary overlap of the emission band of GdVO4:Eu with the absorption band of Cu(2+) results in the effective filter effect to quench the red emission. Because GdVO4:Eu nanoparticles are attractive candidates for applications as magnetic/fluorescent multimodal nanoprobes, it is important to recognize that the average amount of Cu(2+) ion in human blood is sufficient to interfere with or limit the fluorescence probe function of GdVO4:Eu nanoparticles. PMID:27232597

  12. Infant Defensive Reactions to Visual Occlusion.

    ERIC Educational Resources Information Center

    Adamson, Lauren; Tronick, Edward

    This paper describes the initial organization of the infant's reaction to having his vision occluded by an opaque cloth; traces the development of this reaction over the first six months; and probes the role the occlusion of vision plays in provoking the reaction. Fifty videotaped sessions of infants during two conditions - eyes covered with an…

  13. Modelling metal centres, acid sites and reaction mechanisms in microporous catalysts.

    PubMed

    O'Malley, Alexander J; Logsdail, A J; Sokol, A A; Catlow, C R A

    2016-07-01

    We discuss the role of QM/MM (embedded cluster) computational techniques in catalytic science, in particular their application to microporous catalysis. We describe the methodologies employed and illustrate their utility by briefly summarising work on metal centres in zeolites. We then report a detailed investigation into the behaviour of methanol at acidic sites in zeolites H-ZSM-5 and H-Y in the context of the methanol-to-hydrocarbons/olefins process. Studying key initial steps of the reaction (the adsorption and subsequent methoxylation), we probe the effect of framework topology and Brønsted acid site location on the energetics of these initial processes. We find that although methoxylation is endothermic with respect to the adsorbed system (by 17-56 kJ mol(-1) depending on the location), there are intriguing correlations between the adsorption/reaction energies and the geometries of the adsorbed species, of particular significance being the coordination of methyl hydrogens. These observations emphasise the importance of adsorbate coordination with the framework in zeolite catalysed conversions, and how this may vary with framework topology and site location, particularly suited to investigation by QM/MM techniques. PMID:27136967

  14. FY-2015 Methyl Iodide Deep-Bed Adsorption Test Report

    SciTech Connect

    Soelberg, Nicholas Ray; Watson, Tony Leroy

    2015-09-30

    Nuclear fission produces fission and activation products, including iodine-129, which could evolve into used fuel reprocessing facility off-gas systems, and could require off-gas control to limit air emissions to levels within acceptable emission limits. Deep-bed methyl iodide adsorption testing has continued in Fiscal Year 2015 according to a multi-laboratory methyl iodide adsorption test plan. Updates to the deep-bed test system have also been performed to enable the inclusion of evaporated HNO3 and increased NO2 concentrations in future tests. This report summarizes the result of those activities. Test results showed that iodine adsorption from gaseous methyl iodide using reduced silver zeolite (AgZ) resulted in initial iodine decontamination factors (DFs, ratios of uncontrolled and controlled total iodine levels) under 1,000 for the conditions of the long-duration test performed this year (45 ppm CH3I, 1,000 ppm each NO and NO2, very low H2O levels [3 ppm] in balance air). The mass transfer zone depth exceeded the cumulative 5-inch depth of 4 bed segments, which is deeper than the 2-4 inch depth estimated for the mass transfer zone for adsorbing I2 using AgZ in prior deep-bed tests. The maximum iodine adsorption capacity for the AgZ under the conditions of this test was 6.2% (6.2 g adsorbed I per 100 g sorbent). The maximum Ag utilization was 51%. Additional deep-bed testing and analyses are recommended to (a) expand the data base for methyl iodide adsorption and (b) provide more data for evaluating organic iodide reactions and reaction byproducts for different potential adsorption conditions.

  15. Random sequential adsorption on fractals.

    PubMed

    Ciesla, Michal; Barbasz, Jakub

    2012-07-28

    Irreversible adsorption of spheres on flat collectors having dimension d < 2 is studied. Molecules are adsorbed on Sierpinski's triangle and carpet-like fractals (1 < d < 2), and on general Cantor set (d < 1). Adsorption process is modeled numerically using random sequential adsorption (RSA) algorithm. The paper concentrates on measurement of fundamental properties of coverages, i.e., maximal random coverage ratio and density autocorrelation function, as well as RSA kinetics. Obtained results allow to improve phenomenological relation between maximal random coverage ratio and collector dimension. Moreover, simulations show that, in general, most of known dimensional properties of adsorbed monolayers are valid for non-integer dimensions.

