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Sample records for double-quantum mas nmr

  1. Investigation of domain size in polymer membranes using double quantum filtered spin diffusion MAS NMR.

    SciTech Connect

    Fujimoto, Cy H.; Alam, Todd Michael; Cherry, Brian Ray; Cornelius, Christopher James

    2005-02-01

    Solid-state {sup 1}H magic angle spinning (MAS) NMR was used to investigate sulfonated Diels-Alder poly(phenlylene) polymer membranes. Under high spinning speed {sup 1}H MAS conditions, the proton environments of the sulfonic acid and phenylene polymer backbone are resolved. A double-quantum (DQ) filter using the rotor-synchronized back-to-back (BABA) NMR multiple-pulse sequence allowed the selective suppression of the sulfonic proton environment in the {sup 1}H MAS NMR spectra. This DQ filter in conjunction with a spin diffusion NMR experiment was then used to measure the domain size of the sulfonic acid component within the membrane. In addition, the temperature dependence of the sulfonic acid spin-spin relaxation time (T{sub 2}) was determined, providing an estimate of the activation energy for the proton dynamics of the dehydrated membrane.

  2. Proton chemical shift tensors determined by 3D ultrafast MAS double-quantum NMR spectroscopy

    SciTech Connect

    Zhang, Rongchun; Mroue, Kamal H.; Ramamoorthy, Ayyalusamy

    2015-10-14

    Proton NMR spectroscopy in the solid state has recently attracted much attention owing to the significant enhancement in spectral resolution afforded by the remarkable advances in ultrafast magic angle spinning (MAS) capabilities. In particular, proton chemical shift anisotropy (CSA) has become an important tool for obtaining specific insights into inter/intra-molecular hydrogen bonding. However, even at the highest currently feasible spinning frequencies (110–120 kHz), {sup 1}H MAS NMR spectra of rigid solids still suffer from poor resolution and severe peak overlap caused by the strong {sup 1}H–{sup 1}H homonuclear dipolar couplings and narrow {sup 1}H chemical shift (CS) ranges, which render it difficult to determine the CSA of specific proton sites in the standard CSA/single-quantum (SQ) chemical shift correlation experiment. Herein, we propose a three-dimensional (3D) {sup 1}H double-quantum (DQ) chemical shift/CSA/SQ chemical shift correlation experiment to extract the CS tensors of proton sites whose signals are not well resolved along the single-quantum chemical shift dimension. As extracted from the 3D spectrum, the F1/F3 (DQ/SQ) projection provides valuable information about {sup 1}H–{sup 1}H proximities, which might also reveal the hydrogen-bonding connectivities. In addition, the F2/F3 (CSA/SQ) correlation spectrum, which is similar to the regular 2D CSA/SQ correlation experiment, yields chemical shift anisotropic line shapes at different isotropic chemical shifts. More importantly, since the F2/F1 (CSA/DQ) spectrum correlates the CSA with the DQ signal induced by two neighboring proton sites, the CSA spectrum sliced at a specific DQ chemical shift position contains the CSA information of two neighboring spins indicated by the DQ chemical shift. If these two spins have different CS tensors, both tensors can be extracted by numerical fitting. We believe that this robust and elegant single-channel proton-based 3D experiment provides useful atomistic

  3. Proton chemical shift tensors determined by 3D ultrafast MAS double-quantum NMR spectroscopy.

    PubMed

    Zhang, Rongchun; Mroue, Kamal H; Ramamoorthy, Ayyalusamy

    2015-10-14

    Proton NMR spectroscopy in the solid state has recently attracted much attention owing to the significant enhancement in spectral resolution afforded by the remarkable advances in ultrafast magic angle spinning (MAS) capabilities. In particular, proton chemical shift anisotropy (CSA) has become an important tool for obtaining specific insights into inter/intra-molecular hydrogen bonding. However, even at the highest currently feasible spinning frequencies (110-120 kHz), (1)H MAS NMR spectra of rigid solids still suffer from poor resolution and severe peak overlap caused by the strong (1)H-(1)H homonuclear dipolar couplings and narrow (1)H chemical shift (CS) ranges, which render it difficult to determine the CSA of specific proton sites in the standard CSA/single-quantum (SQ) chemical shift correlation experiment. Herein, we propose a three-dimensional (3D) (1)H double-quantum (DQ) chemical shift/CSA/SQ chemical shift correlation experiment to extract the CS tensors of proton sites whose signals are not well resolved along the single-quantum chemical shift dimension. As extracted from the 3D spectrum, the F1/F3 (DQ/SQ) projection provides valuable information about (1)H-(1)H proximities, which might also reveal the hydrogen-bonding connectivities. In addition, the F2/F3 (CSA/SQ) correlation spectrum, which is similar to the regular 2D CSA/SQ correlation experiment, yields chemical shift anisotropic line shapes at different isotropic chemical shifts. More importantly, since the F2/F1 (CSA/DQ) spectrum correlates the CSA with the DQ signal induced by two neighboring proton sites, the CSA spectrum sliced at a specific DQ chemical shift position contains the CSA information of two neighboring spins indicated by the DQ chemical shift. If these two spins have different CS tensors, both tensors can be extracted by numerical fitting. We believe that this robust and elegant single-channel proton-based 3D experiment provides useful atomistic-level structural and dynamical

  4. (27)Al-(27)Al double-quantum single-quantum MAS NMR: Applications to the structural characterization of microporous materials.

    PubMed

    Martineau-Corcos, Charlotte; Dědeček, Jiri; Taulelle, Francis

    In this paper, we review and illustrate applications, reported in the literature or used in our group, of (27)Al-(27)Al double-quantum single-quantum (DQ-SQ) MAS NMR experiments for the structural characterization of Al-containing microporous solids, namely zeolites, aluminophosphates and metal-organic frameworks. Information regarding the periodic frameworks or the localization of the various aluminum species in the materials are obtained from the analysis of the two-dimensional NMR spectra, which allows getting local structural details sometimes inaccessible from other characterization technique. An application of (27)Al-(27)Al of the DQ-SQ experiment for the detection of aluminum pairing in zeolite is shown. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Low-power broadband homonuclear dipolar recoupling in MAS NMR by two-fold symmetry pulse schemes for magnetization transfers and double-quantum excitation

    NASA Astrophysics Data System (ADS)

    Teymoori, Gholamhasan; Pahari, Bholanath; Edén, Mattias

    2015-12-01

    We provide an experimental, numerical, and high-order average Hamiltonian evaluation of an open-ended series of homonuclear dipolar recoupling sequences, SR2 2p 1 with p = 1, 2, 3, … . While operating at a very low radio-frequency (rf) power, corresponding to a nutation frequency of 1/2 of the magic-angle spinning (MAS) rate (ωnut =ωr / 2), these recursively generated double-quantum (2Q) dipolar recoupling schemes offer a progressively improved compensation to resonance offsets and rf inhomogeneity for increasing pulse-sequence order p. The excellent recoupling robustness to these experimental obstacles, as well as to CSA, is demonstrated for 2Q filtering (2QF) experiments and for driving magnetization transfers in 2D NMR correlation spectroscopy, where the sequences may provide either double or zero quantum dipolar Hamiltonians during mixing. Experimental and numerical demonstrations, which mostly target conditions of "ultra-fast" MAS (≳50 kHz) and high magnetic fields, are provided for recoupling of 13C across a wide range of isotropic and anisotropic chemical shifts, as well as dipolar coupling constants, encompassing [2,3-13C2 ]alanine, [1,3-13C2 ]alanine, diammonium [1,4-13C2 ]fumarate, and [U-13 C]tyrosine. When compared at equal power levels, a superior performance is observed for the SR2p 1 sequences with p ⩾ 3 relative to existing and well-established 2Q recoupling techniques. At ultra-fast MAS, proton decoupling is redundant during the homonuclear dipolar recoupling of dilute spins in organic solids, which renders the family of SR2p 1 schemes the first efficient 2Q recoupling option for general applications, such as 2Q-1Q correlation NMR and high-order multiple-quantum excitation, under truly low-power rf conditions.

  6. Low-power broadband homonuclear dipolar recoupling in MAS NMR by two-fold symmetry pulse schemes for magnetization transfers and double-quantum excitation.

    PubMed

    Teymoori, Gholamhasan; Pahari, Bholanath; Edén, Mattias

    2015-12-01

    We provide an experimental, numerical, and high-order average Hamiltonian evaluation of an open-ended series of homonuclear dipolar recoupling sequences, SR [Formula: see text] with p=1,2,3,…. While operating at a very low radio-frequency (rf) power, corresponding to a nutation frequency of 1/2 of the magic-angle spinning (MAS) rate (ωnut=ωr/2), these recursively generated double-quantum (2Q) dipolar recoupling schemes offer a progressively improved compensation to resonance offsets and rf inhomogeneity for increasing pulse-sequence order p. The excellent recoupling robustness to these experimental obstacles, as well as to CSA, is demonstrated for 2Q filtering (2QF) experiments and for driving magnetization transfers in 2D NMR correlation spectroscopy, where the sequences may provide either double or zero quantum dipolar Hamiltonians during mixing. Experimental and numerical demonstrations, which mostly target conditions of "ultra-fast" MAS (≳50kHz) and high magnetic fields, are provided for recoupling of (13)C across a wide range of isotropic and anisotropic chemical shifts, as well as dipolar coupling constants, encompassing [2,3-(13)C2]alanine, [1,3-(13)C2]alanine, diammonium [1,4-(13)C2]fumarate, and [U-(13)C]tyrosine. When compared at equal power levels, a superior performance is observed for the SR [Formula: see text] sequences with p⩾3 relative to existing and well-established 2Q recoupling techniques. At ultra-fast MAS, proton decoupling is redundant during the homonuclear dipolar recoupling of dilute spins in organic solids, which renders the family of SR [Formula: see text] schemes the first efficient 2Q recoupling option for general applications, such as 2Q-1Q correlation NMR and high-order multiple-quantum excitation, under truly low-power rf conditions.

  7. Localized double-quantum-filtered 1H NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Thomas, M. A.; Hetherington, H. P.; Meyerhoff, D. J.; Twieg, D. B.

    The image-guided in vivo spectroscopic (ISIS) pulse sequence has been combined with a double-quantum-filter scheme in order to obtain localized and water-suppressed 1H NMR spectra of J-coupled metabolites. The coherence-transfer efficiency associated with the DQ filter for AX and A 3X spin systems is described. Phantom results of carnosine, alanine, and ethanol in aqueous solution are presented. For comparison, the 1H NMR spectrum of alanine in aqueous solution with the binomial (1331, 2662) spin-echo sequence is also shown.

  8. Double-quantum-filtered 23Na NMR study of intracellular sodium in the perfused liver.

    PubMed Central

    Lyon, R C; McLaughlin, A C

    1994-01-01

    We acquired double-quantum-filtered 23Na NMR spectra from perfused liver, using a range of tau values from 0.2 to 24 ms, where tau is the separation between the first and second pi/2 pulses in the radio-frequency pulse sequence. For each tau value we compared the amplitude of the double-quantum-filtered 23Na NMR signal acquired from intracellular sodium ions when the liver was perfused with buffer containing the "shift reagent" Dy(PPP)2 to the amplitude of the total double-quantum-filtered 23Na NMR signal acquired when the liver was perfused with buffer containing no Dy(PPP)2. For tau < or = 4 ms, the average ratio of the two amplitudes was 0.98 +/- 0.03 (mean +/- SEM). For tau > or = 8 ms, the average ratio was significantly less than 1. These results demonstrate that double-quantum-filtered 23Na NMR signals acquired from perfused liver using short tau values arise almost exclusively from intracellular sodium ions, but double-quantum-filtered 23Na NMR signals acquired from perfused liver using long tau values contain contributions from both intracellular and extracellular sodium ions. This conclusion suggests that multiple-quantum-filtered 23Na NMR spectroscopy will be useful in studying intracellular sodium levels in the perfused liver, and possibly in the intact liver in vivo. PMID:7919009

  9. Low-power broadband solid-state MAS NMR of 14N

    NASA Astrophysics Data System (ADS)

    Pell, Andrew J.; Sanders, Kevin J.; Wegner, Sebastian; Pintacuda, Guido; Grey, Clare P.

    2017-05-01

    We propose two broadband pulse schemes for 14N solid-state magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) that achieves (i) complete population inversion and (ii) efficient excitation of the double-quantum spectrum using low-power single-sideband-selective pulses. We give a comprehensive theoretical description of both schemes using a common framework that is based on the jolting-frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983)]. This formalism is used to determine for the first time that we can obtain complete population inversion of 14N under low-power conditions, which we do here using single-sideband-selective adiabatic pulses. It is then used to predict that double-quantum coherences can be excited using low-power single-sideband-selective pulses. We then proceed to design a new experimental scheme for double-quantum excitation. The final double-quantum excitation pulse scheme is easily incorporated into other NMR experiments, as demonstrated here for double quantum-single quantum 14N correlation spectroscopy, and 1H-14N dipolar heteronuclear multiple-quantum correlation experiments. These pulses and irradiation schemes are evaluated numerically using simulations on single crystals and full powders, as well as experimentally on ammonium oxalate ((NH4)2C2O4) at moderate MAS and glycine at ultra-fast MAS. The performance of these new NMR methods is found to be very high, with population inversion efficiencies of 100% and double-quantum excitation efficiencies of 30%-50%, which are hitherto unprecedented for the low radiofrequency field amplitudes, up to the spinning frequency, that are used here.

  10. MAS-NMR at very high temperatures.

    PubMed

    van Wüllen, Leo; Schwering, Georg; Naumann, Ernst; Jansen, Martin

    2004-09-01

    We report MAS-NMR experiments at temperatures of approx. 1200 K using a CO(2) laser as the heating device. An internal NMR thermometer based on the (7)Li T1 data of Li(0.24)La(0.54)TiO(3) is used for temperature calibration. Using this setup, temperatures as high as 1191 K could be reached under MAS conditions as confirmed by the melting of Li(2)B(4)O(7) at 1191 K which could be followed by (7)Li-MAS-NMR.

  11. MAS NMR of HIV-1 protein assemblies

    NASA Astrophysics Data System (ADS)

    Suiter, Christopher L.; Quinn, Caitlin M.; Lu, Manman; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

    2015-04-01

    The negative global impact of the AIDS pandemic is well known. In this perspective article, the utility of magic angle spinning (MAS) NMR spectroscopy to answer pressing questions related to the structure and dynamics of HIV-1 protein assemblies is examined. In recent years, MAS NMR has undergone major technological developments enabling studies of large viral assemblies. We discuss some of these evolving methods and technologies and provide a perspective on the current state of MAS NMR as applied to the investigations into structure and dynamics of HIV-1 assemblies of CA capsid protein and of Gag maturation intermediates.

  12. Comparison of double-quantum NMR normalization schemes to measure homonuclear dipole-dipole interactions

    NASA Astrophysics Data System (ADS)

    Saalwächter, Kay

    2014-08-01

    A recent implementation of a double-quantum (DQ) recoupling solid-state NMR experiment, dubbed DQ-DRENAR, provides a quantitative measure of homonuclear dipole-dipole coupling constants in multispin-1/2 systems. It was claimed to be more robust than another, previously known experiment relying on the recording of point-by-point normalized DQ build-up curves. Focusing on the POST-C7 and BaBa-xy16 DQ pulse sequences, I here present an in-depth comparison of both approaches based upon spin-dynamics simulations, stressing that they are based upon very similar principles and that they are largely equivalent when no imperfections are present. With imperfections, it is found that DQ-DRENAR/POST-C7 does not fully compensate for additional signal dephasing related to chemical shifts (CS) and their anisotropy (CSA), which over-compensates the intrinsic CS(A)-related efficiency loss of the DQ Hamiltonian and leads to an apparent cancellation effect. The simulations further show that the CS(A)-related dephasing in DQ-DRENAR can be removed by another phase cycle step or an improved super-cycled wideband version. Only the latter, or the normalized DQ build-up, are unaffected by CS(A)-related signal loss and yield clean pure dipolar-coupling information subject to unavoidable, pulse sequence specific performance reduction related to higher-order corrections of the dipolar DQ Hamiltonian. The intrinsically super-cycled BaBa-xy16 is shown to exhibit virtually no CS(A) related imperfection terms, but its dipolar performance is somewhat more challenged by CS(A) effects than POST-C7, which can however be compensated when applied at very fast MAS (>50 kHz). Practically, DQ-DRENAR uses a clever phase cycle separation to achieve a significantly shorter experimental time, which can also be beneficially employed in normalized DQ build-up experiments.

  13. Comparison of double-quantum NMR normalization schemes to measure homonuclear dipole-dipole interactions

    SciTech Connect

    Saalwächter, Kay

    2014-08-14

    A recent implementation of a double-quantum (DQ) recoupling solid-state NMR experiment, dubbed DQ-DRENAR, provides a quantitative measure of homonuclear dipole-dipole coupling constants in multispin-1/2 systems. It was claimed to be more robust than another, previously known experiment relying on the recording of point-by-point normalized DQ build-up curves. Focusing on the POST-C7 and BaBa-xy16 DQ pulse sequences, I here present an in-depth comparison of both approaches based upon spin-dynamics simulations, stressing that they are based upon very similar principles and that they are largely equivalent when no imperfections are present. With imperfections, it is found that DQ-DRENAR/POST-C7 does not fully compensate for additional signal dephasing related to chemical shifts (CS) and their anisotropy (CSA), which over-compensates the intrinsic CS(A)-related efficiency loss of the DQ Hamiltonian and leads to an apparent cancellation effect. The simulations further show that the CS(A)-related dephasing in DQ-DRENAR can be removed by another phase cycle step or an improved super-cycled wideband version. Only the latter, or the normalized DQ build-up, are unaffected by CS(A)-related signal loss and yield clean pure dipolar-coupling information subject to unavoidable, pulse sequence specific performance reduction related to higher-order corrections of the dipolar DQ Hamiltonian. The intrinsically super-cycled BaBa-xy16 is shown to exhibit virtually no CS(A) related imperfection terms, but its dipolar performance is somewhat more challenged by CS(A) effects than POST-C7, which can however be compensated when applied at very fast MAS (>50 kHz). Practically, DQ-DRENAR uses a clever phase cycle separation to achieve a significantly shorter experimental time, which can also be beneficially employed in normalized DQ build-up experiments.

  14. A double quantum (129)Xe NMR experiment for probing xenon in multiply-occupied cavities of solid-state inclusion compounds.

    PubMed

    Brouwer, Darren H; Alavi, Saman; Ripmeester, John A

    2007-03-07

    A method is presented for detecting multiple xenon atoms in cavities of solid-state inclusion compounds using (129)Xe double quantum NMR spectroscopy. Double quantum filtered (129)Xe NMR spectra, performed on the xenon clathrate of Dianin's compound were obtained under high-resolution Magic-Angle Spinning (MAS) conditions, by recoupling the weak (129)Xe-(129)Xe dipole-dipole couplings that exist between xenon atoms in close spatial proximity. Because the (129)Xe-(129)Xe dipole-dipole couplings are generally weak due to dynamics of the atoms and to large internuclear separations, and since the (129)Xe Chemical Shift Anisotropy (CSA) tends to be relatively large, a very robust dipolar recoupling sequence was necessary, with the symmetry-based SR26 dipolar recoupling sequence proving appropriate. We have also attempted to measure the (129)Xe-(129)Xe dipole-dipole coupling constant between xenon atoms in the cavities of the xenon-Dianin's compound clathrate and have found that the dynamics of the xenon atoms (as investigated with molecular dynamics simulations) as well as (129)Xe multiple spin effects complicate the analysis. The double quantum NMR method is useful for peak assignment in (129)Xe NMR spectra because peaks arising from different types of absorption/inclusion sites or from different levels of occupancy of single sites can be distinguished. The method can also help resolve ambiguities in diffraction experiments concerning the order/disorder in a material.

  15. A software framework for analysing solid-state MAS NMR data.

    PubMed

    Stevens, Tim J; Fogh, Rasmus H; Boucher, Wayne; Higman, Victoria A; Eisenmenger, Frank; Bardiaux, Benjamin; van Rossum, Barth-Jan; Oschkinat, Hartmut; Laue, Ernest D

    2011-12-01

    Solid-state magic-angle-spinning (MAS) NMR of proteins has undergone many rapid methodological developments in recent years, enabling detailed studies of protein structure, function and dynamics. Software development, however, has not kept pace with these advances and data analysis is mostly performed using tools developed for solution NMR which do not directly address solid-state specific issues. Here we present additions to the CcpNmr Analysis software package which enable easier identification of spinning side bands, straightforward analysis of double quantum spectra, automatic consideration of non-uniform labelling schemes, as well as extension of other existing features to the needs of solid-state MAS data. To underpin this, we have updated and extended the CCPN data model and experiment descriptions to include transfer types and nomenclature appropriate for solid-state NMR experiments, as well as a set of experiment prototypes covering the experiments commonly employed by solid-sate MAS protein NMR spectroscopists. This work not only improves solid-state MAS NMR data analysis but provides a platform for anyone who uses the CCPN data model for programming, data transfer, or data archival involving solid-state MAS NMR data.

