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Sample records for adsorbed phase nmr

  1. NMR Study of Phase Transitions in Pure Water and Binary H(2)O/HNO(3) Films Adsorbed on Surface of Pyrogenic Silica.

    PubMed

    Bogdan; Kulmala; Gorbunov; Kruppa

    1996-01-15

    Pyrogenic silica (aerosil) was employed as host within which the phase transitions in the adsorbed pure water and binary H(2)O/HNO(3) films have been studied with NMR spectroscopy. The median freezing temperature and freezing temperature region were shown to be highly sensitive both to the average thickness of the adsorbed films and to the amount of adsorbed nitric acid. The molar concentration of nitric acid in the adsorbed films was found to be very small, on the order of 10(-3)-10(-2) (M/liter). The concentration was found to be greater in the layers adjacent to the surface of silica and sharply decreases with distance from the surface. The difference between the median freezing temperatures for adsorbed pure water and for the binary system was found to be about 9 K for films of equal thickness. This is about 150 times greater than the difference between the freezing temperatures of bulk pure water and a solution with the same concentration of nitric acid. PMID:10479419

  2. The NMR phased array.

    PubMed

    Roemer, P B; Edelstein, W A; Hayes, C E; Souza, S P; Mueller, O M

    1990-11-01

    We describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the "NMR phased array." The NMR phased array offers the signal-to-noise ratio (SNR) and resolution of a small surface coil over fields-of-view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 x 512, 48-cm FOV, and 32-cm FOV) spin-echo images of the thoracic and lumbar spine. Data were acquired from four-element linear spine arrays, the first made of 12-cm square coils and the second made of 8-cm square coils. When compared with images from a single 15 x 30-cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine (approximately 7 cm). PMID:2266841

  3. Decomposition of adsorbed VX on activated carbons studied by {sup 31}P MAS NMR

    SciTech Connect

    Ishay Columbus; Daniel Waysbort; Liora Shmueli; Ido Nir; Doron Kaplan

    2006-06-15

    The fate of the persistent OP nerve agent O-ethyl S-(2-(diisopropylamino)ethyl) methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. Four types of activated carbon were used, including coal-based BPL. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) ((DES){sub 2}). Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed. 17 refs., 6 figs., 3 tabs.

  4. Decomposition of adsorbed VX on activated carbons studied by 31P MAS NMR.

    PubMed

    Columbus, Ishay; Waysbort, Daniel; Shmueli, Liora; Nir, Ido; Kaplan, Doron

    2006-06-15

    The fate of the persistent OP nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) {(DES)2}. Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed. PMID:16830567

  5. NMR surface relaxivity of calcite with adsorbed Mn{sup 2+}

    SciTech Connect

    Kenyon, W.E.; Kolleeny, J.A.

    1995-03-15

    Calcite particles were exposed to Mn{sup 2+} in aqueous solution to allow adsorption. The calcite particles were then packed, and the NMR longitudinal relaxation time T{sub 1} of water saturating the interparticle pores was measured. NMR surface relaxivity was then computed as 1/(T{sub 1}{times}S{sub p}/V{sub p}), where S{sub p}/V{sub p} is the ratio of surface area to pore volume. Adsorbed manganese increases the NMR surface relaxivity to approximately 2.4 {times} 10{sup {minus}3} cm/s, roughly 50 times the surface relaxivity of very pure calcite. Flowing water with 4 {mu}M Mn{sup 2+} through a porous limestone plug decreased its T{sub 1} by a factor of 6. Iron as adsorbate produced relatively small increases in surface relaxivity. These results suggest that manganese dominates the surface relaxivity, of limestone rocks in situ, which is important in the interpretation of NMR borehole logs. Observations suggest that some adsorbed manganese eventually becomes buried by freshly precipitated calcite. In particular, the surface relaxivity increased with initial adsorption, but gradually decreased at long reaction times, even as the aqueous manganese concentration continued to decrease. NMR evidently senses only the manganese in the outermost atomic layer, and thus might prove useful in more detailed studies of adsorption.

  6. Dispersed-phase adsorbents for biotechnology applications

    SciTech Connect

    Scott, C.D.

    1987-01-01

    A new type of adsorbent material has been developed in which very small adsorbent particles are entrapped in a hydrocolloidal gel matrix that is formed into small, monodisperse spherical beads. Examples of applications of this type of material include dispersed, hydrous transition metal oxides that can be used for the retention of biocatalysts, such as enzymes, and certain microorganisms or microbial fragments that can be dispersed into the gel matrix to accumulate and isolate various dissolved metals. 7 refs., 2 figs., 2 tabs.

  7. 13C NMR spectroscopy of methane adsorbed in SAPO-11 molecular sieve

    NASA Astrophysics Data System (ADS)

    Koskela, Tuomas; Ylihautala, Mika; Vaara, Juha; Jokisaari, Jukka

    1996-10-01

    Static 13C and 13C-{ 1H} NMR spectra of carbon-13 enriched methane ( 13CH 4) adsorbed into SAPO-11 molecular sieve were recorded at variable temperatures. Moreover, the corresponding MAS NMR spectra were measured. These experiments reveal a temperature-dependent, anisotropic and asymmetric 13C nuclear shielding tensor. Ab initio model calculations of methane in the field of a positive point charge suggest that the deformation of the shielding tensor may be related to the interaction between the methane molecule and the charge-compensating protons. A comparison with existing Xe data is made.

  8. Tethered or adsorbed supported lipid bilayers in nanotubes characterized by deuterium magic angle spinning NMR spectroscopy.

    PubMed

    Wattraint, Olivier; Warschawski, Dror E; Sarazin, Catherine

    2005-04-12

    2H solid-state NMR experiments were performed under magic angle spinning on lipid bilayers oriented into nanotubes arrays, as a new method to assess the geometrical arrangement of the lipids. Orientational information is obtained from the intensities of the spinning sidebands. The lipid bilayers are formed by fusion of small unilamellar vesicles of DMPC-d54 inside a nanoporous anodic aluminum oxide, either by direct adsorption on the support or by tethering through a streptavidin/biotin linker. The results support that the quality of the lipid bilayers alignment is clearly in favor of the tethering rather than an adsorbed strategy. PMID:15807556

  9. A [sup 13]C NMR study of ethylene adsorbed on reduced and oxygen-covered Ag surfaces

    SciTech Connect

    Plischke, J.K.; Benesi, A.J.; Vannice, M.A. )

    1992-11-01

    [sup 13]C-enriched ethylene was adsorbed on both clean and oxygen-covered Ag particles dispersed on [eta]-Al[sub 2]O[sub 3]. Irreversibly adsorbed C[sub 2]H[sub 4] on O-covered Ag exhibited an upfield shift of [minus]20 ppm relative to gas-phase C[sub 2]H[sub 4], whereas a narrower line and smaller shift of [minus]5 ppm occurred for C[sub 2]H[sub 4] reversibly adsorbed on reduced Ag. In addition to the resonance at 103 ppm for irreversibly adsorbed C[sub 2]H[sub 4], CP/MAS NMR spectra also gave resonances at 179, 170, 164, 159, and 19 ppm for the O-covered Ag sample. The CP/MAS spectrum for Ag acetate powder clearly identified the 179- and 19-ppm peaks as those associated with the carboxyl and methyl carbons of the acetate anion, and the peaks at 159, 164, and 170 ppm were assigned to oxalate, formate, and carbonate (or possibly acetic anhydride) species, respectively, based on previous studies. When heated to 473 K the adsorbed C[sub 2]H[sub 4] disappeared and only acetate and oxalate groups were observed, and continued heating to 573 K removed almost all resonances. No C[sub 2]H[sub 4]O was unambiguously detected, thus with this unpromoted Ag catalyst utilizing a high-surface-area alumina the observable surface species appeared to be those associated with complete combustion, with acetate and oxalate predominating during reaction. These results directly confirm the presence of an Ag acetate species which has been proposed previously to be an intermediate in complete combustion, and the presence of the other three species support earlier tentative assignments based on IR and TPR spectroscopy. Chemical shifts at 61, 28, and 13 ppm were indicative of alkoxy species formed on Bronsted-acid sites on the Al[sub 2]O[sub 3] surface. 58 refs., 8 figs., 4 tabs.

  10. A 13C NMR study of the adsorbed states of CO on Rh dispersed on Al2O3

    NASA Astrophysics Data System (ADS)

    Duncan, T. M.; Yates, J. T.; Vaughan, R. W.

    1980-07-01

    The results of nuclear magnetic resonance (NMR) spectroscopy have been analyzed with respect to previous infrared studies of CO adsorbed on Rh dispersed on Al2O3 to quantify the site distribution and to describe the adsorbed state. The 13C NMR spectra account for all the 13CO adsorbed on a 2.2% Rh on Al2O3 substrate. Although the spectra from the different adsorbed states of CO overlap, the line shapes may be separated into two components based on differences in the 13C spin-lattice relaxation times. These two components have been assigned to the 13CO dicarbonyl formed on single Rh atoms and to 13CO adsorbed on Rh rafts. The component attributed to the CO adsorbed on the raft sites is further separated into linear and bridged CO state contributions based on chemical shift information, yielding a quantitative distribution of the three adsorbed states of CO on Rh. The 13CO distribution is used to estimate the molar integrated intensities of the infrared spectrum of 13CO on Rh at high coverage and to determine the degree of dispersion of Rh on the Al2O3. The 13C NMR line shapes of CO adsorbed on Rh are different from the powder pattern of Rh2Cl2(CO)4. It is suggested that the line shape of the dicarbonyl surface species is narrowed to a Lorentzian curve by reorientation at the site and the line shape of CO on the Rh rafts is modulated by exchange between sites on a single raft. The 13C relaxation time distribution provides further evidence for the existence of isolated Rh atoms on the Al2O3 surface.

  11. Allantoin as a solid phase adsorbent for removing endotoxins.

    PubMed

    Vagenende, Vincent; Ching, Tim-Jang; Chua, Rui-Jing; Gagnon, Pete

    2013-10-01

    In this study we present a simple and robust method for removing endotoxins from protein solutions by using crystals of the small-molecule compound 2,5-dioxo-4-imidazolidinyl urea (allantoin) as a solid phase adsorbent. Allantoin crystalline powder is added to a protein solution at supersaturated concentrations, endotoxins bind and undissolved allantoin crystals with bound endotoxins are removed by filtration or centrifugation. This method removes an average of 99.98% endotoxin for 20 test proteins. The average protein recovery is ∼80%. Endotoxin binding is largely independent of pH, conductivity, reducing agent and various organic solvents. This is consistent with a hydrogen-bond based binding mechanism. Allantoin does not affect protein activity and stability, and the use of allantoin as a solid phase adsorbent provides better endotoxin removal than anion exchange, polymixin affinity and biological affinity methods for endotoxin clearance. PMID:24001944

  12. Phase Diagram for 3He Films on Boron Nitride: NMR Studies

    NASA Astrophysics Data System (ADS)

    Tang, Yibing; Sullivan, Neil

    2014-03-01

    Recent studies of the thermodynamic properties of 3He films on graphite have revealed the existence of a previously undetected self-bound liquid phase at low density coverages. We report the results of NMR relaxation time studies for 3He adsorbed on hexagonal boron nitride designed to explore the dynamics of the adsorbed 3He atoms in order to identify the phase boundaries as a function of temperature. A steep thermally activated temperature dependence is observed at high temperatures (T > 2 . 6) K, followed by a linear dependence for 0 . 77 < T < 2 . 6 K. The linear dependence is consistent with that expected for thermal diffusion in the self-bound liquid state. The research was supported in part by a grant from the National Science Foundation, DMR-1303599.

  13. Electrospun polystyrene nanofibers as a novel adsorbent to transfer an organic phase from an aqueous phase.

    PubMed

    Liu, Feilong; Song, Dandan; Huang, Xueying; Xu, Hui

    2016-04-01

    The aim of this work is to develop a simple phase-transfer method for dispersive liquid-liquid microextraction. For this purpose, a polystyrene nanofiber was prepared by a facile electrospinning strategy and used for the first time as an adsorbent to transfer the organic phase in dispersive liquid-liquid microextraction procedure. The fiber was characterized and its chemical stability and excellent hydrophobicity enable it to selectively adsorb the organic solvent in an aqueous sample. High porosity and specific surface area provide a large adsorption capacity. Under the optimal conditions, the developed dispersive liquid-liquid microextraction with high-performance liquid chromatography method was successfully applied to the analysis of aldehydes in environmental water samples. The merits of this approach are that it is easy-to-operate, low-cost, time-saving, and has satisfactory sensitivity. It provides an alternative way for fast and convenient phase transfer of the hydrophobic organic solvent from the aqueous phase. PMID:26841974

  14. High resolution 1H NMR of a lipid cubic phase using a solution NMR probe

    NASA Astrophysics Data System (ADS)

    Boyle-Roden, E.; Hoefer, N.; Dey, K. K.; Grandinetti, P. J.; Caffrey, M.

    2007-11-01

    The cubic mesophase formed by monoacylglycerols and water is an important medium for the in meso crystallogenesis of membrane proteins. To investigate molecular level lipid and additive interactions within the cubic phase, a method was developed for improving the resolution of 1H NMR spectra when using a conventional solution state NMR probe. Using this approach we obtained well-resolved J-coupling multiplets in the one-dimensional NMR spectrum of the cubic-Ia3d phase prepared with hydrated monoolein. A high resolution t-ROESY two-dimensional 1H NMR spectrum of the cubic-Ia3d phase is also reported. Using this new methodology, we have investigated the interaction of two additive molecules, L-tryptophan and ruthenium-tris(2,2-bipyridyl) dichloride (rubipy), with the cubic mesophase. Based on the measured chemical shift differences when changing from an aqueous solution to the cubic phase, we conclude that L-tryptophan experiences specific interactions with the bilayer interface, whereas rubipy remains in the aqueous channels and does not associate with the lipid bilayer.

  15. NMR study of Li adsorbed on the Si (111) - (3×1) -Li surface

    NASA Astrophysics Data System (ADS)

    Bromberger, C.; Jänsch, H. J.; Kühlert, O.; Schillinger, R.; Fick, D.

    2004-06-01

    Li adsorption on the (3×1) -Li reconstructed Si(111) surface has been studied by β -nuclear magnetic resonance experiments (measurements of T1 times). A rich variety of temperature, coverage, and magnetic field dependencies were observed, which reflect a metal-semiconductor-metal transition while adsorbing Li with increasing coverage on a (7×7) -reconstructed Si(111) surface in such a way that the (3×1) reconstruction is driven. With the aid of a formulated concept of Li donors localized on a semiconducting surface the temperature dependence of relaxation rates for Li adsorbed at extremely low coverages (up to 0.01 ML ) could be understood consistently. The donor energy of adsorbed Li on the (3×1) surface has been determined to be ED ≈100 meV . This success proves additionally that the theoretical results of a completely ionized Li chain in the (3×1) reconstruction are correct. The observed semiconductor-metal transition for adsorption of 0.14 ML additional Li on the already (3×1) -reconstructed surface points to the existence of an empty state near the Fermi energy (probably the so-called S-1 state). The diffusion energy of Li on the Si (111) - (3×1) surface could be estimated to be Ediff ≈410 meV .

  16. Characterization of Adsorbed Molecular Water on the Surface of a Stretched Polytetrafluoroethylene Tape Analyzed by (1)H NMR.

    PubMed

    Wakai, Chihiro; Shimoaka, Takafumi; Hasegawa, Takeshi

    2016-03-10

    A single molecule often exhibits a largely different material character from a bulk matter. Although a perfluoroalkyl (Rf) compound is a representative one, many interests have mostly been devoted to the bulk character only thus far, leaving the single molecular character unclear. Recently, a new theoretical framework, stratified dipole-arrays (SDA) theory, has appeared for comprehensive understanding of Rf compounds in terms of both single and bulk systems. On this theory, a mechanically stretched polytetrafluoroethylene (PTFE) is expected to exhibit a single-molecular character having dipole-driven properties, which should attract molecular water. In the present study, a stretched PTFE tape is revealed to attract molecular water (not water droplet) in fact, and the adsorbed water molecules are highly restricted in motion by the dipole-dipole interaction studied by using (1)H NMR, which agrees with the prediction by the SDA theory. PMID:26848611

  17. NMR Studies of the Li-Mg-N-H Phases.

    NASA Astrophysics Data System (ADS)

    Bowman, Robert; Reiter, J. W.; Kulleck, J. G.; Hwang, S.-J.; Luo, Weifang

    2007-03-01

    Solid state NMR including magic-angle-spinning (MAS) and cross-polarization (CP) MAS experiments have been used to characterize various amide and imide phases containing Li and/or Mg. MAS-NMR spectra for the ^1H, ^6Li, ^7Li, and ^15N nuclei have been obtained to improve understanding on formation, processing, and degradation behavior. Only limited information could be obtained from the proton and ^7Li MAS-NMR spectra to due large dipolar interactions and small chemical shifts. However, more success was obtained from the ^6Li and ^15N nuclei although their very long spin-lattice relaxation times did impact signal acquisition times. For example, three distinct ^6Li peaks were resolved from LiNH2 phases that were clearly separated from the LiH secondary phase in these samples. While the ^15N spectra for LiNH2 phase in isotopically enriched samples exhibited only a single peak at least three distinct ^15N peaks were observed from the similarly enriched Mg amide samples. These differences will be related to crystal structures. The NMR spectra also revealed very little motion in these hydrides upon to nearly 500 K.

  18. Solid State NMR Studies of the Aluminum Hydride Phases

    NASA Technical Reports Server (NTRS)

    Hwang, Son-Jong; Bowman, R. C., Jr.; Graetz, Jason; Reilly, J. J.

    2006-01-01

    Several solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the (beta)- and (gamma)- phases as well as the most stable (alpha)-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the (beta)-AlH3 and (gamma)-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the (alpha)-phase materials do not exhibit these changes.

  19. NMR Studies of the Dynamics of HD Adsorbed on MCM-41

    NASA Astrophysics Data System (ADS)

    Huan, Chao; Hamida, Jaha; Sullivan, Neil

    We report the results of measurements of the nuclear spin-spin and spin-lattice relaxation times of a monolayer of HD molecules adsorbed on MCM-41 for temperatures 1 . 5 < T < 20 K. Two distinct characteristic relaxation times are observed. A slow diffusion process for 5 < T < 8 . 8 K and a faster rate with a distinctly different activation energy for 8 . 9 < T < 12 K. The behavior is fluid-like above 12 K. We discuss the results in terms of an expected cluster formation at low temperatures followed by the diffusion of single molecules at high temperatures. Work suported by the National Science Foundation - DMR-1303599 and DMR-1157490 (National High Magnetic Field Laboratory).

  20. NMR study of ferroelastic phase transition of tetramethylammonium tetrabromocobaltate

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Kim, Sun Ha

    2016-09-01

    Static and magic angle spinning (MAS) nuclear magnetic resonance (NMR) experiments were carried out on 1H, 13C, and 14N nuclei in order to understand the structural changes of the N(CH3)4 groups in [N(CH3)4]2CoBr4 near the ferroelastic phase transition temperature TC. The two chemically inequivalent N(CH3)4 groups were distinguished using 13C cross-polarization/(CP)MAS and 14N static NMR. The changes in chemical shifts, line intensities, and the spin-lattice relaxation time near TC can be correlated with the changing structural geometry, which underlies the phase transition. The 14N NMR spectra indicated a crystal symmetry change at TC, which is related to the ferroelastic domain with different orientations of the N(CH3)4 groups. The ferroelastic domain walls were confirmed by optical polarizing microscopy, and the wall orientations were described by the Sapriel theory. The transition to the ferroelastic phase was found to be related to the orientational ordering of the N(CH3)4 groups.

  1. Characterization of a Mixture of CO2 Adsorption Products in Hyperbranched Aminosilica Adsorbents by (13)C Solid-State NMR.

    PubMed

    Moore, Jeremy K; Sakwa-Novak, Miles A; Chaikittisilp, Watcharop; Mehta, Anil K; Conradi, Mark S; Jones, Christopher W; Hayes, Sophia E

    2015-11-17

    Hyperbranched amine polymers (HAS) grown from the mesoporous silica SBA-15 (hereafter "SBA-15-HAS") exhibit large capacities for CO2 adsorption. We have used static in situ and magic-angle spinning (MAS) ex situ (13)C nuclear magnetic resonance (NMR) to examine the adsorption of CO2 by SBA-15-HAS. (13)C NMR distinguishes the signal of gas-phase (13)CO2 from that of the chemisorbed species. HAS polymers possess primary, secondary, and tertiary amines, leading to multiple chemisorption reaction outcomes, including carbamate (RnNCOO(-)), carbamic acid (RnNCOOH), and bicarbonate (HCO3(-)) moieties. Carbamates and bicarbonate fall within a small (13)C chemical shift range (162-166 ppm), and a mixture was observed including carbamic acid and carbamate, the former disappearing upon evacuation of the sample. By examining the (13)C-(14)N dipolar coupling through low-field (B0 = 3 T) (13)C{(1)H} cross-polarization MAS NMR, carbamate is confirmed through splitting of the (13)C resonance. A third species that is either bicarbonate or a second carbamate is evident from bimodal T2 decay times of the ∼163 ppm peak, indicating the presence of two species comprising that single resonance. The mixture of products suggests that (1) the presence of amines and water leads to bicarbonate being present and/or (2) the multiple types of amine sites in HAS permit formation of chemically distinct carbamates. PMID:26477882

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

    USGS Publications Warehouse

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

    1996-01-01

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

  3. Two Phase Flow Measurements by Nuclear Magnetic Resonance (NMR)

    SciTech Connect

    Altobelli, Stephen A; Fukushima, Eiichi

    2006-08-14

    In concentrated suspensions, there is a tendency for the solid phase to migrate from regions of high shear rate to regions of low shear (Leighton & Acrivos, 1987). In the early years that our effort was funded by the DOE Division of Basic Energy Science, quantitative measurement of this process in neutrally buoyant suspensions was a major focus (Abbott, et al., 1991; Altobelli, et al., 1991). Much of this work was used to improve multi-phase numerical models at Sandia National Laboratories. Later, our collaborators at Sandia and the University of New Mexico incorporated body forces into their numerical models of suspension flow (Rao, Mondy, Sun, et al., 2002). We developed experiments that allow us to study flows driven by buoyancy, to characterize these flows in well-known and useful engineering terms (Altobelli and Mondy, 2002) and to begin to explore the less well-understood area of flows with multiple solid phases (Beyea, Altobelli, et al., 2003). We also studied flows that combine the effects of shear and buoyancy, and flows of suspensions made from non-Newtonian liquids (Rao, Mondy, Baer, et al, 2002). We were able to demonstrate the usefulness of proton NMR imaging of liquid phase concentration and velocity and produced quantitative data not obtainable by other methods. Fluids flowing through porous solids are important in geophysics and in chemical processing. NMR techniques have been widely used to study liquid flow in porous media. We pioneered the extension of these studies to gas flows (Koptyug, et al, 2000, 2000, 2001, 2002). This extension allows us to investigate a wider range of Peclet numbers, and to gather data on problems of interest in catalysis. We devised two kinds of NMR experiments for three-phase systems. Both experiments employ two NMR visible phases and one phase that gives no NMR signal. The earlier method depends on the two visible phases differing in a NMR relaxation property. The second method (Beyea, Altobelli, et al., 2003) uses two

  4. Comparison of Gas and Adsorbed Phase X-ray Photoemission Spectra of Oxidized Organics on Ice

    NASA Astrophysics Data System (ADS)

    Newberg, J. T.; Bluhm, H.

    2011-12-01

    Most uptake studies of small chain organics on ice surfaces at near ambient conditions have been performed using flow tube and other methods which monitor the disappearance of the gas phase. We will present results using synchrotron based, ambient pressure X-ray photoemission spectroscopy which allows for the probing of the ice surface directly at near ambient conditions. C 1s XPS and C K-edge NEXAFS gas phase and adsorbed phase spectra will be compared for 2-propanol, acetone, and 1-propanal on ice at -45 C. Uptake experiments give rise to first order Langmuirian isotherms. Acetone and 2-propanol show little difference in the photoemission spectra between the gas phase and adsorbed phase, suggesting that adsorption occurs molecularly. However, adsorption of 1-propanal shows evidence of chemical transformation (oxidation) at the interface of ice. Further studies are underway to better understand this adsorption behavior.

  5. Extraction of quadrature phase information from multiple pulse NMR signals

    NASA Technical Reports Server (NTRS)

    Rhim, W.-K.; Burum, D. P.; Vaughan, R. W.

    1976-01-01

    A multiple pulse sequence (8-pulse sequence) used for high-resolution solid state NMR is analyzed with regard to the information available from each of the four wide sampling windows. It is demonstrated that full quadrature phase information can be obtained using only a single phase detector and that, for the commonly encountered situation where the spectral width is much less than the folding frequency, the signals from the various windows can be combined easily using standard complex Fourier transform software. An improvement in the signal-to-noise ratio equal to the square root of 3 is obtained over either standard single or quadrature phase detection schemes. Procedures for correcting spectral distortions are presented.

  6. Multinuclear NMR Imaging of Fluid Phases in Berea Sandstone

    NASA Astrophysics Data System (ADS)

    Sarkar, S. N.; Dechter, J. J.; Komoroski, R. A.

    Multinuclear NMR of 7Li, 19F, and 1H has been investigated as a method for discriminating multiple fluid phases in porous rock. Good 7Li NMR images from LiCl brine in saturated Berea sandstone were obtained within a few hours at 1 × 1 × 5 mm 3 resolution using a low-TE, 3D volume imaging sequence. At 4.7 T, the 7Li T1 was 750 ms, and T2 was 10 ms. High-quality 19F and 1H images of a model fluorinated injectant (trifluorotoluene) in Berea were obtained at 0.4 × 0.4 × 3 mm 3 resolution in a few hours. Fluorine-19 imaging was found to be easier than 1H imaging due to the narrower 19F resonance and comparable T1 and T2 in Berea sandstone. Lithium-7 and 19F imaging offer alternatives for discriminating aqueous and organic phases unambiguously in flooded oil cores, especially where 1H signals for the two phases are unresolved.

  7. Interlocking order parameter fluctuations in structural transitions between adsorbed polymer phases.

    PubMed

    Martins, Paulo H L; Bachmann, Michael

    2016-01-21

    By means of contact-density chain-growth simulations of a simple coarse-grained lattice model for a polymer grafted at a solid homogeneous substrate, we investigate the complementary behavior of the numbers of surface-monomer and monomer-monomer contacts under various solvent and thermal conditions. This pair of contact numbers represents an appropriate set of order parameters that enables the distinct discrimination of significantly different compact phases of polymer adsorption. Depending on the transition scenario, these order parameters can interlock in perfect cooperation. The analysis helps understand the transitions from compact filmlike adsorbed polymer conformations into layered morphologies and dissolved adsorbed structures, respectively, in more detail. PMID:26690091

  8. Ordered phases of ethylene adsorbed on charged fullerenes and their aggregates☆

    PubMed Central

    Zöttl, Samuel; Kaiser, Alexander; Daxner, Matthias; Goulart, Marcelo; Mauracher, Andreas; Probst, Michael; Hagelberg, Frank; Denifl, Stephan; Scheier, Paul; Echt, Olof

    2014-01-01

    In spite of extensive investigations of ethylene adsorbed on graphite, bundles of nanotubes, and crystals of fullerenes, little is known about the existence of commensurate phases; they have escaped detection in almost all previous work. Here we present a combined experimental and theoretical study of ethylene adsorbed on free C60 and its aggregates. The ion yield of (C60)m(C2H4)n+ measured by mass spectrometry reveals a propensity to form a structurally ordered phase on monomers, dimers and trimers of C60 in which all sterically accessible hollow sites over carbon rings are occupied. Presumably the enhancement of the corrugation by the curvature of the fullerene surface favors this phase which is akin to a hypothetical 1 × 1 phase on graphite. Experimental data also reveal the number of molecules in groove sites of the C60 dimer through tetramer. The identity of the sites, adsorption energies and orientations of the adsorbed molecules are determined by molecular dynamics calculations based on quantum chemical potentials, as well as density functional theory. The decrease in orientational order with increasing temperature is also explored in the simulations whereas in the experiment it is impossible to vary the temperature. PMID:25843960

  9. NMR Studies on the Aqueous Phase Photochemical Degradation of TNT

    SciTech Connect

    Thorn, Kevin A.; Cox, Larry G.

    2008-04-06

    Aqueous phase photochemical degradation of 2,4,6-trinitrotoluene (TNT) is an important pathway in several environments, including washout lagoon soils, impact craters from partially detonated munitions that fill with rain or groundwater, and shallow marine environments containing unexploded munitions that have corroded. Knowledge of the degradation products is necessary for compliance issues on military firing ranges and formerly used defense sites. Previous laboratory studies have indicated that UV irradiation of aqueous TNT solutions results in a multicomponent product mixture, including polymerization compounds, that has been only partially resolved by mass spectrometric analyses. This study illustrates how a combination of solid and liquid state 1H, 13C, and 15N NMR spectroscopy, including two dimensional analyses, provides complementary information on the total product mixture from aqueous photolysis of TNT, and the effect of reaction conditions. Among the degradation products detected were amine, amide, azoxy, azo, and carboxylic acid compounds.

  10. Phase transition and winding properties of a flexible polymer adsorbed to a rigid perioidic copolymer.

    PubMed

    Liu, Lei; Schubert, David; Chu, Min; Heermann, Dieter W

    2015-03-01

    Motivated by the noncovalent binding of polypeptides to DNA, the adsorption of a flexible polymer to a rigid periodic copolymer is studied in two dimensions and three dimensions. The fraction of adsorbed monomers, the specific heat, and the Binder cumulant are analyzed and compared with analytical results for an ideal chain. As the interaction strength ε increases, a second-order phase transition occurs from a nonadsorbed state to an adsorbed state, in two dimensions, and a higher-order transition occurs in three dimensions. The transition point is estimated as ε0∼2.2 for d=2 and ε0∼2.1 for d=3, where ε is given in units of kBT. The dependence of the number of adsorbed monomers Nads on the chain length L of the flexible polymer shows a power law scaling relation Nads∼Lϕ, with ϕ∼0.46,0.42 for d=2,3, respectively. We also find an optimal ε∼2.8 for the winding of the flexible polymer around the rigid one in three dimensions. Compared to the adsorbed monomers, the successive nonadsorbed monomers contribute more to the winding. When the interaction is strong, ε>3.5, the winding value or the number of winding turns of the flexible polymer becomes linearly dependent on the chain length. PMID:25871135

  11. Ionic liquid coated carbon nanospheres as a new adsorbent for fast solid phase extraction of trace copper and lead from sea water, wastewater, street dust and spice samples.

    PubMed

    Tokalıoğlu, Şerife; Yavuz, Emre; Şahan, Halil; Çolak, Süleyman Gökhan; Ocakoğlu, Kasım; Kaçer, Mehmet; Patat, Şaban

    2016-10-01

    In this study a new adsorbent, ionic liquid (1,8-naphthalene monoimide bearing imidazolium salt) coated carbon nanospheres, was synthesized for the first time and it was used for the solid phase extraction of copper and lead from various samples prior to determination by flame atomic absorption spectrometry. The ionic liquid, carbon nanospheres and ionic liquid coated carbon nanospheres were characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, (1)H NMR and (13)C NMR, Brunauer, Emmett and Teller surface area and zeta potential measurements. Various parameters for method optimization such as pH, adsorption and elution contact times, eluent volume, type and concentration, centrifuge time, sample volume, adsorption capacity and possible interfering ion effects were tested. The optimum pH was 6. The preconcentration factor, detection limits, adsorption capacity and precision (as RSD%) of the method were found to be 300-fold, 0.30µgL(-1), 60mgg(-1) and 1.1% for copper and 300-fold, 1.76µgL(-1); 50.3mgg(-1) and 2.2%, for lead, respectively. The effect of contact time results showed that copper and lead were adsorbed and desorbed from the adsorbent without vortexing. The equilibrium between analyte and adsorbent is reached very quickly. The method was rather selective for matrix ions in high concentrations. The accuracy of the developed method was confirmed by analyzing certified reference materials (LGC6016 Estuarine Water, Reference Material 8704 Buffalo River Sediment, and BCR-482 Lichen) and by spiking sea water, wastewater, street dust and spice samples. PMID:27474302

  12. Aging assessment of nuclear air-treatment system HEPA filters and adsorbers. Volume 1, Phase 1

    SciTech Connect

    Winegardner, W.K.

    1993-08-01

    A Phase I aging assessment of high-efficiency particulate air (HEPA) filters and activated carbon gas adsorption units (adsorbers) was performed by the Pacific Northwest Laboratory (PNL) as part of the US Nuclear Regulatory Commission`s (NRC) Nuclear Plant Aging Research (NPAR) Program. Information concerning design features; failure experience; aging mechanisms, effects, and stressors; and surveillance and monitoring methods for these key air-treatment system components was compiled. Over 1100 failures, or 12 percent of the filter installations, were reported as part of a Department of Energy (DOE) survey. Investigators from other national laboratories have suggested that aging effects could have contributed to over 80 percent of these failures. Tensile strength tests on aged filter media specimens indicated a decrease in strength. Filter aging mechanisms range from those associated with particle loading to reactions that alter properties of sealants and gaskets. Low radioiodine decontamination factors associated with the Three Mile Island (TMI) accident were attributed to the premature aging of the carbon in the adsorbers. Mechanisms that can lead to impaired adsorber performance include oxidation as well as the loss of potentially available active sites as a result of the adsorption of pollutants. Stressors include heat, moisture, radiation, and airborne particles and contaminants.

  13. Phase-field modeling of epitaxial growth in stochastic systems with interacting adsorbate

    NASA Astrophysics Data System (ADS)

    Kharchenko, Dmitrii O.; Kharchenko, Vasyl O.; Lysenko, Irina O.

    2011-04-01

    We study the epitaxial growth of pyramidal patterns in stochastic systems with interacting adsorbate within the framework of the phase-field approach based on the Burton-Cabrera-Frank model. Considering the statistical criteria of pattern formation, it is shown that the system dynamics is governed by the interaction strength of adatoms and the noise intensity of the total flux fluctuations. We have shown that the noise action can crucially change the processes of pyramidal pattern formation. The scaling behavior of the height-height correlation function is discussed.

  14. Low-density phases of 3He monolayers adsorbed on graphite

    NASA Astrophysics Data System (ADS)

    Ruggeri, Michele; Vitali, Ettore; Galli, Davide Emilio; Boninsegni, Massimo; Moroni, Saverio

    2016-03-01

    Quantum Monte Carlo simulations at zero temperature of a 3He monolayer adsorbed on graphite, either clean or preplated with 4He, unexpectedly point to a gas-liquid phase transition at a very low areal density of the order of 0.01 Å-2 . This result stems from an essentially unbiased calculation of the ground-state energy for an infinite, defect-free substrate, which interacts with He atoms via a realistic potential, whereas the interaction between two He atoms includes two- and three-body terms. The sensitivity of the gas-liquid coexistence region on the model Hamiltonian employed is discussed.

  15. Report for in-situ 7Li NMR experiment in PNNL Phase -1

    SciTech Connect

    Hu, Jian Zhi

    2014-08-19

    To understand the detailed local structural evolution, an in-situ 7Li NMR study was performed. An operando identification of the lithium germanide phases under various cycling regimens permitted understanding of the kinetics of phase transition between different structural phases, including the amorphous phases, and how these correlated with capacity retention. Combining data from TEM and in-situ 7Li NMR, we discovered that the phase inter-conversion during cycling was mediated by co-existing amorphous and crystalline phases, and that the high capacity observed was correlated with an over-lithiated lithium germanide phase.

  16. 129Xe NMR of xenon adsorbed on the molecular sieves AlPO 4-5, SAPO-5, MAPO-5, and SAPO-37

    NASA Astrophysics Data System (ADS)

    Chen, Q. J.; Springuel-Huet, M. A.; Fraissard, J.

    1989-06-01

    The solids NaY, SAPO-37, ALPO 4-5, SAPO-5 and MAPO-5 have been studied at 26°C by 129 NMR with adsorbed xenon used as a probe. The equal values of the chemical shifts of NaY and SAPO-37 show that this technique can be used both on zeolites and AlPO 4 or their derivatives. The chemical shifts of AlPO 4-5, SAPO-5 and MAPO-5 are identical at 26°C. The difference with respect to the value determined from the structure cannot therefore be explained by the difference in chemical composition leading to specific Xe-solid interactions.

  17. Measurement of the lateral diffusion of dipalmitoylphosphatidylcholine adsorbed on silica beads in the absence and presence of melittin: a 31P two-dimensional exchange solid-state NMR study.

    PubMed Central

    Picard, F; Paquet, M J; Dufourc, E J; Auger, M

    1998-01-01

    31P two-dimensional exchange solid-state NMR spectroscopy was used to measure the lateral diffusion, D(L), in the fluid phase of dipalmitoylphosphatidylcholine (DPPC) in the presence and absence of melittin. The use of a spherical solid support with a radius of 320 +/- 20 nm, on which lipids and peptides are adsorbed together, and a novel way of analyzing the two-dimensional exchange patterns afforded a narrow distribution of D(L) centered at a value of (8.8 +/- 0.5) x 10(-8) cm2/s for the pure lipid system and a large distribution of D(L) spanning 1 x 10(-8) to 10 x 10(-8) cm2/s for the lipids in the presence of melittin. In addition, the determination of D(L) for nonsupported DPPC multilamellar vesicles (MLVs) suggests that the support does not slow down the lipid diffusion and that the radii of the bilayers vary from 300 to 800 nm. Finally, the DPPC-melittin complex is stabilized at the surface of the silica beads in the gel phase, opening the way to further study of the interaction between melittin and DPPC. PMID:9533697

  18. A method for the calculation of the adsorbed phase volume and pseudo-saturation pressure from adsorption isotherm data on activated carbon.

    PubMed

    Srinivasan, Kandadai; Saha, Bidyut Baran; Ng, Kim Choon; Dutta, Pradip; Prasad, Madhu

    2011-07-21

    We propose a new method for evaluating the adsorbed phase volume during physisorption of several gases on activated carbon specimens. We treat the adsorbed phase as another equilibrium phase which satisfies the Gibbs equation and hence assume that the law of rectilinear diameters is applicable. Since invariably the bulk gas phase densities are known along measured isotherms, the constants of the adsorbed phase volume can be regressed from the experimental data. We take the Dubinin-Astakhov isotherm as the model for verifying our hypothesis since it is one of the few equations that accounts for adsorbed phase volume changes. In addition, the pseudo-saturation pressure in the supercritical region is calculated by letting the index of the temperature term in Dubinin's equation to be temperature dependent. Based on over 50 combinations of activated carbons and adsorbates (nitrogen, oxygen, argon, carbon dioxide, hydrocarbons and halocarbon refrigerants) it is observed that the proposed changes fit experimental data quite well. PMID:21670804

  19. Study of the Aharonov-Anandan quantum phase by NMR interferometry

    SciTech Connect

    Suter, D.; Mueller, K.T.; Pines, A.

    1988-03-28

    Aharonov and Anandan have recently reformulated and generalized Berry's phase by showing that a quantum system which evolves through a circuit C in projective Hilbert space acquires a geometrical phase ..beta..(C) related to the topology of the space and the geometry of the circuit. We present NMR interferometry experiments in a three-level system which demonstrate the Aharonov-Anandan phase and its topological invariance for different circuits.

  20. Adsorbent phases with nanomaterials for in-tube solid-phase microextraction coupled on-line to liquid nanochromatography.

    PubMed

    González-Fuenzalida, R A; López-García, E; Moliner-Martínez, Y; Campíns-Falcó, P

    2016-02-01

    Following the present trends in miniaturization, a methodology that combines on-line In-Tube Solid-Phase Microextraction (IT-SPME) with Liquid Nanochromatography (nano-LC) and UV-vis diode array detection (DAD) was developed. This coupling was achieved by using two interconnected valves (i.e. conventional and micro-automatic valves) in the system of injection. As for IT-SPME, different materials, containing in some cases nanostructures or nanoparticles and in other cases polymeric adsorbent phases immobilized on capillary columns, were tested in order to improve extraction efficiencies of organic compounds; diclofenac was selected as the target analyte. Additionally, the transfer time of the sample between the two injection valves, as well as the lengths and the internal diameters of the capillary columns, was optimized. Under the selected conditions, the resulting IT-SPME-nano-LC-DAD method showed great potential to become a powerful analytical tool as it was successfully applied to the determination of diclofenac in pharmaceutical and water samples. For comparison purposes, IT-SPME coupled to Capillary Liquid Chromatography (Cap-LC) was used. The extraction yield of diclofenac reached near 80%, a high value for techniques that involve IT-SPME. Good accuracy (recoveries near 100%) and precision (4% RSD) were obtained. PMID:26795277

  1. Comprehensive multiphase NMR spectroscopy: basic experimental approaches to differentiate phases in heterogeneous samples.

    PubMed

    Courtier-Murias, Denis; Farooq, Hashim; Masoom, Hussain; Botana, Adolfo; Soong, Ronald; Longstaffe, James G; Simpson, Myrna J; Maas, Werner E; Fey, Michael; Andrew, Brian; Struppe, Jochem; Hutchins, Howard; Krishnamurthy, Sridevi; Kumar, Rajeev; Monette, Martine; Stronks, Henry J; Hume, Alan; Simpson, André J

    2012-04-01

    Heterogeneous samples, such as soils, sediments, plants, tissues, foods and organisms, often contain liquid-, gel- and solid-like phases and it is the synergism between these phases that determine their environmental and biological properties. Studying each phase separately can perturb the sample, removing important structural information such as chemical interactions at the gel-solid interface, kinetics across boundaries and conformation in the natural state. In order to overcome these limitations a Comprehensive Multiphase-Nuclear Magnetic Resonance (CMP-NMR) probe has been developed, and is introduced here, that permits all bonds in all phases to be studied and differentiated in whole unaltered natural samples. The CMP-NMR probe is built with high power circuitry, Magic Angle Spinning (MAS), is fitted with a lock channel, pulse field gradients, and is fully susceptibility matched. Consequently, this novel NMR probe has to cover all HR-MAS aspects without compromising power handling to permit the full range of solution-, gel- and solid-state experiments available today. Using this technology, both structures and interactions can be studied independently in each phase as well as transfer/interactions between phases within a heterogeneous sample. This paper outlines some basic experimental approaches using a model heterogeneous multiphase sample containing liquid-, gel- and solid-like components in water, yielding separate (1)H and (13)C spectra for the different phases. In addition, (19)F performance is also addressed. To illustrate the capability of (19)F NMR soil samples, containing two different contaminants, are used, demonstrating a preliminary, but real-world application of this technology. This novel NMR approach possesses a great potential for the in situ study of natural samples in their native state. PMID:22425441

  2. Comprehensive multiphase NMR spectroscopy: Basic experimental approaches to differentiate phases in heterogeneous samples

    NASA Astrophysics Data System (ADS)

    Courtier-Murias, Denis; Farooq, Hashim; Masoom, Hussain; Botana, Adolfo; Soong, Ronald; Longstaffe, James G.; Simpson, Myrna J.; Maas, Werner E.; Fey, Michael; Andrew, Brian; Struppe, Jochem; Hutchins, Howard; Krishnamurthy, Sridevi; Kumar, Rajeev; Monette, Martine; Stronks, Henry J.; Hume, Alan; Simpson, André J.

    2012-04-01

    Heterogeneous samples, such as soils, sediments, plants, tissues, foods and organisms, often contain liquid-, gel- and solid-like phases and it is the synergism between these phases that determine their environmental and biological properties. Studying each phase separately can perturb the sample, removing important structural information such as chemical interactions at the gel-solid interface, kinetics across boundaries and conformation in the natural state. In order to overcome these limitations a Comprehensive Multiphase-Nuclear Magnetic Resonance (CMP-NMR) probe has been developed, and is introduced here, that permits all bonds in all phases to be studied and differentiated in whole unaltered natural samples. The CMP-NMR probe is built with high power circuitry, Magic Angle Spinning (MAS), is fitted with a lock channel, pulse field gradients, and is fully susceptibility matched. Consequently, this novel NMR probe has to cover all HR-MAS aspects without compromising power handling to permit the full range of solution-, gel- and solid-state experiments available today. Using this technology, both structures and interactions can be studied independently in each phase as well as transfer/interactions between phases within a heterogeneous sample. This paper outlines some basic experimental approaches using a model heterogeneous multiphase sample containing liquid-, gel- and solid-like components in water, yielding separate 1H and 13C spectra for the different phases. In addition, 19F performance is also addressed. To illustrate the capability of 19F NMR soil samples, containing two different contaminants, are used, demonstrating a preliminary, but real-world application of this technology. This novel NMR approach possesses a great potential for the in situ study of natural samples in their native state.

  3. 129Xe NMR of xenon adsorbed on the molecular sieves AlPO 4-11 and SAPO-11. Chemical shift anisotropy related to the asymmetry of the adsorption zones

    NASA Astrophysics Data System (ADS)

    Springuel-Huet, M. A.; Fraissard, J.

    1989-01-01

    The form of the 129Xe NMR signal of xenon adsorbed at low concentration on the molecular sieves SAPO-11 and AlPO 4-11 corresponds to a highly anisotropic chemical shift which expresses the asymmetry of the channels in which the xenon is located. To the asymmetry of the xenon-wall interaction is added that of the xenon-xenon interaction when the channels are largely filled.

  4. Solid-state NMR identification and quantification of newly formed aluminosilicate phases in weathered kaolinite systems.

    PubMed

    Crosson, Garry S; Choi, Sunkyung; Chorover, Jon; Amistadi, Mary Kay; O'Day, Peggy A; Mueller, Karl T

    2006-01-19

    The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3-, 1 mol kg-1 of OH-, and pH approximately 13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10(-3), 10(-4), and 10(-5) molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10(-5) m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10(-3) m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and

  5. Solid-State NMR Identification and Quantification of Newly Formed Aluminosilicate Phases in Weathered Kaolinite Systems

    SciTech Connect

    Crosson, Garry S.; Choi, Sunkyung; Chorover, Jon; Amistadi, Mary K.; O'Day, Peggy A.; Mueller, Karl T.

    2006-01-19

    The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3 -, 1 mol kg-1 of OH-, and pH ~13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10-3, 10-4, and 10-5 molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10-5 m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10-3 m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and the quantitative

  6. NMR Studies of Texture in the B-like Phase of 3He in Aerogel

    SciTech Connect

    Dmitriev, V. V.; Zavjalov, V. V.; Zmeev, D. E.; Mulders, N.

    2006-09-07

    Continuous wave NMR experiments have been performed in the B-like phase of 3He in a 98% open aerogel. The results allow us to get information about the texture of the 3He order parameter inside the aerogel. We conclude that in the B-like phase the boundary between the bulk 3He and the aerogel orients the vector of orbital anisotropy (L) parallel to it. Two stable textures and textural transition between them were observed in our sample.

  7. NMR solution studies of hamster galectin-3 and electron microscopic visualization of surface-adsorbed complexes: evidence for interactions between the N- and C-terminal domains.

    PubMed

    Birdsall, B; Feeney, J; Burdett, I D; Bawumia, S; Barboni, E A; Hughes, R C

    2001-04-17

    Galectin-3, a beta-galactoside binding protein, contains a C-terminal carbohydrate recognition domain (CRD) and an N-terminal domain that includes several repeats of a proline-tyrosine-glycine-rich motif. Earlier work based on a crystal structure of human galectin-3 CRD, and modeling and mutagenesis studies of the closely homologous hamster galectin-3, suggested that N-terminal tail residues immediately preceding the CRD might interfere with the canonical subunit interaction site of dimeric galectin-1 and -2, explaining the monomeric status of galectin-3 in solution. Here we describe high-resolution NMR studies of hamster galectin-3 (residues 1--245) and several of its fragments. The results indicate that the recombinant N-terminal fragment Delta 126--245 (residues 1--125) is an unfolded, extended structure. However, in the intact galectin-3 and fragment Delta 1--93 (residues 94--245), N-terminal domain residues lying between positions 94 and 113 have significantly reduced mobility values compared with those expected for bulk N-terminal tail residues, consistent with an interaction of this segment with the CRD domain. In contrast to the monomeric status of galectin-3 (and fragment Delta 1--93) in solution, electron microscopy of negatively stained and rotary shadowed samples of hamster galectin-3 as well as the CRD fragment Delta 1--103 (residues 104--245) show the presence of a significant proportion (up to 30%) of oligomers. Similar imaging of the N-terminal tail fragment Delta 126--245 reveals the presence of fibrils formed by intermolecular interactions between extended polypeptide subunits. Oligomerization of substratum-adsorbed galectin-3, through N- and C-terminal domain interactions, could be relevant to the positive cooperativity observed in binding of the lectin to immobilized multiglycosylated proteins such as laminin. PMID:11294654

  8. Amino Acid-Based Stabilization of Oxide Nanocrystals in Polar Media: From Insight in Ligand Exchange to Solution ¹H NMR Probing of Short-Chained Adsorbates.

    PubMed

    De Roo, Jonathan; Coucke, Sofie; Rijckaert, Hannes; De Keukeleere, Katrien; Sinnaeve, Davy; Hens, Zeger; Martins, José C; Van Driessche, Isabel

    2016-03-01

    Ligand exchange is a crucial step between nanocrystal synthesis and nanocrystal application. Although colloidal stability and ligand exchange in nonpolar media are readily established, the exchange of native, hydrophobic ligands with polar ligands is less systematic. In this paper, we present a versatile ligand exchange strategy for the phase transfer of carboxylic acid capped HfO2 and ZrO2 nanocrystals to various polar solvents, based on small amino acids as the incoming ligand. To gain insight in the fundamental mechanism of the exchange, we study this system with a combination of FTIR, zeta potential measurements, and solution (1)H NMR techniques. The detection of surface-associated, small ligands with solution NMR proves challenging in this respect. Tightly bound amino acids are undetectable, but their existence can be proven through displacement with other ligands in titration experiments. Alternatively, we find that methyl moieties belonging to bound species can circumvent these limitations because of their more favorable relaxation properties as a result of internal mobility. As such, our results are not limited to amino acids but to any short-chained ligand and will therefore facilitate the rigorous investigation and understanding of various ligand exchange processes. PMID:26854070

  9. NMR studies of Phase Transitions in Alkali Metal Films on Glass Substrates

    NASA Astrophysics Data System (ADS)

    Ishikawa, K.; Patton, B.; Jau, Y.-Y.; Happer, W.

    2006-05-01

    We report NMR spectra of thin ^87Rb films on glass in an investigation of the ``curing'' process which is commonly observed in alkali cells. The cells were cycled in temperature over a range of 5 C to 170 C and the rubidium solid-liquid phase transition was studied. The spectra of these two phases are resolvable at 9.4 T because of their different Knight shifts. Hysteresis in the observed phases confirmed reports of a curing phenomenon, and after time a supercooled liquid Rb peak could be detected at temperatures far below the predicted freezing point of 39 C. Moreover, a third NMR peak was observed at temperatures below the melting point whose frequency varied with temperature and spanned the solid and liquid frequency ranges. To our knowledge, this is the first study to characterize this additional resonance. We have also performed analogous measurements on ^133Cs films.

  10. 1H-NMR study of the three low temperature phases of DPPC-water systems.

    PubMed

    Trahms, L; Klabe, W D; Boroske, E

    1983-06-01

    The three phases of dipalmitoylphosphatidylcholine-water dispersions, occurring below the main transition are studied by a moment analysis of 1H-nuclear magnetic resonance (NMR) spectra. The subtransition, recently detected by Chen, S. C., J. M. Sturtevant, and B. J. Gaffney, 1980, Pro. Natl. Acad. Sci. USA, 77:5060-5063, is characterized by a sharp drop in the second moment at 12 degrees C as a result of increasing the temperature. Interesting features of this phase transition are a hysteresis of 11 K and extremely slow kinetics. It is interpreted as the onset of a flip-flop of the hydrocarbon chains about their long axis. At the pretransition, this type of motion is assumed to change into a fast rotation. The proposed models for the three phases are confirmed by computer calculations of theoretical values for the second and fourth moments of the corresponding NMR signals. PMID:6688190

  11. {207}Pb MAS NMR and conductivity identified anomalous phase transition in nanostructured PbF {2}

    NASA Astrophysics Data System (ADS)

    Thangadurai, P.; Ramasamy, S.; Manoharan, P. T.

    2004-02-01

    Lead fluoride, a superionic conductor was prepared in its nanostructured form by Inert Gas Condensation Technique (IGCT) using an Ultra High Vacuum (UHV) chamber. The average grain size was found to be in the range 9 to 43 nm. The existence of mixed phases (α and β-PbF2) was identified using XRD. Solid state 207Pb MAS NMR was carried to average out the dipolar interaction and the resultant isotropic peaks were assigned to the corresponding phases. At high spinning frequencies, one isotropic peak emerged from the contribution of the grain boundary region. The relative intensity of this peak is reduced as the grain size is increased, independent of the concentration of the phases. This is related to the fact that the volume fraction of grain boundary atoms in nanostructured materials increases with the reduction of grain size. The width of the NMR resonance peak is found to be reduced as the grain size goes down. The structural phase transformations were identified at two different temperature regions. The first phase transformation from β to α phase in the annealing temperature range 573 K to 623 K is attributed to some anomalies related to the material microstructure and this has not been reported in earlier literatures. The second phase transformation from α to β in the temperature range 623 K to 673 K is similar to the already reported transformation. Electrical conductivity σ , of the samples was obtained from the complex impedance spectroscopy studies. Conduction species was identified as F- ion through anion vacancies. The magnitude of the conductivity varied according to the dominant phase available when the grain size is higher. But at lower grain sizes below 20 nm, it shows enhanced conductivity that is attributed to the grain size effect. The NMR and conductivity data have jointly supported the anomalous phase transition at the annealing temperature of 623 K.

  12. Halloysite Nanotubes as a New Adsorbent for Solid Phase Extraction and Spectrophotometric Determination of Iron in Water and Food Samples

    NASA Astrophysics Data System (ADS)

    Samadi, A.; Amjadi, M.

    2016-07-01

    Halloysite nanotubes (HNTs) have been introduced as a new solid phase extraction adsorbent for preconcentration of iron(II) as a complex with 2,2-bipyridine. The cationic complex is effectively adsorbed on the sorbent in the pH range of 3.5-6.0 and efficiently desorbed by trichloroacetic acid. The eluted complex has a strong absorption around 520 nm, which was used for determination of Fe(II). After optimizing extraction conditions, the linear range of the calibration graph was 5.0-500 μg/L with a detection limit of 1.3 μg/L. The proposed method was successfully applied for the determination of trace iron in various water and food samples, and the accuracy was assessed through the recovery experiments and analysis of a certified reference material (NIST 1643e).

  13. The polymorphic phases of the hexaalkanoyloxytriphenylene liquid crystals, as studied by deuterium NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Goldfarb, D.; Lifshitz, E.; Zimmermann, H.; Luz, Z.

    1985-06-01

    Deuterium NMR spectra are reported for several specifically deuterated hexaalkanoyloxytriphenylenes in their corresponding liquid crystalline phases. The higher homologs of this series are polymorphic and exhibit a variety of discotic mesophases, including both biaxial (D0 and D1) and uniaxial (D2) columnar phases. The ordering characteristics of these phases are studied using the quadrupolar splittings of the aromatic and aliphatic deuterons. The results show that during the transition from the biaxial D1 to the axial D2 phase the major susceptibility tensor switch orientation, apparently due to strong tilting of the molecules with respect to the columnar axis in the biaxial phase. Characteristic features which appear in the spectra of these phases are interpreted in terms of intercolumnar jumps of mesogen molecules.

  14. Effect of the endcapping of reversed-phase high-performance liquid chromatography adsorbents on the adsorption isotherm

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2005-09-01

    The retention mechanisms of n-propylbenzoate, 4-t ert-butylphenol, and caffeine on the endcapped Symmetry-C{sub 18} and the non-endcapped Resolve-C{sub 18} are compared. The adsorption isotherms were measured by frontal analysis (FA), using as the mobile phase mixtures of methanol or acetonitrile and water of various compositions. The isotherm data were modeled and the adsorption energy distributions calculated. The surface heterogeneity increases faster with decreasing methanol concentration on the non-endcapped than on the endcapped adsorbent. For instance, for methanol concentrations exceeding 30% (v/v), the adsorption of caffeine is accounted for by assuming three and two different types of adsorption sites on Resolve-C{sub 18} and Symmetry-C{sub 18}, respectively. This is explained by the effect of the mobile phase composition on the structure of the C{sub 18}-bonded layer. The bare surface of bonded silica appears more accessible to solute molecules at high water contents in the mobile phase. On the other hand, replacing methanol by a stronger organic modifier like acetonitrile dampens the differences between non-endcapped and endcapped stationary phase and decreases the degree of surface heterogeneity of the adsorbent. For instance, at acetonitrile concentrations exceeding 20%, the surface appears nearly homogeneous for the adsorption of caffeine.

  15. Polarization transfer solid-state NMR for studying surfactant phase behavior.

    PubMed

    Nowacka, Agnieszka; Mohr, Parveen Choudhary; Norrman, Jens; Martin, Rachel W; Topgaard, Daniel

    2010-11-16

    The phase behavior of amphiphiles, e.g., lipids and surfactants, at low water content is of great interest for many technical and pharmaceutical applications. When put in contact with air having a moderate relative humidity, amphiphiles often exhibit coexistence between solid and liquid crystalline phases, making their complete characterization difficult. This study describes a (13)C solid-state NMR technique for the investigation of amphiphile phase behavior in the water-poor regime. While the (13)C chemical shift is an indicator of molecular conformation, the (13)C signal intensities obtained with the CP and INEPT polarization transfer schemes yield information on molecular dynamics. A theoretical analysis incorporating the effect of molecular segment reorientation, with the correlation time τ(c) and order parameter S, shows that INEPT is most efficient for mobile segments with τ(c) < 0.01 μs and S < 0.05, while CP yields maximal signal for rigid segments with τ(c) > 10 μs and/or S > 0.5 under typical solid-state NMR experimental conditions. For liquid crystalline phases, where τ(c) < 0.01 μs and 0 < S < 0.3, the observed CP and INEPT intensities serve as a gauge of S. The combination of information on molecular conformation and dynamics permits facile phase diagram determination for systems with solid crystalline, solid amorphous, anisotropic liquid crystalline, and isotropic liquid (crystalline) phases as demonstrated by experiments on a series of reference systems with known phase structure. Three solid phases (anhydrous crystal, dihydrate, gel), two anisotropic liquid crystalline phases (normal hexagonal, lamellar), and two isotropic liquid crystalline phases (micellar cubic, bicontinuous cubic) are identified in the temperature-composition phase diagram of the cetyltrimethylammonium succinate/water system. Replacing the succinate counterion with DNA prevents the formation of phases other than hexagonal and leads to a general increase of τ(c). PMID

  16. Theoretical study of the three-phase contact line and its tension in adsorbed colloid-polymer mixtures.

    PubMed

    Vandecan, Yves; Indekeu, Joseph O

    2008-03-14

    We perform a theoretical study of the three-phase contact line and the line tension in an adsorbed colloid-polymer mixture near a first-order wetting transition, employing an interface displacement model. We use a simple free-energy functional to describe a colloid-polymer mixture near a hard wall. The bulk phase behavior and the substrate-adsorbate interaction are modeled by the free-volume theory for ideal polymers. The large size of the colloidal particles and the suppression of the van der Waals interaction by optical matching of colloid and solvent justify the planar hard wall model for the substrate. Following the Fisher-Jin scheme, we derive from the free-energy functional an interface potential V(l) for these mixtures. For a particle diameter of 10-100 nm, the calculations indicate a line tension tau approximately 10(-12)-10(-13) N at room temperature. In view of the ultralow interfacial tension in colloid-polymer mixtures, gamma approximately 10(-7) Nm, this leads to a rather large characteristic length scale taugamma in the micrometer range for the three-phase contact zone width. In contrast with molecular fluids, this zone could be studied directly with optical techniques such as confocal scanning laser microscopy. PMID:18345923

  17. Optical pumping and xenon NMR

    SciTech Connect

    Raftery, M.D.

    1991-11-01

    Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping [sup 129]Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

  18. Optical pumping and xenon NMR

    SciTech Connect

    Raftery, M.D.

    1991-11-01

    Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping {sup 129}Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the {sup 131}Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

  19. A {sup 13}C NMR study of the condensation chemistry of acetone and acetaldehyde adsorbed at the Bronsted acid sites in H-ZSM-5

    SciTech Connect

    Biaglow, A.I.; Sepa, J.; Gorte, R.J.

    1995-02-01

    Several bimolecular, acid-catalyzed condensation reactions of acetone and acetaldehyde have been examined in H-ZSM-5, along with the adsorption complexes formed by the products, using {sup 13}C NMR. For acetone, the hydrogen-bonded adsorption complex is stable at room temperature and coverages below one molecule per Broensted acid site. Reaction to mesityl oxide occurs only at higher coverages or temperatures, which are necessary to induce site exchange. The adsorption complex exhibits reaction chemistry analogous to that observed in solution phase, forming adsorption complexes of chloroacetone upon exposure to Cl{sub 2} and of imines upon exposure to NH{sub 3} or dimethylamine. The reactions of acetaldehyde to crotonaldehyde and imines are similar, although they occur at a faster rate due to the higher mobility of this molecule. The adsorption complexes formed by acetone, acetaldehyde, and their condensation products can all be described as rigid, hydrogen-bonded complexes at low coverages. Complexes formed from imines and enamines exhibit isotropic chemical shifts nearly identical to those observed in magic acids, indicating that proton transfer is nearly complete for these molecules. The extent of proton transfer for the remaining molecules varies with the proton affinity of the molecule, ranging from close to complete proton transfer for mesityl oxide and crotonaldehyde to almost complete absence of proton transfer for the chloroacetones. The differences and similarities between these reactions in the zeolite and in solution phase are discussed, along with the implications for understanding the primary processes responsible for these reactions in zeolites. 34 refs., 16 figs., 1 tab.

  20. Phase behaviour of a dispersion of charge-stabilised colloidal spheres with added non-adsorbing interacting polymer chains.

    PubMed

    Gögelein, C; Tuinier, R

    2008-10-01

    We present a theory for the phase behaviour of mixtures of charge-stabilised colloidal spheres plus interacting polymer chains in good and theta -solvents within the framework of free-volume theory. We use simple but accurate combination rules for the depletion thickness around a colloidal particle and for the osmotic pressure up to the semi-dilute concentration regime. Hence, we obtain expressions for the free energy for mixtures of charged colloidal particles and non-adsorbing interacting polymers. From that, we calculate the phase behaviour, and discuss its topology in dependence on the competition between the charge-induced repulsion and the polymer-induced attraction. The homogeneous mixture of colloids and polymers becomes more stabilised against demixing when increasing the electrostatic repulsion. This charge-induced stabilisation is strongest for small polymer-to-colloid size ratios and is more pronounced for charged colloids mixed with polymers in a good solvent than for polymers in a theta -solvent. For the weakly charged regime we find that the phase diagram becomes salt-concentration-independent in the protein limit for charged colloids plus polymers in a theta -solvent. The liquid window, i.e., the concentration regimes where a colloidal liquid exists, is narrowed down upon increasing the charge-induced repulsion. Also this effect is more pronounced when charged colloids are mixed with polymer chains in a good solvent. In summary, we demonstrate that the solvent quality significantly influences the phase behaviour of mixtures of charged colloids plus non-adsorbing polymers if the range of the screened electrostatic repulsion becomes of the order of the range of the depletion-induced attraction. PMID:18791755

  1. NMR signal analysis to characterize solid, aqueous, and lipid phases in baked cakes.

    PubMed

    Le Grand, F; Cambert, M; Mariette, F

    2007-12-26

    Proton mobility was studied in molecular fractions of some model systems and of cake using a 1H nuclear magnetic resonance (NMR) relaxation technique. For cake, five spin-spin relaxation times (T2) were obtained from transverse relaxation curves: T2 (1) approximately 20 micros, T2 (2) approximately 0.2 ms, T2 (3) approximately 3 ms, T2 (4) approximately 50 ms, and T2 (2) approximately 165 ms. The faster component was attributed to the solid phase, components 2 and 3 were associated with the aqueous phase, and the two slowest components were linked to the lipid phase. After cooking, the crust contained more fat but less water than the center part of the cake. The amount of gelatinized starch was lower in the crust, and water was more mobile due to less interaction with macromolecules. This preliminary study revealed different effects of storage on the center and crust. PMID:18044835

  2. Pulsed NMR in the nuclear spin ordered phases of solid 3He in a silver sinter

    NASA Astrophysics Data System (ADS)

    Millan-Chacartegui, Carmen; Schuberth, Erwin A.; Deppe, Frank; Schöttl, Stephan

    2003-05-01

    To obtain the exact spin structure of the nuclear magnetically ordered phases of solid 3He, in the BCC lattice called U2D2 and high field phase, both occurring below about 1 mK, we started a project of neutron scattering from the solid at the Hahn-Meitner Institut, Berlin. This experiment faces three main difficulties: to cool the solid to temperatures below 1 mK (or even much lower in the case of the HCP lattice), to keep it there under neutron flux, and to grow a single crystal within the sintered material needed for this purpose. As a first step we have performed pulsed NMR measurements in the ordered phases of solid 3He in a silver sinter of 700 Å particle size down to temperatures of 600 μK at various molar volumes. The samples remained in the ordered state for as long as 110 h.

  3. Homogeneous coexistence and phase segregation in 1111 iron-based pnictides studied via NMR

    NASA Astrophysics Data System (ADS)

    Fujiwara, Naoki; Kamihara, Yoichi; Matsuishi, Satoru; Hosono, Hideo

    2013-06-01

    We performed 75As and 51Co nuclear magnetic resonance (NMR) measurements on LaFeAsO1- x F x (La1111), a prototype of iron-based superconductors, and on Ca(Fe1- x Co x )AsF (Ca1111), which has a small overlap between the antiferromagnetic (AF) and superconducting (SC) domes in the electronic phase diagram. We found in the Ca1111 series that AF and SC states coexist homogeneously in the overlapped region, while in the La1111 series, we found that paramagnetic (PM) and SC domains coexist around the AF-SC phase boundary. The coexistence of these domains indicates that the AF and SC domes segregate from each other in the electronic phase diagram.

  4. Dipolar recoupling in solid state NMR by phase alternating pulse sequences

    PubMed Central

    Lin, J.; Bayro, M.; Griffin, R. G.; Khaneja, N.

    2009-01-01

    We describe some new developments in the methodology of making heteronuclear and homonuclear recoupling experiments in solid state NMR insensitive to rf-inhomogeneity by phase alternating the irradiation on the spin system every rotor period. By incorporating delays of half rotor periods in the pulse sequences, these phase alternating experiments can be made γ encoded. The proposed methodology is conceptually different from the standard methods of making recoupling experiments robust by the use of ramps and adiabatic pulses in the recoupling periods. We show how the concept of phase alternation can be incorporated in the design of homonuclear recoupling experiments that are both insensitive to chemical-shift dispersion and rf-inhomogeneity. PMID:19157931

  5. Recoupling in solid state NMR using γ prepared states and phase matching

    PubMed Central

    Lin, James; Griffin, R.G.; Khaneja, Navin

    2014-01-01

    The paper describes two-dimensional solid state NMR experiments that use powdered dephased anti-phase coherence (γ preparation) to encode chemical shifts in the indirect dimension. Both components of this chemical shift encoded gamma-prepared states can be refocused into inphase coherence by a recoupling element. This helps to achieve sensitivity enhancement in 2D NMR experiments by quadrature detection. The powder dependence of the gamma-prepared states allows for manipulating them by suitable insertion of delays in the recoupling periods. This helps to design experiments that suppress diagonal peaks in 2D spectra, leading to improved resolution. We describe some new phase modulated heteronuclear and homonuclear recoupling pulse sequences that simplify the implementation of the described experiments based on γ prepared states. Recoupling in the heteronuclear spin system is achieved by matching the difference in the amplitude of the sine/cosine modulated phase on the two rf-channels to the spinning frequency while maintaining the same power on the two rf-channels. PMID:21889380

  6. Positive frequency shifts observed upon adsorbing micron-sized solid objects to a quartz crystal microbalance from the liquid phase.

    PubMed

    Pomorska, Agata; Shchukin, Dmitry; Hammond, Richard; Cooper, Matthew A; Grundmeier, Guido; Johannsmann, Diethelm

    2010-03-15

    By specifically binding derivatized colloidal particles and physisorbing nonderivatized particles to the surface of a quartz crystal microbalance (QCM), we have observed positive shifts of frequency, Deltaf, in contrast to the negative frequency shifts typically found in adsorption experiments. Evidently, the Sauerbrey relation does not apply to this situation. A comparison of frequencies shifts and bandwidths on different overtones reveals a coupled resonance: at low overtones, Deltaf is negative, whereas it is positive at high overtones, with maximal resonance bandwidth observed at the crossover point. As predicted by the Dybwad model, the spheres bound to the surface form resonating systems on their own. A composite resonator is formed, consisting of a large crystal with resonance frequency omega and the adsorbed spheres with resonance frequency omega(S). In the case in which the resonance frequency of the small spheres (firmly attached to crystal), omega(S), is higher than the resonance frequency of the crystal, omega, Deltaf of the composite system is negative (leading to the Sauerbrey limit). In the opposite limit (that is, in the case of large adsorbed particles bound to the sensor surface via a sufficiently weak bridge) Deltaf is positive. Such a behavior is known from sphere-plate contacts in the dry state. Finite element calculation demonstrates that this phenomena is also plausible in liquid phase media, with Deltaf critically dependent on the strength of the sphere-plate contact. Operated in this mode, the QCM most likely probes the contact strength, rather than the mass of the particle. PMID:20166672

  7. Magnetic nano graphene oxide as solid phase extraction adsorbent coupled with liquid chromatography to determine pseudoephedrine in urine samples.