  16. Surface complexation modeling of uranyl adsorption on corrensite from the Waste Isolation Pilot Plant Site

    SciTech Connect

    Park, Sang-Won; Leckie, J.O.; Siegel, M.D.

    1995-09-01

    Corrensite is the dominant clay mineral in the Culebra Dolomite at the Waste Isolation Pilot Plant. The surface characteristics of corrensite, a mixed chlorite/smectite clay mineral, have been studied. Zeta potential measurements and titration experiments suggest that the corrensite surface contains a mixture of permanent charge sites on the basal plane and SiOH and AlOH sites with a net pH-dependent charge at the edge of the clay platelets. Triple-layer model parameters were determined by the double extrapolation technique for use in chemical speciation calculations of adsorption reactions using the computer program HYDRAQL. Batch adsorption studies showed that corrensite is an effective adsorbent for uranyl. The pH-dependent adsorption behavior indicates that adsorption occurs at the edge sites. Adsorption studies were also conducted in the presence of competing cations and complexing ligands. The cations did not affect uranyl adsorption in the range studied. This observation lends support to the hypothesis that uranyl adsorption occurs at the edge sites. Uranyl adsorption was significantly hindered by carbonate. It is proposed that the formation of carbonate uranyl complexes inhibits uranyl adsorption and that only the carbonate-free species adsorb to the corrensite surface. The presence of the organic complexing agents EDTA and oxine also inhibits uranyl sorption.

  17. Simultaneous adsorption of Cd²⁺ and BPA on amphoteric surfactant activated montmorillonite.

    PubMed

    Liu, Chongmin; Wu, Pingxiao; Zhu, Yajie; Tran, Lytuong

    2016-02-01

    The study mainly investigated the simultaneous adsorption of bisphenol A (BPA) and Cd(2+) from aqueous solution on octadecane-betaine modified montmorillonite (BS-Mt). The characteristics of the obtained materials were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Specific surface area (BET) and Scanning electron microscopy/Energy disperse spectroscopy (SEM/EDS), confirming that BS-18 was successfully introduced into Mt. Also, factors including initial solution pH, initial Cd(2+)/BPA concentration, contact time and adsorbent dosage on the adsorption processes were shown to be crucial for Cd(2+) adsorption, whereas had negligible effects on BPA adsorption. In this study, we found that pseudo-second-order model fitted well with the adsorption kinetic studies for both Cd(2+) and BPA with an equilibrium time of 24 h. The Cd(2+) and BPA adsorption isotherm could be well described by Freundlich model and Langmuir model, respectively. On the basis of kinetic models, the maximum adsorption capacity of Cd(2+) in aqueous solution was slightly enhanced after modification, indicating that Cd(2+) adsorption on BS-Mt was mainly attributed to direct electrostatic attraction and the chelate reaction, while the dramatic enhancement of maximum adsorption capacity for BPA was due to the hydrophobic interaction.

  18. Simultaneous adsorption of Cd²⁺ and BPA on amphoteric surfactant activated montmorillonite.

    PubMed

    Liu, Chongmin; Wu, Pingxiao; Zhu, Yajie; Tran, Lytuong

    2016-02-01

    The study mainly investigated the simultaneous adsorption of bisphenol A (BPA) and Cd(2+) from aqueous solution on octadecane-betaine modified montmorillonite (BS-Mt). The characteristics of the obtained materials were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Specific surface area (BET) and Scanning electron microscopy/Energy disperse spectroscopy (SEM/EDS), confirming that BS-18 was successfully introduced into Mt. Also, factors including initial solution pH, initial Cd(2+)/BPA concentration, contact time and adsorbent dosage on the adsorption processes were shown to be crucial for Cd(2+) adsorption, whereas had negligible effects on BPA adsorption. In this study, we found that pseudo-second-order model fitted well with the adsorption kinetic studies for both Cd(2+) and BPA with an equilibrium time of 24 h. The Cd(2+) and BPA adsorption isotherm could be well described by Freundlich model and Langmuir model, respectively. On the basis of kinetic models, the maximum adsorption capacity of Cd(2+) in aqueous solution was slightly enhanced after modification, indicating that Cd(2+) adsorption on BS-Mt was mainly attributed to direct electrostatic attraction and the chelate reaction, while the dramatic enhancement of maximum adsorption capacity for BPA was due to the hydrophobic interaction. PMID:26451652

  19. [Thermodynamics adsorption and its influencing factors of chlorpyrifos and triazophos on the bentonite and humus].