  16. Simulation studies of instrumental artifacts on spin I=1 double quantum filtered NMR spectroscopy

    PubMed Central

    Sun, Cheng; Boutis, Gregory S.

    2010-01-01

    We report on the results of a simulation based study of the effect of various experimental artifacts for spin I=1 double quantum filtered NMR. The simulation captures the effects of static field inhomogeneity, finite pulse widths, phase errors, transients and radio frequency inhomogeneity. We simulated the spectral distortions introduced under these errors for four, eight and sixteen step phase cycles that are well known in the NMR community. The dominating pulse errors are radio frequency field inhomogeneity and antisymmetric pulse transients. These errors result in the reduction of signal intensity as well as an introduction of distortions in the detected double quantum filtered spectrum. Using the simulation tool we studied the improvement one obtains when implementing a sixteen step phase cycle over a four step phase cycle. The results indicate that implementing a sixteen step phase cycle over an eight or four step phase cycle does not result in a significant reduction in the DQF intensity loss, or reduction in spectral distortions for antisymmetric transients. PMID:20451432

  17. Distribution and mobility of phosphates and sodium ions in cheese by solid-state 31P and double-quantum filtered 23Na NMR spectroscopy.

    PubMed

    Gobet, Mallory; Rondeau-Mouro, Corinne; Buchin, Solange; Le Quéré, Jean-Luc; Guichard, Elisabeth; Foucat, Loïc; Moreau, Céline

    2010-04-01

    The feasibility of solid-state magic angle spinning (MAS) (31)P nuclear magnetic resonance (NMR) spectroscopy and (23)Na NMR spectroscopy to investigate both phosphates and Na(+) ions distribution in semi-hard cheeses in a non-destructive way was studied. Two semi-hard cheeses of known composition were made with two different salt contents. (31)P Single-pulse excitation and cross-polarization MAS experiments allowed, for the first time, the identification and quantification of soluble and insoluble phosphates in the cheeses. The presence of a relatively 'mobile' fraction of colloidal phosphates was evidenced. The detection by (23)Na single-quantum NMR experiments of all the sodium ions in the cheeses was validated. The presence of a fraction of 'bound' sodium ions was evidenced by (23)Na double-quantum filtered NMR experiments. We demonstrated that NMR is a suitable tool to investigate both phosphates and Na(+) ions distributions in cheeses. The impact of the sodium content on the various phosphorus forms distribution was discussed and results demonstrated that NMR would be an important tool for the cheese industry for the processes controls.

  18. Low-power broadband homonuclear dipolar recoupling without decoupling: Double-quantum 13C NMR correlations at very fast magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Teymoori, Gholamhasan; Pahari, Bholanath; Stevensson, Baltzar; Edén, Mattias

    2012-09-01

    We report novel symmetry-based radio-frequency (rf) pulse sequences for efficient excitation of double-quantum (2Q) coherences under very fast (>60 kHz) magic-angle spinning (MAS) conditions. The recursively generated pulse-scheme series, R22p1R22p-1(p=1,2,3,…), offers broadband 13C-13C recoupling in organic solids at a very low rf power. No proton decoupling is required. A high-order average Hamiltonian theory analysis reveals a progressively enhanced resonance-offset compensation for increasing p, as verified both by numerical simulations and 2Q filtration NMR experiments on 13C2-glycine, [2,3-13C2]alanine, and [U-13C]tyrosine at 14.1 T and 66 kHz MAS, where the pulse schemes with p⩾3 compare favorably to current state-of-the-art recoupling options.

  19. Structural biology applications of solid state MAS DNP NMR

    NASA Astrophysics Data System (ADS)

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance.

  20. New openings for porous systems research from intermolecular double-quantum NMR.

    PubMed

    Capuani, S; Alesiani, M; Branca, R T; Maraviglia, B

    2004-01-01

    It has been recently recognized that residual intermolecular double-quantum coherences (iDQcs) provide a novel contrast mechanism to study heterogeneity in liquid systems. This is of much interest in the field of the physics of matter and biomedicine. Nowadays, literature concerning the behaviour of the iDQc signal originated by highly heterogeneous systems such as fluids in porous media is scarce. In this paper, we report and discuss our principal results about iDQc signal behaviour in confined liquid systems (trabecular bone, travertine, porous standard systems) and also some new results obtained on doped water in glass capillary pipes.

  1. Probing intermolecular interactions in a diethylcarbamazine citrate salt by fast MAS (1)H solid-state NMR spectroscopy and GIPAW calculations.

    PubMed

    Venâncio, Tiago; Oliveira, Lyege Magalhaes; Ellena, Javier; Boechat, Nubia; Brown, Steven P

    2017-03-02

    Fast magic-angle spinning (MAS) NMR is used to probe intermolecular interactions in a diethylcarbamazine salt, that is widely used as a treatment against adult worms of Wuchereria bancrofti which cause a common disease in tropical countries named filariasis. Specifically, a dihydrogen citrate salt that has improved thermal stability and solubility as compared to the free form is studied. One-dimensional (1)H, (13)C and (15)N and two-dimensional (1)H-(13)C and (14)N-(1)H heteronuclear correlation NMR experiments under moderate and fast MAS together with GIPAW (CASTEP) calculations enable the assignment of the (1)H, (13)C and (14)N/(15)N resonances. A two-dimensional (1)H-(1)H double-quantum (DQ) -single-quantum (SQ) MAS spectrum recorded with BaBa recoupling at 60kHz MAS identifies specific proton-proton proximities associated with citrate-citrate and citrate-diethylcarbamazine intermolecular interactions.

  2. Structural biology applications of solid state MAS DNP NMR.

    PubMed

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Lightweight hydrogen-storage material Mg(0.65)Sc(0.35)D2 studied with 2H and 2H-{45Sc} MAS NMR exchange spectroscopy.

    PubMed

    Srinivasan, S; Magusin, P C M M

    2011-01-01

    Using double-quantum (2)H MAS NMR with (45)Sc recoupling and Bloch-Siegert compensated (2)H-{(45)Sc} TRAPDOR we have identified the overlapping NMR signals of deuterium with and without scandium neighbors in Mg(0.65)Sc(0.35)D(2), a candidate lightweight material for hydrogen storage. At room temperature we also observe a third type of mobile deuterium. Deuterium mobility among the three NMR-distinct sites has been investigated by means of one-and two-dimensional exchange spectroscopy (Exsy). Complete deuterium exchange within 0.1s is observed, which indicates that the three NMR-distinct sites are close together in the crystal lattice. The weak temperature- and MAS-rate dependences observed in Exsy are indicative for a combination of chemical exchange and spin diffusion. Copyright © 2011 Elsevier Inc. All rights reserved.

  4. Effective Hamiltonians by optimal control: solid-state NMR double-quantum planar and isotropic dipolar recoupling.

    PubMed

    Tosner, Zdenek; Glaser, Steffen J; Khaneja, Navin; Nielsen, Niels Chr

    2006-11-14

    We report the use of optimal control algorithms for tailoring the effective Hamiltonians in nuclear magnetic resonance (NMR) spectroscopy through sophisticated radio-frequency (rf) pulse irradiation. Specifically, we address dipolar recoupling in solid-state NMR of powder samples for which case pulse sequences offering evolution under planar double-quantum and isotropic mixing dipolar coupling Hamiltonians are designed. The pulse sequences are constructed numerically to cope with a range of experimental conditions such as inhomogeneous rf fields, spread of chemical shifts, the intrinsic orientation dependencies of powder samples, and sample spinning. While the vast majority of previous dipolar recoupling sequences are operating through planar double-or zero-quantum effective Hamiltonians, we present here not only improved variants of such experiments but also for the first time homonuclear isotropic mixing sequences which transfers all I(x), I(y), and I(z) polarizations from one spin to the same operators on another spin simultaneously and with equal efficiency. This property may be exploited to increase the signal-to-noise ratio of two-dimensional experiments by a factor of square root 2 compared to conventional solid-state methods otherwise showing the same efficiency. The sequences are tested numerically and experimentally for a powder of (13)C(alpha),(13)C(beta)-L-alanine and demonstrate substantial sensitivity gains over previous dipolar recoupling experiments.

  5. Size-exclusion chromatographic NMR under HR-MAS.

    PubMed

    Lucena Alcalde, Guillermo; Anderson, Natalie; Day, Iain J

    2017-05-01

    The addition of stationary phases or sample modifiers can be used to modify the separation achievable in the diffusion domain of diffusion NMR experiments or provide information on the nature of the analyte-sample modifier interaction. Unfortunately, the addition of insoluble chromatographic stationary phases can lead to line broadening and degradation in spectral resolution, largely because of differences in magnetic susceptibility between the sample and the stationary phase. High-resolution magic angle spinning (HR-MAS) techniques can be used to remove this broadening. Here, we attempt the application of HR-MAS to size-exclusion chromatographic NMR with limited success. Observed diffusion coefficients for polymer molecular weight reference standards are shown to be larger than those obtained on static samples. Further investigation reveals that under HR-MAS it is possible to obtain reasonably accurate estimates of diffusion coefficients, using either full rotor synchronisation or sophisticated pulse sequences. The requirement for restricting the sample to the centre of the MAS rotor to ensure homogeneous magnetic and RF fields is also tested. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  6. High-resolution (19)F MAS NMR spectroscopy: structural disorder and unusual J couplings in a fluorinated hydroxy-silicate.

    PubMed

    Griffin, John M; Yates, Jonathan R; Berry, Andrew J; Wimperis, Stephen; Ashbrook, Sharon E

    2010-11-10

    High-resolution (19)F magic angle spinning (MAS) NMR spectroscopy is used to study disorder and bonding in a crystalline solid. (19)F MAS NMR reveals four distinct F sites in a 50% fluorine-substituted deuterated hydrous magnesium silicate (clinohumite, 4Mg(2)SiO(4)·Mg(OD(1-x)F(x))(2) with x = 0.5), indicating extensive structural disorder. The four (19)F peaks can be assigned using density functional theory (DFT) calculations of NMR parameters for a number of structural models with a range of possible local F environments generated by F(-)/OH(-) substitution. These assignments are supported by two-dimensional (19)F double-quantum MAS NMR experiments that correlate F sites based on either spatial proximity (via dipolar couplings) or through-bond connectivity (via scalar, or J, couplings). The observation of (19)F-(19)F J couplings is unexpected as the fluorines coordinate Mg atoms and the Mg-F interaction is normally considered to be ionic in character (i.e., there is no formal F-Mg-F covalent bonding arrangement). However, DFT calculations predict significant (19)F-(19)F J couplings, and these are in good agreement with the splittings observed in a (19)F J-resolved MAS NMR experiment. The existence of these J couplings is discussed in relation to both the nature of bonding in the solid state and the occurrence of so-called "through-space" (19)F-(19)F J couplings in solution. Finally, we note that we have found similar structural disorder and spin-spin interactions in both synthetic and naturally occurring clinohumite samples.

  7. Orientation-dependent proton double-quantum NMR build-up function for soft materials with anisotropic mobility.

    PubMed

    Naumova, Anna; Tschierske, Carsten; Saalwächter, Kay

    In recent years, the analysis of proton double-quantum NMR build-up curves has become an important tool to quantify anisotropic mobility in different kinds of soft materials such as polymer networks or liquid crystals. In the former case, such data provides a measure of orientation-dependent residual (time-averaged) dipolar couplings arising from anisotropic segmental motions, informing about the length and the state of local stretching of the network chains. Previous studies of macroscopically ordered, i.e. stretched, networks were subject to the limitation that a detailed build-up curve analysis on the basis of a universal "Abragam-like" (A-l) build-up function valid for a proton multi-spin system was only possible for an isotropic orientation-averaged response. This situation is here remedied by introducing a generic orientation-dependent build-up function for an anisotropically mobile protonated molecular segment. We discuss an application to the modeling of data for a stretched network measured at different orientations with respect to the magnetic field, and present a validation by fitting data of different liquid-crystal molecules oriented in the magnetic field.

  8. Insight into hydrogen bonding of uranyl hydroxide layers and capsules by use of 1H magic-angle spinning NMR spectroscopy [Insight into the hydrogen bonding for uranyl hydroxides using 1H MAS NMR spectroscopy

    DOE PAGES

    Alam, Todd M.; Liao, Zuolei; Nyman, May; ...

    2016-04-27

    Solid-state 1H magic-angle spinning (MAS) NMR was used to investigate local proton environments in anhydrous [UO2(OH)2] (α-UOH) and hydrated uranyl hydroxide [(UO2)4O(OH)6·5H2O (metaschoepite). For the metaschoepite material, proton resonances of the μ2-OH hydroxyl and interlayer waters were resolved, with two-dimensional (2D) double-quantum (DQ) 1H–1H NMR correlation experiments revealing strong dipolar interactions between these different proton species. The experimental NMR results were combined with first-principles CASTEP GIPAW (gauge including projector-augmented wave) chemical shift calculations to develop correlations between hydrogen-bond strength and observed 1H NMR chemical shifts. Furthermore, these NMR correlations allowed characterization of local hydrogen-bond environments in uranyl U24 capsules andmore » of changes in hydrogen bonding that occurred during thermal dehydration of metaschoepite.« less

  9. Magnetization-recovery experiments for static and MAS-NMR of I = 3/2 nuclei

    NASA Astrophysics Data System (ADS)

    Yesinowski, James P.

    2006-05-01

    Multifrequency pulsed NMR experiments on quadrupole-perturbed I = 3/2 spins in single crystals are shown to be useful for measuring spin-lattice relaxation parameters even for a mixture of quadrupolar plus magnetic relaxation mechanisms. Such measurements can then be related to other MAS-NMR experiments on powders. This strategy is demonstrated by studies of 71Ga and 69Ga (both I = 3/2) spin-lattice relaxation behavior in a single-crystal (film) sample of gallium nitride, GaN, at various orientations of the axially symmetric nuclear quadrupole coupling tensor. Observation of apparent single-exponential relaxation behavior in I = 3/2 saturation-recovery experiments can be misleading when individual contributing rate processes are neglected in the interpretation. The quadrupolar mechanism (dominant in this study) has both a single-quantum process ( T1Q1) and a double-quantum process ( T1Q2), whose time constants are not necessarily equal. Magnetic relaxation (in this study most likely arising from hyperfine couplings to unpaired delocalized electron spins in the conduction band) also contributes to a single-quantum process ( T1M). A strategy of multifrequency irradiation with observation of satellite and/or central transitions, incorporating different initial conditions for the level populations, provides a means of obtaining these three relaxation time constants from single-crystal 71Ga data alone. The 69Ga results provide a further check of internal consistency, since magnetic and quadrupolar contributions to its relaxation scale in opposite directions compared to 71Ga. For both perpendicular and parallel quadrupole coupling tensor symmetry axis orientations small but significant differences between T1Q1 and T1Q2 were measured, whereas for a tensor symmetry axis oriented at the magic-angle (54.74°) the values were essentially equal. Magic-angle spinning introduces a number of complications into the measurement and interpretation of the spin-lattice relaxation

  10. Rapid acquisition of wideline MAS solid-state NMR spectra with fast MAS, proton detection, and dipolar HMQC pulse sequences.

    PubMed

    Rossini, Aaron J; Hanrahan, Michael P; Thuo, Martin

    2016-09-14

    The solid-state NMR spectra of many NMR active elements are often extremely broad due to the presence of chemical shift anisotropy (CSA) and/or the quadrupolar interaction (for nuclei with spin I > 1/2). These NMR interactions often give rise to wideline solid-state NMR spectra which can span hundreds of kHz or several MHz. Here we demonstrate that by using fast MAS, proton detection and dipolar hetero-nuclear multiple-quantum (D-HMQC) pulse sequences, it is possible to rapidly acquire 2D spectra which correlate (1)H chemical shifts to the indirectly detected wideline MAS powder patterns of dipolar coupled hetero-nuclei. The D-HMQC pulse sequence enables broadband excitation of the wideline hetero-nuclear NMR spectrum and provides higher sensitivity by detecting the narrower and more sensitive (1)H NMR signal. This approach is demonstrated for the rapid acquisition of 2D (1)H detected (195)Pt solid-state NMR spectra of cisplatin and transplatin and the (71)Ga solid-state NMR spectrum of a self-assembled Ga coordination polymer of unconfirmed structure. This approach should be broadly applicable for the rapid acquisition of wideline MAS solid-state NMR spectra of moderately abundant NMR nuclei.

  11. Glycerin-Induced Conformational Changes in Bombyx mori Silk Fibroin Film Monitored by (13)C CP/MAS NMR and ¹H DQMAS NMR.

    PubMed

    Asakura, Tetsuo; Endo, Masanori; Hirayama, Misaki; Arai, Hiroki; Aoki, Akihiro; Tasei, Yugo

    2016-09-09

    In order to improve the stiff and brittle characteristics of pure Bombyx mori (B. mori) silk fibroin (SF) film in the dry state, glycerin (Glyc) has been used as a plasticizer. However, there have been very limited studies on the structural characterization of the Glyc-blended SF film. In this study, (13)C Cross Polarization/Magic Angle Spinning nuclear magnetic resonance (CP/MAS NMR) was used to monitor the conformational changes in the films by changing the Glyc concentration. The presence of only 5 wt % Glyc in the film induced a significant conformational change in SF where Silk I* (repeated type II β-turn and no α-helix) newly appeared. Upon further increase in Glyc concentration, the percentage of Silk I* increased linearly up to 9 wt % Glyc and then tended to be almost constant (30%). This value (30%) was the same as the fraction of Ala residue within the Silk I* form out of all Ala residues of SF present in B. mori mature silkworm. The ¹H DQMAS NMR spectra of Glyc-blended SF films confirmed the appearance of Silk I* in the Glyc-blended SF film. A structural model of Glyc-SF complex including the Silk I* form was proposed with the guidance of the Molecular Dynamics (MD) simulation using ¹H-¹H distance constraints obtained from the ¹H Double-Quantum Magic Angle Spinning (DQMAS) NMR spectra.

  12. Glycerin-Induced Conformational Changes in Bombyx mori Silk Fibroin Film Monitored by 13C CP/MAS NMR and 1H DQMAS NMR

    PubMed Central

    Asakura, Tetsuo; Endo, Masanori; Hirayama, Misaki; Arai, Hiroki; Aoki, Akihiro; Tasei, Yugo

    2016-01-01

    In order to improve the stiff and brittle characteristics of pure Bombyx mori (B. mori) silk fibroin (SF) film in the dry state, glycerin (Glyc) has been used as a plasticizer. However, there have been very limited studies on the structural characterization of the Glyc-blended SF film. In this study, 13C Cross Polarization/Magic Angle Spinning nuclear magnetic resonance (CP/MAS NMR) was used to monitor the conformational changes in the films by changing the Glyc concentration. The presence of only 5 wt % Glyc in the film induced a significant conformational change in SF where Silk I* (repeated type II β-turn and no α-helix) newly appeared. Upon further increase in Glyc concentration, the percentage of Silk I* increased linearly up to 9 wt % Glyc and then tended to be almost constant (30%). This value (30%) was the same as the fraction of Ala residue within the Silk I* form out of all Ala residues of SF present in B. mori mature silkworm. The 1H DQMAS NMR spectra of Glyc-blended SF films confirmed the appearance of Silk I* in the Glyc-blended SF film. A structural model of Glyc-SF complex including the Silk I* form was proposed with the guidance of the Molecular Dynamics (MD) simulation using 1H–1H distance constraints obtained from the 1H Double-Quantum Magic Angle Spinning (DQMAS) NMR spectra. PMID:27618034

  13. Ammonia Vapor Removal by Cu3(BTC)2 and Its Characterization by MAS NMR

    DTIC Science & Technology

    2009-01-01

    REPORT Ammonia Vapor Removal by Cu3(BTC)2 and Its Characterization by MAS NMR 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: Adsorption equilibria and...NMR experiments were performed to study the adsorption and interactions of ammonia with metal-organic framework HKUST-1, or Cu3(BTC)2 (BTC ) 1,3,5... adsorption alone, suggesting a stronger interaction involving a potential reaction with the Cu3(BTC)2 framework. Indeed, 1H MAS NMR reveals that a major

  14. Sealed rotors for in situ high temperature high pressure MAS NMR

    SciTech Connect

    Hu, Jian Z.; Hu, Mary Y.; Zhao, Zhenchao; Xu, Souchang; Vjunov, Aleksei; Shi, Hui; Camaioni, Donald M.; Peden, Charles H. F.; Lercher, Johannes A.