    PubMed

    Taghvimi, Arezou; Hamishehkar, Hamed; Ebrahimi, Mahmoud

    2016-01-15

    This paper reports on a method based on magnetic solid phase extraction (MSPE) for the determination of pseudoephedrine. Magnetic nanographene oxide (MNGO) was applied as a new adsorbent for the extraction of pseudoephedrine from urine samples. Synthesis of MNGO was characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The main factors influencing extraction efficiency, including the amounts of sample volume, amount of adsorbent, type and amount of extraction organic solvent, time of extraction and desorption, pH, ionic strength of extraction medium, and agitation rate, were investigated and optimized. Under optimized extraction conditions, a good linearity was observed in the range of 100-2000ng/mL with a correlation coefficient of 0.9908 (r(2)). Limit of detection (LOD) and limit of quantification (LOQ) were 25 and 82.7ng/mL, respectively. Inter-day and intra-day precision and accuracy were 6.01 and 0.34 (%), and 8.70 and 0.29 (%), respectively. The method was applied for the determination of pseudoephedrine in urine samples of volunteers receiving pseudoephedrine with the recovery of 96.42. It was concluded that the proposed method can be applied in diagnostic clinics. PMID:26708626

  8. Distinguishing Bicontinuous Lipid Cubic Phases from Isotropic Membrane Morphologies Using 31P Solid-State NMR Spectroscopy

    PubMed Central

    Yang, Yu; Yao, Hongwei

    2015-01-01

    Nonlamellar lipid membranes are frequently induced by proteins that fuse, bend, and cut membranes. Understanding the mechanism of action of these proteins requires the elucidation of the membrane morphologies that they induce. While hexagonal phases and lamellar phases are readily identified by their characteristic solid-state NMR lineshapes, bicontinuous lipid cubic phases are more difficult to discern, since the static NMR spectra of cubic-phase lipids consist of an isotropic 31P or 2H peak, indistinguishable from the spectra of isotropic membrane morphologies such as micelles and small vesicles. To date, small-angle X-ray scattering is the only method to identify bicontinuous lipid cubic phases. To explore unique NMR signatures of lipid cubic phases, we first describe the orientation distribution of lipid molecules in cubic phases and simulate the static 31P chemical shift lineshapes of oriented cubic-phase membranes in the limit of slow lateral diffusion. We then show that 31P T2 relaxation times differ significantly between isotropic micelles and cubic-phase membranes: the latter exhibit two-orders-of magnitude shorter T2 relaxation times. These differences are explained by the different timescales of lipid lateral diffusion on the cubic-phase surface versus the timescales of micelle tumbling. Using this relaxation NMR approach, we investigated a DOPE membrane containing the transmembrane domain (TMD) of a viral fusion protein. The static 31P spectrum of DOPE shows an isotropic peak, whose T2 relaxation times correspond to that of a cubic phase. Thus, the viral fusion protein TMD induces negative Gaussian curvature, which is an intrinsic characteristic of cubic phases, to the DOPE membrane. This curvature induction has important implications to the mechanism of virus-cell fusion. This study establishes a simple NMR diagnostic probe of lipid cubic phases, which is expected to be useful for studying many protein-induced membrane remodeling phenomena in biology

  9. Two confined phases of argon adsorbed inside open single walled carbon nanotubes.

    PubMed

    Jakubek, Zygmunt J; Simard, Benoit

    2004-07-01

    Isothermal adsorption of Ar on single walled carbon nanotubes (SWNTs) has been studied at 77 and 87 K. The SWNTs have been grown by laser vaporization of a graphite pellet containing 0.6% (atomic) Ni/Co catalyst. The nanotubes have been prepared for argon adsorption measurements by prolonged outgassing of as-grown material in a vacuum at room temperature (295 K), at elevated temperatures of up to 475 K, and by oxidization for 2 h in dry air at 470 K. Formation of two condensed phases of Ar in the interior of SWNTs has been observed at 77 K. The low-density phase is formed at 155(5) microTorr, while the high-density phase, at 120(5) microTorr. At 87 K, only a single phase has been observed at 185(5) microTorr. Condensation at both 77 and 87 K appears to be the first-order phase transition. Onset of the quasi-one-dimensional linear (one-channel) phase and the quasi-two-dimensional monolayer (six-channel) phase formation on the external surface of bundles has been observed at 77 K near 0.0017 and 0.8 Torr, respectively, and at 87 K near 0.018 and 5 Torr, respectively. Isosteric heats of adsorption for the one-channel phase, the first external layer, and the second external layer have been determined to be equal to 137, 107, and 70 meV, respectively. PMID:16459613

  10. Electronic properties and phase transitions of RbC60 and CsC60: Investigation by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Tycko, R.; Dabbagh, G.; Murphy, D. W.; Zhu, Q.; Fischer, J. E.

    1993-09-01

    We report the results of 133Cs, 87Rb, and 13C NMR measurements on the alkali-metal fullerides CsC60 and RbC60. Measurements of NMR spectra and spin-lattice relaxation rates provide clear evidence for phase transitions near 300 K in both compounds, with substantial changes in their electronic properties at the phase transitions. The high-temperature phases are paramagnets, with an exchange coupling of roughly 2 cm-1 between electron spins that are localized primarily on C-60 ions. The 133Cs and 87Rb NMR frequency shifts and relaxation rates are determined by Fermi contact hyperfine couplings to the electron spins. The 13C relaxation rates are determined by dipolar hyperfine couplings. The electron-spin susceptibility is greatly reduced in the low-temperature phases

  11. NMR Properties of the Polar Phase of Superfluid ^3He in Anisotropic Aerogel Under Rotation

    NASA Astrophysics Data System (ADS)

    Mineev, V. P.

    2016-09-01

    The polar phase of superfluid ^3He is stable in "nematically ordered" densed aerogel. A rotating vessel with the polar superfluid can be filled either by an array of the single quantum vortices or by an array of the half-quantum vortices. It is shown that the inhomogeneous distribution of the spin part of the order parameter arising in an array of half-quantum vortices in strong enough magnetic field tilted to the average direction of aerogel strands leads to the appearance of a satellite in the NMR signal shifted in the negative direction with respect to the Larmor frequency. The satellite is absent in the case of an array of single quantum vortices which allows to distinguish these two configurations. The polar state in the anisotropic aerogel with lower density transforms at lower temperatures to the axipolar state. The array of half-quantum vortices created in the polar phase keeps its structure under transition to the axipolar state. The temperature dependence of the vortex-satellite NMR frequency is found to be slower below the transition temperature to the axipolar state.

  12. NMR Properties of the Polar Phase of Superfluid ^3 He in Anisotropic Aerogel Under Rotation

    NASA Astrophysics Data System (ADS)

    Mineev, V. P.

    2016-04-01

    The polar phase of superfluid ^3 He is stable in "nematically ordered" densed aerogel. A rotating vessel with the polar superfluid can be filled either by an array of the single quantum vortices or by an array of the half-quantum vortices. It is shown that the inhomogeneous distribution of the spin part of the order parameter arising in an array of half-quantum vortices in strong enough magnetic field tilted to the average direction of aerogel strands leads to the appearance of a satellite in the NMR signal shifted in the negative direction with respect to the Larmor frequency. The satellite is absent in the case of an array of single quantum vortices which allows to distinguish these two configurations. The polar state in the anisotropic aerogel with lower density transforms at lower temperatures to the axipolar state. The array of half-quantum vortices created in the polar phase keeps its structure under transition to the axipolar state. The temperature dependence of the vortex-satellite NMR frequency is found to be slower below the transition temperature to the axipolar state.

  13. Development of novel adsorbents for the control of vapor- phase mercury emissions

    NASA Astrophysics Data System (ADS)

    Liu, Wei

    Efficient sulfur-impregnated activated carbon-based (SIAC) sorbents for elemental mercury vapors were developed and evaluated in this study. The key parameters of the impregnation protocol included impregnation temperature and initial sulfur to carbon ratio (SCR). Gas constituents and temperature were the key process parameters studied for their impact on sorbent performance. Impregnation temperature is the major impregnation parameter that dominated the performance of SIACs. Performance deteriorated quickly as the impregnation temperature was lowered below 400°C. Higher impregnation temperatures facilitated the presence of more active short-chain S molecules, larger adsorbent surface area, greater fraction of meso-pores, and stronger sulfur-carbon bonding. SCR showed moderate impact on mercury uptake with a 50% decrease in sorbent capacity from highest SCR (4:1) to lowest SCR (1:2). Impact of gas constituents was investigated individually. CO2 (5 and 15%) behaved as inert gas and did not change the performance of SIAC. Also, trace amount of SO2 (300 ppm) and NO (500 ppm) did not alter its performance. Thermogravimetric Analysis showed that micro-structure of SIAC was unchanged after contacting trace pollutants. Low O2 concentration (3%) did not change the performance of SIAC, while high O2 concentration (6% and 9%) increased its capacity by 16% and 30%, respectively. It is postulated that SIAC catalyzed the formation of HgO in the presence of high O2 concentrations. High moisture concentration (10%) decreased SIAC's capacity by 25% while low moisture concentration (5%) showed no impact. It was assumed that water blocked the entrances to the active sites of carbon. H2 formation and hydrogen bonding could have also retarded mercury-sulfur reaction. SIAC's performance was negligible at 250 or 400°C due to the exothermic nature of Hg and S reaction, while its capacity at 140°C increased by 14% as smaller sorbent particle size (170 x 230) was used instead of 60 x 80

  14. C-13 NMR spectroscopy of K(x)C60 - Phase separation, molecular dynamics, and metallic properties

    NASA Astrophysics Data System (ADS)

    Tycko, R.; Dabbagh, G.; Rosseinsky, M. J.; Murphy, D. W.; Fleming, R. M.; Ramirez, A. P.; Tully, J. C.

    1991-08-01

    The results of C-13 NMR measurements on alkali fullerides K(x)C60 are reported. The NMR spectra demonstrate that material with x of 0-3 is in fact a two-phase system at equilibrium, with x = 0 and x = 3. NMR lineshapes indicate that C60(3-) ions rotate rapidly in the K3C60 phase at 300 K, while C60(6-) ions in the insulating K6C60 phase are static on the time scale of the lineshape measurement. The temperature dependence of the C-13 spin-lattice relaxation rate in the normal state of K3C60 is found to be characteristic of a metal, indicating the important role of the C60(3-) ions in the conductivity. From the relaxation measurements, an estimate of the density of electronic states at the Fermi level is derived.

  15. NMR properties of hydrogen-bonded glycine cluster in gas phase

    NASA Astrophysics Data System (ADS)

    Carvalho, Jorge R.; da Silva, Arnaldo Machado; Ghosh, Angsula; Chaudhuri, Puspitapallab

    2016-11-01

    Density Functional Theory (DFT) calculations have been performed to study the effect of the hydrogen bond formation on the Nuclear Magnetic Resonance (NMR) parameters of hydrogen-bonded clusters of glycine molecules in gas-phase. DFT predicted isotropic chemical shifts of H, C, N and O of the isolated glycine with respect to standard reference materials are in reasonable agreement with available experimental data. The variations of isotropic and anisotropic chemical shifts for all atoms constituting these clusters containing up to four glycine molecules have been investigated systematically employing gradient corrected hybrid B3LYP functional with three different types of extended basis sets. The clusters are mainly stabilized by a network of strong hydrogen bonds among the carboxylic (COOH) groups of glycine monomers. The formation of hydrogen bond influences the molecular structure of the clusters significantly which, on the other hand, gets reflected in the variations of NMR properties. The carbon (C) atom of the sbnd COOH group, the bridging hydrogen (H) and the proton-donor oxygen (O) atom of the Osbnd H bond suffer downfield shift due to the formation of hydrogen bond. The hydrogen bond lengths and the structural complexity of the clusters are found to vary with the number of participating monomers. A direct correlation between the hydrogen bond length and isotropic chemical shift of the bridging hydrogen is observed in all cases. The individual variations of the principal axis elements in chemical shift tensor provide additional insight about the different nature of the monomers within the cluster.

  16. Phase diagram of oxygen adsorbed on Ni(111) and thermodynamic properties from first-principles

    NASA Astrophysics Data System (ADS)

    Lazo, C.; Keil, F. J.

    2009-06-01

    The thermodynamic properties and the surface phase diagram of O/Ni(111) have been calculated from Metropolis and Wang-Landau Monte Carlo simulations based on lateral interactions derived from density-functional theory (DFT) calculations. The DFT energies were mapped onto an Ising-like Hamiltonian according to the cluster expansion technique formalism. Both fcc and hcp adsorption sites were included in the Hamiltonian. Different criteria were used to evaluate competing parameter sets: cross-validation score CV, Mallow’s Cp statistics, and adjusted R2 statistics. The parameter space was searched using genetic algorithms in order to find optimum parameter sets. The different parameter sets obtained from different criteria lead essentially to the same transition temperatures. Excellent agreement is found when comparing the shape and the stability regions of the theoretical and the experimental (from the literature) phase diagrams. We investigate the nature of the p(2×2) and (3×3)R30° phase transitions at Θ=1/4 and 1/3 ML, respectively. Differences arise when comparing the values of the calculated and the experimental transition temperatures owing to imprecision in present-day DFT calculations.

  17. NMR studies of granular media and two-phase flow in porous media

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoyu

    This dissertation describes two experimental studies of a vibrofluidized granular medium and a preliminary study of two-phase fluid flow in a porous medium using Nuclear Magnetic Resonance (NMR). The first study of granular medium is to test a scaling law of the rise in center of mass in a three-dimensional vibrofluidized granular system. Our granular system consisted of mustard seeds vibrated vertically at 40 Hz from 0g to 14g. We used Magnetic Resonance Imaging (MRI) to measure density profile in vibrated direction. We observed that the rise in center of mass scaled as nu 0alpha/Nlbeta with alpha = 1.0 +/- 0.2 and beta = 0.5 +/- 0.1, where nu 0 is the vibration velocity and Nl is the number of layers of grains in the container. A simple theory was proposed to explain the scaling exponents. In the second study we measured both density and velocity information in the same setup of the first study. Pulsed Field Gradient (PFG)-NMR combined with MRI was used to do this measurement. The granular system was fully fluidized at 14.85g 50 Hz with Nl ≤ 4. The velocity distributions at horizontal and vertical direction at different height were measured. The distributions were nearly-Gaussian far from sample bottom and non-Gaussian near sample bottom. Granular temperature profiles were calculated from the velocity distributions. The density and temperature profile were fit to a hydrodynamic theory. The theory agreed with experiments very well. A temperature inversion near top was also observed and explained by additional transport coefficient from granular hydrodynamics. The third study was the preliminary density measurement of invading phase profile in a two-phase flow in porous media. The purpose of this study was to test an invasion percolation with gradient (IPG) theory in two-phase flow of porous media. Two phases are dodecane and water doped with CuSO4. The porous medium was packed glass beads. The front tail width sigma and front width of invading phase were

  18. Gas-Phase Infrared and NMR Investigation of the Conformers of Diacetone Diperoxide (DADP).

    PubMed

    Guo, Chunlei; Persons, John; Woodford, Jeffrey N; Harbison, Gerard S

    2015-10-01

    Gas-phase infrared measurements of diacetone diperoxide (DADP) indicate a chair conformation with less than 5% of the predicted twist conformer. Vibrational frequencies are very similar to those previously measured in the solid state. Solution NMR measurements using 2D exchange spectroscopy (EXSY) also set a very low maximum limit on the equilibrium population of the twist conformer, with a room-temperature free-energy difference in excess of 14.5 kJ/mol. These experimental results are in accord with high-level quantum calculations incorporating full thermochemistry and solvation effects, which indicate a free-energy difference in the range of 14.7-17.5 kJ/mol in polar solvents. PMID:26387762

  19. Phase transfer of citrate stabilized gold nanoparticles using nonspecifically adsorbed polymers.

    PubMed

    Alkilany, Alaaldin M; Caravana, Aidan C; Hamaly, Majd A; Lerner, Kevin T; Thompson, Lucas B

    2016-01-01

    Many synthetic approaches for gold nanoparticles rely on an aqueous media, resulting in water-soluble nanoparticles, which limits the ability to incorporate gold nanoparticles into other organic solvents or hydrophobic polymeric composites. Surface functionalization and phase transfer approaches using alkylthiols or alkylamines, which strongly bind the gold surface, are common routes to overcome this limitation, however they are typically challenging methods. In this paper we report an approach to transport citrate capped gold nanoparticles into a variety of solvents, including ones that are hydrophobic and not miscible with water without the need for phase transfer agents. We suspend gold nanoparticles in a water-miscible polar organic solvent that also is a solvent for a hydrophobic polymer. After drying, polymer-stabilized gold nanoparticles were found to be dispersible in various hydrophobic solvents with maintained colloidal stability. This work investigates two hydrophobic polymers, namely (polymethylmethacrylate and polyvinylacetate), which share common chemical motifs but have significantly different physiochemical properties. Interestingly, a significant difference in their ability to stabilize the transferred gold nanoparticles is observed and discussed. PMID:26397907

  20. Commensurate Phases of Kr Adsorbed on Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Mbaye, Mamadou T.; Maiga, Sidi M.; Gatica, Silvina M.

    2016-02-01

    In this paper, we show that Krypton atoms form a commensurate solid (CS) phase with a fractional coverage of one krypton atom per every four carbons on zigzag carbon nanotubes. This is a unique phase, different from the √{3} × √{3} R30° CS monolayer formed on graphite, which has a lower coverage of one krypton atom per every six carbons. Our prediction disagrees with experiments that observe in nanotubes the same solid structure found on graphite. In order to address this discrepancy, we simulated adsorption of Kr on zigzag and armchair single-walled carbon nanotubes with radii ranging from 4.7 to 28.83 Å. Our simulations confirm that the CS of coverage 1/4 forms on medium-sized zigzag nanotubes. We also found the 1/6-coverage solid on graphene, which represents the infinite-radius limit of a nanotube. Our findings are key to experiments of adsorption on nanotubes where the interpretation and justification of the results are based on the monolayer coverage, such as mass or conductance isotherms measurements.

  1. 31P NMR study of magnetic phase transitions of MnP single crystal under 2 GPa pressure

    NASA Astrophysics Data System (ADS)

    Fan, GuoZhi; Zhao, Bo; Wu, Wei; Zheng, Ping; Luo, JianLin

    2016-05-01

    Superconductivity on the border of the long-range magnetic order has been discovered in MnP under high pressures. In order to investigate the nature of the magnetic properties adjacent to the superconducting state, we performed zero-field 31P NMR for MnP single crystal under ambient and hydrostatic pressure of 2 GPa, respectively. Radio frequency power level was used to determine whether NMR signal originates from a helical state or not. When 2 GPa pressure was applied, the signal from helical state exists even above 160 K, while that from the ferromagnetic phase was not observed. Our NMR results indicate that the magnetic phase which is adjacent to the superconducting state is in a helical magnetic structure.

  2. Selective solid-phase extraction of alpha-tocopherol by functionalized ionic liquid-modified mesoporous SBA-15 adsorbent.

    PubMed

    Li, Min; Pham, Patrisha J; Pittman, Charles U; Li, Tingyu

    2008-10-01

    Ordered mesoporous adsorbents were prepared by physically grafting functionalized ionic liquids onto SBA-15 (a mesoporous siliceous substrate) using incipient wetness immersion method. These adsorbents were successfully applied to the selective extraction and separation of alpha-tocopherol (an isomer of vitamin E) from a model mixture of soybean oil deodorizer distillate. Various parameters affecting adsorption process such as adsorption time, the structures and loadings of ionic liquids, the adsorption isotherm, and the reusability of adsorbent were investigated using liquid-solid extraction. As high as 211 mg/g adsorbent of the adsorption capacity for alpha-tocopherol was obtained through the adsorption isotherm tests using [emim][Gly]/SBA-15 (functionalized ionic liquid 1-ethyl-3-methylimidazolium glycine which was physically coated on SBA-15) as the adsorbent, in which the functionalized ionic liquids contained the amino acid glycine as the anion. The adsorbent [emim][Gly]/SBA-15 also exhibited a very high adsorption selectivity for alpha-tocopherol. The extraction selectivity or the ratio of distribution coefficients between alpha-tocopherol and the major interference component glyceryl triundecanoate (K(d(alpha-tocopherol))/K(d(triglyceride))) was 10.5. The concentration of alpha-tocopherol was significantly increased from 15.6% in original feedstock solution that contained fatty acid methyl ester, triglyceride and alpha-tocopherol to 73.0% after stripping by diethyl ether. Five adsorbent recycle tests showed good reusability of the functionalized ionic liquid-modified mesoporous adsorbent. PMID:18845881

  3. Molecular recognition using corona phase complexes made of synthetic polymers adsorbed on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Jingqing; Landry, Markita P.; Barone, Paul W.; Kim, Jong-Ho; Lin, Shangchao; Ulissi, Zachary W.; Lin, Dahua; Mu, Bin; Boghossian, Ardemis A.; Hilmer, Andrew J.; Rwei, Alina; Hinckley, Allison C.; Kruss, Sebastian; Shandell, Mia A.; Nair, Nitish; Blake, Steven; Şen, Fatih; Şen, Selda; Croy, Robert G.; Li, Deyu; Yum, Kyungsuk; Ahn, Jin-Ho; Jin, Hong; Heller, Daniel A.; Essigmann, John M.; Blankschtein, Daniel; Strano, Michael S.

    2013-12-01

    Understanding molecular recognition is of fundamental importance in applications such as therapeutics, chemical catalysis and sensor design. The most common recognition motifs involve biological macromolecules such as antibodies and aptamers. The key to biorecognition consists of a unique three-dimensional structure formed by a folded and constrained bioheteropolymer that creates a binding pocket, or an interface, able to recognize a specific molecule. Here, we show that synthetic heteropolymers, once constrained onto a single-walled carbon nanotube by chemical adsorption, also form a new corona phase that exhibits highly selective recognition for specific molecules. To prove the generality of this phenomenon, we report three examples of heteropolymer-nanotube recognition complexes for riboflavin, L-thyroxine and oestradiol. In each case, the recognition was predicted using a two-dimensional thermodynamic model of surface interactions in which the dissociation constants can be tuned by perturbing the chemical structure of the heteropolymer. Moreover, these complexes can be used as new types of spatiotemporal sensors based on modulation of the carbon nanotube photoemission in the near-infrared, as we show by tracking riboflavin diffusion in murine macrophages.

  4. The origin of the low efficiency of carbon removal from the Nickel/Yttrium-Stabilized Zirconia triple-phase boundary by adsorbed water

    NASA Astrophysics Data System (ADS)

    Zhang, Yanxing; Yang, Zongxian

    2015-04-01

    Carbon removal from the anode triple-phase boundary (TPB) of solid oxide fuel cells (SOFCs) by adsorbed water molecule was studied using the density functional calculations, and a detailed dynamic picture was presented. It is found that the adsorbed H2O molecule can dissociate easily at the Ni/YSZ interface and on the YSZ part compared with the Ni part and react with the interface carbon to form the CHO species. The dissociation process of CHO to CH and O is more favorable as compared with that of CHO to CO and H. The CH fragment can easily diffuse to the O vacancy formed in the dynamic reaction processes and dissociate into C and H, which regenerates carbon at the interface. This might be the main reasons for the low efficiency of carbon removal from the TPB of Ni/YSZ by adsorbed water.

  5. Theoretical Analysis of Electrochemical Formation and Phase Transition of Oxygenated Adsorbates on Pt(111).

    PubMed

    Chen, Junxiang; Luo, Siwei; Liu, Yuwen; Chen, Shengli

    2016-08-10

    The electrochemical oxygenation processes of Pt(111) surface are investigated by combining density functional theory (DFT) calculations and Monto Carlo (MC) simulations. DFT calculations are performed to construct force-field parameters for computing the energy of (√3 × √3)R30°-structured OH*-H2O* hydrogen-bonding networks (differently dissociated water bilayer) on the Pt(111) surface, with which MC simulations are conducted to probe the reversible H2O* ↔ OH* conversion in OH*-H2O* networks. The simulated isotherm (relation between electrode potential and OH* coverage) agrees well with that predicted by the experimental cyclic voltammetry (CV) in the potential region of 0.55-0.85 V (vs RHE). It is suggested that the butterfly shape of CV in this region is due to different variation trends of Pt-H2O* distance in low and high OH* coverages. DFT calculation results indicate that the oxidative voltammetry in the potential region from 0.85 V to ca. 1.07 V is associated with the dissociation of OH* to O*, which yields surface structures consisting of OH*-H2O* networks and (√3 × √3)-structured O* clusters. The high stability of the half-dissociated water bilayer (OH*-H2O* hydrogen-bonding network with equal OH* and H2O* coverages) formed in the butterfly region makes OH* dissociation initially very difficult in energetics, but become facile once starts due to the destabilization of OH* by the formed O* nearby. This explains the experimentally observed nucleation and growth behavior of O* phase formation and the high asymmetry of oxidation-reduction voltammetry in this potential region. PMID:27377100

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

    PubMed

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

    2011-01-01

    Decreasing the particle size of powdered activated carbon (PAC) by pulverization increases its adsorption capacities for natural organic matter (NOM) and polystyrene sulfonate (PSS, which is used as a model adsorbate). A shell adsorption mechanism in which NOM and PSS molecules do not completely penetrate the adsorbent particle and instead preferentially adsorb near the outer surface of the particle has been proposed as an explanation for this adsorption capacity increase. In this report, we present direct evidence to support the shell adsorption mechanism. PAC particles containing adsorbed PSS were sectioned with a focused ion beam, and the solid-phase PSS concentration profiles of the particle cross-sections were directly observed by means of field emission-scanning electron microscopy/energy-dispersive X-ray spectrometry (FE-SEM/EDXS). X-ray emission from sulfur, an index of PSS concentration, was higher in the shell region than in the inner region of the particles. The X-ray emission profile observed by EDXS did not agree completely with the solid-phase PSS concentration profile predicted by shell adsorption model analysis of the PSS isotherm data, but the observed and predicted profiles were not inconsistent when the analytical errors were considered. These EDXS results provide the first direct evidence that PSS is adsorbed mainly in the vicinity of the external surface of the PAC particles, and thus the results support the proposition that the increase in NOM and PSS adsorption capacity with decreasing particle size is due to the increase in external surface area on which the molecules can be adsorbed. PMID:20851447

  7. Nanogold-Decorated Silica Monoliths as Highly Efficient Solid-Phase Adsorbent for Ultratrace Mercury Analysis in Natural Waters.

    PubMed

    Huber, Jessica; Heimbürger, Lars-Eric; Sonke, Jeroen E; Ziller, Sebastian; Lindén, Mika; Leopold, Kerstin

    2015-11-01

    We propose a novel analytical method for mercury (Hg) trace determination based on direct Hg preconcentration from aqueous solution onto a gold nanoparticle-decorated silica monolith (AuNP@SiO2). Detection of Hg is performed after thermal desorption by means of atomic fluorescence spectrometry. This new methodology benefits from reagent-free, time- and cost-saving procedure, due to most efficient solid-phase adsorbent and results in high sensitive quantification. The excellent analytical performance of the whole procedure is demonstrated by a limit of detection as low as 1.31 ng L(-1) for only one-min accumulation duration. A good reproducibility with standard deviations ≤5.4% is given. The feasibility of the approach in natural waters was confirmed by a recovery experiment in spiked seawater with a recovery rate of 101%. Moreover, the presented method was validated through reference analysis of a submarine groundwater discharge sample by cold vapor-atomic fluorescence spectrometry resulting in a very good agreement of the found values. Hence the novel method is a very promising new tool for low-level Hg monitoring in natural waters providing easy-handling on-site preconcentration, reagent-free stabilization as well as reagent-free, highly sensitive detection. PMID:26460188

  8. Anisotropic sup 2 H NMR spin-lattice relaxation in L sub. alpha. -phase cerebroside bilayers

    SciTech Connect

    Speyer, J.B.; Weber, R.T.; Gupta, S.K.D.; Griffin, R.G. )

    1989-12-12

    A series of {sup 2}H NMR inversion recovery experiments in the L{sub {alpha}} phase of the cerebroside N-palmitoylgalactosylsphingosine (NPGS) have been performed. In these liquid crystalline lipid bilayers the authors have observed substantial anisotropy in the spin-lattice relaxation of the CD{sub 2} groups in the acyl chains. The form and magnitude of the anisotropy varies with position in the chain, being positive in the upper region, decreasing to zero at the 4-position, and reversing sign at the lower chain positions. It is also shown that addition of cholesterol to the bilayer results in profound changes in the anisotropy. These observations are accounted for by a simple motional model of discrete hops among nine sites, which result from the coupling of two modes of motion - long-axis rotational diffusion and guache-trans isomerization. This model is employed in quantitative simulations of the spectral line shapes and permits determination of site populations and motional rates. These results, plus preliminary results in sphingomyelin and lecithin bilayers,illustrate the utility of T{sub 1} anisotropy measurements as a probe of dynamics in L{sub {alpha}}-phase bilayers.

  9. Nonuniform sampling of hypercomplex multidimensional NMR experiments: Dimensionality, quadrature phase and randomization

    PubMed Central

    Schuyler, Adam D; Maciejewski, Mark W; Stern, Alan S; Hoch, Jeffrey C

    2015-01-01

    Nonuniform sampling (NUS) in multidimensional NMR permits the exploration of higher dimensional experiments and longer evolution times than the Nyquist Theorem practically allows for uniformly sampled experiments. However, the spectra of NUS data include sampling-induced artifacts and may be subject to distortions imposed by sparse data reconstruction techniques, issues not encountered with the discrete Fourier transform (DFT) applied to uniformly sampled data. The characterization of these NUS-induced artifacts allows for more informed sample schedule design and improved spectral quality. The DFT–Convolution Theorem, via the point-spread function (PSF) for a given sampling scheme, provides a useful framework for exploring the nature of NUS sampling artifacts. In this work, we analyze the PSFs for a set of specially constructed NUS schemes to quantify the interplay between randomization and dimensionality for reducing artifacts relative to uniformly undersampled controls. In particular, we find a synergistic relationship between the indirect time dimensions and the “quadrature phase dimension” (i.e. the hypercomplex components collected for quadrature detection). The quadrature phase dimension provides additional degrees of freedom that enable partial-component NUS (collecting a subset of quadrature components) to further reduce sampling-induced aliases relative to traditional full-component NUS (collecting all quadrature components). The efficacy of artifact reduction is exponentially related to the dimensionality of the sample space. Our results quantify the utility of partial-component NUS as an additional means for introducing decoherence into sampling schemes and reducing sampling artifacts in high dimensional experiments. PMID:25899289

  10. Comparison between the adsorption behaviors of an organic cation and an organic anion on several reversed-phase liquid chromatography adsorbents.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2004-09-01

    Adsorption data of an organic cation (propranololium chloride) and an organic anion (sodium 1-naphthalene sulfonate) were measured by frontal analysis on two RPLC adsorbents, Symmetry-C18 and XTerra-C18, with aqueous solutions of methanol as the mobile phases. The influence of supporting neutral salts on the adsorption behavior of these two ions are compared. The Henry constants are close (H approximately 5). The four sets of isotherm data are all well accounted for using the bi-Moreau model. However, the isotherms of the two ions behave differently at high concentrations. The initial behaviors of all the isotherms are antilangmuirian but remain so in a much wider concentration range for the cation than for the anion, due to its stronger adsorbate-adsorbate interactions on the low-energy adsorption sites. The retention times of both ions increase with increasing concentration of neutral salt in the mobile phase, suggesting the formation of ion-pair complexes, with Cl- for the cation and with Na+ for the anion. The adsorbate-adsorbate interactions vanish in the presence of salt and the bi-Moreau isotherm model tends toward a bi-Langmuir model. Differences in adsorption behavior are also observed between the cation and the anion when bivalent inorganic anions and cations, respectively, are dissolved in the mobile phase. High concentration band profiles of 1-naphthalene sulfonic acid are langmuirian, except in the presence of a trivalent cation, while those of propranolol are antilangmuirian under certain conditions even with uni- or divalent cations. PMID:15453413

  11. Adsorbent phosphates

    NASA Technical Reports Server (NTRS)

    Watanabe, S.

    1983-01-01

    An adsorbent which uses as its primary ingredient phosphoric acid salts of zirconium or titanium is presented. Production methods are discussed and several examples are detailed. Measurements of separating characteristics of some gases using the salts are given.

  12. An investigation of catalytic active phase-support interactions by IR, NMR and x-ray absorption spectroscopies

    SciTech Connect

    Haller, G.L.

    1992-09-01

    Active catalytic phases (metal, mixed metals, oxide or mixed oxides) interacting with oxide support on which the active phase is dispersed can affect the percentage exposed, the morphology of supported particles, the degree of reducibility of cations, etc., in a variety of ways. Our objective is to characterize the physical chemistry of the active phase-oxide support interaction by spectroscopic methods and to correlate this structure with catalytic function. Two catalytic systems and their associated techniques (x-ray absorption and NMR) are discussed in this progress report. Firstly, the interaction of Pt-Ni supported on silica and L-zeolite are characterized and compared by x-ray absorption spectroscopy (EXAFS). Secondly, we present both experimental and calculational developments of NMR for the investigation of amorphous silica-alumina catalysts and/or supports.

  13. Roles of chemically inequivalent N(CH3)4 ions in phase transition temperatures in [N(CH3)4]2CoCl4 by single-crystal NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2014-06-01

    The temperature dependences of the 1H and 13C spin-lattice relaxation time in the laboratory frame, T1, and in the rotating frame, T1ρ, in [N(CH3)4]2CoCl4 were measured by static nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR. In the ferroelastic phase, 1H T1ρ underwent molecular motion according to the Bloembergen-Purcell-Pound theory. Two inequivalent ions, a-N(CH3)4 and b-N(CH3)4, were identified by 13C cross polarization (CP)/MAS NMR. On the basis of the 13C NMR results, the existence of two chemically inequivalent a-N(CH3)4 and b-N(CH3)4 ions in the ferroelectric phase and the existence of the ferroelastic twin structure of the N(CH3)4 ions in the ferroelastic phase were discussed.

  14. Hexagonal boron nitride nanosheets as adsorbents for solid-phase extraction of polychlorinated biphenyls from water samples.

    PubMed

    Jia, Shiliang; Wang, Zhenhua; Ding, Ning; Elaine Wong, Y-L; Chen, Xiangfeng; Qiu, Guangyu; Dominic Chan, T-W

    2016-09-14

    The adsorptive potential of hexagonal boron nitride nanosheets (h-BNNSs) for solid-phase extraction (SPE) of pollutants was investigated for the first time. Seven indicators of polychlorinated biphenyls (PCBs) were selected as target analytes. The adsorption of PCBs on the surface of the h-BNNSs in water was simulated by the density functional theory and molecular dynamics. The simulation results indicated that the PCBs are adsorbed on the surface by π-π, hydrophobic, and electrostatic interactions. The PCBs were extracted with an h-BNNS-packed SPE cartridge, and eluted by dichloromethane. Gas chromatography-tandem mass spectrometry working in the multiple reaction monitor mode was used for the sample quantification. The effect of extraction parameters, including the flow rate, pH value, breakthrough volume, and the ionic strength, were investigated. Under the optimal working conditions, the developed method showed low limits of detection (0.24-0.50 ng L(-1); signal-to-noise ratio = 3:1), low limits of quantification (0.79-1.56 ng L(-1); signal-to-noise ratio = 10:1), satisfactory linearity (r > 0.99) within the concentration range of 2-1000 ng L(-1), and good precision (relative standard deviation < 12%). The PCBs concentration in environmental water samples was determined by the developed method. This results demonstrate that h-BNNSs have high analytical potential in the enrichment of pollutants. PMID:27566347

  15. Solid-phase microextraction of phthalate esters in water sample using different activated carbon-polymer monoliths as adsorbents.

    PubMed

    Lirio, Stephen; Fu, Chung-Wei; Lin, Jhih-Yun; Hsu, Meng-Ju; Huang, Hsi-Ya

    2016-07-13

    In this study, the application of different activated carbon-polymer (AC-polymer) monoliths as adsorbents for the solid-phase microextraction (SPME) of phthalate esters (PAEs) in water sample were investigated. The activated carbon (AC) was embedded in organic polymers, poly(butyl methacrylate-co-ethylene dimethacrylate) (poly(BMA-EDMA)) or poly(styrene-co-divinylbenzene) (poly(STY-DVB)), via a 5-min microwave-assisted or a 15-min water bath heating polymerization. Preliminary investigation on the performance of the native poly(BMA-EDMA) and poly(STY-DVB) demonstrated remarkable adsorption efficiencies for PAEs. However, due to the strong hydrophobic, π-π, and hydrogen bonding interactions between the analytes and polymers, low extraction recoveries were achieved. In contrast, the presence of AC in native polymers not only enhanced the adsorption efficiencies but also assisted the PAE desorption, especially for AC-poly(STY-DVB) with extraction recovery ranged of 76.2-99.3%. Under the optimized conditions, the extraction recoveries for intra-, inter-day and column-to-column were in the range of 76.5-100.8% (<3.7% RSDs), 77.2-97.6% (<5.6% RSDs) and 75.5-99.7% (<6.2% RSDs), respectively. The developed AC-poly(STY-DVB) monolithic column showed good mechanical stability, which can be reused for more than 30 extraction times without any significant loss in the extraction recoveries of PAEs. The AC-poly(STY-DVB) monolithic column was successfully applied in SPME of PAEs in water sample with extraction recovery ranged of 78.8%-104.6% (<5.5% RSDs). PMID:27237837

  16. Ozonation of chlortetracycline in the aqueous phase: Degradation intermediates and pathway confirmed by NMR.

    PubMed

    Khan, M Hammad; Jung, Jin-Young

    2016-06-01

    Chlortetracycline (CTC) degradation mechanism in aqueous phase ozonation was evaluated for degradation mechanism and its correlation with the biodegradability and mineralization. CTC was removed within 8 and 4 min of ozonation at pH 2.2 and 7.0, respectively. At pH 2.2, HPLC-triple quadrupole mass spectrometry (MS) detected 30 products. The structures for some of these products were proposed on the basis of ozonation chemistry, CTC structure and MS data; these structures were then confirmed by nuclear magnetic resonance (NMR) spectra. Double bond cleavages, dimethyl amino group oxidation, opening and removal of the aromatic ring and dechlorination, mostly direct ozonation reactions, gave products with molecular weights (m.w.) 494, 510, 524, 495 and 413, respectively. Subsequent degradations gave products with m.w. 449, 465, 463 and 415. These products were arranged into a degradation pathway. At pH 7.0, the rate of reaction was increased, though the detected products were similar. Direct ozonation at pH 2.2 increased the biodegradability by altering the structures of CTC and its products. Nevertheless, direct ozonation alone remained insufficient for the mineralization, which was efficient at pH 7.0 due to the production of free radicals. PMID:26963235

  17. Metabolomics-Based Study of Logarithmic and Stationary Phases of Promastigotes in Leishmania major by 1H NMR Spectroscopy

    PubMed Central

    Arjmand, Mohammad; Madrakian, Azadeh; Khalili, Ghader; Najafi, Ali; Zamani, Zahra; Akbari, Ziba

    2016-01-01

    Background: Cutaneous leishmaniasis is one of the most important parasitic diseases in humans. In this disease, one of the responsible organisms is Leishmania major, which is transmitted by sandfly vector. There are specific differences in biochemical profiles and metabolite pathways in logarithmic and stationary phases of Leishmania parasites. In the present study, 1H NMR spectroscopy was used to examine the metabolites outliers in the logarithmic and stationary phases of promastigotes in L. major to enlighten more about the transmission mechanism in metacyclogenesis of L. major. Methods: Promastigote was cultured, logarithmic and stationary phases were separated by the peanut agglutinin, and cell metabolites were extracted. 1H NMR spectroscopy was applied, and outliers were analyzed using principal component analysis. Results: The most altered metabolites in stationary and logarithmic phases were limited to citraconic acid, isopropylmalic acid, L-leucine, ornithine, caprylic acid, capric acid, and acetic acid. Conclusion: 1H NMR spectroscopy could play an important role in the characterization of metabolites in biochemical pathways during a metacyclogenesis process. These metabolites and their pathways can help in exploiting a transmission mechanism in metacyclogenesis, and outcoming data might be used in the metabolic network reconstruction of L. major modeling. PMID:26592771

  18. Evaluation of eggshell membrane-based bio-adsorbent for solid-phase extraction of linear alkylbenzene sulfonates coupled with high-performance liquid chromatography.

    PubMed

    Wang, Weidong; Chen, Bo; Huang, Yuming; Cao, Jia

    2010-09-01

    The potential of eggshell membrane (ESM) as a novel solid-phase extraction bio-adsorbent was investigated in the present study. The ESM with a unique structure of intricate lattice network showed a predominant ability to capture linear alkylbenzene sulfonates (LAS) as a model of organic pollutants by the hydrophobic interactions between ESM and LAS molecular at pH very close to the isoelectric point of ESM, which was similar to the most widely used trapping mechanism for SPE. Under the optimal conditions, the breakthrough capacities of the ESM packed cartridge for C10-C13 LAS homologues were found to be 30, 53, 50, and 43microgg(-1), respectively. On the basis of high-performance liquid chromatography separation and UV detection of LAS homologues, the proposed system could respond down to 0.027ngmL(-1) of LAS with a linear calibration range from 0.2 to 100ngmL(-1), showing a good LAS enrichment ability of eggshell membrane biomaterial with high sensitivity, and could be successfully used for the detection of residual LAS in environmental water samples. The reproducibility among columns was satisfactory (RSD among columns is less than 10%). A comparison study with ESM, C8 and C18 as adsorbents for LAS demonstrated that ESM-based bio-adsorbent was advantageous over C8 and C18, the widely used traditional adsorbents. PMID:20674925

  19. EASY-GOING DUMBO on-spectrometer optimisation of phase modulated homonuclear decoupling sequences in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Grimminck, Dennis L. A. G.; Vasa, Suresh K.; Meerts, W. Leo; Kentgens, Arno P. M.; Brinkmann, Andreas

    2011-06-01

    A one-step many-parameter optimisation scheme for phase modulated proton homonuclear decoupling sequences in solid-state NMR is presented. Phase modulations, parameterised by DUMBO Fourier coefficients, were optimised using a Covariance Matrix Adaptation Evolution Strategies algorithm. Our method, denoted EASY-GOING DUMBO, starts with featureless spectra and optimises proton-proton decoupling, during either proton or carbon signal detection. Optimisations at moderate sample magic angle spinning (MAS) frequencies and medium radio-frequency (rf) field strengths resulted in solutions closely resembling (e)DUMBO. Application of EASY-GOING DUMBO for optimisation at very high 680 kHz rf field strength, 12.5 kHz MAS on a 400 MHz NMR spectrometer resulted in a new solution, with competitively resolved proton spectra.

  20. Vibrational spectra of CO adsorbed on oxide thin films: A tool to probe the surface defects and phase changes of oxide thin films

    SciTech Connect

    Savara, Aditya

    2014-03-15

    Thin films of iron oxide were grown on Pt(111) single crystals using cycles of physical vapor deposition of iron followed by oxidative annealing in an ultrahigh vacuum apparatus. Two procedures were utilized for film growth of ∼15–30 ML thick films, where both procedures involved sequential deposition+oxidation cycles. In procedure 1, the iron oxide film was fully grown via sequential deposition+oxidation cycles, and then the fully grown film was exposed to a CO flux equivalent to 8 × 10{sup −7} millibars, and a vibrational spectrum of adsorbed CO was obtained using infrared reflection-absorption spectroscopy. The vibrational spectra of adsorbed CO from multiple preparations using procedure 1 show changes in the film termination structure and/or chemical nature of the surface defects—some of which are correlated with another phase that forms (“phase B”), even before enough of phase B has formed to be easily detected using low energy electron diffraction (LEED). During procedure 2, CO vibrational spectra were obtained between deposition+oxidation cycles, and these spectra show that the film termination structure and/or chemical nature of the surface defects changed as a function of sequential deposition+oxidation cycles. The authors conclude that measurement of vibrational spectra of adsorbed CO on oxide thin films provides a sensitive tool to probe chemical changes of defects on the surface and can thus complement LEED techniques by probing changes not visible by LEED. Increased use of vibrational spectra of adsorbed CO on thin films would enable better comparisons between films grown with different procedures and by different groups.

  1. 1H and 19F NMR studies on molecular motions and phase transitions in solid triethylammonium tetrafluoroborate

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Seki, Riki; Ikeda, Ryuichi; Ishida, Hiroyuki

    1995-02-01

    Measurements by differential thermal analysis and differential scanning calorimetry and of the spin-lattice relaxation time ( T1), the spin-spin relaxation time ( T2), and the second moment ( M2) of 1H and 19F NMR were carried out in the three solid phases of (CH 3CH 2) 3NHBF 4. X-ray powder patterns were taken in the highest-temperature phase (Phase I) existing above 367 K and the room-temperature phase (Phase II) stable between 220 and 367 K. Phase I formed a NaCl-type cubic structure with a = 11.65(3) Å, Z = 4, V = 1581(13) Å3, and Dx = 0.794 g cm -3, and was expected to be an ionic plastic phase. In this phase, the self-diffusion of anions and the isotropic reorientation of cations were observed. Phase II formed a tetragonal structure with a = 12.47(1) and c = 9.47(3) Å, Z = 4, V = 1473(6) Å3, and Dx = 0.852 g cm -3. From the present DSC and NMR results in this phase, the cations and/or anions were considered to be dynamically disordered states. The C3 reorientation of the cation about the NH bond axis was detected and, in addition, the onset of nutation of the cations and local diffusion of the anions was suggested. In the low-temperature phase (Phase III) stable below 219 K, the C3 reorientations of the three methyl groups of cations and the isotropic reorientation of anions were observed. The motional parameters for these modes were evaluated.

  2. sup 13 C NMR spectroscopy of K sub x C sub 60 : Phase separation molecular dynamics, and metallic properties

    SciTech Connect

    Tycko, R.; Dabbagh, G.; Rosseinsky, M.J.; Murphy, D.W.; Fleming, R.M.; Ramirez, A.P.; Tully, J.C. )

    1991-08-23

    The results of C nuclear magnetic resonance (NMR) measurements on alkali fullerides K{sub x}C{sub 60} are reported. The NMR spectra demonstrate that material with 0 < x < 3 is in fact a two-phase system at equilibrium, with x = 0 and x = 3. NMR lineshapes indicate that C{sup 3{minus}}{sub 60} ions rotate rapidly in the K{sub 3}C{sub 60} phase at 300 K, while C{sub 60}{sup 6{minus}} ions in the insulating K{sub 6}C{sub 60} phase are static on the time scale of the lineshape measurement. The temperature dependence of the C spin-lattice relaxation rate in the normal state of K{sub 3}C{sub 60} is found to be characteristic of a metal, indicating the important role of the C{sub 60}{sup 3{minus}} ions in the conductivity. From the relaxation measurements, an estimate of the density of electronic states at the Fermi level is derived.

  3. Fabrication of a novel hydrophobic/ion-exchange mixed-mode adsorbent for the dispersive solid-phase extraction of chlorophenols from environmental water samples.

    PubMed

    Gao, Li; Wei, Yinmao

    2016-08-01

    A novel mixed-mode adsorbent was prepared by functionalizing silica with tris(2-aminoethyl)amine and 3-phenoxybenzaldehyde as the main mixed-mode scaffold due to the presence of the plentiful amino groups and benzene rings in their molecules. The adsorption mechanism was probed with acidic, natural and basic compounds, and the mixed hydrophobic and ion-exchange interactions were found to be responsible for the adsorption of analytes. The suitability of dispersive solid-phase extraction was demonstrated in the determination of chlorophenols in environmental water. Several parameters, including sample pH, desorption solvent, ionic strength, adsorbent dose, and extraction time were optimized. Under the optimal extraction conditions, the proposed dispersive solid-phase extraction coupled with high-performance liquid chromatography showed good linearity range and acceptable limits of detection (0.22∽0.54 ng/mL) for five chlorophenols. Notably, the higher extraction recoveries (88.7∽109.7%) for five chlorophenols were obtained with smaller adsorbent dose (10 mg) and shorter extraction time (15 min) compared with the reported methods. The proposed method might be potentially applied in the determination of trace chlorophenols in real water samples. PMID:27420911

  4. New insights into phase distribution, phase composition and disorder in Y2(Zr,Sn)2O7 ceramics from NMR spectroscopy.

    PubMed

    Ashbrook, Sharon E; Mitchell, Martin R; Sneddon, Scott; Moran, Robert F; de los Reyes, Massey; Lumpkin, Gregory R; Whittle, Karl R

    2015-04-14

    A combination of (89)Y and (119)Sn NMR spectroscopy and DFT calculations are used to investigate phase evolution, local structure and disorder in Y2Zr2-xSnxO7 ceramics, where a phase change is predicted, from pyrochlore to defect fluorite, with increasing Zr content. The ability of NMR to effectively probe materials that exhibit positional and compositional disorder provides insight into the atomic-scale structure in both ordered and disordered phases and, by exploiting the quantitative nature of the technique, we are able to determine detailed information on the composition of the phase(s) present and the average coordination number (and next-nearest neighbour environment) of the cations. In contrast to previous studies, a more complex picture of the phase variation with composition emerges, with single-phase pyrochlore found only for the Sn end member, and a single defect fluorite phase only for x = 0 to 0.6. A broad two-phase region is observed, from x = 1.8 to 0.8, but the two phases present have very different composition, with a maximum of 13% Zr incorporated into the pyrochlore phase, whereas the composition of the defect fluorite phase varies throughout. Preferential ordering of the anion vacancies in the defect fluorite phase is observed, with Sn only ever found in a six-coordinate environment, while remaining vacancies are shown to be more likely to be associated with Zr than Y. Our findings are then discussed in the light of those from previous studies, many of which utilize diffraction-based approaches, where, in most cases, a single phase of fixed composition has been assumed for the refinement procedure. The significant and surprising differences encountered demonstrate the need for complementary approaches to be considered for a detailed and accurate picture of both the long- and short-range structure of a solid to be achieved. PMID:25754713

  5. Final Report: DoE SBIR Phase 2 Low-Cost Small Diameter NMR Technologies for In-Situ Subsurface Characterization and Monitoring

    SciTech Connect

    Walsh, David Oliver

    2010-09-03

    In this Phase 2 SBIR program, Vista Clara successfully developed and field-tested small diameter NNR logging tools for subsurface characterization and monitoring. This effort involved the design and development surface electronics, a winch with 470ft cable, and three interchangeable downhole probes: a 3.5â diameter borehole NMR probe, a 1.67â diameter borehole NMR probe, and a 2.5â diameter NMR probe that can be deployed using a Geoprobe direct push machine. The 3.5â probe was tested extensively over a 6 week period including 4â to 8â boreholes in Washington, Idaho, Nebraska, Colorado, Kansas, Connecticut and Massachusetts. The field test campaign was highly successful. The 1.67â probe was assembled, tested and calibrated in the laboratory. The 2.5â Geoprobe probe is in final assembly and testing at the time of this report. The completed Phase 2 R&D program has resulted in the first NMR logging tool that can be deployed in boreholes of 4â diameter, the first NMR logging tool that can be deployed in boreholes on 2â diameter, and the first NMR logging tool that can be deployed by a direct push machine. These small diameter tools make NMR logging technically and economically feasible, for the first time. Previously available NMR logging tools were developed for oilfield applications and are prohibitively large and expensive for the majority of near surface groundwater characterization problems.

  6. Study of chemically inequivalent N(CH3)4 ions in [N(CH3)4]2ZnBr4 near the phase transition temperature using 1H MAS NMR, 13C CP/MAS NMR, and 14N NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2016-02-01

    The temperature dependences of the chemical shifts and intensities of 1H, 13C, and 14N nuclei in tetramethylammonium tetrabromozincate, [N(CH3)4]2ZnBr4, were investigated using single-crystal nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR spectroscopy to elucidate the structural geometry near the phase transition temperature. Based on the analysis of the 13C cross-polarization (CP)/MAS NMR and 14N NMR spectra, the two chemically inequivalent N(1) (CH3)4 and N(2) (CH3)4 ions were distinguished. Furthermore, the 14N NMR spectrum at the phase transition temperature indicated the existence of the ferroelastic characteristics of the N(CH3)4 ions.

  7. Liquid phase adsorptions of Rhodamine B dye onto raw and chitosan supported mesoporous adsorbents: isotherms and kinetics studies

    NASA Astrophysics Data System (ADS)

    Inyinbor, A. A.; Adekola, F. A.; Olatunji, G. A.

    2016-04-01

    Irvingia gabonensis endocarp waste was charred (DNc) and subsequently coated with chitosan (CCDNc). Physicochemical characteristics of the two adsorbents were established, while Fourier transform infrared (FTIR), Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area methods were further employed for characterization. Efficiencies of the prepared adsorbents in the uptake of Rhodamine B (RhB) from aqueous effluent were investigated and adsorption data were tested using four isotherms and four kinetics models. The BET surface areas of the prepared adsorbent were 0.0092 and 4.99 m2/g for DNc and CCDNc, respectively, and maximum adsorption was recorded at pH between 3 and 4, respectively. While monolayer adsorption dominates the uptake of RhB onto DNc, uptake of RhB onto CCDNc was onto heterogeneous surface. The maximum monolayer adsorption capacities (q max) obtained from the Langmuir equation are 52.90 and 217.39 mg/g for DNc and CCDNc, respectively. Pseudo second order and Elovich kinetic models well described the kinetics of the two adsorption processes. The mean sorption energy (E) calculated from the D-R model and desorption efficiencies suggests that while the uptake of RhB onto DNc was physical in nature, for RhB-CCDNc system chemisorption dominates.

  8. Eggshell membrane-based biotemplating of mixed hemimicelle/admicelle as a solid-phase extraction adsorbent for carcinogenic polycyclic aromatic hydrocarbons.

    PubMed

    Wang, Weidong; Chen, Bo; Huang, Yuming

    2014-08-13

    A new solid-phase extraction (SPE) format was demonstrated, based on eggshell membrane (ESM) templating of the mixed hemimicelle/admicelle of linear alkylbenzenesulfonates (LAS) as an adsorbent for the enrichment of carcinogenic polycyclic aromatic hydrocarbons (PAHs) in environmental aqueous samples. The LAS mixed hemimicelle/admicelle formation and SPE of the target PAHs were conducted simultaneously by adding the organic target and LAS through a column filled with 500 mg of ESM. The effect of various factors, including LAS concentration, solution pH, ionic strength, and humic acid concentration on the recoveries of PAHs were investigated and optimized. The results showed that LAS concentration and solution pH had obvious effect on extraction of PAHs, and the recoveries of PAHs compounds decreased in the presence of salt and humic acid. Under the optimized analytical conditions, the present method could respond down to 0.1-8.6 ng/L PAHs with a linear calibration ranging from 0.02 to 10 μg/L, showing a good PAHs enrichment ability with high sensitivity. The developed method was used satisfactorily for the detection of PAHs in environmental water samples. The mixed hemimicelle/admicelle adsorbent exhibited high extraction efficiency to PAHs and good selectivity with respect to natural organic matter and was advantageous over commercial C₁₈ adsorbent, for example, high extraction yield, high breakthrough volume, and easy regeneration. PMID:25025712

  9. Phase behavior and 13C NMR spectroscopic analysis of the mixed methane + ethane + propane hydrates in mesoporous silica gels.

    PubMed

    Lee, Seungmin; Cha, Inuk; Seo, Yongwon

    2010-11-25

    In this study, the phase behavior and quantitative determination of hydrate composition and cage occupancy for the mixed CH(4) + C(2)H(6) + C(3)H(8) hydrates were closely investigated through the experimental measurement of three-phase hydrate (H)-water-rich liquid (L(W))-vapor (V) equilibria and (13)C NMR spectra. To examine the effect of pore size and salinity, we measured hydrate phase equilibria for the quaternary CH(4) (90%) + C(2)H(6) (7%) + C(3)H(8) (3%) + water mixtures in silica gel pores of nominal diameters of 6.0, 15.0, and 30.0 nm and for the quinary CH(4) (90%) + C(2)H(6) (7%) + C(3)H(8) (3%) + NaCl + water mixtures of two different NaCl concentrations (3 and 10 wt %) in silica gel pores of a nominal 30.0 nm diameter. The value of hydrate-water interfacial tension for the CH(4) (90%) + C(2)H(6) (7%) + C(3)H(8) (3%) hydrate was found to be 47 ± 4 mJ/m(2) from the relation of the dissociation temperature depression with the pore size of silica gels at a given pressure. At a specified temperature, three-phase H-L(W)-V equilibrium curves of pore hydrates were shifted to higher pressure regions depending on pore sizes and NaCl concentrations. From the cage-dependent (13)C NMR chemical shifts of enclathrated guest molecules, the mixed CH(4) (90%) + C(2)H(6) (7%) + C(3)H(8) (3%) gas hydrate was confirmed to be structure II. The cage occupancies of each guest molecule and the hydration number of the mixed gas hydrates were also estimated from the (13)C NMR spectra. PMID:20964277

  10. Scalable synthesis of quaterrylene: solution-phase 1H NMR spectroscopy of its oxidative dication.

    PubMed

    Thamatam, Rajesh; Skraba, Sarah L; Johnson, Richard P

    2013-10-14

    Quaterrylene is prepared in a single reaction and high yield by Scholl-type coupling of perylene, utilizing trifluoromethanesulfonic acid as catalyst and DDQ or molecular oxygen as oxidant. Dissolution in 1 M triflic acid/dichloroethane with sonication yields the aromatic quaterrylene oxidative dication, which is characterized by its (1)H NMR spectrum. PMID:23999880

  11. Microwave distillation-solid phase adsorbent trapping device for the determination of off-flavors, geosmin and methylisoborneol, in catfish tissue below their rejection levels

    SciTech Connect

    Conte, E.D.; Shen, C.Y.; Miller, D.W.; Perschbacher, P.W.

    1996-08-01

    Described is a rapid microwave-mediated steam distillation device for determining two predominant off-flavor compounds, geosmin and methylisoborneol, in catfish tissue. A microwave on-time of 10 min is needed to efficiently remove these off-flavor compounds from the sample matrix and trap them on a solid phase adsorbent. A minimal amount of organic solvent is used to elute the trapped compounds. The extract is then analyzed by gas chromatography with ion trap detection in the selective ion storage mode. Detection limits in the sub-parts-per-billion range are obtained with this method. 11 refs., 5 figs., 1 tab.

  12. Optically polarized {sup 129}Xe NMR investigation of carbon nanotubes

    SciTech Connect

    Clewett, Catherine F. M.; Morgan, Steven W.; Saam, Brian; Pietrass, Tanja

    2008-12-15

    We demonstrate the utility of optically polarized {sup 129}Xe NMR in a convection cell for measuring the surface properties of materials. In particular, we show adsorption of xenon gas on oxidatively purified single- and multiwalled carbon nanotubes. The interaction between xenon and multiwalled nanotubes produced by chemical vapor deposition was stronger than that of single- or multiwalled nanotubes produced by carbon arc discharge. Xenon was observed in gas, liquid, and adsorbed phases. The large polarization and moderate pressures of xenon ({approx}0.2 MPa) allowed resolution of multiple lines in both the gas and condensed phases of xenon in contact with carbon nanotubes. Xe gas exchanges with physisorbed xenon in two different environments. Xe adsorbs preferentially on defects, but if the number of defects is not sufficient, it will also adsorb on surface and interstitial sites. Penetration of Xe in the tube interior was not observed.

  13. Changes in porosity and organic matter phase distribution monitored by NMR relaxometry following hydrous pyrolysis under uniaxial confinement

    USGS Publications Warehouse

    Washburn, Kathryn E.; Birdwell, Justin E.; Lewan, Michael D.; Miller, Michael

    2013-01-01

    Artificial maturation methods are used to induce changes in source rock thermal maturity without the uncertainties that arise when comparing natural samples from a particular basin that often represent different levels of maturation and different lithofacies. A novel uniaxial confinement clamp was used on Woodford Shale cores in hydrous pyrolysis experiments to limit sample expansion by simulating the effect of overburden present during thermal maturation in natural systems. These samples were then subjected to X-ray computed tomography (X-CT) imaging and low-field nuclear magnetic resonance (LF-NMR) relaxometry measurements. LF-NMR relaxometry is a noninvasive technique commonly used to measure porosity and pore-size distributions in fluid-filled porous media, but may also measure hydrogen present in hydrogen-bearing organic solids. Standard T1 and T2 relaxation distributions were determined and two dimensional T1-T2 correlation measurements were performed on the Woodford Shale cores. The T1-T2 correlations facilitate resolution of organic phases in the system. The changes observed in NMR-relaxation times correspond to bitumen and lighter hydrocarbon production that occur as source rock organic matter matures. The LF-NMR porosities of the core samples at maximum oil generation are significantly higher than porosities measured by other methods. This discrepancy likely arises from the measurement of highly viscous organic constituents in addition to fluid-filled porosity. An unconfined sample showed shorter relaxation times and lower porosity. This difference is attributed to the lack of fractures observed in the unconfined sample by X-CT.

  14. Schiff base - Chitosan grafted L-monoguluronic acid as a novel solid-phase adsorbent for removal of congo red.

    PubMed

    Yuan, Bo; Qiu, Li-Gan; Su, Hong-Zhen; Cao, Cheng-Liang; Jiang, Ji-Hong

    2016-01-01

    A novel modified chitosan adsorbent (GL-SBCS) was synthesized by covalently grafting a Schiff base-chitosan (SBCS) onto the surface of l-monoguluronic acid. Physico-chemical investigation on the adsorption of congo red, an anionic azo dye by GL-SBCS has been carried out. The effect of different weight contents of chitosan in GL-SBCS composite, adsorbent dosage, initial pH and contract time were studied in detail using batch adsorption. Results showed that GL-SBCS exhibited better than normal CS and l-monoguluronic acid. Further investigation demonstrated that the adsorption pattern fitted well with the Langmuir model (R(2)>0.99) but less-satisfied the Freundlich model. Both ionic interaction as well as physical forces is responsible for binding of congo red with GL-SBCS as determined by zeta potential measurement Both sodium chloride and sodium dodecyl sulfate significantly influenced the adsorption process. SBCS would be a good method and resource to increase absorption efficiency for the removal of anionic dyes in a wastewater treatment process. PMID:26432372

  15. Tribochemical polymerization of adsorbed n-pentanol on SiO2 during rubbing: when does it occur and is it responsible for effective vapor phase lubrication?

    PubMed

    Barnette, Anna L; Asay, David B; Ohlhausen, James A; Dugger, Michael T; Kim, Seong H

    2010-11-01

    The origin and role of tribochemical reaction products formed while sliding silicon oxide surfaces in the presence of adsorbed alcohol molecules in equilibrium with the vapor phase were studied. Wear and friction coefficient studies with varying contact loads and n-pentanol vapor environments were used to determine under what operating conditions the tribochemical reaction species was produced. Imaging time-of-flight secondary ion mass spectrometry and microinfrared spectroscopy found that hydrocarbon species with a molecular weight higher than the starting vapor molecules are produced when there is wear of the SiO(2) surface. When the n-pentanol vapor lubrication is effective and the silicon oxide surface does not wear, then the tribochemical polymerization products are negligible. These results imply that the tribochemical polymerization is associated with the substrate wear process occurring due to insufficient adsorbate supply or high mechanical load. The tribochemical reactions do not seem to be the primary lubrication mechanism for vapor phase lubrication of SiO(2) surfaces with alcohol, although they may lubricate the substrate momentarily upon failure of the alcohol vapor delivery to the sliding contact. PMID:20735117

  16. Incorporation of phosphorus guest ions in the calcium silicate phases of Portland cement from 31P MAS NMR spectroscopy.

    PubMed

    Poulsen, Søren L; Jakobsen, Hans J; Skibsted, Jørgen

    2010-06-21

    Portland cements may contain small quantities of phosphorus (typically below 0.5 wt % P(2)O(5)), originating from either the raw materials or alternative sources of fuel used to heat the cement kilns. This work reports the first (31)P MAS NMR study of anhydrous and hydrated Portland cements that focuses on the phase and site preferences of the (PO(4))(3-) guest ions in the main clinker phases and hydration products. The observed (31)P chemical shifts (10 to -2 ppm), the (31)P chemical shift anisotropy, and the resemblance of the lineshapes in the (31)P and (29)Si MAS NMR spectra strongly suggest that (PO(4))(3-) units are incorporated in the calcium silicate phases, alite (Ca(3)SiO(5)) and belite (Ca(2)SiO(4)), by substitution for (SiO(4))(4-) tetrahedra. This assignment is further supported by a determination of the spin-lattice relaxation times for (31)P in alite and belite, which exhibit the same ratio as observed for the corresponding (29)Si relaxation times. From simulations of the intensities, observed in inversion-recovery spectra for a white Portland cement, it is deduced that 1.3% and 2.1% of the Si sites in alite and belite, respectively, are replaced by phosphorus. Charge balance may potentially be achieved to some extent by a coupled substitution mechanism where Ca(2+) is replaced by Fe(3+) ions, which may account for the interaction of the (31)P spins with paramagnetic Fe(3+) ions as observed for the ordinary Portland cements. A minor fraction of phosphorus may also be present in the separate phase Ca(3)(PO(4))(2), as indicated by the observation of a narrow resonance at delta((31)P) = 3.0 ppm for two of the studied cements. (31)P{(1)H} CP/MAS NMR spectra following the hydration of a white Portland cement show that the resonances from the hydrous phosphate species fall in the same spectral range as observed for (PO(4))(3-) incorporated in alite. This similarity and the absence of a large (31)P chemical shift ansitropy indicate that the hydrous (PO(4

  17. Effects of non-local exchange on core level shifts for gas-phase and adsorbed molecules

    SciTech Connect

    Van den Bossche, M.; Grönbeck, H.; Martin, N. M.; Gustafson, J.; Lundgren, E.; Hakanoglu, C.; Weaver, J. F.

    2014-07-21

    Density functional theory calculations are often used to interpret experimental shifts in core level binding energies. Calculations based on gradient-corrected (GC) exchange-correlation functionals are known to reproduce measured core level shifts (CLS) of isolated molecules and metal surfaces with reasonable accuracy. In the present study, we discuss a series of examples where the shifts calculated within a GC-functional significantly deviate from the experimental values, namely the CLS of C 1s in ethyl trifluoroacetate, Pd 3d in PdO and the O 1s shift for CO adsorbed on PdO(101). The deviations are traced to effects of the electronic self-interaction error with GC-functionals and substantially better agreements between calculated and measured CLS are obtained when a fraction of exact exchange is used in the exchange-correlation functional.

  18. Short-Range Order of Mesomorphic Phase of a Semi-crystalline Polymer by Solid-State NMR: Isotactic Polypropylene

    NASA Astrophysics Data System (ADS)

    Yuan, Shichen; Miyoshi, Toshikazu

    2015-03-01

    Mesophase is intermediate phase between crystalline and melt state. Characterization of short-range structures of disordered mesomorphic phase without long-range order is challenging issue in polymer characterization. The short range order was considered same as α or β i PP, or neither. In this work, a new strategy using 13C-13C through space interactions as well as molecular dynamics based on chemical shift anisotropy (CSA) re-orientation is proposed for evaluating short-range order of mesophase of isotactic-polypropylene (iPP). 13C-13C double quantum (DQ) build up curves of 13C 15 percent CH3 selectively labeled iPP and spin dynamics simulations elucidate that local packing structures in mesophase is very close to that in β phase. Moreover, exchange NMR proves that the crystalline chains perform large amplitude motions in all α, β, and mesophase. The correlation time of overall dynamics of stems in mesophase follows the same Arrhenius line with that of β phase but is largely deviated from the Arrhenius line of the α phase. Through the obtained results, it is concluded that short-range order in mesophase is exceedingly close or same to those in β phase. This work was financially supported by the National Science Foundation (Grant No. DMR-1105829) and by UA startup funds.

  19. Easy-Going On-Spectrometer Optimisation of Phase Modulated Homonuclear Decoupling Sequences in Solid-State NMR

    NASA Astrophysics Data System (ADS)

    Grimminck, Dennis L. A. G.; Vasa, Suresh K.; Meerts, W. Leo; Kentgens, P. M.

    2011-06-01

    A global optimisation scheme for phase modulated proton homonuclear decoupling sequences in solid-state NMR is presented. Phase modulations, parameterised by DUMBO Fourier coefficients, were optimized using a Covariance Matrix Adaptation Evolution Strategies algorithm. Our method, denoted EASY-GOING homonuclear decoupling, starts with featureless spectra and optimises proton-proton decoupling, during either proton or carbon signal detection. On the one hand, our solutions closely resemble (e)DUMBO for moderate sample spinning frequencies and medium radio-frequency (rf) field strengths. On the other hand, the EASY-GOING approach resulted in a superior solution, achieving significantly better resolved proton spectra at very high 680 kHz rf field strength. N. Hansen, and A. Ostermeier. Evol. Comput. 9 (2001) 159-195 B. Elena, G. de Paepe, L. Emsley. Chem. Phys. Lett. 398 (2004) 532-538

  20. The (1) H NMR spectrum of pyrazole in a nematic phase.

    PubMed

    Provasi, Patricio; Jimeno, María Luisa; Alkorta, Ibon; Reviriego, Felipe; Elguero, José; Jokisaari, Jukka

    2016-08-01

    The experimental (1) H nuclear magnetic resonance (NMR) spectrum of 1H-pyrazole was recorded in thermotropic nematic liquid crystal N-(p-ethoxybenzylidene)-p-butylaniline (EBBA) within the temperature range of 299-308 K. Two of three observable dipolar DHH -couplings appeared to be equal at each temperature because of fast prototropic tautomerism. Analysis of the Saupe orientational order parameters using fixed geometry determined by computations and experimental dipolar couplings results in a situation in which the molecular orientation relative to the magnetic field (and the liquid crystal director) can be described exceptionally by a single parameter. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26947581

  1. NMR Studies of Novel Electronic Phases in Low Dimensional Molecular Solids at High Pressure and Low Temperature

    NASA Astrophysics Data System (ADS)

    Brown, Stuart

    2013-03-01

    Molecular superconductors are known for anisotropic electronic band structure, correlations, and a sensitivity to mechanical or chemical pressure which acts to control the relative strength of the respective kinetic and potential energies. Modest pressures, of order 1 GPa are commonly used to continuously tune from a Mott insulating ground state to a superconducting state, and NMR has been particularly successful in identifying the orders involved, and the nature of the excitations in the various phases encountered. The family of quasi-two dimensional systems κ-(BEDT-TTF)2X (e.g., X=Cu(NCS)2, Cu[N(CN)2]Cl) includes a line of first order phase transitions separating the Mott and superconducting phases, with the superconducting state exhibiting signatures for line nodes associated with an order parameter sign-change over the Fermi surface. The pressure/temperature phase diagram of the quasi-one dimensional materials (TMTSF)2X, X=PF6, ClO4,...) includes more phases, as a consequence of effective 1/4-filling and a substantial density wave susceptibility. The SC ground state is singlet, and there is evidence for a sign-change of the order parameter over the Fermi surface. The high-conductivity normal state exhibits properties associated with two-dimensional spin fluctuations, with signatures in the relaxation rate, as well as transport that are reminiscent of behaviors observed in other correlated superconductors. Supported by the NSF under grant no. DMR-1105531

  2. Use of ZIF-8-derived nanoporous carbon as the adsorbent for the solid phase extraction of carbamate pesticides prior to high-performance liquid chromatographic analysis.

    PubMed

    Hao, Lin; Liu, Xingli; Wang, Juntao; Wang, Chun; Wu, Qiuhua; Wang, Zhi

    2015-09-01

    In this work, a chemically and thermally robust and highly porous zeolite-type metal-organic framework, zeolitic imidazolate framework-8 (ZIF-8), was used as both a precursor and a template and furfuryl alcohol as a second precursor to synthesize a nanoporous carbon. The prepared ZIF-8-derived nanoporous carbon was used as the solid-phase extraction adsorbent for the extraction of carbamate pesticides from cabbage and water samples. The adsorbed analytes were eluted with acetonitrile for the determination by high performance liquid chromatography-ultraviolet detection. The high surface area, high porosity, good stability and fast adsorption/desorption kinetics of the material enabled it to have a high adsorption capacity and good adsorption performance. Under optimum conditions, good linearity for the analytes in the range of 0.5-100 ng g(-1) and 0.05-20 ng mL(-1) existed for cabbage and water samples with the correlation coefficients of 0.9968-0.9980 and 0.9990-0.9995, respectively. The limits of detection (S/N=3) for the analytes were in the range of 0.25-0.1 ng g(-1) and 0.01-0.02 ng mL(-1) for the cabbage and water samples, respectively. The relative standard deviations (RSDs) for intra-day and the inter-day determinations of the analytes were below 7.0% and 12.5%, respectively. PMID:26003698

  3. Graphene-modified TiO2 nanotube arrays as an adsorbent in micro-solid phase extraction for determination of carbamate pesticides in water samples.

    PubMed

    Zhou, Qingxiang; Fang, Zhi

    2015-04-15

    Graphene is a good adsorbent for organic pollutants, especially for compounds containing benzene rings. When used in TiO2 nanotube arrays for micro-solid phase extraction (μ-SPE), the combination of graphene's strong adsorptive properties with its good separation capabilities results in excellent sample preconcentration performance. In the present study, graphene-modified TiO2 nanotube arrays were prepared by electrodeposition using a cyclic voltammetric reduction method. Four carbamate pesticides, including metolcarb, carbaryl, isoprocarb, and diethofencarb, were used as model analytes to validate the enrichment properties of the prepared adsorbent in μ-SPE. Factors affecting the enrichment efficiency of the μ-SPE procedure were optimized and included sample pH, elution solvents, salting-out effect, adsorption time and desorption time. Under optimal conditions, graphene-modified TiO2 nanotube arrays exhibited excellent enrichment efficiency for carbamate pesticides. The detection limits of these carbamate pesticides ranged from 2.27 to 3.26 μg L(-1). The proposed method was validated using four environmental water samples, and yields of pesticides recovered from spiked test samples of the four analytes were in the range of 83.9-108.8%. These results indicate that graphene-modified TiO2 nanotube arrays exhibit good adsorption to the target pollutants, and the method described in this work could be used as a faster and easier alternative procedure for routine analysis of carbamate pesticides in real water samples. PMID:25818138

  4. Solid phase extraction of chromium(VI) from aqueous solutions by adsorption of its diphenylcarbazide complex on a mixed bed adsorbent (acid activated montmorillonite-silica gel) column.