    PubMed

    Zhu, Li-Jun; Zhang, Wei; Zhang, Jin-Chi; Zai, De-Xin; Zhao, Rong

    2010-11-01

    The adsorption of chlorpyrifos and triazophos on bentonite and humus was investigated by using the equilibrium oscillometry. The adsorption capacity of chlorpyrifos and triazophos on humus was great higher than bentonite at the same concentration. Equilibrium data of Langmuir, Freundlich isotherms showed significant relationship to the adsorption of chlorpyrifos and triazophos on humus (chlorpyrifos: R2 0.996 4, 0.996 3; triazophos: R2 0.998 9, 0.992 4). Langmuir isotherm was the best for chlorpyrifos and triazophos on bentonite (chlorpyrifos: R2 = 0.995 7, triazophos: R2 = 0.998 9). The pH value, adsorption equilibrium time and temperature were the main factors affecting adsorption of chlorpyrifos and triazophos on bentonite and humus. The adsorption equilibrium time on mixed adsorbent was 12h for chlorpyrifos and 6h for triazophos respectively. The mass ratio of humus and bentonite was 12% and 14% respectively, the adsorption of chlorpyrifos and triazophos was the stronglest and tended to saturation. At different temperatures by calculating the thermodynamic parameters deltaG, deltaH and deltaS, confirmed that the adsorption reaction was a spontaneous exothermic process theoretically. The adsorption was the best when the pH value was 6.0 and the temperature was 15 degrees C.

  20. Effect of tribology processes on adsorption of albumin

    NASA Astrophysics Data System (ADS)

    Yan, Yu; Yang, Hongjuan; Wang, Linghe; Su, Yanjing; Qiao, Lijie

    2016-03-01

    As soon as artificial joint replacements are implanted into patients, the adsorption of proteins can occur. Joint implants operate in a protein-rich and relatively corrosive environment under tribological contact. The contacted area acted as an anodic part and the rest of the surface was more cathodic. Therefore, the adsorption of proteins is different in and outside the wear track. Adsorbed proteins would denature during rubbing and a tribofilm could form. The tribofilm can lubricate the surface and act as a barrier to corrosion damage. However, to observe the adsorption of proteins in situ has always been a challenge. Scanning Kelvin probe force microscope (SKPFM) was used to study the adsorption of albumin on the surface of CoCrMo alloy under simulated tribology movement. Fluorescence microscopy (FM) was employed to reveal the protein molecules in the wear scar. It was found that albumin molecules can decrease the surface potential and accelerate the corrosion process. In the wear track, albumin denatured and changed the surface potential as time progressed.

  1. Galileo Probe Battery System

    NASA Technical Reports Server (NTRS)

    Dagarin, B. P.; Taenaka, R. K.; Stofel, E. J.

    1997-01-01

    The conclusions of the Galileo probe battery system are: the battery performance met mission requirements with margin; extensive ground-based and flight tests of batteries prior to probe separation from orbiter provided good prediction of actual entry performance at Jupiter; and the Li-SO2 battery was an important choice for the probe's main power.

  2. [Adsorption of fluoride ions on a Ca-deficient hydroxyapatite].

    PubMed

    Li, Ling; Zhu, Zhi-Liang; Qiu, Yan-Ling; Zhang, Hua; Zhao, Jian-Fu

    2010-06-01

    A Ca-deficient hydroxyapatite (d-HAp) from the by-product of phosphate wastewater treatment has been used to remove fluoride ions. The effects of pH, coexistent calcium and magnesium ions, and chloride ions on the adsorption efficiency were investigated for the system. The results showed that d-HAp adsorbed F- efficiently within a wide pH range (4-7), and the defluoridation capacity of d-HAp remained 85%. There was no significant effect on removal of fluoride ions with addition of up to 200 times as high a concentration of Ca2+, Mg2+ and Cl-, so it suggested that d-HAp was applicable to high fluoride area. The adsorption kinetics can be described by Pseudo-second-order reaction model and the correlation coefficient R2 was 0.999 0. It was also found that the adsorption of F- on d-HAp followed the Langmuir model. The maximal static adsorption capacity was calculated as 26.11 mg x g(-1). It also suggested that ion exchange was the main mechanism during this adsorptive process. PMID:20698272

  3. Centrifugal Adsorption Cartridge System

    NASA Technical Reports Server (NTRS)