    2015-07-06

    Magic angle spinning (MAS) nuclear magnetic resonance (NMR) investigations on heterogeneous samples containing solids, semi-solids, liquid and gases or a mixture of them under non-conventional conditions of a combined high pressure and high temperature, or cold temperature suffer from the unavailability of a perfectly sealed rotor. Here, we report the design of reusable and perfectly-sealed all-zircornia MAS rotors. The rotors are easy to use and are suitable for operation temperatures from below 0 to 250 °C and pressures up to 100 bar. As an example of potential applications we performed in situ MAS NMR investigations of AlPO₄-5 molecular sieve crystallization, a kinetic study of the cyclohexanol dehydration reaction using 13C MAS NMR, and an investigation of the metabolomics of intact biological tissue at low temperature using 1H HR-MAS NMR spectroscopy. The in situ MAS NMR experiments performed using the reported rotors allowed reproduction of the results from traditional batch reactions, while offering more detailed quantitative information at the molecular level, as demonstrated for the molecular sieve synthesis and activation energy measurements for cyclohexanol dehydration. The perfectly sealed rotor also shows promising application for metabolomics studies using 1H HR-MAS NMR.

  15. Sealed rotors for in situ high temperature high pressure MAS NMR

    DOE PAGES

    Hu, Jian Z.; Hu, Mary Y.; Zhao, Zhenchao; ...

    2015-07-06

    Magic angle spinning (MAS) nuclear magnetic resonance (NMR) investigations on heterogeneous samples containing solids, semi-solids, liquid and gases or a mixture of them under non-conventional conditions of a combined high pressure and high temperature, or cold temperature suffer from the unavailability of a perfectly sealed rotor. Here, we report the design of reusable and perfectly-sealed all-zircornia MAS rotors. The rotors are easy to use and are suitable for operation temperatures from below 0 to 250 °C and pressures up to 100 bar. As an example of potential applications we performed in situ MAS NMR investigations of AlPO₄-5 molecular sieve crystallization,more » a kinetic study of the cyclohexanol dehydration reaction using 13C MAS NMR, and an investigation of the metabolomics of intact biological tissue at low temperature using 1H HR-MAS NMR spectroscopy. The in situ MAS NMR experiments performed using the reported rotors allowed reproduction of the results from traditional batch reactions, while offering more detailed quantitative information at the molecular level, as demonstrated for the molecular sieve synthesis and activation energy measurements for cyclohexanol dehydration. The perfectly sealed rotor also shows promising application for metabolomics studies using 1H HR-MAS NMR.« less

  16. Deuterium MAS NMR studies of dynamics on multiple timescales: histidine and oxalic acid.

    PubMed

    Chan-Huot, Monique; Wimperis, Stephen; Gervais, Christel; Bodenhausen, Geoffrey; Duma, Luminita

    2015-01-12

    Deuterium ((2) H) magic-angle spinning (MAS) nuclear magnetic resonance is applied to monitor the dynamics of the exchanging labile deuterons of polycrystalline L-histidine hydrochloride monohydrate-d7 and α-oxalic acid dihydrate-d6 . Direct experimental evidence of fast dynamics is obtained from T1Z and T1Q measurements. Further motional information is extracted from two-dimensional single-quantum (SQ) and double-quantum (DQ) MAS spectra. Differences between the SQ and DQ linewidths clearly indicate the presence of motions on intermediate timescales for the carboxylic moiety and the D2 O in α-oxalic acid dihydrate, and for the amine group and the D2 O in L-histidine hydrochloride monohydrate. Comparison of the relaxation rate constants of Zeeman and quadrupolar order with the relaxation rate constants of the DQ coherences suggests the co-existence of fast and slow motional processes.

  17. Multiple quantum filtered 23Na NMR in the Langendorff perfused mouse heart: Ratio of triple/double quantum filtered signals correlates with [Na]i

    PubMed Central

    Eykyn, Thomas R.; Aksentijević, Dunja; Aughton, Karen L.; Southworth, Richard; Fuller, William; Shattock, Michael J.

    2015-01-01

    We investigate the potential of multiple quantum filtered (MQF) 23Na NMR to probe intracellular [Na]i in the Langendorff perfused mouse heart. In the presence of Tm(DOTP) shift reagent the triple quantum filtered (TQF) signal originated largely from the intracellular sodium pool with a 32 ± 6% contribution of the total TQF signal arising from extracellular sodium, whilst the rank 2 double-quantum filtered signal (DQF), acquired with a 54.7° flip-angle pulse, originated exclusively from the extracellular sodium pool. Given the different cellular origins of the 23Na MQF signals we propose that the TQF/DQF ratio can be used as a semi-quantitative measure of [Na]i in the mouse heart. We demonstrate a good correlation of this ratio with [Na]i measured with shift reagent at baseline and under conditions of elevated [Na]i. We compare the measurements of [Na]i using both shift reagent and TQF/DQF ratio in a cohort of wild type mouse hearts and in a transgenic PLM3SA mouse expressing a non-phosphorylatable form of phospholemman, showing a modest but measurable elevation of baseline [Na]i. MQF filtered 23Na NMR is a potentially useful tool for studying normal and pathophysiological changes in [Na]i, particularly in transgenic mouse models with altered Na regulation. PMID:26196304

  18. Multiple quantum filtered (23)Na NMR in the Langendorff perfused mouse heart: Ratio of triple/double quantum filtered signals correlates with [Na]i.

    PubMed

    Eykyn, Thomas R; Aksentijević, Dunja; Aughton, Karen L; Southworth, Richard; Fuller, William; Shattock, Michael J

    2015-09-01

    We investigate the potential of multiple quantum filtered (MQF) (23)Na NMR to probe intracellular [Na]i in the Langendorff perfused mouse heart. In the presence of Tm(DOTP) shift reagent the triple quantum filtered (TQF) signal originated largely from the intracellular sodium pool with a 32±6% contribution of the total TQF signal arising from extracellular sodium, whilst the rank 2 double-quantum filtered signal (DQF), acquired with a 54.7° flip-angle pulse, originated exclusively from the extracellular sodium pool. Given the different cellular origins of the (23)Na MQF signals we propose that the TQF/DQF ratio can be used as a semi-quantitative measure of [Na]i in the mouse heart. We demonstrate a good correlation of this ratio with [Na]i measured with shift reagent at baseline and under conditions of elevated [Na]i. We compare the measurements of [Na]i using both shift reagent and TQF/DQF ratio in a cohort of wild type mouse hearts and in a transgenic PLM(3SA) mouse expressing a non-phosphorylatable form of phospholemman, showing a modest but measurable elevation of baseline [Na]i. MQF filtered (23)Na NMR is a potentially useful tool for studying normal and pathophysiological changes in [Na]i, particularly in transgenic mouse models with altered Na regulation.

  19. Temperature calibration for high-temperature MAS NMR to 913 K: 63Cu MAS NMR of CuBr and CuI, and 23Na MAS NMR of NaNbO3.

    PubMed

    Wu, Jingshi; Kim, Namjun; Stebbins, Jonathan F

    2011-09-01

    The solid-state phase transitions of CuBr, CuI and NaNbO(3) can be readily observed using (63)Cu and (23)Na high-temperature magic-angle spinning nuclear magnetic resonance spectroscopy. Temperature has large, linear effects on the peak maximum of (63)Cu in each solid phase of CuBr and CuI, and there is large jump in shift across each phase transition. The (23)Na MAS NMR peak intensities and the line widths in NaNbO(3) also clearly show its high-temperature transition to the cubic phase. These data can be used to calibrate high-temperature MAS NMR probes up to 913 K, which is two hundred degrees higher than the commonly-used temperature calibration based on the chemical shift of (207)Pb in Pb(NO(3))(2). Copyright © 2011 Elsevier Inc. All rights reserved.

  20. (1)H HR-MAS NMR-based metabolomics analysis for dry-fermented sausage characterization.

    PubMed

    García-García, Ana Belén; Lamichhane, Santosh; Castejón, David; Cambero, Mª Isabel; Bertram, Hanne Christine

    2018-02-01

    Proton high-resolution magic angle spinning ((1)H HR-MAS) nuclear magnetic resonance (NMR) spectroscopy in combination with principal component analysis (PCA) was employed to characterize dry-fermented sausages salchichón type throughout the manufacturing process. (1)H HR-MAS NMR metabolite profiling was achieved from a small sample of intact sausage after 0, 2, 4, 7, 11 and 14days of drying. Intriguingly, the obtained results enabled the identification of the three main stages in the traditional production of salchichón. Formulation, fermentation and drying-ripening periods showed distinct and characteristic metabolomic profiles. Compositional changes related to microbial activity, as well as proteolytic and lipolytic phenomena, decisive steps in such a ripening process, could be monitored through the NMR spectra. This study shows the potential of (1)H HR-MAS as a rapid method for probing metabolomic profiles and compositional changes during sausages processing. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Factor analysis of 27Al MAS NMR spectra for identifying nanocrystalline phases in amorphous geopolymers.

    PubMed

    Urbanova, Martina; Kobera, Libor; Brus, Jiri

    2013-11-01

    Nanostructured materials offer enhanced physicochemical properties because of the large interfacial area. Typically, geopolymers with specifically synthesized nanosized zeolites are a promising material for the sorption of pollutants. The structural characterization of these aluminosilicates, however, continues to be a challenge. To circumvent complications resulting from the amorphous character of the aluminosilicate matrix and from the low concentrations of nanosized crystallites, we have proposed a procedure based on factor analysis of (27)Al MAS NMR spectra. The capability of the proposed method was tested on geopolymers that exhibited various tendencies to crystallize (i) completely amorphous systems, (ii) X-ray amorphous systems with nanocrystalline phases, and (iii) highly crystalline systems. Although the recorded (27)Al MAS NMR spectra did not show visible differences between the amorphous systems (i) and the geopolymers with the nanocrystalline phase (ii), the applied factor analysis unambiguously distinguished these materials. The samples were separated into the well-defined clusters, and the systems with the evolving crystalline phase were identified even before any crystalline fraction was detected by X-ray powder diffraction. Reliability of the proposed procedure was verified by comparing it with (29)Si MAS NMR spectra. Factor analysis of (27)Al MAS NMR spectra thus has the ability to reveal spectroscopic features corresponding to the nanocrystalline phases. Because the measurement time of (27)Al MAS NMR spectra is significantly shorter than that of (29)Si MAS NMR data, the proposed procedure is particularly suitable for the analysis of large sets of specifically synthesized geopolymers in which the formation of the limited fractions of nanocrystalline phases is desired.

  2. Pulsed field gradient multiple-quantum MAS NMR spectroscopy of half-integer spin quadrupolar nuclei

    NASA Astrophysics Data System (ADS)

    Fyfe, C. A.; Skibsted, J.; Grondey, H.; Meyer zu Altenschildesche, H.

    1997-12-01

    Pulsed field gradients (PFGs) have been applied to select coherence transfer pathways in multiple-quantum (MQ) MAS NMR spectra of half-integer spin quadrupolar nuclei in rigid solids. 27Al triple-quantum (3Q) MAS NMR spectra of the aluminophosphate molecular sieves VPI-5 and AlPO 4-18 have been used to demonstrate the selection of the (0)→(3)→(-1) coherence transfer pathway using PFGs and no phase cycling. Compared to MQMAS experiments that employ phase cycling schemes, the main advantage of the PFG-MQMAS technique is its simplicity, which should facilitate the combination of MQMAS with other pulse sequences.

  3. Advanced instrumentation for DNP-enhanced MAS NMR for higher magnetic fields and lower temperatures

    NASA Astrophysics Data System (ADS)

    Matsuki, Yoh; Idehara, Toshitaka; Fukazawa, Jun; Fujiwara, Toshimichi

    2016-03-01

    Sensitivity enhancement of MAS NMR using dynamic nuclear polarization (DNP) is gaining importance at moderate fields (B0 < 9 T) and temperatures (T > 90 K) with potential applications in chemistry and material sciences. However, considering the ever-increasing size and complexity of the systems to be studied, it is crucial to establish DNP under higher field conditions, where the spectral resolution and the basic NMR sensitivity tend to improve. In this perspective, we overview our recent efforts on hardware developments, specifically targeted on improving DNP MAS NMR at high fields. It includes the development of gyrotrons that enable continuous frequency tuning and rapid frequency modulation for our 395 GHz-600 MHz and 460 GHz-700 MHz DNP NMR spectrometers. The latter 700 MHz system involves two gyrotrons and a quasi-optical transmission system that combines two independent sub-millimeter waves into a single dichromic wave. We also describe two cryogenic MAS NMR probe systems operating, respectively, at T ∼100 K and ∼30 K. The latter system utilizes a novel closed-loop helium recirculation mechanism, achieving cryogenic MAS without consuming any cryogen. These instruments altogether should promote high-field DNP toward more efficient, reliable and affordable technology. Some experimental DNP results obtained with these instruments are presented.

  4. Advanced instrumentation for DNP-enhanced MAS NMR for higher magnetic fields and lower temperatures.

    PubMed

    Matsuki, Yoh; Idehara, Toshitaka; Fukazawa, Jun; Fujiwara, Toshimichi

    2016-03-01

    Sensitivity enhancement of MAS NMR using dynamic nuclear polarization (DNP) is gaining importance at moderate fields (B0<9T) and temperatures (T>90K) with potential applications in chemistry and material sciences. However, considering the ever-increasing size and complexity of the systems to be studied, it is crucial to establish DNP under higher field conditions, where the spectral resolution and the basic NMR sensitivity tend to improve. In this perspective, we overview our recent efforts on hardware developments, specifically targeted on improving DNP MAS NMR at high fields. It includes the development of gyrotrons that enable continuous frequency tuning and rapid frequency modulation for our 395 GHz-600 MHz and 460 GHz-700 MHz DNP NMR spectrometers. The latter 700 MHz system involves two gyrotrons and a quasi-optical transmission system that combines two independent sub-millimeter waves into a single dichromic wave. We also describe two cryogenic MAS NMR probe systems operating, respectively, at T ∼ 100K and ∼ 30K. The latter system utilizes a novel closed-loop helium recirculation mechanism, achieving cryogenic MAS without consuming any cryogen. These instruments altogether should promote high-field DNP toward more efficient, reliable and affordable technology. Some experimental DNP results obtained with these instruments are presented. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  5. Slow-spinning low-sideband HR-MAS NMR spectroscopy: delicate analysis of biological samples

    PubMed Central

    Renault, Marie; Shintu, Laetitia; Piotto, Martial; Caldarelli, Stefano

    2013-01-01

    High-Resolution Magic-Angle Spinning (HR-MAS) NMR spectroscopy has become an extremely versatile analytical tool to study heterogeneous systems endowed with liquid-like dynamics. Spinning frequencies of several kHz are however required to obtain NMR spectra, devoid of spinning sidebands, with a resolution approaching that of purely isotropic liquid samples. An important limitation of the method is the large centrifugal forces that can damage the structure of the sample. In this communication, we show that optimizing the sample preparation, particularly avoiding air bubbles, and the geometry of the sample chamber of the HR-MAS rotor leads to high-quality low-sideband NMR spectra even at very moderate spinning frequencies, thus allowing the use of well-established solution-state NMR procedures for the characterization of small and highly dynamic molecules in the most fragile samples, such as live cells and intact tissues. PMID:24284435

  6. Optimized multiple quantum MAS lineshape simulations in solid state NMR

    NASA Astrophysics Data System (ADS)

    Brouwer, William J.; Davis, Michael C.; Mueller, Karl T.

    2009-10-01

    /Linux Operating system: UNIX/Linux Has the code been vectorised or parallelized?: Yes RAM: Example: (1597 powder angles) × (200 Samples) × (81 F2 frequency pts) × (31 F1 frequency points) = 3.5M, SMP AMD opteron Classification: 2.3 External routines: OCTAVE ( http://www.gnu.org/software/octave/), GNU Scientific Library ( http://www.gnu.org/software/gsl/), OPENMP ( http://openmp.org/wp/) Nature of problem: The optimal simulation and modeling of multiple quantum magic angle spinning NMR spectra, for general systems, especially those with mild to significant disorder. The approach outlined and implemented in C and OCTAVE also produces model parameter error estimates. Solution method: A model for each distinct chemical site is first proposed, for the individual contribution of crystallite orientations to the spectrum. This model is averaged over all powder angles [1], as well as the (stochastic) parameters; isotropic chemical shift and quadrupole coupling constant. The latter is accomplished via sampling from a bi-variate Gaussian distribution, using the Box-Muller algorithm to transform Sobol (quasi) random numbers [2]. A simulated annealing optimization is performed, and finally the non-linear jackknife [3] is applied in developing model parameter error estimates. Additional comments: The distribution contains a script, mqmasOpt.m, which runs in the OCTAVE language workspace. Running time: Example: (1597 powder angles) × (200 Samples) × (81 F2 frequency pts) × (31 F1 frequency points) = 58.35 seconds, SMP AMD opteron. References:S.K. Zaremba, Annali di Matematica Pura ed Applicata 73 (1966) 293. H. Niederreiter, Random Number Generation and Quasi-Monte Carlo Methods, SIAM, 1992. T. Fox, D. Hinkley, K. Larntz, Technometrics 22 (1980) 29.

  7. High-field (95) Mo and (183) W static and MAS NMR study of polyoxometalates.

    PubMed

    Haouas, Mohamed; Trébosc, Julien; Roch-Marchal, Catherine; Cadot, Emmanuel; Taulelle, Francis; Martineau-Corcos, Charlotte

    2017-10-01

    The potential of high-field NMR to measure solid-state (95) Mo and (183) W NMR in polyoxometalates (POMs) is explored using some archetypical structures like Lindqvist, Keggin and Dawson as model compounds that are well characterized in solution. NMR spectra in static and under magic angle spinning (MAS) were obtained, and their analysis allowed extraction of the NMR parameters, including chemical shift anisotropy and quadrupolar coupling parameters. Despite the inherent difficulties of measurement in solid state of these low-gamma NMR nuclei, due mainly to the low spectral resolution and poor signal-to-noise ratio, the observed global trends compare well with the solution-state NMR data. This would open an avenue for application of solid-state NMR to POMs, especially when liquid-state NMR is not possible, e.g., for poorly soluble or unstable compounds in solution, and for giant molecules with slow tumbling motion. This is the case of Keplerate where we provide here the first NMR characterization of this class of POMs in the solid state. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  8. Using heat to control the sample spinning speed in MAS NMR.

    PubMed

    Mihaliuk, Eugene; Gullion, Terry

    2011-10-01

    A new approach using temperature to control the spinning speed of a sample rotor in magic-angle spinning NMR is presented. Instead of an electro-mechanical valve that regulates the flow of drive gas to control the spinning speed in traditional MAS NMR systems, we use a small heater wire located directly in the stator. The sample spinning speed is controlled very accurately with a surprisingly low heating power of 1 W. Results on a benchtop unit demonstrate the capability of the system.

  9. Multiple-quantum cross-polarization in MAS NMR of quadrupolar nuclei

    NASA Astrophysics Data System (ADS)

    Ashbrook, Sharon E.; Brown, Steven P.; Wimperis, Stephen

    1998-05-01

    Using 27Al ( I=5/2) NMR of aluminium acetylacetonate, we show that it is possible to cross-polarize from a spin I=1/2 nucleus ( 1H) directly to the central triple-quantum transition of a half-integer quadrupolar nucleus ( 27Al) in a powdered sample under MAS conditions. The optimum conditions for this multiple-quantum cross-polarization (MQCP) are investigated experimentally and compared with existing theoretical results. The new technique is applied to the recently introduced two-dimensional MQMAS experiment for recording high-resolution NMR spectra of half-integer quadrupolar nuclei.

  10. 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.

  11. 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.

  12. In Situ Characterization of Pharmaceutical Formulations by Dynamic Nuclear Polarization Enhanced MAS NMR.

    PubMed

    Ni, Qing Zhe; Yang, Fengyuan; Can, Thach V; Sergeyev, Ivan V; D'Addio, Suzanne M; Jawla, Sudheer K; Li, Yongjun; Lipert, Maya P; Xu, Wei; Williamson, R Thomas; Leone, Anthony; Griffin, Robert G; Su, Yongchao

    2017-08-31

    A principal advantage of magic angle spinning (MAS) NMR spectroscopy lies in its ability to determine molecular structure in a noninvasive and quantitative manner. Accordingly, MAS should be widely applicable to studies of the structure of active pharmaceutical ingredients (API) and formulations. However, the low sensitivity encountered in spectroscopy of natural abundance APIs present at low concentration has limited the success of MAS experiments. Dynamic nuclear polarization (DNP) enhances NMR sensitivity and can be used to circumvent this problem provided that suitable paramagnetic polarizing agent can be incorporated into the system without altering the integrity of solid dosages. Here, we demonstrate that DNP polarizing agents can be added in situ during the preparation of amorphous solid dispersions (ASDs) via spray drying and hot-melt extrusion so that ASDs can be examined during drug development. Specifically, the dependence of DNP enhancement on sample composition, radical concentration, relaxation properties of the API and excipients, types of polarizing agents and proton density, has been thoroughly investigated. Optimal enhancement values are obtained from ASDs containing 1% w/w radical concentration. Both polarizing agents TOTAPOL and AMUPol provided reasonable enhancements. Partial deuteration of the excipient produced 3× higher enhancement values. With these parameters, an ASD containing posaconazole and vinyl acetate yields a 32-fold enhancement which presumably results in a reduction of NMR measurement time by ∼1000. This boost in signal intensity enables the full assignment of the natural abundance pharmaceutical formulation through multidimensional correlation experiments.