    PubMed

    Rajesh, N; Mishra, Braja Gopal; Pareek, Pawan Kumar

    2008-02-01

    A novel approach has been developed for the solid phase extraction of chromium(VI) based on the adsorption of its diphenylcarbazide complex on a mixture of acid activated montmorillonite (AAM)-silica gel column. The effect of various parameters such as acidity, stability of the column, sample volume, interfering ions, etc., were studied in detail. The adsorbed complex could be easily eluted using polyethylene glycol-sulfuric acid mixture and the concentration of chromium has been determined using visible spectrophotometry. The calibration graph was linear in the range 0-1microgmL(-1) chromium(VI) with a detection limit of 6microgL(-1). A highest preconcentration factor of 25 could be obtained for 250mL sample volume using glass wool as support for the mixed bed adsorbent. Chromium(VI) could be effectively separated from other ions such as nickel, copper, zinc, chloride, sulfate, nitrate, etc., and the method has been successfully applied to study the recovery of chromium in electroplating waste water and spiked water samples. PMID:17604681

  5. [Analysis of organochlorine pesticides and pyrethroid pesticides in vegetables by gas chromatography-electron capture detection coupled with solid-phase extraction using multiwalled carbon nanotubes as adsorbent].

    PubMed

    Zhao, Haixiang; Jia, Yanxia; Ding, Mingyu; Sun, Dajiang; Zhao, Mengbin

    2011-05-01

    A multi-residue analytical method based on solid-phase extraction (SPE) with multiwalled carbon nanotubes (MWCNTs) as adsorbent was developed. The determination of 6 organochlorine pesticides and 7 pyrethroid pesticides in vegetables (including cucumber, cherry tomato, cabbage, lettuce, purple cabbage, leek, shallot and onion) was carried out by gas chromatography-electron capture detection (GC-ECD). The GC-ECD method used two columns (HP-50 and HP-1) and two ECD detectors. The HP-50 column was used for the analysis and the HP-1 column for validation. The clean-up conditions were optimized. The analytes were extracted by acetonitrile, and the extract was cleaned up by the MWCNTs SPE cartridge. The extract was re-dissolved by hexane, eluted with acetone-hexane (7:3, v/v) from the columns. The recoveries were over 70% for the 11 pesticides in the 13 pesticides. The results indicated that the MWCNTs SPE cartridge was efficient for 8 vegetable samples, because it reduced the contamination of the coloring materials to GC-ECD. The experimental results showed the MWCNTs SPE cartridge can adsorb the coloring materials and the eluant was nearly colorless. PMID:21847981

  6. Solid phase extraction of chromium(VI) from aqueous solutions by adsorption of its diphenylcarbazide complex on a mixed bed adsorbent (acid activated montmorillonite-silica gel) column

    NASA Astrophysics Data System (ADS)

    Rajesh, N.; Mishra, Braja Gopal; Pareek, Pawan Kumar

    2008-02-01

    A novel approach has been developed for the solid phase extraction of chromium(VI) based on the adsorption of its diphenylcarbazide complex on a mixture of acid activated montmorillonite (AAM)-silica gel column. The effect of various parameters such as acidity, stability of the column, sample volume, interfering ions, etc., were studied in detail. The adsorbed complex could be easily eluted using polyethylene glycol-sulfuric acid mixture and the concentration of chromium has been determined using visible spectrophotometry. The calibration graph was linear in the range 0-1 μg mL -1 chromium(VI) with a detection limit of 6 μg L -1. A highest preconcentration factor of 25 could be obtained for 250 mL sample volume using glass wool as support for the mixed bed adsorbent. Chromium(VI) could be effectively separated from other ions such as nickel, copper, zinc, chloride, sulfate, nitrate, etc., and the method has been successfully applied to study the recovery of chromium in electroplating waste water and spiked water samples.

  7. NMR study of hydrogen diffusion and phase determination of the Mg2NiHx system

    NASA Astrophysics Data System (ADS)

    Goren, S. D.; Korn, C.; Mintz, M. H.; Gavra, Z.; Hadari, Z.

    1980-11-01

    We have measured the temperature dependence of the hydrogen spin lattice relaxation time in the hydride (β, β', γ, δ) and solid solution phases of the Mg2NiHx system. These gave the temperature ranges of the various phases. The hydrogen diffusion activation energy for the β, β', γ and δ hydride phases were found to be 10.6±0.4, ?17, 12.0±0.3 and ?20 kcal/mole, respectively, and 8.7±0.7 kcal/mole for the α phase solution.

  8. Quantifying fluid distribution and phase connectivity with a simple 3D cubic pore network model constrained by NMR and MICP data

    NASA Astrophysics Data System (ADS)

    Xu, Chicheng; Torres-Verdín, Carlos

    2013-12-01

    A computer algorithm is implemented to construct 3D cubic pore networks that simultaneously honor nuclear magnetic resonance (NMR) and mercury injection capillary pressure (MICP) measurements on core samples. The algorithm uses discretized pore-body size distributions from NMR and pore-throat size versus incremental pore-volume fraction information from MICP as initial inputs. Both pore-throat radius distribution and body-throat correlation are iteratively refined to match percolation-simulated primary drainage capillary pressure with MICP data. It outputs a pore-throat radius distribution which is not directly measurable with either NMR or MICP. In addition, quasi-static fluid distribution and single-phase connectivity are quantified at each capillary pressure stage. NMR measurements on desaturating core samples are simulated from the quantitative fluid distribution in a gas-displacing-water drainage process and are verified with laboratory measurements. We invoke effective medium theory to quantify the single-phase connectivity in two-phase flow by simulating percolation in equivalent sub-pore-networks that consider the remaining fluid phase as solid cementation. Primary drainage relative permeability curves quantified from fluid distribution and phase connectivity show petrophysical consistency after applying a hydrated-water saturation correction. Core measurements of tight-gas sandstone samples from the Cotton Valley formation, East Texas, are used to verify the new algorithm.

  9. Molecular motions and phase transitions. NMR relaxation times studies of several lecithins.

    PubMed Central

    Bar-Adon, R; Gilboa, H

    1981-01-01

    The spin-lattice relaxation time, T1, and the dipolar energy relaxation time, TD, were measured as a function of temperature. The materials studied were samples of anhydrous L-dipalmitoyl lecithin, DL-dipalmitoyl lecithin, L-dimyristoyl lecithin, DL-dimyristoyl lecithin and their monohydrates, and of anhydrous egg yolk lecithin. It is shown that TD is a much more sensitive parameter than T1 for the determination of the Chapman phase transition. Comparison between T1 and TD provides information about new types of slow molecular motions below and above the phase transition temperature. It is suggested that the relaxation mechanisms for T1 and TD in the gel phase are governed by segmental motion in the phospholipid molecule. A new metastable phase was detected in dimyristoyl lecithin monohydrates. This phase could only be detected from the dipolar energy relaxation times. PMID:7225514

  10. High-Resolution Solid-State NMR Investigation of the Phase Transition in Decamethylferrocene-Acenaphthenequinone Charge-Transfer Complex

    NASA Astrophysics Data System (ADS)

    Nakamura, Hideaki; Kuwahara, Daisuke; Mochida, Tomoyuki

    2009-10-01

    A charge-transfer complex composed of decamethylferrocene (D) and acenaphthenequinone (A) was prepared. The material was a 1:1 neutral complex with a mixed-stack structure and exhibited a phase transition at -16 °C. High-resolution 13C and 1H NMR spectroscopy revealed that an inclination of A with respect to D occurs below the phase-transition temperature. The 1H spin-diffusion rates of the complex undergoing high-speed magic-angle spinning (MAS) were measured to determine the shortest 1H-1H distance r between D and A. To analyze the experimental results, we derived the analytical expression of the spin-diffusion rate Wz for a homonuclear multispin system undergoing MAS. It was found that Wz for the complex is proportional only to 1/r6 under high-speed MAS conditions. On the basis of this relationship and the crystal structure at 20 °C, it was determined that the shortest 1H-1H distance r at -27.7 °C (below the phase transition temperature) is 0.4 Å shorter than that at 20 °C. Given this information, a plausible model of the low-temperature structure is discussed.

  11. Humic acids as both matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and adsorbent for magnetic solid phase extraction.

    PubMed

    Zhao, Qin; Xu, Jing; Yin, Jia; Feng, Yu-Qi

    2015-08-19

    In the present study, humic acids (HAs) were applied as both a matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and an adsorbent of magnetic solid phase extraction (MSPE) for the first time. As natural macromolecule compounds, HAs are inherently highly functionalized and contain laser energy absorbing-transferring aromatic structures. This special molecular structure made HAs a good candidate for use as a MALDI matrix in small molecule analysis. At the same time, due to its good adsorption ability, HAs was prepared as MSPE adsorbent via a simple co-mixing method, in which the commercially available HAs were directly mixed with Fe3O4 magnetic nanoparticles (MNPs) in a mortar and grinded evenly and completely. In this process, MNPs were physically wrapped and adhered to tiny HAs leading to the formation of magnetic HAs (MHAs). To verify the bi-function of the MHAs, Rhodamine B (RdB) was chosen as model compound. Our results show that the combination of MHAs-based MSPE and MALDI-TOF-MS can provide a rapid and sensitive method for the determination of RdB in chili oil. The whole analytical procedure could be completed within 30 min for simultaneous determination of more than 20 samples, and the limit of quantitation for RdB was found to be 0.02 μg/g. The recoveries in chili oil were in the range 73.8-81.5% with the RSDs less than 21.3% (intraday) and 20.3% (interday). The proposed strategy has potential applications for high-throughput analysis of small molecules in complex samples. PMID:26343436

  12. Determination of imidazole derivatives by micellar electrokinetic chromatography combined with solid-phase microextraction using activated carbon-polymer monolith as adsorbent.

    PubMed

    Shih, Yung-Han; Lirio, Stephen; Li, Chih-Keng; Liu, Wan-Ling; Huang, Hsi-Ya

    2016-01-01

    In this study, an effective method for the separation of imidazole derivatives 2-methylimidazole (2-MEI), 4- methylimidazole (4-MEI) and 2-acetyl-4-tetrahydroxybutylimidazole (THI) in caramel colors using cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI-sweeping-MEKC) was developed. The limits of detection (LOD) and quantitation (LOQ) for the CSEI-sweeping-MEKC method were in the range of 4.3-80μgL(-1) and 14-270μgL(-1), respectively. Meanwhile, a rapid fabrication activated carbon-polymer (AC-polymer) monolithic column as adsorbent for solid-phase microextraction (SPME) of imidazole colors was developed. Under the optimized SPME condition, the extraction recoveries for intra-day, inter-day and column-to-column were in the range of 84.5-95.1% (<6.3% RSDs), 85.6-96.1% (<4.9% RSDs), and 81.3-96.1% (<7.1% RSDs), respectively. The LODs and LOQs of AC-polymer monolithic column combined with CSEI-sweeping-MEKC method were in the range of 33.4-60.4μgL(-1) and 111.7-201.2μgL(-1), respectively. The use of AC-polymer as SPME adsorbent demonstrated the reduction of matrix effect in food samples such as soft drink and alcoholic beverage thereby benefiting successful determination of trace-level caramel colors residues using CSEI-sweeping-MEKC method. The developed AC-polymer monolithic column can be reused for more than 30 times without any significant loss in the extraction recovery for imidazole derivatives. PMID:26363948

  13. Minimizing the effects of RF inhomogeneity and phase transients allows resolution of two peaks in the (1)H CRAMPS NMR spectrum of adamantane.

    PubMed

    Brouwer, Darren H; Horvath, Matthew

    2015-10-01

    One of the limiting factors to achieving highly resolved (1)H NMR spectra with (1)H homonuclear decoupling sequences is imperfections in the applied radiofrequency (RF) pulses, most notably phase transients and RF inhomogeneity. Through a series of simulations and solid-state NMR experiments, it is demonstrated that the combined effects of phase transients and RF inhomogeneity can be minimized by a combination of (i) restricting the sample to small volume of the rotor, (ii) by employing a super-cycled version of the DUMBO decoupling sequence, and (iii) by carefully adjusting the probe tuning such that the asymmetric component of phase transients is minimized. Under these optimal conditions, it was possible to clearly resolve two signals in the (1)H CRAMPS NMR spectrum of adamantane arising from the CH and CH2 protons in the molecule. It is proposed that adamantane could be a very useful setup sample for (1)H CRAMPS NMR as the two peaks are only resolved when the effects of RF inhomogeneity and phase transients are minimized. PMID:26483329

  14. Analytical and mechanistic aspects of the room temperature phosphorescence of Erythrosine B adsorbed on solid supports as oxygen sensing phases

    NASA Astrophysics Data System (ADS)

    Velasco-García, Nieves; Pereiro-García, Rosario; Diaz-García, Marta E.

    1995-05-01

    Room temperature phosphorescence (RTP) lifetime measurements and spectra of different concentrations of Erythrosine B immobilized on anion exchangers and non-ionic resins have been employed to unveil mechanistic aspects of the RTP of immobilized Erythrosine B. The existence of a definite number of RTP decaying components in some experimental conditions has been confirmed. The effects of humidified argon and air on RTP lifetimes and the changes in luminescence intensities were used to investigate some of the interactions responsible for the multiple component RTP emission. The experiments performed also proved the suitability of the phases prepared using non-ionic resins, for the quantification of molecular oxygen by RTP-quenching measurements. Moreover, the solid phases with anion-exchanger resins showed good potential for the analytical sensing of humidity.

  15. Effect of phase symmetry on the NMR spectrum of acetonitrile oriented in a uniaxial-biaxial-uniaxial phase

    NASA Astrophysics Data System (ADS)

    Deepak, H. S. Vinay; Yelamaggad, C. V.; Khetrapal, C. L.; Ramanathan, K. V.

    2016-09-01

    We report here the measurement of the Csbnd H and the Hsbnd H dipolar couplings of the methyl group of acetonitrile oriented in the biaxial liquid crystal potassium laurate/1-decanol/water system. These parameters show large variations when measured as a function of temperature. The variations follow the symmetry of the phase as the liquid crystal goes through the sequence of uniaxial - biaxial - uniaxial phases and show a close correspondence to the phase changes that occur in the liquid crystalline solvent coinciding with the onset of biaxiality. The Hsbnd Csbnd H bond angle calculated after incorporating vibrational corrections to the dipolar couplings is discussed in terms of contributions in the case of the biaxial liquid crystal arising from vibration-rotation interaction effects.

  16. Suppression of electron correlations in the collapsed tetragonal phase of CaFe2As2 under ambient pressure demonstrated by As75 NMR/NQR measurements

    SciTech Connect

    Furukawa, Yuji; Roy, Beas; Ran, Sheng; Budko, Sergey L.; Canfield, Paul C.

    2014-03-20

    The static and the dynamic spin correlations in the low-temperature collapsed tetragonal and the high-temperature tetragonal phase in CaFe2As2 have been investigated by As75 nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements. Through the temperature (T) dependence of the nuclear spin lattice relaxation rates (1/T1) and the Knight shifts, although stripe-type antiferromagnetic (AFM) spin correlations are realized in the high-temperature tetragonal phase, no trace of the AFM spin correlations can be found in the nonsuperconducting, low-temperature, collapsed tetragonal (cT) phase. Given that there is no magnetic broadening in As75 NMR spectra, together with the T-independent behavior of magnetic susceptibility χ and the T dependence of 1/T1Tχ, we conclude that Fe spin correlations are completely quenched statically and dynamically in the nonsuperconducting cT phase in CaFe2As2.

  17. Suppression of electron correlations in the collapsed tetragonal phase of CaFe2As2 under ambient pressure demonstrated by As75 NMR/NQR measurements

    NASA Astrophysics Data System (ADS)

    Furukawa, Y.; Roy, B.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.

    2014-03-01

    The static and the dynamic spin correlations in the low-temperature collapsed tetragonal and the high-temperature tetragonal phase in CaFe2As2 have been investigated by As75 nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements. Through the temperature (T) dependence of the nuclear spin lattice relaxation rates (1/T1) and the Knight shifts, although stripe-type antiferromagnetic (AFM) spin correlations are realized in the high-temperature tetragonal phase, no trace of the AFM spin correlations can be found in the nonsuperconducting, low-temperature, collapsed tetragonal (cT) phase. Given that there is no magnetic broadening in As75 NMR spectra, together with the T-independent behavior of magnetic susceptibility χ and the T dependence of 1/T1Tχ, we conclude that Fe spin correlations are completely quenched statically and dynamically in the nonsuperconducting cT phase in CaFe2As2.

  18. Spectrophotometric determination of basic fuchsin from various water samples after vortex assisted solid phase extraction using reduced graphene oxide as an adsorbent.

    PubMed

    Tokalıoğlu, Şerife; Yavuz, Emre; Aslantaş, Ayşe; Şahan, Halil; Taşkın, Ferhat; Patat, Şaban

    2015-10-01

    In this study, a fast and simple vortex assisted solid phase extraction method was developed for the separation/preconcentration of basic fuchsin in various water samples. The determination of basic fuchsin was carried out at a wavelength of 554 nm by spectrophotometry. Reduced graphene oxide which was used as a solid phase extractor was synthesized and characterized by X-ray diffraction, scanning electron microscopy and the Brunauer, Emmett and Teller. The optimum conditions are as follows: pH 2, contact times for adsorption and elution of 30 s and 90 s, respectively, 10 mg adsorbent, and eluent (ethanol) volume of 1 mL. The effects of some interfering ions and dyes were investigated. The method was linear in the concentration range of 50-250 μg L(-1). The adsorption capacity was 34.1 mg g(-1). The preconcentration factor, limit of detection and precision (RSD, %) of the method were found to be 400, 0.07 μg L(-1) and 1.2%, respectively. The described method was validated by analyzing basic fuchsin spiked certified reference material (SPS-WW1 Batch 114-Wastewater) and spiked real water samples. PMID:25974670

  19. [Simultaneous determination of 16 organophosphorous pesticides in vegetables, fruits and tea by gas chromatography coupled with clean-up by mesoporous alumina as solid-phase extraction adsorbent].

    PubMed

    Hu, Yeqin; Xi, Cunxian; Cao, Shurui; Wang, Guomin; Li, Xianliang; Zhang, Lei; Zhang, Yunhuai

    2014-07-01

    A gas chromatographic method based on solid-phase extraction was developed for the simultaneous determination of 16 organophosphorous pesticides in vegetables, fruits and tea, including cabbage, lettuce, pumpkin, onion, tomato, turnip, apple, pear and tea. The samples were extracted with ethyl acetate, and clean-up with mesoporous alumina as solid-phase extraction adsorbent. The separation of target compounds was performed on a DB-1701 capillary column, and the quantitative analysis of the organophosphorous pesticides was carried out by gas chromatography with flame photometric detection. The results showed that the calibration curves of the 16 organophosphorous pesticides were linear in the range of 10-2 000 microg/L with good correlation coefficients (R2 > 0.997). The recoveries of the pesticides in different samples at three spiked levels ranged from 83.2% to 103.8% with the relative standard deviations of 2.0%-9.9%. This method has high sensitivity, high accuracy and good repeatability, and can be applied to the determination of the organophosphorus pesticide residues in vegetables, fruits and tea. PMID:25255574

  20. Geometric quantum gates in liquid-state NMR based on a cancellation of dynamical phases

    NASA Astrophysics Data System (ADS)

    Ota, Yukihiro; Goto, Yoshito; Kondo, Yasushi; Nakahara, Mikio

    2009-11-01

    A proposal for applying nonadiabatic geometric phases to quantum computing, called double-loop method [S.-L. Zhu and Z. D. Wang, Phys. Rev. A 67, 022319 (2003)], is demonstrated in a liquid-state nuclear magnetic-resonance quantum computer. Using a spin-echo technique, the original method is modified so that quantum gates are implemented in a standard high-precision nuclear magnetic-resonance system for chemical analysis. We show that a dynamical phase is successfully eliminated and a one-qubit quantum gate is realized although the gate fidelity is not high.

  1. Phase Cycling Schemes for finite-pulse-RFDR MAS Solid State NMR Experiments

    PubMed Central

    Zhang, Rongchun; Nishiyama, Yusuke; Sun, Pingchuan; Ramamoorthy, Ayyalusamy

    2015-01-01

    The finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used in 2D homonuclear chemical shift correlation experiments under magic angle spinning (MAS). A recent study demonstrated the advantages of using a short phase cycle, XY4, and its super-cycle, XY414, for the fp-RFDR pulse sequence employed in 2D 1H/1H single-quantum/single-quantum correlation experiments under ultrafast MAS conditions. In this study, we report a comprehensive analysis on the dipolar recoupling efficiencies of XY4, XY412, XY413, XY414, and XY814 phase cycles under different spinning speeds ranging from 10 to 100 kHz. The theoretical calculations reveal the presence of second-order terms (T10T2,±2, T1,±1T2,±1, etc.) in the recoupled homonuclear dipolar coupling Hamiltonian only when the basic XY4 phase cycle is utilized, making it advantageous for proton-proton magnetization transfer under ultrafast MAS conditions. It is also found that the recoupling efficiency of fp-RFDR is quite dependent on the duty factor (τ180/τR) as well as on the strength of homonuclear dipolar couplings. The rate of longitudinal magnetization transfer increases linearly with the duty factor of fp-RFDR for all the XY-based phase cycles investigated in this study. Examination of the performances of different phase cycles against chemical shift offset and RF field in homogeneity effects revealed that XY414 is the most tolerant phase cycle, while the shortest phase cycle XY4 suppressed the RF field inhomogeneity effects most efficiently under slow spinning speeds. Our results suggest that the difference in the fp-RFDR recoupling efficiencies decreases with the increasing MAS speed, while ultrafast (>60 kHz) spinning speed is advantageous as it recouples a large amount of homonuclear dipolar couplings and therefore enable fast magnetization exchange. The effects of higher-order terms and cross terms between various interactions in the effective Hamiltonian of fp-RFDR are also analyzed

  2. Multinuclear NMR microscopy of two-phase fluid systems in porous rock.

    PubMed

    Doughty, D A; Tomutsa, L

    1996-01-01

    The high-field magnetic resonance (MR) characteristics of fluids in porous reservoir rock exhibit short T2 relaxation times and broad natural line widths. These characteristics severely restrict which MR imaging (MRI) methodology can be used to obtain high-resolution porescale images of fluids in porous rock. An MR microscopy protocol based on 3D backprojection using strong imaging gradients was developed to overcome many of these constraints. To improve the image quality of two-phase systems, multinuclear MRI using proton MR to image the brine phase and 19F MR of a fluorinated hydrocarbon to image the oil phase was used. Resolution as high as 25 microns per pixel has been obtained for fluid systems in Bentheim and Fontainebleau sandstones. Separate proton and 19F images of brine and oil phases show good agreement with total saturation images. Software has been developed to perform 3D erosion/dilations and to extract the pore size distribution from binarized 3D images of fluid filled porosity. Results from pore size measurements show significant differences in the nature of the pore network in Fontainebleau and Bentheim sandstones. PMID:8970097

  3. 2H NMR study of phase transition and hydrogen dynamics in hydrogen bonded organic antiferroelectric 55DMBP-H2ca

    NASA Astrophysics Data System (ADS)

    Asaji, Tetsuo; Hara, Masamichi; Fujimori, Hiroki; Hagiwara, Shoko

    2016-12-01

    Hydrogen dynamics in one-dimensional hydrogen bonded organic antiferroelectric, co-crystal of 5,5'-dimethyl-2,2'-bipyridine (55DMBP) and chloranilic acid (H2ca), was investigated by use of 2H high resolution solid-state NMR. The two types of hydrogen bonds O-H …N and N+-H … O - in the antiferroelectric phase were clearly observed as the splitting of the side band of the 2H MAS NMR spectra of the acid-proton deuterated compound 55DMBP-D 2ca. The temperature dependence of the spin-lattice relaxation time was measured of the N+-H and O-H deuterons, respectively. It was suggested that the motion of the O-H deuteron is already in the antiferroelectric phase in the fast-motion regime in the NMR time scale, while that of the N+-H deuteron is a slow motion. In the high-temperature paraelectric phase, the both deuterons become equivalent and the fast motion of the deuterons in the NMR time scale is taking place with the activation energy of 7.9 kJ mol-1.

  4. A novel fiber-based adsorbent technology

    SciTech Connect

    Reynolds, T.A.

    1997-10-01

    In this Phase I Small Business Innovation Research program, Chemica Technologies, Inc. is developing an economical, robust, fiber-based adsorbent technology for removal of heavy metals from contaminated water. The key innovation is the development of regenerable adsorbent fibers and adsorbent fiber cloths that have high capacity and selectivity for heavy metals and are chemically robust. The process has the potential for widespread use at DOE facilities, mining operations, and the chemical process industry.

  5. Pulsed-field-gradient NMR studies of hydrogen diffusion in Laves-phase hydrides

    SciTech Connect

    Majer, G.

    1998-12-31

    The diffusivities D of hydrogen in cubic Laves-phase hydrides have been measured by means of pulsed-field-gradient nuclear magnetic resonance over wide temperature ranges. A review is given of the diffusion coefficients of hydrogen in ZrCr{sub 2}H{sub x}, ZrTi{sub 2}H{sub x}, ZrV{sub 2}H{sub x}, ZrMo{sub 2}H{sub x} and HfV{sub 2}H{sub x} with special emphasis on the variation of D with the hydrogen concentration x. The formation of ordered low-temperature phases in ZrV{sub 2}H{sub x} results in a substantial reduction of the hydrogen diffusivity. The dependence of D on the lattice parameter of the host compound is considered.

  6. Analyte induced water adsorbability in gas phase biosensors: the influence of ethinylestradiol on the water binding protein capacity.

    PubMed

    Snopok, Borys; Kruglenko, Ivanna

    2015-05-01

    An ultra-sensitive gas phase biosensor/tracer/bio-sniffer is an emerging technology platform designed to provide real-time information on air-borne analytes, or those in liquids, through classical headspace analysis. The desired bio-sniffer measures gaseous 17α- ethinylestradiol (ETED) as frequency changes on a quartz crystal microbalance (QCM), which is a result of the interactions of liquid sample components in the headspace (ETED and water) with a biorecognition layer. The latter was constructed by immobilization of polyclonal antiserum against a phenolic A-ring of estrogenic receptors through protein A. The QCM response exhibited stretched exponential kinetics of negative frequency shifts with reversible and "irreversible" components of mass uptake onto the sensor surface in static headspace conditions when exposed to water solutions of ETED over the sensor working range, from 10(-10) to 10(-17) g L(-1). It was shown that the variations in the QCM response characteristics are due to the change of the water-binding capacity of the sensing layer induced by protein transformations initiated by the binding of ETED molecules. This result is well correlated with the natural physiological function of estrogens in controlling the homeostasis of body fluids in living beings. PMID:25763411

  7. N-methylimidazolium modified magnetic particles as adsorbents for solid phase extraction of genomic deoxyribonucleic acid from genetically modified soybeans.

    PubMed

    Deng, Manchen; Jiang, Cheng; Jia, Li

    2013-04-10

    N-Methylimidazolium modified magnetic particles (MIm-MPs) were prepared and applied in the solid phase extraction of genomic deoxyribonucleic acid (DNA) from genetically modified soybeans. The adsorption of MIm-MPs for DNA mainly resulted from the strong electrostatic interaction between the positively charged MPs and the negatively charged DNA. The elution of DNA from MPs-DNA conjugates using phosphate buffer resulted from the stronger electrostatic interaction of phosphate ions with MPs than DNA. In the extraction procedure, no harmful reagents (e.g. phenol, chloroform and isopropanol, etc.) used, high yield (10.4 μg DNA per 30 mg sample) and high quality (A260/A280=1.82) of DNA can be realized. The as-prepared DNA was used as template for duplex-polymerase chain reaction (PCR) and the PCR products were analyzed by a sieving capillary electrophoresis method. Quick and high quality extraction of DNA template, and fast and high resolution detection of duplex PCR products can be realized using the developed method. No toxic reagents are used throughout the method. PMID:23522109

  8. Gas-phase NMR. Part I. Conformational energies of 1,2-disubstituted propanes and a comparison with MM2 and MNDO calculations

    NASA Astrophysics Data System (ADS)

    Miyajima, Takashi; Hirano, Tsuneo; Sato, Hisaya

    1984-11-01

    Gas-phase 1H NMR spectra of 1,2-dichloropropane (1,2-DCP) and 1,2-di(methoxy- d3)-propane (1,2-DMP) have been measured. The conformational energies of these molecules in the gas phase were determined from the observed coupling constants under a three rotational isomeric state model and are compared with the theoretical values from MM2 molecular mechanics and MNDO molecular orbital calculations. The results indicate that gas-phase NMR is useful method for the determination of conformational energies of relatively complex molecules, and that the MNDO results are more reasonable than the MM2 results for molecules containing electronegative atoms such as oxygen.

  9. An investigation of catalytic active phase-support interactions by IR, NMR and x-ray absorption spectroscopies. Progress report, January 15, 1992--September 15, 1992

    SciTech Connect

    Haller, G.L.

    1992-09-01

    Active catalytic phases (metal, mixed metals, oxide or mixed oxides) interacting with oxide support on which the active phase is dispersed can affect the percentage exposed, the morphology of supported particles, the degree of reducibility of cations, etc., in a variety of ways. Our objective is to characterize the physical chemistry of the active phase-oxide support interaction by spectroscopic methods and to correlate this structure with catalytic function. Two catalytic systems and their associated techniques (x-ray absorption and NMR) are discussed in this progress report. Firstly, the interaction of Pt-Ni supported on silica and L-zeolite are characterized and compared by x-ray absorption spectroscopy (EXAFS). Secondly, we present both experimental and calculational developments of NMR for the investigation of amorphous silica-alumina catalysts and/or supports.

  10. Sideband separation experiments in NMR with phase incremented echo train acquisition

    NASA Astrophysics Data System (ADS)

    Walder, Brennan J.; Dey, Krishna K.; Kaseman, Derrick C.; Baltisberger, Jay H.; Grandinetti, Philip J.

    2013-05-01

    A general approach for enhancing sensitivity of nuclear magnetic resonance sideband separation experiments, such as Two-Dimensional One Pulse (TOP), Magic-Angle Turning (MAT), and Phase Adjust Spinning Sidebands (PASS) experiments, with phase incremented echo-train acquisition (PIETA) is described. This approach is applicable whenever strong inhomogeneous broadenings dominate the unmodulated frequency resonances, such as in non-crystalline solids or in samples with large residual frequency anisotropy. PIETA provides significant sensitivity enhancements while also eliminating spectral artifacts would normally be present with Carr-Purcell-Meiboom-Gill acquisition. Additionally, an intuitive approach is presented for designing and processing echo train acquisition magnetic resonance experiments on rotating samples. Affine transformations are used to relate the two-dimensional signals acquired in TOP, MAT, and PASS experiments to a common coordinate system. Depending on sequence design and acquisition conditions two significant artifacts can arise from truncated acquisition time and discontinuous damping in the T2 decay. Here we show that the former artifact can always be eliminated through selection of a suitable affine transformation, and give the conditions in which the latter can be minimized or removed entirely.

  11. Magic Angle Spinning NMR Spectroscopy: A Versatile Technique for Structural and Dynamic Analysis of Solid-Phase Systems

    PubMed Central

    Polenova, Tatyana; Gupta, Rupal; Goldbourt, Amir

    2016-01-01

    Magic Angle Spinning (MAS) NMR spectroscopy is a powerful method for analysis of a broad range of systems, including inorganic materials, pharmaceuticals, and biomacromolecules. The recent developments in MAS NMR instrumentation and methodologies opened new vistas to atomic-level characterization of a plethora of chemical environments previously inaccessible to analysis, with unprecedented sensitivity and resolution. PMID:25794311

  12. Carbon nanotube sponges as a solid-phase extraction adsorbent for the enrichment and determination of polychlorinated biphenyls at trace levels in environmental water samples.

    PubMed

    Wang, Lei; Wang, Xia; Zhou, Jia-Bin; Zhao, Ru-Song

    2016-11-01

    Carbon nanotube (CNT) sponges has recently attracted considerable attention in numerous fields because of its excellent properties, such as high porosity, light weight, and large surface area. The potential of CNT sponges for the solid-phase extraction (SPE) of organic pollutants at trace levels was investigated in this study for the first time. Seven polychlorinated biphenyls (PCBs) were selected as analytes, and gas chromatography-tandem mass spectrometry was employed for the detection. We optimized important parameters that may influence the efficiency of SPE, including the kind and volume of elution solvent, sample pH, and sample flow rate and volume. Under optimized conditions, low limits of detection (0.72-1.98ngL(-1)), wide range of linearity (10-1000ngL(-1)) and good repeatability (2.69-6.85%, n=5) were obtained. CNT sponges exhibited higher extraction performance than other adsorbent materials under the optimized conditions. Real environmental water samples were analyzed, and satisfactory recoveries (81.1-119.1%) were achieved. All these results demonstrated that CNT sponges are suitable SPE material for the enrichment and sensitive determination of PCBs at trace levels. PMID:27591590

  13. A novel dispersive solid-phase extraction method using metal-organic framework MIL-101 as the adsorbent for the analysis of benzophenones in toner.

    PubMed

    Li, Ning; Zhu, Quanfei; Yang, Yang; Huang, Jianlin; Dang, Xueping; Chen, Huaixia

    2015-01-01

    Metal-organic frameworks (MOFs) have been paid widespread attention in the field of adsorption and separation materials due to its porosity, large specific surface area, unsaturated metal-ligand sites and structural diversity. In this study, the green powder MIL-101 was synthesized and used for the extraction of benzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxy-benzophenone from toner samples for the first time. The synthesized MIL-101 was characterized by X-ray diffraction, scanning electron microscopy, thermogravimetry and nitrogen adsorption porosimetry. The MIL-101 was applied as the dispersive solid phase extraction (DSPE) adsorbent for the extraction and preconcentration of benzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxy-benzophenone from toner samples. The extraction conditions were investigated. Under the optimized conditions, a DSPE-HPLC method for the determination of benzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxy-benzophenone was developed. The method yielded a linear calibration curve in the concentration ranges from 4.0 to 3500 μg L(-1) for the three analytes in toner samples with regression coefficients (r(2)) of 0.9992, 0.9999 and 0.9990, respectively. Limits of detection were 1.2, 1.2 and 0.9 μg L(-1), respectively. Both the intra-day and inter-day precisions (RSDs) were <10%. PMID:25476369

  14. Magnetic metal-organic nanotubes: An adsorbent for magnetic solid-phase extraction of polychlorinated biphenyls from environmental and biological samples.

    PubMed

    Li, Qiu-Lin; Wang, Lei-Lei; Wang, Xia; Wang, Ming-Lin; Zhao, Ru-Song

    2016-06-01

    A new type of three-dimensional, echinus-like magnetic Fe3O4 @ cobalt(Ⅱ)-based metal-organic nanotube (Fe3O4 @ Co-MONT) yolk-shell microspheres, have been designed and synthesized for the first time. Fe3O4 @ Co-MONTs yolk-shell microspheres were characterized by scanning electron micrographs, transmission electron microscopy, Fourier transform infrared spectra, X-ray diffraction, and vibrating sample magnetometry. The feasibility of the new material for use as an absorbent was investigated for magnetic solid phase-extraction (MSPE) of polychlorinated biphenyls (PCBs) from environmental water samples and biological samples. The Plackett-Burman design and Box-Behnken design were used to determine and optimize the extraction parameters influencing the extraction efficiency through response surface methodology. Under the optimized conditions, the developed method showed good linearity within the range of 5-1000ngL(-1), low limits of detection (0.31-0.49ngL(-1)), and good reproducibility (RSD<10%). The proposed method was successfully applied for the analysis of PCBs in real environmental water samples. These results demonstrated that Fe3O4 @ Co-MONTs is a promising adsorbent material for the MSPE of PCBs at trace levels from environmental water samples and biological samples. PMID:27156750

  15. Moving NMR

    NASA Astrophysics Data System (ADS)

    Blümich, Bernhard; Casanova, Federico; Danieli, Ernesto; Gong, Qingxia; Greferath, Marcus; Haber, Agnes; Kolz, Jürgen; Perlo, Juan

    2008-12-01

    Initiated by the use of NMR for well logging, portable NMR instruments are being developed for a variety of novel applications in materials testing and process analysis and control. Open sensors enable non-destructive testing of large objects, and small, cup-size magnets become available for high throughput analysis by NMR relaxation and spectroscopy. Some recent developments of mobile NMR are reviewed which delineate the direction into which portable NMR is moving.

  16. MQ NMR and SPME analysis of nonlinearity in the degradation of a filled silicone elastomer

    SciTech Connect

    Chinn, S C; Alviso, C T; Berman, E S; Harvey, C A; Maxwell, R S; Wilson, T S; Cohenour, R; Saalwachter, K; Chasse, W

    2008-10-10

    Radiation induced degradation of polymeric materials occurs via numerous, simultaneous, competing chemical reactions. Though degradation is typically found to be linear in adsorbed dose, some silicone materials exhibit non-linear dose dependence due to dose dependent dominant degradation pathways. We have characterized the effects of radiative and thermal degradation on a model filled-PDMS system, Sylgard 184 (commonly used as an electronic encapsulant and in biomedical applications), using traditional mechanical testing, NMR spectroscopy, and sample headspace analysis using Solid Phase Micro-Extraction (SPME) followed by Gas Chromatography/Mass Spectrometry (GC/MS). The mechanical data and {sup 1}H spin-echo NMR indicated that radiation exposure leads to predominantly crosslinking over the cumulative dose range studies (0 to 250 kGray) with a rate roughly linear with dose. {sup 1}H Multiple Quantum NMR detected a bimodal distribution in the network structure, as expected by the proposed structure of Sylgard 184. The MQ-NMR further indicated that the radiation induced structural changes were not linear in adsorbed dose and competing chain scission mechanisms contribute more largely to the overall degradation process in the range of 50 -100 kGray (though crosslinking still dominates). The SPME-GC/MS data were analyzed using Principal Component Analysis (PCA), which identified subtle changes in the distributions of degradation products (the cyclic siloxanes and other components of the material) as a function of age that provide insight into the dominant degradation pathways at low and high adsorbed dose.

  17. NMR Studies of 3He Films on Boron Nitride

    NASA Astrophysics Data System (ADS)

    Tang, Y.; Sullivan, N. S.

    2014-12-01

    We report the results of NMR studies of the dynamics of 3He adsorbed on hexagonal boron nitride. These studies can identify the phase transitions of the 2D films as a function of temperature. A thermally activated temperature dependence is observed for 2.6 < T < 8 K compared to a linear temperature dependence for 0.7 < T < 2.6 K. This linear dependence is consistent with that expected for thermal diffusion in a fluid for coverages of 0.4 - 0.6 of a monolayer.

  18. NOx adsorber and method of regenerating same

    SciTech Connect

    Endicott, Dennis L.; Verkiel, Maarten; Driscoll, James J.

    2007-01-30

    New technologies, such as NOx adsorber catalytic converters, are being used to meet increasingly stringent regulations on undesirable emissions, including NOx emissions. NOx adsorbers must be periodically regenerated, which requires an increased fuel consumption. The present disclosure includes a method of regenerating a NOx adsorber within a NOx adsorber catalytic converter. At least one sensor positioned downstream from the NOx adsorber senses, in the downstream exhaust, at least one of NOx, nitrous oxide and ammonia concentrations a plurality of times during a regeneration phase. The sensor is in communication with an electronic control module that includes a regeneration monitoring algorithm operable to end the regeneration phase when a time rate of change of the at least one of NOx, nitrous oxide and ammonia concentrations is after an expected plateau region begins.

  19. Effects of post-reactor functionalization on the phase behaviour of an ethylene-1-octene copolymer studied using solid-state high resolution 13C NMR spectroscopy.

    PubMed

    Calucci, Lucia; Cicogna, Francesca; Forte, Claudia

    2013-10-01

    The effects of post-reactor functionalization with naphthoate-TEMPO on the structure and morphology of an ethylene-1-octene copolymer were investigated by means of solid-state NMR techniques and DSC measurements. Selective (13)C MAS experiments allowed the orthorhombic and the monoclinic crystalline phases and two amorphous phases with different degree of mobility to be detected and quantified. (13)C and (1)H relaxation time measurements and spin diffusion experiments gave insight into the polymer dynamics within the different phases, the crystalline domain dimensions, and the rate of chain diffusion between amorphous and crystalline phases. Comparison of the results obtained for the pristine copolymer and the functionalized samples clearly indicated that the functionalization procedure causes redistribution within the crystalline and the amorphous phases with no relevant change in the degree of crystallinity or in the crystalline domain average size, and slows down chain diffusion. PMID:23942957

  20. Study of the ferroelastic phase transition in the tetraethylammonium compound [N(C2H5)4]2ZnBr4 by magic-angle spinning and static NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2016-03-01

    The ferroelastic phase transition of tetraethylammonium compound [N(C2H5)4]2ZnBr4 at the phase transition temperature (TC) = 283 K was characterized by magic-angle spinning (MAS) and static nuclear magnetic resonance (NMR), and confirmed by optical polarizing spectroscopy. The structural geometry near TC was studied in terms of the chemical shifts and the spin-lattice relaxation times T1ρ in the rotating frame for 1H MAS NMR and 13C cross-polarization (CP)/MAS NMR. The two inequivalent ethyl groups were distinguishable in the 13C NMR spectrum, and the T1ρ results indicate that they undergo tumbling motion above TC in a coupled manner. From the 14N NMR results, the two nitrogen nuclei in the N(C2H5)4+ ions were distinguishable above TC, and the splitting in the spectra below TC was related to the ferroelastic domains with different orientations.

  1. NMR study of the AF-SC-SC-AF phased transition in a pnictide superconductor LaFeAsO1-xHx

    NASA Astrophysics Data System (ADS)

    Fujiwara, Naoki; Sakurai, Ryosuke; Iimura, Soushi; Matsuishi, Satoru; Hosono, Hideo; Yamakawa, Youichi; Kontani, Hiroshi

    2014-03-01

    We have performed 75As and 1H NMR measurements in LaFeAsO1xHx, an isomorphic compound of LaFeAsO1xFx. LaFeAsO1xHx is an electron doped system, and O2- can be replaced with H- up to x = 0.5. LaFeAsO1xHx is known for having double superconducting (SC) domes on H doping. Recently, we discovered that a new antiferromagnetic (AF) phase follows the double SC domes on further H doping, forming a symmetric AF-SC-SC-AF phase alignment in the electronic phase diagram Unlike the AF ordering in the lightly H-doped regime, the AF ordering in the highly H-doped regime is attributed to the nesting between electron pockets. In the conference, we will show the data of both NMR spectra and the relaxation rate 1/T1 in the whole doping region. We will discuss the difference of electronic states between the lightly H-doped AF-SC phases and highly H-doped SC-AF phases. This work is supported by a Grant-in-Aid (Grant No. KAKENHI 23340101) from the Ministry of Education, Science, and Culture, Japan.

  2. Deuterium dynamics in the icosahedral and amorphous phases of the Ti40Zr40Ni20 hydrogen-absorbing alloy studied by 2H NMR

    NASA Astrophysics Data System (ADS)

    Gradišek, A.; Kocjan, A.; McGuiness, P. J.; Apih, T.; Kim, Hae Jin; Dolinšek, J.

    2008-11-01

    The Ti40Zr40Ni20 hydrogen-absorbing alloy was prepared in the icosahedral and amorphous phases by controlling the rotation speed of the melt-spinning method of sample preparation, and the deuterium dynamics was investigated by 2H NMR dynamic lineshape and spin-lattice relaxation. The results were analysed by the lineshape and relaxation models that assume deuterium thermally activated hopping within a manifold of different chemical environments. The observed 8% larger activation energy for the deuterium hopping over the interstitial sites and the 10% larger static spectrum width of the amorphous phase, as compared to the icosahedral phase, can be accounted for by the larger deuterium content of the investigated amorphous sample. From the deuterium dynamics point of view, the icosahedral phase is not special with respect to the amorphous modification of the same material.

  3. An investigation of catalytic active phase-support interactions by IR, NMR and x-ray absorption spectroscopies. Progress report, January 15, 1991--July 31, 1993

    SciTech Connect

    Haller, G.L.

    1993-07-01

    Active catalytic phases (metal, mixed metals, oxide or mixed oxides) interacting with oxide support can affect percentage exposed, the morphology of supported particles, the degree of reducibility of cations, etc., in a variety of ways. Solid state {sup 29}Si NMR was used to obtain a new correlation between partial charge on the Si which comprises a part of the SiOHAl Br{o}nsted acid structure in amorphous silica-aluminas. We also describe two potential improvements in solid state NMR applied to catalysts and catalysts supports. One is experimental, dynamic angle spinning NMR, a new technique for obtaining high resolution spectra of quadrupolar nuclei, e.g., {sup 27}Al. The second approach is an alternative to the standard fast Fourier transform of the free induction decay to convert from the time to spectral domain, the maximum entropy method. Effect of different methods of preparation of Pd/L-zeolites is described. By comparison to analogous Pt systems, it is the inherent chemistry of the L-zeolite which results in better dispersion when impregnation preparation is used relative to ion exchange preparation. X-ray absorption spectroscopy is used to compare the effect of support (SiO{sub 2} and L-zeolite) on the degree and kind of Pt-Ni interaction. When supported in L-zeolite and promoted with Ni, Pt has improved stability both with regard to self-poisoning and sulfur catalyzed agglomeration.

  4. Multinuclear solid film state NMR studies of metal oxide catalysts and minerals

    SciTech Connect

    Maxwell, R.S.; Stec, D.F.; Ellis, P.D.

    1996-10-01

    Several of our investigations of heterogeneous process by novel NMR experiments and analyses are reviewed and the utility and limitations of NMR spectroscopy for these areas discussed. Out studies have included the following: dynamics and arrangements of proton-containing adsorbates, primarily Bronsted acid sites and water, on the surface of zirconia and alumina catalysts; hydrogen dynamics and coordinates in synthetic aluminum oxyhydroxides; phase separation and crystallinity of synthetic minerals. In combination with the complementary results obtained in our laboratory via infrared spectroscopy, thermal analysis (primarily TGA and DSC), and catalytic activity measurements, these NMR data provide unique and valuable information on atomic and molecular dynamics, identities, and structures without requiring pristine, single crystal specimens.

  5. Evidence of a structural phase transition in superconducting SmFeAsO1-xFx from 19F NMR

    NASA Astrophysics Data System (ADS)

    Majumder, M.; Ghoshray, K.; Mazumdar, C.; Poddar, A.; Ghoshray, A.; Berardan, D.; Dragoe, N.

    2013-01-01

    We report resistivity, magnetization and 19F NMR results in a polycrystalline sample of SmFeAsO0.86F0.14. The resistivity and magnetization data show a sharp drop at 48 K indicating a superconducting transition. The nuclear spin-lattice rate (1/T1) and spin-spin relaxation rate (1/T2) clearly show the existence of a structural phase transition near 163 K in the sample, which also undergoes a superconducting transition. This finding creates interest in exploring whether this is unique for Sm based systems or is also present in other rare-earth based 1111 superconductors.

  6. Chromatographic NMR in NMR solvents

    NASA Astrophysics Data System (ADS)

    Carrara, Caroline; Viel, Stéphane; Delaurent, Corinne; Ziarelli, Fabio; Excoffier, Grégory; Caldarelli, Stefano

    2008-10-01

    Recently, it was demonstrated that pseudo-chromatographic NMR experiments could be performed using typical chromatographic solids and solvents. This first setup yielded improved separation of the spectral components of the NMR spectra of mixtures using PFG self-diffusion measurements. The method (dubbed Chromatographic NMR) was successively shown to possess, in favorable cases, superior resolving power on non-functionalized silica, compared to its LC counterpart. To further investigate the applicability of the method, we studied here the feasibility of Chromatographic NMR in common deuterated solvents. Two examples are provided, using deuterated chloroform and water, for homologous compounds soluble in these solvents, namely aromatic molecules and alcohols, respectively.

  7. Li7 NMR Investigation of Li-Li Pair Ordering in the Paraelectric Phase of Weakly Substitutionally Disordered K1-xLixTaO3

    NASA Astrophysics Data System (ADS)

    Zalar, Boštjan; Lebar, Andrija; Ailion, David C.; Kuzian, R. O.; Kondakova, I. V.; Laguta, V. V.

    2010-11-01

    Breaking of the average cubic symmetry in Li-doped potassium tantalate was observed with quadrupole-perturbed Li7 NMR at temperatures (150-400 K) far above the nominal glass transition temperature (≈50K for Li concentration x=0.03). The observed spectrum consists of contributions from both isolated Li ions (i.e., with no nearest-neighbor Li) and from Li-Li pairs. The isolated Li ions move among six equivalent off-center sites in a potential having cubic symmetry. These have zero average electric field gradient and, hence, exhibit no quadrupole splitting. In addition, very low intensity, but well resolved, quadrupole satellites having a temperature-dependent splitting were observed. This splitting indicates that the various Li-Li pair configurations are not all equally probable. These are the first direct observations of biased Li ion ordering that persists in the paraelectric phase at temperatures high above the glass phase.

  8. Photochemistry of Nitrate Adsorbed on Mineral Dust

    NASA Astrophysics Data System (ADS)

    Gankanda, A.; Grassian, V. H.

    2013-12-01

    Mineral dust particles in the atmosphere are often associated with adsorbed nitrate from heterogeneous reactions with nitrogen oxides including HNO3 and NO2. Although nitrate ion is a well-studied chromophore in natural waters, the photochemistry of adsorbed nitrate on mineral dust particles is yet to be fully explored. In this study, wavelength dependence of the photochemistry of adsorbed nitrate on different model components of mineral dust aerosol has been investigated using transmission FTIR spectroscopy. Al2O3, TiO2 and NaY zeolite were used as model systems to represent non-photoactive oxides, photoactive semiconductor oxides and porous materials respectively, present in mineral dust aerosol. In this study, adsorbed nitrate is irradiated with 254 nm, 310 nm and 350 nm narrow band light. In the irradiation with narrow band light, NO2 is the only detectable gas-phase product formed from nitrate adsorbed on Al2O3 and TiO2. The NO2 yield is highest at 310 nm for both Al2O3 and TiO2. Unlike Al2O3 and TiO2, in zeolite, adsorbed nitrate photolysis to nitrite is observed only at 310 nm during narrow band irradiation. Moreover gas phase products were not detected during nitrate photolysis in zeolite at all three wavelengths. The significance of these differences as related to nitrate photochemistry on different mineral dust components will be highlighted.

  9. Molecular Adsorber Coating

    NASA Technical Reports Server (NTRS)

    Straka, Sharon; Peters, Wanda; Hasegawa, Mark; Hedgeland, Randy; Petro, John; Novo-Gradac, Kevin; Wong, Alfred; Triolo, Jack; Miller, Cory

    2011-01-01

    A document discusses a zeolite-based sprayable molecular adsorber coating that has been developed to alleviate the size and weight issues of current ceramic puck-based technology, while providing a configuration that more projects can use to protect against degradation from outgassed materials within a spacecraft, particularly contamination-sensitive instruments. This coating system demonstrates five times the adsorption capacity of previously developed adsorber coating slurries. The molecular adsorber formulation was developed and refined, and a procedure for spray application was developed. Samples were spray-coated and tested for capacity, thermal optical/radiative properties, coating adhesion, and thermal cycling. Work performed during this study indicates that the molecular adsorber formulation can be applied to aluminum, stainless steel, or other metal substrates that can accept silicate-based coatings. The coating can also function as a thermal- control coating. This adsorber will dramatically reduce the mass and volume restrictions, and is less expensive than the currently used molecular adsorber puck design.

  10. Solid-state 13C NMR study of banana liquid crystals - 3: Alkyl-tail-group packing environments of an acute-angle bent-core molecule in the hexagonal columnar and cubic phases

    NASA Astrophysics Data System (ADS)

    Kurosu, Hiromichi; Endo, Yumi; Kimura, Saori; Hashimoto, Tomoko; Harada, Motoi; Lee, Eun-Woo; Sone, Masato; Watanabe, Junji; Kang, Sungmin

    2016-02-01

    Solid-state 13C nuclear magnetic resonance (NMR) measurements were performed on the hexagonal columnar and cubic phases of an acute-angle banana-shaped molecule, N(1,7)-S30. In the hexagonal columnar phase, three peaks appear at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that the two alkyl tails have different packing structures, and one of the tails has two different conformations within a single molecule. Combined cross-polarization/magic-angle spinning and pulse saturation transfer/magic-angle spinning measurements show that one of the alkyl chains is located inside and the other is located outside the columnar structure. In the cubic phase, pulse saturation transfer/magic-angle spinning measurement shows that only one peak appears at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that both of the alkyl chains are located outside the cubic structure.

  11. NMR Study on Ion Dynamics and Phase Behavior of a Piperidinium-Based Room-Temperature Ionic Liquid: 1-Butyl-1-methylpiperidinium Bis(fluorosulfonyl)amide.

    PubMed

    Shimizu, Yuichi; Wachi, Yuto; Fujii, Kozo; Imanari, Mamoru; Nishikawa, Keiko

    2016-06-30

    By use of pulse NMR methods, the temperature dependences of the longitudinal and transverse relaxation times for (1)H and (19)F were measured for the three phases of 1-butyl-1-methylpiperidinium bis(fluorosulfonyl)amide ([Pip1,4][FSA]), i.e., liquid or supercooled liquid, Cryst-α, and Cryst-β, to investigate the ion dynamics and phase behavior related to the dynamics. Since the cations and anions in the room-temperature ionic liquid have (1)H and (19)F nuclei, respectively, the dynamics of the [Pip1,4] cation and [FSA] anion can be independently observed and the relation between them can be evaluated. The relevant local motions of the ions are fluctuational motion around the chair form of the piperidinium ring, libration or rotation of the alkyl groups, and libration or rotation of the SO2F groups around the N-S axes. Each phase preferentially exhibits these motions. In the Cryst-β phase, it is thought that O atoms in the SO2F groups form strong hydrogen bonds with the H atoms in the piperidinium ring. As a result, the motions of the SO2F groups and the piperidinium ring are restricted. In the liquid or supercooled liquid states and Cryst-α phase, the motion of the anion is more significant than that of the cation and the former works as a trigger for phase changes. Particularly, the motion of the SO2F groups in the Cryst-α phase becomes very significant with rising temperature and is directly related to the melting phase transition. PMID:27281062

  12. Monitoring and understanding the paraelectric-ferroelectric phase transition in the metal-organic framework [NH4 ][M(HCOO)3 ] by solid-state NMR spectroscopy.

    PubMed

    Xu, Jun; Lucier, Bryan E G; Sinelnikov, Regina; Terskikh, Victor V; Staroverov, Viktor N; Huang, Yining

    2015-10-01

    The paraelectric-ferroelectric phase transition in two isostructural metal-organic frameworks (MOFs) [NH4 ][M(HCOO)3 ] (M=Mg, Zn) was investigated by in situ variable-temperature (25) Mg, (67) Zn, (14) N, and (13) C solid-state NMR (SSNMR) spectroscopy. With decreasing temperature, a disorder-order transition of NH4 (+) cations causes a change in dielectric properties. It is thought that [NH4 ][Mg(HCOO)3 ] exhibits a higher transition temperature than [NH4 ][Zn(HCOO)3 ] due to stronger hydrogen-bonding interactions between NH4 (+) ions and framework oxygen atoms. (25) Mg and (67) Zn NMR parameters are very sensitive to temperature-induced changes in structure, dynamics, and dielectric behavior; stark spectral differences across the paraelectric-ferroelectric phase transition are intimately related to subtle changes in the local environment of the metal center. Although (25) Mg and (67) Zn are challenging nuclei for SSNMR experiments, the highly spherically symmetric metal-atom environments in [NH4 ][M(HCOO)3 ] give rise to relatively narrow spectra that can be acquired in 30-60 min at a low magnetic field of 9.4 T. Complementary (14) N and (13) C SSNMR experiments were performed to probe the role of NH4 (+) -framework hydrogen bonding in the paraelectric-ferroelectric phase transition. This multinuclear SSNMR approach yields new physical insights into the [NH4 ][M(HCOO)3 ] system and shows great potential for molecular-level studies on electric phenomena in a wide variety of MOFs. PMID:26397187

  13. Accessing structure and dynamics of mobile phase in organic solids by real-time T1C filter PISEMA NMR spectroscopy.

    PubMed

    Zhang, Rongchun; Chen, Yuzhu; Chen, Tiehong; Sun, Pingchuan; Li, Baohui; Ding, Datong

    2012-01-26

    The structure and dynamic behavior of mobile components play a significant role in determining properties of solid materials. Herein, we propose a novel real-time spectrum-editing method to extract signals of mobile components in organic solids on the basis of the polarization inversion spin exchange at magic angle (PISEMA) pulse sequence and the difference in (13)C T(1) values of rigid and mobile components. From the dipolar splitting spectrum sliced along the heteronuclear dipolar coupling dimension of the 2D spectrum, the structural and dynamic information can be obtained, such as the distances between atoms, the dipolar coupling strength, the order parameter of the polymer backbone chain, and so on. Furthermore, our proposed method can be used to achieve the separation of overlapped NMR signals of mobile and rigid phases in the PISEMA experiment. The high efficacy of this 2D NMR method is demonstrated on organic solids, including crystalline L-alanine, semicrystalline polyamide-6, and the natural abundant silk fibroin. PMID:22185485

  14. Joint NMR and Solid-Phase Microextraction-Gas Chromatography Chemometric Approach for Very Complex Mixtures: Grape and Zone Identification in Wines.

    PubMed

    Martin-Pastor, Manuel; Guitian, Esteban; Riguera, Ricardo

    2016-06-21

    In very complex mixtures, classification by chemometric methods may be limited by the difficulties to extract from the NMR or gas chromatography/mass spectrometry (GC/MS) experimental data information useful for a reliable classification. The joint analysis of both data has showed its superiority in the biomedical field but is scarcely used in foodstuffs and never in wine in spite of the complexity of their spectra and classification. In this article we show that univariate and multivariate principal component analysis-discriminant analysis (PCA-DA) statistics applied to the combined (1)H NMR and solid-phase microextraction-gas chromatography (SPME-GC) data of a collection of 270 wines from Galicia (northwest Spain) allows a discrimination and classification not attainable from the separate data, distinguishing wines from autochthonous and nonautochthonous grapes, mono- from the plurivarietals, and identifying, in part, the geographical subzone of origin of the albariño wines. A general and automatable protocol, based on the signal integration of selected ROIs (regions of interest), is proposed that allows the fast and reliable identification of the grape in Galician wines. PMID:27247992

  15. Investigation of Phase Mixing in Amorphous Solid Dispersions of AMG 517 in HPMC-AS Using DSC, Solid-State NMR, and Solution Calorimetry.

    PubMed

    Calahan, Julie L; Azali, Stephanie C; Munson, Eric J; Nagapudi, Karthik

    2015-11-01

    Intimate phase mixing between the drug and the polymer is considered a prerequisite to achieve good physical stability for amorphous solid dispersions. In this article, spray dried amorphous dispersions (ASDs) of AMG 517 and HPMC-as were studied by differential scanning calorimetry (DSC), solid-state NMR (SSNMR), and solution calorimetry. DSC analysis showed a weakly asymmetric (ΔTg ≈ 13.5) system with a single glass transition for blends of different compositions indicating phase mixing. The Tg-composition data was modeled using the BKCV equation to accommodate the observed negative deviation from ideality. Proton spin-lattice relaxation times in the laboratory and rotating frames ((1)H T1 and T1ρ), as measured by SSNMR, were consistent with the observation that the components of the dispersion were in intimate contact over a 10-20 nm length scale. Based on the heat of mixing calculated from solution calorimetry and the entropy of mixing calculated from the Flory-Huggins theory, the free energy of mixing was calculated. The free energy of mixing was found to be positive for all ASDs, indicating that the drug and polymer are thermodynamically predisposed to phase separation at 25 °C. This suggests that miscibility measured by DSC and SSNMR is achieved kinetically as the result of intimate mixing between drug and polymer during the spray drying process. This kinetic phase mixing is responsible for the physical stability of the ASD. PMID:26457879

  16. Magnetic solid-phase extraction using poly(para-phenylenediamine) modified with magnetic nanoparticles as adsorbent for analysis of monocyclic aromatic amines in water and urine samples.

    PubMed

    Amiri, Amirhassan; Baghayeri, Mehdi; Nori, Somayeh

    2015-10-01

    In the present work, a simple and effective method based on magnetic separation has been developed for the extraction of monocyclic aromatic amines in water and urine samples using poly(para-phenylenediamine) modified with Fe3O4 nanoparticles (PpPD/Fe3O4) as an adsorbent. The chemical structures of the sorbent were characterized by field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectrophotometer (FT-IR). Various parameters affecting on the extraction efficiency of desired analytes, such as pH of solution, desorption conditions, extraction time, salt effect and amount of adsorbent have been investigated and optimized. The obtained optimal conditions were: sample pH, 6; amount of sorbent, 20mg; sorption time, 2min; elution solvent and its volume, dichloromethane and chloroform (3:1 v/v), 250μL; elution time, 30s and without addition of NaCl. Under the optimum conditions, detection limits in the range of 0.007-0.01ngmL(-1) were obtained by gas chromatography-flame ionization detector (GC-FID). The calibration curves were linear in the range 0.05-100ngmL(-1) with a correlation coefficient better than 0.9953. In addition, a satisfactory reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations (RSDs) less than 5.9 and 7.3%, respectively. The proposed procedure has been successfully applied to the determination of target analytes in water and urine samples. The results demonstrated that the developed method is simple, inexpensive, accurate and remarkably free from interference effects. PMID:26341590

  17. Synthesis of mimic molecularly imprinted ordered mesoporous silica adsorbent by thermally reversible semicovalent approach for pipette-tip solid-phase extraction-liquid chromatography fluorescence determination of estradiol in milk.

    PubMed

    Wang, Lu; Yan, Hongyuan; Yang, Chunliu; Li, Zan; Qiao, Fengxia

    2016-07-22

    A mimic molecularly imprinted ordered mesoporous silica (MIOMS) adsorbent was prepared utilizing a thermally reversible semicovalent approach. The thermally reversible covalent template-monomer complex was firstly synthesized by employing 4,4'-sulfonyldiphenol (BPS) and (3-isocyanatopropyl) triethoxysilane (ICPTES) as template and monomer, respectively. The template-monomer complex was incorporated into ordered mesoporous silica via a simple self-assembly process. The adsorption experiment illustrated that the imprint-removed silica (MIOMS-ir) had higher special recognition ability (250μgg(-1)) for estradiol (E2) than the non-imprinted silica (NIOMS-ir) (25μgg(-1)). MIOMS-ir was applied as an adsorbent in pipette-tip solid-phase extraction (PT-SPE) coupled with liquid chromatography-fluorescence detector (LC-FLD) for determination of E2 in milk samples. Under the optimized conditions, only 3mg of the adsorbent, 0.3mL of water as washing solvent, and 0.5mL of acetonitrile-acetic acid (96:4, v/v) as elution solvent were used in the pretreatment procedure of milk samples. Good calibration linearity was obtained in a range of 25ngL(-1) to 1000ngL(-1), and the recoveries at three spiked levels were ranged from 95.4% to 107.0% with relative standard deviations (RSDs) ≤3.1% (n=3). The proposed MIOMS-ir-PT-SPE-LC-FLD method combined the advantages of PT-SPE and ordered mesoporous material such as ease assembly, low cost, high extraction efficiency and large specific surface area, so it is a potential pretreatment strategy for the extraction and determination of E2 in complex milk samples. PMID:27328886

  18. Distinction of tris(diimine)ruthenium(II) enantiomers chiral by virtue of helical chirality: temperature-dependent deuterium NMR spectroscopy in partially oriented phases.

    PubMed

    Szalontai, Gábor; Kovács, Margit

    2006-11-01

    2H NMR spectra of perdeuterated tris(diimine)ruthenium(II) complexes have been recorded in lyotropic liquid crystalline phase formed by the chiral polypeptide, poly-gamma-benzyl-L-glutamate (PBLG) and co-solvents. It is demonstrated that the left- and right-rotation isomers of these octahedral metal complexes with D3 symmetry can be distinguished. The effects of temperature and ligand size on spectral resolution were also studied. Although in the case of free bipyridine ligands excellent optical resolution could be obtained at room temperature in the complexes studied, the increase in ligand size has a detrimental effect on the resolution. This can be compensated to some extent by elevating the sample temperature and decreasing the deuterium relaxation rates, but the available temperature range and therefore the applicability of the technique are limited. PMID:16958156

  19. Deuteron and proton NMR study of D2, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases

    NASA Astrophysics Data System (ADS)

    Burnell, E. E.; Ahmed, Z.; Welch, C.; Mehl, G. H.; Dong, R. Y.

    2016-08-01

    The solutes dideuterium, 1,3,5-trichlorobenzene and p-dichlorobenzene (pdcb) are co-dissolved in a 61/39 wt% mixture of CBC9CB/5CB, a bimesogenic liquid crystal with two nematic phases. NMR spectra are collected for each solute. The local electric field gradient (FZZ) is obtained from the dideuterium spectrum. A double Maier-Saupe potential (MSMS) is used to rationalize the order parameters of pdcb. The liquid-crystal fields G1 and G2 are taken to be due to size and shape interactions and interactions between the solute molecular quadrupole and the mean FZZ of the medium. The FZZ 's obtained from D2 and G2 (from pdcb) are compared and discussed.

  20. Stability-indicating reversed-phase HPLC method development and characterization of impurities in vortioxetine utilizing LC-MS, IR and NMR.

    PubMed

    Liu, Lei; Cao, Na; Ma, Xingling; Xiong, Kaihe; Sun, Lili; Zou, Qiaogen; Yao, Lili

    2016-01-01

    The current study reports the development and validation of a stability-indicating reversed phase HPLC method for the separation and identification of potential impurities in vortioxetine, a recently developed antidepressant. The structures of a new compound and four process-related impurities formed during the synthesis were characterized and confirmed by NMR, MS, and IR spectroscopy analyses. The most probable formation mechanisms of the impurities identified were proposed. Based on the characterization data, the new compound was proposed to be 1-[4-[(2,4-dimethylphenyl)thio]phenyl]-piperazine. In addition, an efficient chromatographic method was optimized to separate and quantify the impurities, which were obtained in the 0.05-0.75 μg/mL range. The developed HPLC method was validated with respect to accuracy, precision, linearity, robustness, and limits of detection and quantitation. PMID:26412721

  1. Tracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes: Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy.

    PubMed

    Allan, Phoebe K; Griffin, John M; Darwiche, Ali; Borkiewicz, Olaf J; Wiaderek, Kamila M; Chapman, Karena W; Morris, Andrew J; Chupas, Peter J; Monconduit, Laure; Grey, Clare P

    2016-02-24

    Operando pair distribution function (PDF) analysis and ex situ (23)Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy are used to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline NaxSb phases from the total PDF, an approach constrained by chemical phase information gained from (23)Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na(3-x)Sb (x ≈ 0.4-0.5), a structure locally similar to crystalline Na3Sb (c-Na3Sb) but with significant numbers of sodium vacancies and a limited correlation length, and a-Na(1.7)Sb, a highly amorphous structure featuring some Sb-Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na(3-x)Sb and, finally, crystalline Na3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphous network reacts at higher voltages reforming a-Na(1.7)Sb, then a-Na(3-x)Sb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na(3-x)Sb without the formation of a-Na(1.7)Sb. a-Na(3-x)Sb is converted to crystalline Na3Sb at the end of the second discharge. We find no evidence of formation of NaSb. Variable temperature (23)Na NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes. PMID:26824406

  2. Tracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes: Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy

    PubMed Central

    2016-01-01

    Operando pair distribution function (PDF) analysis and ex situ 23Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy are used to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline NaxSb phases from the total PDF, an approach constrained by chemical phase information gained from 23Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na3–xSb (x ≈ 0.4–0.5), a structure locally similar to crystalline Na3Sb (c-Na3Sb) but with significant numbers of sodium vacancies and a limited correlation length, and a-Na1.7Sb, a highly amorphous structure featuring some Sb–Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na3–xSb and, finally, crystalline Na3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphous network reacts at higher voltages reforming a-Na1.7Sb, then a-Na3–xSb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na3–xSb without the formation of a-Na1.7Sb. a-Na3–xSb is converted to crystalline Na3Sb at the end of the second discharge. We find no evidence of formation of NaSb. Variable temperature 23Na NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes. PMID:26824406

  3. Regenerative adsorbent heat pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1991-01-01

    A regenerative adsorbent heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system and at least a portion of the heat of adsorption. A series of at least four compressors containing an adsorbent is provided. A large amount of heat is transferred from compressor to compressor so that heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

  4. Bovine serum albumin-Cu(II) hybrid nanoflowers: An effective adsorbent for solid phase extraction and slurry sampling flame atomic absorption spectrometric analysis of cadmium and lead in water, hair, food and cigarette samples.

    PubMed

    Yilmaz, Erkan; Ocsoy, Ismail; Ozdemir, Nalan; Soylak, Mustafa

    2016-02-01

    Herein, the synthesis of bovine serum albumin-Cu(II) hybrid nanoflowers (BSA-NFs) through the building blocks of bovine serum albumin (BSA) and copper(II) ions in phosphate buffered saline (PBS) and their use as adsorbent for cadmium and lead ions are reported. The BSA-NFs, for the first time, were efficiently utilized as novel adsorbent for solid phase extraction (SPE) of cadmium and lead ions in water, food, cigarette and hair samples. The method is based on the separation and pre-concentration of Cd(II) and Pb(II) by BSA-NFs prior to determination by slurry analysis via flame atomic absorption spectrometry (FAAS). The analytes were adsorbed on BSA-NFs under the vortex mixing and then the ion-loaded slurry was separated and directly introduced into the flame AAS nebulizer by using a hand-made micro sample introduction system to eliminate a number of drawbacks. The effects of analytical key parameters, such as pH, amount of BSA-NFs, vortexing time, sample volume, and matrix effect of foreign ions on adsorbing of Cd(II) and Pb(II) were systematically investigated and optimized. The limits of detection (LODs) for Cd(II) and Pb(II) were calculated as 0.37 μg L(-)(1) and 8.8 μg L(-)(1), respectively. The relative standard deviation percentages (RSDs) (N = 5) for Cd(II) and Pb(II) were 7.2%, and 5.0%, respectively. The accuracy of the developed procedure was validated by the analysis of certified reference materials (TMDA-53.3 Fortified Water, TMDA-70 Fortified Water, SPS-WW2 Waste Water, NCSDC-73349 Bush Branches and Leaves) and by addition/recovery analysis. The quantitative recoveries were obtained for the analysis of certified reference materials and addition/recovery tests. The method was successfully applied to the analysis of cadmium and lead in water, food, cigarette and hair samples. PMID:26772130

  5. Nanopore reactive adsorbents for the high-efficiency removal of waste species

    DOEpatents

    Yang, Arthur Jing-Min; Zhang, Yuehua

    2005-01-04

    A nanoporous reactive adsorbent incorporates a relatively small number of relatively larger reactant, e.g., metal, enzyme, etc., particles (10) forming a discontinuous or continuous phase interspersed among and surrounded by a continuous phase of smaller adsorbent particles (12) and connected interstitial pores (14) therebetween. The reactive adsorbent can effectively remove inorganic or organic impurities in a liquid by causing the liquid to flow through the adsorbent. For example, silver ions may be adsorbed by the adsorbent particles (12) and reduced to metallic silver by reducing metal, such as ions, as the reactant particles (10). The column can be regenerated by backwashing with the liquid effluent containing, for example, acetic acid.

  6. Adsorbent and adsorbent bed for materials capture and separation processes

    SciTech Connect

    Liu, Wei

    2011-01-25

    A method device and material for performing adsorption wherein a fluid mixture is passed through a channel in a structured adsorbent bed having a solid adsorbent comprised of adsorbent particles having a general diameter less than 100 um, loaded in a porous support matrix defining at least one straight flow channel. The adsorbent bed is configured to allow passage of a fluid through said channel and diffusion of a target material into said adsorbent under a pressure gradient driving force. The targeted molecular species in the fluid mixture diffuses across the porous support retaining layer, contacts the adsorbent, and adsorbs on the adsorbent, while the remaining species in the fluid mixture flows out of the channel.