    Gonda, Steve R.; Tsao, Yow-Min D.; Lee, Wenshan

    2004-01-01

    The centrifugal adsorption cartridge system (CACS) is an apparatus that recovers one or more bioproduct(s) from a dilute aqueous solution or suspension flowing from a bioreactor. The CACS can be used both on Earth in unit gravity and in space in low gravity. The CACS can be connected downstream from the bioreactor; alternatively, it can be connected into a flow loop that includes the bioreactor so that the liquid can be recycled. A centrifugal adsorption cartridge in the CACS (see figure) includes two concentric cylinders with a spiral ramp between them. The volume between the inner and outer cylinders, and between the turns of the spiral ramp is packed with an adsorbent material. The inner cylinder is a sieve tube covered with a gas-permeable, hydrophobic membrane. During operation, the liquid effluent from the bioreactor is introduced at one end of the spiral ramp, which then constrains the liquid to flow along the spiral path through the adsorbent material. The spiral ramp also makes the flow more nearly uniform than it would otherwise be, and it minimizes any channeling other than that of the spiral flow itself. The adsorbent material is formulated to selectively capture the bioproduct(s) of interest. The bioproduct(s) can then be stored in bound form in the cartridge or else eluted from the cartridge. The centrifugal effect of the spiral flow is utilized to remove gas bubbles from the liquid. The centrifugal effect forces the bubbles radially inward, toward and through the membrane of the inner cylinder. The gas-permeable, hydrophobic membrane allows the bubbles to enter the inner cylinder while keeping the liquid out. The bubbles that thus enter the cylinder are vented to the atmosphere. The spacing between the ramps determines rate of flow along the spiral, and thereby affects the air-bubble-removal efficiency. The spacing between the ramps also determines the length of the fluid path through the cartridge adsorbent, and thus affects the bioproduct

  4. Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin.

    PubMed

    Rienecker, Shermiyah B; Mostert, A Bernardus; Schenk, Gerhard; Hanson, Graeme R; Meredith, Paul

    2015-12-01

    Melanins are pigmentary macromolecules found in many locations throughout nature including plants and vertebrate animals. It was recently proposed that the predominant brown-black pigment eumelanin is a mixed ionic-electronic conductor which has led to renewed interest in its basic properties as a model bioelectronic material. This exotic hybrid electrical behavior is strongly dependent upon hydration and is closely related to the free radical content of melanin which is believed to be a mixed population of two species: the semiquinone (SQ) and a carbon-centered radical (CCR). The predominant charge carrier is the proton that is released during the formation of the SQ radical and controlled by a comproportionation equilibrium reaction. In this paper we present a combined solid-state electron paramagnetic resonance (EPR), adsorption, and hydrated conductivity study using D2O as a probe. We make specific predictions as to how the heavy isotope effect, in contrast to H2O, should perturb the comproportionation equilibrium and the related outcome as far as the electrical conductivity is concerned. Our EPR results confirm the proposed two-spin mechanism and clearly demonstrate the power of combining macroscopic measurements with observations from mesoscopic probes for the study of bioelectronic materials. PMID:26580677

  5. Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin.

    PubMed

    Rienecker, Shermiyah B; Mostert, A Bernardus; Schenk, Gerhard; Hanson, Graeme R; Meredith, Paul

    2015-12-01

    Melanins are pigmentary macromolecules found in many locations throughout nature including plants and vertebrate animals. It was recently proposed that the predominant brown-black pigment eumelanin is a mixed ionic-electronic conductor which has led to renewed interest in its basic properties as a model bioelectronic material. This exotic hybrid electrical behavior is strongly dependent upon hydration and is closely related to the free radical content of melanin which is believed to be a mixed population of two species: the semiquinone (SQ) and a carbon-centered radical (CCR). The predominant charge carrier is the proton that is released during the formation of the SQ radical and controlled by a comproportionation equilibrium reaction. In this paper we present a combined solid-state electron paramagnetic resonance (EPR), adsorption, and hydrated conductivity study using D2O as a probe. We make specific predictions as to how the heavy isotope effect, in contrast to H2O, should perturb the comproportionation equilibrium and the related outcome as far as the electrical conductivity is concerned. Our EPR results confirm the proposed two-spin mechanism and clearly demonstrate the power of combining macroscopic measurements with observations from mesoscopic probes for the study of bioelectronic materials.