  13. Estimation of the specific surface area of apatites in human mineralized tissues using 31P MAS NMR.

    PubMed

    Kolmas, Joanna; Slósarczyk, Anna; Wojtowicz, Andrzej; Kolodziejski, Waclaw

    2007-10-01

    Specific surface areas of apatites in whole human mineralized tissues were estimated from (31)P MAS NMR linewidths: 77 m(2)g(-1) for enamel and 94 m(2)g(-1) for dentin, dental cementum and cortical bone.

  14. (11)B MAS NMR and First-Principles Study of the [OBO3] Pyramids in Borates.

    PubMed

    Zhou, Bing; Sun, Wei; Zhao, Biao-Chun; Mi, Jin-Xiao; Laskowski, Robert; Terskikh, Victor; Zhang, Xi; Yang, Lingyun; Botis, Sanda M; Sherriff, Barbara L; Pan, Yuanming

    2016-03-07

    Borates are built from the [Bϕ3] planar triangles and the [Bϕ4] tetrahedral groups, where ϕ denotes O or OH. However, the [Bϕ4] groups in some borates are highly distorted to include three normal B-O bonds and one anomalously long B-O bond and, therefore, are best described as the [OBO3] pyramids. Four synthetic borates of the boracite-type structures (Mg3B7O13Br, Cu3B7O13Br, Zn3B7O13Cl, and Mg3B7O13Cl) containing a range of [OBO3] pyramids were investigated by multifield (7.05, 14.1, and 21.1 T) (11)B magic-angle spinning nuclear magnetic resonance (MAS NMR), triple quantum (3Q) MAS NMR experiments, as well as density functional theory calculations. The high-resolution (11)B MAS NMR spectra supported by theoretical predictions show that the [OBO3] pyramids are characterized by isotropic chemical shifts δiso((11)B) from 1.4(1) to 4.9(1) ppm and nuclear quadrupole parameters CQ((11)B) up to 1.3(1) MHz, both significantly different from those of the [BO4] and [BO3] groups in borates. These δiso((11)B) and CQ((11)B) values indicate that the [OBO3] pyramids represent an intermediate state between the [BO4] tetrahedra and [BO3] triangles and demonstrate that the (11)B NMR parameters of four-coordinate boron oxyanions are sensitive to local structural environments. The orientation of the calculated unique electronic field gradient tensor element Vzz of the [OBO3] pyramids is aligned approximately along the direction of the anomalously long B-O bond, corresponding to B-2pz with the lowest electron density.

  15. A 29Si MAS-NMR study of transition metal site occupancy in forsterite

    NASA Astrophysics Data System (ADS)

    Mccarty, R. J.; Palke, A.; Stebbins, J. F.; Hartman, S.

    2012-12-01

    In this study, we address the problem of transition metal site occupancy in Mg-rich olivine using solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Transition metal substitution in olivine can occur in either of the two crystallographically unique octahedral sites: the smaller, more symmetric M1 site or the larger, more distorted M2 site. Site occupancy of the transition metal is expected to correlate with ionic radius and d-orbital structure. In NMR spectroscopy the presence of paramagnetic ions, such as transition metal ions, can produce accessory peaks referred to as "contact shifts," due to the interaction between unpaired electrons on the paramagnetic ion locally associated with the resonating nucleus. The position and intensity of the contact shifts are dependent on the geometrical association such as bond distances and bond angles between the paramagnetic ion and the resonating nucleus. 29Si MAS-NMR spectra collected on synthetic forsterite (Mg2SiO4) doped with minor amounts (0.2-5%) of individual, divalent, paramagnetic, transition metal cations (Mn, Co, Ni, or Cu) substituting for Mg in the octahedral sites, reveals multiple contact shifts. An interpretation of the number of such contact shifts and their relative intensities correlated with structural information of possible 29Si-M1 and 29Si-M2 configurations, potentially allows for the assignment of specific transition metals to individual M1 or M2 sites. An analysis of the MAS-NMR data will potentially bring a new level of confidence to transition metal site occupancy in forsterite.

  16. Distance measurements in disodium ATP hydrates by means of 31P double quantum two-dimensional solid-state NMR spectroscopy.

    PubMed

    Potrzebowski, M J; Gajda, J; Ciesielski, W; Montesinos, I M

    2006-04-01

    POST-C7 measurements provide constraints allowing distinguishing crystal lattice organization and establishing intra and/or intermolecular distances between phosphorus atoms of triphosphate chains for different hydrates of disodium ATP salts. Double-quantum efficiency in function of excitation time obtained from series of two-dimensional spectra for POST-C7 experiments was used to set up of buildup curves and semi-quantitative measure of 31P-31P length.

  17. Increasing 13C CP-MAS NMR resolution using single crystals: application to model octaethyl porphyrins.

    PubMed

    Dugar, Sneha; Fu, Riqiang; Dalal, Naresh S

    2012-08-02

    Octaethyl porphyrin (OEP) and its Ni and Zn derivatives are considered as model compounds in biochemical, photophysical, and fossil fuel chemistry. They have thus been investigated by high-resolution solid-state (13)C NMR using powders, but peak assignment has been difficult because of large line widths. Arguing that a significant cause of broadening might be the anisotropic bulk magnetic susceptibility, we utilized single crystals in our (13)C cross-polarization magic angle spinning (CP-MAS) measurements and observed a nearly 2-fold line narrowing. This enhanced resolution enabled us to assign chemical shifts to each carbon for all the three compounds. The new assignments are now in agreement with X-ray structural data and allowed us to probe the motional dynamics of the methyl and methylene carbons of the OEP side chains. It is apparent that the use of single crystals in (13)C CP-MAS measurements has a significantly wider impact than previously thought.

  18. Effects of nucleotide binding to LmrA: A combined MAS-NMR and solution NMR study.

    PubMed

    Hellmich, Ute A; Mönkemeyer, Leonie; Velamakanni, Saroj; van Veen, Hendrik W; Glaubitz, Clemens

    2015-12-01

    ABC transporters are fascinating examples of fine-tuned molecular machines that use the energy from ATP hydrolysis to translocate a multitude of substrates across biological membranes. While structural details have emerged on many members of this large protein superfamily, a number of functional details are still under debate. High resolution structures yield valuable insights into protein function, but it is the combination of structural, functional and dynamic insights that facilitates a complete understanding of the workings of their complex molecular mechanisms. NMR is a technique well-suited to investigate proteins in atomic resolution while taking their dynamic properties into account. It thus nicely complements other structural techniques, such as X-ray crystallography, that have contributed high-resolution data to the architectural understanding of ABC transporters. Here, we describe the heterologous expression of LmrA, an ABC exporter from Lactococcus lactis, in Escherichia coli. This allows for more flexible isotope labeling for nuclear magnetic resonance (NMR) studies and the easy study of LmrA's multidrug resistance phenotype. We use a combination of solid-state magic angle spinning (MAS) on the reconstituted transporter and solution NMR on its isolated nucleotide binding domain to investigate consequences of nucleotide binding to LmrA. We find that nucleotide binding affects the protein globally, but that NMR is also able to pinpoint local dynamic effects to specific residues, such as the Walker A motif's conserved lysine residue.

  19. Assessing Heterogeneity of Osteolytic Lesions in Multiple Myeloma by 1H HR-MAS NMR Metabolomics

    PubMed Central

    Tavel, Laurette; Fontana, Francesca; Garcia Manteiga, Josè Manuel; Mari, Silvia; Mariani, Elisabetta; Caneva, Enrico; Sitia, Roberto; Camnasio, Francesco; Marcatti, Magda; Cenci, Simone; Musco, Giovanna

    2016-01-01

    Multiple myeloma (MM) is a malignancy of plasma cells characterized by multifocal osteolytic bone lesions. Macroscopic and genetic heterogeneity has been documented within MM lesions. Understanding the bases of such heterogeneity may unveil relevant features of MM pathobiology. To this aim, we deployed unbiased 1H high-resolution magic-angle spinning (HR-MAS) nuclear magnetic resonance (NMR) metabolomics to analyze multiple biopsy specimens of osteolytic lesions from one case of pathological fracture caused by MM. Multivariate analyses on normalized metabolite peak integrals allowed clusterization of samples in accordance with a posteriori histological findings. We investigated the relationship between morphological and NMR features by merging morphological data and metabolite profiling into a single correlation matrix. Data-merging addressed tissue heterogeneity, and greatly facilitated the mapping of lesions and nearby healthy tissues. Our proof-of-principle study reveals integrated metabolomics and histomorphology as a promising approach for the targeted study of osteolytic lesions. PMID:27809247

  20. Immobilization of soluble protein complexes in MAS solid-state NMR: Sedimentation versus viscosity.

    PubMed

    Sarkar, Riddhiman; Mainz, Andi; Busi, Baptiste; Barbet-Massin, Emeline; Kranz, Maximilian; Hofmann, Thomas; Reif, Bernd

    2016-01-01

    In recent years, MAS solid-state NMR has emerged as a technique for the investigation of soluble protein complexes. It was found that high molecular weight complexes do not need to be crystallized in order to obtain an immobilized sample for solid-state NMR investigations. Sedimentation induced by sample rotation impairs rotational diffusion of proteins and enables efficient dipolar coupling based cross polarization transfers. In addition, viscosity contributes to the immobilization of the molecules in the sample. Natural Deep Eutectic Solvents (NADES) have very high viscosities, and can replace water in living organisms. We observe a considerable amount of cross polarization transfers for NADES solvents, even though their molecular weight is too low to yield significant sedimentation. We discuss how viscosity and sedimentation both affect the quality of the obtained experimental spectra. The FROSTY/sedNMR approach holds the potential to study large protein complexes, which are otherwise not amenable for a structural characterization using NMR. We show that using this method, backbone assignments of the symmetric proteasome activator complex (1.1MDa), and high quality correlation spectra of non-symmetric protein complexes such as the prokaryotic ribosome 50S large subunit binding to trigger factor (1.4MDa) are obtained.

  1. Conformational analysis of capsaicin using 13C, 15N MAS NMR, GIAO DFT and GA calculations

    NASA Astrophysics Data System (ADS)

    Siudem, Paweł; Paradowska, Katarzyna; Bukowicki, Jarosław

    2017-10-01

    Capsaicin produced by plants from genus Capsicum exerts multiple pharmacological effects and has found applications in food and pharmaceutical industry. The alkaloid was studied by a combined approach: solid-state NMR, GA conformational search and GIAO DFT methods. The 13C CPMAS NMR spectra were recorded using variable contact time and dipolar dephasing experiments. The results of cross-polarization (CP) kinetics, such as TCP values and long T1ρH (100-200 ms), indicated that the capsaicin molecule is fairly mobile, especially at the end of the aliphatic chain. The15N MAS NMR spectrum showed one narrow signal at -255 ppm. Genetic algorithm (GA) search with multi modal optimization was used to find low-energy conformations of capsaicin. Theoretical GIAO DFT calculations were performed using different basis sets to characterize five selected conformations. 13C CPMAS NMR was used as a validation method and the experimental chemical shifts were compared with those calculated for selected stable conformers. Conformational analysis suggests that the side chain can be bent or extended. A comparison of the experimental and the calculated chemical shifts indicates that solid capsaicin does not have the same structure as those established by PWXRD.

  2. Structural analysis of molybdo-zinc-phosphate glasses: Neutron scattering, FTIR, Raman scattering, MAS NMR studies

    NASA Astrophysics Data System (ADS)

    Renuka, C.; Shinde, A. B.; Krishna, P. S. R.; Reddy, C. Narayana

    2016-08-01

    Vitreous samples were prepared in the xMoO3-17ZnO-(83-x) NaPO3 with 35 ≥ x ≥ 55 glass forming system by energy efficient microwave heating method. Structural evolution of the vitreous network was monitored as a function of composition by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), Raman scattering, Magic Angle Spin Nuclear magnetic resonance (MAS NMR) and Neutron scattering. Addition of MoO3 to the ZnO-NaPO3 glass leads to a pronounced increase in glass transition temperature (Tg) suggesting a significant increase in network connectivity and strength. In order to analyze FTIR and Raman scattering, a simple structural model is presented to rationalize the experimental observations. A number of structural units are formed due to network modification, and the resulting glass may be characterized by a network polyhedral with different numbers of unshared corners. 31P MAS NMR confirms a clear distinction between structural species having 3, 2, 1, 0 bridging oxygens (BOs). Further, Neutron scattering studies were used to probe the structure of these glasses. The result suggests that all the investigated glasses have structures based on chains of four coordinated phosphate and six coordinated molybdate units, besides, two different lengths of P-O bonds in tetrahedral phosphate units that are assigned to bonds of the P-atom with terminal and bridging oxygen atoms.

  3. Indirect detection of infinite-speed MAS solid-state NMR spectra

    NASA Astrophysics Data System (ADS)

    Perras, Frédéric A.; Venkatesh, Amrit; Hanrahan, Michael P.; Goh, Tian Wei; Huang, Wenyu; Rossini, Aaron J.; Pruski, Marek

    2017-03-01

    Heavy spin-1/2 nuclides are known to possess very large chemical shift anisotropies that can challenge even the most advanced magic-angle-spinning (MAS) techniques. Wide manifolds of overlapping spinning sidebands and insufficient excitation bandwidths often obfuscate meaningful spectral information and force the use of static, low-resolution solid-state (SS)NMR methods for the characterization of materials. To address these issues, we have merged fast-magic-angle-turning (MAT) and dipolar heteronuclear multiple-quantum coherence (D-HMQC) experiments to obtain D-HMQC-MAT pulse sequences which enable the rapid acquisition of 2D SSNMR spectra that correlate isotropic 1H chemical shifts to the indirectly detected isotropic ;infinite-MAS; spectra of heavy spin-1/2 nuclides. For these nuclides, the combination of fast MAS and 1H detection provides a high sensitivity, which rivals the DNP-enhanced ultra-wideline SSNMR. The new pulse sequences were used to determine the Pt coordination environments in a complex mixture of decomposition products of transplatin and in a metal-organic framework with Pt ions coordinated to the linker ligands.

  4. SLOW-MAS NMR METHODS TO STUDY METABOLIC PROCESSES IN VIVO AND IN VITRO

    SciTech Connect

    Wind, Robert A.; Bertram, Hanne Christine; Hu, Jian Zhi

    2005-09-25

    In vitro and in vivo 1H NMR spectroscopy is widely used to measure metabolic profiles in cells, tissues, animals, and humans and to use them, e.g., for diagnosis and therapy response evaluations. However, the spectra often suffer from poor resolution due to variations in the isotropic bulk magnetic susceptibility present in biological objects, resulting in a broadening of the NMR lines. In principle this broadening can be averaged to zero by the technique of magic angle spinning (MAS), where the sample is rotated about an axis making an angle of 54o44’ relative to the external magnetic field. However, a problem is that in a standard MAS experiment spinning speeds of a kHz or more are required in order to avoid the occurrence of spinning sidebands (SSBs) in the spectra, which renders analysis of the spectra difficult again. At these spinning speeds the large centrifugal forces cause severe structural damage in larger biological objects, so that this method cannot be used to study metabolic processes in intact samples. In solid state NMR several methods have been developed where slow MAS is combined with special radio frequency pulse sequences to eliminate spinning side bands or separate them from the isotropic spectrum so that a SSB-free high-resolution isotropic spectrum is obtained. It has been shown recently that two methods, phase-adjusted spinning sidebands (PASS) and phase-corrected magic angle turning (PHORMAT), can successfully be modified for applications in biological materials (1, 2). With PASS MAS speeds as low as 40 Hz can be employed, allowing non or minimally invasive in vitro studies of excised tissues and organs. This method was used, amongst other things, to study post mortem changes in the proton metabolite spectra in excised rabbit muscle tissue (3). With PHORMAT the NMR sensitivity is reduced and longer measuring times are required, but with this methodology the MAS speed can be reduced to ~1 Hz. This makes PHORMAT amenable for in vivo

  5. Lipid Bilayer-Bound Conformation of an Integral Membrane Beta Barrel Protein by Multidimensional MAS NMR

    PubMed Central

    Eddy, Matthew T.; Su, Yongchao; Silvers, Robert; Andreas, Loren; Clark, Lindsay; Wagner, Gerhard; Pintacuda, Guido; Emsley, Lyndon; Griffin, Robert G.

    2015-01-01

    The human voltage dependent anion channel 1 (VDAC) is a 32 kDa β-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and diffraction structures, a structural basis for the mechanism of its function is not yet fully understood. Biophysical studies suggest VDAC requires a lipid bilayer to achieve full function, motivating the need for atomic resolution structural information of VDAC in a membrane environment. Here we report an essential step toward that goal: extensive assignments of backbone and side chain resonances for VDAC in DMPC lipid bilayers via magic angle spinning nuclear magnetic resonance (MAS NMR). VDAC reconstituted into DMPC lipid bilayers spontaneously forms 2-dimensional lipid crystals, showing remarkable spectral resolution (0.5–0.3 ppm for 13C line width and less than 0.5 ppm 15N line widths at 750 MHz). In addition to the benefits of working in a lipid bilayer, several distinct advantages are observed with the lipid crystalline preparation. First, the strong signals and sharp line widths facilitated extensive NMR resonance assignments for an integral membrane β-barrel protein in lipid bilayers by MAS NMR. Second, a large number of residues in loop regions were readily observed and assigned, which can be challenging in detergent-solubilized membrane proteins where loop regions are often not detected due to line broadening from conformational exchange. Third, complete backbone and side chain chemical shift assignments could be obtained for the first 25 residues, which comprise the functionally important N-terminus. The reported assignments allow us to compare predicted torsion angles for VDAC prepared in DMPC 2D lipid crystals, DMPC liposomes, and LDAO-solubilized samples to address the possible effects of the membrane mimetic environment on the conformation of the protein. Concluding, we discuss the strengths and weaknesses of the reported

  6. Lipid bilayer-bound conformation of an integral membrane beta barrel protein by multidimensional MAS NMR.

    PubMed

    Eddy, Matthew T; Su, Yongchao; Silvers, Robert; Andreas, Loren; Clark, Lindsay; Wagner, Gerhard; Pintacuda, Guido; Emsley, Lyndon; Griffin, Robert G

    2015-04-01

    The human voltage dependent anion channel 1 (VDAC) is a 32 kDa β-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and diffraction structures, a structural basis for the mechanism of its function is not yet fully understood. Biophysical studies suggest VDAC requires a lipid bilayer to achieve full function, motivating the need for atomic resolution structural information of VDAC in a membrane environment. Here we report an essential step toward that goal: extensive assignments of backbone and side chain resonances for VDAC in DMPC lipid bilayers via magic angle spinning nuclear magnetic resonance (MAS NMR). VDAC reconstituted into DMPC lipid bilayers spontaneously forms two-dimensional lipid crystals, showing remarkable spectral resolution (0.5-0.3 ppm for (13)C line widths and <0.5 ppm (15)N line widths at 750 MHz). In addition to the benefits of working in a lipid bilayer, several distinct advantages are observed with the lipid crystalline preparation. First, the strong signals and sharp line widths facilitated extensive NMR resonance assignments for an integral membrane β-barrel protein in lipid bilayers by MAS NMR. Second, a large number of residues in loop regions were readily observed and assigned, which can be challenging in detergent-solubilized membrane proteins where loop regions are often not detected due to line broadening from conformational exchange. Third, complete backbone and side chain chemical shift assignments could be obtained for the first 25 residues, which comprise the functionally important N-terminus. The reported assignments allow us to compare predicted torsion angles for VDAC prepared in DMPC 2D lipid crystals, DMPC liposomes, and LDAO-solubilized samples to address the possible effects of the membrane mimetic environment on the conformation of the protein. Concluding, we discuss the strengths and weaknesses of the reported

  7. Proton detection of MAS solid-state NMR spectra of half-integer quadrupolar nuclei.

    PubMed

    Venkatesh, Amrit; Hanrahan, Michael P; Rossini, Aaron J

    Fast magic angle spinning (MAS) and proton detection has found widespread application to enhance the sensitivity of solid-state NMR experiments with spin-1/2 nuclei such as (13)C, (15)N and (29)Si, however, this approach is not yet routinely applied to half-integer quadrupolar nuclei. Here we have investigated the feasibility of using fast MAS and proton detection to enhance the sensitivity of solid-state NMR experiments with half-integer quadrupolar nuclei. The previously described dipolar hetero-nuclear multiple quantum correlation (D-HMQC) and dipolar refocused insensitive nuclei enhanced by polarization transfer (D-RINEPT) pulse sequences were used for proton detection of half-integer quadrupolar nuclei. Quantitative comparisons of signal-to-noise ratios and the sensitivity of proton detected D-HMQC and D-RINEPT and direct detection spin echo and quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) solid-state NMR spectra, demonstrate that one dimensional proton detected experiments can provide sensitivity similar to or exceeding that obtainable with direct detection QCPMG experiments. 2D D-HMQC and D-RINEPT experiments provide less sensitivity than QCPMG experiments but proton detected 2D hetero-nuclear correlation solid-state NMR spectra of half-integer nuclei can still be acquired in about the same time as a 1D spin echo spectrum. Notably, the rarely used D-RINEPT pulse sequence is found to provide similar, or better sensitivity than D-HMQC in some cases. Proton detected D-RINEPT benefits from the short longitudinal relaxation times (T1) normally associated with half-integer quadrupolar nuclei, it can be combined with existing signal enhancement methods for quadrupolar nuclei, and t1-noise in the indirect dimension can easily be removed by pre-saturation of the (1)H nuclei. The rapid acquisition of proton detected 2D HETCOR solid-state NMR spectra of a range of half-integer quadrupolar nuclei such as (17)O, (27)Al, (35)Cl and (71)Ga is demonstrated. Copyright

  8. MAS (1)H NMR Probes Freezing Point Depression of Water and Liquid-Gel Phase Transitions in Liposomes.

    PubMed

    Mandal, Abhishek; van der Wel, Patrick C A

    2016-11-01

    The lipid bilayer typical of hydrated biological membranes is characterized by a liquid-crystalline, highly dynamic state. Upon cooling or dehydration, these membranes undergo a cooperative transition to a rigidified, more-ordered, gel phase. This characteristic phase transition is of significant biological and biophysical interest, for instance in studies of freezing-tolerant organisms. Magic-angle-spinning (MAS) solid-state NMR (ssNMR) spectroscopy allows for the detection and characterization of the phase transitions over a wide temperature range. In this study we employ MAS (1)H NMR to probe the phase transitions of both solvent molecules and different hydrated phospholipids, including tetraoleoyl cardiolipin (TOCL) and several phosphatidylcholine lipid species. The employed MAS NMR sample conditions cause a previously noted substantial reduction in the freezing point of the solvent phase. The effect on the solvent is caused by confinement of the aqueous solvent in the small and densely packed MAS NMR samples. In this study we report and examine how the freezing point depression also impacts the lipid phase transition, causing a ssNMR-observed reduction in the lipids' melting temperature (Tm). The molecular underpinnings of this phenomenon are discussed and compared with previous studies of membrane-associated water phases and the impact of membrane-protective cryoprotectants. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  9. Structural characteristics for phase transitions of [N(CH3)4]2CuCl4 by (13)C CP/MAS NMR and (14)N NMR.