  7. Development of a Desulfurization Strategy for a NOx Adsorber Catalyst

    SciTech Connect

    Tomazic, Dean

    2000-08-20

    Improve NOx regeneration calibration developed in DECSE Phase I project to understand full potential of NOx adsorber catalyst over a range of operating temperatures. Develop and demonstrate a desulfurization process to restore NOx conversion efficiency lost to sulfur contamination. Investigate effect of desulfurization process on long-term performance of the NOx adsorber catalyst.

  8. Phase Separation in Binary Mixtures of Bipolar and Monopolar Lipid Dispersions Revealed by 2H NMR Spectroscopy, Small Angle X-Ray Scattering, and Molecular Theory

    PubMed Central

    Brownholland, David P.; Longo, Gabriel S.; Struts, Andrey V.; Justice, Matthew J.; Szleifer, Igal; Petrache, Horia I.; Brown, Michael F.; Thompson, David H.

    2009-01-01

    Abstract Binary mixtures of C20BAS and POPC membranes were studied by solid-state 2H NMR spectroscopy and small angle x-ray scattering (SAXS) over a wide range of concentrations and at different temperatures. Three specifically deuterated C20BAS derivatives—[1′,1′,20′,20′-2H4]C20BAS, [2′,2′,19′,19′-2H4]C20BAS, and [10′,11′-2H2]C20BAS—combined with protiated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), as well as membranes containing POPC-d31 and fully protiated bolalipid, were used in NMR experiments to obtain structural information for the mixtures. The 2H NMR spectra of [10′,11′-2H2]C20BAS/POPC membrane dispersions reveal that the bolalipid is predominantly in the transmembrane conformation at high bolalipid concentrations (100, 90, and 70 mol %). At ≤50 mol % C20BAS, smaller quadrupolar couplings appear in the spectra, indicating the presence of U-shaped conformers. The proportion of U-shaped bolalipids increases as the amount of POPC in the membrane increases; however, the transmembrane component remains the dominant bolalipid conformation in the membrane even at 45°C and 10 mol % C20BAS, where it accounts for ∼50% of the bolalipid population. The large fraction of C20BAS transmembrane conformers, regardless of the C20BAS/POPC ratio, together with the findings from molecular mean-field theory calculations, suggests the coexistence of phase-separated bolalipid-rich domains and POPC-rich domains. A single lamellar repeat distance was observed in SAXS experiments corresponding to the average repeat spacing expected for C20BAS- and POPC-rich domains. These observations are consistent with the presence of microphase-separated domains in the mixed membrane samples that arise from POPC-C20BAS hydrophobic mismatch. PMID:19917223

  9. Ferroelastic phase transitions by 14N NMR spectra in [N(CH3)4]2CoCl4 and [N(CH3)4]2ZnCl4 single crystals

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2016-09-01

    Changes in the structural geometry of [N(CH3)4]2BCl4 (B=Co and Zn) crystals near the phase transition temperatures were studied by analyzing the 14N nuclear magnetic resonance (NMR) spectra. Two physically inequivalent a-N(1)(CH3)4 and b-N(2)(CH3)4 groups were observed in these spectra. Abrupt changes in the resonance frequency and splitting of 14N NMR signals near the phase transition temperatures were attributed to structural phase transitions, and the primary mechanism of these phase transitions exhibited ferroelastic characteristics. In addition, ferroelasticity of [N(CH3)4]2BCl4 was identified at low temperatures using optical polarizing microscopy.

  10. [Determination of six phthalate acid esters in camellia oil by gas chromatography-mass spectrometry coupled with solid-phase extraction using single-walled carbon nanotubes as adsorbent].

    PubMed

    Zhang, Fan; Li, Zhonghai; Zhang, Ying; Huang, Zhiqiang; Wang, Xiaosong

    2014-07-01

    An analytical method based on solid-phase extraction with single-walled carbon nanotubes (SWCNTs) as adsorbent was developed for the simultaneous determination of six phthalate acid esters (PAEs) in camellia oil by gas chromatography-mass spectrometry (GC-MS). The samples were diluted by hexane and then cleaned up with a glass SWCNTs solid phase extraction (SPE) column. The PAEs were measured by GC-MS in selected ion monitoring (SIM) mode, using external standard method for quantitative analysis. The important factors affecting extraction efficiency, such as the dilution volume of hexane, the type of adsorbent material, the dosage of SWCNTs, the volume of wash solution, the type and volume of elution solution were optimized. The optimal conditions were as follows: the dilution volume of hexane was 5 mL, the dosage of SWCNTs was 0.6 g, the wash solution was 20 mL hexane, and the elution solution was 5 mL toluene. The six PAEs had a good linear range from 0.05 mg/L to 1.0 mg/L, with the correlation coefficients (r) all above 0.999 9. The average recoveries of the six targets in spiked camellia oil (from 0.05 mg/kg to 1.0 mg/kg) ranged from 86.4% to 111.7% with the relative standard deviations (RSDs) from 4.2% to 10.4%. The developed method is accurate, quick and suitable for the determination of the six PAEs in camellia oil. PMID:25255566

  11. Determination of phthalate esters at trace level from environmental water samples by magnetic solid-phase extraction with Fe@SiO2@polyethyleneimine magnetic nanoparticles as adsorbent prior to high-performance liquid chromatography.

    PubMed

    Zhou, Qingxiang; Zheng, Zhenwen; Xiao, Junping; Fan, Huili; Yan, Xiuyi

    2016-07-01

    In this work, polyethyleneimine grafted silica-coated nanoscale zero valent iron (Fe@SiO2@PEI) has been successfully synthesized and was investigated to be an effective adsorbent for efficient enrichment of five phthalate esters such as diphenyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, diphenyl isophthalate, and dicyclohexyl phthalate (DPP, DBP, BBP, DPIP, and DCHP) from environmental water samples. The structure and morphology of the materials were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction(XRD). The parameters that influenced the enrichment performance such as amount of sorbent, sample pH, type of eluent, volume of eluent, salting-out effect, adsorption time, and desorption time were investigated. Under optimal conditions, excellent linear relationships were found in the concentration range from 0.5 to 100 μg L(-1), the limits of detection (S/N = 3) were in the range of 0.26-0.45 μg L(-1), and the intra-day and inter-day precisions (n = 6) were in the range of 3.7-4.8 and 3.2-4.3 %, respectively. The developed method was evaluated with real water samples, and satisfied spiked recoveries in the range of 99-104 % were achieved. The experimental results proved that Fe@SiO2@PEI had good adsorption for phthalate esters, and would be a good adsorbent for the magnetic solid-phase extraction of important pollutants from environmental water samples.ᅟ Graphical abstract A flowchart of the synthesis of polyethyleneimine grafted silica coated nanoscale zero valent iron (Fe@SiO2@PEI) and the process of the developed magnetic solid phase extraction of phthalate esters before the analysis by high performance liquid chromatography. PMID:27178558

  12. Novel Phase Transitions in the Breathing Pyrochlore Lattice: Li7-NMR on LiInCr4O8 and LiGaCr4O8

    NASA Astrophysics Data System (ADS)

    Tanaka, Yu; Yoshida, Makoto; Takigawa, Masashi; Okamoto, Yoshihiko; Hiroi, Zenji

    2014-11-01

    We report Li7-NMR studies on LiInCr4O8 and LiGaCr4O8, in which Cr3 + ions with spin 3 /2 form a breathing pyrochlore lattice, a network of tetrahedra with alternating sizes. In LiInCr4O8 with large alternation, the nuclear relaxation rate 1 /T1 shows an activated temperature (T ) dependence down to 18 K, indicating a singlet ground state with a spin gap. This behavior, however, is disrupted by an antiferromagnetic transition at 13 K, which is preceded by another, most likely structural, transition at 16 K. In contrast, LiGaCr4O8 with a small alternation shows no spin gap but exhibits a first-order antiferromagnetic transition over a distributed T range 13-20 K. Nevertheless, 1 /T1 of the paramagnetic phase diverges toward 13 K, indicating proximity to a second-order transition. The results indicate that LiGaCr4O8 is located in the vicinity of a tricritical point in the phase diagram.

  13. Toward a structure determination method for biomineral-associated protein using combined solid-state NMR and computational structure prediction

    PubMed Central

    Masica, David L.; Ash, Jason T.; Ndao, Moise; Drobny, Gary P.; Gray, Jeffrey J

    2010-01-01

    Summary Protein-biomineral interactions are paramount to materials production in biology, including the mineral phase of hard tissue. Unfortunately, the structure of biomineral-associated proteins cannot be determined by X-ray crystallography or solution NMR. Here we report a method for determining the structure of biomineral-associated proteins. The method combines solid-state NMR (ssNMR) and ssNMR-biased computational structure prediction. In addition, the algorithm is able to identify lattice geometries most compatible with ssNMR constraints, representing a quantitative, novel method for investigating crystal-face binding specificity. We use this new method to determine most of the structure of human salivary statherin interacting with the mineral phase of tooth enamel. Computation and experiment converge on an ensemble of related structures and identify preferential binding at three crystal surfaces. The work represents a significant advance toward determining structure of biomineral-adsorbed protein using experimentally biased structure prediction. This method is generally applicable to proteins that can be chemically synthesized. PMID:21134646

  14. In situ microscopic studies on the structures and phase behaviors of SF/PEG films using solid-state NMR and Raman imaging.

    PubMed

    Chen, Congheng; Yao, Ting; Tu, Sidong; Xu, Weijie; Han, Yi; Zhou, Ping

    2016-06-28

    In order to overcome the drawbacks of silk fibroin (SF)-based materials, SF has been blended with some polymers. Before using the blend material, understanding of the structures and phase behaviors of the blend is thought to be essential. In this study, solid-state (13)C CP-MAS NMR and Raman imaging techniques were used to study the structures and phase behaviors of blends of SF with polyethylene glycol (PEG) at a molecular weight that varied from 2 to 20 kDa and a blend ratio of SF/PEG from 95/5 to 70/30 (w/w%) at the molecular and microscopic levels. It is found that the conformational transition of SF to the β-sheet increased as the PEG content increased, while the amount of the formed β-sheet conformers was decreased as the PEG molecular weight increased for a given content. It is also observed that SF was incompatible with PEG to some extent. The phase separation into "sea" and "island" domains took place in the SF/PEG blend films. SF was dominantly present in the "sea" domain, while PEG in the "island" domains. The conformation of SF in the interface between SF and PEG was changed to the β-sheet, while that in the protein-rich domain remained in the random coil and/or helix conformation. These observations suggest that the specifically expected materials, for example, the silk-based microspheres or scaffold materials can be manufactured by controlling the molecular weight and content of PEG in the blend system. PMID:27255417

  15. Phosphate-water interplay tunes amorphous calcium carbonate metastability: spontaneous phase separation and crystallization vs stabilization viewed by solid state NMR.

    PubMed

    Kababya, Shifi; Gal, Assaf; Kahil, Keren; Weiner, Steve; Addadi, Lia; Schmidt, Asher

    2015-01-21

    Organisms tune the metastability of amorphous calcium carbonates (ACC), often by incorporation of additives such as phosphate ions and water molecules, to serve diverse functions, such as modulating the availability of calcium reserves or constructing complex skeletal scaffolds. Although the effect of additive distribution on ACC was noted for several biogenic and synthetic systems, the molecular mechanisms by which additives govern ACC stability are not well understood. By precipitating ACC in the presence of different PO4(3-) concentrations and regulating the initial water content, we identify conditions yielding either kinetically locked or spontaneously transforming coprecipitates. Solid state NMR, supported by FTIR, XRD, and electron microscopy, define the interactions of phosphate and water within the initial amorphous matrix, showing that initially the coprecipitates are homogeneous molecular dispersions of structural water and phosphate in ACC, and a small fraction of P-rich phases. Monitoring the transformations of the homogeneous phase shows that PO4(3-) and waters are extracted first, and they phase separate, leading to solid-solid transformation of ACC to calcite; small part of ACC forms vaterite that subsequently converts to calcite. The simultaneous water-PO4(3-) extraction is the key for the subsequent water-mediated accumulation and crystallization of hydroxyapatite (HAp) and carbonated hydroxyapatite. The thermodynamic driving force for the transformations is calcite crystallization, yet it is gated by specific combinations of water-phosphate levels in the initial amorphous coprecipitates. The molecular details of the spontaneously transforming ACC and of the stabilized ACC modulated by phosphate and water at ambient conditions, provide insight into biogenic and biomimetic pathways. PMID:25523637

  16. Using multi-walled carbon nanotubes as solid phase extraction adsorbents to determine dichlorodiphenyltrichloroethane and its metabolites at trace level in water samples by high performance liquid chromatography with UV detection.

    PubMed

    Zhou, Qingxiang; Xiao, Junping; Wang, Weidong

    2006-09-01

    Carbon nanotubes (CNTs) are a kind of new carbon-based nano-materials which have drawn great attention in many application fields. The potential of multi-walled carbon nanotubes (MWNTs) as solid-phase extraction (SPE) adsorbents for the preconcentration of environmental pollutants has been investigated in recent years. The goal of this work was to investigate the feasibility of MWNTs used as SPE adsorbents to enrich dichlorodiphenyltrichloroethane (DDT) and its metabolites including 1,1-dichloro-2,2-bis-(4'-chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis-(4'-chlorophenyl)ethane (DDE) at trace level which are typical persistent organic pollutants in environment. Parameters that maybe influence the extraction efficiency such as the eluent volume, sample flow rate, sample pH and the sample volume were optimized in detail. The experimental results showed the excellent linear relationship between peak area and the concentration of DDT and its metabolites over the range of 0.2-60 microg L(-1), and the precisions (RSD) were 2.3-2.5% under the optimal conditions. The detection limits of proposed method could reach 4-13 ng L(-1) based on the ratio of chromatographic signal to base line noise (S/N = 3). Satisfied results were achieved when the proposed method was applied to determine the four target compounds in realworld water samples with spiked recoveries over the range of 89.7-115.5%. All these facts indicated that MWCNTs as SPE packing materials coupled to HPLC was an excellent alternative for the routine analysis of DDT and its metabolites at trace level in environment. PMID:16797570

  17. Three-dimensional graphene aerogel-supported iron oxide nanoparticles as an efficient adsorbent for magnetic solid phase extraction of organophosphorus pesticide residues in fruit juices followed by gas chromatographic determination.

    PubMed

    Mahpishanian, Shokouh; Sereshti, Hassan

    2016-04-22

    In this research, a magnetic three dimensional-graphene nanocomposite (3D-G-Fe3O4) was prepared, characterized and used as an effective nanoadsorbent in magnetic solid-phase extraction (MSPE) of eight organophosphorus pesticides (OPPs) from juice samples prior to gas chromatography-nitrogen phosphorous detection (GC-NPD). The properties and morphology of 3D-G-Fe3O4 were characterized by scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR) and vibrating sample magnetometry (VSM). The main experimental parameters affecting extraction recoveries including extraction time, amount of adsorbent, pH of sample solution, salt concentration and desorption conditions were carefully studied and optimized. The results showed wide linear concentration ranges with determination coefficients between 0.9973 and 0.9999. The limits of detection (S/N=3) of the method and limits of quantification (S/N=10) were from 1.2 to 5.1 ng L(-1) and 3.4-17.0 ng L(-1), respectively. The intra-day and inter-day RSDs were 2.6-5.1% and 3.5-6.9%, respectively. The method was successfully applied to the analysis of OPPs in fruit juices (apple, orange, grape, sour-cherry and apricot) with recoveries in range of 86.6-107.5%. The GC-NPD results were confirmed by gas chromatography-mass spectrometry (GC-MS). The results demonstrated that with combination of highly interconnected 3D network structure and magnetism property of adsorbent, 3D-G-Fe3O4 aerogel exhibited exceptional extraction ability towards the OPPs. PMID:27018186

  18. NMR study of the magnetization of superfluid helium-3-boron and NMR of superfluid helium-3 in aerogel

    NASA Astrophysics Data System (ADS)

    Haard, Thomas Michael

    Pulsed NMR measurements of superfluid 3He confined in 98.2% porosity silica aerogel are reported. The aerogel suppressed the superfluid transition temperature TC and the order parameter magnitude from their bulk values in qualitative agreement with impurity scattering models. Magnetization measurements showed that the superfluid is an equal spin pairing state (ESP). The superfluid exhibited positive NMR frequency shifts with similar temperature dependence to those of the bulk A-phase, only smaller. TC was independent of the magnetic field for H < 1.8 kOe to within the experimental error. At 2.18 kOe an increased suppression of TC and the order parameter was observed. Two layers of solid 3He were adsorbed to the aerogel strands. When these were replaced with solid 4He a non-ESP superfluid state was observed. An experimental cell for measuring the heat capacity of 3He in aerogel was designed and fabricated. It was tested without aerogel by measuring the heat capacity of liquid 3He over a range of temperatures from 1 to 25 mK and at pressures of 7.0, 14.0, and 28.0 bar. The measurements in both the normal and superfluid phases were consistent with the data of Greywall. The discrepancy between static and dynamic measurements of the magnetization of superfluid 3He-B was characterized over a region of the phase diagram by comparison of nuclear magnetic resonance (NMR) data and recent SQUID data from other researchers. At the B- to A-phase transition, TAB, the discrepancy was absent at low pressure, but increased to 20% at 26.6 bar and 1.2 kOe. The NMR data were consistent with the weak-coupling-plus (wcp) theory at TAB for most pressures and fields. The Ginzburg-Landau strong-coupling parameter gz/( gz)wcp was determined from NMR results to equal 1.00 +/- 0.03 for all pressures. Combinations of the Ginzburg-Landau beta-parameters are reported that are consistent with this observation.

  19. Nuclear spin heat capacity of 3He adsorbed on graphite

    NASA Astrophysics Data System (ADS)

    Greywall, Dennis S.

    1989-10-01

    The heat capacity of 3He adsorbed on graphite has been measured for films between one and five atomic layers and for temperatures between 2 and 200 mK. These results are compared with recent magnetization data which also show several anomalies in this coverage regime. Prior to third layer promotion the second layer is found to solidify into a registered structure with unusual propertis. This contradicts the model proposed to explain the NMR measurements.

  20. High Resolution 15N NMR of the 225 K Phase Transition of Ammonia Borane (NH3BH3): Mixed Order-Disorder and Displacive Behavior

    SciTech Connect

    Gunaydin-Sen, Ozge; Achey, Randall; Dalal, Nar S.; Stowe, Ashley C.; Autrey, Thomas

    2007-02-01

    We report high resolution 15N NMR probing of the solid-solid phase transition of 15N-labeled ammonia borane (NH3BH3) around 225 K. Both the 15N isotropic chemical shift, δiso, and the spin-lattice relaxation rate (T1-1) exhibited strong anomalies around 225 K. The analysis of T1-1 using the Bloembergen-Purcell and Pound model showed that the motional correlation time, τ, increased from about 1 ps to 100 ps while the corresponding Arrhenius activation energy increased from 6 to 13.4 kJ/mol on going through the transition. The observed strong temperature dependence of δiso was interpreted by an extension of the Bayer model. The time scale of the underlying motion was found to be in a reasonable agreement with the T1-1 data. These results imply that the NH3 rotor motion plays a pivotal role in the transition mechanism, and that the transition is of both order-disorder and displacive type. This work was supported by the Office of Basic Energy Sciences of the U. S. Department of Energy Chemical Sciences program. Pacific Northwest National Laboratory is operated by Battelle for the U. S. Department of Energy.

  1. Synthesis of metronidazole-imprinted molecularly imprinted polymers by distillation precipitation polymerization and their use as a solid-phase adsorbent and chromatographic filler.

    PubMed

    Liu, Jiang; Zhang, Lu; Li Han Song, Le; Liu, Yuan; Tang, Hui; Li, Yingchun

    2015-04-01

    Metronidazole-imprinted polymers with superior recognition properties were prepared by a novel strategy called distillation-precipitation polymerization. The as-obtained polymers were characterized by Fourier-transform infrared spectroscopy, laser particle size determination and scanning electron microscopy, and their binding performances were evaluated in detail by static, kinetic and dynamic rebinding tests, and Scatchard analysis. The results showed that when the fraction of the monomers was 5 vol% in the whole reaction system, the prepared polymers afforded good morphology, monodispersity, and high adsorption capacity and excellent selectivity to the target molecule, metronidazole. The optimal binding performance is 12.41 mg/g for metronidazole just before leakage occurred and 38.51 mg/g at saturation in dynamic rebinding tests. Metronidazole-imprinted polymers were further applied as packing agents in solid-phase extraction and as chromatographic filler, both of which served for the detection of metronidazole in fish tissue. The results illustrated the recoveries of spiked samples ranged from 82.97 to 87.83% by using molecularly imprinted solid-phase extraction combined with a C18 commercial column and 93.7 to 101.2% by directly using the polymer-packed chromatographic column. The relative standard deviation of both methods was less than 6%. PMID:25594306

  2. Distribution of metal and adsorbed guest species in zeolites

    SciTech Connect

    Chmelka, B.F.

    1989-12-01

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

  3. NMR relaxation study of the phase transitions and relaxation mechanisms of the alums MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) single crystals

    SciTech Connect

    Lim, Ae Ran; Paik, Younkee; Lim, Kye-Young

    2011-06-15

    The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) single crystals have been investigated. The phase transition temperatures, NMR spectra, and the spin-lattice relaxation times T{sub 1} of the {sup 87}Rb and {sup 133}Cs nuclei in the two crystals were determined using DSC and FT NMR spectroscopy. The resonance lines and relaxation times of the {sup 87}Rb and {sup 133}Cs nuclei undergo significant changes at the phase transition temperatures. The sudden changes in the splitting of the Rb and Cs resonance lines are attributed to changes in the local symmetry of their sites, and the changes in the temperature dependences of T{sub 1} are related to variations in the symmetry of the octahedra of water molecules surrounding Rb{sup +} and Cs{sup +}. We also compared these {sup 87}Rb and {sup 133}Cs NMR results with those obtained for the trivalent cations Cr and Al in MCr(SO{sub 4}){sub 2}.12H{sub 2}O and MAl(SO{sub 4}){sub 2}.12H{sub 2}O crystals. - Graphical Abstract: The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb, Cs, and NH{sub 4}) single crystals have been investigated. Highlights: > The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) crystals {yields} The NMR spectra and the spin-lattice relaxation times T{sub 1} of the {sup 87}Rb and {sup 133}Cs nuclei in the two crystals {yields} The variations in the symmetry of the octahedra of water molecules surrounding Rb{sup +} and Cs{sup +}.

  4. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Hou, Guangjin; Lu, Xingyu; Vega, Alexander J.; Polenova, Tatyana

    2014-09-01

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear 1H-X (X = 13C, 15N, 31P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the 1H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the 1H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from 1H chemical shift anisotropy, while keeping the 1H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [15N]-N-acetyl-valine and [U-13C,15N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate 1H-15N dipolar couplings in the context of 3D experiments is presented on U-13C,15N-enriched dynein light chain protein LC8.

  5. Phospholipids chiral at phosphorus. Dramatic effects of phosphorus chirality on the deuterium NMR properties of the choline head group of phospholipids in the liquid crystalline phase

    SciTech Connect

    Loffredo, W.M.; Jiang, Rutai; Tsai, Mingdaw )

    1990-12-01

    To probe the motional and conformational propertis of the choline head group of 1,2-dipalmitoyl-sn-glycero-3-thiophosphocholine (DPPsC), the R{sub p}, S{sub p}, and R{sub p} {plus} S{sub p} isomers of ({alpha}-D{sub 2})DPPsC, ({beta}-D{sub 2})DPPsC, and ({delta}-D{sub 9})DPPsC in the subgel, gel, and liquid crystalline phases were investigated with deuterium NMR, and the results were compared with those of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) labeled at the same positions. In the subgel phase (5 {degree}C) all isomers of ({alpha}-D{sub 2})DPPsC and ({beta}-D{sub 2})DPPsC displayed amorphous line shapes characteristic of a restricted and disordered motional environment, whereas ({delta}-D{sub 9})DPPsC showed narrower and symmetric line shapes indicating substantial motions. For all three labeled positions the apparent line width of the R{sub p} isomer is larger than those of S{sub p} and R{sub p} {plus} S{sub p} isomers, and the amorphous line shape of the R{sub p} isomer also persists at 25 and 35{degree}C. These results indicate that the motional and conformational properties of the C{sub {alpha}}-C{sub {beta}} segment of DPPsC is very sensitive to the configuration at phosphorus. Structurally, this provides strong support for noncovalent interactions between the quaternary ammonium group of choline and the phosphate group of a neighboring molecule in the bilayers of phosphatidylcholine and suggests that such interactions are important to the motion of the choline chain.

  6. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    SciTech Connect

    Hou, Guangjin E-mail: tpolenov@udel.edu; Lu, Xingyu E-mail: lexvega@comcast.net; Vega, Alexander J. E-mail: lexvega@comcast.net; Polenova, Tatyana E-mail: tpolenov@udel.edu

    2014-09-14

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear {sup 1}H-X (X = {sup 13}C, {sup 15}N, {sup 31}P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the {sup 1}H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the {sup 1}H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from {sup 1}H chemical shift anisotropy, while keeping the {sup 1}H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [{sup 15}N]-N-acetyl-valine and [U-{sup 13}C,{sup 15}N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate {sup 1}H-{sup 15}N dipolar couplings in the context of 3D experiments is presented on U-{sup 13}C,{sup 15}N-enriched dynein light chain protein LC8.

  7. Dynamics of the Chiral Liquid Crystal 4'-Butyl-4-(S)-(2-methylbutoxy)azoxybenzene in the Isotropic, Cholesteric, and Solid Phases: A Fast Field-Cycling NMR Relaxometry Study.

    PubMed

    Carignani, Elisa; Calucci, Lucia; Juszyńska-Gałązka, Ewa; Gałązka, Mirosław; Massalska-Arodź, Maria; Forte, Claudia; Geppi, Marco

    2016-06-01

    (1)H NMR relaxometry was applied to investigate dynamic processes in the isotropic liquid, cholesteric, and crystalline phases of the chiral mesogen 4'-butyl-4-(S)-(2-methylbutoxy)azoxybenzene (4ABO5*). To this aim, (1)H longitudinal relaxation rates were measured as a function of temperature (between 257 and 319 K) and Larmor frequency (from 10 kHz to 35 MHz by a fast field-cycling relaxometer and at 400 MHz by an NMR spectrometer). The NMR relaxation dispersion (NMRD) curves so obtained were analyzed in terms of models suitable for the description of dynamic processes in the different phases, thus quantitatively determining values of characteristic motional parameters. In particular, internal and overall rotations/reorientations, molecular translational diffusion, and collective motions contribute to relaxation in the isotropic and cholesteric phases, whereas, in the crystalline phase, relaxation is mainly determined by internal motions and molecular reorientations. The results were discussed and compared with those previously obtained on the same compound by dielectric relaxation spectroscopy. PMID:27186864

  8. Decoherence of many-spin systems in NMR: From molecular characterization to an environmentally induced quantum dynamical phase transition

    NASA Astrophysics Data System (ADS)

    Alvarez, Gonzalo A.

    2007-05-01

    The control of open quantum systems has a fundamental relevance for fields ranging from quantum information processing to nanotechnology. Typically, the system whose coherent dynamics one wants to manipulate, interacts with an environment that smoothly degrades its quantum dynamics. Thus, a precise understanding of the inner mechanisms of this process, called "decoherence", is critical to develop strategies to control the quantum dynamics. In this thesis we solved the generalized Liouville-von Neumann quantum master equation to obtain the dynamics of many-spin systems interacting with a spin bath. We also solve the spin dynamics within the Keldysh formalism. Both methods lead to identical solutions and together gave us the possibility to obtain numerous physical predictions that contrast well with Nuclear Magnetic Resonance experiments. We applied these tools for molecular characterizations, development of new numerical methodologies and the control of quantum dynamics in experimental implementations. But, more important, these results contributed to fundamental physical interpretations of how quantum dynamics behaves in open systems. In particular, we found a manifestation of an environmentally induced quantum dynamical phase transition.

  9. Silver nanoparticles attached to silica gel as a new solid phase adsorbent for preconcentration and determination of iron from biological samples

    NASA Astrophysics Data System (ADS)

    Khajeh, Mostafa; Dastafkan, Kamran

    2012-11-01

    In this study, an easy and fast procedure based on solid phase extraction was developed that is intended to pre-concentrate, separate, and determine trace amounts of Fe(III) ions in biological samples using flame atomic absorption spectrometry (FAAS). Silver nanoparticles coated with silica gel were modified by morin and then used as a sorbent. It was synthesized by mixing slurried silica gel with silver nitrate and sodium citrate. The effects of experimental conditions, including pH, sample and eluent flow rates, and the type and least amount of an eluent to the elute iron from the sorbent were studied, and optimum values of these parameters have been found. Under the optimum conditions, the limit of detection of this procedure for Fe(III) was 67 ng/l. The relative standard deviation (RSD%) was 2.5 % (n = 10, C = 0.5 mg/l). The developed procedure was used to determine iron in biological samples.

  10. Evaluation of multi-walled carbon nanotubes as solid-phase extraction adsorbents of pesticides from agricultural, ornamental and forestal soils.

    PubMed

    Asensio-Ramos, M; Hernández-Borges, J; Borges-Miquel, T M; Rodríguez-Delgado, M A

    2009-08-11

    A new, simple and cost-effective method based on the use of multi-walled carbon nanotubes (MWCNTs) as solid-phase extraction stationary phases is proposed for the determination of a group of seven organophosphorus pesticides (i.e. ethoprophos, diazinon, chlorpyriphos-methyl, fenitrothion, malathion, chlorpyriphos and phosmet) and one thiadiazine (buprofezin) in different kinds of soil samples (forestal, ornamental and agricultural) using gas chromatography with nitrogen phosphorus detection. Soils were first ultrasound extracted with 10 mL 1:1 methanol/acetonitrile (v/v) and the evaporated extract redissolved in 20 mL water (pH 6.0) was passed through 100 mg of MWCNTs of 10-15 nm o.d., 2-6 nm i.d. and 0.1-10 microm length. Elution was carried out with 20 mL dichloromethane. The method was validated in terms of linearity, precision, recovery, accuracy and selectivity. Matrix-matched calibration was carried out for each type of soil since statistical differences between the calibration curves constructed in pure solvent and in the reconstituted soil extract were found for most of the pesticides under study. Recovery values of spiked samples ranged between 54 and 91% for the three types of soils (limits of detection (LODs) between 2.97 and 9.49 ngg(-1)), except for chlorpyrifos, chlorpyrifos-methyl and buprofezin which ranged between 12 and 54% (LODs between 3.14 and 72.4 ngg(-1)), which are the pesticides with the highest soil organic carbon sorption coefficient (K(OC)) values. Using a one-sample test (Student's t-test) with fortified samples at two concentration levels in each type of soil, no significant differences were observed between the real and the experimental values (accuracy percentages ranged between 87 and 117%). It is the first time that the adsorptive potential of MWCNTs for the extraction of organophosphorus pesticides from soils is investigated. PMID:19591701

  11. Phase separation, clustering, and fractal characteristics in glass: A magic-angle-spinning NMR spin-lattice relaxation study

    NASA Astrophysics Data System (ADS)

    Sen, S.; Stebbins, J. F.

    1994-07-01

    A comparative study of the 29Si spin-lattice relaxation behavior (induced by trace amounts of paramagnetic dopants in the glass) in phase-separated Li2Si4O9 and monophasic Li2Si2O5 and Na2Si2O5 glasses has been made in order to understand the nature of clustering and the resulting intermediate-range ordering. Optically clear tetrasilicate and disilicate glasses were prepared with 500 to 2000 ppm of Gd2O3, a paramagnetic dopant. The constituent structural units (Q3 and Q4 species) in all tetrasilicate glasses show strong differential relaxation following a power-law behavior. This is due to preferential partitioning of Gd3+ into the lower silica (Q3-rich) regions of these glasses, indicating the presence of Q species clusters too small to produce optical opalescence (a few nm to perhaps tens of nm). Preliminary results on 6Li spin-lattice relaxation in these glasses support this hypothesis. Differential relaxation becomes more pronounced on annealing due to growth of such clusters. No such differential relaxation was observed in the monophase disilicate glasses. For spin-lattice relaxation induced by direct dipolar coupling to paramagnetic ions, the recovery of magnetization is proportional to time as M(t)~tα where α is a function of the dimensionality D of mass distribution of the constituent Q species around the Gd3+ paramagnetic centers in the glass. For tetrasilicate glasses D~=2.62+/-0.22 and the system behaves as a mass fractal up to a length scale of 2 to 3 nm. D is thus equal to, within error, the theoretical value of 2.6 for an infinite percolation cluster of one type of Q species in another. For disilicate glasses, D~=3.06+/-0.18 which indicates a three-dimensional (and thus nonfractal) mass distribution of the constituent Q species over the same length scale.

  12. Capillary electrophoresis combined in-line with solid-phase extraction using magnetic particles as new adsorbents for the determination of drugs of abuse in human urine.

    PubMed

    Baciu, Tatiana; Borrull, Francesc; Neusüß, Christian; Aguilar, Carme; Calull, Marta

    2016-05-01

    A simple approach is presented based on the in-line coupling between magnetic particles-based SPE and CE. Silica-coated iron oxide particles functionalized with C18 were successfully synthesized and used as a reverse-phase sorbent for in-line SPE-CE. Magnets were used to locally immobilize these sorbents inside the capillary. Four drugs of abuse were preconcentrated and determined in urine samples using the developed method with a simple pretreatment procedure based on LLE. Several parameters affecting the preconcentration were evaluated. The obtained results show that this strategy enhanced detection sensitivity in the range of 125-700-fold compared with CE without preconcentration. The developed method provides LODs (S/N = 3) for standard samples in the range of 0.5-20 ng/mL with satisfactory analytical precision, in both intraday and day-to-day experiments (RSDs <20%). The LODs (S/N = 3) reached for urine samples were in the range of 20-50 ng/mL. Relative recoveries greater than 75.9% were obtained. The established method has been applied to the analysis of drugs of abuse in urine samples from drug abusers. PMID:26856766

  13. Determination of ibuprofen, naproxen and diclofenac in aqueous samples using a multi-template molecularly imprinted polymer as selective adsorbent for solid-phase extraction.

    PubMed

    Madikizela, Lawrence Mzukisi; Chimuka, Luke

    2016-09-01

    This study describes the application of multi-template molecularly imprinted polymer (MIP) as selective sorbent in the solid-phase extraction (SPE) of naproxen, ibuprofen and diclofenac from wastewater and river water. MIP was synthesized at 70°C by employing naproxen, ibuprofen and diclofenac as multi-templates, ethylene glycol dimethacrylate, 2-vinyl pyridine and toluene as cross-linker, functional monomer and porogen, respectively. Wastewater and river water samples (pH 2.5) were percolated through SPE cartridge packed with 50mg of the MIP. The cartridge was washed with 2mL of methanol-water 10:90% (v:v) prior to elution with 2mL of acetic acid-acetonitrile 20:80% (v:v). Quantification of eluted compounds was performed with high performance liquid chromatography equipped with photo diode array detection. The detection limits were 0.15, 1.00 and 0.63μgL(-1) for naproxen, ibuprofen and diclofenac, respectively. Recoveries for naproxen, ibuprofen and diclofenac in deionized water spiked at 5 and 50μgL(-1) were greater than 80%. Ibuprofen was the most frequently detected compound with maximum concentrations of 221, 67.9 and 11.4μgL(-1) in wastewater influent, effluent and river water, respectively. PMID:27268945

  14. In Situ Synthesis of Porous Carbons by Using Room-Temperature, Atmospheric-Pressure Dielectric Barrier Discharge Plasma as High-Performance Adsorbents for Solid-Phase Microextraction.

    PubMed

    Lin, Yao; Wu, Li; Xu, Kailai; Tian, Yunfei; Hou, Xiandeng; Zheng, Chengbin

    2015-09-21

    A one-step, template-free method is described to synthesize porous carbons (PCs) in situ on a metal surface by using a room-temperature, atmospheric-pressure dielectric barrier discharge (DBD) plasma. This method not only features high efficiency, environmentally friendliness, and low cost and simple equipment, but also can conveniently realize large-area synthesis of PCs by only changing the design of the DBD reactor. The synthesized PCs have a regulated nestlike morphology, and thus, provide a high specific surface area and high pore volume, which result in excellent adsorption properties. Its applicability was demonstrated by using a PC-coated stainless-steel fiber as a solid-phase microextraction (SPME) fiber to preconcentrate polycyclic aromatic hydrocarbons (PAHs) prior to analysis by gas chromatography with flame ionization detection (GC-FID). The results showed that the fiber exhibited excellent enrichment factors (4.1×10(4) to 3.1×10(5)) toward all tested PAHs. Thus, the PC-based SPME-GC-FID provides low limits of detection (2 to 20 ng L(-1)), good precision (<7.8%), and good recoveries (80-115%) for ultra-sensitive determination of PAHs in real water samples. In addition, the PC-coated fiber could be stable enough for more than 500 replicate extraction cycles. PMID:26267394

  15. Coordination polymer adsorbent for matrix solid-phase dispersion extraction of pesticides during analysis of dehydrated Hyptis pectinata medicinal plant by GC/MS.

    PubMed

    Aquino, Adriano; Wanderley, Kaline A; Paiva-Santos, Carlos de Oliveira; de Sá, Gilberto F; Alexandre, Marcelo da R; Júnior, Severino A; Navickiene, Sandro

    2010-12-15

    The coordination polymer [Zn(BDC)(H(2)O)(2)](n) was tested for extraction of pyrimethanil, ametryn, dichlofluanid, tetraconazole, flumetralin, kresoxim-methyl and tebuconazole from the medicinal plant Hyptis pectinata, with analysis using gas chromatography-mass spectrometry in selected ion monitoring mode (GC/MS, SIM). Experiments carried out at different fortification levels (0.1, 0.5 and 1.0 μg g(-1)) resulted in recoveries in the range 73-97%, and RSD values were between 5 and 12% for the [Zn(BDC)(H(2)O)(2)](n) sorbent. Detection and quantification limits ranged from 0.02 to 0.07 μg g(-1) and from 0.05 to 0.1 μg g(-1), respectively, for the different pesticides studied. The method developed was linear over the range tested (0.04-14.0 μg g(-1)), with correlation coefficients ranging from 0.9987 to 0.9998. Comparison between [Zn(BDC)(H(2)O)(2)](n) and the commercial phase C(18)-bonded silica showed good performance of the [Zn(BDC)(H(2)O)(2)](n) polymeric sorbent for the pesticides tested. PMID:21111184

  16. Development and Testing of Molecular Adsorber Coatings

    NASA Technical Reports Server (NTRS)

    Abraham, Nithin; Hasegawa, Mark; Straka, Sharon

    2012-01-01

    The effect of on-orbit molecular contamination has the potential to degrade the performance of spaceflight hardware and diminish the lifetime of the spacecraft. For example, sensitive surfaces, such as optical surfaces, electronics, detectors, and thermal control surfaces, are vulnerable to the damaging effects of contamination from outgassed materials. The current solution to protect these surfaces is through the use of zeolite coated ceramic adsorber pucks. However, these pucks and its additional complex mounting hardware requirements result in several disadvantages, such as size, weight, and cost related concerns, that impact the spacecraft design and the integration and test schedule. As a result, a new innovative molecular adsorber coating was developed as a sprayable alternative to mitigate the risk of on-orbit molecular contamination. In this study, the formulation for molecular adsorber coatings was optimized using various binders, pigment treatment methods, binder to pigment ratios, thicknesses, and spray application techniques. The formulations that passed coating adhesion and vacuum thermal cycling tests were further tested for its adsorptive capacity. Accelerated molecular capacitance tests were performed in an innovatively designed multi-unit system containing idealized contaminant sources. This novel system significantly increased the productivity of the testing phase for the various formulations that were developed. Work performed during the development and testing phases has demonstrated successful application of molecular adsorber coatings onto metallic substrates, as well as, very promising results for the adhesion performance and the molecular capacitance of the coating. Continued testing will assist in the qualification of molecular adsorber coatings for use on future contamination sensitive spaceflight missions.

  17. Sol-gel approach for fabrication of coated anodized titanium wire for solid-phase microextraction: highly efficient adsorbents for enrichment of trace polar analytes.

    PubMed

    Jia, Jing; Xu, Lili; Wang, Shuai; Wang, Licheng; Liu, Xia

    2014-05-01

    Nanotubular titania film was prepared in situ on titanium wire and was used as the fiber substrate for solid-phase microextraction (SPME) because of its high surface-to-volume ratio, easy preparation, and mechanical stability. Three different functional coatings, β-cyclodextrin (β-CD), β-cyclodextrin-co-poly(ethylenepropylene glycol) (β-CD/PEG), and polyethylene glycol (PEG)-based sorbents were chemically bonded to the nanostructured wire surface via sol-gel technology to further enhance the absorbing capability and extraction selectivity. Coupled to gas chromatography-flame ionic detection (GC-FID), the prepared SPME fibers were investigated using diverse compounds. The results indicated that the fibers showed good mechanical strength, excellent thermal stability, and wonderful capacity and selectivity to polar compounds, including polar aromatic compounds, alcohols, and ketones. Combining the superior hydrophilic property of a bonded functional molecule and the highly porous structure of a fiber coating, the prepared PEG-coated SPME fiber showed much higher adsorption affinity to ephedrine and methylephedrine than β-CD and β-CD/PEG fibers. The as-established PEG-coated SPME-GC analytical method provided excellent sensitivity (LODs, 0.004 and 0.001 ng mL(-1) for ephedrine and methylephedrine, respectively) and better linear range (0.01-2 000 μg L(-1)). In addition, it has surprising repeatability and reproducibility. Finally, the present approach was used to analyze ephedrine and methylephedrine from real urine samples, and reliable results were obtained. PMID:24682230

  18. Twist, tilt, and orientational order at the nematic to twist-bend nematic phase transition of 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane: A dielectric, 2H NMR, and calorimetric study

    NASA Astrophysics Data System (ADS)

    Robles-Hernández, Beatriz; Sebastián, Nerea; de la Fuente, M. Rosario; López, David O.; Diez-Berart, Sergio; Salud, Josep; Ros, M. Blanca; Dunmur, David A.; Luckhurst, Geoffrey R.; Timimi, Bakir A.

    2015-12-01

    The nature of the nematic-nematic phase transition in the liquid crystal dimer 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB) has been investigated using techniques of calorimetry, dynamic dielectric response measurements, and 2H NMR spectroscopy. The experimental results for CB9CB show that, like the shorter homologue CB7CB, the studied material exhibits a normal nematic phase, which on cooling undergoes a transition to the twist-bend nematic phase (NTB), a uniaxial nematic phase, promoted by the average bent molecular shape, in which the director tilts and precesses describing a conical helix. Modulated differential scanning calorimetry has been used to analyze the nature of the NTB-N phase transition, which is found to be weakly first order, but close to tricritical. Additionally broadband dielectric spectroscopy and 2H magnetic resonance studies have revealed information on the structural characteristics of the recently discovered twist-bend nematic phase. Analysis of the dynamic dielectric response in both nematic phases has provided an estimate of the conical angle of the heliconical structure for the NTB phase. Capacitance measurements of the electric-field realignment of the director in initially planar aligned cells have yielded values for the splay and bend elastic constants in the high temperature nematic phase. The bend elastic constant is small and decreases with decreasing temperature as the twist-bend phase is approached. This behavior is expected theoretically and has been observed in materials that form the twist-bend nematic phase. 2H NMR measurements characterize the chiral helical twist identified in the twist-bend nematic phase and also allow the determination of the temperature dependence of the conical angle and the orientational order parameter with respect to the director.

  19. NMR studies of multiphase flows II

    SciTech Connect

    Altobelli, S.A.; Caprihan, A.; Fukushima, E.

    1995-12-31

    NMR techniques for measurements of spatial distribution of material phase, velocity and velocity fluctuation are being developed and refined. Versions of these techniques which provide time average liquid fraction and fluid phase velocity have been applied to several concentrated suspension systems which will not be discussed extensively here. Technical developments required to further extend the use of NMR to the multi-phase flow arena and to provide measurements of previously unobtainable parameters are the focus of this report.

  20. [Magnetic multi-walled carbon nanotubes as a solid phase extraction adsorbent for the determination of 13 phthalate acid esters in water samples by gas chromatography-mass spectrometry].

    PubMed

    Fu, Shanliang; Ding, Li; Zhu, Shaohua; Jiao, Yanna; Gong, Qiang; Chen, Jitao; Wang, Libing

    2011-08-01

    A method based on solid phase extraction (SPE) with magnetic multi-walled carbon nanotubes (MWCNTs) as adsorbent was developed for the determination of 13 phthalate acid esters (PAEs) in water samples by gas chromatography-mass spectrometry (GC-MS). The factors affecting the extraction efficiency, such as extraction time, pH of water sample, desorption solvent, and desorption time, were carefully investigated. The optimized conditions were as follows: extraction time, 10 min; pH of water samples, 5 - 7; desorption solvent, 2 mL acetone; desorption time, 5 min. The extraction efficiencies were 89.7% - 100.5% under the optimized conditions. The method was sensitive with the detection limits (S/N = 3) between 0.08 -0.47 microg/L for the 13 PAEs. The developed method was successfully applied for the analysis of tap water, bottle drinking water and lake water, and none of the 13 PAEs was detected. The recoveries ranged from 84.5% to 107.5% for the 3 real spiked samples, and the relative standard deviations were between 1.9% and 12.8%. The developed method has proved convenient, time-saving, accurate, sensitive, and environmental-friendly, and can be used for the determination of PAEs in water samples. PMID:22128736

  1. Simultaneous determination of copper, cobalt, and mercury ions in water samples by solid-phase extraction using carbon nanotube sponges as adsorbent after chelating with sodium diethyldithiocarbamate prior to high performance liquid chromatography.

    PubMed

    Wang, Lei; Zhou, Jia-Bin; Wang, Xia; Wang, Zhen-Hua; Zhao, Ru-Song

    2016-06-01

    Recently, a sponge-like material called carbon nanotube sponges (CNT sponges) has drawn considerable attention because it can remove large-area oil, nanoparticles, and organic dyes from water. In this paper, the feasibility of CNT sponges as a novel solid-phase extraction (SPE) adsorbent for the enrichment and determination of heavy metal ions (Co(2+), Cu(2+), and Hg(2+)) was investigated for the first time. Sodium diethyldithiocarbamate (DDTC) was used as the chelating agent and high performance liquid chromatography (HPLC) for the final analysis. Important factors which may influence extraction efficiency of SPE were optimized, such as the kind and volume of eluent, volume of DDTC, sample pH, flow rate, etc. Under the optimized conditions, wide range of linearity (0.5-400 μg L(-1)), low limits of detection (0.089~0.690 μg L(-1); 0.018~0.138 μg), and good repeatability (1.27~3.60 %, n = 5) were obtained. The developed method was applied for the analysis of the three metal ions in real water samples, and satisfactory results were achieved. All of these findings demonstrated that CNT sponges will be a good choice for the enrichment and determination of target ions at trace levels in the future. PMID:27108287

  2. Application of (13)C ramp CPMAS NMR with phase-adjusted spinning sidebands (PASS) for the quantitative estimation of carbon functional groups in natural organic matter.

    PubMed

    Ikeya, Kosuke; Watanabe, Akira

    2016-01-01

    The composition of carbon (C) functional groups in natural organic matter (NOM), such as dissolved organic matter, soil organic matter, and humic substances, is frequently estimated using solid-state (13)C NMR techniques. A problem associated with quantitative analysis using general cross polarization/magic angle spinning (CPMAS) spectra is the appearance of spinning side bands (SSBs) split from the original center peaks of sp (2) hybridized C species (i.e., aromatic and carbonyl C). Ramp CP/phase-adjusted side band suppressing (PASS) is a pulse sequence that integrates SSBs separately and quantitatively recovers them into their inherent center peaks. In the present study, the applicability of ramp CP/PASS to NOM analysis was compared with direct polarization (DPMAS), another quantitative method but one that requires a long operation time, and/or a ramp CP/total suppression side band (ramp CP/TOSS) technique, a popular but non-quantitative method for deleting SSBs. The test materials were six soil humic acid samples with various known degrees of aromaticity and two fulvic acids. There were no significant differences in the relative abundance of alkyl C, O-alkyl C, and aromatic C between the ramp CP/PASS and DPMAS methods, while the signal intensities corresponding to aromatic C in the ramp CP/TOSS spectra were consistently less than the values obtained in the ramp CP/PASS spectra. These results indicate that ramp CP/PASS can be used to accurately estimate the C composition of NOM samples. PMID:26522329

  3. NMR Relaxometry for the Thermal Stability and Phase Transition Mechanism of Flower-like Micelles from Linear and Cyclic Amphiphilic Block Copolymers.

    PubMed

    Wada, Haruna; Kitazawa, Yu; Kuroki, Shigeki; Tezuka, Yasuyuki; Yamamoto, Takuya

    2015-08-18

    Linear and cyclic amphiphilic block copolymers consisting of poly(ethylene oxide) (PEO) as the hydrophilic segment and poly(methyl acrylate) or poly(ethyl acrylate) as the hydrophobic segments were synthesized and self-assembled to form flower-like micelles. The micelles from linear (methyl acrylate)12(ethylene oxide)73(methyl acrylate)12 (Mn = 1000-3200-1000, l-MOM) showed a cloud point (Tc) at 46 °C by the transmittance of the micellar solution, whereas that of cyclic (methyl acrylate)30(ethylene oxide)79 (Mn = 2600-3500, c-MO) increased to 72 °C, as previously reported. DLS showed comparable diameters (l-MOM, 14 nm; c-MO, 12 nm) and Tc values (l-MOM, 48 °C; c-MO, 75 °C). For the investigation of the difference in Tc and the phase transition mechanism based on the polymer topology, NMR relaxometry was performed to determine the spin-lattice (T1) and spin-spin (T2) relaxation times. A decrease in T2 of the PEO segment in both l-MOM and c-MO was observed above Tc, suggesting that slow large-scale motions, such as the detachment of a chain end from the core, bridging, and interpenetration of the micelles, were inhibited. T1 of the PEO segment in l-MOM continuously increased in the experimental temperature range, indicating that the segment is hydrated even above its Tc. On the other hand, that of c-MO reached a ceiling above its Tc, likely due to the prevention of the rotation of the PEO main chain bonds caused by dehydration. Similar results were obtained for linear (ethyl acrylate)8(ethylene oxide)79(ethyl acrylate)8 (Mn = 800-3500-800, l-EOE) and its cyclic (ethyl acrylate)15(ethylene oxide)78 (Mn = 1500-3400, c-EO). PMID:26230670

  4. Proton NMR studies of functionalized nanoparticles in aqueous environments

    NASA Astrophysics Data System (ADS)

    Tataurova, Yulia Nikolaevna

    Nanoscience is an emerging field that can provide potential routes towards addressing critical issues such as clean and sustainable energy, environmental remediation and human health. Specifically, porous nanomaterials, such as zeolites and mesoporous silica, are found in a wide range of applications including catalysis, drug delivery, imaging, environmental protection, and sensing. The characterization of the physical and chemical properties of nanocrystalline materials is essential to the realization of these innovative applications. The great advantage of porous nanocrystals is their increased external surface area that can control their biological, chemical and catalytic activities. Specific functional groups synthesized on the surface of nanoparticles are able to absorb heavy metals from the solution or target disease cells, such as cancer cells. In these studies, three main issues related to functionalized nanomaterials will be addressed through the application of nuclear magnetic resonance (NMR) techniques including: 1) surface composition and structure of functionalized nanocrystalline particles; 2) chemical properties of the guest molecules on the surface of nanomaterials, and 3) adsorption and reactivity of surface bound functional groups. Nuclear magnetic resonance (NMR) is one of the major spectroscopic techniques available for the characterization of molecular structure and conformational dynamics with atomic level detail. This thesis deals with the application of 1H solution state NMR to porous nanomaterial in an aqueous environment. Understanding the aqueous phase behavior of functionalized nanomaterials is a key factor in the design and development of safe nanomaterials because their interactions with living systems are always mediated through the aqueous phase. This is often due to a lack of fundamental knowledge in interfacial chemical and physical phenomena that occur on the surface of nanoparticles. The use of solution NMR spectroscopy results

  5. Adsorbent Alkali Conditioning for Uranium Adsorption from Seawater. Adsorbent Performance and Technology Cost Evaluation

    SciTech Connect

    Tsouris, Costas; Mayes, Richard T.; Janke, Christopher James; Dai, Sheng; Das, S.; Liao, W. -P.; Kuo, Li-Jung; Wood, Jordana; Gill, Gary; Byers, Maggie Flicker; Schneider, Eric

    2015-09-30

    -flow natural seawater at the Pacific Northwest National Laboratory (PNNL). Fourier Transform Infrared (FTIR) spectroscopy, Nuclear Magnetic Resonance (NMR) spectroscopy, Scanning Electron Microscopy (SEM), and elemental analysis were used to characterize the adsorbent at different stages of adsorbent preparation and treatment. The study can be divided into two parts: (A) investigation of optimal parameters for KOH adsorbent conditioning and (B) investigation of other possible agents for alkali conditioning, including cost analysis on the basis of uranium production. In the first part of the study, tests with simulated seawater containing 8 ppm uranium showed that the uranium adsorption capacity increased with an increase in the KOH concentration and conditioning time and temperature at each of the KOH concentrations used. FTIR and solid state NMR studies indicated that KOH conditioning converts the amidoxime functional groups into more hydrophilic carboxylate. The longer the KOH conditioning time, up to three hours, the higher was the loading capacity from the simulated seawater solution which is composed of only uranyl, sodium, chloride, and carbonate ions. Marine testing with natural seawater, on the other hand, showed that the uranium adsorption capacity of the adsorbent increased with KOH conditioning temperature, and gradually decreased with increasing KOH conditioning time from one hour to three hours at 80 C. This behavior is due to the conversion of amidoxime to carboxylate. The carboxylate groups are needed to increase the hydrophilicity of the adsorbent; however, conversion of a significant amount of amidoxime to carboxylate leads to loss in selectivity toward uranyl ions. Thus, there is an optimum KOH conditioning time for each temperature at which an optimum ratio between amidoxime and carboxylate is reached. For the case of base conditioning with 0.44 M KOH at 80 C, the optimal conditioning time is 1 hour, with respect to the highest uranium loading capacity from

  6. Advanced NMR-based techniques for pore structure analysis of coal

    SciTech Connect

    Smith, D.M.

    1992-01-01

    One of the main problems in coal utilization is the inability to properly characterize its complex pore structure. Coals typically have micro/ultra-micro pores but they also exhibit meso and macroporosity. Conventional pore size techniques (adsorption/condensation, mercury porosimetry) are limited because of this broad pore size range, microporosity, reactive nature of coal, samples must be completely dried, and network/percolation effects. Small angle scattering is limited because it probes both open and closed pores. Although one would not expect any single technique to provide a satisfactory description of a coal's structure, it is apparent that better techniques are necessary. We believe that measurement of the NMR parameters of various gas phase and adsorbed phase NMR active probes can provide the resolution to this problem. We will investigate the dependence of the common NMR parameters such as chemical shifts and relaxation times of several different nuclei and compounds on the pore structure of model microporous solids, carbons, and coals. In particular, we will study the interaction between several small molecules and the pore surfaces in coals. These molecules have been selected for their chemical and physical properties. A special NMR probe will be constructed which will allow the concurrent measurement of NMR properties and adsorption uptake at a variety of temperatures. All samples will be subjected to a suite of conventional'' pore structure analyses. These include nitrogen adsorption at 77 K with BET analysis, CO[sub 2] and CH[sub 4] adsorption at 273 K with D-R (Dubinin-Radushkevich) analysis, helium pycnometry, and small angle X-ray scattering as well as gas diffusion measurements.

  7. Advanced NMR-based techniques for pore structure analysis of coal

    SciTech Connect

    Smith, D.M.

    1992-01-01

    One of the main problems in coal utilization is the inability to properly characterize its complex pore structure. Coals typically have micro/ultra-micro pores but they also exhibit meso and macroporosity. Conventional pore size techniques (adsorption/condensation, mercury porosimetry) are limited because of this broad pore size range, microporosity, reactive nature of coal, samples must be completely dried, and network/percolation effects. Small angle scattering is limited because it probes both open and closed pores. Although one would not expect any single technique to provide a satisfactory description of a coal's structure, it is apparent that better techniques are necessary. We believe that measurement of the NMR parameters of various gas phase and adsorbed phase NMR active probes can provide the resolution to this problem. We now have two suites of well-characterized microporous materials including oxides (zeolites and silica gel) and activated carbons from our industrial partner, Air Products in Allentown, PA. Our current work may be divided into three areas: small-angle X-ray scattering (SAXS), adsorption, and NMR.

  8. Adsorbed Water Illustration

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Thermal and Electrical Conductivity Probe on NASA's Phoenix Mars Lander detected small and variable amounts of water in the Martian soil.

    In this schematic illustration, water molecules are represented in red and white; soil minerals are represented in green and blue. The water, neither liquid, vapor, nor solid, adheres in very thin films of molecules to the surfaces of soil minerals. The left half illustrates an interpretation of less water being adsorbed onto the soil-particle surface during a period when the tilt, or obliquity, of Mars' rotation axis is small, as it is in the present. The right half illustrates a thicker film of water during a time when the obliquity is greater, as it is during cycles on time scales of hundreds of thousands of years. As the humidity of the atmosphere increases, more water accumulates on mineral surfaces. Thicker films behave increasingly like liquid water.

    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.

  9. Computer simulations of adsorbed liquid crystal films

    NASA Astrophysics Data System (ADS)

    Wall, Greg D.; Cleaver, Douglas J.

    2003-01-01

    The structures adopted by adsorbed thin films of Gay-Berne particles in the presence of a coexisting vapour phase are investigated by molecular dynamics simulation. The films are adsorbed at a flat substrate which favours planar anchoring, whereas the nematic-vapour interface favours normal alignment. On cooling, a system with a high molecule-substrate interaction strength exhibits substrate-induced planar orientational ordering and considerable stratification is observed in the density profiles. In contrast, a system with weak molecule-substrate coupling adopts a director orientation orthogonal to the substrate plane, owing to the increased influence of the nematic-vapour interface. There are significant differences between the structures adopted at the two interfaces, in contrast with the predictions of density functional treatments of such systems.

  10. Determination and speciation of trace and ultratrace selenium ions by energy-dispersive X-ray fluorescence spectrometry using graphene as solid adsorbent in dispersive micro-solid phase extraction.

    PubMed

    Kocot, Karina; Leardi, Riccardo; Walczak, Beata; Sitko, Rafal

    2015-03-01

    A dispersive micro-solid phase extraction (DMSPE) with graphene as a solid adsorbent and ammonium pyrrolidinedithiocarbamate (APDC) as a chelating agent was proposed for speciation and detemination of inorganic selenium by the energy-dispersive X-ray fluorescence spectrometry (EDXRF). In developed DMSPE, graphene particles are dispersed throughout the analyzed solution, therefore reaction between Se(IV)-APDC complexes and graphene nanoparticles occurs immediately. The concentration of Se(VI) is calculated as the difference between the concentration of selenite after and before prereduction of selenate. A central composite face-centered design with 3 center points was performed in order to optimize conditions and to study the effect of four variables (pH of the sample, concentration of APDC, concentration of Triton-X-100, and sample volume). The best results were obtained when suspension consisting of 200 µg of graphene nanosheets, 1.2 mg of APDC and 0.06 mg of Triton-X-100 was rapidly injected to the 50 mL of the analyzed solution. Under optimized conditions Se ions can be determined with a very good recovery (97.7±5.0% and 99.2±6.6% for Se(IV) and Se(VI), respectively) and precision (RSD=5.1-6.6%). Proposed DMSPE/EDXRF procedure allowed to obtain low detection limits (0.032 ng mL(-1)) and high enrichment factor (1013±15). The proposed methodology was successfully applied for the determination of Se in mineral, tap, lake and sea water samples as well as in biological materials (Lobster Hepatopancreas and Pig Kidney). PMID:25618680

  11. Pulling adsorbed self-avoiding walks from a surface

    NASA Astrophysics Data System (ADS)

    Guttmann, Anthony J.; Jensen, I.; Whittington, S. G.

    2014-01-01

    We consider a self-avoiding walk model of polymer adsorption where the adsorbed polymer can be desorbed by the application of a force, concentrating on the case of the square lattice. Using series analysis methods we investigate the behaviour of the free energy of the system when there is an attractive potential ɛ with the surface and a force f applied at the last vertex, normal to the surface, and extract the phase boundary between the ballistic and adsorbed phases. We believe this to be exact to graphical accuracy. We give precise estimates of the location of the transition from the free phase to the ballistic phase, which we find to be at yc = exp (f/kBTc) = 1, and from the free phase to the adsorbed phase, which we estimate to be at ac = exp ( - ɛ/kBTc) = 1.775 615 ± 0.000 005. In addition we prove that the phase transition from the ballistic to the adsorbed phase is first order.

  12. From adsorption to condensation: the role of adsorbed molecular clusters.

    PubMed

    Yaghoubian, Sima; Zandavi, Seyed Hadi; Ward, C A

    2016-08-01

    The adsorption of heptane vapour on a smooth silicon substrate with a lower temperature than the vapour is examined analytically and experimentally. An expression for the amount adsorbed under steady state conditions is derived from the molecular cluster model of the adsorbate that is similar to the one used to derive the equilibrium Zeta adsorption isotherm. The amount adsorbed in each of a series of steady experiments is measured using a UV-vis interferometer, and gives strong support to the amount predicted to be adsorbed. The cluster distribution is used to predict the subcooling temperature required for the adsorbed vapour to make a disorder-order phase transition to become an adsorbed liquid, and the subcooling temperature is found to be 2.7 ± 0.4 K. The continuum approach for predicting the thickness of the adsorbed liquid film originally developed by Nusselt is compared with that measured and is found to over-predict the thickness by three-orders of magnitude. PMID:27426944

  13. Methane Recovery from Gaseous Mixtures Using Carbonaceous Adsorbents

    NASA Astrophysics Data System (ADS)

    Buczek, Bronisław

    2016-06-01

    Methane recovery from gaseous mixtures has both economical and ecological aspect. Methane from different waste gases like mine gases, nitrogenated natural gases and biogases can be treated as local source for production electric and heat energy. Also occurs the problem of atmosphere pollution with methane that shows over 20 times more harmful environmental effect in comparison to carbon dioxide. One of the ways utilisation such gases is enrichment of methane in the PSA technique, which requires appropriate adsorbents. Active carbons and carbon molecular sieve produced by industry and obtained in laboratory scale were examined as adsorbent for methane recuperation. Porous structure of adsorbents was investigated using densimetry measurements and adsorption of argon at 77.5K. On the basis of adsorption data, the Dubinin-Radushkevich equation parameters, micropore volume (Wo) and characteristics of energy adsorption (Eo) as well as area micropores (Smi) and BET area (SBET) were determined. The usability of adsorbents in enrichment of the methane was evaluated in the test, which simulate the basic stages of PSA process: a) adsorbent degassing, b) pressure raise in column by feed gas, c) cocurrent desorption with analysis of out flowing gas. The composition of gas phase was accepted as the criterion of the suitability of adsorbent for methane separation from gaseous mixtures. The relationship between methane recovery from gas mixture and texture parameters of adsorbents was found.

  14. Following Solid-Acid-Catalyzed Reactions by MAS NMR Spectroscopy in Liquid Phase -Zeolite-Catalyzed Conversion of Cyclohexanol in Water

    SciTech Connect

    Vjunov, Aleksei; Hu, Mary Y.; Feng, Ju; Camaioni, Donald M.; Mei, Donghai; Hu, Jian Z.; Zhao, Chen; Lercher, Johannes A.

    2014-01-07

    The catalytic conversion of cyclohexanol on zeolite HBEA in hot liquid water leads to dehydration as well as alkylation products. A novel micro autoclave suitable for application in MAS NMR at high temperatures and pressures is developed and successfully applied to obtain new insight into the mechanistic pathway leading to an understanding of the reactions under selected experimental conditions.

  15. Phase transitions and molecular motions in [Cd(H{sub 2}O){sub 6}](BF{sub 4}){sub 2} studied by DSC, {sup 1}H and {sup 19}F NMR and FT-MIR

    SciTech Connect

    Mikuli, E. . E-mail: mikuli@chemia.uj.edu.pl; Grad, B.; Medycki, W.; Holderna-Natkaniec, K.

    2004-10-01

    Two solid phase transitions of [Cd(H{sub 2}O){sub 6}](BF{sub 4}){sub 2} occurring on heating at T{sub C2}=183.3K and T{sub C1}=325.3K, with 2K and 5K hysteresis, respectively, were detected by differential scanning calorimetry (DSC). High value of entropy changes indicated large orientational disorder of the high temperature and intermediate phase. Nuclear magnetic resonance ({sup 1}H NMR and {sup 19}F NMR) relaxation measurements revealed that the phase transitions at T{sub C1} and T{sub C2} were associated with a drastic and small change, respectively, of the both spin-lattice relaxation times: T{sub 1}({sup 1}H) and T{sub 1}({sup 19}F). These relaxation processes were connected with the 'tumbling' motions of the [Cd(H{sub 2}O){sub 6}]{sup 2+}, reorientational motions of the H{sub 2}O ligands, and with the iso- and anisotropic reorientation of the BF{sub 4}{sup -} anions. The cross-relaxation effect was observed in phase III. The line width and the second moment of the {sup 1}H and {sup 19}F NMR line measurements revealed that the H{sub 2}O reorientate in all three phases of the title compound. On heating the onset of the reorientation of 3 H{sub 2}O in the [Cd(H{sub 2}O){sub 6}]{sup +2}, around the three-fold symmetry axis of these octahedron, causes the isotropic reorientation of the whole cation. The BF{sub 4}{sup -} reorientate isotropically in the phases I and II, but in the phase III they perform slow reorientation only about three- or two-fold axes. A small distortion in the structure of BF{sub 4}{sup -} as well as of [Cd(H{sub 2}O){sub 6}]{sup 2+} is postulated. The temperature dependence of the bandwidth of the O-H stretching mode measured by Fourier transform middle infrared spectroscopy (FT-MIR) indicated that the activation energy for the reorientation of the H{sub 2}O did not change much at the T{sub C2} phase transition.

  16. New insights into perfluorinated adsorbents for analytical and bioanalytical applications.

    PubMed

    Marchetti, Nicola; Guzzinati, Roberta; Catani, Martina; Massi, Alessandro; Pasti, Luisa; Cavazzini, Alberto

    2015-01-01

    Perfluorinated (F-) adsorbents are generally prepared by bonding perfluoro-functionalized silanes to silica gels. They have been employed for a long time essentially as media for solid-phase extraction of F-molecules or F-tagged molecules in organic chemistry and heterogeneous catalysis. More recently, this approach has been extended to proteomics and metabolomics. Owing to their unique physicochemical properties, namely fluorophilicity and proteinophilicity, and a better understanding of some fundamental aspects of their behavior, new applications of F-adsorbents in the field of environmental science and bio-affinity studies can be envisaged. In this article, we revisit the most important features of F-adsorbents by focusing, in particular, on some basic information that has been recently obtained through (nonlinear) chromatographic studies. Finally, we try to envisage new applications and possibilities that F-adsorbents will allow in the near future. PMID:25358910

  17. Stochastic molecular motions in the nematic, smectic-A, and solid phases of p,p{sup '}-di-n-heptyl-azoxybenzene as seen by quasielastic neutron scattering and {sup 13}C cross-polarization magic-angle-spinning NMR

    SciTech Connect

    ZajaPc, Wojciech; Urban, Stanislaw; Domenici, Valentina; Geppi, Marco; Veracini, Carlo Alberto; Telling, Mark T. F.; Gabrys, Barbara J.

    2006-05-15

    Molecular rotational dynamics in p,p{sup '}-di-n-heptyl-azoxybenzene was studied by means of quasielastic neutron scattering (QENS) and {sup 13}C cross-polarization magic-angle-spinning (CPMAS) NMR. Fast reorientation of the hydrogen nuclei was observed by QENS in the two liquid crystalline (LC) phases nematic and smectic A, as well as in the crystalline phase. The latter could not be restricted to the -CH{sub 3} rotations alone, and a clear indication was found of some other reorientation motions persisting in the crystal. Two Lorentz-type components convoluted with the resolution function gave an excellent fit to the QENS spectra in both LC phases. The narrow (slow) component was attributed to the reorientation of the whole molecule around the long axis. The corresponding characteristic time of {approx}130 ps agreed well with the values obtained in recent dielectric relaxation and {sup 2}H NMR studies. The full width at half maximum of the broader (fast) component shows a quadratic Q dependence (Q is the momentum transfer). Hence the corresponding motions could be described by a stretched exponential correlation function and were interpreted as various ''crankshaft-type'' motions within the alkyl tails. The {sup 13}C CPMAS experiments fully corroborated the QENS results, sometimes considered ambiguous in complex systems.

  18. Stochastic molecular motions in the nematic, smectic-A, and solid phases of p,p'-di-n-heptyl-azoxybenzene as seen by quasielastic neutron scattering and 13C cross-polarization magic-angle-spinning NMR.

    PubMed

    Zajac, Wojciech; Urban, Stanisław; Domenici, Valentina; Geppi, Marco; Veracini, Carlo Alberto; Telling, Mark T F; Gabryś, Barbara J

    2006-05-01

    Molecular rotational dynamics in p,p'-di-n-heptyl-azoxybenzene was studied by means of quasielastic neutron scattering (QENS) and 13C cross-polarization magic-angle-spinning (CPMAS) NMR. Fast reorientation of the hydrogen nuclei was observed by QENS in the two liquid crystalline (LC) phases nematic and smectic A, as well as in the crystalline phase. The latter could not be restricted to the -CH3 rotations alone, and a clear indication was found of some other reorientation motions persisting in the crystal. Two Lorentz-type components convoluted with the resolution function gave an excellent fit to the QENS spectra in both LC phases. The narrow (slow) component was attributed to the reorientation of the whole molecule around the long axis. The corresponding characteristic time of approximately 130 ps agreed well with the values obtained in recent dielectric relaxation and 2H NMR studies. The full width at half maximum of the broader (fast) component shows a quadratic Q dependence (Q is the momentum transfer). Hence the corresponding motions could be described by a stretched exponential correlation function and were interpreted as various "crankshaft-type" motions within the alkyl tails. The 13C CPMAS experiments fully corroborated the QENS results, sometimes considered ambiguous in complex systems. PMID:16802951

  19. NMR Mechanisms and Fluid Typing Based on Numerical Simulation in Gas-Bearing Shale

    NASA Astrophysics Data System (ADS)

    Tan, M.; Xu, J.; Wang, X.

    2013-12-01

    In Nuclear Magnetic Resonance (NMR) survey of oil- or gas-bearing shales, the relaxation is so fast and the diffusion is so low, and oil or gas typing is difficult to distinguish from each other using the previous analysis method. To study the NMR responses in gas-bearing shale, we supposed an ideal shale model including incredible water, free and adsorbed gas, and kerogen. Firstly, we supposed a series of ideal shale models with incredible water, free and adsorbed gas, and kerogen. Then, some simulations are performed for two-dimensional T2-D plots, and NMR characteristics are summarized successfully. Then, a series of simulations of different models with different adsorbed gas fractions are made, and the NMR responses are analyzed, from which we can identify the adsorbed gas and free gas. In inversion, a hybrid method with LSQR and TSVD is proved suitable for D-T2 NMR of gas shale with slow and fast diffusion, and short and long relaxation. It is noticed that the activation sequence of NMR is also important for accurate fluid typing in gas-bearing shale. We design a series of activation sequences, and simulate the corresponding NMR echo decays, and invert the fluid properties to search for an optimal activation sequence for fluid typing purpose. Figure 1 SEM picture and petrophysical model of organic shale. (a) 2D SEM shows pore and kerogen within shale. Black deposits pore, and dark gray is kerogen, light grey is matrix including clay and silica; (b) Petrophysical model Figure 2 Comparison of 2D-NMR simulations with different adsorbed gas fractions, (a) ɛ =0.0, (b) ɛ =0.2, (c) ɛ=0.4, t (d) ɛ =0.6, (e) ɛ =0.8, and (f) ɛ=1.0. From D-T2 plots, the position and amplitude of signals in T2-D plots indicate the fluid typing and fraction of the gas or adsorbed gas.