  6. Zip nucleic acids are potent hydrolysis probes for quantitative PCR

    PubMed Central

    Paris, Clément; Moreau, Valérie; Deglane, Gaëlle; Voirin, Emilie; Erbacher, Patrick; Lenne-Samuel, Nathalie

    2010-01-01

    Zip nucleic acids (ZNAs) are oligonucleotides conjugated with cationic spermine units that increase affinity for their target. ZNAs were recently shown to enable specific and sensitive reactions when used as primers for polymerase chain reaction (PCR) and reverse-transcription. Here, we report their use as quantitative PCR hydrolysis probes. Ultraviolet duplex melting data demonstrate that attachment of cationic residues to the 3′ end of an oligonucleotide does not alter its ability to discriminate nucleotides nor the destabilization pattern relative to mismatch location in the oligonucleotide sequence. The stability increase provided by the cationic charges allows the use of short dual-labeled probes that significantly improve single-nucleotide polymorphism genotyping. Longer ZNA probes were shown to display reduced background fluorescence, therefore, generating greater sensitivity and signal level as compared to standard probes. ZNA probes thus provide broad flexibility in assay design and also represent an effective alternative to minor groove binder- and locked nucleic-acid-containing probes. PMID:20071749

  7. [Study on the co-adsorption mechanism of Pb (II) and chlorpyrifos on arid loess in northwestern China].

    PubMed

    Fan, Chun-Hui; Zhang, Ying-Chao; Wang, Jia-Hong

    2013-08-01

    The co-adsorption characteristics of Pb(II) and chlorpyrifos on arid loess were investigated with batch adsorption procedures, and the co-adsorption mechanism was studied with approaches of SEM, FT-IR, XRD and theoretical analysis. The experimental results indicated that the adsorption process of Pb(II) and chlorpyrifos on loess fit better the Langmuir isotherm, the maximum adsorption capacity of q(m) is 12.5 and 0.64 mg x g(-1) for Pb(II) and chlorpyrifos on loess, respectively, and the reaction could be illustrated with pseudo-second order kinetic equation. The SEM micrograph of loess surface varies little after the adsorption process of Pb(II) and chlorpyrifos, and certain wave peaks of FTIR spectra red-shift, disappears or intensity-decrease, with the XRD pattern and theoretical analysis, the adsorption mechanism is described as follows: the adsorption of Pb (II) on arid loess is the chemical-effect of coordination-complexation and Van der Waals force; the physical-adsorption on chlorpyrifos involves the interception function, hydrogen bonds and Van der Waals force, and chemical adsorption effect to some extent. The organic matter in arid loess plays an important role in Pb(II) and chlorpyrifos adsorption.

  8. Short-Cycle Adsorption Refrigerator

    NASA Technical Reports Server (NTRS)

    Chan, C. K.

    1988-01-01

    Modular adsorption/Joule-Thomson-effect refrigerator offers fast regeneration; adsorption/desorption cycle time expected to be 1 minute. Pressurized hydrogen generated by bank of compressor modules during heating phase passes through system of check valves and expands in Joule-Thomson junction as it enters refrigeration chamber. Hydrogen absorbs heat from load before it is sucked out by another bank of compressor modules in cooling phase.

  9. A generalized adsorption-phase transition model to describe adsorption rates in flexible metal organic framework RPM3-Zn.

    PubMed

    Lueking, Angela D; Wang, Cheng-Yu; Sircar, Sarmishtha; Malencia, Christopher; Wang, Hao; Li, Jing

    2016-03-14

    Flexible gate-opening metal organic frameworks (GO-MOFs) expand or contract to minimize the overall free energy of the system upon accommodation of an adsorbate. The thermodynamics of the GO process are well described by a number of models, but the kinetics of the process are relatively unexplored. A flexible GO-MOF, RPM3-Zn, exhibits a significant induction period for opening by N2 and Ar at low temperatures, both above and below the GO pressure. A similar induction period is not observed for H2 or O2 at comparable pressures and temperatures, suggesting the rate of opening is strongly influenced by the gas-surface interaction rather than an external stress. The induction period leads to severe mass transfer limitations for adsorption and over-prediction of the gate-opening pressure. After review of a number of existing adsorption rate models, we find that none adequately describe the experimental rate data and similar timescales for diffusion and opening invalidate prior reaction-diffusion models. Statistically, the rate data are best described by a compressed exponential function. The resulting fitted parameters exceed the expectations for adsorption but fall within those expected for phase transition. By treating adsorption as a phase transition, we generalize the Avrami theory of phase transition kinetics to describe adsorption in both rigid and flexible hosts. The generalized theory is consistent with observed experimental trends relating to induction period, temperature, pressure, and gas-substrate interaction.