    PubMed

    Hee Kim, Nam; Lim, Ae Ran

    2015-09-01

    Structure geometry changes in [N(CH3)4]2CuCl4 near the phase transition temperature were studied by (13)C CP/MAS NMR and (14)N NMR spectrum. We distinguished the two chemically inequivalent N(1)(CH3)4 and N(2)(CH3)4 groups by (13)C CP/MAS NMR and (14)N NMR spectrum. The abrupt changes in chemical shifts and the split of the NMR signals near the phase transition temperatures for (13)C and (14)N are explained by a structural phase transition, implying that the structural geometry depends on the temperature. The mechanism behind this phase transition is based on ferroelasticity, and is also mainly related to the (14)N ions in N(CH3)4 ions. Furthermore, both phases III and IV exhibit ferroelastic properties with identical orientational domains. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Molecular degradation of ancient documents revealed by 1H HR-MAS NMR spectroscopy

    PubMed Central

    Corsaro, Carmelo; Mallamace, Domenico; Łojewska, Joanna; Mallamace, Francesco; Pietronero, Luciano; Missori, Mauro

    2013-01-01

    For centuries mankind has stored its knowledge on paper, a remarkable biomaterial made of natural cellulose fibers. However, spontaneous cellulose degradation phenomena weaken and discolorate paper over time. The detailed knowledge of products arising from cellulose degradation is essential in understanding deterioration pathways and in improving durability of cultural heritage. In this study, for the first time, products of cellulose degradation were individually detected in solid paper samples by means of an extremely powerful proton HR-MAS NMR set-up, in combination to a wise use of both ancient and, as reference, artificially aged paper samples. Carboxylic acids, in addition to more complex dicarboxylic and hydroxy-carboxylic acids, were found in all samples studied. Since these products can catalyze further degradation, their knowledge is fundamental to improve conservation strategies of historical documents. Furthermore, the identification of compounds used in ancient production techniques, also suggests for artifacts dating, authentication and provenance. PMID:24104201

  11. 19F MAS-NMR studies of strontium oxyfluoride aluminosilicate glass

    NASA Astrophysics Data System (ADS)

    Środa, M.; Olejniczak, Z.

    2011-08-01

    Local environment of fluorine atoms in the lanthanum oxyfluoride aluminosilicate glasses and glass-ceramics modified by SrO was studied by solid state 19F MAS-NMR spectroscopy and X-ray diffraction. The effect of strontium concentration on the formation of crystalline LaF 3 phase was determined, as a function of heat treatment conditions. In all glasses studied, the F-Me( n) (where Me = Sr, La), but no Na-F species were observed. The presence of F-La,Sr( n) units, in which fluorine is coordinated by both lanthanum and strontium, was detected in the glass with higher content of SrO. Supplementary XRD analysis of this series confirmed that an increase of strontium contents leads to the formation of Sr 0.69La 0.31F 2.31 and LaSr 2F 7, instead of the pure LaF 3 only.

  12. Molecular degradation of ancient documents revealed by 1H HR-MAS NMR spectroscopy.

    PubMed

    Corsaro, Carmelo; Mallamace, Domenico; Łojewska, Joanna; Mallamace, Francesco; Pietronero, Luciano; Missori, Mauro

    2013-10-09

    For centuries mankind has stored its knowledge on paper, a remarkable biomaterial made of natural cellulose fibers. However, spontaneous cellulose degradation phenomena weaken and discolorate paper over time. The detailed knowledge of products arising from cellulose degradation is essential in understanding deterioration pathways and in improving durability of cultural heritage. In this study, for the first time, products of cellulose degradation were individually detected in solid paper samples by means of an extremely powerful proton HR-MAS NMR set-up, in combination to a wise use of both ancient and, as reference, artificially aged paper samples. Carboxylic acids, in addition to more complex dicarboxylic and hydroxy-carboxylic acids, were found in all samples studied. Since these products can catalyze further degradation, their knowledge is fundamental to improve conservation strategies of historical documents. Furthermore, the identification of compounds used in ancient production techniques, also suggests for artifacts dating, authentication and provenance.

  13. Structural study of synthetic mica montmorillonite by means of 2D MAS NMR experiments

    NASA Astrophysics Data System (ADS)

    Alba, M. D.; Castro, M. A.; Chain, P.; Naranjo, M.; Perdigón, A. C.

    2005-07-01

    Syn-1, is a synthetic mica montmorillonite interstratified mineral that forms one of the standard clay samples in the Clay Minerals Society Source Clays Project. However, there are still controversies regarding some structural aspects such as the interlayer composition or the location of the extra-aluminium determined by chemical analysis. The main objective of this paper is to shed light on those structural aspects that affect the reactivity of the interstratified minerals. For this purpose, we have used 1 H 29 Si and 1 H 27Al HETCOR MAS NMR to show that it is likely that the interlayer space of the beidellite part is composed of ammonium ions whereas ammonium and aluminium ions are responsible for the charge balance in the mica type layer.

  14. Metallic Li colloids studied by Li-7 MAS NMR in electron-irradiated LiF

    NASA Astrophysics Data System (ADS)

    Zogal, O. J.; Beuneu, F.; Vajda, P.; Florian, P.; Massiot, D.

    Li-7 MAS NMR spectra of 2.5 MeV electron-irradiated LiF crystals have been measured in a field of 9.4 T. Besides the resonance line of the ionic compound, a second well-separated spectrum is observed in the region of the Knight shift value for metallic lithium. At room temperature, the latter can be decomposed into two components with different Knight shift and linewidth values. When the temperature is increased, line narrowing takes place at first, indicating shortening of correlation times for self-diffusion, independently in both components. Above 370 K, both lines broaden and approach each other before collapsing into a single line. The high ppm component disappears after crossing the melting temperature of metallic lithium (454 K). The two lines are attributed to different types of metallic Li: one to bulk-like metal, the other to Li present initially under pressure and relaxing to the former under thermal treatment.

  15. Thermal maturity of type II kerogen from the New Albany Shale assessed by 13C CP/MAS NMR.

    PubMed

    Werner-Zwanziger, Ulrike; Lis, Grzegorz; Mastalerz, Maria; Schimmelmann, Arndt

    2005-01-01

    Thermal maturity of oil and gas source rocks is typically quantified in terms of vitrinite reflectance, which is based on optical properties of terrestrial woody remains. This study evaluates 13C CP/MAS NMR parameters in kerogen (i.e., the insoluble fraction of organic matter in sediments and sedimentary rocks) as proxies for thermal maturity in marine-derived source rocks where terrestrially derived vitrinite is often absent or sparse. In a suite of samples from the New Albany Shale (Middle Devonian to the Early Mississippian, Illinois Basin) the abundance of aromatic carbon in kerogen determined by 13C CP/MAS NMR correlates linearly well with vitrinite reflectance.

  16. Technetium-99 MAS NMR spectroscopy of a cationic framework material that traps TcO4- ions

    SciTech Connect

    Yu, P.; Wang, Shuao; Alekseev, Evgeny V.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.; Phillips, Brian L.; Casey, William H.

    2010-07-15

    99Tc magic-angle spinning (MAS) NMR spectra show that TcO4- ions, which are generated by nuclear fission and can contaminate the environment, can be trapped within the channels and cavities of a cationic framework material (see picture). These spectra are among the first 99Tc MAS NMR spectra reported to date, and show that the TcO4- ions can be efficiently removed from simulated nuclear waste solutions.

  17. Assessing the fate and transformation of plant residues in the terrestrial environment using HR-MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kelleher, Brian P.; Simpson, Myrna J.; Simpson, Andre J.

    2006-08-01

    Plant litter decomposition plays a fundamental role in carbon and nitrogen cycles, provides key nutrients to the soil environment and represents a potentially large positive feedback to atmospheric CO 2. However, the full details of decomposition pathways and products are unknown. Here we present the first application of HR-MAS NMR spectroscopy on 13C and 15N labeled plant materials, and apply this approach in a preliminary study to monitor the environmental degradation of the pine and wheatgrass residues over time. In HR-MAS, is it possible to acquire very high resolution NMR data of plant biomass, and apply the vast array of multidimensional experiments available in conventional solution-state NMR. High levels of isotopic enrichment combined with HR-MAS significantly enhance the detection limits, and provide a wealth of information that is unattainable by any other method. Diffusion edited HR-MAS NMR data reveal the rapid loss of carbohydrate structures, while two-dimensional (2-D) HR-MAS NMR spectra demonstrate the relatively fast loss of both hydrolysable and condensed tannin structures from all plant tissues studied. Aromatic (partially lignin) and aliphatic components (waxes, cuticles) tend to persist, along with a small fraction of carbohydrate, and become highly functionalized over time. While one-dimensional (1-D) 13C HR-MAS NMR spectra of fresh plant tissue reflect compositional differences between pine and grass, these differences become negligible after decomposition suggesting that recalcitrant carbon may be similar despite the plant source. Two-dimensional 1H- 15N HR-MAS NMR analysis of the pine residue suggests that nitrogen from specific peptides is either selectively preserved or used for the synthesis of what appears to be novel structures. The amount of relevant data generated from plant components in situ using HR-MAS NMR is highly encouraging, and demonstrates that complete assignment will yield unprecedented structural knowledge of plant cell

  18. Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy

    PubMed Central

    Debelouchina, Galia T.; Bayro, Marvin J.; Fitzpatrick, Anthony W.; Ladizhansky, Vladimir; Colvin, Michael T.; Caporini, Marc A.; Jaroniec, Christopher P.; Bajaj, Vikram S.; Rosay, Melanie; MacPhee, Cait E.; Vendruscolo, Michele; Maas, Werner E.; Dobson, Christopher M.; Griffin, Robert G.

    2014-01-01

    Protein magic angle spinning (MAS) NMR spectroscopy has generated structural models of several amyloid fibril systems, thus providing valuable information regarding the forces and interactions that confer the extraordinary stability of the amyloid architecture. Despite these advances, however, obtaining atomic resolution information describing the higher levels of structural organization within the fibrils remains a significant challenge. Here, we detail MAS NMR experiments and sample labeling schemes designed specifically to probe such higher order amyloid structure and we have applied them to the fibrils formed by an eleven-residue segment of the amyloidogenic protein transthyretin (TTR(105-115)). These experiments have allowed us to define unambiguously not only the arrangement of the peptide β-strands into β-sheets but also the β-sheet interfaces within each protofilament, and in addition to identify the nature of the protofilament-to-protofilament contacts that lead to the formation of the complete fibril. Our efforts have resulted in 111 quantitative distance and torsion angle restraints (10 per residue) that describe the various levels of structure organization. The experiments benefited extensively from the use of dynamic nuclear polarization (DNP), which in some cases allowed us to shorten the data acquisition time from days to hours and to improve significantly the signal-to-noise ratios of the spectra. The β-sheet interface and protofilament interactions identified here revealed local variations in the structure that result in multiple peaks for the exposed N- and C-termini of the peptide and in inhomogeneous line-broadening for the side-chains buried within the interior of the fibrils. PMID:24304221

  19. Dynamic Nuclear Polarization Enhanced MAS NMR Spectroscopy for Structural Analysis of HIV-1 Protein Assemblies.

    PubMed

    Gupta, Rupal; Lu, Manman; Hou, Guangjin; Caporini, Marc A; Rosay, Melanie; Maas, Werner; Struppe, Jochem; Suiter, Christopher; Ahn, Jinwoo; Byeon, In-Ja L; Franks, W Trent; Orwick-Rydmark, Marcella; Bertarello, Andrea; Oschkinat, Hartmut; Lesage, Anne; Pintacuda, Guido; Gronenborn, Angela M; Polenova, Tatyana

    2016-01-21

    Mature infectious HIV-1 virions contain conical capsids composed of CA protein, generated by the proteolytic cleavage cascade of the Gag polyprotein, termed maturation. The mechanism of capsid core formation through the maturation process remains poorly understood. We present DNP-enhanced MAS NMR studies of tubular assemblies of CA and Gag CA-SP1 maturation intermediate and report 20-64-fold sensitivity enhancements due to DNP at 14.1 T. These sensitivity enhancements enabled direct observation of spacer peptide 1 (SP1) resonances in CA-SP1 by dipolar-based correlation experiments, unequivocally indicating that the SP1 peptide is unstructured in assembled CA-SP1 at cryogenic temperatures, corroborating our earlier results. Furthermore, the dependence of DNP enhancements and spectral resolution on magnetic field strength (9.4-18.8 T) and temperature (109-180 K) was investigated. Our results suggest that DNP-based measurements could potentially provide residue-specific dynamics information by allowing for the extraction of the temperature dependence of the anisotropic tensorial or relaxation parameters. With DNP, we were able to detect multiple well-resolved isoleucine side-chain conformers; unique intermolecular correlations across two CA molecules; and functionally relevant conformationally disordered states such as the 14-residue SP1 peptide, none of which are visible at ambient temperatures. The detection of isolated conformers and intermolecular correlations can provide crucial constraints for structure determination of these assemblies. Overall, our results establish DNP-based MAS NMR spectroscopy as an excellent tool for the characterization of HIV-1 assemblies.

  20. Dynamic Nuclear Polarization Enhanced MAS NMR for Structural Analysis of HIV-1 Protein Assemblies

    PubMed Central

    Gupta, Rupal; Lu, Manman; Hou, Guangjin; Caporini, Marc A.; Rosay, Melanie; Maas, Werner; Struppe, Jochem; Suiter, Christopher; Ahn, Jinwoo; Byeon, In-Ja L.; Franks, W. Trent; Orwick-Rydmark, Marcella; Bertarello, Andrea; Oschkinat, Hartmut; Lesage, Anne; Pintacuda, Guido; Gronenborn, Angela M.; Polenova, Tatyana

    2016-01-01

    Mature infectious HIV-1 virions contain conical capsids comprised of CA protein, generated by the proteolytic cleavage cascade of the Gag polyprotein, termed maturation. The mechanism of capsid core formation through the maturation process remains poorly understood. We present DNP-enhanced MAS NMR studies of tubular assemblies of CA and Gag CA-SP1 maturation intermediate and report 20 – 64 fold sensitivity enhancements due to DNP at 14.1 T. These sensitivity enhancements enabled direct observation of spacer peptide 1 (SP1) resonances in CA-SP1 by dipolar based correlation experiments, unequivocally indicating that the SP1 peptide is unstructured in assembled CA-SP1 at cryogenic temperatures, corroborating our earlier results. Furthermore, the dependence of DNP enhancements and spectral resolution on magnetic field strength (9.4 – 18.8 T) and temperature (109 – 180 K) was investigated. Our results suggest that DNP-based measurements could potentially provide residue-specific dynamics information by allowing for the extraction of temperature dependence of the anisotropic tensorial or relaxation parameters. With DNP, we were able to detect multiple well-resolved isoleucine sidechain conformers, unique intermolecular correlations across two CA molecules, and functionally relevant conformationally disordered states such as the 14-residue SP1 peptide, none of which are visible at ambient temperatures. The detection of isolated conformers and intermolecular correlations can provide crucial constraints for structure determination of these assemblies. Overall, our results establish DNP-based MAS NMR as an excellent tool for characterization of HIV-1 assemblies. PMID:26709853

  1. 1H HR-MAS NMR of carotenoids in aqueous samples and raw vegetables.

    PubMed

    Miglietta, M L; Lamanna, R

    2006-07-01

    Carotenoids are linear C40 tetraterpenoid hydrocarbons and represent a wide category of natural pigments. They are components of the pigment system of chloroplasts and are involved in the primary light absorption and the photon canalization of photosynthesis. Moreover, they also behave as quenchers of singlet oxygen, protecting cells and organisms against lipid peroxidation. Carotenoids have a strong lipophilic character and are usually analyzed in organic solvents. However, because of their biological activity, the characterization of these compounds in an aqueous environment or in the natural matrix is very important. One of the most important dietary carotenoids is beta-carotene, which has been extensively studied both in vivo and in model systems, but because of the low concentration and strong interaction with the biological matrix, beta-carotene has never been observed by NMR in solid aqueous samples.In the present work, a model system has been developed for the detection and identification of beta-carotene in solid aqueous samples by 1H HR-MAS NMR. The efficiency of the model has led to the identification of beta-carotene in a raw vegetable matrix.

  2. Evidence for cross-linking in tomato cutin using HR-MAS NMR spectroscopy.

    PubMed

    Deshmukh, Ashish P; Simpson, André J; Hatcher, Patrick G

    2003-11-01

    Cutin is a polyester biopolymer component of plant leaf and fruit cuticles, most often associated with waxes and cuticular polysaccharides, and sometimes with another aliphatic biopolymer called cutan. Insolubility of these cuticular biopolymers has made it difficult to apply traditional analytical techniques for structure determination, because most techniques providing molecular level details require solubility. By using the relatively new technique of one and two-dimensional high-resolution magic angle spinning (HR-MAS) NMR spectroscopy, with added information from solid-state 13C NMR spectroscopy, detailed through-bond connectivities and assignments are made for cutin from Lycopersicon esculentum (tomato) fruit. Based on the data obtained, tomato cutin is found to be predominantly an aliphatic polyester with some olefinic and aromatic moieties, consistent with previous studies that employed various degradative approaches. Aside from esters, there are free primary and secondary alcohol groups, as well as free fatty acids. A significant finding is the presence of alpha-branched fatty acids/esters. Mid-chain hydroxyls appear to be generally unesterified, but esters of mid-chain hydroxyls have been identified. The alpha-branched fatty acids/esters and esters of mid-chain hydroxyls could point towards cross-linking.

  3. Insight into hydrogen bonding of uranyl hydroxide layers and capsules by use of 1H magic-angle spinning NMR spectroscopy [Insight into the hydrogen bonding for uranyl hydroxides using 1H MAS NMR spectroscopy

    SciTech Connect

    Alam, Todd M.; Liao, Zuolei; Nyman, May; Yates, Jonathan

    2016-04-27

    Solid-state 1H magic-angle spinning (MAS) NMR was used to investigate local proton environments in anhydrous [UO2(OH)2] (α-UOH) and hydrated uranyl hydroxide [(UO2)4O(OH)6·5H2O (metaschoepite). For the metaschoepite material, proton resonances of the μ2-OH hydroxyl and interlayer waters were resolved, with two-dimensional (2D) double-quantum (DQ) 1H–1H NMR correlation experiments revealing strong dipolar interactions between these different proton species. The experimental NMR results were combined with first-principles CASTEP GIPAW (gauge including projector-augmented wave) chemical shift calculations to develop correlations between hydrogen-bond strength and observed 1H NMR chemical shifts. Furthermore, these NMR correlations allowed characterization of local hydrogen-bond environments in uranyl U24 capsules and of changes in hydrogen bonding that occurred during thermal dehydration of metaschoepite.