  20. On the acidity of saponite materials: a combined HRTEM, FTIR, and solid-state NMR study.

    PubMed

    Bisio, C; Gatti, G; Boccaleri, E; Marchese, L; Bertinetti, L; Coluccia, S

    2008-03-18

    Acid clays were prepared by exchanging a synthetic saponite in HCl solutions of different concentration (0.01 and 1M, respectively). A combined experimental approach (XRD, HRTEM, N2 physisorption, solid-state MAS NMR, and TGA) was used to investigate on the structural, morphological, and textural features of the samples treated under mild and strong acid conditions. FTIR spectroscopy of adsorbed probe molecules with different basicity (e.g., CO and NH3) was used to monitor the surface acid properties and acid site distribution. XRD and SS-MAS NMR indicated that the activation under mild acid conditions does not alter the clay structure, while a deep modification of the saponite framework occurred after ion exchange in 1 M HCl solution. The presence of porous amorphous silica phase after treatment under strong acid conditions was confirmed by TEM inspection augmented by SS-MAS NMR and FTIR spectroscopy. N2 and Ar physisorption measurements suggested that cavitation phenomena occurred in saponite structure. N2 physisorption confirmed that the porosity and surface area of the samples are strongly modified upon strong acid treatment. FTIR spectroscopy of adsorbed NH3 pointed out that the H-exchange in mild conditions increased the number of surface Brønsted acid sites. Conversely, these sites are significantly depleted after treatment under strong acid conditions. The use of CO as a FTIR probe molecule, which is applied for the first time to study synthetic acid clays, allowed to monitor distribution and strength of Brønsted acid sites, whose acidity is similar to that of strong acid zeolites. The Al-OH sites with medium acidity are also found in acid-activated saponites. The distribution of strong and medium acid sites is strictly dependent on the acid conditions adopted. PMID:18251562

  1. NMR analysis of biodiesel

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biodiesel is usually analyzed by the various methods called for in standards such as ASTM D6751 and EN 14214. Nuclear magnetic resonance (NMR) is not one of these methods. However, NMR, with 1H-NMR commonly applied, can be useful in a variety of applications related to biodiesel. These include monit...

  2. Advanced NMR-based techniques for pore structure analysis of coal. Quarterly report No. 9, October 1, 1993--December 30, 1993

    SciTech Connect

    Smith, D.M.

    1993-12-31

    One of the main problems in coal utilization is the inability to properly characterize its complex pore structure. Coals typically have micro/ultra-micro pores but they also exhibit meso and macroporosity. Conventional pore size techniques (adsorption/condensation, mercury porosimetry) are limited because of this broad pore size range, microporosity, reactive nature of coal, samples must be completely dried, and network/percolation effects. Small angle scattering is limited because it probes both open and dosed pores. Although one would not expect any single technique to provide a satisfactory description of a coal`s structure, it is apparent that better techniques are necessary. Small angle scattering could be improved by combining scattering and adsorption measurements. Also, the measurement of NMR parameters of various gas phase and adsorbed phase NMR active probes can provide pore structure information. We will investigate the dependence of the common NMR parameters such as chemical shifts and relaxation times of several different nuclei and compounds on the pore structure of model microporous solids, carbons, and coals. In particular, we will study the interaction between several small molecules ({sup 129}Xe, {sup 3}He, {sup 14}N{sub 2}, {sup 14}NH{sub 3}, {sup 15}N{sub 2}, {sup 13}CH{sub 4}, {sup 13}CO{sub 2}) and pore surface. Our current work may be divided into three areas: small-angle X-ray scattering (SAXS), adsorption, and NMR.

  3. NMR Hyperpolarization Techniques for Biomedicine

    PubMed Central

    Nikolaou, Panayiotis; Goodson, Boyd M.

    2015-01-01

    Recent developments in NMR hyperpolarization have enabled a wide array of new in vivo molecular imaging modalities—ranging from functional imaging of the lungs to metabolic imaging of cancer. This Concept article explores selected advances in methods for the preparation and use of hyperpolarized contrast agents, many of which are already at or near the phase of their clinical validation in patients. PMID:25470566

  4. Conformational changes of adsorbed proteins

    NASA Astrophysics Data System (ADS)

    Allen, Scott

    2005-03-01

    The adsorption of bovine serum albumin (BSA) and pepsin to gold surfaces has been studied using surface plasmon resonance (SPR). Proteins are adsorbed from solution onto a gold surface and changes in the conformation of the adsorbed proteins are induced by changing the buffer solution. We selected pH and ionic strength values for the buffer solutions that are known from our circular dichroism measurements to cause conformational changes of the proteins in bulk solution. We find that for both BSA and pepsin the changes in conformation are impeded by the interaction of the protein with the gold surface.

  5. Hyperpolarized 131Xe NMR spectroscopy

    PubMed Central

    Stupic, Karl F.; Cleveland, Zackary I.; Pavlovskaya, Galina E.; Meersmann, Thomas

    2011-01-01

    Hyperpolarized (hp) 131Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T1 relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent 131Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in 129Xe SEOP. 131Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase 131Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp 131Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp 131Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I⩾1/2 nuclei is presented. PMID:21051249

  6. Distinguishing Phosphate Structural Defects From Inclusions in Calcite and Aragonite by NMR Spectroscopy (Invited)

    NASA Astrophysics Data System (ADS)

    Phillips, B. L.; Mason, H. E.

    2010-12-01

    Variations in the concentration of minor and trace elements are being studied extensively for potential use as proxies to infer environmental conditions at the time of mineral deposition. Such proxies rely fundamentally on a relationship between the activities in the solution and in the solid that would seem to be simple only in the case that the species substitutes into the mineral structure. Other incorporation mechanisms are possible, including inclusions (both mineral and fluid) and occlusion of surface adsorbate complexes, that might be sensitive to other factors, such as crystallization kinetics, and difficult to distinguish analytically. For example, it is known from mineral adsorption studies that surface precipitates can be nanoscopic, and might not be apparent at resolutions typical of microchemical analysis. Techniques by which a structural relationship between the substituting element and the host mineral structure are needed to provide a sound basis for geochemical proxies. NMR spectroscopy offers methods for probing such spatial relationship. We are using solid-state NMR spectroscopy to investigate phosphate incorporation in calcium carbonate minerals, including calcite speleothems and coral skeletal aragonite, at concentrations of the order 100 μg P g -1. In 31P NMR spectra of most samples, narrow peaks arising from crystalline inclusions can be resolved, including apatite in coral aragonite and an unidentified phase in calcite. All samples studied yield also a broad 31P signal, centered near chemical shifts of +3 to +4 ppm, that could be assigned to phosphate defects in the host mineral and from which the fraction of P occurring in the carbonate mineral structure can be determined. To test this assignment we applied rotational-echo double-resonance (REDOR) NMR techniques that probe the molecular-scale proximity of carbonate groups to the phosphate responsible for the broad 31P peak. This method measures dipole-dipole coupling between 31P of

  7. Linear transport models for adsorbing solutes

    NASA Astrophysics Data System (ADS)

    Roth, K.; Jury, W. A.

    1993-04-01

    A unified linear theory for the transport of adsorbing solutes through soils is presented and applied to analyze movement of napropamide through undisturbed soil columns. The transport characteristics of the soil are expressed in terms of the travel time distribution of the mobile phase which is then used to incorporate local interaction processes. This approach permits the analysis of all linear transport processes, not only the small subset for which a differential description is known. From a practical point of view, it allows the direct use of measured concentrations or fluxes of conservative solutes to characterize the mobile phase without first subjecting them to any model. For complicated flow regimes, this may vastly improve the identification of models and estimation of their parameters for the local adsorption processes.

  8. Solution- and Adsorbed-State Structural Ensembles Predicted for the Statherin-Hydroxyapatite System

    PubMed Central

    Masica, David L.; Gray, Jeffrey J.

    2009-01-01

    Abstract We have developed a multiscale structure prediction technique to study solution- and adsorbed-state ensembles of biomineralization proteins. The algorithm employs a Metropolis Monte Carlo-plus-minimization strategy that varies all torsional and rigid-body protein degrees of freedom. We applied the technique to fold statherin, starting from a fully extended peptide chain in solution, in the presence of hydroxyapatite (HAp) (001), (010), and (100) monoclinic crystals. Blind (unbiased) predictions capture experimentally observed macroscopic and high-resolution structural features and show minimal statherin structural change upon adsorption. The dominant structural difference between solution and adsorbed states is an experimentally observed folding event in statherin's helical binding domain. Whereas predicted statherin conformers vary slightly at three different HAp crystal faces, geometric and chemical similarities of the surfaces allow structurally promiscuous binding. Finally, we compare blind predictions with those obtained from simulation biased to satisfy all previously published solid-state NMR (ssNMR) distance and angle measurements (acquired from HAp-adsorbed statherin). Atomic clashes in these structures suggest a plausible, alternative interpretation of some ssNMR measurements as intermolecular rather than intramolecular. This work demonstrates that a combination of ssNMR and structure prediction could effectively determine high-resolution protein structures at biomineral interfaces. PMID:19383454

  9. DESIGNING FIXED-BED ADSORBERS TO REMOVE MIXTURES OF ORGANICS.

    EPA Science Inventory

    A liquid-phase granular activated carbon (GAC) pilot plant and a full-scale GAC adsorber were designed, built, and operated in order to evaluate their performance for treating a groundwater contaminated with several volatile and synthetic organic chemicals. Several empty bed con...

  10. An NMR Study of Microvoids in Polymers

    NASA Technical Reports Server (NTRS)

    Toy, James; Mattrix, Larry

    1996-01-01

    An understanding of polymer defect structures, like microvoids in polymeric matrices, is most crucial to their fabrication and application potential. In this project guest atoms are introduced into the microvoids in PMR-15 and NMR is used to determine microvoid sizes and locations. Xenon is a relatively inert probe that would normally not be found naturally in polymer or in NMR probe materials. There are two NMR active Xenon isotopes, Xe-129 and Xe-131. The Xe atom has a very high polarizability, which makes it sensitive to the intracrystalline environment of polymers. Interactions between the Xe atoms and the host matrix perturb and Xe electron cloud, deshielding the nuclei, and thereby expanding the range of the observed NMR chemical shifts. This chemical shift range which may be as large as 5000 ppm, permits subtle structural and chemical effects to be studied with high sensitivity. The Xe-129-NMR line shape has been found to vary in response to changes in the pore symmetry of the framework hosts in Zeolites and Clathrasil compounds. Before exposure to Xe gas, the PMR-15 samples were dried in a vacuum oven at 150 C for 48 hours. The samples were then exposed to Xe gas at 30 psi for 72 hours and sealed in glass tubes with 1 atmosphere of Xenon gas. Xenon gas at 1 atmosphere was used to tune up the spectrometer and to set up the appropriate NMR parameters. A series of spectra were obtained interspersed with applications of vacuum and heating to drive out the adsorbed Xe and determine the role of Xe-Xe interactions in the observed chemical shift.

  11. Effects of Pressure on the Short-range Structure and Speciation of Fluid phases in Silicate Melts: Insights from Multi-nuclear NMR and X-ray Raman Scattering

    NASA Astrophysics Data System (ADS)

    Kim, E.; Fei, Y.; Tschauner, O. D.; Mosenfelder, J. L.; Asimow, P. D.; Lee, S.

    2013-12-01

    The atomic structures of fluid-bearing silicate liquids at high pressure are essential to understand the changes in the melt properties in earth's interior and to yield insights into the deep carbon-hydrogen cycle. Despite the importance, structural changes in silicate liquids (with/without fluid phases) under compression have not been fully understood. The recent breakthroughs in NMR and X-ray Raman scattering (XRS) allowed us to explore the detailed effect of pressure on the degree of melt polymerization and speciation of fluid phases in oxide glasses with varying composition (e.g. Lee, Rev. Min. Geochem. 2013 accepted; Proc. Nat. Aca. Sci. 2011, 108 6847; Kim and Lee, Geochim. Cosmochim Acta. In press; Lee et al. Geophys. Res. Letts. 2012, 39 5306). Here, we present the key recent results of structure of silicate glasses under compression. In contrast to an expected complex composition-dependence in melt-densification, the experimental results of diverse silicate melts demonstrate a simple trend in pressure-induced decreases in non-bridging oxygen content that can be modeled with a narrow range of network flexibility upon compression. NMR results of model basaltic glasses showed that both dynamic and static compression lead to an increase in the fraction of highly coordinated Al: whereas statically compressed basaltic glass at 5 GPa leads to the formation of ~40% [5,6]Al, dynamically compressed basaltic glass at peak pressure of ~ 20 GPa consists only of ~3-4% of [5]Al. The threshold pressure for Al coordination transformation in the basaltic glass upon dynamic compression is estimated to ~ 15 GPa, providing a path-dependent Al-coordination transformation. The first high-resolution 13C MAS NMR spectrum for carbon-bearing enstatite at 1.5 GPa revealed the presence of molecular CO2 in the lattice, providing a new solubility mechanism of carbon into chain silicates. 13C NMR spectra for albite glasses quenched from melts at high pressure up to 6 GPa showed that

  12. Polymorphism and disorder in natural active ingredients. Low and high-temperature phases of anhydrous caffeine: Spectroscopic ((1)H-(14)N NMR-NQR/(14)N NQR) and solid-state computational modelling (DFT/QTAIM/RDS) study.

    PubMed

    Seliger, Janez; Žagar, Veselko; Apih, Tomaž; Gregorovič, Alan; Latosińska, Magdalena; Olejniczak, Grzegorz Andrzej; Latosińska, Jolanta Natalia

    2016-03-31

    The polymorphism of anhydrous caffeine (1,3,7-trimethylxanthine; 1,3,7-trimethyl-1H-purine-2,6-(3H,7H)-dione) has been studied by (1)H-(14)N NMR-NQR (Nuclear Magnetic Resonance-Nuclear Quadrupole Resonance) double resonance and pure (14)N NQR (Nuclear Quadrupole Resonance) followed by computational modelling (Density Functional Theory, supplemented Quantum Theory of Atoms in Molecules with Reduced Density Gradient) in solid state. For two stable (phase II, form β) and metastable (phase I, form α) polymorphs the complete NQR spectra consisting of 12 lines were recorded. The assignment of signals detected in experiment to particular nitrogen sites was verified with the help of DFT. The shifts of the NQR frequencies, quadrupole coupling constants and asymmetry parameters at each nitrogen site due to polymorphic transition were evaluated. The strongest shifts were observed at N(3) site, while the smallest at N(9) site. The commercial pharmaceutical sample was found to contain approximately 20-25% of phase I and 75-80% of phase II. The orientational disorder in phase II with a local molecular arrangement mimics that in phase I. Substantial differences in the intermolecular interaction phases I and II of caffeine were analysed using computational (DFT/QTAIM/RDS) approach. The analysis of local environment of each nitrogen nucleus permitted drawing some conclusions on the topology of interactions in both polymorphs. For the most stable orientations in phase I and phase II the maps of the principal component qz of EFG tensor and its asymmetry parameter at each point of the molecular system were calculated and visualized. The relevant maps calculated for both phases I and II indicates small variation in electrostatic potential upon phase change. Small differences between packings in phases slightly disturb the neighbourhood of the N(1) and N(7) nitrogens, thus are meaningless from the biological point of view. The composition of two phases in pharmaceutical material

  13. Measurement of the intracrystalline self-diffusion of xenon in zeolites by the NMR pulsed field gradient technique

    SciTech Connect

    Heink, W.; Kaerger, J.; Pfeifer, H.; Stallmach, F. )

    1990-03-14

    With use of {sup 129}Xe NMR, the NMR pulsed field gradient technique is applied to study the self-diffusion of xenon adsorbed on zeolites NaX, NaCaA, and ZSM-5. In their dependence on both the type of adsorbent and the sorbate concentration, the self-diffusion coefficients are found to follow the same patterns as previously determined for methane by {sup 1}H NMR. For NaCaA, the comparison of the present results with literature data reveals large discrepancies, while recent computer simulations of xenon self-diffusion in ZSM-5 are found to be in reasonable agreement.

  14. Vibrational Studies of Adsorbate-Induced Reconstruction on Molybdenum Surfaces.

    NASA Astrophysics Data System (ADS)

    Lopinski, Gregory Peter

    Adsorbate-induced rearrangement of the substrate structure strongly modifies the adsorbate-substrate and adsorbate-adsorbate interactions, leading to the complex behavior observed in many chemisorption systems. In this thesis the H/Mo(211), O/Mo(211) and Na/Mo(100) systems have been studied using high resolution electron energy loss spectroscopy (HREELS) to observe vibrations of the adsorbed atoms. The vibrational data is correlated with observations of the long-range order probed by LEED as well as the work function changes induced by adsorption. Adsorbate -induced substrate reconstruction plays an important role in all three of these systems. Studies of the coadsorption systems O+H/Mo(211) and Na+O/Mo(100) indicate how these effects can influence interactions between adsorbates. For H/Mo(211), above 1ML a (1 x 1) to (1 x 2) transition is observed and attributed to modification of the substrate periodicity. Below 1ML, H atoms are bridge bonded and induce local distortions of the substrate. The transition to the (1 x 2) phase involves the ordering of these displacements and occupation of three-fold sites partially populated by conversion of the bridge bonded species. This conversion accounts for the sawtooth-like coverage dependence of the work function. The structural model proposed for this system is also supported by the desorption parameters and partial molar entropy extracted from adsorption isobars. Oxygen adsorption on Mo(211) involves the occupation of multiple binding sites, with both the long-range order and the local geometry of the adsorbate phases strongly temperature dependent. Coadsorption of low coverages of oxygen and hydrogen leads to segregation of the two adsorbates which can be understood in terms of a substrate-mediated repulsive interaction between O and H. For Na/Mo(100), the frequency of the Na-Mo symmetric stretch mode does not shift with coverage although the mode intensity is strongly coverage dependent. The absence of a frequency shift

  15. Two dimensional NMR spectroscopy

    SciTech Connect

    Schram, J.; Bellama, J.M.

    1988-01-01

    Two dimensional NMR represents a significant achievement in the continuing effort to increase solution in NMR spectroscopy. This book explains the fundamentals of this new technique and its analytical applications. It presents the necessary information, in pictorial form, for reading the ''2D NMR,'' and enables the practicing chemist to solve problems and run experiments on a commercial spectrometer by using the software provided by the manufacturer.

  16. Photodecomposition of chloromethanes adsorbed on silica surfaces

    NASA Technical Reports Server (NTRS)

    Ausloos, P.; Rebbert, R. E.; Glasgow, L.

    1977-01-01

    Irradiation of CCl4, CFCl3, and CF2Cl2 in the presence of C2H6 in vessels containing silica sand or fused quartz tubing results in the formation of chlorine-containing products. The formation of these compounds occurs at wavelengths extending up to approximately 400 nm, that is, at wavelengths well beyond the absorption threshold of the chloromethanes in the gas phase. It is suggested that CCl4 adsorbed on silica surfaces photodissociates to yield CCl3 and CCl2 species. The poor material balance obtained in these experiments indicates that several of the chlorine-containing fragments are strongly adsorbed on the surface. At a CCl4 pressure of 13 Pa (0.1 torr), photolysis with 366 nm light in the presence of sand results in the decomposition of one molecule for every 10,000 photons striking the surface. Under otherwise identical conditions, the photon-induced breadkdown of CFCl3 and CF2Cl2 is respectively only 10% or 3% as efficient.

  17. MAS PFG NMR Studies of Mixtures in Porous Materials

    NASA Astrophysics Data System (ADS)

    Gratz, Marcel; Hertel, Stefan; Wehring, Markus; Schlayer, Stefan; Stallmach, Frank; Galvosas, Petrik

    2011-03-01

    Pulsed field gradient (PFG) and magic angle spinning (MAS) NMR techniques have been successfully combined for the study of mixture diffusion in porous materials. Using a modular setup of commercially available components, gradient pulses of up to ±2.6 T/m can be applied coinciding with fast sample rotation at the magic angle. Methods for the proper alignment of all components are presented along with protocols for MAS PFG NMR experiments. Finally, first diffusion measurements of n-hexane and benzene being adsorbed together in the metal-organic framework MOF-5 are presented.

  18. Sol-gel synthesis, phase composition, morphological and structural characterization of Ca10(PO4)6(OH)2: XRD, FTIR, SEM, 3D SEM and solid-state NMR studies

    NASA Astrophysics Data System (ADS)

    Kareiva, Simonas; Klimavicius, Vytautas; Momot, Aleksandr; Kausteklis, Jonas; Prichodko, Aleksandra; Dagys, Laurynas; Ivanauskas, Feliksas; Sakirzanovas, Simas; Balevicius, Vytautas; Kareiva, Aivaras

    2016-09-01

    Aqueous sol-gel chemistry route based on ammonium-hydrogen phosphate as the phosphorus precursor, calcium acetate monohydrate as source of calcium ions, and 1,2-ethylendiaminetetraacetic acid (EDTA), or 1,2-diaminocyclohexanetetracetic acid (DCTA), or tartaric acid (TA), or ethylene glycol (EG), or glycerol (GL) as complexing agents have been used to prepare calcium hydroxyapatite (Ca10(PO4)6(OH)2, CHAp). The phase transformations, composition, and structural changes in the polycrystalline samples were studied by infrared spectroscopy (FTIR), X-ray powder diffraction analysis (XRD), and scanning electron microscopy (SEM). The local short-range (nano- and mezo-) scale effects in CHAp were studied using solid-state NMR spectroscopy. The spatial 3D data from the SEM images of CHAp samples obtained by TA, EG and GL sol-gel routes were recovered for the first time to our knowledge.

  19. Interface Induced Growth and Transformation of Polymer-Conjugated Proto-Crystalline Phases in Aluminosilicate Hybrids: A Multiple-Quantum (23)Na-(23)Na MAS NMR Correlation Spectroscopy Study.

    PubMed

    Brus, Jiri; Kobera, Libor; Urbanova, Martina; Doušová, Barbora; Lhotka, Miloslav; Koloušek, David; Kotek, Jiří; Čuba, Pavel; Czernek, Jiri; Dědeček, Jiří

    2016-03-22

    Nanostructured materials typically offer enhanced physicochemical properties because of their large interfacial area. In this contribution, we present a comprehensive structural characterization of aluminosilicate hybrids with polymer-conjugated nanosized zeolites specifically grown at the organic-inorganic interface. The inorganic amorphous Al-O-Si framework is formed by alkali-activated low-temperature transformation of metakaoline, whereas simultaneous copolymerization of organic comonomers creates a secondary epoxide network covalently bound to the aluminosilicate matrix. This secondary epoxide phase not only enhances the mechanical integrity of the resulting hybrids but also introduces additional binding sites accessible for compensating negative charge on the aluminosilicate framework. This way, the polymer network initiates growth and subsequent transformation of protocrystalline short-range ordered zeolite domains that are located at the organic-inorganic interface. By applying an experimental approach based on 2D (23)Na-(23)Na double-quantum (DQ) MAS NMR spectroscopy, we discovered multiple sodium binding sites in these protocrystalline domains, in which immobilized Na(+) ions form pairs or small clusters. It is further demonstrated that these sites, the local geometry of which allows for the pairing of sodium ions, are preferentially occupied by Pb(2+) ions during the ion exchange. The proposed synthesis protocol thus allows for the preparation of a novel type of geopolymer hybrids with polymer-conjugated zeolite phases suitable for capturing and storage of metal cations. The demonstrated (23)Na-(23)Na DQ MAS NMR combined with DFT calculations represents a suitable approach for understanding the role of Na(+) ions in aluminositicate solids and related inorganic-organic hybrids, particularly their specific arrangement and clustering at interfacial areas. PMID:26931131

  20. Supercritical fluid regeneration of adsorbents

    NASA Astrophysics Data System (ADS)

    Defilippi, R. P.; Robey, R. J.

    1983-05-01

    The results of a program to perform studies supercritical (fluid) carbon dioxide (SCF CO2) regeneration of adsorbents, using samples of industrial wastewaters from manufacturing pesticides and synthetic solution, and to estimate the economics of the specific wastewater treatment regenerations, based on test data are given. Processing costs for regenerating granular activated carbon GAC) for treating industrial wastewaters depend on stream properties and regeneration throughput.

  1. Identifying low-coverage surface species on supported noble metal nanoparticle catalysts by DNP-NMR

    SciTech Connect

    Johnson, Robert L.; Perras, Frédéric A.; Kobayashi, Takeshi; Schwartz, Thomas J.; Dumesic, James A.; Shanks, Brent H.; Pruski, Marek

    2015-11-20

    DNP-NMR spectroscopy has been applied to enhance the signal for organic molecules adsorbed on γ-Al2O3-supported Pd nanoparticles. In addition, by offering >2500-fold time savings, the technique enabled the observation of 13C-13C cross-peaks for low coverage species, which were assigned to products from oxidative degradation of methionine adsorbed on the nanoparticle surface.

  2. Identifying low-coverage surface species on supported noble metal nanoparticle catalysts by DNP-NMR

    DOE PAGESBeta

    Johnson, Robert L.; Perras, Frédéric A.; Kobayashi, Takeshi; Schwartz, Thomas J.; Dumesic, James A.; Shanks, Brent H.; Pruski, Marek

    2015-11-20

    DNP-NMR spectroscopy has been applied to enhance the signal for organic molecules adsorbed on γ-Al2O3-supported Pd nanoparticles. In addition, by offering >2500-fold time savings, the technique enabled the observation of 13C-13C cross-peaks for low coverage species, which were assigned to products from oxidative degradation of methionine adsorbed on the nanoparticle surface.

  3. Identifying low-coverage surface species on supported noble metal nanoparticle catalysts by DNP-NMR.

    PubMed

    Johnson, Robert L; Perras, Frédéric A; Kobayashi, Takeshi; Schwartz, Thomas J; Dumesic, James A; Shanks, Brent H; Pruski, Marek

    2016-01-31

    DNP-NMR spectroscopy has been applied to enhance the signal for organic molecules adsorbed on γ-Al2O3-supported Pd nanoparticle catalysts. By offering >2500-fold time savings, the technique enabled the observation of (13)C-(13)C cross-peaks for low coverage species, which were assigned to products from oxidative degradation of methionine adsorbed on the nanoparticle surface. PMID:26675287

  4. Carbon-13 NMR spectroscopy study of L-zeolite- and silica-supported platinum catalysts

    SciTech Connect

    Sharma, S.B.; Laska, T.E.; Balaraman, P.; Root, T.W.; Dumesic, J.A.

    1994-12-01

    NMR studies of CO adsorbed on small Pt particles show evidence of changes in the metallic nature of these particles with size. Large particles on silica or the exterior of zeolite crystallites have conduction-band electrons that cause a Knight shift for adsorbed CO. Small particles in zeolite cavities are diamagnetic clusters, and yield spectra for linear and bridging carbonyls similar to those of transition-metal cluster compounds. {sup 13}C NMR of CO offers a simple probe of metal dispersion and particle size for these Pt catalysts and other noble metal systems. 29 refs., 7 figs., 2 tabs.

  5. Solid-state NMR studies of biomineralization peptides and proteins.

    PubMed

    Roehrich, Adrienne; Drobny, Gary

    2013-09-17

    Nature has evolved sophisticated strategies for engineering hard tissues through the interaction of proteins, and ultimately cells, with inorganic mineral phases. This process, called biomineralization, is how living organisms transform inorganic materials such as hydroxyapatite, calcite, and silica into highly intricate and organized structures. The remarkable material properties of shell, bone, and teeth come from the activities of proteins that function at the organic-inorganic interface. A better understanding of the biomolecular mechanisms used to promote or retard the formation of mineral-based structures could provide important design principles for the development of calcification inhibitors and promoters in orthopedics, cardiology, urology, and dentistry. With the knowledge of the structural basis for control of hard tissue growth by proteins, scientists could potentially develop materials using biomimetic principles with applications in catalysis, biosensors, electronic devices, and chromatographic separations, to name a few. Additionally, biomineralization also has potential applications in electronics, catalysis, magnetism, sensory devices, and mechanical design. Where man-made hard materials require the use of extreme temperatures, high pressure, and pH, biological organisms can accomplish these feats at ambient temperature and at physiological pH. Despite the fact that many researchers want to identify and control the structure of proteins at material and biomineral interfaces, there is a decided lack of molecular-level structure information available for proteins at biomaterial interfaces in general. In particular, this holds for mammalian proteins that directly control calcification processes in hard tissue. The most fundamental questions regarding the secondary and tertiary structures of proteins adsorbed to material surfaces, how proteins catalyze the formation of biomineral composites, or how proteins interact at biomaterial interfaces remain

  6. Adsorbed self-avoiding walks subject to a force

    NASA Astrophysics Data System (ADS)

    Janse van Rensburg, E. J.; Whittington, S. G.

    2013-11-01

    We consider a self-avoiding walk model of polymer adsorption where the adsorbed polymer can be desorbed by the application of a force. In this paper the force is applied normal to the surface at the last vertex of the walk. We prove that the appropriate limiting free energy exists where there is an applied force and a surface potential term, and prove that this free energy is convex in appropriate variables. We then derive an expression for the limiting free energy in terms of the free energy without a force and the free energy with no surface interaction. Finally we show that there is a phase boundary between the adsorbed phase and the desorbed phase in the presence of a force, prove some qualitative properties of this boundary and derive bounds on the location of the boundary.

  7. Revealing lithium-silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy.

    PubMed

    Ogata, K; Salager, E; Kerr, C J; Fraser, A E; Ducati, C; Morris, A J; Hofmann, S; Grey, C P

    2014-01-01

    Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by (7)Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium-silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies. PMID:24488002

  8. Following solid-acid-catalyzed reactions by MAS NMR spectroscopy in liquid phase--zeolite-catalyzed conversion of cyclohexanol in water.

    PubMed

    Vjunov, Aleksei; Hu, Mary Y; Feng, Ju; Camaioni, Donald M; Mei, Donghai; Hu, Jian Z; Zhao, Chen; Lercher, Johannes A

    2014-01-01

    A microautoclave magic angle spinning NMR rotor is developed enabling in situ monitoring of solid-liquid-gas reactions at high temperatures and pressures. It is used in a kinetic and mechanistic study of the reactions of cyclohexanol on zeolite HBEA in 130 °C water. The (13) C spectra show that dehydration of 1-(13) C-cyclohexanol occurs with significant migration of the hydroxy group in cyclohexanol and the double bond in cyclohexene with respect to the (13) C label. A simplified kinetic model shows the E1-type elimination fully accounts for the initial rates of 1-(13) C-cyclohexanol disappearance and the appearance of the differently labeled products, thus suggesting that the cyclohexyl cation undergoes a 1,2-hydride shift competitive with rehydration and deprotonation. Concurrent with the dehydration, trace amounts of dicyclohexyl ether are observed, and in approaching equilibrium, a secondary product, cyclohexyl-1-cyclohexene is formed. Compared to phosphoric acid, HBEA is shown to be a more active catalyst exhibiting a dehydration rate that is 100-fold faster per proton. PMID:24282024

  9. Spin-spin coupling in the HD molecule determined from 1H and 2H NMR experiments in the gas-phase

    NASA Astrophysics Data System (ADS)

    Garbacz, Piotr

    2014-10-01

    The indirect spin-spin coupling of hydrogen deuteride, J(D, H), was determined from a series of 1H and 2H NMR spectra acquired at various densities of gaseous solvents (He, Ar, CO2, and N2O). The analysis of these spectra shows that accurate determination of J(D, H) from this experimental data requires careful examination of the effects of nuclear relaxation and of HD-solvent gas interactions on hydrogen deuteride line shapes. Particularly, it was found that the first-order corrections of the peak-to-peak separations between HD multiplet peaks due to weak van der Waals interactions are proportional to solvent gas density, while these corrections for nuclear relaxation of the proton and the deuteron are proportional to the second power of the inverse of the gas density. Analysis of the data indicates that J(D, H), obtained by correcting for the effects of nuclear relaxation and intermolecular interactions, is 43.136(7) Hz at 300 K.

  10. Lectures on pulsed NMR

    SciTech Connect

    Pines, A.

    1988-08-01

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 32 refs., 56 figs.

  11. Lectures on pulsed NMR

    SciTech Connect

    Pines, A.

    1986-09-01

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 55 figs.

  12. Method And Apparatus For Regenerating Nox Adsorbers

    DOEpatents

    Driscoll, J. Joshua; Endicott, Dennis L.; Faulkner, Stephen A.; Verkiel, Maarten

    2006-03-28

    Methods and apparatuses for regenerating a NOx adsorber coupled with an exhaust of an engine. An actuator drives a throttle valve to a first position when regeneration of the NOx adsorber is desired. The first position is a position that causes the regeneration of the NOx adsorber. An actuator drives the throttle valve to a second position while regeneration of the NOx adsorber is still desired. The second position being a position that is more open than the first position and operable to regenerate a NOx adsorber.

  13. NMR logging apparatus

    DOEpatents

    Walsh, David O; Turner, Peter

    2014-05-27

    Technologies including NMR logging apparatus and methods are disclosed. Example NMR logging apparatus may include surface instrumentation and one or more downhole probes configured to fit within an earth borehole. The surface instrumentation may comprise a power amplifier, which may be coupled to the downhole probes via one or more transmission lines, and a controller configured to cause the power amplifier to generate a NMR activating pulse or sequence of pulses. Impedance matching means may be configured to match an output impedance of the power amplifier through a transmission line to a load impedance of a downhole probe. Methods may include deploying the various elements of disclosed NMR logging apparatus and using the apparatus to perform NMR measurements.

  14. Silver and Gold NMR

    PubMed Central

    Zangger, Klaus

    1999-01-01

    Silver and gold, together with copper, form the transition metal group IB elements in the periodic table and possess very different nuclear magnetic resonance (NMR) spectroscopic properties. While there is only one gold isotope (197Au), which has a spin of 3/2 and therefore a quadrupole moment, silver occurs in two isotopic forms (109Ag and 109Au), both of which have a spin 1/2 and similar NMR spectroscopic properties. The unfavorable properties of gold have prevented its NMR spectroscopic investigation thus far. On the other hand, there are several reports of silver NMR. However, the low sensitivity of silver, combined with its long relaxation times have rendered the direct detection of silver possible only with concentrations greater than a few tenth molar. Reviewed here are the general limitations of silver NMR and some techniques to partially overcome these limitations, as well as a summary of currently available chemical shift and scalar coupling data on 109Ag. PMID:18475898

  15. Complexation of trace metals by adsorbed natural organic matter

    USGS Publications Warehouse

    Davis, J.A.

    1984-01-01

    The adsorption behavior and solution speciation of Cu(II) and Cd(II) were studied in model systems containing colloidal alumina particles and dissolved natural organic matter. At equilibrium a significant fraction of the alumina surface was covered by adsorbed organic matter. Cu(II) was partitioned primarily between the surface-bound organic matter and dissolved Cu-organic complexes in the aqueous phase. Complexation of Cu2+ with the functional groups of adsorbed organic matter was stronger than complexation with uncovered alumina surface hydroxyls. It is shown that the complexation of Cu(II) by adsorbed organic matter can be described by an apparent stability constant approximately equal to the value found for solution phase equilibria. In contrast, Cd(II) adsorption was not significantly affected by the presence of organic matter at the surface, due to weak complex formation with the organic ligands. The results demonstrate that general models of trace element partitioning in natural waters must consider the presence of adsorbed organic matter. ?? 1984.

  16. Photochemistry of adsorbed nitrate on aluminum oxide particle surfaces.

    PubMed

    Rubasinghege, Gayan; Grassian, Vicki H

    2009-07-01

    Nitrogen oxides, including nitrogen dioxide and nitric acid, react with mineral dust particles in the atmosphere to yield adsorbed nitrate. Although nitrate ion is a well-known chromophore in natural waters, little is known about the surface photochemistry of nitrate adsorbed on mineral particles. In this study, nitrate adsorbed on aluminum oxide, a model system for mineral dust aerosol, is irradiated with broadband light (lambda > 300 nm) as a function of relative humidity (RH) in the presence of molecular oxygen. Upon irradiation, the nitrate ion readily undergoes photolysis to yield nitrogen-containing gas-phase products including NO(2), NO, and N(2)O, with NO being the major product. The relative ratio and product yields of these gas-phase products change with RH, with N(2)O production being highest at the higher relative humidities. Furthermore, an efficient dark reaction readily converts the major NO product into NO(2) during post-irradiation. Photochemical processes on mineral dust aerosol surfaces have the potential to impact the chemical balance of the atmosphere, yet little is known about these processes. In this study, the impact that adsorbed nitrate photochemistry may have on the renoxification of the atmosphere is discussed. PMID:19534452

  17. Influences of Dilute Organic Adsorbates on the Hydration of Low-Surface-Area Silicates.

    PubMed

    Sangodkar, Rahul P; Smith, Benjamin J; Gajan, David; Rossini, Aaron J; Roberts, Lawrence R; Funkhouser, Gary P; Lesage, Anne; Emsley, Lyndon; Chmelka, Bradley F

    2015-07-01

    Competitive adsorption of dilute quantities of certain organic molecules and water at silicate surfaces strongly influence the rates of silicate dissolution, hydration, and crystallization. Here, we determine the molecular-level structures, compositions, and site-specific interactions of adsorbed organic molecules at low absolute bulk concentrations on heterogeneous silicate particle surfaces at early stages of hydration. Specifically, dilute quantities (∼0.1% by weight of solids) of the disaccharide sucrose or industrially important phosphonic acid species slow dramatically the hydration of low-surface-area (∼1 m(2)/g) silicate particles. Here, the physicochemically distinct adsorption interactions of these organic species are established by using dynamic nuclear polarization (DNP) surface-enhanced solid-state NMR techniques. These measurements provide significantly improved signal sensitivity for near-surface species that is crucial for the detection and analysis of dilute adsorbed organic molecules and silicate species on low-surface-area particles, which until now have been infeasible to characterize. DNP-enhanced 2D (29)Si{(1)H}, (13)C{(1)H}, and (31)P{(1)H} heteronuclear correlation and 1D (29)Si{(13)C} rotational-echo double-resonance NMR measurements establish hydrogen-bond-mediated adsorption of sucrose at distinct nonhydrated and hydrated silicate surface sites and electrostatic interactions with surface Ca(2+) cations. By comparison, phosphonic acid molecules are found to adsorb electrostatically at or near cationic calcium surface sites to form Ca(2+)-phosphonate complexes. Although dilute quantities of both types of organic molecules effectively inhibit hydration, they do so by adsorbing in distinct ways that depend on their specific architectures and physicochemical interactions. The results demonstrate the feasibility of using DNP-enhanced NMR techniques to measure and assess dilute adsorbed molecules and their molecular interactions on low

  18. Imaging the wave functions of adsorbed molecules

    PubMed Central

    Lüftner, Daniel; Ules, Thomas; Reinisch, Eva Maria; Koller, Georg; Soubatch, Serguei; Tautz, F. Stefan; Ramsey, Michael G.; Puschnig, Peter

    2014-01-01

    The basis for a quantum-mechanical description of matter is electron wave functions. For atoms and molecules, their spatial distributions and phases are known as orbitals. Although orbitals are very powerful concepts, experimentally only the electron densities and -energy levels are directly observable. Regardless whether orbitals are observed in real space with scanning probe experiments, or in reciprocal space by photoemission, the phase information of the orbital is lost. Here, we show that the experimental momentum maps of angle-resolved photoemission from molecular orbitals can be transformed to real-space orbitals via an iterative procedure which also retrieves the lost phase information. This is demonstrated with images obtained of a number of orbitals of the molecules pentacene (C22H14) and perylene-3,4,9,10-tetracarboxylic dianhydride (C24H8O6), adsorbed on silver, which are in excellent agreement with ab initio calculations. The procedure requires no a priori knowledge of the orbitals and is shown to be simple and robust. PMID:24344291

  19. Phase modulation in dipolar-coupled A 2 spin systems: effect of maximum state mixing in 1H NMR in vivo

    NASA Astrophysics Data System (ADS)

    Schröder, Leif; Schmitz, Christian; Bachert, Peter

    2004-12-01

    Coupling constants of nuclear spin systems can be determined from phase modulation of multiplet resonances. Strongly coupled systems such as citrate in prostatic tissue exhibit a more complex modulation than AX connectivities, because of substantial mixing of quantum states. An extreme limit is the coupling of n isochronous spins (A n system). It is observable only for directly connected spins like the methylene protons of creatine and phosphocreatine which experience residual dipolar coupling in intact muscle tissue in vivo. We will demonstrate that phase modulation of this "pseudo-strong" system is quite simple compared to those of AB systems. Theory predicts that the spin-echo experiment yields conditions as in the case of weak interactions, in particular, the phase modulation depends linearly on the line splitting and the echo time.

  20. Advanced NMR-based techniques for pore structure analysis of coal. Quarter report No. 4, 1 October 1992--30 December 1992

    SciTech Connect

    Smith, D.M.

    1992-12-31

    One of the main problems in coal utilization is the inability to properly characterize its complex pore structure. Coals typically have micro/ultra-micro pores but they also exhibit meso and macroporosity. Conventional pore size techniques (adsorption/condensation, mercury porosimetry) are limited because of this broad pore size range, microporosity, reactive nature of coal, samples must be completely dried, and network/percolation effects. Small angle scattering is limited because it probes both open and closed pores. Although one would not expect any single technique to provide a satisfactory description of a coal`s structure, it is apparent that better techniques are necessary. We believe that measurement of the NMR parameters of various gas phase and adsorbed phase NMR active probes can provide the resolution to this problem. We will investigate the dependence of the common NMR parameters such as chemical shifts and relaxation times of several different nuclei and compounds on the pore structure of model microporous solids, carbons, and coals. In particular, we will study the interaction between several small molecules and the pore surfaces in coals. These molecules have been selected for their chemical and physical properties. A special NMR probe will be constructed which will allow the concurrent measurement of NMR properties and adsorption uptake at a variety of temperatures. All samples will be subjected to a suite of ``conventional`` pore structure analyses. These include nitrogen adsorption at 77 K with BET analysis, CO{sub 2} and CH{sub 4} adsorption at 273 K with D-R (Dubinin-Radushkevich) analysis, helium pycnometry, and small angle X-ray scattering as well as gas diffusion measurements.

  1. Reconstruction of adsorption potential in Polanyi-based models and application to various adsorbents.

    PubMed

    Pan, Bingjun; Zhang, Huichun

    2014-06-17

    The equilibrium Polanyi adsorption potential was reconstructed as ε = -RT ln(Ca(or H)/δ) to correlate the characteristic energy (E) of Polanyi-based models (qe = f[ε/E]) with the properties or structures of absorbates, where qe is the equilibriumn adsorption capacity, Ca(or H) is the converted concentration from the equilibrium aqueous concentration at the same activity and corresponds to the adsorption from the gas or n-hexadecane (HD) phase by the water-wet adsorbent, and "δ" is an arbitrary divisor to converge the model fitting. Subsequently, the modified Dubinin-Astakhov model based on the reconstructed ε was applied to aqueous adsorption on activated carbon, black carbon, multiwalled carbon nanotubes, and polymeric resin. The fitting results yielded intrinsic characteristic energies Ea, derived from aqueous-to-gas phase conversion, or EH, derived from aqueous-to-HD phase conversion, which reflect the contributions of the overall or specific adsorbate-adsorbent interactions to the adsorption. Effects of the adsorbate and adsorbent properties on Ea or EH then emerge that are unrevealed by the original characteristic energy (Eo), i.e., adsorbates with tendency to form stronger interactions with an adsorbent have larger Ea and EH. Additionally, comparison of Ea and EH allows quantitative analysis of the contributions of nonspecific interactions, that is, a significant relationship was established between the nonspecific interactions and Abraham's descriptors for the adsorption of all 32 solutes on the four different adsorbents: (Ea - EH) = 24.7 × V + 9.7 × S - 19.3 (R(2) = 0.97), where V is McGowan's characteristic volume for adsorbates, and S reflects the adsorbate's polarity/polarizability. PMID:24815932

  2. Advanced NMR-based techniques for pore structure analysis of coal. Quarterly report No. 7, April 1, 1993--June 31, 1993

    SciTech Connect

    Smith, D.M.

    1993-09-01

    One of the main problems in coal utilization is the inability to properly characterize its complex pore structure. Coals typically have micro/ultramicro pores but they also exhibit meso and macroporosity. Conventional pore size techniques (adsorption/condensation, mercury porosimetry) are limited because of this broad pore size range, microporosity, reactive nature of coal, samples must be completely dried, and network/percolation effects. Small angle scattering is limited because it probes both open and closed pores. Although one would not expect any single technique to provide a satisfactory description of a coal`s structure, it is apparent that better techniques are necessary. Small angle scattering could be improved by combining scattering and adsorption measurements. Also, the measurement of NMR parameters of various gas phase and adsorbed phase NMR active probes can provide pore structure information. We will investigate the dependence of the common NMR parameters such as chemical shifts and relaxation times of several different nuclei and compounds on the pore structure of model microporous solids, carbons, and coals. In particular, we will study the interaction between several small molecules ({sup 129}Xe, {sup 3}He, {sup 2}H{sub 2},{sup 14}N{sub 2}, {sup 14}NH{sub 3}, {sup 15}N{sub 2},{sup 13}CH{sub 4}, {sup 13}CO{sub 2}) and the pore surfaces in coals.

  3. Advanced NMR-based techniques for pore structure analysis of coal. Quarterly report No. 3, July 1, 1992--September 30, 1992

    SciTech Connect

    Smith, D.M.

    1992-12-31

    One of the main problems in coal utilization is the inability to properly characterize its complex pore structure. Coals typically have micro/ultra-micro pores but they also exhibit meso and macroporosity. Conventional pore size techniques (adsorption/condensation, mercury porosimetry) are limited because of this broad pore size range, microporosity, reactive nature of coal, samples must be completely dried, and network/percolation effects. Small angle scattering is limited because it probes both open and closed pores. Although one would not expect any single technique to provide a satisfactory description of a coal`s structure, it is apparent that better techniques are necessary. We believe that measurement of the NMR parameters of various gas phase and adsorbed phase NMR active probes can provide the resolution to this problem. We now have two suites of well-characterized microporous materials including oxides (zeolites and silica gel) and activated carbons from our industrial partner, Air Products in Allentown, PA. Our current work may be divided into three areas: small-angle X-ray scattering (SAXS), adsorption, and NMR.

  4. Advanced NMR-based techniques for pore structure analysis of coal. Quarter report {number_sign}8, 7/1/93--9/30/93

    SciTech Connect

    Smith, D.M.

    1993-12-31

    One of the main problems in coal utilization is the inability to properly characterize its complex pore structure. Coals typically have micro/ultramicro pores but they also exhibit meso and macroporosity. Conventional pore size techniques (adsorption/condensation, mercury porosimetry) are limited because of this broad pore size range, microporosity, reactive nature of coal, samples must be completely dried, and network/percolation effects. Small angle scattering is limited because it probes both open and closed pores. Although one would not expect any single technique to provide a satisfactory description of a coal`s structure, it is apparent that better techniques are necessary. Small angle scattering could be improved by combining scattering and adsorption measurements. Also, the measurement of NMR parameters of various gas phase and adsorbed phase NMR active probes can provide pore structure information. The dependence of the common NMR parameters such as chemical shifts and relaxation times of several different nuclei and compounds on the pore structure of model microporous solids, carbons, and coals is investigated. In particular, the interaction between several small molecules ({sup 129}Xe, {sup 3}He, {sup 14}N{sub 2},{sup 14}NH{sub 3},{sup 15}N{sub 2},{sup 13} CH{sub 4}, {sup 13}CO{sub 2}) and pore surface is studied.

  5. Advanced NMR-based techniques for pore structure analysis of coal. Quarterly report No. 6, January 1, 1993--March 31, 1993

    SciTech Connect

    Smith, D.M.

    1993-08-01

    One of the main problems in coal utilization is the inability to properly characterize its complex pore structure. Coals typically have micro/ultra-micro pores but they also exhibit meso and macroporosity. Conventional pore size techniques (adsorption/condensation, mercury porosimetry) are limited because of this broad pore size range, microporosity, reactive nature of coal, samples must be completely dried, and network/percolation effects. Small angle scattering is limited because it probes both open and closed pores. Although one would not expect any single technique to provide a satisfactory description of a coal`s structure, it is apparent that better techniques are necessary. Small angle scattering could be improved by combining scattering and adsorption measurements. Also, the measurement of NMR parameters of various gas phase and adsorbed phase NMR active probes can provide pore structure information. We will investigate the dependence of the common NMR parameters such as chemical shifts and relaxation times of several different nuclei and compounds on the pore structure of model microporous solids, carbons, and coals. In particular, we will study the interaction between several small molecules ({sup 129}Xe, {sup 3}He, {sup 2}H{sub 2}, {sup 14}N{sub 2},{sup 14}NH{sub 3}, {sup 15}N{sup 2}, {sup 13}CH{sub 4}, {sup 13}CO{sub 2}) and the pore surfaces in coals.

  6. Hydrogen Adsorption in Carbon-Based Materials Studied by NMR

    NASA Astrophysics Data System (ADS)

    Wu, Yue; Kleinhammes, Alfred; Anderson, Robert; Mao, Shenghua

    2007-03-01

    Hydrogen adsorption in carbon-based materials such as boron-doped graphite and boron-doped single-walled carbon nanotubes (SWNTs) were investigated by nuclear magnetic resonance (NMR). ^1H NMR is shown to be a sensitive and quantitative probe for detecting adsorbed gas molecules such as H2, methane, and ethane. NMR measurements were carried out in-situ under given H2 pressure up to a pressure of over 100 atm. From such ^1H NMR measurement, the amount of adsorbed H2 molecules was determined versus pressure. This gives an alternative method for measuring the adsorption isotherms where the H2 signature is identified based on spin properties rather than weight or volume as in gravimetric and volumetric measurements. The measurement shows that boron doping has a favorable effect on increasing the adsorption enthalpy of H2 in carbon-based systems. This work was done in collaboration with NREL and Department of Chemistry, University of Pennsylvania, within the DOE Center of Excellence on Carbon-based Hydrogen Storage Materials and is supported by DOE.

  7. Integrated system for temperature-controlled fast protein liquid chromatography comprising improved copolymer modified beaded agarose adsorbents and a travelling cooling zone reactor arrangement.

    PubMed

    Müller, Tobias K H; Cao, Ping; Ewert, Stephanie; Wohlgemuth, Jonas; Liu, Haiyang; Willett, Thomas C; Theodosiou, Eirini; Thomas, Owen R T; Franzreb, Matthias

    2013-04-12

    An integrated approach to temperature-controlled chromatography, involving copolymer modified agarose adsorbents and a novel travelling cooling zone reactor (TCZR) arrangement, is described. Sepharose CL6B was transformed into a thermoresponsive cation exchange adsorbent (thermoCEX) in four synthetic steps: (i) epichlorohydrin activation; (ii) amine capping; (iii) 4,4'-azobis(4-cyanovaleric acid) immobilization; and 'graft from' polymerization of poly(N-isopropylacrylamide-co-N-tert-butylacrylamide-co-acrylic acid-co-N,N'-methylenebisacrylamide). FT-IR, (1)H NMR, gravimetry and chemical assays allowed precise determination of the adsorbent's copolymer composition and loading, and identified the initial epoxy activation step as a critical determinant of 'on-support' copolymer loading, and in turn, protein binding performance. In batch binding studies with lactoferrin, thermoCEX's binding affinity and maximum adsorption capacity rose smoothly with temperature increase from 20 to 50 °C. In temperature shifting chromatography experiments employing thermoCEX in thermally jacketed columns, 44-51% of the lactoferrin adsorbed at 42 °C could be desorbed under binding conditions by cooling the column to 22 °C, but the elution peaks exhibited strong tailing. To more fully exploit the potential of thermoresponsive chromatography adsorbents, a new column arrangement, the TCZR, was developed. In TCZR chromatography, a narrow discrete cooling zone (special assembly of copper blocks and Peltier elements) is moved along a bespoke fixed-bed separation columnfilled with stationary phase. In tests with thermoCEX, it was possible to recover 65% of the lactoferrin bound at 35 °C using 8 successive movements of the cooling zone at a velocity of 0.1mm/s; over half of the recovered protein was eluted in the first peak in more concentrated form than in the feed. Intra-particle diffusion of desorbed protein out of the support pores, and the ratio between the velocities of the cooling

  8. Topological features of engineered arrays of adsorbates in honeycomb lattices

    NASA Astrophysics Data System (ADS)

    Gonzalez-Arraga, Luis A.; Lado, J. L.; Guinea, Francisco

    2016-09-01

    Hydrogen adatoms are one of the most the promising proposals for the functionalization of graphene. The adatoms induce narrow resonances near the Dirac energy, which lead to the formation of magnetic moments. Furthermore, they also create local lattice distortions which enhance the spin-orbit coupling. The combination of magnetism and spin-orbit coupling allows for a rich variety of phases, some of which have non-trivial topological features. We analyze the interplay between magnetism and spin-orbit coupling in ordered arrays of adsorbates on honeycomb lattice monolayers, and classify the different phases that may arise. We extend our model to consider arrays of adsorbates in graphene-like crystals with stronger intrinsic spin-orbit couplings. We also consider a regime away from half-filling in which the Fermi level is at the bottom of the conduction band, we find a Berry curvature distribution corresponding to a Valley-Hall effect.

  9. pyIAST: Ideal adsorbed solution theory (IAST) Python package

    NASA Astrophysics Data System (ADS)

    Simon, Cory M.; Smit, Berend; Haranczyk, Maciej

    2016-03-01

    Ideal adsorbed solution theory (IAST) is a widely-used thermodynamic framework to readily predict mixed-gas adsorption isotherms from a set of pure-component adsorption isotherms. We present an open-source, user-friendly Python package, pyIAST, to perform IAST calculations for an arbitrary number of components. pyIAST supports several common analytical models to characterize the pure-component isotherms from experimental or simulated data. Alternatively, pyIAST can use numerical quadrature to compute the spreading pressure for IAST calculations by interpolating the pure-component isotherm data. pyIAST can also perform reverse IAST calculations, where one seeks the required gas phase composition to yield a desired adsorbed phase composition.

  10. Studies on 2H NMR and single crystal X-ray diffraction of thermochromic bis ( N, N-diethyl-1,2-ethanediamine) nickel(II) complexes with and without structural phase transitions

    NASA Astrophysics Data System (ADS)

    Ikeda, Ryuichi; Kotani, Kyoko; Ohki, Hiroshi; Ishimaru, Shin'ichi; Okamoto, Ken-Ichi; Ghosh, Ashutosh

    1995-02-01

    The thermochromic complex bis( N, N-diethyl-1,2-ethanediamine) ((C 2H 5) 2NC 2H 4NH 2) nickel(II) perchlorate([Ni(dieten) 2](ClO 4) 2) was studied by single crystal X-ray diffraction and found to form a triclinic lattice with space group P 1¯, a = 8.108(1) Å, b = 8.835(1) Å, c = 9.736(1) Å, α = 94.24(1)°, β = 114.28(1)°, γ = 116.49(1)°, and Z = 1 being isomorphous with that of [Cu(dieten) 2](ClO 4) 2 which has been reported to have a thermochromic phase transition. The temperature dependences of 2H NMR spectra in [Ni(dieten- d2) 2]X 2 (dieten- d2: (C 2H 5) 2NC 2H 4ND 2; X: ClO 4, BF 4, Br, NO 3, I) were observed and quadrupole coupling constants e2Qq and asymmetry parameters η were evaluated. Below room temperature, an almost rigid structure of the ND 2 group was derived by analyzing the spectra. For perchlorate and tetrafluoroborate with colour changes at respective phase transition temperatures ( Tc), quadrupole parameters were also changed discontinuously at Tc. The analysis of spectra observed above Tc afforded two-site jumps of the N-D bond by angles of 52-55° supporting the ring-puckering model of the five-membered chelate ring. However, iodide having no phase transition showed continuous changes of both e2Qq and η values with increasing temperature up to 450 K. These results which cannot be attributed to the puckering motion were explained by whole complex reorientation. These molecular motions are discussed in connection with the colour change observed in these complexes.

  11. Quasiparticle excitations of adsorbates on doped graphene

    NASA Astrophysics Data System (ADS)

    Lischner, Johannes; Wickenburg, Sebastian; Wong, Dillon; Karrasch, Christoph; Wang, Yang; Lu, Jiong; Omrani, Arash A.; Brar, Victor; Tsai, Hsin-Zon; Wu, Qiong; Corsetti, Fabiano; Mostofi, Arash; Kawakami, Roland K.; Moore, Joel; Zettl, Alex; Louie, Steven G.; Crommie, Mike

    Adsorbed atoms and molecules can modify the electronic structure of graphene, but in turn it is also possible to control the properties of adsorbates via the graphene substrate. In my talk, I will discuss the electronic structure of F4-TCNQ molecules on doped graphene and present a first-principles based theory of quasiparticle excitations that captures the interplay of doping-dependent image charge interactions between substrate and adsorbate and electron-electron interaction effects on the molecule. The resulting doping-dependent quasiparticle energies will be compared to experimental scanning tunnelling spectra. Finally, I will also discuss the effects of charged adsorbates on the electronic structure of doped graphene.

  12. Interactions of organic contaminants with mineral-adsorbed surfactants

    USGS Publications Warehouse

    Zhu, L.; Chen, B.; Tao, S.; Chiou, C.T.

    2003-01-01

    Sorption of organic contaminants (phenol, p-nitrophenol, and naphthalene) to natural solids (soils and bentonite) with and without myristylpyridinium bromide (MPB) cationic surfactant was studied to provide novel insight to interactions of contaminants with the mineral-adsorbed surfactant. Contaminant sorption coefficients with mineral-adsorbed surfactants, Kss, show a strong dependence on surfactant loading in the solid. At low surfactant levels, the Kss values increased with increasing sorbed surfactant mass, reached a maximum, and then decreased with increasing surfactant loading. The Kss values for contaminants were always higher than respective partition coefficients with surfactant micelles (Kmc) and natural organic matter (Koc). At examined MPB concentrations in water the three organic contaminants showed little solubility enhancement by MPB. At low sorbed-surfactant levels, the resulting mineral-adsorbed surfactant via the cation-exchange process appears to form a thin organic film, which effectively "adsorbs" the contaminants, resulting in very high Kss values. At high surfactant levels, the sorbed surfactant on minerals appears to form a bulklike medium that behaves essentially as a partition phase (rather than an adsorptive surface), with the resulting Kss being significantly decreased and less dependent on the MPB loading. The results provide a reference to the use of surfactants for remediation of contaminated soils/sediments or groundwater in engineered surfactant-enhanced washing.

  13. Solid state NMR and LVSEM studies on the hardening of latex modified tile mortar systems

    SciTech Connect

    Rottstegge, J.; Arnold, M.; Herschke, L.; Glasser, G.; Wilhelm, M.; Spiess, H.W. . E-mail: spiess@mpip-mainz.mpg.de; Hergeth, W.D.

    2005-12-15

    Construction mortars contain a broad variety of both inorganic and organic additives beside the cement powder. Here we present a study of tile mortar systems based on portland cement, quartz, methyl cellulose and different latex additives. As known, the methyl cellulose stabilizes the freshly prepared cement paste, the latex additive enhances final hydrophobicity, flexibility and adhesion. Measurements were performed by solid state nuclear magnetic resonance (NMR) and low voltage scanning electron microscopy (LVSEM) to probe the influence of the latex additives on the hydration, hardening and the final tile mortar properties. While solid state NMR enables monitoring of the bulk composition, scanning electron microscopy affords visualization of particles and textures with respect to their shape and the distribution of the different phases. Within the alkaline cement paste, the poly(vinyl acetate) (VAc)-based latex dispersions stabilized by poly(vinyl alcohol) (PVA) were found to be relatively stable against hydrolysis. The influence of the combined organic additives methyl cellulose, poly(vinyl alcohol) and latexes stabilized by poly(vinyl alcohol) on the final silicate structure of the cement hydration products is small. But even small amounts of additives result in an increased ratio of ettringite to monosulfate within the final hydrated tile mortar as monitored by {sup 27}Al NMR. The latex was found to be adsorbed to the inorganic surfaces, acting as glue to the inorganic components. For similar latex water interfaces built up by poly(vinyl alcohol), a variation in the latex polymer composition results in modified organic textures. In addition to the networks of the inorganic cement and of the latex, there is a weak network build up by thin polymer fibers, most probably originating from poly(vinyl alcohol). Besides the weak network, polymer fibers form well-ordered textures covering inorganic crystals such as portlandite.

  14. NMR Stark Spectroscopy: New Methods to Calibrate NMR Sensitivity to Electric Fields

    NASA Astrophysics Data System (ADS)

    Tarasek, Matthew R.

    The influence of electrostatics on NMR parameters is well accepted. Thus, NMR is a promising route to probe electrical features within molecules and materials. However, applications of NMR Stark effects (E-field induced changes in spin energy levels) have been elusive. I have developed new approaches to resolve NMR Stark effects from an applied E field. This calibrates nuclear probes whose spectral response might later be used to evaluate internal E fields that are critical to function, such as those due to local charge distributions or sample structure. I will present two novel experimental approaches for direct calibration of NMR quadrupolar Stark effects (QSEs). In the first, steady-state (few-second) excitation by an E field at twice the NMR frequency (2ω 0) is used to saturate spin magnetization. The extent of saturation vs. E-field amplitude calibrates the QSE response rate, while measurements vs sample orientation determine tensorial character. The second method instead synchronizes short (few µs) pulses of the 2ω0 E field with a multiple-pulse NMR sequence. This, “POWER” (Perturbations Observed With Enhanced Resolution) approach enables more accurate measure of small QSEs (i.e. few Hz spectral changes). A 2nd key advantage is the ability to define tensorial response without reorienting the sample, but instead varying the phase of the 2ω0 field. I will describe these experiments and my home-built NMR “Stark probe”, employed on a conventional wide-bore solid-state NMR system. Results with GaAs demonstrate each method, while extensions to a wider array of molecular and material systems may now be possible using these methods.

  15. 1H NMR relaxation in urea

    NASA Astrophysics Data System (ADS)

    Taylor, R. E.; Bacher, Alfred D.; Dybowski, C.

    2007-11-01

    Proton NMR spin-lattice relaxation times T1 were measured for urea as a function of temperature. An activation energy of 46.3 ± 4.7 kJ/mol was extracted and compared with the range of 38-65 kJ/mol previously reported in the literature as measured by different magnetic resonance techniques. In addition, proton NMR spin-lattice relaxation times in the rotating frame T1 ρ were measured as a function of temperature. These measurements provide acquisition conditions for the 13C and 15N CP/MAS spectra of pure urea in the crystalline phase.

  16. pH-controlled quaternary ammonium herbicides capture/release by carboxymethyl-β-cyclodextrin functionalized magnetic adsorbents: Mechanisms and application.

    PubMed

    Liu, Chang; Wang, Peng; Shen, Zhigang; Liu, Xueke; Zhou, Zhiqiang; Liu, Donghui

    2015-12-11

    In our work, the pH-controlled magnetic solid phase extraction for the determination of paraquat and diquat was introduced firstly. Furthermore, to clarify the mechanism of carboxymethyl-β-cyclodextrin functionalized magnetic adsorbents, we studied the pH-responsive supramolecular interaction between carboxymethyl-β-cyclodextrin (CM-β-CD) and paraquat/diquat by ultraviolet-visible (UV-vis) spectroscopy and nuclear magnetic resonance (NMR) experiment, and the energy-minimized structures were also obtained. Then, the functional group CM-β-CD was modified on the surface of magnetic materials to synthesize the adsorbent. The Fourier transform infrared spectrum (FT-IR) results proved the successful modification of CM-β-CD. Thus, this absorbent was applied for the determination of paraquat and diquat in water. Under the optimal condition, limits of detection (LODs) of paraquat and diquat were 0.8 μg L(-1) and 0.9 μg L(-1), relative standard deviations (RSD) and recoveries varied 0.7-4.6% and 86.5-106.6%, respectively. Good recoveries (70.2-100.0%) and low RSD (1.7-9.6%) were achieved in analyzing spiked water samples. Furthermore, with the capillary electrophoresis (CE) as the analyser, the whole analytical process did not need the attendance of organic solvents. PMID:26614057

  17. Solid-state NMR and ESR studies of activated carbons produced from pecan shells

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Activated carbon from pecan shells has shown promise as an adsorbent in water treatment and sugar refining. However, the chemistry of the material is complex and not fully understood. We report here the application of solid state NMR and ESR to study the chemical structure, mobility, and pore volu...

  18. The uranium from seawater program at PNNL: Overview of marine testing, adsorbent characterization, adsorbent durability, adsorbent toxicity, and deployment studies

    DOE PAGESBeta

    Gill, Gary A.; Kuo, Li -Jung; Janke, Christopher James; Park, Jiyeon; Jeters, Robert T.; Bonheyo, George T.; Pan, Horng -Bin; Wai, Chien; Khangaonkar, Tarang P.; Bianucci, Laura; et al

    2016-02-07

    The Pacific Northwest National Laboratory's (PNNL) Marine Science Laboratory (MSL) located along the coast of Washington State is evaluating the performance of uranium adsorption materials being developed for seawater extraction under realistic marine conditions with natural seawater. Two types of exposure systems were employed in this program: flow-through columns for testing of fixed beds of individual fibers and pellets and a recirculating water flume for testing of braided adsorbent material. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time, typically 42 to 56 day exposures, to determine the adsorbent capacitymore » and adsorption rate (kinetics). Analysis of uranium and other trace elements collected by the adsorbents was conducted following strong acid digestion of the adsorbent with 50% aqua regia using either Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The ORNL 38H adsorbent had a 56 day adsorption capacity of 3.30 ± 0.68 g U/ kg adsorbent (normalized to a salinity of 35 psu), a saturation adsorption capacity of 4.89 ± 0.83 g U/kg of adsorbent material (normalized to a salinity of 35 psu) and a half-saturation time of 28 10 days. The AF1 adsorbent material had a 56 day adsorption capacity of 3.9 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu), a saturation capacity of 5.4 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu) and a half saturation time of 23 2 days. The ORNL amidoxime-based adsorbent materials are not specific for uranium, but also adsorb other elements from seawater. The major doubly charged cations in seawater (Ca and Mg) account for a majority of the cations adsorbed (61% by mass and 74% by molar percent). For the ORNL AF1 adsorbent material, U is the 4th most abundant element adsorbed by mass and 7th most abundant by molar percentage. Marine testing

  19. The Uranium from Seawater Program at PNNL: Overview of marine testing, adsorbent characterization, adsorbent durability, adsorbent toxicity, and deployment studies

    SciTech Connect

    Gill, Gary; Kuo, Li-Jung; Janke, Christopher James; Park, Jiyeon; Jeters, Robert T; Bonheyo, George; Pan, Horng-Bin; Wai, Chien; Khangaonkar, Tarang P; Bianucci, Laura; Wood, Jordana; Warner, Marvin G; Peterson, Sonja; Abrecht, David; Mayes, Richard T; Tsouris, Costas; Oyola, Yatsandra; Strivens, Jonathan E.; Schlafer, Nicholas; Addleman, Shane R; Chouyyok, Wilaiwan; Das, Sadananda; Kim, Jungseung; Buesseler, Dr. Ken; Breier, Crystalline; D'Alessandro, Dr. Evan

    2016-01-01

    The Pacific Northwest National Laboratory s (PNNL) Marine Science Laboratory (MSL) located along the coast of Washington State is evaluating the performance of uranium adsorption materials being developed for seawater extraction under realistic marine conditions with natural seawater. Two types of exposure systems were employed in this program: flow-through columns for testing of fixed beds of individual fibers and pellets and a recirculating water flume for testing of braided adsorbent material. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time, typically 42 to 56 day exposures, to determine the adsorbent capacity and adsorption rate (kinetics). Analysis of uranium and other trace elements collected by the adsorbents was conducted following strong acid digestion of the adsorbent with 50% aqua regia using either Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The ORNL 38H adsorbent had a 56 day adsorption capacity of 3.30 0.68 g U/ kg adsorbent (normalized to a salinity of 35 psu), a saturation adsorption capacity of 4.89 0.83 g U/kg of adsorbent material (normalized to a salinity of 35 psu) and a half-saturation time of 28 10 days. The AF1 adsorbent material had a 56 day adsorption capacity of 3.9 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu), a saturation capacity of 5.4 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu) and a half saturation time of 23 2 days. The ORNL amidoxime-based adsorbent materials are not specific for uranium, but also adsorb other elements from seawater. The major doubly charged cations in seawater (Ca and Mg) account for a majority of the cations adsorbed (61% by mass and 74% by molar percent). For the ORNL AF1 adsorbent material, U is the 4th most abundant element adsorbed by mass and 7th most abundant by molar percentage. Marine testing at Woods Hole

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

    SciTech Connect

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

    2014-04-30

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

  1. Solid phase synthesis, NMR structure determination of α-KTx3.8, its in silico docking to Kv1.x potassium channels, and electrophysiological analysis provide insights into toxin-channel selectivity.

    PubMed

    Kohl, Bastian; Rothenberg, Ina; Ali, Syed Abid; Alam, Mehtab; Seebohm, Guiscard; Kalbacher, Hubert; Voelter, Wolfgang; Stoll, Raphael

    2015-07-01

    Animal venoms, such as those from scorpions, are a potent source for new pharmacological substances. In this study we have determined the structure of the α-KTx3.8 (named as Bs6) scorpion toxin by multidimensional (1)H homonuclear NMR spectroscopy and investigated its function by molecular dynamics (MD) simulations and electrophysiological measurements. Bs6 is a potent inhibitor of the Kv1.3 channel which plays an important role during the activation and proliferation of memory T-cells (TEM), which play an important role in autoimmune diseases. Therefore, it could be an interesting target for treatment of autoimmune diseases. In this study, Bs6 was synthesised by solid phase synthesis and its three-dimensional (3D) structure has been determined. To gain a deeper insight into the interaction of Bs6 with different potassium channels like hKv1.1 and hKv1.3, the protein-protein complex was modelled based on known toxin-channel structures and tested for stability in MD simulations using GROMACS. The toxin-channel interaction was further analysed by electrophysiological measurements of different potassium channels like hKv1.3 and hKv7.1. As potassium channel inhibitors could play an important role to overcome autoimmune diseases like multiple sclerosis and type-1 diabetes mellitus, our data contributes to the understanding of the molecular mechanism of action and will ultimately help to develop new potent inhibitors in future. PMID:25953725

  2. Magnetic reduced graphene oxide functionalized with β-cyclodextrin as magnetic solid-phase extraction adsorbents for the determination of phytohormones in tomatoes coupled with high performance liquid chromatography.

    PubMed

    Li, Na; Chen, Juan; Shi, Yan-Ping

    2016-04-01

    A β-cyclodextrin (β-CD) functionalized magnetic reduced graphene oxide composite (Fe3O4/RGO@β-CD) has been prepared and its application as a selective adsorbent for the determination of the two naphthalene-derived phytohormones (1-naphthalene acetic acid (NAA) and 2-naphthoxyacetic acid (2-NOA)) has been investigated. Magnetic reduced graphene oxide composite (Fe3O4/RGO) was first synthesized via in situ chemical precipitation method and then β-CD was applied to further functionalize the resultant Fe3O4/RGO composite. The as-prepared Fe3O4/RGO@β-CD was characterized by Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Compared with Fe3O4/RGO, the as-prepared Fe3O4/RGO@β-CD showed better molecular selectivity and higher extraction efficiency for NAA and 2-NOA by dint of the size complementarity brought by the introduction of β-CD. Response surface methodology (RSM), a multivariate experimental design technique, was used to optimize experimental parameters affecting the extraction efficiency in detail. Under the optimal conditions, good performance data was obtained. The calibration curves were linear over the concentration ranging from 2 to 600 ngg(-1) with correlation coefficients (R(2)) between 0.9995 and 0.9997 for all the analytes. The limits of detection (LODs) were 0.67 ngg(-1) for both NAA and 2-NOA. The intra- and inter-day relative standard deviations (RSDs) were less than 6.02% and 7.34%, respectively. The recoveries ranged from 91.45% to 95.89%. Taken together, the proposed method was an efficient pretreatment and enrichment procedure and could be successfully applied for selective extraction and determination of naphthalene-derived phytormones in complex matrices. PMID:26949214

  3. Heat capacity of multilayers of 3He adsorbed on graphite at low millikelvin temperatures

    NASA Astrophysics Data System (ADS)

    Greywall, Dennis S.