  10. Synthesis and adsorption of functionalized polystyrenes

    SciTech Connect

    Iyengar, D.R.

    1992-12-31

    The effect of specifically interacting functional groups located at the chain ends of polystyrene on the absorption rate, adsorbance, graft density and surface excess are discussed from cyclohexane, a theta solvent and toluene. Polystyrenes with hydroxyl and carboxylic acid-end-groups in narrow molecular weight distribution are synthesized by anionic polymerization of styrene followed by suitable termination reactions. Thin layer chromatography (TLC) is developed as an analytical technique to predict trends in the adsorption of the polymers in a range of solvents. In particular the information about the localization of the end-group and therefore different chain architectures at the interface are inferred from this simple technique. Adsorption isotherms are obtained for each of the functionalized polymers of four different molecular weights, the selection of which was based on the TLC results. Kinetics of adsorption and the adsorbance data are determined by liquid counting of tritium labelled polymers. Graft density and surface excess data are calculated from the adsorbance data and other known parameters. It is shown, from these data, that polystyrenes with a carboxylic acid end-group form weakly stretched brushes at the glass-cyclohexane interface and mushrooms at the glass-toluene interface a result consistent with the higher osmotic repulsions towards packing in good solvents. Polystyrenes with function groups at both the chain ends are hypothesized to form a range of structures from those dominated by tails at higher concentrations to those dominated by loops and trains at lower solution concentrations. At higher molecular weights it is shown that functionalized a result consistent with the TLC predictions. Hydroxyl end-group is shown to be an ineffective sticky foot from its adsorbance vis-a-vis polystyrene.

  11. Surfactant adsorption kinetics in microfluidics

    PubMed Central

    Riechers, Birte; Maes, Florine; Akoury, Elias; Semin, Benoît; Gruner, Philipp; Baret, Jean-Christophe

    2016-01-01

    Emulsions are metastable dispersions. Their lifetimes are directly related to the dynamics of surfactants. We design a microfluidic method to measure the kinetics of adsorption of surfactants to the droplet interface, a key process involved in foaming, emulsification, and droplet coarsening. The method is based on the pH decay in the droplet as a direct measurement of the adsorption of a carboxylic acid surfactant to the interface. From the kinetic measurement of the bulk equilibration of the pH, we fully determine the adsorption process of the surfactant. The small droplet size and the convection during the droplet flow ensure that the transport of surfactant through the bulk is not limiting the kinetics of adsorption. To validate our measurements, we show that the adsorption process determines the timescale required to stabilize droplets against coalescence, and we show that the interface should be covered at more than 90% to prevent coalescence. We therefore quantitatively link the process of adsorption/desorption, the stabilization of emulsions, and the kinetics of solute partitioning—here through ion exchange—unraveling the timescales governing these processes. Our method can be further generalized to other surfactants, including nonionic surfactants, by making use of fluorophore–surfactant interactions. PMID:27688765

  12. PDMS compound adsorption in context.

    PubMed

    Li, Nianzhen; Schwartz, Michael; Ionescu-Zanetti, Cristian

    2009-02-01

    Soft lithography of polydimethylsiloxane (PDMS), an elastomeric polymer, has enabled rapid and inexpensive fabrication of microfluidic devices for various biotechnology applications. However, concerns remain about adsorption of compounds on PDMS surfaces because of its porosity and hydrophobicity. Here, the adsorption of 2 small fluorescent dyes of different hydrophobicity (calcein and 5- (and 6-)carboxytetramethylrhodamine (TMR)) on PDMS surface has been systematically characterized, and PDMS adsorption has been compared with 2 traditional substrates: glass and polystyrene. To characterize adsorption in a regimen that is more relevant to microfluidic applications, the adsorption and desorption of the 2 compounds in PDMS microfluidic channels under flow conditions were also studied. Results showed that there was minimal adsorption of the hydrophilic compound calcein on PDMS, whereas the more hydrophobic TMR adsorbed on PDMS up to 4 times of that on glass or polystyrene. Under flow conditions, the desorption profiles and times needed to drop desorbed compound concentrations to negligible levels (desorption time constant, 10-42 s) were characterized. In the worst case scenario, after a 4-min exposure to TMR, 4 min of continuous wash resulted in compound concentrations in the microchannels to drop to values below 2 x 10(- 5) of the initial concentration.