  4. Insight into hydrogen bonding of uranyl hydroxide layers and capsules by use of 1H magic-angle spinning NMR spectroscopy [Insight into the hydrogen bonding for uranyl hydroxides using 1H MAS NMR spectroscopy

    SciTech Connect

    Alam, Todd M.; Liao, Zuolei; Nyman, May; Yates, Jonathan

    2016-04-27

    Solid-state 1H magic-angle spinning (MAS) NMR was used to investigate local proton environments in anhydrous [UO2(OH)2] (α-UOH) and hydrated uranyl hydroxide [(UO2)4O(OH)6·5H2O (metaschoepite). For the metaschoepite material, proton resonances of the μ2-OH hydroxyl and interlayer waters were resolved, with two-dimensional (2D) double-quantum (DQ) 1H–1H NMR correlation experiments revealing strong dipolar interactions between these different proton species. The experimental NMR results were combined with first-principles CASTEP GIPAW (gauge including projector-augmented wave) chemical shift calculations to develop correlations between hydrogen-bond strength and observed 1H NMR chemical shifts. Furthermore, these NMR correlations allowed characterization of local hydrogen-bond environments in uranyl U24 capsules and of changes in hydrogen bonding that occurred during thermal dehydration of metaschoepite.

  5. Heating and temperature gradients of lipid bilayer samples induced by RF irradiation in MAS solid-state NMR experiments.

    PubMed

    Wang, Jing; Zhang, Zhengfeng; Zhao, Weijing; Wang, Liying; Yang, Jun

    2016-05-09

    The MAS solid-state NMR has been a powerful technique for studying membrane proteins within the native-like lipid bilayer environment. In general, RF irradiation in MAS NMR experiments can heat and potentially destroy expensive membrane protein samples. However, under practical MAS NMR experimental conditions, detailed characterization of RF heating effect of lipid bilayer samples is still lacking. Herein, using (1) H chemical shift of water for temperature calibration, we systematically study the dependence of RF heating on hydration levels and salt concentrations of three lipids in MAS NMR experiments. Under practical (1) H decoupling conditions used in biological MAS NMR experiments, three lipids show different dependence of RF heating on hydration levels as well as salt concentrations, which are closely associated with the properties of lipids. The maximum temperature elevation of about 10 °C is similar for the three lipids containing 200% hydration, which is much lower than that in static solid-state NMR experiments. The RF heating due to salt is observed to be less than that due to hydration, with a maximum temperature elevation of less than 4 °C in the hydrated samples containing 120 mmol l(-1) of salt. Upon RF irradiation, the temperature gradient across the sample is observed to be greatly increased up to 20 °C, as demonstrated by the remarkable broadening of (1) H signal of water. Based on detailed characterization of RF heating effect, we demonstrate that RF heating and temperature gradient can be significantly reduced by decreasing the hydration levels of lipid bilayer samples from 200% to 30%. Copyright © 2016 John Wiley & Sons, Ltd.

  6. Characterization of cation environments in polycrystalline forsterite by Mg-25 MAS, MQMAS, and QCPMG NMR

    SciTech Connect

    Davis, Michael C.; Brouwer, William J.; Lipton, Andrew S.; Gan, Zhehong; Mueller, Karl T.

    2010-11-01

    Forsterite (Mg2SiO4) is a silicate mineral frequently studied in the Earth sciences as it has a simple crystal structure and fast dissolution kinetics (elemental release rates under typical conditions on the order of 10-7 mol/m2/s1). During the dissolution process, spectroscopic techniques are often utilized to augment solution chemical analysis and to provide data for determining reaction mechanisms. Nuclear magnetic resonance (NMR) is able to interrogate the local bonding arrangement and coordination of a particular nuclide to obtain in structural information. Although previous NMR studies have focused on the silicon and oxygen environments in forsterite, studies focusing on the two nonequivalent magnesium environments in forsterite are limited to a few single-crystal studies. In this study, we present the results of 25Mg MAS, MQMAS, and static QCMG experiments performed on a powdered sample of pure synthetic forsterite. We also present spectral fits obtained from simulation software packages, which directly provide quadrupolar parameters for 25Mg nuclei occupying each of the two nonequivalent magnesium sites in the forsterite structure. These results are compared to calculations of the electric field gradient tenor conducted in previous ab initio studies to make definitive assignments correlating each peak to their respective magnesium site in the forsterite structure. Although previous NMR investigations of forsterite have focused on single-crystal samples, we have focused on powdered forsterite as the increased surface area of powdered samples makes them more amenable to laboratory-scale dissolution studies and, ultimately, the products from chemical weathering may be monitored an quantified.

  7. 3D Double-Quantum/Double-Quantum Exchange Spectroscopy of Protons under 100 kHz Magic Angle Spinning.

    PubMed

    Zhang, Rongchun; Duong, Nghia Tuan; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2017-06-22

    Solid-state (1)H NMR spectroscopy has attracted much attention in the recent years due to the remarkable spectral resolution improvement by ultrafast magic-angle-spinning (MAS) as well as due to the sensitivity enhancement rendered by proton detection. Although these developments have enabled the investigation of a variety of challenging chemical and biological solids, the proton spectral resolution is still poor for many rigid solid systems owing to the presence of conformational heterogeneity and the unsuppressed residual proton-proton dipolar couplings even with the use of the highest currently feasible sample spinning speed of ∼130 kHz. Although a further increase in the spinning speed of the sample could be beneficial to some extent, there is a need for alternate approaches to enhance the spectral resolution. Herein, by fully utilizing the benefits of double-quantum (DQ) coherences, we propose a single radio frequency channel proton-based 3D pulse sequence that correlates double-quantum (DQ), DQ, and single-quantum (SQ) chemical shifts of protons. In addition to the two-spin homonuclear proximity information, the proposed 3D DQ/DQ/SQ experiment also enables the extraction of three-spin and four-spin proximities, which could be beneficial for revealing the dipolar coupled proton network in the solid state. Besides, the 2D DQ/DQ spectrum sliced at different isotropic SQ chemical shift values of the 3D DQ/DQ/SQ spectrum will also facilitate the identification of DQ correlation peaks and improve the spectral resolution, as it only provides the local homonuclear correlation information associated with the specific protons selected by the SQ chemical shift frequency. The 3D pulse sequence and its efficiency are demonstrated experimentally on small molecular compounds in the solid state. We expect that this approach would create avenues for further developments by suitably combining the benefits of partial deuteration of samples, selective excitation

  8. Magnesium Silicate Dissolution Investigated by 29Si MAS, 1H-29Si CP MAS, 25Mg QCPMG, and 1H-25Mg CP QCPMG NMR

    SciTech Connect

    Davis, Michael C.; Brouwer, William J.; Wesolowski, David J.; Anovitz, Lawrence M.; Lipton, Andrew S.; Mueller, Karl T.

    2009-08-01

    Olivine has been the subject of frequent investigation in the earth sciences because of its simple structure and rapid dissolution kinetics. Several studies have observed a preferential release of magnesium with respect to silica during weathering under acidic conditions, which has been correlated to the formation of a silicon rich leached layer. While leached layer formation has been inferred through the changing solution chemistry, a thorough spectroscopic investigation of olivine reacted under acidic conditions has not been conducted. In particular, the fate of magnesium in the system is not understood and spectroscopic interrogations through nuclear magnetic resonance can elucidate the changing magnesium coordination and bonding environment. In this study, we combine analysis of the changing solution chemistry with advanced spectroscopic techniques (29Si MAS, 1H-29Si CP MAS, 25Mg QCPMG, and 1H-25Mg 2 CP QCPMG NMR) to probe leached layer formation and possible secondary phase precipitation during the dissolution of forsterite at 150 oC.

  9. Fermi resonance of C 1 chlorine compounds in the adsorbed phase of zeolites. An FTIR and MAS NMR spectroscopic study

    NASA Astrophysics Data System (ADS)

    Hannus, I.; Kónya, Z.; Nagy, J. B.; Kiricsi, I.

    1997-06-01

    Fermi resonance was investigated for CH 3Cl, COCl 2, CO + Cl 2, CCl 4 and CCl 2F 2 adsorbed in NaYFAU zeolite. The extent of the resonance was measured by IR spectroscopy, while the mechanism of surface reaction was evidenced by MAS NMR spectroscopy.

  10. Rapid measurement of multidimensional 1H solid-state NMR spectra at ultra-fast MAS frequencies

    NASA Astrophysics Data System (ADS)

    Ye, Yue Qi; Malon, Michal; Martineau, Charlotte; Taulelle, Francis; Nishiyama, Yusuke

    2014-02-01

    A novel method to realize rapid repetition of 1H NMR experiments at ultra-fast MAS frequencies is demonstrated. The ultra-fast MAS at 110 kHz slows the 1H-1H spin diffusion, leading to variations of 1H T1 relaxation times from atom to atom within a molecule. The different relaxation behavior is averaged by applying 1H-1H recoupling during relaxation delay even at ultra-fast MAS, reducing the optimal relaxation delay to maximize the signal to noise ratio. The way to determine optimal relaxation delay for arbitrary relaxation curve is shown. The reduction of optimal relaxation delay by radio-frequency driven recoupling (RFDR) was demonstrated on powder samples of glycine and ethenzamide with one and multi-dimensional NMR measurements.

  11. Heterogeneous Coordination Environments in Lithium-Neutralized Ionomers Identified Using 1H and 7Li MAS NMR

    PubMed Central

    Alam, Todd M.; Jenkins, Janelle E.; Bolintineanu, Dan S.; Stevens, Mark J.; Frischknecht, Amalie L.; Buitrago, C. Francisco; Winey, Karen I.; Opper, Kathleen L.; Wagener, Kenneth B.

    2012-01-01

    The carboxylic acid proton and the lithium coordination environments for precise and random Li-neutralized polyethylene acrylic acid P(E-AA) ionomers were explored using high speed solid-state 1H and 7Li MAS NMR. While the 7Li NMR revealed only a single Li coordination environment, the chemical shift temperature variation was dependent on the precise or random nature of the P(E-AA) ionomer. The 1H MAS NMR revealed two different carboxylic acid proton environments in these materials. By utilizing 1H-7Li rotational echo double resonance (REDOR) MAS NMR experiments, it was demonstrated that the proton environments correspond to different average 1H-7Li distances, with the majority of the protonated carboxylic acids having a close through space contact with the Li. Molecular dynamics simulations suggest that the shortest 1H-7Li distance corresponds to un-neutralized carboxylic acids directly involved in the coordination environment of Li clusters. These solid-state NMR results show that heterogeneous structural motifs need to be included when developing descriptions of these ionomer materials.

  12. Hydration properties of regioselectively etherified celluloses monitored by 2H and 13C solid-state MAS NMR spectroscopy.

    PubMed

    Larsen, Flemming H; Schöbitz, Michael; Schaller, Jens

    2012-06-20

    The hydration properties of 2,3-O-hydroxypropylcellulose (HPC) and 2,3-O-hydroxyethylcellulose (HEC) were analyzed by multi-nuclear solid-state MAS NMR spectroscopy. By 13C single-pulse (SP) MAS and cross-polarization (CP) MAS NMR, differences between the immobile regions and all parts of the polysaccharides were detected as a function of hydration. Complementary information about the water environments was observed by 2H MAS NMR. By this approach it was demonstrated that side chains in 2,3-O-HPC and 2,3-O-HEC were easier to hydrate than the cellulose backbone. Furthermore the motion of water was more restricted (slower) in 2,3-O-HPC than in 2,3-O-HEC. For both polysaccharides the hydration could be explained by a two-step process: in step one increased ordering of the immobile regions occurs after which the entire polymer is hydrated in step two. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. DNP-Enhanced MAS NMR of Bovine Serum Albumin Sediments and Solutions

    PubMed Central

    2015-01-01

    Protein sedimentation sans cryoprotection is a new approach to magic angle spinning (MAS) and dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy of proteins. It increases the sensitivity of the experiments by a factor of ∼4.5 in comparison to the conventional DNP sample preparation and circumvents intense background signals from the cryoprotectant. In this paper, we investigate sedimented samples and concentrated frozen solutions of natural abundance bovine serum albumin (BSA) in the absence of a glycerol-based cryoprotectant. We observe DNP signal enhancements of ε ∼ 66 at 140 GHz in a BSA pellet sedimented from an aqueous solution containing the biradical polarizing agent TOTAPOL and compare this with samples prepared using the conventional protocol (i.e., dissolution of BSA in a glycerol/water cryoprotecting mixture). The dependence of DNP parameters on the radical concentration points to the presence of an interaction between TOTAPOL and BSA, so much so that a frozen solution sans cryoprotectant still gives ε ∼ 50. We have studied the interaction of BSA with another biradical, SPIROPOL, that is more rigid than TOTAPOL and has been reported to give higher enhancements. SPIROPOL was also found to interact with BSA, and to give ε ∼ 26 close to its maximum achievable concentration. Under the same conditions, TOTAPOL gives ε ∼ 31, suggesting a lesser affinity of BSA for SPIROPOL with respect to TOTAPOL. Altogether, these results demonstrate that DNP is feasible in self-cryoprotecting samples. PMID:24460530

  14. DNP-enhanced MAS NMR of bovine serum albumin sediments and solutions.

    PubMed

    Ravera, Enrico; Corzilius, Björn; Michaelis, Vladimir K; Luchinat, Claudio; Griffin, Robert G; Bertini, Ivano

    2014-03-20

    Protein sedimentation sans cryoprotection is a new approach to magic angle spinning (MAS) and dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy of proteins. It increases the sensitivity of the experiments by a factor of ∼4.5 in comparison to the conventional DNP sample preparation and circumvents intense background signals from the cryoprotectant. In this paper, we investigate sedimented samples and concentrated frozen solutions of natural abundance bovine serum albumin (BSA) in the absence of a glycerol-based cryoprotectant. We observe DNP signal enhancements of ε ∼ 66 at 140 GHz in a BSA pellet sedimented from an aqueous solution containing the biradical polarizing agent TOTAPOL and compare this with samples prepared using the conventional protocol (i.e., dissolution of BSA in a glycerol/water cryoprotecting mixture). The dependence of DNP parameters on the radical concentration points to the presence of an interaction between TOTAPOL and BSA, so much so that a frozen solution sans cryoprotectant still gives ε ∼ 50. We have studied the interaction of BSA with another biradical, SPIROPOL, that is more rigid than TOTAPOL and has been reported to give higher enhancements. SPIROPOL was also found to interact with BSA, and to give ε ∼ 26 close to its maximum achievable concentration. Under the same conditions, TOTAPOL gives ε ∼ 31, suggesting a lesser affinity of BSA for SPIROPOL with respect to TOTAPOL. Altogether, these results demonstrate that DNP is feasible in self-cryoprotecting samples.

  15. Structural investigations of borosilicate glasses containing MoO 3 by MAS NMR and Raman spectroscopies

    NASA Astrophysics Data System (ADS)

    Caurant, D.; Majérus, O.; Fadel, E.; Quintas, A.; Gervais, C.; Charpentier, T.; Neuville, D.

    2010-01-01

    High molybdenum concentration in glass compositions may lead to alkali and alkaline-earth molybdates crystallization during melt cooling that must be controlled particularly during the preparation of highly radioactive nuclear glassy waste forms. To understand the effect of molybdenum addition on the structure of a simplified nuclear glass and to know how composition changes can affect molybdates crystallization tendency, the structure of two glass series belonging to the SiO 2-B 2O 3-Na 2O-CaO-MoO 3 system was studied by 29Si, 11B, 23Na MAS NMR and Raman spectroscopies by increasing MoO 3 or B 2O 3 concentrations. Increasing MoO 3 amount induced an increase of the silicate network reticulation but no significant effect was observed on the proportion of BO4- units and on the distribution of Na + cations in glass structure. By increasing B 2O 3 concentration, a strong evolution of the distribution of Na + cations was observed that could explain the evolution of the nature of molybdate crystals (CaMoO 4 or Na 2MoO 4) formed during melt cooling.

  16. 13C CP/MAS NMR studies of vitamin E model compounds.

    PubMed

    Witkowski, Stanislaw; Paradowska, Katarzyna; Wawer, Iwona

    2004-10-01

    13C cross-polarization magic angle spinning (CP/MAS) NMR data for 2,2,5,7,8-pentamethylchroman-6-ol (2), 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox c) (3) and its acetate (4), 2-methoxy-2,2,5,7,8-pentamethylchroman-6-ol (5), 2-hydroxy-2,2,5,7,8-pentamethylchroman-6-ol (6) and 2,2,5,7,8-pentamethylchroman (7) are reported. A deshielding of 7.7 ppm for the carboxylic carbon was observed in solid Trolox due to formation of intermolecular hydrogen bonds within cyclic dimers. Such crystal packing permits effective cross-polarization and fast relaxation (short T1rho(H)). The impact of the proton concentration on the CP dynamics is reflected by the longer T(CP) and T1rhoH for Trolox-d2 (deuterated at mobile proton sites). The calculated GIAO RHF shielding constants are sensitive to intramolecular effects: rotation around the C-6-O bond (changes of sigma up to 8 ppm) and conformation at C-2.

  17. A very sensitive high-resolution NMR method for quadrupolar nuclei: SPAM-DQF-STMAS.

    PubMed

    Amoureux, Jean-Paul; Flambard, Alexandrine; Delevoye, Laurent; Montagne, Lionel

    2005-07-21

    We show that by combining the intrinsically larger (with respect to MQMAS) efficiency of Double-Quantum Filtered Satellite-Transition MAS (DQF-STMAS), with the large S/N gain of the Soft-Pulse Added Mixing (SPAM) concept, a new very sensitive high-resolution solid-state NMR method can be obtained for semi-integer quadrupolar nuclei.

  18. Magnesium silicate dissolution investigated by Si-29 MAS, H-1-Si-29 CPMAS, Mg-25 QCPMG NMR.

    SciTech Connect

    Davis, M C; Wesolowski, David J

    2009-09-01

    Olivine-(Mg,Fe){sub 2}SiO{sub 4}-has been the subject of frequent investigation in the earth sciences because of its simple structure and rapid dissolution kinetics. Several studies have observed a preferential release of the divalent cation with respect to silicon during weathering under acidic conditions, which has been correlated to the formation of a silicon-rich leached layer. While leached layer formation has been inferred through the changing solution chemistry, a thorough spectroscopic investigation of olivine reacted under acidic conditions has not been conducted. The pure magnesium end member of the olivine series (forsterite-Mg{sub 2}SiO{sub 4}) was chosen for detailed investigations in this study because paramagnetic iron hinders NMR investigations by providing an extra mode of relaxation for neighboring nuclei, causing lineshapes to become significantly broadened and unobservable in the NMR spectrum. For reacting forsterite, spectroscopic interrogations using nuclear magnetic resonance (NMR) can elucidate the changing magnesium coordination and bonding environment. In this study, we combine analysis of the changing solution chemistry with advanced NMR techniques ({sup 29}Si MAS, {sup 1}H-{sup 29}Si CP MAS, {sup 25}Mg QCPMG, and {sup 1}H-{sup 25}Mg CP QCPMG NMR) to probe leached layer formation and secondary phase precipitation during the dissolution of forsterite at 150 C.

  19. DRIFT and HR MAS NMR characterization of humic substances from a soil treated with different organic and mineral fertilizers

    NASA Astrophysics Data System (ADS)

    Ferrari, Erika; Francioso, Ornella; Nardi, Serenella; Saladini, Monica; Ferro, Nicola Dal; Morari, Francesco

    2011-07-01

    In this study, using DRIFT and HR MAS NMR, we analyzed the humic substances isolated from a soil treated, over 40 years, with different organic, mineral and organic plus mineral treatments and cultivated with maize as the main crop. As expected, the structure of humic substances was very complex but by combining both techniques (DRIFT and HR MAS NMR) additional information was obtained on aromatic and aliphatic components, the most recalcitrant parts of these macromolecules. In so doing we wanted to investigate the relationship between HS structure and long-term management practices. An elevated content of lignin, aminoacids, peptides and proteins was observed mainly for farmyard manure treatments with respect to mineral or liquid manure amendments; this supports how the different management practices have greatly influenced the humification process of cultivated soils.