    1990-02-01

    Precise heat-capacity results are presented for 3He adsorbed on graphite. The temperature range of the data is from 2 to 200 mK, while the coverages span from somewhat below monolayer completion up through five atomic layers. Promotion of atoms into the second, third, and fourth layers is clearly observed. Nuclear-spin exchange energies of the order of a few tenths of a mK are found for the submonolayer incommensurate solid phase. These values differ significantly from those recently inferred from NMR experiments. Data for the second-layer fluid yield 3He quasiparticle effective masses that agree well with the corresponding first-layer values and range from one to five times the bare 3He mass. Prior to third-layer promotion, the second layer undergoes a first-order phase transition. By comparison with the phase diagram for the first layer, the new phase in the second layer is assumed to be a registered solid. Registry is now with respect to the first 3He layer, which continues to exist as a triangular-lattice solid incommensurate with the graphite substrate. The registered phase exhibits a large, sharp heat-capacity anomaly at 2.5 mK. This anomaly may be due to antiferromagnetic polarons which form around zero-point vacancies or may be the signature of an unusual registered phase in which some of the atoms are positioned at substrate potential maxima. As the coverage is increased further, the second-layer spin peak remains located at 2.5 mK but suddenly grows in amplitude, while the temperature dependence above the peak changes from T-0.5 towards T-2. The anomaly reaches its greatest magnitude at 0.24 atoms/AṦ where, perhaps coincidentally, promotion of atoms into the fourth layer also occurs. At this same coverage previous magnetization measurements have shown a large ferromagnetic peak. The heat-capacity data indicate that the ferromagnetic peak occurs when the second layer exists in a state intermediate between a registered solid and the incommensurate

  4. Experimental study of a three-adsorber sorption refrigerator for utilization of renewable sources of energy

    NASA Astrophysics Data System (ADS)

    Tsitovich, A. P.

    2013-03-01

    A three-adsorber refrigerator has been created and experimentally tested, in which use is made of a composite sorbent consisting of activated carbon fiber and alkali salts. This sorbent has a high capacity of storage of refrigeration characteristic of chemical coolers and a high sorption rate characteristic of adsorption refrigerators. The sorbent structure makes it possible to effect a convective intrapore process of cooling of the sorbent through intense two-phase heat transfer. A three-adsorber refrigerator has a higher refrigeration efficiency and smaller mass and overall dimensions than a traditional two-stage four-adsorber refrigerator.

  5. NMR imaging microscopy

    SciTech Connect

    Not Available

    1986-10-01

    In the past several years, proton nuclear magnetic resonance (NMR) imaging has become an established technique in diagnostic medicine and biomedical research. Although much of the work in this field has been directed toward development of whole-body imagers, James Aguayo, Stephen Blackband, and Joseph Schoeninger of the Johns Hopkins University School of Medicine working with Markus Hintermann and Mark Mattingly of Bruker Medical Instruments, recently developed a small-bore NMR microscope with sufficient resolution to image a single African clawed toad cell (Nature 1986, 322, 190-91). This improved resolution should lead to increased use of NMR imaging for chemical, as well as biological or physiological, applications. The future of NMR microscopy, like that of many other newly emerging techniques, is ripe with possibilities. Because of its high cost, however, it is likely to remain primarily a research tool for some time. ''It's like having a camera,'' says Smith. ''You've got a way to look at things at very fine levels, and people are going to find lots of uses for it. But it is a very expensive technique - it costs $100,000 to add imaging capability once you have a high-resolution NMR, which itself is at least a $300,000 instrument. If it can answer even a few questions that can't be answered any other way, though, it may be well worth the cost.''

  6. Fluorescence dynamics of microsphere-adsorbed sunscreens

    NASA Astrophysics Data System (ADS)

    Krishnan, R.

    2005-03-01

    Sunscreens are generally oily substances which are prepared in organic solvents, emulsions or dispersions with micro- or nanoparticles. These molecules adsorb to and integrate into skin cells. In order to understand the photophysical properties of the sunscreen, we compare steady-state and time-resolved fluorescence in organic solvent of varying dielectric constant ɛ and adsorbed to polystyrene microspheres and dispersed in water. Steady-state fluorescence is highest and average fluorescence lifetime longest in toluene, the solvent of lowest ɛ. However, there is no uniform dependence on ɛ. Sunscreens PABA and padimate-O show complex emission spectra. Microsphere-adsorbed sunscreens exhibit highly non-exponential decay, illustrative of multiple environments of the adsorbed molecule. The heterogeneous fluorescence dynamics likely characterizes sunscreen adsorbed to cells.

  7. Nanovalved Adsorbents for CH4 Storage.

    PubMed

    Song, Zhuonan; Nambo, Apolo; Tate, Kirby L; Bao, Ainan; Zhu, Minqi; Jasinski, Jacek B; Zhou, Shaojun J; Meyer, Howard S; Carreon, Moises A; Li, Shiguang; Yu, Miao

    2016-05-11

    A novel concept of utilizing nanoporous coatings as effective nanovalves on microporous adsorbents was developed for high capacity natural gas storage at low storage pressure. The work reported here for the first time presents the concept of nanovalved adsorbents capable of sealing high pressure CH4 inside the adsorbents and storing it at low pressure. Traditional natural gas storage tanks are thick and heavy, which makes them expensive to manufacture and highly energy-consuming to carry around. Our design uses unique adsorbent pellets with nanoscale pores surrounded by a coating that functions as a valve to help manage the pressure of the gas and facilitate more efficient storage and transportation. We expect this new concept will result in a lighter, more affordable product with increased storage capacity. The nanovalved adsorbent concept demonstrated here can be potentially extended for the storage of other important gas molecules targeted for diverse relevant functional applications. PMID:27124722

  8. Nuclear spin noise in NMR revisited

    SciTech Connect

    Ferrand, Guillaume; Luong, Michel

    2015-09-07

    The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a “bump” or as a “dip” superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.

  9. Nuclear spin noise in NMR revisited

    NASA Astrophysics Data System (ADS)

    Ferrand, Guillaume; Huber, Gaspard; Luong, Michel; Desvaux, Hervé

    2015-09-01

    The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a "bump" or as a "dip" superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.

  10. Separation of the attractive and repulsive contributions to the adsorbate-adsorbate interactions of polar adsorbates on Si(100)

    NASA Astrophysics Data System (ADS)

    Lin, Ying-Hsiu; Jeng, Horng-Tay; Lin, Deng-Sung

    2015-11-01

    Dissociative adsorption of H2O, NH3, CH3OH and CH3NH2 polar molecules on the Si(100) surface results in a 1:1 mixture of two adsorbates (H and multi-atomic fragment A = OH, NH2, CH3O, CH3NH, respectively) on the surface. By using density functional theory (DFT) calculations, the adsorption geometry, the total energies and the charge densities for various possible ordered structures of the mixed adsorbate layer have been found. Analyzing the systematic trends in the total energies unveils concurrently the nearest-neighbor interactions ENN and the next nearest-neighbor interactions ENNN between two polar adsorbates A. In going from small to large polar adsorbates, ENN's exhibit an attractive-to-repulsive crossover behavior, indicating that they include competing attractive and repulsive contributions. Exploration of the charge density distributions allows the estimation of the degree of charge overlapping between immediately neighboring A's, the resulting contribution of the steric repulsions, and that of the attractive interactions to the corresponding ENN's. The attractive contributions to nearest neighboring adsorbate-adsorbate interactions between the polar adsorbates under study are shown to result from hydrogen bonds or dipole-dipole interactions.

  11. Forsterite Carbonation in Wet-scCO2: Dependence on Adsorbed Water Concentration

    NASA Astrophysics Data System (ADS)

    Loring, J.; Benezeth, P.; Qafoku, O.; Thompson, C.; Schaef, T.; Bonneville, A.; McGrail, P.; Felmy, A.; Rosso, K.

    2013-12-01

    Capturing and storing CO2 in basaltic formations is one of the most promising options for mitigating atmospheric CO2 emissions resulting from the burning of fossil fuels. These geologic reservoirs have high reactive potential for CO2-mineral trapping due to an abundance of divalent-cation containing silicates, such as forsterite (Mg2SiO4). Recent studies have shown that carbonation of these silicates under wet scCO2 conditions, e. g. encountered near a CO2 injection well, proceeds along a different pathway and is more effective than in CO2-saturated aqueous fluids. The presence of an adsorbed water film on the forsterite surface seems to be key to reactivity towards carbonation. In this study, we employed in situ high pressure IR spectroscopy to investigate the dependence of adsorbed water film thickness on forsterite carbonation chemistry. Post reaction ex situ SEM, TEM, TGA, XRD, and NMR measurements will also be discussed. Several IR titrations were performed of forsterite with water at 50 °C and 90 bar scCO2. Aliquots of water were titrated at 4-hour reaction-time increments. Once a desired total water concentration was reached, data were collected for about another 30 hours. One titration involved 10 additions, which corresponds to 6.8 monolayers of adsorbed water. Clearly, a carbonate was precipitating, and its spectral signature matched magnesite. Another titration involved 8 aliquots, or up to 4.4 monolayers of water. The integrated absorbance under the CO stretching bands of carbonate as a function of time after reaching 4.4 monolayers showed an increase and then a plateau. We are currently unsure of the identity of the carbonate that precipitated, but it could be an amorphous anhydrous phase or magnesite crystals with dimensions of only several nanometers. A third titration only involved 3 additions, or up to 1.6 monolayers of water. The integrated absorbance under the CO stretching bands of carbonate as a function of time after reaching 1.6 monolayers

  12. Analysis of Adsorbate-Adsorbate and Adsorbate-Adsorbent Interactions to Decode Isosteric Heats of Gas Adsorption.

    PubMed

    Madani, S Hadi; Sedghi, Saeid; Biggs, Mark J; Pendleton, Phillip

    2015-12-21

    A qualitative interpretation is proposed to interpret isosteric heats of adsorption by considering contributions from three general classes of interaction energy: fluid-fluid heat, fluid-solid heat, and fluid-high-energy site (HES) heat. Multiple temperature adsorption isotherms are defined for nitrogen, T=(75, 77, 79) K, argon at T=(85, 87, 89) K, and for water and methanol at T=(278, 288, 298) K on a well-characterized polymer-based, activated carbon. Nitrogen and argon are subjected to isosteric heat analyses; their zero filling isosteric heats of adsorption are consistent with slit-pore, adsorption energy enhancement modelling. Water adsorbs entirely via specific interactions, offering decreasing isosteric heat at low pore filling followed by a constant heat slightly in excess of water condensation enthalpy, demonstrating the effects of micropores. Methanol offers both specific adsorption via the alcohol group and non-specific interactions via its methyl group; the isosteric heat increases at low pore filling, indicating the predominance of non-specific interactions. PMID:26538339

  13. Inorganic chemically active adsorbents (ICAAs)

    SciTech Connect

    Ally, M.R.; Tavlarides, L.

    1997-10-01

    Oak Ridge National Laboratory (ORNL) researchers are developing a technology that combines metal chelation extraction technology and synthesis chemistry. They begin with a ceramic substrate such as alumina, titanium oxide or silica gel because they provide high surface area, high mechanical strength, and radiolytic stability. One preparation method involves silylation to hydrophobize the surface, followed by chemisorption of a suitable chelation agent using vapor deposition. Another route attaches newly designed chelating agents through covalent bonding by the use of coupling agents. These approaches provide stable and selective, inorganic chemically active adsorbents (ICAAs) tailored for removal of metals. The technology has the following advantages over ion exchange: (1) higher mechanical strength, (2) higher resistance to radiation fields, (3) higher selectivity for the desired metal ion, (4) no cation exchange, (5) reduced or no interference from accompanying anions, (6) faster kinetics, and (7) easy and selective regeneration. Target waste streams include metal-containing groundwater/process wastewater at ORNL`s Y-12 Plant (multiple metals), Savannah River Site (SRS), Rocky Flats (multiple metals), and Hanford; aqueous mixed wastes at Idaho National Engineering Laboratory (INEL); and scrubber water generated at SRS and INEL. Focus Areas that will benefit from this research include Mixed Waste, and Subsurface Contaminants.

  14. Hydrogen adsorption of ruthenium: Isosteres of solubility of adsorbed hydrogen

    SciTech Connect

    Zaginaichenko, S.Y.; Matysina, Z.A.; Schur, D.V.; Pishuk, V.K.

    1998-12-31

    The theoretical investigation of solubility isosteres of adsorbed hydrogen has been performed for free face (0001) of crystals with hexagonal close-packed lattice A3 of Mg type. The face free energy has been calculated and its dependence on temperature, pressure, hydrogen concentration and character of hydrogen atoms distribution over surface interstitial sites of different type has been defined. The equations of thermodynamic equilibrium and solubility of adsorbed hydrogen have been defined. The plots of isosteres in the region of phase transition from isotropic to anisotropic state have been constructed and it has been established that in anisotropic state the order in distribution of hydrogen atoms over interstitial sites of different type must become apparent. Comparison of the theoretical isosteres with experimental for ruthenium has been carried out, the isotropic-anisotropic state transition can stipulate a stepwise and break-like change in isosteres.

  15. Theory of optical excitation of adsorbed rare gas atoms

    NASA Astrophysics Data System (ADS)

    Tsukada, Masaru; Brenig, Wilhelm

    1985-03-01

    Optical absorption spectra of rare-gas atoms adsorbed on metal surfaces exhibit a bimodal behavior, which, according to Cunningham, Greenlaw and Flynn, can be correlated with the difference I' - φ (where I' is the ionization energy of the excited (gas phase) state of the rare gas atom and φ the work function of the metal) controlling the energetics of charge transfer from the excited atom to the metal. In this paper we propose a model which allows to treat this charge transfer and some accompanying many-body effects in detail. Strong Coulomb attraction between the core hole and the excited electron on the adatom is taken into account as well as the interaction with surface plasmons. An improved charge transfer criterion is obtained which, besides the important parameter I∗ - φ, involves additional parameters such as the adsorbate-metal coupling strength and the plasmon frequency.

  16. Dual Species NMR Oscillator

    NASA Astrophysics Data System (ADS)

    Weber, Joshua; Korver, Anna; Thrasher, Daniel; Walker, Thad

    2016-05-01

    We present progress towards a dual species nuclear magnetic oscillator using synchronous spin exchange optical pumping. By applying the bias field as a sequence of alkali 2 π pulses, we generate alkali polarization transverse to the bias field. The alkali polarization is then modulated at the noble gas resonance so that through spin exchange collisions the noble gas becomes polarized. This novel method of NMR suppresses the alkali field frequency shift by at least a factor of 2500 as compared to longitudinal NMR. We will present details of the apparatus and measurements of dual species co-magnetometry using this method. Research supported by the NSF and Northrop-Grumman Corp.

  17. NMR studies of oriented molecules

    SciTech Connect

    Sinton, S.W.

    1981-11-01

    Deuterium and proton magnetic resonance are used in experiments on a number of compounds which either form liquid crystal mesophases themselves or are dissolved in a liquid crystal solvent. Proton multiple quantum NMR is used to simplify complicated spectra. The theory of nonselective multiple quantum NMR is briefly reviewed. Benzene dissolved in a liquid crystal are used to demonstrate several outcomes of the theory. Experimental studies include proton and deuterium single quantum (..delta..M = +-1) and proton multiple quantum spectra of several molecules which contain the biphenyl moiety. 4-Cyano-4'-n-pentyl-d/sub 11/-biphenyl (5CB-d/sub 11/) is studied as a pure compound in the nematic phase. The obtained chain order parameters and dipolar couplings agree closely with previous results. Models for the effective symmetry of the biphenyl group in 5CB-d/sub 11/ are tested against the experimental spectra. The dihedral angle, defined by the planes containing the rings of the biphenyl group, is found to be 30 +- 2/sup 0/ for 5DB-d/sub 11/. Experiments are also described for 4,4'-d/sub 2/-biphenyl, 4,4' - dibromo-biphenyl, and unsubstituted biphenyl.

  18. Site blocking effects on adsorbed polyacrylamide conformation

    NASA Astrophysics Data System (ADS)

    Brotherson, Brett A.

    The use of polymers as flocculating additives is a common practice in many manufacturing environments. However, exactly how these polymers interact with surfaces is relatively unknown. One specific topic which is thought to be very important to flocculation is an adsorbed polymer's conformation. Substantial amounts of previous work, mainly using simulations, have been performed to elucidate the theory surrounding adsorbed polymer conformations. Yet, there is little experimental work which directly verifies current theory. In order to optimize the use of polymer flocculants in industrial applications, a better understanding of an adsorbed polymer's conformation on a surface beyond theoretical simulations is necessary. This work looks specifically at site blocking, which has a broad impact on flocculation, adsorption, and surface modification, and investigated its effects on the resulting adsorbed polymer conformation. Experimental methods which would allow direct determination of adsorbed polymer conformational details and be comparable with previous experimental results were first determined or developed. Characterization of an adsorbed polymer's conformation was then evaluated using dynamic light scattering, a currently accepted experimental technique to examine this. This commonly used technique was performed to allow the comparison of this works results with past literature. Next, a new technique using atomic force microscopy was developed, building on previous experimental techniques, to allow the direct determination of an adsorbed polymer's loop lengths. This method also was able to quantify changes in the length of adsorbed polymer tails. Finally, mesoscopic simulation was attempted using dissipative particle dynamics. In order to determine more information about an adsorbed polymer's conformation, three different environmental factors were analyzed: an adsorbed polymer on a surface in water, an adsorbed polymer on a surface in aqueous solutions of varying

  19. Adsorbed natural gas storage with activated carbon

    SciTech Connect

    Sun, Jian; Brady, T.A.; Rood, M.J.

    1996-12-31

    Despite technical advances to reduce air pollution emissions, motor vehicles still account for 30 to 70% emissions of all urban air pollutants. The Clean Air Act Amendments of 1990 require 100 cities in the United States to reduce the amount of their smog within 5 to 15 years. Hence, auto emissions, the major cause of smog, must be reduced 30 to 60% by 1998. Natural gas con be combusted with less pollutant emissions. Adsorbed natural gas (ANG) uses adsorbents and operates with a low storage pressure which results in lower capital costs and maintenance. This paper describes the production of an activated carbon adsorbent produced from an Illinois coal for ANG.

  20. States of water adsorbed on perindopril crystals

    NASA Astrophysics Data System (ADS)

    Stepanov, V. A.; Khmelevskaya, V. S.; Bogdanov, N. Yu.; Gorchakov, K. A.

    2011-10-01

    The relationship between the structural state of adsorbed water, the crystal structure of the substances, and the solubility of the perindopril salt C19H32N2O5 · C4H11N in water was studied by IR spectroscopy and X-ray diffractometry. The high-frequency shift of the stretching vibrations of adsorbed water and the solubility depend on the crystal structure of the drug substance. A reversible chemical reaction occurred between the adsorbed water and the perindopril salt.

  1. Volumetric Interpretation of Protein Adsorption: Capacity Scaling with Adsorbate Molecular Weight and Adsorbent Surface Energy

    PubMed Central

    Parhi, Purnendu; Golas, Avantika; Barnthip, Naris; Noh, Hyeran; Vogler, Erwin A.

    2009-01-01

    Silanized-glass-particle adsorbent capacities are extracted from adsorption isotherms of human serum albumin (HSA, 66 kDa), immunoglobulin G (IgG, 160 kDa), fibrinogen (Fib, 341 kDa), and immunoglobulin M (IgM, 1000 kDa) for adsorbent surface energies sampling the observable range of water wettability. Adsorbent capacity expressed as either mass-or-moles per-unit-adsorbent-area increases with protein molecular weight (MW) in a manner that is quantitatively inconsistent with the idea that proteins adsorb as a monolayer at the solution-material interface in any physically-realizable configuration or state of denaturation. Capacity decreases monotonically with increasing adsorbent hydrophilicity to the limit-of-detection (LOD) near τo = 30 dyne/cm (θ~65o) for all protein/surface combinations studied (where τo≡γlvocosθ is the water adhesion tension, γlvo is the interfacial tension of pure-buffer solution, and θ is the buffer advancing contact angle). Experimental evidence thus shows that adsorbent capacity depends on both adsorbent surface energy and adsorbate size. Comparison of theory to experiment implies that proteins do not adsorb onto a two-dimensional (2D) interfacial plane as frequently depicted in the literature but rather partition from solution into a three-dimensional (3D) interphase region that separates the physical surface from bulk solution. This interphase has a finite volume related to the dimensions of hydrated protein in the adsorbed state (defining “layer” thickness). The interphase can be comprised of a number of adsorbed-protein layers depending on the solution concentration in which adsorbent is immersed, molecular volume of the adsorbing protein (proportional to MW), and adsorbent hydrophilicity. Multilayer adsorption accounts for adsorbent capacity over-and-above monolayer and is inconsistent with the idea that protein adsorbs to surfaces primarily through protein/surface interactions because proteins within second (or higher

  2. Screening proteins for NMR suitability

    PubMed Central

    Yee, Adelinda A.; Semesi, Anthony; Garcia, Maite; Arrowsmith, Cheryl H.

    2014-01-01

    Summary NMR spectroscopy is an invaluable tool in structural genomics. Identification of protein samples that are amenable to structure determination by NMR spectroscopy requires efficient screening. Here, we describe how we prepare multiple samples in parallel and screen by NMR. The method described here is applicable to large structural genomics projects but can easily be scaled down for application to small structural biology projects since all the equipments used are those commonly found in any NMR structural biology laboratory. PMID:24590717

  3. Modern NMR Spectroscopy.

    ERIC Educational Resources Information Center

    Jelinski, Lynn W.

    1984-01-01

    Discusses direct chemical information that can be obtained from modern nuclear magnetic resonance (NMR) methods, concentrating on the types of problems that can be solved. Shows how selected methods provide information about polymers, bipolymers, biochemistry, small organic molecules, inorganic compounds, and compounds oriented in a magnetic…

  4. Enantiodiscrimination by NMR spectroscopy.

    PubMed

    Uccello-Barretta, Gloria; Balzano, Federica; Salvadori, Piero

    2006-01-01

    The analysis of enantiorecognition processes involves the detection of enantiomeric species as well as the study of chiral discrimination mechanisms. In both fields Nuclear Magnetic Resonance (NMR) spectroscopy plays a fundamental role, providing several tools, based on the use of suitable chiral auxiliaries, for observing distinct signals of enantiomers and for investigating the complexation phenomena involved in enantiodiscrimination processes. PMID:17100610

  5. IR investigations of surfaces and adsorbates

    SciTech Connect

    Gwyn Williams

    2001-12-10

    Synchrotron infrared reflection-absorption measurements on single crystal metal surfaces with adsorbates have led to the determination of many key parameters related to the bonding vibrational modes and the dynamics of adsorbates. In particular, energy couplings between electrons and adsorbate motion have been shown to be a dominant mechanism on metal surfaces. Excellent agreement has been obtained with calculations for many of the observations, and the synergy between theory and experiment has led to a deeper understanding of the roles of electrons and phonons in determining the properties of interfaces and their roles in phenomena as diverse as friction, lubrication, catalysis and adhesion. Nonetheless, as the experiments are pushed harder, to describe such effects as co-adsorbed systems, disagreements continue to challenge the theory and our comprehension also is still evolving.

  6. PERVAPORATION USING ADSORBENT-FILLED MEMBRANES

    EPA Science Inventory

    Membranes containing selective fillers, such as zeolites and activated carbon, can improve the separation by pervaporation. Applications of adsorbent-filled membranes in pervaporation have been demonstrated by a number of studies. These applications include removal of organic co...

  7. Examining Adsorbed Polymer Conformations with Fluorescence Imaging

    NASA Astrophysics Data System (ADS)

    Parkes, Maria; Chennaoui, Mourad; Wong, Janet; Tribology Group, Dept. of Mechanical Engineering Team

    2011-03-01

    The conformation of adsorbed polymers can have significant impact on their properties such as dynamics and elasticity as well as their ability to take part in reactions with other molecules. Experimental research to determine adsorbed polymer conformation has relied mainly on atomic force microscopy (AFM) studies. During an AFM scan, the contact between the scanning probe and the polymer could affect the polymer conformation, particularly where parts of the polymer might have formed projected loops and tails. In this work, conformations of model polymers are examined with total internal reflection fluorescence microscopy (TIRFM). The advantage of TIRFM over AFM is that TIRFM is a non contact technique. Lambda DNA labelled along its length with fluorescent probes was adsorbed in a projected 2D -- 3D state. With TIRFM, the relationship between intensity and depth was used as a basis to determine how the conformation of the adsorbed polymers evolved with time using our custom algorithm.

  8. Novel adsorbent applicability for decontamination of printing wastewater

    NASA Astrophysics Data System (ADS)

    Kiurski, Jelena; Oros, Ivana; Ranogajec, Jonjaua; Kecic, Vesna

    2013-04-01

    Adsorption capacity of clayey minerals can be enhanced by replacing the natural exchangeable cations with organic cations, which makes the clay surface more hydrophobic. Different solids such as activated carbon, clay minerals, zeolites, metal oxides and organic polymers have been tested as effective adsorbents. On a global scale, clays have a large applicability for decontamination, purification of urban and industrial residual waters, protection of waste disposal areas, and purification of industrial gases and so on. Clay derivative materials with high adsorption capacities are very attractive from an economical point of view. Due to the economic constraints, a development of cost effective and clean processes is desired. Adsorption processes has proved to be the most effective, especially for effluents with moderate and low heavy metal concentrations, as like as in printing wastewaters. Among several removal technologies, the adsorption of Zn(II) ion onto NZ, B, pure C and C with PEG 600 addition could be of great importance for the printing wastewaters purification. However, the newly designed adsorbent of the defined pore size distribution and phase structure considered as the most suitable material for Zn(II) ion removal. The values of distribution coefficient (Kd) increased with decreasing of the adsorbent amount. The Kd values depend also on the type of used adsorbent, the following increased order is obtained: NZ < B = pure C < C with PEG 600 addition. The adsorption equilibrium data of Zn(II) ion on NZ, B, pure C and C with PEG 600 were analyzed in terms of the Freundlich, Langmuir and Dubinin-Kaganer-Radushkevich (DKR) isotherm models. The characteristic parameters for each isotherms and related correlation coefficients were determined. The values of correlation coefficient (R2) indicated the following order of the isotherm models: Freundlich > Langmuir > DKR. The study also showed that the fired clay modified with PEG 600 addition has great potential

  9. Hybrid inorganic-organic adsorbents Part 1: Synthesis and characterization of mesoporous zirconium titanate frameworks containing coordinating organic functionalities.

    PubMed

    Griffith, Christopher S; De Los Reyes, Massey; Scales, Nicholas; Hanna, John V; Luca, Vittorio

    2010-12-01

    A series of functional hybrid inorganic-organic adsorbent materials have been prepared through postsynthetic grafting of mesoporous zirconium titanate xerogel powders using a range of synthesized and commercial mono-, bis-, and tris-phosphonic acids, many of which have never before been investigated for the preparation of hybrid phases. The hybrid materials have been characterized using thermogravimetric analysis, diffuse reflectance infrared (DRIFT) and 31P MAS NMR spectroscopic techniques and their adsorption properties studied using a 153Gd radiotracer. The highest level of surface functionalization (molecules/nm2) was observed for methylphosphonic acid (∼3 molecules/nm2). The level of functionalization decreased with an increase in the number of potential surface coordinating groups of the phosphonic acids. Spectral decomposition of the DRIFT and 31P MAS NMR spectra showed that each of the phosphonic acid molecules coordinated strongly to the metal oxide surface but that for the 1,1-bis-phosphonic acids and tris-phosphonic acids the coordination was highly variable resulting in a proportion of free or loosely coordinated phosphonic acid groups. Functionalization of a porous mixed metal oxide framework with the tris-methylenephosphonic acid (ATMP-ZrTi-0.33) resulted in a hybrid with the highest affinity for 153Gd3+ in nitric acid solutions across a wide range of acid concentrations. The ATMP-ZrTi-0.33 hybrid material extracted 153Gd3+ with a Kd value of 1×10(4) in 0.01 M HNO3 far exceeding that of the other hybrid phases. The unfunctionalized mesoporous mixed metal oxide had negligible affinity for Gd3+ (Kd<100) under identical experimental conditions. It has been shown that the presence of free or loosely coordinated phosphonic acid groups does not necessarily translate to affinity for 153Gd3+. The theoretical cation exchange capacity of the ATMP-ZrTi-0.33 hybrid phase for Gd3+ has been determined to be about 0.005 mmol/g in 0.01 M HNO3. This behavior and

  10. Regenerable activated bauxite adsorbent alkali monitor probe

    DOEpatents

    Lee, Sheldon H. D.

    1992-01-01

    A regenerable activated bauxite adsorber alkali monitor probe for field applications to provide reliable measurement of alkali-vapor concentration in combustion gas with special emphasis on pressurized fluidized-bed combustion (PFBC) off-gas. More particularly, the invention relates to the development of a easily regenerable bauxite adsorbent for use in a method to accurately determine the alkali-vapor content of PFBC exhaust gases.

  11. Hydrophobic Porous Material Adsorbs Small Organic Molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Hickey, Gregory S.

    1994-01-01

    Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

  12. Mesoporous Silica: A Suitable Adsorbent for Amines

    PubMed Central

    2009-01-01

    Mesoporous silica with KIT-6 structure was investigated as a preconcentrating material in chromatographic systems for ammonia and trimethylamine. Its adsorption capacity was compared to that of existing commercial materials, showing its increased adsorption power. In addition, KIT-6 mesoporous silica efficiently adsorbs both gases, while none of the employed commercial adsorbents did. This means that KIT-6 Mesoporous silica may be a good choice for integrated chromatography/gas sensing micro-devices. PMID:20628459

  13. Regenerable activated bauxite adsorbent alkali monitor probe

    DOEpatents

    Lee, S.H.D.

    1992-12-22

    A regenerable activated bauxite adsorber alkali monitor probe for field applications to provide reliable measurement of alkali-vapor concentration in combustion gas with special emphasis on pressurized fluidized-bed combustion (PFBC) off-gas. More particularly, the invention relates to the development of a easily regenerable bauxite adsorbent for use in a method to accurately determine the alkali-vapor content of PFBC exhaust gases. 6 figs.

  14. NMR studies of metallic tin confined within porous matrices

    SciTech Connect

    Charnaya, E. V.; Tien, Cheng; Lee, M. K.; Kumzerov, Yu. A.

    2007-04-01

    {sup 119}Sn NMR studies were carried out for metallic tin confined within synthetic opal and porous glass. Tin was embedded into nanoporous matrices in the melted state under pressure. The Knight shift for liquid confined tin was found to decrease with decreasing pore size. Correlations between NMR line shapes, Knight shift, and pore filling were observed. The melting and freezing phase transitions of tin under confinement were studied through temperature dependences of NMR signals upon warming and cooling. Melting of tin within the opal matrix agreed well with the liquid skin model suggested for small isolated particles. The influence of the pore filling on the melting process was shown.

  15. Analysis of experimentally shocked minerals by NMR spectroscopy

    SciTech Connect

    Cygan, R.T.; Boslough, M.B.

    1994-10-01

    The shock-loading of natural materials by an impact or explosion can result in the formation of modified and altered phases. In order to characterize the resulting material and to evaluate the extent of shock modification, the authors have used nuclear magnetic resonance (NMR) spectroscopy to examine several experimentally shocked minerals. In three related NMR studies, they have (1) examined shocked clinoptilolite, (2) performed a preliminary analysis of shocked quartz, and (3) reproduced shocked quartz results with detailed spectral deconvolutions, and extended it with NMR analysis of shocked feldspar powders.

  16. Multiple-quantum NMR in solids

    NASA Astrophysics Data System (ADS)

    Yen, Yu-Sze; Pines, A.

    1983-03-01

    Multiple-quantum NMR has typically been observed in small groups of spins in isolated molecules. Due to the profusion of spin transitions in a solid, individual lines are unresolved. Excitation of high quantum transitions by normal schemes is thus difficult. To ensure that overlapping lines add constructively and to enhance sensitivity, time-reversal pulse sequences are used to generate all lines in phase. Up to 22-quantum 1H absorption in solid adamantane is observed.

  17. Multiple-quantum NMR in solids

    SciTech Connect

    Yen, Y.; Pines, A.

    1983-03-15

    Multiple-quantum NMR has typically been observed in small groups of spins in isolated molecules. Due to the profusion of spin transitions in a solid, individual lines are unresolved. Excitation of high quantum transitions by normal schemes is thus difficult. To ensure that overlapping lines add constructively and to enhance sensitivity, time-reversal pulse sequences are used to generate all lines in phase. Up to 22-quantum /sup 1/H absorption in solid adamantane is observed.

  18. Thiophilic adsorbents for RIA and ELISA procedures.

    PubMed

    Oscarsson, S; Chaga, G; Porath, J

    1991-10-25

    Three types of agarose derivatives have been prepared and investigated as adsorbents for radioimmunoassay and ELISA analysis. The analytical systems were evaluated using beta 2 microglobulin as a model. After a competitive reaction between the immunocomponents in solution, the formed immune complexes were adsorbed onto the adsorbent in the presence of 0.5 M potassium sulfate in 0.1 M Tris, pH 7.5. The binding constant between the interaction site on human IgG and the adsorbent 3-(2-pyridylthio)-2-hydroxypropylagarose (Py-S-gel) was determined to be 1.5 x 10(7) M-1 and the binding capacity was 20 mg/ml gel. The immune complex was desorbed by deleting potassium sulfate from the buffer, and only 0.5% of the total applied protein remained after washing the adsorbent with 0.5 M NaOH. The same adsorbent can be used repetitively with different systems. PMID:1940385

  19. Laundering and Deinking Applications of 1H NMR Imaging

    NASA Astrophysics Data System (ADS)

    Tutunjian, P. N.; Borchardt, J. K.; Prieto, N. E.; Raney, K. H.; Ferris, J. A.

    One-dimensional 1H NMR imaging techniques are used to visualize oil removal from fabrics and paper fibers immersed in aqueous solutions of nonionic detergents. The method provides a unique approach to the study of oil-removal kinetics in nonionic detergent systems where traditional optical techniques fail due to solution turbidity. The only requirement of the NMR experiment is the use of deuterated water in order to selectively image the hydrocarbon phase. Preliminary applications to laundering and paper deinking are discussed.

  20. Removal of radioactive iodine from water using Ag2O grafted titanate nanolamina as efficient adsorbent.

    PubMed

    Bo, Arixin; Sarina, Sarina; Zheng, Zhanfeng; Yang, Dongjiang; Liu, Hongwei; Zhu, Huaiyong

    2013-02-15

    Emergency treatment of radioactive material leakage and safety disposal of nuclear waste is a constant concern all along with the development of radioactive materials applications. To provide a solution, titanate with large surface area (143 m(2)g(-1)) and a lamina morphology (the thickness of the lamina is in range of tens of nanometers) was prepared from inorganic titanium compounds by hydrothermal reactions at 433 K. Ag(2)O nanocrystals (5-30 nm) were deposited onto the titanate lamina. The surface of the titanate lamina has crystallographic similarity to that of Ag(2)O nanocrystals. Hence, the deposited Ag(2)O nanocrystals and titanate substrate join together at these surfaces, forming a well-matched phase coherent interface between them. Such coherence between the two phases reduces the overall energy by minimizing surface energy and anchors the Ag(2)O nanocrystals firmly on the external surface of the titanate structure. The composite thus obtained was applied as efficient adsorbent to remove radioactive iodine from water (one gram adsorbent can capture up to 3.4 mmol of I(-) anions). The composite adsorbent can be recovered easily for safe disposal. The structure changes of the titanate lamina and the composite adsorbent were monitored by various techniques. The isotherm and kinetics of iodine adsorption, competitive adsorption and column adsorption using the adsorbent were studied to assess its iodine removal abilities. The adsorbent exhibited a capacity as high as 3.4 mmol of iodine per gram of adsorbent in 1h. Therefore, Ag(2)O deposited titanate lamina is an effective adsorbent for removing radioactive iodine from water. PMID:23313892

  1. 224} studied by NMR

    SciTech Connect

    Furukawa, Y; Fang, X; Kögerler, P

    2014-05-14

    7Li nuclear magnetic resonance (NMR) studies have been performed to investigate magnetic properties and spin dynamics of Mn3+ (S = 2) spins in the giant polyoxometalate molecule {Mn40W224}. The 7Li-NMR line width is proportional to the external magnetic field H as expected in a paramagnetic state above 3 K. Below this temperature the line width shows a sudden increase and is almost independent of H, which indicates freezing of the local Mn3+ spins. The temperature dependence of T1 for both 1H and 7Li reveals slow spin dynamics at low temperatures, consistent with spin freezing. The slow spin dynamics is also evidenced by the observation of a peak of 1/T2 around 3 K, where the fluctuation frequency of spins is of the order of ~200 kHz. An explicit form of the temperature dependence of the fluctuation frequency of Mn3+ spins is derived from the nuclear relaxation data.

  2. Double rotation NMR studies of zeolites and aluminophosphate molecular sieves

    SciTech Connect

    Jelinek, R. |

    1993-07-01

    Goal is to study the organization and structures of guest atoms and molecules and their reactions on internal surfaces within pores of zeolites and aluminophosphate molecular sieves. {sup 27}Al and {sup 23}Na double rotation NMR (DOR) is used since it removes the anisotropic broadening in NMR spectra of quadrupolar nuclei, thus increasing resolution. This work concentrates on probing aluminum framework atoms in aluminophosphate molecular sieves and sodium extra framework cations in porous aluminosilicates. In aluminophosphates, ordering and electronic environments of the framework {sup 27}Al nuclei are modified upon adsorption of water molecules within the channels; a relation is sought between the sieve channel topology and the organization of adsorbed water, as well as the interaction between the Al nuclei and the water molecules. Extra framework Na{sup +} cations are directly involved in adsorption processes and reactions in zeolite cavities.

  3. NMR imaging of materials

    SciTech Connect

    Vinegar, H.J.; Rothwell, W.P.

    1988-03-01

    A method for obtaining at least one petrophysical property of a porous material containing therein at least one preselected fluid, is described, comprising: NMR imaging the material to generate signals dependent upon both M(0) and T/sub 1/ and M(0) and T/sub 2/, generating separate M(0), T/sub 1/ and T/sub 2/ images from the signals, and determining at least one petrophysical property from at least one of the images.

  4. NMR Studies of Peroxidases.

    NASA Astrophysics Data System (ADS)

    Veitch, Nigel Charles

    Available from UMI in association with The British Library. Requires signed TDF. Peroxidases are a haem-containing group of enzymes with a wide diversity of function within biological systems. While a common characteristic is the ability to catalyse the conversion of hydrogen peroxide to water, it is the accompanying processes of hormone synthesis and degradation which have generated such a high level of interest. However, information at the molecular level is limited to a single well-resolved crystal structure, that of yeast cytochrome c peroxidase. This thesis presents a strategy for the investigation of peroxidase structure and function based on proton nuclear magnetic resonance spectroscopy, a technique which has the ability to address aspects of both protein structure and protein dynamics in solution. The application of one- and two-dimensional NMR techniques has been developed in the context of plant peroxidases, notably the isoenzyme HRP-C derived from the horseradish root. Characterisation of the proton NMR spectra of HRP -C in resting and ligated states provided new information enabling the structure of the binding site for aromatic donor molecules, such as indole-3-propionic, ferulic and benzhydroxamic acids, to be resolved. In order to overcome difficulties encountered with a protein of the complexity of peroxidase, additional information was obtained from chemical shift parameters and the use of peroxidase variants produced by site-directed mutagenesis. A comparative study using NMR spectroscopy was undertaken for wild-type recombinant HRP-C expressed in Escherichia coli, and two protein variants with substitutions made to residues located on the distal side of the haem pocket, Phe41 to Val and Arg38 to Lys. NMR analyses of a plant peroxidase from barley grains and the fungal peroxidase from Coprinus cinereus were also successful using methods conceived with HRP-C. Examination of three specifically constructed recombinant protein variants of C. cinereus

  5. Titanate-based adsorbents for radioactive ions entrapment from water.

    PubMed

    Yang, Dongjiang; Liu, Hongwei; Zheng, Zhanfeng; Sarina, Sarina; Zhu, Huaiyong

    2013-03-21

    This feature article reviews some titanate-based adsorbents for the removal of radioactive wastes (cations and anions) from water. At the beginning, we discuss the development of the conventional ion-exchangeable titanate powders for the entrapment of radioactive cations, such as crystalline silicotitanate (CST), monosodium titanate (MST), peroxotitanate (PT). Then, we specially emphasize the recent progress in the uptake of radioactive ions by one-dimensional (1D) sodium titanate nanofibers and nanotubes, which includes the synthesis and phase transformation of the 1D nanomaterials, adsorption ability (capacity, selectivity, kinetics, etc.) of radioactive cations and anions, and the structural evolution during the adsorption process. PMID:23412572

  6. Mobilization of arsenite by dissimilatory reduction of adsorbed arsenate

    USGS Publications Warehouse

    Zobrist, J.; Dowdle, P.R.; Davis, J.A.; Oremland, R.S.

    2000-01-01

    Sulfurospirillum barnesii is capable of anaerobic growth using ferric iron or arsenate as electron acceptors. Cell suspensions of S. barnesii were able to reduce arsenate to arsenite when the former oxyanion was dissolved in solution, or when it was adsorbed onto the surface of ferrihydrite, a common soil mineral, by a variety of mechanisms (e.g., coprecipitation, presorption). Reduction of Fe(III) in ferrihydrite to soluble Fe(II) also occurred, but dissolution of ferrihydrite was not required in order for adsorbed arsenate reduction to be achieved. This was illustrated by bacterial reduction of arsenate coprecipitated with aluminum hydroxide, a mineral that does not undergo reductive dissolution. The rate of arsenate reduction was influenced by the method in which arsenate became associated with the mineral phases and may have been strongly coupled with arsenate desorption rates. The extent of release of arsenite into solution was governed by adsorption of arsenite onto the ferrihydrite or alumina phases. The results of these experiments have interpretive significance to the mobilization of arsenic in large alluvial aquifers, such as those of the Ganges in India and Bangladesh, and in the hyporheic zones of contaminated streams.Sulfurospirillum barnesii is capable of anaerobic growth using ferric iron or arsenate as electron acceptors. Cell suspensions of S. barnesii were able to reduce arsenate to arsenite when the former oxyanion was dissolved in solution, or when it was adsorbed onto the surface of ferrihydrite a common soil mineral, by a variety of mechanisms (e.g., coprecipitation, presorption). Reduction of Fe(III) in ferrihydrite to soluble Fe(II) also occurred, but dissolution of ferrihydrite was not required in order for adsorbed arsenate reduction to be achieved. This was illustrated by bacterial reduction of arsenate coprecipitated with aluminum hydroxide, a mineral that does not undergo reductive dissolution. The rate of arsenate reduction was

  7. Contaminant removal from enclosed atmospheres by regenerable adsorbents

    NASA Technical Reports Server (NTRS)

    Goldsmith, R. L.; Mcnulty, K. J.; Freedland, G. M.; Turk, A.; Nwankwo, J.

    1974-01-01

    A system for removing contaminants from spacecraft atmospheres was studied, which utilizes catalyst-impregnated activated carbon followed by in-situ regeneration by low-temperature catalytic oxidation of the adsorbed contaminants. Platinum was deposited on activated carbon by liquid phase impregnation with chloroplatinic acid, followed by drying and high-temperature reduction. Results were obtained for the seven selected spacecraft contaminants by means of three experimental test systems. The results indicate that the contaminants could be removed by oxidation with very little loss in adsorptive capacity. The advantages of a catalyst-impregnated carbon for oxidative regeneration are found to be significant enough to warrent its use.

  8. Insight into the adsorption of PPCPs by porous adsorbents: Effect of the properties of adsorbents and adsorbates.

    PubMed

    Zhu, Zengyin; Xie, Jiawen; Zhang, Mancheng; Zhou, Qing; Liu, Fuqiang

    2016-07-01

    Adsorption is an efficient method for removal of pharmaceuticals and personal care products (PPCPs). Magnetic resins are efficient adsorbents for water treatment and exhibit potential for PPCP removal. In this study, the magnetic hypercrosslinked resin Q100 was used for adsorption of PPCPs. The adsorption behavior of this resin was compared with those of two activated carbons, namely, Norit and F400D. Norit exhibited the fastest adsorption kinetics, followed by Q100. Norit featured a honeycomb shape and long-range ordered pore channels, which facilitated the diffusion of PPCPs. Moreover, the large average pore size of Q100 reduced diffusion resistance. The adsorbed amounts of 11 PPCPs on the three adsorbents increased with increasing adsorbate hydrophobicity. For Q100, a significant linear correlation was observed between the adsorption performance for PPCPs and hydrophobicity (logD value) of adsorbates (R(2) = 0.8951); as such, PPCPs with high logD values (>1.69) could be efficiently removed. Compared with those of Norit and F400D, the adsorption performance of Q100 was less affected by humic acid because of the dominant hydrophobic interaction. Furthermore, Q100 showed improved regeneration performance, which renders it promising for PPCP removal in practical applications. PMID:27131811

  9. Determination of 1-naphthol and 2-naphthol from environmental waters by magnetic solid phase extraction with Fe@MgAl-layered double hydroxides nanoparticles as the adsorbents prior to high performance liquid chromatography.

    PubMed

    Zhou, Qingxiang; Lei, Man; Li, Jing; Zhao, Kuifu; Liu, Yongli

    2016-04-01

    Magnetic Fe@MgAl-layered double hydroxides (MgAl-LDHs) composite was firstly synthesized by coating MgAl-layered double hydroxides on the surface of the dispersed nanoscale zero valent irons with co-precipitation method and characterized by transmission electron microscopy and X-ray diffraction techniques. The synthesized Fe@MgAl-LDHs nanoparticles were investigated for magnetic solid phase extraction (MSPE) of 1-naphthol and 2-naphthol from the water samples. The elutent containing 1-naphthol and 2-naphthol was analyzed by high performance liquid chromatography with variable wavelength detection (HPLC-UV). Under optimal conditions, there is good linear relationship between the concentration and the peak area in the range of 0.5-200 μgL(-1) with the correlation coefficients (r(2)) above 0.998 for 1-naphthol and 2-naphthol. The limits of detection were 0.22 μgL(-1) and 0.19 μgL(-1) for 1-naphthol and 2-naphthol, respectively, and precisions were both below 2.5% (n=6). The real water analysis demonstrated that the spiked recoveries were in the range of 79.2-80.9% (n=3). All these results indicated that the developed MSPE-HPLC-UV method was proved to be an efficient tool for the analysis of naphthols. PMID:26965650

  10. Phase Coexistence in a Dynamic Phase Diagram.

    PubMed

    Gentile, Luigi; Coppola, Luigi; Balog, Sandor; Mortensen, Kell; Ranieri, Giuseppe A; Olsson, Ulf

    2015-08-01

    Metastability and phase coexistence are important concepts in colloidal science. Typically, the phase diagram of colloidal systems is considered at the equilibrium without the presence of an external field. However, several studies have reported phase transition under mechanical deformation. The reason behind phase coexistence under shear flow is not fully understood. Here, multilamellar vesicle (MLV)-to-sponge (L3 ) and MLV-to-Lα transitions upon increasing temperature are detected using flow small-angle neutron scattering techniques. Coexistence of Lα and MLV phases at 40 °C under shear flow is detected by using flow NMR spectroscopy. The unusual rheological behavior observed by studying the lamellar phase of a non-ionic surfactant is explained using (2) H NMR and diffusion flow NMR spectroscopy with the coexistence of planar lamellar-multilamellar vesicles. Moreover, a dynamic phase diagram over a wide range of temperatures is proposed. PMID:26083451

  11. Supported polytertiary amines: highly efficient and selective SO2 adsorbents.

    PubMed

    Tailor, Ritesh; Abboud, Mohamed; Sayari, Abdelhamid

    2014-01-01

    Tertiary amine containing poly(propyleneimine) second (G2) and third (G3) generation dendrimers as well as polyethyleneimine (PEI) were developed for the selective removal of SO2. N-Alkylation of primary and secondary amines into tertiary amines was confirmed by FTIR and NMR analysis. Such modified polyamines were impregnated on two nanoporous supports, namely, SBA-15PL silica with platelet morphology and ethanol-extracted pore-expanded MCM-41 (PME) composite. In the presence of 0.1% SO2/N2 at 23 °C, the uptake of modified PEI, G2, and G3 supported on SBA-15PL was 2.07, 2.35, and 1.71 mmol/g, respectively; corresponding to SO2/N ratios of 0.22, 0.4, and 0.3. Under the same conditions, the SO2 adsorption capacity of PME-supported modified PEI and G3 was significantly higher, reaching 4.68 and 4.34 mmol/g, corresponding to SO2/N ratios of 0.41 and 0.82, respectively. The working SO2 adsorption capacity decreased with increasing temperature, reflecting the exothermic nature of the process. The adsorption capacity of these materials was enhanced dramatically in the presence of humidity in the gas mixture. FTIR data before SO2 adsorption and after adsorption and regeneration did not indicate any change in the materials. Nonetheless, the SO2 working capacity decreased in consecutive adsorption/regeneration cycles due to evaporation of impregnated polyamines, rather than actual deactivation. FTIR and (13)C and (15)N CP-MAS NMR of fresh and SO2 adsorbed modified G3 on PME confirmed the formation of a complexation adduct. PMID:24437448

  12. Multiwalled carbon nanotubes as a solid-phase extraction adsorbent for the determination of three barbiturates in pork by ion trap gas chromatography-tandem mass spectrometry (GC/MS/MS) following microwave assisted derivatization.

    PubMed

    Zhao, Haixiang; Wang, Liping; Qiu, Yueming; Zhou, Zhiqiang; Zhong, Weike; Li, Xiang

    2007-03-14

    A new method was developed for the rapid screening and confirmation analysis of barbital, amobarbital and phenobarbital residues in pork by gas chromatography-tandem mass spectrometry (GC/MS/MS) with ion trap MSD. The residual barbiturates in pork were extracted by ultrasonic extraction, cleaned up on a multiwalled carbon nanotubes (MWCNTs) packed solid phase extraction (SPE) cartridge and applied acetone-ethyl acetate (3:7, v/v) mixture as eluting solvent and derivatized with CH3I under microwave irradiation. The methylated barbiturates were separated on a TR-5MS capillary column and detected with an ion trap mass detector. Electron impact ion source (EI) operating MS/MS mode was adopted for identification and external standard method was employed for quantification. One precursor ion m/z 169 was selected for analysis of barbital and amobarbital and m/z 232 was selected for phenobarbital. The product ions were obtained under 1.0 V excitation voltage. Good linearities (linear coefficient R > 0.99) were obtained at the range of 0.5-50 microg kg(-1). Limit of detection (LOD) of barbital was 0.2 microg kg(-1) and that of amobarbital and phenobarbital were both 0.1 microg kg(-1) (S/N > or = 3). Limit of quantification (LOQ) was 0.5 microg kg(-1) for three barbiturates (S/N > or = 10). Satisfying recoveries ranging from 75% to 96% of the three barbiturates spiked in pork were obtained, with relative standard deviations (R.S.D.) in the range of 2.1-7.8%. PMID:17386740

  13. Bayesian reconstruction of projection reconstruction NMR (PR-NMR).

    PubMed

    Yoon, Ji Won

    2014-11-01

    Projection reconstruction nuclear magnetic resonance (PR-NMR) is a technique for generating multidimensional NMR spectra. A small number of projections from lower-dimensional NMR spectra are used to reconstruct the multidimensional NMR spectra. In our previous work, it was shown that multidimensional NMR spectra are efficiently reconstructed using peak-by-peak based reversible jump Markov chain Monte Carlo (RJMCMC) algorithm. We propose an extended and generalized RJMCMC algorithm replacing a simple linear model with a linear mixed model to reconstruct close NMR spectra into true spectra. This statistical method generates samples in a Bayesian scheme. Our proposed algorithm is tested on a set of six projections derived from the three-dimensional 700 MHz HNCO spectrum of a protein HasA. PMID:25218584

  14. Soils, Pores, and NMR

    NASA Astrophysics Data System (ADS)

    Pohlmeier, Andreas; Haber-Pohlmeier, Sabina; Haber, Agnes; Sucre, Oscar; Stingaciu, Laura; Stapf, Siegfried; Blümich, Bernhard

    2010-05-01

    Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 < 5 ms. Moreover, the dependence of the relaxation rate on magnetic field strength allows the identification of 2D diffusion at the interfaces as the mechanism which governs the relaxation process (Pohlmeier et al. 2009). T2 relaxation curves are frequently measured for the rapid characterization of soils by means of the CPMG echo train. Basically, they contain the same information about the pore systems like T1 curves, since mostly the overall relaxation is dominated by surface relaxivity and the surface/volume ratio of the pores. However, one must be aware that T2 relaxation is additionally affected by diffusion in internal gradients, and this can be overcome by using sufficiently short echo times and low magnetic fields (Stingaciu et al. 2009). Second, the logic continuation of conventional relaxation measurements is the 2-dimensional experiment, where prior to the final detection of the CPMG echo train an encoding period is applied. This can be T1-encoding by an inversion pulse, or T2 encoding by a sequence of 90 and 180° pulses. During the following evolution time the separately encoded signals can mix and this reveals information about

  15. NMR solution structure of butantoxin.

    PubMed

    Holaday, S K; Martin, B M; Fletcher, P L; Krishna, N R

    2000-07-01

    The NMR structure of a new toxin, butantoxin (BuTX), which is present in the venoms of the three Brazilian scorpions Tityus serrulatus, Tityus bahiensis, and Tityus stigmurus, has been investigated. This toxin was shown to reversibly block the Shaker B potassium channels (K(d) approximately 660 nM) and inhibit the proliferation of T-cells and the interleukin-2 production of antigen-stimulated T-helper cells. BuTX is a 40 amino acid basic protein stabilized by the four disulfide bridges: Cys2-Cys5, Cys10-Cys31, Cys16-Cys36, and Cys20-Cys38. The latter three are conserved among all members of the short-chain scorpion toxin family, while the first is unique to BuTX. The three-dimensional structure of BuTX was determined using (1)H-NMR spectroscopy. NOESY, phase sensitive COSY (PH-COSY), and amide hydrogen exchange data were used to generate constraints for molecular modeling calculations. Distance geometry and simulated annealing calculations were performed to generate a family of 49 structures free of constraint violations. The secondary structure of BuTX consists of a short 2(1/2) turn alpha-helix (Glu15-Phe23) and a beta-sheet. The beta-sheet is composed of two well-defined antiparallel strands (Gly29-Met32 and Lys35-Cys38) connected by a type-I' beta-turn (Asn33-Asn34). Residues Cys5-Ala9 form a quasi-third strand of the beta-sheet. The N-terminal C2-C5 disulfide bridge unique to this toxin does not appear to confer stability to the protein. PMID:10864437

  16. Correlation between the Sorption-Induced Deformation of Nanoporous Glass and the Continuous Freezing of Adsorbed Argon.

    PubMed

    Schappert, Klaus; Reiplinger, Nicolas; Pelster, Rolf

    2016-08-01

    In this article we study the dependence of the sorption-induced deformation of nanoporous glass on the liquid-solid phase transition of adsorbed argon. During cooling we observe a continuous reduction of the expansion of the porous glass matrix caused by the adsorbate. The contraction is attended by a likewise continuous change of the adsorbed argon's phase state from liquid to solid. This simultaneous behavior evidences that the liquid-solid phase transition leads to a reduction of the pressure the adsorbate exerts on the pore walls. Furthermore, the study shows that small temperature changes can temporarily cause strong deformations of the porous material that decay in long time intervals of up to 1 week. We expect that our observations for the model system of argon and porous glass can be generalized to other systems. Consequently, this study will have implications when considering porous materials for applications, e.g., as a medium for storage. PMID:27398774

  17. Fringe field NMR diffusometry of anomalous self-diffusion in molecular sieves

    NASA Astrophysics Data System (ADS)

    Ylihautala, Mika; Jokisaari, Jukka; Fischer, Elmar; Kimmich, Rainer

    1998-06-01

    Superconducting magnet fringe field NMR diffusometry is applied to an adsorbate-molecular sieve system in order to obtain intracrystalline self-diffusion of adsorbed molecules. Effects of self-diffusion, exchange, relaxation, and dipolar correlation are discussed. The proper equations for one- and two-dimensional anomalous self-diffusion with and without macroscopic order are derived. The method is applied to investigate methane self-diffusion in the molecular sieve silicoaluminophosphate, type 11 (SAPO-11). It is concluded that the nature of the methane displacements in the sieve channels is single-file self-diffusion.

  18. Black Molecular Adsorber Coatings for Spaceflight Applications

    NASA Technical Reports Server (NTRS)

    Abraham, Nithin Susan; Hasegawa, Mark Makoto; Straka, Sharon A.

    2014-01-01

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

  19. Size selective hydrophobic adsorbent for organic molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Hickey, Gregory S. (Inventor)

    1997-01-01

    The present invention relates to an adsorbent formed by the pyrolysis of a hydrophobic silica with a pore size greater than 5 .ANG., such as SILICALITE.TM., with a molecular sieving polymer precursor such as polyfurfuryl alcohol, polyacrylonitrile, polyvinylidene chloride, phenol-formaldehyde resin, polyvinylidene difluoride and mixtures thereof. Polyfurfuryl alcohol is the most preferred. The adsorbent produced by the pyrolysis has a silicon to carbon mole ratio of between about 10:1 and 1:3, and preferably about 2:1 to 1:2, most preferably 1:1. The pyrolysis is performed as a ramped temperature program between about 100.degree. and 800.degree. C., and preferably between about 100.degree. and 600.degree. C. The present invention also relates to a method for selectively adsorbing organic molecules having a molecular size (mean molecular diameter) of between about 3 and 6 .ANG. comprising contacting a vapor containing the small organic molecules to be adsorbed with the adsorbent composition of the present invention.

  20. The use of dielectric and NMR measurements to determine the pore-scale location of organic. 1998 annual progress report

    SciTech Connect

    Knight, R.

    1998-06-01

    'The objective of the three-year research project is to investigate the effect of adsorbed organics on the dielectric and nuclear magnetic resonance (NMR) response of porous geological materials. This will allow the author to assess the use of dielectric and NMR measurements at a site to determine whether organic contaminants are present in the central volume of the pore space or are adsorbed to the solid surfaces. In addition, she proposes to use laboratory dielectric and NMR measurements to study the kinetics of the adsorption and desorption of organics. This report summarizes work completed after 20 months of a three-year project. The research involves the study of the NMR and dielectric behavior of sands with three types of solid surfaces: water-wet, where water spontaneously coats and adsorbs to the solid surfaces; hydrophobic, where water is repelled from the solid surfaces by an organosilane coating; and oil-wet, where oil coats the solid surfaces. The oil-wet case is representative of a contaminated soil, in which oil has become adsorbed to the solid surfaces.'

  1. The use of dielectric and NMR measurements to determine the pore-scale location of organic contaminants. 1997 annual progress report

    SciTech Connect

    Knight, R.; Bryar, T.; Caputi, M.

    1997-07-15

    'The objective of the three-year research project is to investigate the effect of adsorbed organics on the dielectric and nuclear magnetic resonance (NMR) response of porous geological materials. This will allow us to assess the use of dielectric and NMR measurements at a site to determine whether organic contaminants are present in the central volume of the pore space (in a water-wet system) or are adsorbed to the solid surface. In addition, the authors propose to use laboratory dielectric and NMR measurements to study the kinetics of the adsorption and desorption of organics by conducting experiments where the authors control temperature and vary fluid chemistry. This project can be divided into three parts: sample preparation, NMR studies, dielectric studies. Over the past nine months the authors have made significant progress in sample preparation and NMR studies. As the plan is to conduct the NMR and dielectric measurements on the same set of samples, the authors delayed the start of the dielectric measurements until the first stage of NMR measurements were complete. Below the authors summarize the progress in sample preparation and NMR measurements, first briefly introducing the method used for the NMR measurements.'

  2. Method for modifying trigger level for adsorber regeneration

    DOEpatents

    Ruth, Michael J.; Cunningham, Michael J.

    2010-05-25

    A method for modifying a NO.sub.x adsorber regeneration triggering variable. Engine operating conditions are monitored until the regeneration triggering variable is met. The adsorber is regenerated and the adsorbtion efficiency of the adsorber is subsequently determined. The regeneration triggering variable is modified to correspond with the decline in adsorber efficiency. The adsorber efficiency may be determined using an empirically predetermined set of values or by using a pair of oxygen sensors to determine the oxygen response delay across the sensors.

  3. Discrete analysis of stochastic NMR.II

    NASA Astrophysics Data System (ADS)

    Wong, S. T. S.; Rods, M. S.; Newmark, R. D.; Budinger, T. F.

    Stochastic NMR is an efficient technique for high-field in vivo imaging and spectroscopic studies where the peak RF power required may be prohibitively high for conventional pulsed NMR techniques. A stochastic NMR experiment excites the spin system with a sequence of RF pulses where the flip angles or the phases of the pulses are samples of a discrete stochastic process. In a previous paper the stochastic experiment was analyzed and analytic expressions for the input-output cross-correlations, average signal power, and signal spectral density were obtained for a general stochastic RF excitation. In this paper specific cases of excitation with random phase, fixed flip angle, and excitation with two random components in quadrature are analyzed. The input-output cross-correlation for these two types of excitations is shown to be Lorentzian. Line broadening is the only spectral distortion as the RF excitation power is increased. The systematic noise power is inversely proportional to the number of data points N used in the spectral reconstruction. The use of a complete maximum length sequence (MLS) may improve the signal-to-systematic-noise ratio by 20 dB relative to random binary excitation, but peculiar features in the higher-order autocorrelations of MLS cause noise-like distortion in the reconstructed spectra when the excitation power is high. The amount of noise-like distortion depends on the choice of the MLS generator.

  4. Infrared study on the adsorbed state of ammonia on heteropoly compounds

    SciTech Connect

    Seo, Gon; Lim, Jeong-Woo ); Kim, Jong-Taik )

    1988-12-01

    A heteropoly compound is one of the strongly active acid catalysts which can be used for several acid catalyzed reaction. One property of heteropoly compounds as a solid acid catalyst is that there are acid sites on the surface as well as in the bulk. The other property of these catalysts is that nitrogen compounds such as pyridine and ammonia are easily adsorbed as a pseudo-liquid phase in the bulk. Kim et al. reported that there was no correlation between the adsorbed amounts of pyridine and those of ammonia on heteropoly compounds. They suggested that ammonia could be adsorbed on an acid site of a heteropoly compound as well as on a metal cation. The adsorption of ammonia as an amine structure on copper containing heteropoly compound was discussed by Saito et al. However, a systematic study on the adsorbed state of ammonia on the heteropoly compound was not reported. This paper reports an investigation of the infrared spectra of ammonia adsorbed on a heteropoly compound to illustrate the possible states of the adsorbed ammonia.

  5. Photoexcitation of adsorbates on metal surfaces: One-step or three-step

    SciTech Connect

    Petek, Hrvoje

    2012-09-07

    In this essay we discuss the light-matter interactions at molecule-covered metal surfaces that initiate surface photochemistry. The hot-electron mechanism for surface photochemistry, whereby the absorption of light by a metal surface creates an electron-hole pair, and the hot electron scatters through an unoccupied resonance of adsorbate to initiate nuclear dynamics leading to photochemistry, has become widely accepted. Yet, ultrafast spectroscopic measurements of molecule-surface electronic structure and photoexcitation dynamics provide scant support for the hot electron mechanism. Instead, in most cases the adsorbate resonances are excited through photoinduced substrate-to-adsorbate charge transfer. Based on recent studies of the role of coherence in adsorbate photoexcitation, as measured by the optical phase and momentum resolved two-photon photoemission measurements, we examine critically the hot electron mechanism, and propose an alternative description based on direct charge transfer of electrons from the substrate to adsorbate. The advantage of this more quantum mechanically rigorous description is that it informs how material properties of the substrate and adsorbate, as well as their interaction, influence the frequency dependent probability of photoexcitation and ultimately how light can be used to probe and control surface femtochemistry.

  6. Dimensionally Frustrated Diffusion towards Fractal Adsorbers

    NASA Astrophysics Data System (ADS)

    Nair, Pradeep R.; Alam, Muhammad A.

    2007-12-01

    Diffusion towards a fractal adsorber is a well-researched problem with many applications. While the steady-state flux towards such adsorbers is known to be characterized by the fractal dimension (DF) of the surface, the more general problem of time-dependent adsorption kinetics of fractal surfaces remains poorly understood. In this Letter, we show that the time-dependent flux to fractal adsorbers (1

  7. Standoff Spectroscopy of Surface Adsorbed Chemicals

    SciTech Connect

    Van Neste, Charles W; Senesac, Larry R; Thundat, Thomas George

    2009-01-01

    Despite its immediate applications, selective detection of trace quantities of surface adsorbed chemicals, such as explosives, without physically collecting the sample molecules is a challenging task. Standoff spectroscopic techniques offer an ideal method of detecting chemicals without using a sample collection step. Though standoff spectroscopic techniques are capable of providing high selectivity, their demonstrated sensitivities are poor. Here we describe standoff detection of trace quantities of surface adsorbed chemicals using two quantum cascade lasers operated simultaneously, with tunable wavelength windows that match with absorption peaks of the analytes. This standoff method is a variation of photoacoustic spectroscopy, where scattered light from the sample surface is used for exciting acoustic resonance of the detector. We demonstrate a sensitivity of 100 ng/cm{sup 2} and a standoff detection distance of 20 m for surface adsorbed analytes such as explosives and tributyl phosphate.

  8. Summary of Miniature NMR Development

    SciTech Connect

    Friedman, Gennady; Feinerman, Alan

    2000-12-31

    The effort in this project has been in 3 distinct directions: (1) First, they focused on development of miniature microfabricated micro-coil NMR detectors with maximum Signal-to-Noise (SNR) ratio. (2) Secondly, they focused on design of miniature micro-coil NMR detectors that have minimal effect on the NMR spectrum distortions. (3) Lastly they focused on the development of a permanent magnet capable of generating fields on the order of 1 Tesla with better than 10 ppm uniformity.

  9. NMR with excitation modulated by Frank sequences.

    PubMed

    Blümich, Bernhard; Gong, Qingxia; Byrne, Eimear; Greferath, Marcus

    2009-07-01

    Miniaturized NMR is of growing importance in bio-, chemical, and -material sciences. Other than the magnet, bulky components are the radio-frequency power amplifier and the power supply or battery pack. We show that constant flip-angle excitation with phase modulation following a particular type of polyphase perfect sequences results in low peak excitation power at high response peak power. It has ideal power distribution in both the time domain and the frequency domain. A savings in peak excitation power of six orders of magnitude has been realized compared to conventionally pulsed excitation. Among others, the excitation promises to be of use for button-cell operated miniature NMR devices as well as for complying with specific-absorption-rate regulations in high-field medical imaging. PMID:19386525

  10. Automated sample preparation station for studying self-diffusion in porous solids with NMR spectroscopy

    SciTech Connect

    Hedin, Niklas; DeMartin, Gregory J.; Reyes, Sebastian C.

    2006-03-15

    In studies of gas diffusion in porous solids with nuclear magnetic resonance (NMR) spectroscopy the sample preparation procedure becomes very important. An apparatus is presented here that pretreats the sample ex situ and accurately sets the desired pressure and temperature within the NMR tube prior to its introduction in the spectrometer. The gas manifold that supplies the NMR tube is also connected to a microbalance containing another portion of the same sample, which is kept at the same temperature as the sample in the NMR tube. This arrangement permits the simultaneous measurement of the adsorption loading on the sample, which is required for the interpretation of the NMR diffusion experiments. Furthermore, to ensure a good seal of the NMR tube, a hybrid valve design composed of titanium, a Teflon registered seat, and Kalrez registered O-rings is utilized. A computer controlled algorithm ensures the accuracy and reproducibility of all the procedures, enabling the NMR diffusion experiments to be performed at well controlled conditions of pressure, temperature, and amount of gas adsorbed on the porous sample.

  11. NMR Spectroscopy for Thin Films by Magnetic Resonance Force Microscopy

    PubMed Central

    Won, Soonho; Saun, Seung-Bo; Lee, Soonchil; Lee, SangGap; Kim, Kiwoong; Han, Yunseok

    2013-01-01

    Nuclear magnetic resonance (NMR) is a fundamental research tool that is widely used in many fields. Despite its powerful applications, unfortunately the low sensitivity of conventional NMR makes it difficult to study thin film or nano-sized samples. In this work, we report the first NMR spectrum obtained from general thin films by using magnetic resonance force microscopy (MRFM). To minimize the amount of imaging information inevitably mixed into the signal when a gradient field is used, we adopted a large magnet with a flat end with a diameter of 336 μm that generates a homogeneous field on the sample plane and a field gradient in a direction perpendicular to the plane. Cyclic adiabatic inversion was used in conjunction with periodic phase inversion of the frequency shift to maximize the SNR. In this way, we obtained the 19F NMR spectrum for a 34 nm-thick CaF2 thin film. PMID:24217000

  12. Enhancing uranium uptake by amidoxime adsorbent in seawater: An investigation for optimum alkaline conditioning parameters

    DOE PAGESBeta

    Das, Sadananda; Tsouris, Costas; Zhang, Chenxi; Brown, Suree; Janke, Christopher James; Mayes, Richard T.; Kuo, Li -Jung; Gill, Gary; Dai, Sheng; Kim, J.; et al

    2015-09-07

    A high-surface-area polyethylene-fiber adsorbent (AF160-2) has been developed at the Oak Ridge National Laboratory by radiation-induced graft polymerization of acrylonitrile and itaconic acid. The grafted nitriles were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with potassium hydroxide (KOH) by varying different reaction parameters such as KOH concentration (0.2, 0.44, and 0.6 M), duration (1, 2, and 3 h), and temperature (60, 70, and 80 °C). Adsorbent screening was then performed with simulated seawater solutions containing sodium chloride and sodium bicarbonate, at concentrations found in seawater, and uranium nitrate at a uranium concentration ofmore » ~7–8 ppm and pH 8. Fourier transform infrared spectroscopy and solid-state NMR analyses indicated that a fraction of amidoxime groups was hydrolyzed to carboxylate during KOH conditioning. The uranium adsorption capacity in the simulated seawater screening solution gradually increased with conditioning time and temperature for all KOH concentrations. It was also observed that the adsorption capacity increased with an increase in concentration of KOH for all the conditioning times and temperatures. AF160-2 adsorbent samples were also tested with natural seawater using flow-through experiments to determine uranium adsorption capacity with varying KOH conditioning time and temperature. Based on uranium loading capacity values of several AF160-2 samples, it was observed that changing KOH conditioning time from 3 to 1 h at 60, 70, and 80 °C resulted in an increase of the uranium loading capacity in seawater, which did not follow the trend found in laboratory screening with stimulated solutions. Longer KOH conditioning times lead to significantly higher uptake of divalent metal ions, such as calcium and magnesium, which is a result of amidoxime conversion into less selective carboxylate. The scanning electron microscopy showed that long

  13. Enhancing uranium uptake by amidoxime adsorbent in seawater: An investigation for optimum alkaline conditioning parameters

    SciTech Connect

    Das, Sadananda; Tsouris, Costas; Zhang, Chenxi; Brown, Suree; Janke, Christopher James; Mayes, Richard T.; Kuo, Li -Jung; Gill, Gary; Dai, Sheng; Kim, J.; Oyola, Y.; Wood, J. R.