  13. Polymer Adsorption on Graphite and CVD Graphene Surfaces Studied by Surface-Specific Vibrational Spectroscopy.

    PubMed

    Su, Yudan; Han, Hui-Ling; Cai, Qun; Wu, Qiong; Xie, Mingxiu; Chen, Daoyong; Geng, Baisong; Zhang, Yuanbo; Wang, Feng; Shen, Y R; Tian, Chuanshan

    2015-10-14

    Sum-frequency vibrational spectroscopy was employed to probe polymer contaminants on chemical vapor deposition (CVD) graphene and to study alkane and polyethylene (PE) adsorption on graphite. In comparing the spectra from the two surfaces, it was found that the contaminants on CVD graphene must be long-chain alkane or PE-like molecules. PE adsorption from solution on the honeycomb surface results in a self-assembled ordered monolayer with the C-C skeleton plane perpendicular to the surface and an adsorption free energy of ∼42 kJ/mol for PE(H(CH2CH2)nH) with n ≈ 60. Such large adsorption energy is responsible for the easy contamination of CVD graphene by impurity in the polymer during standard transfer processes. Contamination can be minimized with the use of purified polymers free of PE-like impurities.

  14. Dissociative adsorption of O2 on unreconstructed metal (100) surfaces: Pathways, energetics, and sticking kinetics

    NASA Astrophysics Data System (ADS)

    Liu, Da-Jiang; Evans, James W.

    2014-05-01

    An accurate description of oxygen dissociation pathways and kinetics for various local adlayer environments is key for an understanding not just of the coverage dependence of oxygen sticking, but also of reactive steady states in oxidation reactions. Density functional theory analysis for M(100) surfaces with M =Pd, Rh, and Ni, where O prefers the fourfold hollow adsorption site, does not support the traditional Brundle-Behm-Barker picture of dissociative adsorption onto second-nearest-neighbor hollow sites with an additional blocking constraint. Rather adsorption via neighboring vicinal bridge sites dominates, although other pathways can be active. The same conclusion also applies for M =Pt and Ir, where oxygen prefers the bridge adsorption site. Statistical mechanical analysis is performed based on kinetic Monte Carlo simulation of a multisite lattice-gas model consistent with our revised picture of adsorption. This analysis determines the coverage and temperature dependence of sticking for a realistic treatment of the oxygen adlayer structure.

  15. Equilibrium models and kinetic for the adsorption of methylene blue on Co-hectorites.

    PubMed

    Ma, Jun; Jia, Yong-Zhong; Jing, Yan; Sun, Jin-He; Yao, Ying; Wang, Xiao-Hua

    2010-03-15

    The adsorption of methylene blue (MB) onto the surface of cobalt doping hectorite (Co-hectorite) was systematically studied. The physical properties of Co-hectorites were investigated, where characterizations were carried out by X-ray diffraction (XRD) and Electron Diffraction Spectrum (EDS) techniques, and morphology was examined by nitrogen adsorption. The sample with a Co content 5% (m/m) had a higher specific surface area than other Co-hectorites. The pore diameters were distributed between 2.5 and 5.0 nm. The adsorption results revealed that Co-hectorite surfaces possessed effective interactions with MB and bases, and greatest adsorption capacity achieved with Co content 5%, where the best-fit isotherm model was the Langmuir adsorption model. Kinetic studies were fitted to the pseudo-second-order kinetic model. The intraparticle diffusion was not the rate-limiting step for the whole reaction.

  16. The dynamics of adsorption on clean and adsorbate-modified transition metal surfaces

    SciTech Connect

    Madix, R.J.

    1991-06-01

    Research is being carried out on both nondissociative and dissociative adsorption of gases on transition metal surfaces, with emphasis on alkanes. Particular attention is be placed on understanding the effects of adsorbed species on adsorption probabilities and on clarifying the role of energy exchange processes at the surface in both dissociative and nondissociative adsorption. Molecular beam methods are coupled with methods of surface science to gain the greatest control of the variables of the problem, including the incident kinetic energy, vibrational energy and angle of incidence of the incoming molecules. The dynamics of both direct and precursor-influenced dissociative adsorption routes are examined. Surface intermediates formed by activated adsorption are identified by vibrational spectroscopy and temperature programmed reaction. Emphasis is on comparative studies of low molecular weight alkanes in order to understand the origin of the differences in their reactivities on different metals.