  20. Proton-detected heteronuclear single quantum correlation NMR spectroscopy in rigid solids with ultra-fast MAS.

    PubMed

    Holland, Gregory P; Cherry, Brian R; Jenkins, Janelle E; Yarger, Jeffery L

    2010-01-01

    In this article, we show the potential for utilizing proton-detected heteronuclear single quantum correlation (HSQC) NMR in rigid solids under ultra-fast magic angle spinning (MAS) conditions. The indirect detection of carbon-13 from coupled neighboring hydrogen nuclei provides a sensitivity enhancement of 3- to 4-fold in crystalline amino acids over direct-detected versions. Furthermore, the sensitivity enhancement is shown to be significantly larger for disordered solids that display inhomogeneously broadened carbon-13 spectra. Latrodectus hesperus (Black Widow) dragline silk is given as an example where the sample is mass-limited and the sensitivity enhancement for the proton-detected experiment is 8- to 13-fold. The ultra-fast MAS proton-detected HSQC solid-state NMR technique has the added advantage that no proton homonuclear decoupling is applied during the experiment. Further, well-resolved, indirectly observed carbon-13 spectra can be obtained in some cases without heteronuclear proton decoupling.

  1. Proton-detected heteronuclear single quantum correlation NMR spectroscopy in rigid solids with ultra-fast MAS

    PubMed Central

    Holland, Gregory P.; Cherry, Brian R.; Jenkins, Janelle E.; Yarger, Jeffery L.

    2009-01-01

    In this article, we show the potential for utilizing proton-detected heteronuclear single quantum correlation (HSQC) NMR in rigid solids under ultra-fast magic angle spinning (MAS) conditions. The indirect detection of carbon-13 from coupled neighboring hydrogen nuclei provides a sensitivity enhancement of 3 - 4 fold in crystalline amino acids over direct-detected versions. Furthermore, the sensitivity enhancement is shown to be significantly larger for disordered solids that display inhomogeneously broadened carbon-13 spectra. Latrodectus hesperus (Black Widow) dragline silk is given as an example where the sample is mass-limited and the sensitivity enhancement for the proton-detected experiment is 8 - 13 fold. The ultra-fast MAS proton-detected HSQC solid-state NMR technique has the added advantage that no proton homonuclear decoupling is applied during the experiment. Further, well-resolved, indirectly observed carbon-13 spectra can be obtained in some cases without heteronuclear proton decoupling. PMID:19857977

  2. Partitioning of aluminum atoms in crystallographically non-equivalent tetrahedral sites of the zeolite offretite by 29Si MAS NMR

    NASA Astrophysics Data System (ADS)

    Chen, T. H.; Wang, K. X.; Luo, W. L.; Yuan, Z. Y.; Wang, J. Z.; Ding, D. T.; Li, H. X.; Hu, C.

    1996-04-01

    For the zeolite offretite, a formula is proposed which includes the framework Si/Al ratio ( R), the partitioning ratio of Al over two crystallographically non-equivalent tetrahedral sites ( r) and intensities of the observed peaks in the 29Si MAS NMR spectrum. By this formula, the framework Si/Al ratio of offretite can be estimated from the 29Si MAS NMR spectrum. Combined with chemical analysis of the Si/Al ratio, Al partitioning in two kinds of T sites can also be deduced. It is concluded that the T B sites are favored by Al atoms in parent offretites and Al atoms at T B sites can more easily be substituted isomorphously by Si when treated with (NH 4) 2SiF 6. The formula proposed here is based only on experiments and may be used to testify some statistical models of Al distributions in offretites.

  3. Thermal maturity of type II kerogen from the New Albany Shale assessed by13C CP/MAS NMR

    USGS Publications Warehouse

    Werner-Zwanziger, U.; Lis, G.; Mastalerz, Maria; Schimmelmann, A.

    2005-01-01

    Thermal maturity of oil and gas source rocks is typically quantified in terms of vitrinite reflectance, which is based on optical properties of terrestrial woody remains. This study evaluates 13C CP/MAS NMR parameters in kerogen (i.e., the insoluble fraction of organic matter in sediments and sedimentary rocks) as proxies for thermal maturity in marine-derived source rocks where terrestrially derived vitrinite is often absent or sparse. In a suite of samples from the New Albany Shale (Middle Devonian to the Early Mississippian, Illinois Basin) the abundance of aromatic carbon in kerogen determined by 13C CP/MAS NMR correlates linearly well with vitrinite reflectance. ?? 2004 Elsevier Inc. All rights reserved.

  4. Molecular dynamics of spider dragline silk fiber investigated by 2H MAS NMR.

    PubMed

    Shi, Xiangyan; Holland, Gregory P; Yarger, Jeffery L

    2015-03-09

    The molecular dynamics of the proteins that comprise spider dragline silk were investigated with solid-state (2)H magic angle spinning (MAS) NMR line shape and spin-lattice relaxation time (T1) analysis. The experiments were performed on (2)H/(13)C/(15)N-enriched N. clavipes dragline silk fibers. The silk protein side-chain and backbone dynamics were probed for Ala-rich regions (β-sheet and 31-helical domains) in both native (dry) and supercontracted (wet) spider silk. In native (dry) silk fibers, the side chains in all Ala containing regions undergo similar fast methyl rotations (>10(9) s(-1)), while the backbone remains essentially static (<10(2) s(-1)). When the silk is wet and supercontracted, the presence of water initiates fast side-chain and backbone motions for a fraction of the β-sheet region and 31-helicies. β-Sheet subregion 1 ascribed to the poly(Ala) core exhibits slower dynamics, while β-sheet subregion 2 present in the interfacial, primarily poly(Gly-Ala) region that links the β-sheets to disordered 31-helical motifs, exhibits faster motions when the silk is supercontracted. Particularly notable is the observation of microsecond backbone motions for β-sheet subregion 2 and 31-helicies. It is proposed that these microsecond backbone motions lead to hydrogen-bond disruption in β-sheet subregion 2 and helps to explain the decrease in silk stiffness when the silk is wet and supercontracted. In addition, water mobilizes and softens 31-helical motifs, contributing to the increased extensibility observed when the silk is in a supercontracted state. The present study provides critical insight into the supercontraction mechanism and corresponding changes in mechanical properties observed for spider dragline silks.

  5. MAS-NMR study of lithium zinc silicate glasses and glass-ceramics with various ZnO content

    NASA Astrophysics Data System (ADS)

    Goswami, Madhumita; Kothiyal, Govind P.; Montagne, Lionel; Delevoye, Laurent

    2008-02-01

    Lithium zinc silicate glasses of composition (mol%): 17.5Li 2O-(72- x)SiO 2- xZnO-5.1Na 2O-1.3P 2O 5-4.1B 2O 3, 5.5⩽ x⩽17.7, were prepared by conventional melt-quenched technique and converted to glass-ceramic by controlled crystallization process. 29Si and 31P MAS-NMR was used to characterize the structure of both glass and glass-ceramic samples. Despite the complex glass composition, Q2, Q3 and Q4 sites are identified from 29Si MAS-NMR, which relative intensities are found to vary with the ZnO content, indicating a network depolymerization by ZnO. Moreover, well separated Q3 and Q4 resonances for low ZnO content indicates the occurrence of phase separation. From 31P MAS-NMR, it is seen that phosphorus is mainly present in the form of ortho-( Q0) and pyro-phosphate ( Q1) structural units and variation of ZnO content did not have much effect on these resonances, which provides an additional evidence for phase separation in the glass. On conversion to glass-ceramics, lithium disilicate (Li 2Si 2O 5), lithium zinc ortho-silicate (Li 3Zn 0.5SiO 4), tridymite (SiO 2) and cristobalite (SiO 2) were identified as major silicate crystalline phases. Using 29Si MAS-NMR, quantification of these silicate crystalline phases is carried out and correlated with the ZnO content in the glass-ceramics samples. In addition, 31P spectra unambiguously revealed the presence of crystalline Li 3PO 4 and (Na,Li) 3PO 4 in the glass-ceramics.

  6. Spectral editing through laser-flash excitation in two-dimensional photo-CIDNP MAS NMR experiments

    NASA Astrophysics Data System (ADS)

    Sai Sankar Gupta, Karthick Babu; Daviso, Eugenio; Jeschke, Gunnar; Alia, A.; Ernst, Matthias; Matysik, Jörg

    2014-09-01

    In solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) MAS NMR experiments, strong signal enhancement is observed from molecules forming a spin-correlated radical pair in a rigid matrix. Two-dimensional 13C-13C dipolar-assisted rotational resonance (DARR) photo-CIDNP MAS NMR experiments have been applied to obtain exact chemical shift assignments from those cofactors. Under continuous illumination, the signals are enhanced via three-spin mixing (TSM) and differential decay (DD) and their intensity corresponds to the electron spin density in pz orbitals. In multiple-13C labelled samples, spin diffusion leads to propagation of signal enhancement to all 13C spins. Under steady-state conditions, direct signal assignment is possible due to the uniform signal intensity. The original intensities, however, are inaccessible and the information of the local electron spin density is lost. Upon laser-flash illumination, the signal is enhanced via the classical radical pair mechanism (RPM). The obtained intensities are related to isotropic hyperfine interactions aiso and both enhanced absorptive and emissive lines can be observed due to differences in the sign of the local isotropic hyperfine interaction. Exploiting the mechanism of the polarization, selectivity can be increased by the novel time-resolved two-dimensional dipolar-assisted rotational resonance (DARR) MAS NMR experiment which simplifies the signal assignment compared to complex spectra of the same RCs obtained by continuous illumination. Here we present two-dimensional time-resolved photo-CIDNP MAS NMR experiments providing both directly: signal assignment and spectral editing by sign and strength of aiso. Hence, this experiment provides a direct key to the electronic structure of the correlated radical pair.

  7. Characterization of solid polymer dispersions of active pharmaceutical ingredients by 19F MAS NMR and factor analysis.

    PubMed

    Urbanova, Martina; Brus, Jiri; Sedenkova, Ivana; Policianova, Olivia; Kobera, Libor

    2013-01-01

    In this contribution the ability of (19)F MAS NMR spectroscopy to probe structural variability of poorly water-soluble drugs formulated as solid dispersions in polymer matrices is discussed. The application potentiality of the proposed approach is demonstrated on a moderately sized active pharmaceutical ingredient (API, Atorvastatin) exhibiting extensive polymorphism. In this respect, a range of model systems with the API incorporated in the matrix of polvinylpyrrolidone (PVP) was prepared. The extent of mixing of both components was determined by T(1)((1)H) and T(1ρ)((1)H) relaxation experiments, and it was found that the API forms nanosized domains. Subsequently it was found out that the polymer matrix induces two kinds of changes in (19)F MAS NMR spectra. At first, this is a high-frequency shift reaching 2-3 ppm which is independent on molecular structure of the API and which results from the long-range polarization of the electron cloud around (19)F nucleus induced by electrostatic fields of the polymer matrix. At second, this is broadening of the signals and formation of shoulders reflecting changes in molecular arrangement of the API. To avoid misleading in the interpretation of the recorded (19)F MAS NMR spectra, because both the contributions act simultaneously, we applied chemometric approach based on multivariate analysis. It is demonstrated that factor analysis of the recorded spectra can separate both these spectral contributions, and the subtle structural differences in the molecular arrangement of the API in the nanosized domains can be traced. In this way (19)F MAS NMR spectra of both pure APIs and APIs in solid dispersions can be directly compared. The proposed strategy thus provides a powerful tool for the analysis of new formulations of fluorinated pharmaceutical substances in polymer matrices.

  8. Characterization of solid polymer dispersions of active pharmaceutical ingredients by 19F MAS NMR and factor analysis

    NASA Astrophysics Data System (ADS)

    Urbanova, Martina; Brus, Jiri; Sedenkova, Ivana; Policianova, Olivia; Kobera, Libor

    In this contribution the ability of 19F MAS NMR spectroscopy to probe structural variability of poorly water-soluble drugs formulated as solid dispersions in polymer matrices is discussed. The application potentiality of the proposed approach is demonstrated on a moderately sized active pharmaceutical ingredient (API, Atorvastatin) exhibiting extensive polymorphism. In this respect, a range of model systems with the API incorporated in the matrix of polvinylpyrrolidone (PVP) was prepared. The extent of mixing of both components was determined by T1(1H) and T1ρ(1H) relaxation experiments, and it was found that the API forms nanosized domains. Subsequently it was found out that the polymer matrix induces two kinds of changes in 19F MAS NMR spectra. At first, this is a high-frequency shift reaching 2-3 ppm which is independent on molecular structure of the API and which results from the long-range polarization of the electron cloud around 19F nucleus induced by electrostatic fields of the polymer matrix. At second, this is broadening of the signals and formation of shoulders reflecting changes in molecular arrangement of the API. To avoid misleading in the interpretation of the recorded 19F MAS NMR spectra, because both the contributions act simultaneously, we applied chemometric approach based on multivariate analysis. It is demonstrated that factor analysis of the recorded spectra can separate both these spectral contributions, and the subtle structural differences in the molecular arrangement of the API in the nanosized domains can be traced. In this way 19F MAS NMR spectra of both pure APIs and APIs in solid dispersions can be directly compared. The proposed strategy thus provides a powerful tool for the analysis of new formulations of fluorinated pharmaceutical substances in polymer matrices.

  9. Colloidal Double Quantum Dots

    PubMed Central

    2016-01-01

    Conspectus Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole–dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single

  10. Colloidal Double Quantum Dots.

    PubMed

    Teitelboim, Ayelet; Meir, Noga; Kazes, Miri; Oron, Dan

    2016-05-17

    Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole-dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon

  11. Effects of fluoride on in vitro enamel demineralization analyzed by ¹⁹F MAS-NMR.

    PubMed

    Mohammed, N R; Kent, N W; Lynch, R J M; Karpukhina, N; Hill, R; Anderson, P

    2013-01-01

    The mechanistic action of fluoride on inhibition of enamel demineralization was investigated using (19)F magic angle spinning nuclear magnetic resonance (MAS-NMR). The aim of this study was to monitor the fluoride-mineral phase formed on the enamel as a function of the concentration of fluoride ions [F(-)] in the demineralizing medium. The secondary aim was to investigate fluorapatite formation on enamel in the mechanism of fluoride anti-caries efficacy. Enamel blocks were immersed into demineralization solutions of 0.1 M acetic acid (pH 4) with increasing concentrations of fluoride up to 2,262 ppm. At and below 45 ppm [F(-)] in the solution, (19)F MAS-NMR showed fluoride-substituted apatite formation, and above 45 ppm, calcium fluoride (CaF2) formed in increasing proportions. Further increases in [F(-)] caused no further reduction in demineralization, but increased the proportion of CaF2 formed. Additionally, the combined effect of strontium and fluoride on enamel demineralization was also investigated using (19)F MAS-NMR. The presence of 43 ppm [Sr(2+)] in addition to 45 ppm [F(-)] increases the fraction of fluoride-substituted apatite, but delays formation of CaF2 when compared to the demineralization of enamel in fluoride-only solution.

  12. 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.

  13. Solid-state (13)C CP MAS NMR spectroscopy of mushrooms gives directly the ratio between proteins and polysaccharides.

    PubMed

    Pizzoferrato, L; Manzi, P; Bertocchi, F; Fanelli, C; Rotilio, G; Paci, M

    2000-11-01

    The solid-state (13)C CP MAS NMR technique has the potential of monitoring the chemical composition in the solid state of an intact food sample. This property has been utilized to study mushrooms of different species (Pleurotus ostreatus, Pleurotus eryngii, Pleurotus pulmunarius, and Lentinula edodes), already characterized by chemical analyses for protein and dietary fiber components. Solid-state (13)C CP MAS NMR spectroscopy reveals a large difference in the ratio between the glucidic and the proteic resonances probably depending on the mushroom species. An accurate inspection by model compounds and suitable mixtures of proteins and saccharides gives a methodology to interpret these experimental data. A good correlation (R(2) = 0.93; R(2) = 0.81) has been obtained by comparing the NMR data with the results of the chemical analyses. The results suggest the possibility to perform a taxonomic study and/or a nutritional study on the basis of the ratio between protein and polysaccharide levels determined by NMR or chemical methodologies.

  14. Study of phase transition mechanisms in [N(CH3)4]2ZnCl4 by static NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Lim, Kye-Young

    2014-05-01

    The temperature dependences of chemical shifts, intensities, the spin-lattice relaxation time in laboratory frame T1, and in rotating frame T1ρ were measured for 1H and 13C in [N(CH3)4]2ZnCl4 by single-crystal NMR and MAS NMR. The unit cell in phase I contains two chemically inequivalent types of N(CH3)4 ions. However, the two chemically different ions N(CH3)4 cannot be practically identified from the 13C NMR spectrum. The structural changes for 1H and 13C were measured near Ti and TC4. The existence of chemically equivalent N(CH3)4 ions in phase I and the existence of the ferroelastic characteristic of the N(CH3)4 ions in phases IV and V are discussed.

  15. Determination of the structural changes by Raman and {sup 13}C CP/MAS NMR spectroscopy on native corn starch with plasticizers

    SciTech Connect

    Cozar, O.; Filip, C.; Tripon, C.; Cioica, N.; Coţa, C.; Nagy, E. M.

    2013-11-13

    The plasticizing - antiplasticizing effect of water and glycerol contents on native corn starch samples is investigated by FT-Raman and {sup 13}C CP/MAS NMR spectroscopy. The presence of both amorphous and crystalline structural phases was evidenced in pure native corn starch and also in the samples containing plasticizers. Among the crystalline starch structures, the A- and V- types were suggested by CP/MAS NMR spectra.

  16. Quantitation of crystalline material within a liquid vehicle using 1H/19F CP/MAS NMR.

    PubMed

    Farrer, Brian T; Peresypkin, Andrey; Wenslow, Robert M

    2007-02-01

    A method to detect and quantify a small amount crystalline material within a liquid solution of solubilized material is described. 19F CP-MAS ssNMR was investigated as a technique to detect low levels (0.2 mg/g) of crystalline sodium (2R)-7-{3-[2-chloro-4-(2,2,2-trifluoroethoxy)phenoxy]propoxy}-2-methyl-3,4-dihydro-2H-chromane-2-carboxylate (I) within a solid mixture (with microcrystalline cellulose) and a slurry with a liquid vehicle (capric and caprylic acid triglycerides). The results demonstrate that the area of the 19F CP/MAS signal obtained in 25 min at 25 degrees C is linearly dependent (R2=0.997) on the mass of I within the ssNMR rotor. Slopes of CP-MAS peak area versus mass of I in the rotor were nearly identical for the solid mixture and slurry suspension. Signal-to-noise ratio for the low potency slurry suggest detection and quantitation of 0.1 mg of crystalline I in the rotor, corresponding to 2 mg/g of crystalline material within the slurry suspension.

  17. 1H HR-MAS NMR Spectroscopy and the Metabolite Determination of Typical Foods in Mediterranean Diet

    PubMed Central

    Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Ferrantelli, Vincenzo; Dugo, Giacomo; Cicero, Nicola

    2015-01-01

    NMR spectroscopy has become an experimental technique widely used in food science. The experimental procedures that allow precise and quantitative analysis on different foods are relatively simple. For a better sensitivity and resolution, NMR spectroscopy is usually applied to liquid sample by means of extraction procedures that can be addressed to the observation of particular compounds. For the study of semisolid systems such as intact tissues, High-Resolution Magic Angle Spinning (HR-MAS) has received great attention within the biomedical area and beyond. Metabolic profiling and metabolism changes can be investigated both in animal organs and in foods. In this work we present a proton HR-MAS NMR study on the typical vegetable foods of Mediterranean diet such as the Protected Geographical Indication (PGI) cherry tomato of Pachino, the PGI Interdonato lemon of Messina, several Protected Designation of Origin (PDO) extra virgin olive oils from Sicily, and the Traditional Italian Food Product (PAT) red garlic of Nubia. We were able to identify and quantify the main metabolites within the studied systems that can be used for their characterization and authentication. PMID:26495154

  18. (1)H HR-MAS NMR Spectroscopy and the Metabolite Determination of Typical Foods in Mediterranean Diet.

    PubMed

    Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Ferrantelli, Vincenzo; Dugo, Giacomo; Cicero, Nicola

    2015-01-01

    NMR spectroscopy has become an experimental technique widely used in food science. The experimental procedures that allow precise and quantitative analysis on different foods are relatively simple. For a better sensitivity and resolution, NMR spectroscopy is usually applied to liquid sample by means of extraction procedures that can be addressed to the observation of particular compounds. For the study of semisolid systems such as intact tissues, High-Resolution Magic Angle Spinning (HR-MAS) has received great attention within the biomedical area and beyond. Metabolic profiling and metabolism changes can be investigated both in animal organs and in foods. In this work we present a proton HR-MAS NMR study on the typical vegetable foods of Mediterranean diet such as the Protected Geographical Indication (PGI) cherry tomato of Pachino, the PGI Interdonato lemon of Messina, several Protected Designation of Origin (PDO) extra virgin olive oils from Sicily, and the Traditional Italian Food Product (PAT) red garlic of Nubia. We were able to identify and quantify the main metabolites within the studied systems that can be used for their characterization and authentication.

  19. Qualitative and quantitative study of the highly specialized lipid tissues of cetaceans using HR-MAS NMR and classical GC.