    2015-09-07

    A high-surface-area polyethylene-fiber adsorbent (AF160-2) has been developed at the Oak Ridge National Laboratory by radiation-induced graft polymerization of acrylonitrile and itaconic acid. The grafted nitriles were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with potassium hydroxide (KOH) by varying different reaction parameters such as KOH concentration (0.2, 0.44, and 0.6 M), duration (1, 2, and 3 h), and temperature (60, 70, and 80 °C). Adsorbent screening was then performed with simulated seawater solutions containing sodium chloride and sodium bicarbonate, at concentrations found in seawater, and uranium nitrate at a uranium concentration of ~7–8 ppm and pH 8. Fourier transform infrared spectroscopy and solid-state NMR analyses indicated that a fraction of amidoxime groups was hydrolyzed to carboxylate during KOH conditioning. The uranium adsorption capacity in the simulated seawater screening solution gradually increased with conditioning time and temperature for all KOH concentrations. It was also observed that the adsorption capacity increased with an increase in concentration of KOH for all the conditioning times and temperatures. AF160-2 adsorbent samples were also tested with natural seawater using flow-through experiments to determine uranium adsorption capacity with varying KOH conditioning time and temperature. Based on uranium loading capacity values of several AF160-2 samples, it was observed that changing KOH conditioning time from 3 to 1 h at 60, 70, and 80 °C resulted in an increase of the uranium loading capacity in seawater, which did not follow the trend found in laboratory screening with stimulated solutions. Longer KOH conditioning times lead to significantly higher uptake of divalent metal ions, such as calcium and magnesium, which is a result of amidoxime conversion into less selective carboxylate. The scanning electron microscopy showed that long conditioning

  14. An NMR determination of CO diffusion on platinum electrocatalysts.

    PubMed

    Kobayashi, Takeshi; Babu, Panakkattu K; Gancs, Lajos; Chung, Jong Ho; Oldfield, Eric; Wieckowski, Andrzej

    2005-10-19

    We report the first direct measurement of CO diffusion on nanoparticle Pt electrocatalysts at the solid/liquid interface, carried out using 13C nuclear magnetic resonance (NMR) with a spin-labeling pulse sequence. Diffusion parameters were measured in the temperature range of 253-293 K for CO adsorbed on commercial Pt-black under saturation coverage. 2H NMR of the same system indicates that the electrolyte remains in the liquid state at temperatures where the CO diffusion experiments were performed. The CO diffusion parameters follow typical Arrhenius behavior with an activation energy of 6.0 +/- 0.4 kcal/mol and a pre-exponential factor of (1.1 +/- 0.6) x 10-8 cm2/s. Exchange between different CO populations, driven by a chemical potential gradient, is suggested to be the main mechanism for CO diffusion. The presence of the electrolyte medium considerably slows down the diffusion of CO as compared to that seen on surfaces of bulk metals under UHV conditions. This work opens up a new approach to the study of surface diffusion of adsorbed molecules on nanoparticle electrode catalysts, including the possibility of correlating diffusion parameters to catalytic activity in real world applications of broad general interest. PMID:16218593

  15. Elution of uranium and transition metals from amidoxime-based polymer adsorbents for sequestering uranium from seawater

    DOE PAGESBeta

    Pan, Horng-Bin; Kuo, Li-Jung; Miyamoto, Naomi; Wood, Jordana; Strivens, Jonathan E.; Gill, Gary; Janke, Christopher James; Wai, Chien

    2015-11-30

    High-surface-area amidoxime and carboxylic acid grafted polymer adsorbents developed at Oak Ridge National Laboratory were tested for sequestering uranium in a flowing seawater flume system at the PNNL-Marine Sciences Laboratory. FTIR spectra indicate that a KOH conditioning process is necessary to remove the proton from the carboxylic acid and make the sorbent effective for sequestering uranium from seawater. The alkaline conditioning process also converts the amidoxime groups to carboxylate groups in the adsorbent. Both Na2CO3 H2O2 and hydrochloric acid elution methods can remove ~95% of the uranium sequestered by the adsorbent after 42 days of exposure in real seawater. Themore » Na2CO3 H2O2 elution method is more selective for uranium than conventional acid elution. Iron and vanadium are the two major transition metals competing with uranium for adsorption to the amidoxime-based adsorbents in real seawater. Tiron (4,5-Dihydroxy-1,3-benzenedisulfonic acid disodium salt, 1 M) can remove iron from the adsorbent very effectively at pH around 7. The coordination between vanadium (V) and amidoxime is also discussed based on our 51V NMR data.« less

  16. Elution of uranium and transition metals from amidoxime-based polymer adsorbents for sequestering uranium from seawater

    SciTech Connect

    Pan, Horng-Bin; Kuo, Li-Jung; Miyamoto, Naomi; Wood, Jordana; Strivens, Jonathan E.; Gill, Gary; Janke, Christopher James; Wai, Chien

    2015-11-30

    High-surface-area amidoxime and carboxylic acid grafted polymer adsorbents developed at Oak Ridge National Laboratory were tested for sequestering uranium in a flowing seawater flume system at the PNNL-Marine Sciences Laboratory. FTIR spectra indicate that a KOH conditioning process is necessary to remove the proton from the carboxylic acid and make the sorbent effective for sequestering uranium from seawater. The alkaline conditioning process also converts the amidoxime groups to carboxylate groups in the adsorbent. Both Na2CO3 H2O2 and hydrochloric acid elution methods can remove ~95% of the uranium sequestered by the adsorbent after 42 days of exposure in real seawater. The Na2CO3 H2O2 elution method is more selective for uranium than conventional acid elution. Iron and vanadium are the two major transition metals competing with uranium for adsorption to the amidoxime-based adsorbents in real seawater. Tiron (4,5-Dihydroxy-1,3-benzenedisulfonic acid disodium salt, 1 M) can remove iron from the adsorbent very effectively at pH around 7. The coordination between vanadium (V) and amidoxime is also discussed based on our 51V NMR data.

  17. Trivalent chromium removal from aqueous solutions by a sol–gel synthesized silica adsorbent functionalized with sulphonic acid groups

    SciTech Connect

    Gomez-Gonzalez, Sergio Efrain; Carbajal-Arizaga, Gregorio Guadalupe; Manriquez-Gonzalez, Ricardo; De la Cruz-Hernandez, Wencel; Gomez-Salazar, Sergio

    2014-11-15

    Highlights: • Corpuscular sulphonic acid-functionalized silica holds improved uptake of chromium. • Mesopores on adsorbent facilitate (CH{sub 3}COO){sub 2}Cr{sup +} ion uptake on sulphonate sites. • Formation of chromium acetate sulphonate complex proposed from XPS results. • Fixed bed chromium uptake results suggest potential industrial use. - Abstract: A high capacity hybrid silica adsorbent was synthesized via sol–gel processing with sulphonic acid groups as trivalent chromium complex ions chelators from aqueous solutions. The synthesis included co-condensation of tetraethoxysilane (TEOS) with 3-(mercaptopropyl)trimethoxysilane (MPS), and oxidation of thiol to sulphonic acid groups. Chromium uptake kinetic, batch and fixed-bed experiments were performed to assess the removal of this metal from aqueous solutions. {sup 13}C, {sup 29}Si CPMAS NMR, FTIR, XPS were used to characterize the adsorbent structure and the nature of chromium complexes on the adsorbent surface. Chromium maximum uptake was obtained at pH 3 (72.8 mg/g). Elemental analysis results showed ligand density of 1.48 mmol sulphonic groups/g. About 407 mL of Cr(III) solution (311 mg/L) were treated to breakthrough point reaching ≤0.06 mg/L at the effluent. These results comply with USEPA regulation for chromium concentration in drinking water (≤0.1 mg/L). The adsorbent shows potential to be used in chromium separations to the industrial level.

  18. The biogeochemical cycle of the adsorbed template. II - Selective adsorption of mononucleotides on adsorbed polynucleotide templates

    NASA Technical Reports Server (NTRS)

    Lazard, Daniel; Lahav, Noam; Orenberg, James B.

    1988-01-01

    Experimental results are presented for the verification of the specific interaction step of the 'adsorbed template' biogeochemical cycle, a simple model for a primitive prebiotic replication system. The experimental system consisted of gypsum as the mineral to which an oligonucleotide template attaches (Poly-C or Poly-U) and (5-prime)-AMP, (5-prime)-GMP, (5-prime)-CMP and (5-prime)-UMP as the interacting biomonomers. When Poly-C or Poly-U were used as adsorbed templates, (5-prime)-GMP and (5-prime)-AMP, respectively, were observed to be the most strongly adsorbed species.

  19. Unoccupied electronic states in adsorbate systems

    NASA Astrophysics Data System (ADS)

    Bertel, E.

    1991-11-01

    Experimental work on unoccupied electronic states in adsorbate systems on metallic substrates is reviewed with emphasis on recent developments. The first part is devoted to molecular adsorbates. Weakly chemisorbed hydrocarbons are briefly discussed. An exhaustive inverse photoemission (IPE) study of the CO bond to the transition metals Ni, Pb, and Pt is presented. Adsorbed NO is taken as an example to demonstrate the persisting discrepancies in the interpretation of IPE spectra. Atomic adsorbates are discussed in the second part. The quantum well state model is applied to interpret the surface states in reconstructing and non-reconstructing adsorption systems of alkali metals and hydrogen. A recent controversy on the unoccupied electronic states of the Cu(110)/O p(2×1) surface is critically reviewed. The quantum well state model is then compared to tight binding and local-density-functional calculations of the unoccupied bands and the deficiencies of the various approaches are pointed out. Finally, the relation between the surface state model and more chemically oriented models of surface bonding is briefly discussed.

  20. TRANSFORMATION AND MOBILIZATION OF ARSENIC ADSORBED ON GRANULAR FERRIC HYDROXIDE UNDER BIO-REDUCTIVE CONDITIONS

    EPA Science Inventory

    Biotic and abiotic reduction of arsenic (V) and iron (III) influences the partioning of arsenic (As) between the solid and aqueous phases in soils, sediments and wastes. In this study, laboratory experiments on arsenic adsorbed on granular ferric hydroxide (GFH) was performed to ...

  1. 19F Magic angle spinning NMR reporter molecules: empirical measures of surface shielding, polarisability and H-bonding.

    PubMed

    Budarin, Vitaliy L; Clark, James H; Deswarte, Fabien E I; Mueller, Karl T; Tavener, Stewart J

    2007-06-14

    Magic Angle Spinning (MAS) (19)F NMR spectra have been obtained and chemical shifts measured for 37 molecules in the gas phase and adsorbed on the surfaces of six common materials: octadecyl- and octyl-functionalised chromatography silicas, Kieselgel 100 silica, Brockmann neutral alumina, Norit activated charcoal and 3-(1-piperidino)propyl functionalised silica. From these six surfaces, octadecyl-silica is selected as a non-polar reference to which the others are compared. The change in chemical shift of a fluorine nucleus within a molecule on adsorption to a surface from the gas phase, Deltadelta(gas)(surface), is described by the empirical relationship: Deltadelta(gas)(surface) = delta(s) + (alpha(s)+pi(s))/alpha(r) (Deltadelta(gas)(reference) - delta(r)) + delta(HBA) + delta(HBD), where delta(s) and delta(r) are constants that describe the chemical shift induced by the electromagnetic field of the surface under investigation and reference surface, alpha(s) and alpha(r) are the relative surface polarisability for the surface and reference, pi(s) is an additional contribution to the surface polarisabilities due to its ability to interact with aromatic molecules, and delta(HBA) and delta(HBD) are measurements of the hydrogen acceptor and donor properties of the surface. These empirical parameters are measured for the surfaces under study. Silica and alumina are found to undergo specific interactions with aromatic reporter molecules and both accept and donate H-bonds. Activated charcoal was found to have an extreme effect on shielding but no specific interactions with the adsorbed molecules. 3-(1-Piperidino)propyl functionalised silica exhibits H-bond acceptor ability, but does not donate H-bonds. PMID:17487325

  2. Determination of the effect of different additives in coking blends using a combination of in situ high-temperature {sup 1}H NMR and rheometry

    SciTech Connect

    Miguel C. Diaz; Karen M. Steel; Trevor C. Drage; John W. Patrick; Colin E. Snape

    2005-12-01

    High-temperature {sup 1}H NMR and rheometry measurements were carried out on 4:1 wt/wt blends of a medium volatile bituminous coal with two anthracites, two petroleum cokes, charcoal, wood, a low-temperature coke breeze, tyre crumb, and active carbon to determine the effects on fluidity development to identify the parameters responsible for these effects during pyrolysis and to study possible relationships among the parameters derived from these techniques. Positive, negative, and neutral effects were identified on the concentration of fluid material. Small positive effects (ca. 5-6%) were caused by blending the coal with petroleum cokes. Charcoal, wood, and active carbon all exerted negative effects on concentration (18-27% reduction) and mobility (12-25% reduction in T2) of the fluid phase, which have been associated with the inert character and high surface areas of these additives that adsorb the fluid phase of the coal. One of the anthracites and the low-temperature coke breeze caused deleterious effects to a lesser extent on the concentration (7-12%) and mobility (13-17%) of the fluid material, possibly due to the high concentration of metals in these additives (ca. 11% ash). Despite the high fluid character of tyre crumb at the temperature of maximum fluidity of the coal (73%), the mobility of the fluid phase of the blend was lower than expected. The comparison of {sup 1}H NMR and rheometry results indicated that to account for the variations in minimum complex viscosity for all the blends, both the maximum concentration of fluid phase and the maximum mobility of the fluid material had to be considered. For individual blends, two exponential relationships have been found between the complex viscosity and the concentration of solid phase in both the softening and resolidification stages but the parameters are different for each blend. 30 refs., 8 figs., 5 tabs.

  3. THz Dynamic Nuclear Polarization NMR

    PubMed Central

    Nanni, Emilio A.; Barnes, Alexander B.; Griffin, Robert G.; Temkin, Richard J.

    2013-01-01

    Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The enhancement in NMR sensitivity can amount to a factor of well above 100, enabling faster data acquisition and greatly improved NMR measurements. With the increasing magnetic fields (up to 23 T) used in NMR research, the required frequency for DNP falls into the THz band (140–600 GHz). Gyrotrons have been developed to meet the demanding specifications for DNP NMR, including power levels of tens of watts; frequency stability of a few megahertz; and power stability of 1% over runs that last for several days to weeks. Continuous gyrotron frequency tuning of over 1 GHz has also been demonstrated. The complete DNP NMR system must include a low loss transmission line; an optimized antenna; and a holder for efficient coupling of the THz radiation to the sample. This paper describes the DNP NMR process and illustrates the THz systems needed for this demanding spectroscopic application. THz DNP NMR is a rapidly developing, exciting area of THz science and technology. PMID:24639915

  4. THz Dynamic Nuclear Polarization NMR.

    PubMed

    Nanni, Emilio A; Barnes, Alexander B; Griffin, Robert G; Temkin, Richard J

    2011-08-29

    Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The enhancement in NMR sensitivity can amount to a factor of well above 100, enabling faster data acquisition and greatly improved NMR measurements. With the increasing magnetic fields (up to 23 T) used in NMR research, the required frequency for DNP falls into the THz band (140-600 GHz). Gyrotrons have been developed to meet the demanding specifications for DNP NMR, including power levels of tens of watts; frequency stability of a few megahertz; and power stability of 1% over runs that last for several days to weeks. Continuous gyrotron frequency tuning of over 1 GHz has also been demonstrated. The complete DNP NMR system must include a low loss transmission line; an optimized antenna; and a holder for efficient coupling of the THz radiation to the sample. This paper describes the DNP NMR process and illustrates the THz systems needed for this demanding spectroscopic application. THz DNP NMR is a rapidly developing, exciting area of THz science and technology. PMID:24639915

  5. In situ solid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach.

    PubMed

    Zhang, Weiping; Xu, Shutao; Han, Xiuwen; Bao, Xinhe

    2012-01-01

    In situ solid-state NMR is a well-established tool for investigations of the structures of the adsorbed reactants, intermediates and products on the surface of solid catalysts. The techniques allow identifications of both the active sites such as acidic sites and reaction processes after introduction of adsorbates and reactants inside an NMR rotor under magic angle spinning (MAS). The in situ solid-state NMR studies of the reactions can be achieved in two ways, i.e. under batch-like or continuous-flow conditions. The former technique is low cost and accessible to the commercial instrument while the latter one is close to the real catalytic reactions on the solids. This critical review describes the research progress on the in situ solid-state NMR techniques and the applications in heterogeneous catalysis under batch-like and continuous-flow conditions in recent years. Some typical probe molecules are summarized here to detect the Brønsted and Lewis acidic sites by MAS NMR. The catalytic reactions discussed in this review include methane aromatization, olefin selective oxidation and olefin metathesis on the metal oxide-containing zeolites. With combining the in situ MAS NMR spectroscopy and the density functional theoretical (DFT) calculations, the intermediates on the catalyst can be identified, and the reaction mechanism is revealed. Reaction kinetic analysis in the nanospace instead of in the bulk state can also be performed by employing laser-enhanced MAS NMR techniques in the in situ flow mode (163 references). PMID:21743940

  6. The metal-organic framework MIL-101(Cr) as efficient adsorbent in a vortex-assisted dispersive solid-phase extraction of imatinib mesylate in rat plasma coupled with ultra-performance liquid chromatography/mass spectrometry: Application to a pharmacokinetic study.

    PubMed

    Qi, Chao; Cai, Qianqian; Zhao, Pan; Jia, Xiuna; Lu, Nan; He, Lu; Hou, Xiaohong

    2016-06-01

    Metal-organic framework MIL-101(Cr) was successfully used as an efficient sorbent in a vortex-assisted dispersive solid-phase extraction (VA-DSPE) and applied for the determination and the pharmacokinetic of imatinib mesylate in rat plasma by UPLC-MS/MS. In the enrichment of imatinib from rat plasma, the analyte was efficiently adsorbed on MIL-101(Cr) and simply recovered by using initial mobile phase (0.1% formic acid-methanol (6:4 v/v)) as elution solvent. Meanwhile, the protein in the plasma samples was excluded from the porous structure of MIL-101(Cr), leading to direct extraction of drug molecule from protein-rich biological samples without any other pretreatment procedure. After being removed, the supernatant was filtered and directly injected into the UPLC-MS/MS for the analysis of the target. The experimental parameters, including nature of MOFs, amount of MIL-101(Cr), pH value of aqueous solution, extraction time, type and volume of elution solvent, were systematically optimized. After VA-DSPE, chromatographic separation was performed on an ACQUITY UPLC(®) BEH C18 column (2.1mm×100mm, 1.7μm) with a 3min gradient elution using 0.1% formic acid and methanol as mobile phase at a flow rate of 0.3mL/min. The detection was accomplished on a tandem mass spectrometer via an electrospray ionization (ESI) source by multiple reaction monitoring (MRM) in the positive ionization mode. The lower limit of quantification of 1ng/mL was achieved and the mean recovery of the analyte was higher than 81.2%. Moreover, computational simulation was primarily applied to predict the adsorption behavior and revealed the molecular interactions and free binding energies between MIL-101(Cr) and imatinib with the molecular modeling method, providing certain explanation of the adsorption mechanism. The originally established pretreatment and detection method has some merits, such as less solvent consumption, easy operation, higher sensitivity and lower matrix effect. And the MIL-101

  7. Two-dimensional NMR spectroscopy

    SciTech Connect

    Croasmun, W.R.; Carlson, R.M.K.

    1987-01-01

    Written for chemists and biochemists who are not NMR spectroscopists, but who wish to use the new techniques of two-dimensional NMR spectroscopy, this book brings together for the first time much of the practical and experimental data needed. It also serves as information source for industrial, academic, and graduate student researchers who already use NMR spectroscopy, but not yet in two dimensions. The authors describe the use of 2-D NMR in a wide variety of chemical and biochemical fields, among them peptides, steroids, oligo- and poly-saccharides, nucleic acids, natural products (including terpenoids, alkaloids, and coal-derived heterocyclics), and organic synthetic intermediates. They consider throughout the book both the advantages and limitations of using 2-D NMR.

  8. NMR CHARACTERIZATIONS OF PROPERTIES OF HETEROGENEOUS MEDIA

    SciTech Connect

    C.T. Philip Chang; Changho Choi; Jeromy T. Hollenshead; Rudi Michalak; Jack Phan; Ramon Saavedra; John C. Slattery; Jinsoo Uh; Randi Valestrand; A. Ted Watson; Song Xue

    2005-01-01

    developed methodology using that data to determine spatially resolved permeability distributions. We investigate the use of intrinsic properties for developing improved correlations for predicting permeability from NMR well-logging data and for obtaining more accurate estimates of multiphase flow properties--the relative permeability and capillary pressure--from displacement experiments. We demonstrate the use of MRI measurements of saturation and relaxation for prediction wetting-phase relative permeability for unstable experiments. Finally, we developed an improved method for determining surface relaxivity with NMR experiments, which can provide better descriptions of permeable media microstructures and improved correlations for permeability predictions.

  9. Earth's field NMR; a surface moisture detector?

    NASA Astrophysics Data System (ADS)

    Fukushima, Eiichi; Altobelli, Stephen; McDowell, Andrew; Zhang, Tongsheng

    2012-10-01

    Earth's field NMR (EFNMR), being free of magnets, would be an ideal teaching medium as well as a mobile NMR technique except for its weak S/N. The common EFNMR apparatus uses a powerful prepolarization field to enhance the spin magnetization before the experiment. We introduce a coil design geared to larger but manageable samples with sufficient sensitivity without prepolarization to move EFNMR closer to routine use and to provide an inexpensive teaching tool. Our coil consists of parallel wires spread out on a plywood to form a current sheet with the current return wires separated so they will not influence the main part of the coil assembly. The sensitive region is a relatively thin region parallel to the coil and close to it. A single turn of the coil is wound to be topologically equivalent to a figure-8. The two crossing segments in the center of a figure-8 form two of the parallel wires of the flat coil. Thus, a two-turn figure-8 has four crossing wires so its topologically equivalent coil will have four parallel wires with currents in phase. Together with the excellent sensitivity, this coil offers outstanding interference rejection because of the figure-8 geometry. An example of such a coil has 328 parallel wires covering a ˜1 meter square plywood which yields a good NMR signal from 26 liters of water spread out roughly over the area of the coil in less than one minute in a nearby park.

  10. Catalysts of Cu(II) and Co(II) ions adsorbed in chitosan used in transesterification of soy bean and babassu oils - a new route for biodiesel syntheses.

    PubMed

    da Silva, Rondinelly Brandão; Lima Neto, Alcides Fernandes; Soares Dos Santos, Lucas Samuel; de Oliveira Lima, José Renato; Chaves, Mariana Helena; Dos Santos, José Ribeiro; de Lima, Geraldo Magela; de Moura, Edmilson Miranda; de Moura, Carla Verônica Rodarte

    2008-10-01

    Catalysts of Cu(II) and Co(II) adsorbed in chitosan was used in transesterification of soy bean and babassu oils. The catalysts were characterized by infrared, atomic absorption and TG, and biodiesels was characterized by infrared, NMR, CG, TG, physic chemistry analysis. The maximum adsorption values found for copper and cobalt cations were 1.584 and 1.260mgg(-1), respectively, in 180min. However, conversion of oils in biodiesel was better when used Co(II) adsorbed in chitosan. PMID:18440802

  11. Natural Transformation of Azotobacter vinelandii by Adsorbed Chromosomal DNA: Role of Adsorbed DNA Conformation

    NASA Astrophysics Data System (ADS)

    Lv, N.; Zilles, J.; Nguyen, H.

    2008-12-01

    Recent increases in antibiotic resistance among pathogenic microorganisms and the accompanying public health concerns result both from the widespread use of antibiotics and from the transfer of antibiotic resistance genes among microorganisms. To understand the transfer of antibiotic resistance genes and identify efficient measures to minimize these transfers, an interdisciplinary approach was used to identify physical and chemical factors that control the fate and biological availability of extracellular DNA. Quartz crystal microbalance with dissipation (QCM-D) was used to study extracellular DNA adsorption and the conformation of the adsorbed DNA on silica and natural organic matter (NOM) surfaces. Solution chemistry was varied systematically to investigate the role of adsorbed DNA conformation on transformation. Gene transfer was assessed under the same conditions using natural transformation of chromosomal DNA into the soil bacteria Azotobacter vinelandii. DNA adsorbed to both silica and NOM surfaces has a more compact and rigid conformation in the presence of Ca2+ compared to Na+. Extracellular DNA adsorbed on silica and NOM surfaces transformed A. vinelandii. The transformation efficiency of adsorbed DNA was up to 4 orders of magnitude lower than that of dissolved DNA. Preliminary results suggest that the presence of Ca2+ in groundwater (e.g. hardness) reduces the availability of adsorbed DNA for transformation.

  12. Fibrous adsorbent for removal of aqueous aromatic hydrocarbons.

    PubMed

    Jung, Yong-Jun; Kiso, Yoshiaki; Oguchi, Tatsuo; Yamada, Toshiro; Takagi, Hiroo; Nishimura, Kazuyuki

    2007-01-01

    Bundles of a strongly hydrophobic fibrous material (p-phenylene-2,6-benzobisoxazole; PBO; Zylon) were employed as an adsorbent for the removal of aqueous aromatic compounds, because the PBO fibers are too rigid to be woven and did not entrap suspended solids. The removal performance for nine kinds of polyaromatic hydrocarbons (PAHs) and di-(2-ethylhexyl) phthalate (DEHP) was evaluated. PAHs and DEHP at initial concentrations of 50 microg L(-1) were removed at 72.5-99.9% and ca. 95%, respectively, although the removal efficiencies were affected by the phase ratio (fiber weight/solution volume). The logarithm of the partition coefficient (log K) for planar PAHs was linearly correlated with the logarithm of the n-octanol/water partition coefficient (log P), but nonplanar PAHs, such as cis-stilbene, p-terphenyl, and o-terphenyl, showed significantly lower adsorption performance. The adsorbed PAHs were not desorbed effectively with CH3CN, CH2Cl2, and toluene. On the other hand, DEHP was effectively desorbed with methanol. PMID:17585293

  13. EMERGING TECHNOLOGY SUMMARY: DEMONSTRATION OF AMBERSORB 563 ADSORBENT TECHNOLOGY

    EPA Science Inventory

    A field pilot study was conducted to demonstrate the technical feasibility and cost-effectiveness of Ambersorb® 5631 carbonaceous adsorbent for remediating groundwater contaminated with volatile organic compounds (VOCs). The Ambersorb adsorbent technology demonstration consist...

  14. NMR Characterizations of Properties of Heterogeneous Media

    SciTech Connect

    Uh, Jinsoo; Phan, Jack; Xue, Dong; Watson, A. Ted

    2003-01-28

    The overall goal of this project was to develop reliable methods for resolving macroscopic properties important for describing the flow of one or more fluid phases in reservoirs from formation measurements. During this reporting period, the determination of surface relaxivity from NMR data was investigated. A new method for determining the surface relaxivity from measured data was developed and tested with data obtained from an Exxon sample. The new method avoids the use of a certain mathematical short-time approximation in the data analysis, which has been shown to be unsuitable.

  15. Multinuclear NMR approach to coal fly ash characterization

    SciTech Connect

    Netzel, D.A.

    1991-09-01

    This report describes the application of various nuclear magnetic resonance (NMR) techniques to study the hydration kinetics and mechanisms, the structural properties, and the adsorption characteristics of coal fly ash. Coal fly ash samples were obtained from the Dave Johnston and Laramie River electric power generating plants in Wyoming. Hydrogen NMR relaxation times were measured as a function of time to observe the kinetics of hydration for the two coal fly ashes at different temperatures and water-to-cement ration. The kinetic data for the hydrated coal fly ashes were compared to the hydration of portland cement. The mechanism used to describe the kinetic data for the hydration of portland cement was applied, with reservation, to describe the hydration of the coal fly ashes. The results showed that the coal fly ashes differ kinetically from that of portland cement and from each other. Consequently, both coal fly ashes were judged to be poorer cementitious materials than portland cement. Carbon-13 NMR CP/MAS spectra were obtained for the anhydrous coal fly ashes in an effort to determine the type of organic species that may be present, either adsorbed on the surface or entrained.

  16. NMR of small solutes in liquid crystals and molecular sieves

    NASA Astrophysics Data System (ADS)

    Ylihautala, Mika Petri

    The present thesis deals with the nuclear magnetic resonance (NMR) spectroscopy of small solutes applied to the studies of liquid crystals and molecular sieves. In this method, changes induced by the investigated environment to the static spectral parameters (i.e. nuclear shielding, indirect and direct spin-spin coupling and quadrupole coupling) of the solute are measured. The nuclear shielding of dissolved noble gases is utilized for the studies of thermotropic liquid crystals. The relation between the symmetry properties of mesophases and the nuclear shielding is described. The different interaction mechanisms perturbing the observed noble gas nuclear shielding are discussed, particularly, the role of long-range attractive van der Waals interactions is brought out. The suitability of the noble gas NMR spectroscopy to the studies of Iyotropic liquid crystals is investigated in terms of nuclear shielding and quadrupole coupling interactions. In molecular sieve systems, the effect of inter- and intracrystalline motions of solutes on their NMR spectra is discussed. A novel method for the measurement of the intracrystalline motions is developed. The distinctions in the 13C shielding of methane adsorbed in AlPO4-11 and SAPO-11, two structurally similar molecular sieves differing in composition, are indicated.

  17. Modeling of chlorophenols competitive adsorption on soils by means of the ideal adsorbed solution theory.

    PubMed

    Baciocchi, Renato; Boni, Maria Rosaria; Lavecchia, Roberto

    2005-02-14

    The adsorption of 3-chlorophenol (3-CP) and 3,5-dichlorophenol (3,5-CP) on two Italian soils was studied at 20 degrees C. Experiments on the pure components showed that 3,5-CP was more strongly adsorbed than 3-CP, and that the adsorption capacity could be related to the organic carbon fraction of the soil. Competitive adsorption data were described by the fully predictive ideal adsorbed solution (IAS) theory. To this end, the Langmuir parameters determined from pure component adsorption data were used. Results showed that at low 3,5-CP concentration (up to 5-10 mM) the model describes satisfactorily the binary system behavior, whereas at higher concentrations predictions fail, suggesting that non ideality effects in the adsorbed phase should be accounted for. PMID:15721549

  18. Properties and potential environmental applications of carbon adsorbents from waste tire rubber

    USGS Publications Warehouse

    Lehmann, C.M.B.; Rameriz, D.; Rood, M.J.; Rostam-Abadi, M.

    2000-01-01

    The properties of tire-derived carbon adsorbents (TDCA) produced from select tire chars were compared with those derived from an Illinois coal and pistachio nut shells. Chemical analyses of the TDCA indicated that these materials contain metallic elements not present in coal-and nut shell-derived carbons. These metals, introduced during the production of tire rubber, potentially catalyze steam gasification reactions of tire char. TDCA carbons contained larger meso-and macopore volumes than their counterparts derived from coal and nut shell (on the moisture-and ash-free-basis). Adsorptive properties of the tire-derived adsorbent carbons for air separation, gas storage, and gas clean up were also evaluated and compared with those of the coal-and nut shell derived carbons as well as a commercial activated carbon. The results revealed that TDCA carbons are suitable adsorbents for removing vapor-phase mercury from combustion flue gases and hazardous organic compounds from industrial gas streams.

  19. Chemical shift referencing in MAS solid state NMR

    NASA Astrophysics Data System (ADS)

    Morcombe, Corey R.; Zilm, Kurt W.

    2003-06-01

    Solid state 13C magic angle spinning (MAS) NMR spectra are typically referenced externally using a probe which does not incorporate a field frequency lock. Solution NMR shifts on the other hand are more often determined with respect to an internal reference and using a deuterium based field frequency lock. Further differences arise in solution NMR of proteins and nucleic acids where both 13C and 1H shifts are referenced by recording the frequency of the 1H resonance of DSS (sodium salt of 2,2-dimethyl-2-silapentane-5-sulphonic acid) instead of TMS (tetramethylsilane). In this note we investigate the difficulties in relating shifts measured relative to TMS and DSS by these various approaches in solution and solids NMR, and calibrate adamantane as an external 13C standard for solids NMR. We find that external chemical shift referencing of magic angle spinning spectra is typically quite reproducible and accurate, with better than ±0.03 ppm accuracy being straight forward to achieve. Solid state and liquid phase NMR shifts obtained by magic angle spinning with external referencing agree with those measured using typical solution NMR hardware with the sample tube aligned with the applied field as long as magnetic susceptibility corrections and solvent shifts are taken into account. The DSS and TMS reference scales for 13C and 1H are related accurately using MAS NMR. Large solvent shifts for the 13C resonance in TMS in either deuterochloroform or methanol are observed, being +0.71 ppm and -0.74 ppm from external TMS, respectively. The ratio of the 13C resonance frequencies for the two carbons in solid adamantane to the 1H resonance of TMS is reported.

  20. Chemical shift referencing in MAS solid state NMR.

    PubMed

    Morcombe, Corey R; Zilm, Kurt W

    2003-06-01

    Solid state 13C magic angle spinning (MAS) NMR spectra are typically referenced externally using a probe which does not incorporate a field frequency lock. Solution NMR shifts on the other hand are more often determined with respect to an internal reference and using a deuterium based field frequency lock. Further differences arise in solution NMR of proteins and nucleic acids where both 13C and 1H shifts are referenced by recording the frequency of the 1H resonance of DSS (sodium salt of 2,2-dimethyl-2-silapentane-5-sulphonic acid) instead of TMS (tetramethylsilane). In this note we investigate the difficulties in relating shifts measured relative to TMS and DSS by these various approaches in solution and solids NMR, and calibrate adamantane as an external 13C standard for solids NMR. We find that external chemical shift referencing of magic angle spinning spectra is typically quite reproducible and accurate, with better than +/-0.03 ppm accuracy being straight forward to achieve. Solid state and liquid phase NMR shifts obtained by magic angle spinning with external referencing agree with those measured using typical solution NMR hardware with the sample tube aligned with the applied field as long as magnetic susceptibility corrections and solvent shifts are taken into account. The DSS and TMS reference scales for 13C and 1H are related accurately using MAS NMR. Large solvent shifts for the 13C resonance in TMS in either deuterochloroform or methanol are observed, being +0.71 ppm and -0.74 ppm from external TMS, respectively. The ratio of the 13C resonance frequencies for the two carbons in solid adamantane to the 1H resonance of TMS is reported. PMID:12810033

  1. Analysis of Adsorbed Natural Gas Tank Technology

    NASA Astrophysics Data System (ADS)

    Knight, Ernest; Schultz, Conrad; Rash, Tyler; Dohnke, Elmar; Stalla, David; Gillespie, Andrew; Sweany, Mark; Seydel, Florian; Pfeifer, Peter

    With gasoline being an ever decreasing finite resource and with the desire to reduce humanity's carbon footprint, there has been an increasing focus on innovation of alternative fuel sources. Natural gas burns cleaner, is more abundant, and conforms to modern engines. However, storing compressed natural gas (CNG) requires large, heavy gas cylinders, which limits space and fuel efficiency. Adsorbed natural gas (ANG) technology allows for much greater fuel storage capacity and the ability to store the gas at a much lower pressure. Thus, ANG tanks are much more flexible in terms of their size, shape, and weight. Our ANG tank employs monolithic nanoporous activated carbon as its adsorbent material. Several different configurations of this Flat Panel Tank Assembly (FPTA) along with a Fuel Extraction System (FES) were examined to compare with the mass flow rate demands of an engine.

  2. Gas storage using fullerene based adsorbents

    NASA Technical Reports Server (NTRS)

    Loutfy, Raouf O. (Inventor); Lu, Xiao-Chun (Inventor); Li, Weijiong (Inventor); Mikhael, Michael G. (Inventor)

    2000-01-01

    This invention is directed to the synthesis of high bulk density high gas absorption capacity adsorbents for gas storage applications. Specifically, this invention is concerned with novel gas absorbents with high gravimetric and volumetric gas adsorption capacities which are made from fullerene-based materials. By pressing fullerene powder into pellet form using a conventional press, then polymerizing it by subjecting the fullerene to high temperature and high inert gas pressure, the resulting fullerene-based materials have high bulk densities and high gas adsorption capacities. By pre-chemical modification or post-polymerization activation processes, the gas adsorption capacities of the fullerene-based adsorbents can be further enhanced. These materials are suitable for low pressure gas storage applications, such as oxygen storage for home oxygen therapy uses or on-board vehicle natural gas storage. They are also suitable for storing gases and vapors such as hydrogen, nitrogen, carbon dioxide, and water vapor.

  3. PVDF membranes containing hybrid nanoparticles for adsorbing cationic dyes: physical insights and mechanism

    NASA Astrophysics Data System (ADS)

    Sharma, Maya; Madras, Giridhar; Bose, Suryasarathi

    2016-07-01

    In this study, Fe (iron) and Ag (silver) based adsorbents were synthesized using solution combustion and in situ reduction techniques. The synthesized adsorbents were comprehensively characterized by different techniques including electron microscopy, BET, XRD, Zeta potential etc. Three chlorinated cationic dyes used were malachite green, methyl violet and pyronin Y. These dyes were adsorbed on various synthesized adsorbents [iron III oxide (Fe2O3)], iron III oxide decorated silver nanoparticles by combustion synthesis technique [Fe2O3–Ag(C)] and iron III oxide decorated silver nanoparticles using in situ reduction, [Fe2O3–Ag (S)]. The isotherm and the adsorption kinetics have been studied systematically. The kinetic data can be explained by the pseudo second order model and the adsorption equilibrium followed Langmuir isotherm. The equilibrium and kinetics results suggest that Fe2O3–Ag(S) nanoparticles showed the maximum adsorption among all the adsorbents. Hence, Polyvinylidene fluoride based membranes containing Fe2O3–Ag(S) nanoparticles were prepared via phase inversion (precipitation immersion using DMF/water) technique. The adsorption kinetics were studied in detail and it was observed that the composite membrane showed synergistic improvement in dye adsorption. Such membranes can be used for water purification.

  4. In Situ NMR Spectroscopy of Supercapacitors: Insight into the Charge Storage Mechanism

    PubMed Central

    2013-01-01

    Electrochemical capacitors, commonly known as supercapacitors, are important energy storage devices with high power capabilities and long cycle lives. Here we report the development and application of in situ nuclear magnetic resonance (NMR) methodologies to study changes at the electrode–electrolyte interface in working devices as they charge and discharge. For a supercapacitor comprising activated carbon electrodes and an organic electrolyte, NMR experiments carried out at different charge states allow quantification of the number of charge storing species and show that there are at least two distinct charge storage regimes. At cell voltages below 0.75 V, electrolyte anions are increasingly desorbed from the carbon micropores at the negative electrode, while at the positive electrode there is little change in the number of anions that are adsorbed as the voltage is increased. However, above a cell voltage of 0.75 V, dramatic increases in the amount of adsorbed anions in the positive electrode are observed while anions continue to be desorbed at the negative electrode. NMR experiments with simultaneous cyclic voltammetry show that supercapacitor charging causes marked changes to the local environments of charge storing species, with periodic changes of their chemical shift observed. NMR calculations on a model carbon fragment show that the addition and removal of electrons from a delocalized system should lead to considerable increases in the nucleus-independent chemical shift of nearby species, in agreement with our experimental observations. PMID:24274637

  5. Interactions between Nafion resin and protonated dodecylamine modified montmorillonite: a solid state NMR study.

    PubMed

    Zhang, Limin; Xu, Jun; Hou, Guangjin; Tang, Huiru; Deng, Feng

    2007-07-01

    A series of nanocomposites have been prepared from perfluorosulfonylfluoride copolymer resin (Nafion) and layered montmorillonite (MMT) modified with protonated dodecylamine by conventional sol-gel intercalation. The structure of these nanocomposite materials have been characterized using FT-IR, elemental analysis, XRD and solid state NMR techniques, including 19F magic-angle spinning (MAS) NMR, 19F NMR relaxation time measurements, 29Si MAS, 1H MAS, 1H-13C cross-polarization magic-angle spinning (CPMAS), and 1H-13C heteronuclear correlation (HETCOR) 2D NMR. The results showed that thermal stability of Nafion was improved moderately by the addition of dodecylamine modified MMT without intercalation. FT-IR and 29Si MAS NMR results indicated that dodecylamine modification did not result in obvious changes in the MMT lattice structure. The XRD results showed that the protonated dodecylamine has been embedded and intercalated into the MMT interlayers, whereas Nafion was not. Elemental analysis results also suggested that some dodecylamine was adsorbed on the surface of MMT. 1H-13C HETCOR 2D NMR experiment clearly indicated that strong electrostatic interactions were present between the NH+3 group of dodecylamine and the fluorine-containing groups (CF3, OCF2, and SCF2) of Nafion resin. Such electrostatic interactions are probably the major contributors for the improved thermal stability of the resultant composite materials. PMID:17382953

  6. GFT projection NMR spectroscopy for proteins in the solid state

    PubMed Central

    Franks, W. Trent; Atreya, Hanudatta S.; Szyperski, Thomas

    2011-01-01

    Recording of four-dimensional (4D) spectra for proteins in the solid state has opened new avenues to obtain virtually complete resonance assignments and three-dimensional (3D) structures of proteins. As in solution state NMR, the sampling of three indirect dimensions leads per se to long minimal measurement time. Furthermore, artifact suppression in solid state NMR relies primarily on radio-frequency pulse phase cycling. For an n-step phase cycle, the minimal measurement times of both 3D and 4D spectra are increased n times. To tackle the associated ‘sampling problem’ and to avoid sampling limited data acquisition, solid state G-Matrix Fourier Transform (SS GFT) projection NMR is introduced to rapidly acquire 3D and 4D spectral information. Specifically, (4,3)D (HA)CANCOCX and (3,2)D (HACA)NCOCX were implemented and recorded for the 6 kDa protein GB1 within about 10% of the time required for acquiring the conventional congeners with the same maximal evolution times and spectral widths in the indirect dimensions. Spectral analysis was complemented by comparative analysis of expected spectral congestion in conventional and GFT NMR experiments, demonstrating that high spectral resolution of the GFT NMR experiments enables one to efficiently obtain nearly complete resonance assignments even for large proteins. PMID:21052779

  7. Simulations of noble gases adsorbed on graphene

    NASA Astrophysics Data System (ADS)

    Maiga, Sidi; Gatica, Silvina

    2014-03-01

    We present results of Grand Canonical Monte Carlo simulations of adsorption of Kr, Ar and Xe on a suspended graphene sheet. We compute the adsorbate-adsorbate interaction by a Lennard-Jones potential. We adopt a hybrid model for the graphene-adsorbate force; in the hybrid model, the potential interaction with the nearest carbon atoms (within a distance rnn) is computed with an atomistic pair potential Ua; for the atoms at r>rnn, we compute the interaction energy as a continuous integration over a carbon uniform sheet with the density of graphene. For the atomistic potential Ua, we assume the anisotropic LJ potential adapted from the graphite-He interaction proposed by Cole et.al. This interaction includes the anisotropy of the C atoms on graphene, which originates in the anisotropic π-bonds. The adsorption isotherms, energy and structure of the layer are obtained and compared with experimental results. We also compare with the adsorption on graphite and carbon nanotubes. This research was supported by NSF/PRDM (Howard University) and NSF (DMR 1006010).

  8. Orbital tomography for highly symmetric adsorbate systems

    NASA Astrophysics Data System (ADS)

    Stadtmüller, B.; Willenbockel, M.; Reinisch, E. M.; Ules, T.; Bocquet, F. C.; Soubatch, S.; Puschnig, P.; Koller, G.; Ramsey, M. G.; Tautz, F. S.; Kumpf, C.

    2012-10-01

    Orbital tomography is a new and very powerful tool to analyze the angular distribution of a photoemission spectroscopy experiment. It was successfully used for organic adsorbate systems to identify (and consequently deconvolute) the contributions of specific molecular orbitals to the photoemission data. The technique was so far limited to surfaces with low symmetry like fcc(110) oriented surfaces, owing to the small number of rotational domains that occur on such surfaces. In this letter we overcome this limitation and present an orbital tomography study of a 3,4,9,10-perylene-tetra-carboxylic-dianhydride (PTCDA) monolayer film adsorbed on Ag(111). Although this system exhibits twelve differently oriented molecules, the angular resolved photoemission data still allow a meaningful analysis of the different local density of states and reveal different electronic structures for symmetrically inequivalent molecules. We also discuss the precision of the orbital tomography technique in terms of counting statistics and linear regression fitting algorithm. Our results demonstrate that orbital tomography is not limited to low-symmetry surfaces, a finding which makes a broad field of complex adsorbate systems accessible to this powerful technique.

  9. Characterization of zeolite structure and fluorocarbon reactivity using solid state NMR and x-ray powder diffraction

    NASA Astrophysics Data System (ADS)

    Ciraolo, Michael Frank

    The research presented in this thesis involves a combination of techniques used to study the structure and interactions zeolites adsorbed with fluorocarbons. This research is specifically aimed at understanding the processes of adsorption, binding, and reactivity of fluorocarbons on cation exchanged faujasite type zeolites. The solid state ion exchange process has also been studied since it is one way to obtain materials with higher exchange levels, which has been shown to effect adsorption and catalytic activity. To improve the understanding of the adsorption and separation processes a time resolved in-situ synchrotron x-ray powder diffraction study has been undertaken. Since faujasite type zeolites have been found to be effective in separating mixtures of HFC-134 (CF2HCF2H) and HFC-134a (CFH2CF3) isomers, the adsorption of these fluorocarbons on NaY have been studied. It has been shown that both the extent of loading and the kinetics of the sorption process in molecular sieves can be followed using this technique. A model for the binding of hydrochlorofluorocarbon (HCFC) 124a (CF 2HCF2Cl) adsorbed on NaX at 100K has been determined using a combination x-ray and neutron powder diffraction and solid state NMR. Using Rietveld refinement of the diffraction data, the HCFC molecule was found localized in the zeolite cavities bound on either end by sodium cations in the SII and SIII' positions. The model is consistent with hydrogen bonding between the proton of the HCFC and the framework oxygen. The NMR results further confirm the model and are consistent with Na-F binding and HCFC-framework interactions. Solid-state MAS NMR, synchrotron X-ray powder diffraction and a mass spectrometer and gas chromatograph catalysis system have been used to study the reactivity of HCFC-124a (CF2HCF2Cl) on NaX, Zn 2+-exchanged NaX (ZnX) and Rb+-exchanged NaX (RbX). We have chosen to study HCFC-124a (CF2HCF2Cl) since HCFC-124a can undergo both dehydrofluorination and dehydrochlorination

  10. Pillared Interlayered Clays as Adsorbents of Gases and Vapors

    NASA Astrophysics Data System (ADS)

    Pires, J.; Pinto, M. L.

    This chapter reviews recent works where porous materials prepared from clays, particularly pillared interlayered clays (PILCs), were studied as gas phase adsorbents. It also includes the cases which used the adsorption of gases and vapors for the nanotextural characterization of the materials, other than the usual low temperature nitrogen adsorption. This is, for instance, the case of the adsorption of molecules of volatile organic compounds (VOCs), with various dimensions and shapes, which can be used as probe molecules for the characterization of the porosity or concerning the topic of the VOCs abatement. A similar situation occurs with water adsorption, whose results can be informative not only on the desiccant properties of the materials but also on their surface chemistry. A more recent line of studies of adsorption by materials prepared from clays, namely, the hydrocarbon purification from natural gas or biogas, was also addressed.

  11. Compact orthogonal NMR field sensor

    DOEpatents

    Gerald, II, Rex E.; Rathke, Jerome W.

    2009-02-03

    A Compact Orthogonal Field Sensor for emitting two orthogonal electro-magnetic fields in a common space. More particularly, a replacement inductor for existing NMR (Nuclear Magnetic Resonance) sensors to allow for NMR imaging. The Compact Orthogonal Field Sensor has a conductive coil and a central conductor electrically connected in series. The central conductor is at least partially surrounded by the coil. The coil and central conductor are electrically or electro-magnetically connected to a device having a means for producing or inducing a current through the coil and central conductor. The Compact Orthogonal Field Sensor can be used in NMR imaging applications to determine the position and the associated NMR spectrum of a sample within the electro-magnetic field of the central conductor.

  12. Integrative NMR for biomolecular research.

    PubMed

    Lee, Woonghee; Cornilescu, Gabriel; Dashti, Hesam; Eghbalnia, Hamid R; Tonelli, Marco; Westler, William M; Butcher, Samuel E; Henzler-Wildman, Katherine A; Markley, John L

    2016-04-01

    NMR spectroscopy is a powerful technique for determining structural and functional features of biomolecules in physiological solution as well as for observing their intermolecular interactions in real-time. However, complex steps associated with its practice have made the approach daunting for non-specialists. We introduce an NMR platform that makes biomolecular NMR spectroscopy much more accessible by integrating tools, databases, web services, and video tutorials that can be launched by simple installation of NMRFAM software packages or using a cross-platform virtual machine that can be run on any standard laptop or desktop computer. The software package can be downloaded freely from the NMRFAM software download page ( http://pine.nmrfam.wisc.edu/download_packages.html ), and detailed instructions are available from the Integrative NMR Video Tutorial page ( http://pine.nmrfam.wisc.edu/integrative.html ). PMID:27023095

  13. Polarization transfer NMR imaging

    DOEpatents

    Sillerud, Laurel O.; van Hulsteyn, David B.

    1990-01-01

    A nuclear magnetic resonance (NMR) image is obtained with spatial information modulated by chemical information. The modulation is obtained through polarization transfer from a first element representing the desired chemical, or functional, information, which is covalently bonded and spin-spin coupled with a second element effective to provide the imaging data. First and second rf pulses are provided at first and second frequencies for exciting the imaging and functional elements, with imaging gradients applied therebetween to spatially separate the nuclei response for imaging. The second rf pulse is applied at a time after the first pulse which is the inverse of the spin coupling constant to select the transfer element nuclei which are spin coupled to the functional element nuclei for imaging. In a particular application, compounds such as glucose, lactate, or lactose, can be labeled with .sup.13 C and metabolic processes involving the compounds can be imaged with the sensitivity of .sup.1 H and the selectivity of .sup.13 C.

  14. Multispectral Analysis of NMR Imagery

    NASA Technical Reports Server (NTRS)

    Butterfield, R. L.; Vannier, M. W. And Associates; Jordan, D.

    1985-01-01

    Conference paper discusses initial efforts to adapt multispectral satellite-image analysis to nuclear magnetic resonance (NMR) scans of human body. Flexibility of these techniques makes it possible to present NMR data in variety of formats, including pseudocolor composite images of pathological internal features. Techniques do not have to be greatly modified from form in which used to produce satellite maps of such Earth features as water, rock, or foliage.

  15. NMR characterization of thin films

    DOEpatents

    Gerald II, Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

    2010-06-15

    A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

  16. NMR characterization of thin films

    DOEpatents

    Gerald, II, Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

    2008-11-25

    A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

  17. Automated protein NMR resonance assignments.

    PubMed

    Wan, Xiang; Xu, Dong; Slupsky, Carolyn M; Lin, Guohui

    2003-01-01

    NMR resonance peak assignment is one of the key steps in solving an NMR protein structure. The assignment process links resonance peaks to individual residues of the target protein sequence, providing the prerequisite for establishing intra- and inter-residue spatial relationships between atoms. The assignment process is tedious and time-consuming, which could take many weeks. Though there exist a number of computer programs to assist the assignment process, many NMR labs are still doing the assignments manually to ensure quality. This paper presents (1) a new scoring system for mapping spin systems to residues, (2) an automated adjacency information extraction procedure from NMR spectra, and (3) a very fast assignment algorithm based on our previous proposed greedy filtering method and a maximum matching algorithm to automate the assignment process. The computational tests on 70 instances of (pseudo) experimental NMR data of 14 proteins demonstrate that the new score scheme has much better discerning power with the aid of adjacency information between spin systems simulated across various NMR spectra. Typically, with automated extraction of adjacency information, our method achieves nearly complete assignments for most of the proteins. The experiment shows very promising perspective that the fast automated assignment algorithm together with the new score scheme and automated adjacency extraction may be ready for practical use. PMID:16452794

  18. NMR Relaxation and Petrophysical Properties

    NASA Astrophysics Data System (ADS)

    Fleury, Marc

    2011-03-01

    NMR relaxation is routinely used in the field of geosciences to give basic petrophysical properties such as porosity, pore size distribution, saturation etc. In this tutorial, we focus on the pore size distribution deduced from NMR. We recall the basic principle used in the interpretation of the NMR signal and compare the results with other standard petrophysical techniques such as mercury pore size distribution, BET specific surface measurements, thin section visualizations. The NMR pore size distribution is a unique information available on water saturated porous media and can give similar results as MICP in certain situations. The scaling of NMR relaxation time distribution (s) into pore sizes (μm) requires the knowledge of the surface relaxivity (μm/s) and we recommend using specific surface measurements as an independent determination of solid surface areas. With usual surface relaxivities, the NMR technique can explore length-scales starting from nano-meters and ending around 100 μm. Finally, we will introduce briefly recent techniques sensitive to the pore to pore diffusional exchange, providing new information on the connectivity of the pore network, but showing another possibility of discrepancy in the determination of pore size distribution with standard techniques.

  19. On the solid-state NMR spectra of naproxen

    NASA Astrophysics Data System (ADS)

    Czernek, Jiří

    2015-01-01

    Two previous measurements of the 13C and 1H NMR isotropic chemical shifts in crystalline naproxen, which is an important pharmaceutical compound, are confronted with the results obtained from several theoretical approaches capable of the proper treatment of solid-phase effects. In the underlying geometrical optimizations, two crystal structures are considered. The agreement between the data sets is quantified, including an evaluation of the similarity between the experimental solid-state NMR spectra. The 13C-1H heteronuclear correlations are analyzed, and their various assignments are discussed employing the statistical treatment of the differences between the measured and theoretical isotropic chemical shifts.

  20. Radiation-induced reactions of amino acids adsorbed on solid surfaces

    NASA Astrophysics Data System (ADS)

    López-Esquivel Kranksith, L.; Negrón-Mendoza, A.; Mosqueira, F. G.; Ramos-Bernal, Sergio

    2010-07-01

    The purpose of this work is to study the adsorption of compounds such as amino acids on clays and carbon nanotubes (CNTs) as a possible phase in the chemical evolution that may have occurred on the primitive Earth or in extraterrestrial environments. We further study the behavior of amino acids adsorbed on these solid surfaces at different conditions of pH and levels of irradiation, simulating a high-radiation field at early Earth conditions. The relevance of this work is to explain the possible contribution of solids (clays and CNTs) as promoters of polymerization and as shields for the adsorbed organic compounds against external sources of energy. To this end, tryptophan, aspartic acid, and glutamic acid were adsorbed on fixed amounts of solid surfaces and were irradiated by a 60Co source for different periods of time at fixed dose rates. After irradiation, the amino acids were extracted from the solid and analyzed with UV and IR spectroscopes and high-performance liquid chromatography. The most efficient surface for adsorption of amino acids was clay, followed by CNTs. Studies of the gamma irradiation of amino acids adsorbed on clay (in the solid phase) show a low yield of recovery of the amino acid.

  1. 13C NMR of methane in an AlPO4-11 molecular sieve: Exchange effects and shielding anisotropy

    NASA Astrophysics Data System (ADS)

    Koskela, Tuomas; Ylihautala, Mika; Jokisaari, Jukka; Vaara, Juha

    1998-12-01

    13C NMR spectra of 13CH4 in an AlPO4-11 molecular sieve reveal exchange effects between adsorbed and nonadsorbed methane gas. An application of pulsed field gradients is introduced to decrease nonadsorbed and exchanging gas signals in order to extract the chemical shift anisotropy line shape of the adsorbed gas. The resulting 13C shielding anisotropy of methane is compared to existing value for methane in related SAPO-11 material. Less anisotropic shielding is observed in AlPO4-11, most likely due to the lack of charge-compensating cations.

  2. NMR solvent peak suppression by nonlinear excitation

    NASA Astrophysics Data System (ADS)

    Levitt, Malcolm H.

    1988-03-01

    Most existing NMR solvent peak suppression sequences provide a satisfactory dependence of the intensity of excited signals on frequency but poor phase characteristics. In practice this leads to spectral distortions which generally become more severe as the frequency selectivity of the sequence is increased. However, it is shown that by working well outside the linear response regime, excitation schemes which combine high frequency selectivity with good phase properties may be devised. Sequences of six rectangular radio-frequency pulses were discovered using a combination of coherent averaging theory to treat the near-resonant behavior and numerical simulation further from resonance. Extensive use of symmetry greatly simplifies both the coherent averaging calculations and the numerical simulations. The new pulse sequences have been given the acronym NERO (nonlinear excitation rejecting on-resonance). Experimental spectra of an enzyme in dilute aqueous solution are shown.

  3. Detecting Adsorbed Sulfate and Phosphate on Nanophase Weathering Products on Mars

    NASA Astrophysics Data System (ADS)

    Rampe, E. B.; Morris, R. V.

    2012-12-01

    Characterizing the mineralogy and chemistry of aqueous alteration phases on the martian surface is essential for understanding past aqueous processes because the types of secondary phases present and their chemical compositions tell us about the environments in which they formed. Orbital mid-infrared data and in-situ mineralogical and chemical data from the martian surface indicate that Si/Al- and Fe-bearing nanophase weathering products are widespread, including allophane and nanophase ferric oxide (npOx), which includes any combination of superparamagnetic hematite and goethite, ferrihydrite, schwertmannite, akaganeite, iddingsite, and palagonite (altered basaltic glass) [Morris et al., 2006; Michalski et al., 2006; Rampe et al., in press]. These weathering products have larger surface areas and variable surface charge and can adsorb anions and cations onto their surfaces. Some anions, such as sulfate and phosphate, specifically chemically adsorb onto mineral/mineraloid surfaces so that these complexes are covalently bonded and form ligands. Nanophase weathering products on Earth can specifically adsorb up to a few weight percent to a few tens of weight percent phosphate and sulfate, respectively [Parfitt and Smart, 1978; Jara et al., 2006]. Phosphate and sulfate have been identified in martian rocks and soils in abundances of up to ~5 wt.% and ~30 wt.%, respectively [Gellert et al., 2006; Ming et al., 2006], and it has been suggested that phosphate and sulfate ions may be adsorbed on nanophase weathering products on the martian surface [Greenwood and Blake, 2006; Morris et al., 2006]. What is relatively unknown is how to use in-situ and orbital instruments on Mars to determine if these ions are present as discrete minerals or adsorbed onto the surfaces of weathering products. We adsorbed phosphate and sulfate onto allophane surfaces in the laboratory. Here, we present laboratory measurements of phosphate- and sulfate-adsorbed allophane to compare to in

  4. NMR study of a 17O enriched LaMnO3 stoichiometric crystal

    NASA Astrophysics Data System (ADS)

    Pinsard-Gaudart, L.; Trokiner, A.; Verkhovskii, S.; Gerashenko, A.; Dragoe, N.

    2011-12-01

    We present the synthesis and the NMR characterization of a 17O enriched LaMnO 3 crystalline sample. We checked that it is single phase and, more important, stoichiometric in oxygen. Its 17O enrichment estimated by NMR is about 5.5%. These first 17O NMR results obtained at T=415 K in an undoped parent LaMnO 3 manganite demonstrate that the two oxygen sites of the structure probe very different Mn spin correlations in the paramagnetic orbital ordered phase. This work opens the way to study experimentally the interactions responsible for the orbital order.

  5. Medical applications of NMR imaging and NMR spectroscopy with stable isotopes. Summary

    SciTech Connect

    Matwiyoff, N.A.

    1983-01-01

    The current status of NMR imaging and NMR spectroscopy are summarized. For the most part examples from the March 1983 Puerto Rico symposium are used to illustrate the utility of NMR in medicine. 18 refs., 5 figs.

  6. jsNMR: an embedded platform-independent NMR spectrum viewer.

    PubMed

    Vosegaard, Thomas

    2015-04-01

    jsNMR is a lightweight NMR spectrum viewer written in JavaScript/HyperText Markup Language (HTML), which provides a cross-platform spectrum visualizer that runs on all computer architectures including mobile devices. Experimental (and simulated) datasets are easily opened in jsNMR by (i) drag and drop on a jsNMR browser window, (ii) by preparing a jsNMR file from the jsNMR web site, or (iii) by mailing the raw data to the jsNMR web portal. jsNMR embeds the original data in the HTML file, so a jsNMR file is a self-transforming dataset that may be exported to various formats, e.g. comma-separated values. The main applications of jsNMR are to provide easy access to NMR data without the need for dedicated software installed and to provide the possibility to visualize NMR spectra on web sites. PMID:25641013

  7. NMR Imaging: Instrumentation and Techniques

    NASA Astrophysics Data System (ADS)

    Tingle, Jeremy Mark

    Available from UMI in association with The British Library. This thesis presents three original contributions to the field of Nuclear Magnetic Resonance (NMR): the experimental framework and analysis for the measurement of a new imaging parameter to describe perfusion; the measurement and analysis of magnetic field inhomogeneity and a practical correction system for their reduction; a novel system for the synchronous control of NMR experiments based on the microprogrammed concept. The thesis begins with an introduction to the theory of NMR. The application of NMR to imaging is also introduced with emphasis on the techniques which developed into those in common use today. Inaccurate determination of the traditional NMR parameters (T_1 and T_2 and the molecular diffusion coefficient) can be caused by non-diffusive fluid movement within the sample. The experimental basis for determining a new imaging parameter --the Perfusion coefficient--is presented. This provides a measure of forced isotropic fluid motion through an organ or tissue. The instrumentation required for conducting NMR experiments is described in order to introduce the contribution made in this area during this research: A sequence controller. The controller is based on the concept of microprogramming and enables completely synchronous output of 128 bits of data. The software for the generation and storage of control data and the regulation of the data to provide experimental control is microcomputer based. It affords precise and accurate regulation of the magnetic field gradients, the rf synthesizer and the spectrometer for spectroscopic and imaging applications. Fundamental to the science of NMR is the presence of a magnetic field. A detailed study of the analysis of magnetic field inhomogeneity in terms of spherical harmonics is presented. The field of a whole body imaging system with poor inhomogeneity was measured and analyzed to determine and describe the components of the inhomogeneity. Finally a

  8. Conformational properties of an adsorbed charged polymer.

    PubMed

    Cheng, Chi-Ho; Lai, Pik-Yin

    2005-06-01

    The behavior of a strongly charged polymer adsorbed on an oppositely charged surface of a low-dielectric constant is formulated by the functional integral method. By separating the translational, conformational, and fluctuational degrees of freedom, the scaling behaviors for both the height of the polymer and the thickness of the diffusion layer are determined. Unlike the results predicted by scaling theory, we identified the continuous crossover from the weak compression to the compression regime. All the analytical results are found to be consistent with Monte Carlo simulations. Finally, an alternative (operational) definition of a charged polymer adsorption is proposed. PMID:16089715

  9. Recovery of Technetium Adsorbed on Charcoal

    SciTech Connect

    Engelmann, Mark D.; Metz, Lori A.; Ballou, Nathan E.

    2006-05-01

    Two methods capable of near complete recovery of technetium adsorbed on charcoal are presented. The first involves liquid extraction of the technetium from the charcoal by hot 4M nitric acid. An average recovery of 98% (n=3) is obtained after three rounds of extraction. The second method involves dry ashing with air in a quartz combustion tube at 400-450 C. This method yields an average recovery of 96% (n=5). Other thermal methods were attempted, but resulted in reduced recovery and incomplete material balance

  10. Lead removal with adsorbing colloid flotation

    SciTech Connect

    Thackston, E.L.; Wilson, D.J.; Hanson, J.S.; Miller, D.L. Jr.

    1980-02-01

    A process that removes lead from industrial waste by adsorbing colloid foam flotation has been designed and demonstrated. A system of ferric chloride and sodium lauryl sulfate, both relatively inexpensive chemicals, gave good performance with optimum dosages of sodium lauryl sulfate at 40 mg/l and trivalent iron at 150 mg/l. With optimum chemical and hydraulic conditions, the pilot plant was able to produce effluents with lead concentrations of less than 0.5 mg/l. The process may be especially attractive where space for heavy metals removal equipment is extremely limited.

  11. NMR study in sodium-hydrogen-C{sub 60} superconductor

    SciTech Connect

    Ogata, H.; Miyajima, S.; Imaeda, K.; Inokuchi, H.

    1998-12-31

    {sup 23}Na and {sup 1}H NMR studies have been carried out for a Na{sub x}H{sub y}C{sub 60} superconductor. The peak position of the {sup 23}Na NMR spectrum exhibits discontinuous upfield shift of 30 ppm at about 250 K, indicates a first order phase transition. From the line shape of the {sup 23}Na spectrum obtained at 7 K, the quadrupole coupling constant tensor is evaluated to be {vert_bar}e{sup 2}Qq/h{vert_bar} = 3.7 MHz with the asymmetry parameter {eta} = 0.95. The {sup 1}H NMR spectrum suggests an anionic hydrogen state with weakly delocalized nature.

  12. NMR characteristics in noncentrosymmetric Mo3Al2C

    NASA Astrophysics Data System (ADS)

    Kuo, C. N.; Liu, H. F.; Lue, C. S.

    2012-02-01

    We present an extensive study of the noncentrosymmetric superconductor Mo3Al2C using 27Al nuclear magnetic resonance (NMR) spectroscopy. The NMR line shapes, Knight shifts, as well as spin-lattice relaxation rates in both superconducting and normal states have been identified. In the superconducting phase, the results of the Knight shift and relaxation rate signify the existence of finite density of states, attributed to the strong antisymmetric spin-orbital coupling effect enhanced by intrinsic defects. In the normal state, peculiar changes such as the broadening of the NMR linewidth and the distinct drop of the Knight shift were discerned across a characteristic temperature of T*≃196 K. Moreover, the magnitude of 1/T1T decreases markedly and develops pseudogaplike behavior below T*. We associated these anomalous features with distortions near the Al sites toward a lower symmetric structural environment, leading to the modification of electronic structures around Fermi surfaces.

  13. A new method for analysis of reactive adsorbed intermediates: Bismuth postdosing in thermal desorption mass spectroscopy

    NASA Astrophysics Data System (ADS)

    Campbell, Charles T.; Rodriguez, J. A.; Henn, F. C.; Campbell, J. M.; Dalton, P. J.; Seimanides, S. G.

    1988-05-01

    A new method which should have relatively general applicability for the identification and quantitative analysis of reactive adsorbed molecular intermediates in surface reactions will be described, and the first examples of its application will be presented. When a reactive intermediate is generated on a surface, it often has a tendency to dissociate before desorbing. Since dissociation generally requires additional free sites on the surface, dissociation can be suppressed and desorption correspondingly enhanced if the free sites on the surface can be properly poisoned. We have found that bismuth adatoms are very good inert site blockers, which can be postdosed to the surface of a transition metal containing a reactive adsorbed hydrocarbon without destroying the hydrocarbon. Whereas in the absence of bismuth, the hydrocarbon would completely dehydrogenate during thermal desorption spectroscopy (TDS) and liberate only H2 into the gas phase, after bismuth postdosing the reactive hydrocarbon desorbs intact for mass spectral identification and quantitative analysis. This method has been used to prove that adsorbed benzene is the initial product of the dehydrogenation of cyclohexane on Pt(111) at ˜235 K. In the absence of bismuth, this benzene all dissociates during TDS to liberate only H2, leaving graphitic carbon residue on the surface. When one-third monolayer of Bi is postdosed at 110 K, the dehydrogenation pathway is sterically poisoned and the adsorbed benzene quantitatively desorbs during TDS, where it is unambiguously identified by mass spectroscopy. By briefly heating the reactive adsorbed intermediate to increasing temperatures prior to Bi deposition, the thermal stability limits of the intermediate and the kinetic parameters for its dissociation can be established. This is demonstrated for the dehydrogenation reaction of adsorbed cyclopentene on Pt(111). Bismuth postdosing in thermal desorption mass spectroscopy (BPTDS) should be a very useful but

  14. Thermodynamic investigation of trichloroethylene adsorption in water-saturated microporous adsorbents

    SciTech Connect

    Farrell, J.; Hauck, B.; Jones, M.

    1999-08-01

    Adsorption of trichloroethylene (TCE) in adsorbents containing hydrophilic and hydrophobic micropores was investigated in order to determine the mechanisms responsible for TCE adsorption on mineral solids. A high-pressure liquid chromatography method was used to measure TCE adsorption isotherms on three microporous adsorbents. Silica gel and zeolite type NaX were used as hydrophilic model adsorbents, and hexamethyldisilazane (HMDS)-treated silica gel was used as a model hydrophobic adsorbent. Batch uptake and desorption isotherms were also measured on the hydrophilic silica gel. Uptake of TCE by all three adsorbents was linear over the concentration range investigated. However, the silica gel desorption isotherm was highly nonlinear, as indicated by its Freundlich isotherm exponent of 0.58. Capillary phase separation into hydrophobic micropores was postulated as being responsible for the isotherm hysteresis. Supporting this hypothesis was the conformance of the TCE adsorption isotherm to Dubinin-Radushkevitch volume filling of micropores theory. The enthalpies for TCE adsorption on all three solids were determined by van't Hoff analysis of distribution coefficients measured over a temperature range from 5 to 90 C. The TCE adsorption enthalpies on the silica gel and HMDS silica gel were exothermic, but on the zeolite adsorption was endothermic. High exothermic adsorption enthalpies on the silica gel adsorbents indicated that TCE adsorption was occurring in hydrophobic micropores, and that adsorption on surfaces with large radii of curvature contributed only minimally to the total uptake. This indicates that the predominant mechanism for TCE adsorption on these mineral solids is not partitioning into the vicinal water layer.

  15. Surface photochemistry of adsorbed nitrate: the role of adsorbed water in the formation of reduced nitrogen species on α-Fe2O3 particle surfaces.

    PubMed

    Nanayakkara, Charith E; Jayaweera, Pradeep M; Rubasinghege, Gayan; Baltrusaitis, Jonas; Grassian, Vicki H

    2014-01-01

    The surface photochemistry of nitrate, formed from nitric acid adsorption, on hematite (α-Fe2O3) particle surfaces under different environmental conditions is investigated using X-ray photoelectron spectroscopy (XPS). Following exposure of α-Fe2O3 particle surfaces to gas-phase nitric acid, a peak in the N1s region is seen at 407.4 eV; this binding energy is indicative of adsorbed nitrate. Upon broadband irradiation with light (λ > 300 nm), the nitrate peak decreases in intensity as a result of a decrease in adsorbed nitrate on the surface. Concomitant with this decrease in the nitrate coverage, there is the appearance of two lower binding energy peaks in the N1s region at 401.7 and 400.3 eV, due to reduced nitrogen species. The formation as well as the stability of these reduced nitrogen species, identified as NO(-) and N(-), are further investigated as a function of water vapor pressure. Additionally, irradiation of adsorbed nitrate on α-Fe2O3 generates three nitrogen gas-phase products including NO2, NO, and N2O. As shown here, different environmental conditions of water vapor pressure and the presence of molecular oxygen greatly influence the relative photoproduct distribution from nitrate surface photochemistry. The atmospheric implications of these results are discussed. PMID:24299394

  16. Sensitization of a stray-field NMR to vibrations: A potential for MR elastometry with a portable NMR sensor

    NASA Astrophysics Data System (ADS)

    Mastikhin, Igor; Barnhill, Marie

    2014-11-01

    An NMR signal from a sample in a constant stray field of a portable NMR sensor is sensitized to vibrations. The CPMG sequence is synchronized to vibrations so that the constant gradient becomes an "effective" square-wave gradient, leading to the vibration-induced phase accumulation. The integrating nature of the spot measurement, combined with the phase distribution due to a non-uniform gradient and/or a wave field, leads to a destructive interference, the drop in the signal intensity and changes in the echo train shape. Vibrations with amplitudes as small as 140 nm were reliably detected with the permanent gradient of 12.4 T/m. The signal intensity depends on the phase offset between the vibrations and the pulse sequence. This approach opens the way for performing elastometry and micro-rheology measurements with portable NMR devices beyond the walls of a laboratory. Even without synchronization, if a vibration frequency is comparable to 1/2TE of the CPMG sequence, the signal can be severely affected, making it important for potential industrial applications of stray-field NMR.