  17. Dissociative adsorption of O2 on unreconstructed metal (100) surfaces: Pathways, energetics, and sticking kinetics

    SciTech Connect

    Liu, Da-Jiang; Evans, James W.

    2014-05-06

    An accurate description of oxygen dissociation pathways and kinetics for various local adlayer environments is key for an understanding not just of the coverage dependence of oxygen sticking, but also of reactive steady states in oxidation reactions. Density functional theory analysis for M(100) surfaces with M=Pd, Rh, and Ni, where O prefers the fourfold hollow adsorption site, does not support the traditional Brundle-Behm-Barker picture of dissociative adsorption onto second-nearest-neighbor hollow sites with an additional blocking constraint. Rather adsorption via neighboring vicinal bridge sites dominates, although other pathways can be active. The same conclusion also applies for M=Pt and Ir, where oxygen prefers the bridge adsorption site. Statistical mechanical analysis is performed based on kinetic Monte Carlo simulation of a multisite lattice-gas model consistent with our revised picture of adsorption. This analysis determines the coverage and temperature dependence of sticking for a realistic treatment of the oxygen adlayer structure.

  18. Ultrafast scanning probe microscopy

    DOEpatents

    Weiss, Shimon; Chemla, Daniel S.; Ogletree, D. Frank; Botkin, David

    1995-01-01

    An ultrafast scanning probe microscopy method for achieving subpicosecond-temporal resolution and submicron-spatial resolution of an observation sample. In one embodiment of the present claimed invention, a single short optical pulse is generated and is split into first and second pulses. One of the pulses is delayed using variable time delay means. The first pulse is then directed at an observation sample located proximate to the probe of a scanning probe microscope. The scanning probe microscope produces probe-sample signals indicative of the response of the probe to characteristics of the sample. The second pulse is used to modulate the probe of the scanning probe microscope. The time delay between the first and second pulses is then varied. The probe-sample response signal is recorded at each of the various time delays created between the first and second pulses. The probe-sample response signal is then plotted as a function of time delay to produce a cross-correlation of the probe sample response. In so doing, the present invention provides simultaneous subpicosecond-temporal resolution and submicron-spatial resolution of the sample.

  19. Ultrafast scanning probe microscopy

    DOEpatents

    Weiss, S.; Chemla, D.S.; Ogletree, D.F.; Botkin, D.

    1995-05-16

    An ultrafast scanning probe microscopy method is described for achieving subpicosecond-temporal resolution and submicron-spatial resolution of an observation sample. In one embodiment of the present claimed invention, a single short optical pulse is generated and is split into first and second pulses. One of the pulses is delayed using variable time delay means. The first pulse is then directed at an observation sample located proximate to the probe of a scanning probe microscope. The scanning probe microscope produces probe-sample signals indicative of the response of the probe to characteristics of the sample. The second pulse is used to modulate the probe of the scanning probe microscope. The time delay between the first and second pulses is then varied. The probe-sample response signal is recorded at each of the various time delays created between the first and second pulses. The probe-sample response signal is then plotted as a function of time delay to produce a cross-correlation of the probe sample response. In so doing, the present invention provides simultaneous subpicosecond-temporal resolution and submicron-spatial resolution of the sample. 6 Figs.

  20. Traversing probe system

    DOEpatents

    Mashburn, Douglas N.; Stevens, Richard H.; Woodall, Harold C.

    1977-01-01

    This invention comprises a rotatable annular probe-positioner which carries at least one radially disposed sensing probe, such as a Pitot tube having a right-angled tip. The positioner can be coaxially and rotatably mounted within a compressor casing or the like and then actuated to orient the sensing probe as required to make measurements at selected stations in the annulus between the positioner and compressor casing. The positioner can be actuated to (a) selectively move the probe along its own axis, (b) adjust the yaw angle of the right-angled probe tip, and (c) revolve the probe about the axis common to the positioner and casing. A cam plate engages a cam-follower portion of the probe and normally rotates with the positioner. The positioner includes a first-motor-driven ring gear which effects slidable movement of the probe by rotating the positioner at a time when an external pneumatic cylinder is actuated to engage the cam plate and hold it stationary. When the pneumatic cylinder is not actuated, this ring gear can be driven to revolve the positioner and thus the probe to a desired circumferential location about the above-mentioned common axis. A second motor-driven ring gear included in the positioner can be driven to rotate the probe about its axis, thus adjusting the yaw angle of the probe tip. The positioner can be used in highly corrosive atmosphere, such as gaseous uranium hexafluoride.