  17. The relationship between reorientational molecular motions and phase transitions in [Mg(H{sub 2}O){sub 6}](BF{sub 4}){sub 2}, studied with the use of {sup 1}H and {sup 19}F NMR and FT-MIR

    SciTech Connect

    Mikuli, Edward Hetmańczyk, Joanna; Grad, Bartłomiej; Kozak, Asja; Wąsicki, Jan W.; Bilski, Paweł; Hołderna-Natkaniec, Krystyna; Medycki, Wojciech

    2015-02-14

    A {sup 1}H and {sup 19}F nuclear magnetic resonance study of [Mg(H{sub 2}O){sub 6}](BF{sub 4}){sub 2} has confirmed the existence of two phase transitions at T{sub c1} ≈ 257 K and T{sub c2} ≈ 142 K, detected earlier by the DSC method. These transitions were reflected by changes in the temperature dependences of both proton and fluorine of second moments M{sub 2}{sup H} and M{sub 2}{sup F} and of spin-lattice relaxation times T{sub 1}{sup H} and T{sub 1}{sup F}. The study revealed anisotropic reorientations of whole [Mg(H{sub 2}O){sub 6}]{sup 2+} cations, reorientations by 180° jumps of H{sub 2}O ligands, and aniso- and isotropic reorientations of BF{sub 4}{sup −} anions. The activation parameters for these motions were obtained. It was found that the phase transition at T{sub c1} is associated with the reorientation of the cation as a whole unit around the C{sub 3} axis and that at T{sub c2} with isotropic reorientation of the BF{sub 4}{sup −} anions. The temperature dependence of the full width at half maximum value of the infrared band of ρ{sub t}(H{sub 2}O) mode (at ∼596 cm{sup −1}) indicated that in phases I and II, all H{sub 2}O ligands in [Mg(H{sub 2}O){sub 6}]{sup 2+} perform fast reorientational motions (180° jumps) with a mean value of activation energy equal to ca 10 kJ mole{sup −1}, what is fully consistent with NMR results. The phase transition at T{sub c1} is associated with a sudden change of speed of fast (τ{sub R} ≈ 10{sup −12} s) reorientational motions of H{sub 2}O ligands. Below T{sub c2} (in phase III), the reorientations of certain part of the H{sub 2}O ligands significantly slow down, while others continue their fast reorientation with an activation energy of ca 2 kJ mole{sup −1}. This fast reorientation cannot be evidenced in NMR relaxation experiments. Splitting of certain IR bands connected with H{sub 2}O ligands at the observed phase transitions suggests a reduction of the symmetry of the octahedral [Mg(H{sub 2}O

  18. Sensitive and robust electrophoretic NMR: Instrumentation and experiments

    NASA Astrophysics Data System (ADS)

    Hallberg, Fredrik; Furó, István; Yushmanov, Pavel V.; Stilbs, Peter

    2008-05-01

    Although simple as a concept, electrophoretic NMR (eNMR) has so far failed to find wider application. Problems encountered are mainly due to disturbing and partly irreproducible convection-like bulk flow effects from both electro-osmosis and thermal convection. Additionally, bubble formation at the electrodes and rf noise pickup has constrained the typical sample geometry to U-tube-like arrangements with a small filling factor and a low resulting NMR sensitivity. Furthermore, the sign of the electrophoretic mobility cancels out in U-tube geometries. We present here a new electrophoretic sample cell based on a vertically placed conventional NMR sample tube with bubble-suppressing palladium metal as electrode material. A suitable radiofrequency filter design prevents noise pickup by the NMR sample coil from the high-voltage leads which extend into the sensitive sample volume. Hence, the obtained signal-to-noise ratio of this cell is one order of magnitude higher than that of our previous U-tube cells. Permitted by the retention of the sign of the displacement-related signal phase in the new cell design, an experimental approach is described where bulk flow effects by electro-osmosis and/or thermal convection are compensated through parallel monitoring of a reference signal from a non-charged species in the sample. This approach, together with a CPMG-like pulse train scheme provides a superior first-order cancellation of non-electrophoretic bulk flow effects.

  19. Theory of mirrored time domain sampling for NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Ghosh, Arindam; Wu, Yibing; He, Yunfen; Szyperski, Thomas

    2011-12-01

    A generalized theory is presented for novel mirrored hypercomplex time domain sampling (MHS) of NMR spectra. It is the salient new feature of MHS that two interferograms are acquired with different directionality of time evolution, that is, one is sampled forward from time t = 0 to the maximal evolution time tmax, while the second is sampled backward from t = 0 to - tmax. The sampling can be accomplished in a (semi) constant time or non constant-time manner. Subsequently, the two interferograms are linearly combined to yield a complex time domain signal. The manifold of MHS schemes considered here is defined by arbitrary settings of sampling phases ('primary phase shifts') and amplitudes of the two interferograms. It is shown that, for any two given primary phase shifts, the addition theorems of trigonometric functions yield the unique linear combination required to form the complex signal. In the framework of clean absorption mode (CAM) acquisition of NMR spectra being devoid of residual dispersive signal components, 'secondary phase shifts' represent time domain phase errors which are to be eliminated. In contrast, such secondary phase shifts may be introduced by experimental design in order to encode additional NMR parameters, a new class of NMR experiments proposed here. For generalization, it is further considered that secondary phase shifts may depend on primary phase shifts and/or sampling directionality. In order to compare with MHS theory, a correspondingly generalized theory is derived for widely used hypercomplex ('States') sampling (HS). With generalized theory it is shown, first, that previously introduced 'canonical' schemes, characterized by primary phases being multiples of π/4, afford maximal intensity of the desired absorptive signals in the absence of secondary phase shifts, and second, how primary phases can be adjusted to maximize the signal intensity provided that the secondary phase shifts are known. Third, it is demonstrated that theory

  20. Theory of mirrored time domain sampling for NMR spectroscopy.

    PubMed

    Ghosh, Arindam; Wu, Yibing; He, Yunfen; Szyperski, Thomas

    2011-12-01

    A generalized theory is presented for novel mirrored hypercomplex time domain sampling (MHS) of NMR spectra. It is the salient new feature of MHS that two interferograms are acquired with different directionality of time evolution, that is, one is sampled forward from time t=0 to the maximal evolution time tmax, while the second is sampled backward from t=0 to -tmax. The sampling can be accomplished in a (semi) constant time or non constant-time manner. Subsequently, the two interferograms are linearly combined to yield a complex time domain signal. The manifold of MHS schemes considered here is defined by arbitrary settings of sampling phases ('primary phase shifts') and amplitudes of the two interferograms. It is shown that, for any two given primary phase shifts, the addition theorems of trigonometric functions yield the unique linear combination required to form the complex signal. In the framework of clean absorption mode (CAM) acquisition of NMR spectra being devoid of residual dispersive signal components, 'secondary phase shifts' represent time domain phase errors which are to be eliminated. In contrast, such secondary phase shifts may be introduced by experimental design in order to encode additional NMR parameters, a new class of NMR experiments proposed here. For generalization, it is further considered that secondary phase shifts may depend on primary phase shifts and/or sampling directionality. In order to compare with MHS theory, a correspondingly generalized theory is derived for widely used hypercomplex ('States') sampling (HS). With generalized theory it is shown, first, that previously introduced 'canonical' schemes, characterized by primary phases being multiples of π/4, afford maximal intensity of the desired absorptive signals in the absence of secondary phase shifts, and second, how primary phases can be adjusted to maximize the signal intensity provided that the secondary phase shifts are known. Third, it is demonstrated that theory enables

  1. NMR planar microcoil for microanalysis

    NASA Astrophysics Data System (ADS)

    Sorli, B.; Chateaux, J. F.; Quiquerez, L.; Bouchet-Fakri, L.; Briguet, A.; Morin, P.

    2006-11-01

    This article deals with the analysis of small sample volume by using a planar microcoil and a micromachined cavity. This microcoil is used as a nuclear magnetic resonance (NMR) radio frequency detection coil in order to perform in vitro NMR analysis of the sample introduced into the microcavity. It is a real challenging task to develop microsystem for NMR spectrum extraction for smaller and smaller sample volume. Moreover, it is advantageous that these microsystems could be integrated in a Micro Total Analysing System (μ -TAS) as an analysing tool. In this paper, NMR theory, description, fabrication process and electrical characterization of planar microcoils receiver are described. Results obtained on NMR microspectroscopy experiments have been performed on water and ethanol, using a 1 mm diameter planar coil. This microcoil is tuned and matched at 85.13 MHz which is the Larmor frequency of proton in a 2 T magnetic field. This paper has been presented at “3e colloque interdisciplinaire en instrumentation (C2I 2004)”, École Normale Supérieure de Cachan, 29 30 janvier 2004.

  2. Optimizing heterosurface adsorbent synthesis for liquid chromatography

    NASA Astrophysics Data System (ADS)

    Bogoslovskii, S. Yu.; Serdan, A. A.

    2016-03-01

    The structural and geometric parameters of a silica matrix (SM) for the synthesis of heterosurface adsorbents (HAs) are optimized. Modification is performed by shielding the external surfaces of alkyl-modified silica (AS) using human serum albumin and its subsequent crosslinking. The structural and geometric characteristics of the SM, AS, and HA are measured via low-temperature nitrogen adsorption. It is found that the structural characteristics of AS pores with diameters D < 6 nm do not change during HA synthesis, while the volume of pores with diameters of 6 nm < D < 9 nm shrinks slightly due to the adsorption of albumin in the pore orifices. It is established that the volume of pores with diameters D > 9 nm reduces significantly due to adsorption of albumin. It is concluded that silica gel with a maximum pore size distribution close to 5 nm and a minimal proportion of pores with D > 9 nm is optimal for HA synthesis; this allows us to achieve the greatest similarity between the chromatographic retention parameters for HA and AS. The suitability of the synthesized adsorbents for analyzing drugs in biological fluids through direct sample injection is confirmed by chromatography. It was found that the percentage of the protein fraction detected at the outlet of the chromatographic column is 98%.

  3. Nitric oxide releasing material adsorbs more fibrinogen.

    PubMed

    Lantvit, Sarah M; Barrett, Brittany J; Reynolds, Melissa M

    2013-11-01

    One mechanism of the failure of blood-contacting devices is clotting. Nitric oxide (NO) releasing materials are seen as a viable solution to the mediation of surface clotting by preventing platelet activation; however, NO's involvement in preventing clot formation extends beyond controlling platelet function. In this study, we evaluate NO's effect on factor XII (fibrinogen) adsorption and activation, which causes the initiation of the intrinsic arm of the coagulation cascade. This is done by utilizing a model plasticized poly(vinyl) chloride (PVC), N-diazeniumdiolate system and looking at the adsorption of fibrinogen, an important clotting protein, to these surfaces. The materials have been prepared in such a way to eliminate changes in surface properties between the control (plasticized PVC) and composite (NO-releasing) materials. This allows us to isolate NO release and determine the effect on the adsorption of fibrinogen, to the material surface. Surprisingly, it was found that an NO releasing material with a surface flux of 17.4 ± 0.5 × 10(-10) mol NO cm(-2) min(-1) showed a significant increase in the amount of fibrinogen adsorbed to the material surface compared to one with a flux of 13.0 ± 1.6 × 10(-10) mol NO cm(-2) min(-1) and the control (2334 ± 496, 226 ± 99, and 103 ±31% fibrinogen adsorbed of control, respectively). This study suggests that NO's role in controlling clotting is extended beyond platelet activation. PMID:23554300

  4. Adsorbents as antiendotoxin agents in experimental colitis.

    PubMed Central

    Gardiner, K R; Anderson, N H; McCaigue, M D; Erwin, P J; Halliday, M I; Rowlands, B J

    1993-01-01

    The intestinal mucosa protects the body from a large reservoir of intraluminal pathogenic bacteria and endotoxins. This mucosal barrier is disrupted by the inflammation and ulceration of inflammatory bowel disease and may permit the absorption of toxic bacterial products. Systemic endotoxaemia has been demonstrated in ulcerative colitis and Crohn's disease and correlates with the extent and activity of disease. In this study the efficacy of absorbents as antiendotoxin agents in a hapten induced rat model of colitis is investigated. Induction of colitis was associated with systemic endotoxaemia. Enteral administration of terra fullonica and kaolin, but not of charcoal, significantly reduced systemic endotoxaemia (terra fullonica 4.2 (1.40) pg/ml; kaolin 5.29 (1.86) pg/ml; charcoal 32.7 (16.6) pg/ml; water 39.8 (12.6) pg/ml). Data expressed as mean (SE). With increasing severity of colitis, there was a decreasing ability of adsorbent therapy (terra fullonica) to control systemic endotoxaemia. Enteral administration of adsorbents controls gut derived systemic endotoxaemia in experimental colitis in animals and may be a useful antiendotoxin treatment in patients with inflammatory bowel disease. PMID:8432452

  5. Block copolymer adsorbed layers on solids

    NASA Astrophysics Data System (ADS)

    Sen, Mani; Jiang, Naisheng; Gowd, Bhoje; Endoh, Maya; Koga, Tadanori

    Block copolymer thin films offer a simple and effective route to fabricate highly ordered periodic microdomain structures. The fundamental, yet unsolved question is whether these highly oriented microdomain structures persist even near an impenetrable solid wall. We here report the adsorbed structures of polystyrene-block-poly (4-vinylpyridine) (PS-block-P4VP, Mw = 41,000, PS (weight fraction =0.81) formed on planar silicon substrates. Perpendicularly aligned cylindrical microdomains were created by solvent vapor annealing (Gowd et al., Soft Matter, 2014, 10, 7753), and the adsorbed layer was derived by solvent leaching with chloroform, a good solvent for the polymers and thereafter characterized by using atomic force microscopy, scanning electron microscopy, grazing incidence small angle x-ray scattering, and x-ray reflectivity. The results showed that both PS and P4VP chains lie flat on the substrate, forming a microphase-separated structure (MSS) without long-range order. Moreover, a spin-coated PS-block-P4VP thin film annealed under vacuum at 190 °C showed similar MSS on the substrate, indicating the generality of the interfacial polymer structure. Details will be discussed in the presentation. NSF Grant No. CMMI-1332499.

  6. Mimetite Formation from Goethite-Adsorbed Ions.

    PubMed

    Kleszczewska-Zębala, Anna; Manecki, Maciej; Bajda, Tomasz; Rakovan, John; Borkiewicz, Olaf J

    2016-06-01

    Bioavailability of arsenic in contaminated soils and wastes can be reduced to insignificant levels by precipitation of mimetite Pb5(AsO4)3Cl. The objective of this study is to elucidate mechanisms of the reaction between solution containing lead ions and arsenates adsorbed on synthetic goethite (AsO4-goethite), or arsenate ions in the solution and goethite saturated with adsorbed Pb (Pb-goethite). These reactions, in the presence of Cl, result in rapid crystallization of mimetite. Formation of mimetite is faster than desorption of AsO4 but slower than desorption of Pb from the goethite surface. Slow desorption of arsenates from AsO4-goethite results in heterogeneous precipitation and formation of mimetite incrustation on goethite crystals. Desorption of lead from Pb-goethite is at least as fast as diffusion and advection of AsO4 and Cl in suspension allowing for homogeneous crystallization of mimetite in intergranular solution. Therefore, the mechanism of nucleation is primarily driven by the kinetics of constituent supply to the saturation front, rather than by the thermodynamics of nucleation. The products of the reactions are well documented using microscopy methods such as scanning electron microscopy, electron backscattered diffraction, X-ray diffraction, and Fourier transform infrared spectroscopy. PMID:27329315

  7. The persistence length of adsorbed dendronized polymers.

    PubMed

    Grebikova, Lucie; Kozhuharov, Svilen; Maroni, Plinio; Mikhaylov, Andrey; Dietler, Giovanni; Schlüter, A Dieter; Ullner, Magnus; Borkovec, Michal

    2016-07-21

    The persistence length of cationic dendronized polymers adsorbed onto oppositely charged substrates was studied by atomic force microscopy (AFM) and quantitative image analysis. One can find that a decrease in the ionic strength leads to an increase of the persistence length, but the nature of the substrate and of the generation of the side dendrons influence the persistence length substantially. The strongest effects as the ionic strength is being changed are observed for the fourth generation polymer adsorbed on mica, which is a hydrophilic and highly charged substrate. However, the observed dependence on the ionic strength is much weaker than the one predicted by the Odijk, Skolnik, and Fixman (OSF) theory for semi-flexible chains. Low-generation polymers show a variation with the ionic strength that resembles the one observed for simple and flexible polyelectrolytes in solution. For high-generation polymers, this dependence is weaker. Similar dependencies are found for silica and gold substrates. The observed behavior is probably caused by different extents of screening of the charged groups, which is modified by the polymer generation, and to a lesser extent, the nature of the substrate. For highly ordered pyrolytic graphite (HOPG), which is a hydrophobic and weakly charged substrate, the electrostatic contribution to the persistence length is much smaller. In the latter case, we suspect that specific interactions between the polymer and the substrate also play an important role. PMID:27353115

  8. Investigation of drug-porous adsorbent interactions in drug mixtures with selected porous adsorbents.

    PubMed

    Madieh, Shadi; Simone, Michael; Wilson, Wendy; Mehra, Dev; Augsburger, Larry

    2007-04-01

    The adsorption of drugs onto porous substrates may prove to be a convenient method by which to enhance the dissolution rate of certain poorly water-soluble drugs in body fluids. The purpose of this research is to provide a better understanding of the type of interactions occurring between drugs and certain pharmaceutically acceptable porous adsorbents that leads to enhanced drug dissolution rates. The interactions between ibuprofen (acidic drug), acetaminophen (acidic drug), dipyridamole (basic drug), and the porous adsorbents used (calcium silicate and silica gel) were investigated using differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and Fourier Transform infrared spectroscopy (FTIR). DSC and PXRD results indicated a significant loss of crystallinity of both ibuprofen and acetaminophen but not dipyridamole. In the case of ibuprofen, FTIR results indicated the ionization of the carboxylic group based on the shift in the FTIR carboxylic band. Dissolution of ibuprofen from its mixtures with porous adsorbents was found to be significantly higher compared to the neat drug, whereas dipyridamole dissolution from its mixtures with porous adsorbents was not significantly different from that of the neat drug. PMID:17221849

  9. Equilibrium molecular theory of two-dimensional adsorbate drops on surfaces of heterogeneous adsorbents

    NASA Astrophysics Data System (ADS)

    Tovbin, Yu. K.

    2016-08-01

    A molecular statistical theory for calculating the linear tension of small multicomponent droplets in two-dimensional adsorption systems is developed. The theory describes discrete distributions of molecules in space (on a scale comparable to molecular size) and continuous distributions of molecules (at short distances inside cells) in their translational and vibrational motions. Pair intermolecular interaction potentials (the Mie type potential) in several coordination spheres are considered. For simplicity, it is assumed that distinctions in the sizes of mixture components are slight and comparable to the sizes of adsorbent adsorption centers. Expressions for the pressure tensor components inside small droplets on the heterogeneous surface of an adsorbent are obtained, allowing calculations of the thermodynamic characteristics of a vapor-fluid interface, including linear tension. Problems in refining the molecular theory are discussed: describing the properties of small droplets using a coordination model of their structure, considering the effect an adsorbate has on the state of a near-surface adsorbent region, and the surface heterogeneity factor in the conditions for the formation of droplets.

  10. Influence of carboxylic ion-pairing reagents on retention of peptides in thin-layer chromatography systems with C18 silica-based adsorbents.

    PubMed

    Gwarda, Radosław Ł; Aletańska-Kozak, Monika; Klimek-Turek, Anna; Ziajko-Jankowska, Agnieszka; Matosiuk, Dariusz; Dzido, Tadeusz H

    2016-04-01

    One of the main problems related to chromatography of peptides concerns adverse interactions of their strong basic groups with free silanol groups of the silica based stationary phase. Influence of type and concentration of ion-pairing regents on peptide retention in reversed-phase high-performance liquid chromatography (RP-HPLC) systems has been discussed before. Here we present influence of these mobile phase additives on retention of some peptide standards in high-performance thin-layer chromatography (HPTLC) systems with C18 silica-based adsorbents. We prove, that due to different characteristic of adsorbents used in both techniques (RP HPLC and HPTLC), influence of ion-pairing reagents on retention of basic and/or amphoteric compounds also may be quite different. C18 silica-based HPTLC adsorbents provide more complex mechanism of retention and should be rather considered as mixed-mode adsorbents. PMID:26944833

  11. Improving NMR Structures of RNA.

    PubMed

    Bermejo, Guillermo A; Clore, G Marius; Schwieters, Charles D

    2016-05-01

    Here, we show that modern solution nuclear magnetic resonance (NMR) structures of RNA exhibit more steric clashes and conformational ambiguities than their crystallographic X-ray counterparts. To tackle these issues, we developed RNA-ff1, a new force field for structure calculation with Xplor-NIH. Using seven published NMR datasets, RNA-ff1 improves covalent geometry and MolProbity validation criteria for clashes and backbone conformation in most cases, relative to both the previous Xplor-NIH force field and the original structures associated with the experimental data. In addition, with smaller base-pair step rises in helical stems, RNA-ff1 structures enjoy more favorable base stacking. Finally, structural accuracy improves in the majority of cases, as supported by complete residual dipolar coupling cross-validation. Thus, the reported advances show great promise in bridging the quality gap that separates NMR and X-ray structures of RNA. PMID:27066747

  12. Elucidating the effects of adsorbent flexibility on fluid adsorption using simple models and flat-histogram sampling methods

    SciTech Connect

    Shen, Vincent K. Siderius, Daniel W.

    2014-06-28

    Using flat-histogram Monte Carlo methods, we investigate the adsorptive behavior of the square-well fluid in two simple slit-pore-like models intended to capture fundamental characteristics of flexible adsorbent materials. Both models require as input thermodynamic information about the flexible adsorbent material itself. An important component of this work involves formulating the flexible pore models in the appropriate thermodynamic (statistical mechanical) ensembles, namely, the osmotic ensemble and a variant of the grand-canonical ensemble. Two-dimensional probability distributions, which are calculated using flat-histogram methods, provide the information necessary to determine adsorption thermodynamics. For example, we are able to determine precisely adsorption isotherms, (equilibrium) phase transition conditions, limits of stability, and free energies for a number of different flexible adsorbent materials, distinguishable as different inputs into the models. While the models used in this work are relatively simple from a geometric perspective, they yield non-trivial adsorptive behavior, including adsorption-desorption hysteresis solely due to material flexibility and so-called “breathing” of the adsorbent. The observed effects can in turn be tied to the inherent properties of the bare adsorbent. Some of the effects are expected on physical grounds while others arise from a subtle balance of thermodynamic and mechanical driving forces. In addition, the computational strategy presented here can be easily applied to more complex models for flexible adsorbents.

  13. Fundamental characteristics of synthetic adsorbents intended for industrial chromatographic separations.

    PubMed

    Adachi, Tadashi; Isobe, Eiji

    2004-05-14

    With the aim of obtaining comprehensive information on the selection of synthetic adsorbents for industrial applications, effect of pore and chemical structure of industrial-grade synthetic adsorbents on adsorption capacity of several pharmaceutical compounds was investigated. For relatively low molecular mass compounds, such as cephalexin, berberine chloride and tetracycline hydrochloride, surface area per unit volume of polystyrenic adsorbents dominated the equilibrium adsorption capacity. On the contrary, effect of pore size of the polystyrenic adsorbents on the equilibrium adsorption capacity was observed for relatively high molecular mass compounds, such as rifampicin, Vitamin B12 and insulin. Polystyrenic adsorbent with high surface area and small pore size showed small adsorption capacity for relatively high molecular mass compounds, whereas polystyrenic adsorbent with relatively small surface area but with large pore size showed large adsorption capacity. Effect of chemical structure on the equilibrium adsorption capacity of several pharmaceutical compounds was also studied among polystyrenic, modified polystyrenic and polymethacrylic adsorbents. The modified polystyrenic adsorbent showed larger adsorption capacity for all compounds tested in this study due to enhanced hydrophobicity. The polymethacrylic adsorbent possessed high adsorption capacity for rifampicin and insulin, but it showed lower adsorption capacity for the other compounds studied. This result may be attributed to hydrogen bonding playing major role for the adsorption of compounds on polymethacrylic adsorbent. Furthermore, column adsorption experiments were operated to estimate the effect of pore characteristics of the polystyrenic adsorbents on dynamic adsorption behavior, and it is found that both surface area and pore size of the polystyrenic adsorbents significantly affect the dynamic adsorption capacity as well as flow rate. PMID:15139411

  14. A SENSITIVE NMR THERMOMETER FOR MULTINUCLEI FT NMR

    EPA Science Inventory

    A pernicious problem in multinuclei FT NMR is accurate measurement of sample temperature. This arises from several factors including widespread use of high-power decoupling, large sample tubes (with potentially large temperature gradients across the sample volume), and lack of su...

  15. Adsorption of copper cyanide on chemically active adsorbents

    SciTech Connect

    Lee, J.S.; Deorkar, N.V.; Tavlarides, L.L.

    1998-07-01

    An inorganic chemically active adsorbent (ICAA), SG(1)-TEPA (tetraethylenepentaamine)-propyl, is developed for removal, recovery, and recycling of copper cyanide from industrial waste streams. Equilibrium studies are executed to determine and model adsorption of the copper cyanide complex from aqueous solutions in a batch and packed column. It appears that adsorption is dependent on anionic copper cyanide species and the basicity of the ligand. Aqueous-phase equilibrium modeling shows that monovalent (Cu(CN){sub 2}{sup {minus}}), divalent (Cu(CN){sub 3}{sup 2{minus}}), and trivalent (Cu(CN){sub 4}{sup 3{minus}}) species of copper cyanide exist in the solution, depending on the pH and the concentration of total cyanide ions. Batch adsorption data are modeled using a modified multicomponent Langmuir isotherm which includes aqueous-phase speciation and basicity of the SG(1)-TEPA-propyl. This developed model is applied with a mass balance equation to describe the adsorption of copper cyanide complexes in a packed column.

  16. MULTIPLE-QUANTUM NMR IN SOLIDS

    SciTech Connect

    Yen, Y-S.

    1982-11-01

    Time domain multiple-quantum (MQ) nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for spectral simplification and for providing new information on molecular dynamics. In this thesis, applications of MQ NMR are presented and show distinctly the advantages of this method over the conventional single-quantum NMR. Chapter 1 introduces the spin Hamiltonians, the density matrix formalism and some basic concepts of MQ NMR spectroscopy. In chapter 2, {sup 14}N double-quantum coherence is observed with high sensitivity in isotropic solution, using only the magnetization of bound protons. Spin echoes are used to obtain the homogeneous double-quantum spectrum and to suppress a large H{sub 2}O solvent signal. Chapter 3 resolves the main difficulty in observing high MQ transitions in solids. Due to the profusion of spin transitions in a solid, individual lines are unresolved. Excitation and detection of high quantum transitions by normal schemes are thus difficult. To ensure that overlapping lines add constructively and thereby to enhance sensitivity, time-reversal pulse sequences are used to generate all lines in phase. Up to 22-quantum {sup 1}H absorption in solid adamantane is observed. A time dependence study shows an increase in spin correlations as the excitation time increased. In chapter 4, a statistical theory of MQ second moments is developed for coupled spins of spin I = 1/2. The model reveals that the ratio of the average dipolar coupling to the rms value largely determines the dependence of second moments on the number of quanta. The results of this model are checked against computer-calculated and experimental second moments, and show good agreement. A simple scheme is proposed in chapter 5 for sensitivity improvement in a MQ experiment. The scheme involves acquiring all of the signal energy available in the detection period by applying pulsed spinlocking and sampling between pulses. Using this technique on polycrystalline adamantane, a large

  17. Carbonaceous adsorbent regeneration and halocarbon displacement by hydrocarbon gases

    DOEpatents

    Senum, G.I.; Dietz, R.N.

    1994-04-05

    This invention describes a process for regeneration of halocarbon bearing carbonaceous adsorbents through which a carbonaceous adsorbent is contacted with hydrocarbon gases, preferably propane, butane and pentane at near room temperatures and at atmospheric pressure. As the hydrocarbon gases come in contact with the adsorbent, the hydrocarbons displace the halocarbons by physical adsorption. As a result of using this process, the halocarbon concentration and the hydrocarbon eluant is increased thereby allowing for an easier recovery of pure halocarbons. By using the process of this invention, carbonaceous adsorbents can be regenerated by an inexpensive process which also allows for subsequent re-use of the recovered halocarbons. 8 figures.

  18. Carbonaceous adsorbent regeneration and halocarbon displacement by hydrocarbon gases

    DOEpatents

    Senum, Gunnar I.; Dietz, Russell N.

    1994-01-01

    This invention describes a process for regeneration of halocarbon bearing carbonaceous adsorbents through which a carbonaceous adsorbent is contacted with hydrocarbon gases, preferably propane, butane and pentane at near room temperatures and at atmospheric pressure. As the hydrocarbon gases come in contact with the adsorbent, the hydrocarbons displace the halocarbons by physical adsorption. As a result of using this process, the halocarbon concentration and the hydrocarbon eluant is increased thereby allowing for an easier recovery of pure halocarbons. By using the process of this invention, carbonaceous adsorbents can be regenerated by an inexpensive process which also allows for subsequent re-use of the recovered halocarbons.

  19. Video STM Studies of Adsorbate Diffusion at Electrochemical Interfaces

    NASA Astrophysics Data System (ADS)

    Tansel, T.; Magnussen, O. M.

    2006-01-01

    Direct in situ studies of the surface diffusion of isolated adsorbates at an electrochemical interface by high-speed scanning tunneling microscopy (video STM) are presented for sulfide adsorbates on Cu(100) in HCl solution. As revealed by a quantitative statistical analysis, the adsorbate motion can be described by thermally activated hopping between neighboring adsorption sites with an activation energy that increases linearly with electrode potential by 0.50 eV per V. This can be explained by changes in the adsorbate dipole moment during the hopping process and contributions from coadsorbates.

  20. Swelling induced regeneration of TiO2-impregnated chitosan adsorbents under visible light.

    PubMed

    Yang, Limin; Jiang, Lei; Hu, Di; Yan, Qingyun; Wang, Zhi; Li, Sisi; Chen, Cheng; Xue, Qi

    2016-04-20

    Since only the molecules that are in direct contact with the TiO2 surface undergo photosensitization, it is challenging to regenerate the TiO2-impregnated chitosan (TIC) adsorbent beads under visible light. This study focused on the role of chitosan swelling properties. It was found that dye-loaded TIC adsorbent exhibited a pH-dependent swelling owing to protonation/deprotonation of free amino groups on chitosan chains. In the acidic medium (pH<6.0), the adsorbent underwent a 'smart' phase transition from a dry contracted state to a hydrated swollen state, and its physicochemical properties were also significantly changed, which eventually enabled the photosensitized oxidation of dye. This swelling induced regeneration was further confirmed by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The involvement of oxygen radical species (O2(-)/HOO and OH) was also confirmed with electron spin resonance (ESR) spectroscopy. Moreover, the adsorption effectiveness of TIC adsorbent was mostly recovered after six regeneration cycles. PMID:26876871

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

    SciTech Connect

    Kenny, T.W.

    1989-05-01

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

  2. From MDF and PB wastes to adsorbents for the removal of pollutants

    NASA Astrophysics Data System (ADS)

    Gomes, J. A. F. L.; Azaruja, B. A.; Mourão, P. A. M.

    2016-09-01

    The production of activated carbons in powder and monolith forms, by physical activation with CO2, with specific surface areas between 804 and 1469 m2 g-1, porous volume between 0.33 and 0.59 cm3 g-1, with basic nature (PZC ∼ 9.6-10.6) was achieved in our lab, from medium density fibreboard (MDF) and particleboard (PB), engineered wood composites wastes. These highly porous adsorbents were applied in kinetic and equilibrium adsorption studies, in batch and dynamic modes, in powder and monolith forms, of specific adsorptives, considered pollutants, namely phenol (P), p-nitrophenol (PNP) and neutral red (NR). In batch the maximum adsorbed amount was 267, 162 and 92 mg g-1, for PNP, P and NR, respectively. The application of different kinetic models (pseudo-first order, pseudo-second order and intraparticle diffusion model) leads to a better knowledge of the adsorption mechanisms of those adsorptives. The results obtained in the kinetic and equilibrium tests show that the combination of the structural features and the surface chemistry nature of the adsorbents, with the adsorptives properties, establish the kinetic performance, the type and amount adsorbed for each system. This work confirms the potential of these types of wastes in the production of activated carbons and its application in adsorption from liquid phase.

  3. Hydrothermal synthesis and characterization of titanium dioxide nanotubes as novel lithium adsorbents

    SciTech Connect

    Moazeni, Maryam; Hajipour, Hengameh; Askari, Masoud; Nusheh, Mohammad

    2015-01-15

    The ion exchange process is a promising method for lithium extraction from brine and seawater having low concentrations of this element. To achieve this goal, it is vital to use an effective adsorbent with maximum lithium adsorption potential together with a stable structure during extraction and insertion of the ions. In this study, titanium dioxide and then lithium titanate spinel with nanotube morphology was synthesized via a simple two-step hydrothermal process. The produced Li{sub 4}Ti{sub 5}O{sub 12} spinel ternary oxide nanotube with about 70 nm diameter was then treated with dilute acidic solution in order to prepare an adsorbent suitable for lithium adsorption from local brine. Morphological and phase analysis of the obtained nanostructured samples were done by using transmission and scanning electron microscopes along with X-ray diffraction. Lithium ion exchange capacity of this adsorbent was finally evaluated by means of adsorption isotherm. The results showed titanium dioxide adsorbent could recover 39.43 mg/g of the lithium present in 120 mg/L of lithium solution.

  4. Adsorbent capability testing using desorption efficiency method on palm oil fiber

    NASA Astrophysics Data System (ADS)

    Manap, Nor Rahafza Abdul; Shamsudin, Roslinda

    2015-09-01

    The palm oil fiber had been used as filler in making thermoplastics, biocomposites and also used as adsorbent in treating waste water. In this study, palm oil fiber was used as adsorbent to treat indoor air pollutants that caused by toluene, ethylbenzene, ortho-, meta-, and para- xylene (o-, m-, p-xylene). Known amount of pollutants, ranges between 1.3 to 28 ppm was spiked into palm oil fiber and left in refrigerator for 24 hours. Then, elution of the pollutants was carried out by carbon disulphide as mobile phase or eluent. The ability of palm oil fiber as adsorbent was determine using desorption efficiency technique by gas chromatography with flame ionization detector (GC/FID). The desorption efficiency percentage given by toluene was in the range of 88.9% to 100%, 91% to 100% for ethylbenzene, 65% to 100% for pm-xylene and 92.9% to 100% for o-xylene. This percentage indicates that palm oil fiber can be used as adsorbent to treat indoor air pollutants.

  5. [Preparation of novel magnetic dextran affinity adsorbents and their application to purify urokinase].

    PubMed

    Dong, Y S; Liang, F; Yu, X Y; Guo, L A; Chang, J H

    2001-01-01

    The reverse phase suspension and embedment technique were adopted to prepare magnetic dextran microsphere (MDMS). The dispersion medium was mixture of some organic solvents. Span-80 was used as stabilizer. The aqueous dextran with magnetic fluid was suspended in dispersion medium with epichlorohydrin as cross-linking reagent. The mixture was stirred for 30 minutes at room temperature and then heated at 70 degrees C for 4 hours, MDMS was thus obtained. MDMS was activated by epichlorohydrin on which 6-aminohexanoic acid, glycine or ethylene diamine was bonded as spacers. Then it was coupled with p-aminobenzamide, L-arginine methyl ester or guanidohexanoic acid and five magnetic affinity adsorbents were prepared. The MDMS was polydisperse particles with the size of 50-300 meshes and the content of Fe3O4 was about 6.2 per cent in the MDMS. Influence of some parameters such as viscosity and density of organic phase, the volume ratio of organic and aqueous phase, the quantity of surfactant and stirring speed on preparing MDMS was studied. Magnetic affinity adsorbents were used to purify crude urokinase in a bath mode and the effect of coupling reagents and ligands on results of purification was discussed. The bioactivity recovery was 40.0 to 60.7 per cent, the purification-fold was between 14.9 and 32.8, and the adsorptive capacity varies from 89 mg to 121 mg per milliliter of adsorbent. PMID:12541840

  6. 15N and13C NMR investigation of hydroxylamine-derivatized humic substances

    USGS Publications Warehouse

    Thorn, K.A.; Arterburn, J.B.; Mikita, M.A.

    1992-01-01

    Five fulvic and humic acid samples of diverse origins were derivatized with 15N-labeled hydroxylamine and analyzed by liquid-phase 15N NMR spectrometry. The 15N NMR spectra indicated that hydroxylamine reacted similarly with all samples and could discriminate among carbonyl functional groups. Oximes were the major derivatives; resonances attributable to hydroxamic acids, the reaction products of hydroxylamine with esters, and resonances attributable to the tautomeric equilibrium position between the nitrosophenol and monoxime derivatives of quinones, the first direct spectroscopic evidence for quinones, also were evident. The 15N NMR spectra also suggested the presence of nitriles, oxazoles, oxazolines, isocyanides, amides, and lactams, which may all be explained in terms of Beckmann reactions of the initial oxime derivatives. INEPT and ACOUSTIC 15N NMR spectra provided complementary information on the derivatized samples. 13C NMR spectra of derivatized samples indicated that the ketone/quinone functionality is incompletely derivatized with hydroxylamine. ?? 1991 American Chemical Society.

  7. The persistence length of adsorbed dendronized polymers

    NASA Astrophysics Data System (ADS)

    Grebikova, Lucie; Kozhuharov, Svilen; Maroni, Plinio; Mikhaylov, Andrey; Dietler, Giovanni; Schlüter, A. Dieter; Ullner, Magnus; Borkovec, Michal

    2016-07-01

    The persistence length of cationic dendronized polymers adsorbed onto oppositely charged substrates was studied by atomic force microscopy (AFM) and quantitative image analysis. One can find that a decrease in the ionic strength leads to an increase of the persistence length, but the nature of the substrate and of the generation of the side dendrons influence the persistence length substantially. The strongest effects as the ionic strength is being changed are observed for the fourth generation polymer adsorbed on mica, which is a hydrophilic and highly charged substrate. However, the observed dependence on the ionic strength is much weaker than the one predicted by the Odijk, Skolnik, and Fixman (OSF) theory for semi-flexible chains. Low-generation polymers show a variation with the ionic strength that resembles the one observed for simple and flexible polyelectrolytes in solution. For high-generation polymers, this dependence is weaker. Similar dependencies are found for silica and gold substrates. The observed behavior is probably caused by different extents of screening of the charged groups, which is modified by the polymer generation, and to a lesser extent, the nature of the substrate. For highly ordered pyrolytic graphite (HOPG), which is a hydrophobic and weakly charged substrate, the electrostatic contribution to the persistence length is much smaller. In the latter case, we suspect that specific interactions between the polymer and the substrate also play an important role.The persistence length of cationic dendronized polymers adsorbed onto oppositely charged substrates was studied by atomic force microscopy (AFM) and quantitative image analysis. One can find that a decrease in the ionic strength leads to an increase of the persistence length, but the nature of the substrate and of the generation of the side dendrons influence the persistence length substantially. The strongest effects as the ionic strength is being changed are observed for the fourth

  8. Protein-Inhibitor Interaction Studies Using NMR

    PubMed Central

    Ishima, Rieko

    2015-01-01

    Solution-state NMR has been widely applied to determine the three-dimensional structure, dynamics, and molecular interactions of proteins. The designs of experiments used in protein NMR differ from those used for small-molecule NMR, primarily because the information available prior to an experiment, such as molecular mass and knowledge of the primary structure, is unique for proteins compared to small molecules. In this review article, protein NMR for structural biology is introduced with comparisons to small-molecule NMR, such as descriptions of labeling strategies and the effects of molecular dynamics on relaxation. Next, applications for protein NMR are reviewed, especially practical aspects for protein-observed ligand-protein interaction studies. Overall, the following topics are described: (1) characteristics of protein NMR, (2) methods to detect protein-ligand interactions by NMR, and (3) practical aspects of carrying out protein-observed inhibitor-protein interaction studies. PMID:26361636

  9. "Solvent Effects" in 1H NMR Spectroscopy.

    ERIC Educational Resources Information Center

    Cavaleiro, Jose A. S.

    1987-01-01

    Describes a simple undergraduate experiment in chemistry dealing with the "solvent effects" in nuclear magnetic resonance (NMR) spectroscopy. Stresses the importance of having students learn NMR spectroscopy as a tool in analytical chemistry. (TW)

  10. Push-through Direction Injectin NMR Automation

    EPA Science Inventory

    Nuclear magnetic resonance (NMR) and mass spectrometry (MS) are the two major spectroscopic techniques successfully used in metabolomics studies. The non-invasive, quantitative and reproducible characteristics make NMR spectroscopy an excellent technique for detection of endogeno...

  11. Atomic Motion in Low-Coverage Helium Films Adsorbed in FSM Nanochannels

    NASA Astrophysics Data System (ADS)

    Matsushita, Taku; Kuze, Atsushi; Kawai, Ryosuke; Hieda, Mitsunori; Wada, Nobuo

    2013-06-01

    4He and 3He films adsorbed in nanoporous silicates have shown similar heat capacities until the quantum-fluid layer appears at coverages over the first-layer completion n 1. To obtain information on dynamics of adatoms at low coverages below the quantum fluid region, we have done pulsed-NMR experiment at 3.3 MHz for 3He films adsorbed in straight 2.4 nm nanochannels of FSM silicates. The spin-lattice and spin-spin relaxation times T 1 and T 2 observed at 0.54-7 K were well described by the two-dimensional version of the Bloembergen-Purcell-Pound model. At coverages 0.4-1.7 n 1, minima of T 1, indicating the spin correlation time τ c of 4.8×10-8 sec, were observed at temperatures between 6 and 3 K. With decreasing temperature, changes in T 1 and T 2 become small below about 1.5 K, suggesting crossover from thermally-activated motion to quantum tunneling. In contrast to large variations below n 1, both relaxation times above n 1 are almost independent of coverage, which is likely to indicate that τ c is determined by interlayer exchange of adatoms. Below n 1, onsets for localization of adatoms were suggested by a decrease in T 2.

  12. Ozonolysis of surface adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

    NASA Astrophysics Data System (ADS)

    O'Neill, E. M.; Kawam, A. Z.; Van Ry, D. A.; Hinrichs, R. Z.

    2013-07-01

    Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near monolayer surface concentrations of 3 × 1018 molecules m-2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (±0.8) × 10-7 and 2 (±1) × 10-6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV-visible radiation (λ>300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(±1) but had no effect on ozonolysis of the alkene side-chain.

  13. Deuterium Exchange Kinetics by NMR.

    ERIC Educational Resources Information Center

    Roper, G. C.

    1985-01-01

    Describes a physical chemistry experiment which allows such concepts as kinetics, catalysis, isotope shifts, coupling constants, and the use of nuclear magnetic resonance (NMR) for quantitative work to be covered in the same exercise. Background information, experimental procedures used, and typical results obtained are included. (JN)

  14. Petrophysical applications of NMR imaging

    SciTech Connect

    Rothwell, W.P.; Vinegar, H.J.

    1985-12-01

    A system for obtaining high-resolution NMR images of oil field cores is described. Separate proton density and T/sub 2/ relaxation images are obtained to distinguish spatial variations of fluid-filled porosity and the physical nature of the pores. Results are presented for typical sandstones.

  15. QUANTITATIVE 15N NMR SPECTROSCOPY

    EPA Science Inventory

    Line intensities in 15N NMR spectra are strongly influenced by spin-lattice and spin-spin relaxation times, relaxation mechanisms and experimental conditions. Special care has to be taken in using 15N spectra for quantitative purposes. Quantitative aspects are discussed for the 1...

  16. NMR imaging of fluid dynamics in reservoir core.

    PubMed

    Baldwin, B A; Yamanashi, W S

    1988-01-01

    A medical NMR imaging instrument has been modified to image water and oil in reservoir rocks by the construction of a new receiving coil. Both oil and water inside the core produced readily detectable proton NMR signals, while the rock matrix produced no signal. Because of similar T2 NMR relaxation times, the water was doped with a paramagnetic ion, Mn+2, to reduce its T2 relaxation time. This procedure enhanced the separation between the oil and water phases in the resulting images. Sequential measurements, as water imbibed into one end and oil was expelled from the other end of a core plug, produced a series of images which showed the dynamics of the fluids. For water-wet Berea Sandstone a flood front was readily observed, but some of the oil was apparently left behind in small, isolated pockets which were larger than individual pores. After several additional pore volumes of water flowed through the plug the NMR image indicated a homogeneous distribution of oil. The amount of residual oil, as determined from the ratio of NMR intensities, closely approximated the residual oil saturation of fully flooded Berea samples measured by Dean-Stark extraction. A Berea sandstone core treated to make it partially oil-wet, did not show a definitive flood front, but appeared to channel the water around the perimeter of the core plug. The relative ease with which these images were made indicates that NMR imaging can be a useful technique to follow the dynamics of oil and water through a core plug for a variety of production processes. PMID:3226235

  17. Determination of Molecular Self-Diffusion Coefficients Using Pulsed-Field-Gradient NMR: An Experiment for Undergraduate Physical Chemistry Laboratory

    ERIC Educational Resources Information Center

    Harmon, Jennifer; Coffman, Cierra; Villarrial, Spring; Chabolla, Steven; Heisel, Kurt A.; Krishnan, Viswanathan V.

    2012-01-01

    NMR spectroscopy has become one of the primary tools that chemists utilize to characterize a range of chemical species in the solution phase, from small organic molecules to medium-sized proteins. A discussion of NMR spectroscopy is an essential component of physical and biophysical chemistry lecture courses, and a number of instructional…

  18. In situ solid-state NMR spectroscopy of electrochemical cells: batteries, supercapacitors, and fuel cells.

    PubMed

    Blanc, Frédéric; Leskes, Michal; Grey, Clare P

    2013-09-17

    prevent dendrite formation. The in situ method was also applied to monitor (by (11)B NMR) electrochemical double-layer formation in supercapacitors in real time. Though this method is useful, it comes with challenges. The separation of the contributions from the different cell components in the NMR spectra is not trivial because of overlapping resonances. In addition, orientation-dependent NMR interactions, including the spatial- and orientation-dependent bulk magnetic susceptibility (BMS) effects, can lead to resonance broadening. Efforts to understand and mitigate these BMS effects are discussed in this Account. The in situ NMR investigation of fuel cells initially focused on the surface electrochemistry at the electrodes and the electrochemical oxidation of methanol and CO to CO2 on the Pt cathode. On the basis of the (13)C and (195)Pt NMR spectra of the adsorbates and electrodes, CO adsorbed on Pt and other reaction intermediates and complete oxidation products were detected and their mode of binding to the electrodes investigated. Appropriate design and engineering of the NMR hardware has allowed researchers to integrate intact direct methanol fuel cells into NMR probes. Chemical transformations of the circulating methanol could be followed and reaction intermediates could be detected in real time by either (2)H or (13)C NMR spectroscopy. By use of the in situ NMR approach, factors that control fuel cell performance, such as methanol cross over and catalyst performance, were identified. PMID:24041242

  19. Establishing resolution-improved NMR spectroscopy in high magnetic fields with unknown spatiotemporal variations.

    PubMed

    Zhang, Zhiyong; Smith, Pieter E S; Cai, Shuhui; Zheng, Zhenyao; Lin, Yulan; Chen, Zhong

    2015-12-28

    A half-century quest for higher magnetic fields has been an integral part of the progress undergone in the Nuclear Magnetic Resonance (NMR) study of materials' structure and dynamics. Because 2D NMR relies on systematic changes in coherences' phases as a function of an encoding time varied over a series of independent experiments, it generally cannot be applied in temporally unstable fields. This precludes most NMR methods from being used to characterize samples situated in hybrid or resistive magnets that are capable of achieving extremely high magnetic field strength. Recently, "ultrafast" NMR has been developed into an effective and widely applicable methodology enabling the acquisition of a multidimensional NMR spectrum in a single scan; it can therefore be used to partially mitigate the effects of temporally varying magnetic fields. Nevertheless, the strong interference of fluctuating fields with the spatial encoding of ultrafast NMR still severely restricts measurement sensitivity and resolution. Here, we introduce a strategy for obtaining high resolution NMR spectra that exploits the immunity of intermolecular zero-quantum coherences (iZQCs) to field instabilities and inhomogeneities. The spatial encoding of iZQCs is combined with a J-modulated detection scheme that removes the influence of arbitrary field inhomogeneities during acquisition. This new method can acquire high-resolution one-dimensional NMR spectra in large inhomogeneous and fluctuating fields, and it is tested with fields experimentally modeled to mimic those of resistive and resistive-superconducting hybrid magnets. PMID:26723664

  20. Establishing resolution-improved NMR spectroscopy in high magnetic fields with unknown spatiotemporal variations

    SciTech Connect

    Zhang, Zhiyong; Cai, Shuhui; Zheng, Zhenyao; Lin, Yulan E-mail: lylfj2005@xmu.edu.cn; Chen, Zhong E-mail: lylfj2005@xmu.edu.cn; Smith, Pieter E. S.

    2015-12-28

    A half-century quest for higher magnetic fields has been an integral part of the progress undergone in the Nuclear Magnetic Resonance (NMR) study of materials’ structure and dynamics. Because 2D NMR relies on systematic changes in coherences’ phases as a function of an encoding time varied over a series of independent experiments, it generally cannot be applied in temporally unstable fields. This precludes most NMR methods from being used to characterize samples situated in hybrid or resistive magnets that are capable of achieving extremely high magnetic field strength. Recently, “ultrafast” NMR has been developed into an effective and widely applicable methodology enabling the acquisition of a multidimensional NMR spectrum in a single scan; it can therefore be used to partially mitigate the effects of temporally varying magnetic fields. Nevertheless, the strong interference of fluctuating fields with the spatial encoding of ultrafast NMR still severely restricts measurement sensitivity and resolution. Here, we introduce a strategy for obtaining high resolution NMR spectra that exploits the immunity of intermolecular zero-quantum coherences (iZQCs) to field instabilities and inhomogeneities. The spatial encoding of iZQCs is combined with a J-modulated detection scheme that removes the influence of arbitrary field inhomogeneities during acquisition. This new method can acquire high-resolution one-dimensional NMR spectra in large inhomogeneous and fluctuating fields, and it is tested with fields experimentally modeled to mimic those of resistive and resistive-superconducting hybrid magnets.

  1. Establishing resolution-improved NMR spectroscopy in high magnetic fields with unknown spatiotemporal variations

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiyong; Smith, Pieter E. S.; Cai, Shuhui; Zheng, Zhenyao; Lin, Yulan; Chen, Zhong

    2015-12-01

    A half-century quest for higher magnetic fields has been an integral part of the progress undergone in the Nuclear Magnetic Resonance (NMR) study of materials' structure and dynamics. Because 2D NMR relies on systematic changes in coherences' phases as a function of an encoding time varied over a series of independent experiments, it generally cannot be applied in temporally unstable fields. This precludes most NMR methods from being used to characterize samples situated in hybrid or resistive magnets that are capable of achieving extremely high magnetic field strength. Recently, "ultrafast" NMR has been developed into an effective and widely applicable methodology enabling the acquisition of a multidimensional NMR spectrum in a single scan; it can therefore be used to partially mitigate the effects of temporally varying magnetic fields. Nevertheless, the strong interference of fluctuating fields with the spatial encoding of ultrafast NMR still severely restricts measurement sensitivity and resolution. Here, we introduce a strategy for obtaining high resolution NMR spectra that exploits the immunity of intermolecular zero-quantum coherences (iZQCs) to field instabilities and inhomogeneities. The spatial encoding of iZQCs is combined with a J-modulated detection scheme that removes the influence of arbitrary field inhomogeneities during acquisition. This new method can acquire high-resolution one-dimensional NMR spectra in large inhomogeneous and fluctuating fields, and it is tested with fields experimentally modeled to mimic those of resistive and resistive-superconducting hybrid magnets.

  2. Comprehensive multiphase NMR: a promising technology to study plants in their native state.

    PubMed

    Wheeler, Heather L; Soong, Ronald; Courtier-Murias, Denis; Botana, Adolfo; Fortier-Mcgill, Blythe; Maas, Werner E; Fey, Michael; Hutchins, Howard; Krishnamurthy, Sridevi; Kumar, Rajeev; Monette, Martine; Stronks, Henry J; Campbell, Malcolm M; Simpson, Andre

    2015-09-01

    Nuclear magnetic resonance (NMR) spectroscopy is arguably one the most powerful tools to study the interactions and molecular structure within plants. Traditionally, however, NMR has developed as two separate fields, one dealing with liquids and the other dealing with solids. Plants in their native state contain components that are soluble, swollen, and true solids. Here, a new form of NMR spectroscopy, developed in 2012, termed comprehensive multiphase (CMP)-NMR is applied for plant analysis. The technology composes all aspects of solution, gel, and solid-state NMR into a single NMR probe such that all components in all phases in native unaltered samples can be studied and differentiated in situ. The technology is evaluated using wild-type Arabidopsis thaliana and the cellulose-deficient mutant ectopic lignification1 (eli1) as examples. Using CMP-NMR to study intact samples eliminated the bias introduced by extraction methods and enabled the acquisition of a more complete structural and metabolic profile; thus, CMP-NMR revealed molecular differences between wild type (WT) and eli1 that could be overlooked by conventional methods. Methanol, fatty acids and/or lipids, glutamine, phenylalanine, starch, and nucleic acids were more abundant in eli1 than in WT. Pentaglycine was present in A. thaliana seedlings and more abundant in eli1 than in WT. PMID:25855560

  3. Magnesium oxide-impregnated tuff soil-derived ceramic: a novel cadmium(II) adsorbing media

    NASA Astrophysics Data System (ADS)

    Salim, Md; Bhakta, Jatindra N.; Maneesh, Namburath; Munekage, Yukihiro; Motomura, Kevin

    2015-07-01

    The contamination of cadmium (Cd) in the aquatic environment is one of the serious environmental and human health's risks. The present study attempted to develop the potential magnesium oxide (MgO)-impregnated tuff soil-derived ceramic (MITDC)-based novel adsorbent media for adsorbing higher rate of cadmium [Cd(II)] from water phase. A potential MITDC adsorbent media was developed using volcanic raw tuff soil and its Cd(II) adsorption capacity from water phase was evaluated comparing with the raw tuff soil. A series of studies were carried out in an agitated batch method at 20 ± 2 °C to characterize the adsorption capacity of MITDC under different conditions of factors, such as contact time (0-360 min), initial pH (3-11) of solution, dose of MITDC (2, 5, 7.5 and 10 g/L), and initial concentration of Cd(II) (5, 10, 20, 30, and 40 mg/L), influencing the adsorption mechanism. MITDC exhibited the equilibrium state of maximum Cd(II) adsorption at the contact time 120 min and pH 4.7 (removed 98.2 % Cd) when initial Cd(II) concentration was 10 mg/L in the present study. The dose of 7.5 g MITDC/L showed maximum removal of Cd(II) from water. Experimental data were described by the Freundlich and the Langmuir isotherms and equilibrium data fitted well with the Langmuir model (R 2 = 0.996). The Cd(II) adsorption capacity of MITDC was 31.25 mg/g. The high Cd(II) adsorption capacity indicated that novel MITDC could be used as a potential ceramic adsorbent media to remove high rate of Cd(II) from aqueous phase.

  4. SORPTION PROPERTIES OF MODEL COMPOUNDS ON C18 ADSORBENTS

    EPA Science Inventory

    The bonded silica adsorbent Bondapak-C18 was evaluated for removing organic matter from secondary sewage effluents and from solutions of pure organic compounds. The adsorbent is hydrophobic and its behavior with water samples may be erratic unless first wet with a solvent. Howeve...

  5. Convection Compensated Electrophoretic NMR

    NASA Astrophysics Data System (ADS)

    He, Qiuhong; Wei, Zhaohui

    2001-06-01

    A novel method of convection compensated ENMR (CC-ENMR) has been developed to detect electrophoretic motion of ionic species in the presence of bulk solution convection. This was accomplished using a gradient moment nulling technique to remove spectral artifacts from heat-induced convection and using the polarity switch of the applied electric field to retain spin phase modulations due to electrophoretic flow. Experiments were carried out with a mixture of 100 mM L-aspartic acid and 100 mM 4,9-dioxa-1,12-dodecanediamine to demonstrate this new method of ENMR. CC-ENMR enhances our previously developed capillary array ENMR (CA-ENMR) in solving the convection problem. The combined CA- and CC-ENMR approach strengthens the potential of multidimensional ENMR in simultaneous structural determination of coexisting proteins and protein conformations in biological buffer solutions of high ionic strength. Structural mapping of interacting proteins during biochemical reactions becomes possible in the future using ENMR techniques, which may have a profound impact on the understanding of biological events, including protein folding, genetic control, and signal transduction in general.

  6. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1992-05-27

    This report covers the progress made on the title project for the project period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups that determine the reactivity of coals. Special attention is being paid to methods that are compatible with the very high magic angle sample spinning rates needed for operation at the high magnetic field strengths available today. Polarization inversion methods utilizing the difference in heat capacities of small groups of spins are particularly promising. Methods combining proton-proton spin diffusion with {sup 13}C CPMAS readout are being developed to determine the connectivity of functional groups in coals in a high sensitivity relay type of experiment. Additional work is aimed a delineating the role of methyl group rotation in the proton NMR relaxation behavior of coals.

  7. Kinetic study of lead adsorption to composite biopolymer adsorbent

    SciTech Connect

    Seki, H.; Suzuki, A.

    1999-03-15

    A kinetic study of lead adsorption to composite biopolymer adsorbents was carried out. Spherical and membranous adsorbents containing two biopolymers, humic acid and alginic acid, were used for lead adsorption in dilute acidic solutions. The shrinking core model derived by M.G. Rao and A.K. Gupta was applied to describe the rate process of lead adsorption to spherical adsorbents (average radii of 0.12, 0.15, and 0.16 cm). Furthermore, the shrinking core model was modified and adapted for description of the rate process of lead adsorption to membranous adsorbent (average thickness of 0.0216 cm). The adsorption rate process for both the cases was well described and average apparent lead diffusion coefficients of about 6 {times} 10{sup {minus}6} and 7 {times} 10{sup {minus}6} cm{sup 2}/s were found for the spherical and membranous adsorbents, respectively.

  8. Structure and properties of water film adsorbed on mica surfaces

    NASA Astrophysics Data System (ADS)

    Zhao, Gutian; Tan, Qiyan; Xiang, Li; Cai, Di; Zeng, Hongbo; Yi, Hong; Ni, Zhonghua; Chen, Yunfei

    2015-09-01

    The structure profiles and physical properties of the adsorbed water film on a mica surface under conditions with different degrees of relative humidity are investigated by a surface force apparatus. The first layer of the adsorbed water film shows ice-like properties, including a lattice constant similar with ice crystal, a high bearing capacity that can support normal pressure as high as 4 MPa, a creep behavior under the action of even a small normal load, and a character of hydrogen bond. Adjacent to the first layer of the adsorbed water film, the water molecules in the outer layer are liquid-like that can flow freely under the action of external loads. Experimental results demonstrate that the adsorbed water layer makes the mica surface change from hydrophilic to weak hydrophobic. The weak hydrophobic surface may induce the latter adsorbed water molecules to form water islands on a mica sheet.

  9. Kinetic Study of Lead Adsorption to Composite Biopolymer Adsorbent.

    PubMed

    Seki; Suzuki

    1999-03-15

    A kinetic study of lead adsorption to composite biopolymer adsorbents was carried out. Spherical and membranous adsorbents containing two biopolymers, humic acid and alginic acid, were used for lead adsorption in dilute acidic solutions. The shrinking core model derived by M. G. Rao and A. K. Gupta (Chem. Eng. J. 24, 181, 1982) was applied to describe the rate process of lead adsorption to spherical adsorbents (average radii of 0.12, 0.15, and 0.16 cm). Furthermore, the shrinking core model was modified and adapted for description of the rate process of lead adsorption to membranous adsorbent (average thickness of 0.0216 cm). The adsorption rate process for the both cases was well described and average apparent lead diffusion coefficients of about 6 x 10(-6) and 7 x 10(-6) cm2 s-1 were found for the spherical and membranous adsorbents, respectively. Copyright 1999 Academic Press. PMID:10049553

  10. Anomalous fast dynamics of adsorbate overlayers near an incommensurate structural transition.

    PubMed

    Granato, Enzo; Ying, S C; Elder, K R; Ala-Nissila, T

    2013-09-20

    We investigate the dynamics of a compressively strained adsorbed layer on a periodic substrate via a simple two-dimensional model that admits striped and hexagonal incommensurate phases. We show that the mass transport is superfast near the striped-hexagonal phase boundary and in the hexagonal phase. For an initial step profile separating a bare substrate region (or "hole") from the rest of a striped incommensurate phase, the superfast domain wall dynamics leads to a bifurcation of the initial step profile into two interfaces or profiles propagating in opposite directions with a hexagonal phase in between. This yields a theoretical understanding of the recent experiments for the Pb/Si(111) system. PMID:24093278

  11. Removal of hydrogen sulfide at ambient conditions on cadmium/GO-based composite adsorbents.

    PubMed

    Florent, Marc; Wallace, Rajiv; Bandosz, Teresa J

    2015-06-15

    Cadmium-based materials with various hydroxide to carbonate ratios and their composites with graphite oxide were synthesized by a fast and simple precipitation procedure and then used as H2S adsorbents at ambient conditions in the dark or upon a visible light exposure. The structural properties and chemical features of the adsorbents were analyzed before and after hydrogen sulfide adsorption. The results showed that the high ratio of hydroxide to carbonate led to an improved H2S adsorption capacity. In moist conditions cadmium hydroxide was the best adsorbent. Moreover, it showed photoactive properties. While the incorporation of a graphene-based phase slightly decreased the extent of the improvement in the H2S adsorption capacity in moist conditions caused by photoactivity, its presence in the composites enhanced the performance in dry conditions. This was linked to photoactivity of CdS that can split H2S resulting in the formation of water in the system. The graphene-based phase enhanced the electron transfer and delayed the recombination of photoinduced charges. Carbonate-based materials showed a very good adsorption capacity in dark conditions in the presence of moisture. Upon the light exposure, CdS likely photocatalyzes the reduction of carbonate ions to formates/formaldehydes. Their deposition on the surface limits the number of sites available to H2S adsorption. PMID:25792480

  12. Solution NMR of large molecules and assemblies†

    PubMed Central

    Foster, Mark P.; McElroy, Craig A.; Amero, Carlos D.

    2008-01-01

    Solution NMR spectroscopy represents a powerful tool for examining the structure and function of biological macromolecules. The advent of multidimensional (2D–4D) NMR, together with the widespread use of uniform isotopic labeling of proteins and RNA with the NMR-active isotopes, 15N and 13C, opened the door to detailed analyses of macromolecular structure, dynamics and interactions of smaller macromolecules (< ~25 kDa). Over the past 10 years, advances in NMR and isotope labeling methods have expanded the range of NMR-tractable targets by at least an order of magnitude. Here we briefly describe the methodological advances that allow NMR spectroscopy of large macromolecules and their complexes, and provide a perspective on the wide range of applications of NMR to biochemical problems. PMID:17209543

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

    SciTech Connect

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

    2014-08-01

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

  14. Physical and Chemical Effects of Two-Phase Brine/Supercritical-CO2 Fluid Flow on Clastic Rocks: Real-Time Monitoring and NMR Imaging of Flow-Through Core Experiments

    NASA Astrophysics Data System (ADS)

    Shaw, C. A.; Vogt, S.; Maneval, J. E.; Brox, T.; Skidmore, M. L.; Codd, S. L.; Seymour, J. D.

    2010-12-01

    Sandstone core samples were challenged with a supercritical CO2-saturated brine mixture in a laboratory flow-through core reactor system over a range of temperatures and brine strengths. Cores of quartz arenite from the Berea formation were selected to represent ideal ‘clean’ sandstone These laboratory experiments potentially provide an analog for the acidification of pore fluids near the brine/CO2 interface during CO2 flooding of depleted clastic hydrocarbon reservoirs for carbon sequestration. Flow in the reactor was perpendicular to bedding. Initial experiments were run at 50°C and 100°C with brine concentrations of 1g/L and 10g/L (TDS) to test effects of different temperatures and brine compositions. Real-time monitoring of fluid pH and conductivity provided a measure of reaction rates. Introduction of supercritical CO2 into the brine-saturated cores initiated a reduction in pH accompanied by an increase in conductivity. NMR images of fresh cores were compared with images of challenged cores using a protocol for pixel-by-pixel comparison to determine the effects on bulk pore volume and geometry. Two types of imaging experiments were conducted: multi-slice spin echo and 3-D spin echo images. Multi-slice experiments had a slice thickness of 1.5 mm and an in-plane resolution of 0.27 mm x 0.27 mm, and 3-D experiments had a resolution of 0.47 mm x 0.55 mm x 0.55mm. Imaging results reflected the observed changes in the physical and chemical structure post-challenge. Two-dimensional relaxation correlation experiments were also conducted to probe the pore sizes, connectivity and fluid saturation of the rock cores before and after challenging. Chemical analyses and microscopic examination of the challenged cores will provide a better understanding of alteration in the cores and the changes in the volume, geometry and connectivity of pore space.

  15. Detecting and Quantifying Organic Contaminants in Sediments with NMR

    NASA Astrophysics Data System (ADS)

    Fay, E. L.; Knight, R. J.

    2015-12-01

    Nuclear magnetic resonance (NMR) methods have the potential to detect and monitor free-phase organic contaminants in sediments, both in the laboratory and in the field. NMR directly detects signal from hydrogen-bearing fluids; the signal amplitude is proportional to the total amount of hydrogen present, while the signal decay rate provides information about fluid properties and interactions with the surrounding sediments. Contrasting relaxation times (T2) or diffusion coefficients (D) allow the separation of water signal from contaminant signal. In this work, we conduct a laboratory study to assess the use of NMR measurements to detect and quantify diesel, gasoline, crude oil, and tri-chloroethylene in sediments. We compare the T2 distributions for sediments containing only water, only contaminant, and both water and contaminant, confirming that the identification and quantification of contaminants using T2 data alone is limited by overlapping water and contaminant T2 distributions in some sediments. We leverage the contrast between the diffusion coefficient of water and that of diesel and crude oil to separate contaminant signal from water signal in D-T2 maps. D-T2 distributions are measured both using a pulsed gradient method and a static gradient method similar to methods used with logging tools, allowing us to compare the ability of each method to quantify diesel and crude oil when water is also present. There is the potential to apply these methods to characterize and monitor contaminated sites using commercially available NMR logging tools.

  16. NMR spin relaxation rates in the Heisenberg bilayer

    NASA Astrophysics Data System (ADS)

    Mendes, Tiago; Curro, Nicholas; Scalettar, Richard; Paiva, Thereza; Dos Santos, Raimundo R.

    One of the striking features of heavy fermions is the fact that in the vicinity of a quantum phase transition these systems exhibit the breakdown of Fermi-liquid behavior and superconductivity. Nuclear magnetic resonance (NMR) expirements play an important role in the study of these phenomena. Measurements of NMR spin relaxation rates and Knight shift, for instance, can be used to probe the electronic spin susceptibility of these systems. Here we studied the NMR response of the Heisenberg bilayer model. In this model, it is well known that the increase of the interplane coupling between the planes, Jperp, supresses the antiferromagnetic order at a quantum critical point (QCP). We use stochastic series expansion (SSE) and the maximum-entropy analytic continuation method to calculate the NMR spin lattice relaxation rate 1 /T1 and the spin echo decay 1 /T2 G as function of Jperp. The spin echo decay, T2 G increases for small Jperp, due to the increase of the order parameter, and then vanishes abruptly in the QCP. The effects of Jperp dilution disorder in the QCP and the relaxation rates are also discussed. This research was supported by the NNSA Grant Number DE-NA 0002908, and Ciência sem fronteiras program/CNPQ.

  17. X-ray CT and NMR imaging of rocks

    SciTech Connect

    Vinegar, H.J.

    1986-03-01

    In little more than a decade, X-ray computerized tomography (CT) and nuclear magnetic resonance (NMR) imaging have become the premier modalities of medical radiology. Both of these imaging techniques also promise to be useful tools in petrophysics and reservoir engineering, because CT and NMR can nondestructively image a host of physical and chemical properties of porous rocks and multiple fluid phases contained within their pores. The images are taken within seconds to minutes, at reservoir temperatures and pressures, with spatial resolution on the millimeter and submillimeter level. The physical properties imaged by the two techniques are complementary. CT images bulk density and effective atomic number. NMR images the nuclide concentration, M/sub 0/, of a variety of nuclei (/sup 1/H, /sup 19/F, /sup 23/Na, /sup 31/P, etc.), their longitudinal and transverse relaxation-time curves (t/sub 1/ and t/sub 2/), and their chemical shift spectra. In rocks, CT images both rock matrix and pore fluids, while NMR images only mobile fluids and the interactions of these mobile fluids with the confining surfaces of the pores.

  18. Calculation of NMR lineshapes for Ba-Al-Ge clathrates

    NASA Astrophysics Data System (ADS)

    Rodriguez, Sergio; Gou, Weiping; Ross, Joseph

    2008-10-01

    Clathrates consist of Si, Ge, or Sn cages in a crystalline framework, with guest atoms inside the cages. They have gained interest due to thermoelectric properties suitable for potential device application. To understand Al substitutional configurations, we calculated Al NMR line shapes for several structures with compositions Ba8Ge46-x-yAlxy for x=3,8,11,12,16,24; y=2,3; where represents a vacancy. The results were obtained by calculating Electric Field Gradients (EFG) for Al sites of type-I clathrates assuming an ordered superstructure of vacancies and framework occupation. We used ab initio methods in the Generalized Gradient Approximation as implemented by the WIEN2k program, and used the results to simulate NMR lineshapes numerically. These were compared to our previously reported NMR lineshapes. In the case of Ba8Ge31Al123 four Al sites in the superstructure include two sites with small EFG where the vacancy is far away and two sites with large EFG with a vacancy adjacent to Al. Assuming a larger Knight shift for sites next to vacancies, we obtain good agreement with NMR experimental results for reduced-Al Ba8Ge34Al12, while for the Zintl phase Ba8Ge30Al16 we obtain good agreement with no spontaneous vacancies. We infer that Al prefers locations close to vacancies rather than random occupation. This work was supported by Robert A. Welch Foundation (Grant A-1526).

  19. Advancements in waste water characterization through NMR spectroscopy: review.

    PubMed

    Alves Filho, Elenilson G; Alexandre e Silva, Lorena M; Ferreira, Antonio G

    2015-09-01

    There are numerous organic pollutants that lead to several types of ecosystem damage and threaten human health. Wastewater treatment plants are responsible for the removal of natural and anthropogenic pollutants from the sewage, and because of this function, they play an important role in the protection of human health and the environment. Nuclear magnetic resonance (NMR) has proven to be a valuable analytical tool as a result of its versatility in characterizing both overall chemical composition as well as individual species in a wide range of mixtures. In addition, NMR can provide physical information (rigidity, dynamics, etc.) as well as permit in depth quantification. Hyphenation with other techniques such as liquid chromatography, solid phase extraction and mass spectrometry creates unprecedented capabilities for the identification of novel and unknown chemical species. Thus, NMR is widely used in the study of different components of wastewater, such as complex organic matter (fulvic and humic acids), sludge and wastewater. This review article summarizes the NMR spectroscopy methods applied in studies of organic pollutants from wastewater to provide an exhaustive review of the literature as well as a guide for readers interested in this topic. PMID:25280056

  20. Two-dimensional NMR spectrometry

    SciTech Connect

    Farrar, T.C.

    1987-06-01

    This article is the second in a two-part series. In part one (ANALYTICAL CHEMISTRY, May 15) the authors discussed one-dimensional nuclear magnetic resonance (NMR) spectra and some relatively advanced nuclear spin gymnastics experiments that provide a capability for selective sensitivity enhancements. In this article and overview and some applications of two-dimensional NMR experiments are presented. These powerful experiments are important complements to the one-dimensional experiments. As in the more sophisticated one-dimensional experiments, the two-dimensional experiments involve three distinct time periods: a preparation period, t/sub 0/; an evolution period, t/sub 1/; and a detection period, t/sub 2/.