    PubMed

    Jung, Jean-Luc; Simon, Gaelle; Alfonsi, Eric; Thoraval, Didier; Kervarec, Nelly; Ben Salem, Douraied; Hassani, Sami; Domergue, Frédéric

    2017-01-01

    Cetacean adipose tissues contain an extremely very wide variety of acyl-chains present in triacylglycerols and / or wax esters. In addition, changes in the lipid composition across organs suggest fine stratification. It therefore remains technically challenging to describe precisely the lipid organization of these tissues. In the present study, we used in parallel HR-MAS NMR (High Resolution Magic Angle Spinning Nuclear Magnetic Resonance) and GC (gas-chromatography) to characterize and quantify the lipids and fatty acyl-chains from the blubber and melon of two odontocete species. Both methods generated very similar compositions, but each presented clear advantages. While GC underestimated the amount of short branched fatty acyl-chains, which are specific to cetacean adipose tissues and most probably of primary importance for their functioning, HR-MAS NMR allowed for their exact quantification. Conversely, when HR-MAS NMR could only discriminate a few types of fatty acyl-chain families, GC unambiguously identified and quantified most of them. In addition, this technique allowed for the determination of the wax esters molecular species. Our results further suggest that the stratification of these adipose tissues relies on changes in the triacylglycerol to wax ester ratio and in the fatty acyl composition of triacylglycerols, but not on changes in the wax esters composition. Altogether, our data show that the complementarities of these two approaches result in lipid analyses of unprecedented precision, paving the way for the detailed description of the fatty acyl composition of cetacean adipose tissues and the understanding of their functioning.

  20. Microscopic structural analysis of fractured silk fibers from Bombyx mori and Samia cynthia ricini using 13C CP/MAS NMR with a 1mm microcoil MAS NMR probehead.

    PubMed

    Yamauchi, Kazuo; Yamasaki, Shizuo; Takahashi, Rui; Asakura, Tetsuo

    2010-07-01

    Conformational changes have been studied in silk fibers from the domestic silkworm Bombyx mori and a wild silkworm Samia cynthia ricini as a result of fractured by stretching. About 300 samples consisting of only the fractured regions of [1-13C]Ala or [1-13C]Gly labeled silk fibers were collected and observed by 13C CP/MAS NMR spectra. The total amount of these fractured fibers is only about 1mg and therefore we used a home-built 1mm microcoil MAS NMR probehead. A very small increase in the fraction of random coil was noted for the alanine regions of both silk fibroins and for the glycine region of B. mori silk fibroin. However, there is no difference in the spectra before and after fractured for the glycine region of S. c. ricini silk fibroin. Thus, the influence of fracture occurs exclusively at the Ala region for S. c. ricini. The relationship between sequence, fracture and structure is discussed.

  1. 31P MAS NMR: a useful tool for the evaluation of VX natural weathering in various urban matrixes.

    PubMed

    Mizrahi, Dana M; Columbus, Ishay

    2005-11-15

    The fate of chemical warfare agent VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate) in various urban matrixes was monitored utilizing 31P MAS NMR. Chosen matrixes represent buildings, roads, pavement, and earth found in urban environments. In view of the high toxicity of VX, solid state NMR afforded a fairly safe experimental mode, omitting any chance for evaporation. Moreover, due to the nondestructive nature of these experiments, measurements could be repeated over and over using the same samples. Degradation rates of VX were obtained and compared to provide a list of relative reactivity toward VX: concrete > desert sand > beach sand > asphalt approximately to bitumen sheet. Chemical interactions between VX, its degradation products, and the matrixes were often expressed by widening of the peaks to the extent that mass balance could not be achieved. It is noteworthy that these experiments were usually carried out on crushed or milled specimens, allowing high reactivity and rapid reactions.

  2. (1)H HR-MAS NMR-based metabolomics study of different persimmon cultivars (Diospyros kaki) during fruit development.

    PubMed

    Santos, Alan Diego da Conceição; Fonseca, Flávia Aparecida; Dutra, Lívia Macedo; Santos, Maria de Fátima Costa; Menezes, Leociley Rocha Alencar; Campos, Francinete Ramos; Nagata, Noemi; Ayub, Ricardo; Barison, Andersson

    2018-01-15

    (1)H HR-MAS NMR spectroscopy was used to track the metabolic changes throughout the whole development of astringent ('Giombo') and non-astringent ('Fuyu') cultivars of persimmon (Diospyros kaki). The NMR data revealed the low concentration of amino acids (threonine, alanine, citrulline and GABA) and organic acids (malic acid). In addition, the signals of carbohydrates (sucrose, glucose and fructose) seemed to play the most important role in the fruit development. In both cultivars, the growth was characterized by fluctuating sucrose concentration along with a constant increase in both glucose and fructose. In the initial growth stage, the polyphenol composition was quite different between the cultivars. Gallic acid was detected throughout the growth of 'Giombo', while for 'Fuyu', signals of polyphenols disappeared over time. Additional multivariate analysis suggested that these cultivars share many metabolic similarities during development. These findings might help the comprehension of fruit development, which in turn, impacts the quality of the fruits. Copyright © 2017. Published by Elsevier Ltd.

  3. Quantification of ammonia binding sites in Davison (Type 3A) zeolite desiccant : a solid-state Nitrogen-15 MAS NMR spectroscopy investigation.

    SciTech Connect

    Alam, Todd Michael; Holland, Gregory P.; Cherry, Brian Ray

    2004-01-01

    The quantitative analysis of ammonia binding sites in the Davison (Type 3A) zeolite desiccant using solid-state {sup 15}N MAS NMR spectroscopy is reported. By utilizing 15N enriched ammonia ({sup 15}NH{sub 3}) gas, the different adsorption/binding sites within the zeolite were investigated as a function of NH{sub 3} loading. Using {sup 15}N MAS NMR multiple sites were resolved that have distinct cross-polarization dynamics and chemical shift behavior. These differences in the {sup 15}N NMR were used to characterize the adsorption environments in both the pure 3A zeolite and the silicone-molded forms of the desiccant.

  4. Domains in Binary SOPC/POPE Lipid Mixtures Studied by Pulsed Field Gradient 1H MAS NMR

    PubMed Central

    Polozov, Ivan V.; Gawrisch, Klaus

    2004-01-01

    We studied domain formation in mixtures of the monounsaturated lipids SOPC and POPE as a function of temperature and composition by NMR. Magic angle spinning at kHz frequencies restored resolution of 1H NMR lipid resonances in the fluid phase, whereas the linewidth of gel-phase lipids remained rather broad and spinning frequency dependent. In regions of fluid- and gel-phase coexistence, spectra are a superposition of resonances from fluid and gel domains, as indicated by the existence of isosbestic points. Quantitative determination of the amount of lipid in the coexisting phases is straightforward and permitted construction of a binary phase diagram. Lateral rates of lipid diffusion were determined by 1H MAS NMR with pulsed field gradients. At the onset of the phase transition near 25°C apparent diffusion rates became diffusion time dependent, indicating that lipid movement is obstructed by the formation of gel-phase domains. A percolation threshold at which diffusion of fluid-phase lipid becomes confined to micrometer-size domains was observed when ∼40% of total lipid had entered the gel phase. The results indicate that common phosphatidylethanolamines may trigger domain formation in membranes within a physiologically relevant temperature range. This novel NMR approach may aid the study of lipid rafts. PMID:15345553

  5. An investigation into the structure and reactivity of calcium-zinc-silicate ionomer glasses using MAS-NMR spectroscopy.

    PubMed

    Boyd, D; Towler, M R; Law, R V; Hill, R G

    2006-05-01

    The suitability of Glass Polyalkenoate Cements (GPCs) for orthopaedic applications is retarded by the presence in the glass phase of aluminium, a neurotoxin. Unfortunately, the aluminium ion plays an integral role in the setting process of GPCs and its absence is likely to hinder cement formation. However, the authors have previously shown that aluminium-free GPCs may be formulated based on calcium zinc silicate glasses and these novel materials exhibit significant potential as hard tissue biomaterials. However there is no data available on the structure of these glasses. (29)Si MAS-NMR, differential thermal analysis (DTA), X-ray diffraction (XRD), and network crosslink density (CLD) calculations were used to characterize the structure of five calcium zinc silicate glasses and relate glass structure to reactivity. The results indicate that glasses capable of forming Zn-GPCs are predominantly Q(2)/Q(3) in structure with corresponding network crosslink densities greater than 2. The correlation of CLD and MAS-NMR results indicate the primary role of zinc in these simple glass networks is as a network modifier and not an intermediate oxide; this fact will allow for more refined glass compositions, with less reactive structures, to be formulated in the future.

  6. CaCl 2 -Accelerated Hydration of Tricalcium Silicate: A STXM Study Combined with 29 Si MAS NMR

    DOE PAGES

    Li, Qinfei; Ge, Yong; Geng, Guoqing; ...

    2015-01-01

    Tmore » he effect of calcium chloride (CaCl 2 ) on tricalcium silicate (C 3 S) hydration was investigated by scanning transmission X-ray microscopy (STXM) with Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra and 29 Si MAS NMR. STXM is demonstrated to be a powerful tool for studying the chemical composition of a cement-based hydration system.he Ca L 3,2 -edge NEXAFS spectra obtained by examining C 3 S hydration in the presence of CaCl 2 showed that this accelerator does not change the coordination of calcium in the calcium silicate hydrate (C-S-H), which is the primary hydration product. O K-edge NEXAFS is also very useful in distinguishing the chemical components in hydrated C 3 S. Based on the Ca L 3,2 -edge spectra and chemical component mapping, we concluded that CaCl 2 prefers to coexist with unhydrated C 3 S instead of C-S-H. In Si K-edge NEXAFS analysis, CaCl 2 increases the degree of silicate polymerization of C-S-H in agreement with the 29 Si CP/MAS NMR results, which show that the presence of CaCl 2 in hydrated C 3 S considerably accelerates the formation of middle groups ( Q 2 ) and branch sites ( Q 3 ) in the silicate chains of C-S-H gel at 1-day hydration.« less

  7. Site-resolved 2H relaxation experiments in solid materials by global line-shape analysis of MAS NMR spectra

    NASA Astrophysics Data System (ADS)

    Lindh, E. L.; Stilbs, P.; Furó, I.

    2016-07-01

    We investigate a way one can achieve good spectral resolution in 2H MAS NMR experiments. The goal is to be able to distinguish between and study sites in various deuterated materials with small chemical shift dispersion. We show that the 2H MAS NMR spectra recorded during a spin-relaxation experiment are amenable to spectral decomposition because of the different evolution of spectral components during the relaxation delay. We verify that the results are robust by global least-square fitting of the spectral series both under the assumption of specific line shapes and without such assumptions (COmponent-REsolved spectroscopy, CORE). In addition, we investigate the reliability of the developed protocol by analyzing spectra simulated with different combinations of spectral parameters. The performance is demonstrated in a model material of deuterated poly(methacrylic acid) that contains two 2H spin populations with similar chemical shifts but different quadrupole splittings. In 2H-exchanged cellulose containing two 2H spin populations with very similar chemical shifts and quadrupole splittings, the method provides new site-selective information about the molecular dynamics.

  8. MAS NMR of the Drug Resistant S31N M2 Proton Transporter from Influenza A

    PubMed Central

    Andreas, Loren B.; Eddy, Matthew T.; Chou, James J.; Griffin, Robert G.

    2012-01-01

    We report chemical shift assignments of the drug-resistant S31N mutant of M218-60 determined with magic angle spinning (MAS) 3D spectra acquired with a 15N-13C ZF-TEDOR transfer followed by 13C-13C mixing by RFDR. The MAS spectra reveal two sets of resonances, indicating that the tetramer assembles as a dimer of dimers, similar to the wild type channel. The two sets of chemical shifts are shown to be in close proximity at residue H37, and assignments reveal a difference in the helix torsion angles, as predicted by TALOS+, for the key resistance residue N31. In contrast to wild type M218-60, chemical shift changes are minimal with addition of the inhibitor rimantadine, suggesting that the drug does not bind to S31N. PMID:22480220

  9. Polydisperse methyl β-cyclodextrin–epichlorohydrin polymers: variable contact time 13C CP-MAS solid-state NMR characterization

    PubMed Central

    Mallard, Isabelle; Baudelet, Davy; Castiglione, Franca; Ferro, Monica; Panzeri, Walter; Ragg, Enzio

    2015-01-01

    Summary The polymerization of partially methylated β-cyclodextrin (CRYSMEB) with epichlorohydrin was carried out in the presence of a known amount of toluene as imprinting agent. Three different preparations (D1, D2 and D3) of imprinted polymers were obtained and characterized by solid-state 13C NMR spectroscopy under cross-polarization magic angle spinning (CP-MAS) conditions. The polymers were prepared by using the same synthetic conditions but with different molar ratios of imprinting agent/monomer, leading to morphologically equivalent materials but with different absorption properties. The main purpose of the work was to find a suitable spectroscopic descriptor accounting for the different imprinting process in three homogeneous polymeric networks. The polymers were characterized by studying the kinetics of the cross-polarization process. This approach is based on variable contact time CP-MAS spectra, referred to as VCP-MAS. The analysis of the VCP-MAS spectra provided two relaxation parameters: T CH (the CP time constant) and T 1ρ (the proton spin-lattice relaxation time in the rotating frame). The results and the analysis presented in the paper pointed out that T CH is sensitive to the imprinting process, showing variations related to the toluene/cyclodextrin molar ratio used for the preparation of the materials. Conversely, the observed values of T 1ρ did not show dramatic variations with the imprinting protocol, but rather confirmed that the three polymers are morphologically similar. Thus the combined use of T CH and T 1ρ can be helpful for the characterization and fine tuning of imprinted polymeric matrices. PMID:26877800

  10. Polydisperse methyl β-cyclodextrin-epichlorohydrin polymers: variable contact time (13)C CP-MAS solid-state NMR characterization.

    PubMed

    Mallard, Isabelle; Baudelet, Davy; Castiglione, Franca; Ferro, Monica; Panzeri, Walter; Ragg, Enzio; Mele, Andrea

    2015-01-01

    The polymerization of partially methylated β-cyclodextrin (CRYSMEB) with epichlorohydrin was carried out in the presence of a known amount of toluene as imprinting agent. Three different preparations (D1, D2 and D3) of imprinted polymers were obtained and characterized by solid-state (13)C NMR spectroscopy under cross-polarization magic angle spinning (CP-MAS) conditions. The polymers were prepared by using the same synthetic conditions but with different molar ratios of imprinting agent/monomer, leading to morphologically equivalent materials but with different absorption properties. The main purpose of the work was to find a suitable spectroscopic descriptor accounting for the different imprinting process in three homogeneous polymeric networks. The polymers were characterized by studying the kinetics of the cross-polarization process. This approach is based on variable contact time CP-MAS spectra, referred to as VCP-MAS. The analysis of the VCP-MAS spectra provided two relaxation parameters: T CH (the CP time constant) and T 1ρ (the proton spin-lattice relaxation time in the rotating frame). The results and the analysis presented in the paper pointed out that T CH is sensitive to the imprinting process, showing variations related to the toluene/cyclodextrin molar ratio used for the preparation of the materials. Conversely, the observed values of T 1ρ did not show dramatic variations with the imprinting protocol, but rather confirmed that the three polymers are morphologically similar. Thus the combined use of T CH and T 1ρ can be helpful for the characterization and fine tuning of imprinted polymeric matrices.

  11. Low-power XiX decoupling in MAS NMR experiments.

    PubMed

    Ernst, Matthias; Samoson, Ago; Meier, Beat H

    2003-08-01

    Low-power XiX proton decoupling under fast magic-angle spinning is introduced. The method is applicable if the MAS frequency exceeds the proton-proton interactions. For rigid organic solids this is the case for MAS frequencies above approximately 40 kHz. It is shown that the quality of the decoupling as well as the sensitivity to frequency offsets can be improved compared to low-power continuous-wave decoupling. The decoupling efficiency is somewhat reduced compared to optimized high-power decoupling: in a peptide sample investigated at an MAS frequency of 50 kHz a loss of about 10% in signal intensity for CH3 and CH groups, and of about 40% for CH2 groups was observed. Taking into consideration, that the rf amplitude in the low-power XiX was about 15 times lower than in high-power XiX decoupling, such a reduction in line intensity is sometimes tolerable.

  12. High-resolution proton-detected NMR of proteins at very fast MAS

    NASA Astrophysics Data System (ADS)

    Andreas, Loren B.; Le Marchand, Tanguy; Jaudzems, Kristaps; Pintacuda, Guido

    2015-04-01

    When combined with high-frequency (currently ∼60 kHz) magic-angle spinning (MAS), proton detection boosts sensitivity and increases coherence lifetimes, resulting in narrow 1H lines. Herein, we review methods for efficient proton detected techniques and applications in highly deuterated proteins, with an emphasis on 100% selected 1H site concentration for the purpose of sensitivity. We discuss the factors affecting resolution and sensitivity that have resulted in higher and higher frequency MAS. Next we describe the various methods that have been used for backbone and side-chain assignment with proton detection, highlighting the efficient use of scalar-based 13C-13C transfers. Additionally, we show new spectra making use of these schemes for side-chain assignment of methyl 13C-1H resonances. The rapid acquisition of resolved 2D spectra with proton detection allows efficient measurement of relaxation parameters used as a measure of dynamic processes. Under rapid MAS, relaxation times can be measured in a site-specific manner in medium-sized proteins, enabling the investigation of molecular motions at high resolution. Additionally, we discuss methods for measurement of structural parameters, including measurement of internuclear 1H-1H contacts and the use of paramagnetic effects in the determination of global structure.

  13. High-resolution proton-detected NMR of proteins at very fast MAS.

    PubMed

    Andreas, Loren B; Le Marchand, Tanguy; Jaudzems, Kristaps; Pintacuda, Guido

    2015-04-01

    When combined with high-frequency (currently ∼60 kHz) magic-angle spinning (MAS), proton detection boosts sensitivity and increases coherence lifetimes, resulting in narrow ((1))H lines. Herein, we review methods for efficient proton detected techniques and applications in highly deuterated proteins, with an emphasis on 100% selected ((1))H site concentration for the purpose of sensitivity. We discuss the factors affecting resolution and sensitivity that have resulted in higher and higher frequency MAS. Next we describe the various methods that have been used for backbone and side-chain assignment with proton detection, highlighting the efficient use of scalar-based ((13))C-((13))C transfers. Additionally, we show new spectra making use of these schemes for side-chain assignment of methyl ((13))C-((1))H resonances. The rapid acquisition of resolved 2D spectra with proton detection allows efficient measurement of relaxation parameters used as a measure of dynamic processes. Under rapid MAS, relaxation times can be measured in a site-specific manner in medium-sized proteins, enabling the investigation of molecular motions at high resolution. Additionally, we discuss methods for measurement of structural parameters, including measurement of internuclear ((1))H-((1))H contacts and the use of paramagnetic effects in the determination of global structure.

  14. Phase cycling schemes for finite-pulse-RFDR MAS solid state NMR experiments

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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 inhomogeneity 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

  15. Phase cycling schemes for finite-pulse-RFDR MAS solid state NMR experiments.

    PubMed

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

    2015-03-01

    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, XY4(1)4, for the fp-RFDR pulse sequence employed in 2D (1)H/(1)H 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, XY4(1)2, XY4(1)3, XY4(1)4, and XY8(1)4 phase cycles under different spinning speeds ranging from 10 to 100 kHz. The theoretical calculations reveal the presence of second-order terms (T(10)T(2,±2), T(1,±1)T(2,±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 inhomogeneity effects revealed that XY4(1)4 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

  16. 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

  17. Magnetic susceptibility effects on 13C MAS NMR spectra of carbon materials and graphite.

    PubMed

    Freita, J C; Emmerich, F G; Cernicchiaro, G R; Sampaio, L C; Bonagamba, T J

    2001-01-01

    13C high-resolution solid-state nuclear magnetic resonance (NMR) was employed to study carbon materials prepared through the thermal decomposition of four different organic precursors (rice hulls, endocarp of babassu coconut, peat, and PVC). For heat treatment temperatures (HTTs) above about 600 C, all materials presented 13C NMR spectra composed of a unique resonance line associated with carbon atoms in aromatic planes. With increasing HTT a continuous broadening of this resonance and a diamagnetic shift in its central frequency were verified for all samples. The evolution of the magnitude and anisotropy of the magnetic susceptibility of the heat-treated carbon samples with HTT explains well these findings. It is shown that these results are better understood when a comparison is made with the features of the 13C NMR spectrum of polycrystalline graphite, for which the magnetic susceptibility effect is also present and is much more pronounced.

  18. Acceleration of natural-abundance solid-state MAS NMR measurements on bone by paramagnetic relaxation from gadolinium-DTPA

    NASA Astrophysics Data System (ADS)

    Mroue, Kamal H.; Zhang, Rongchun; Zhu, Peizhi; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

    2014-07-01

    Reducing the data collection time without affecting the signal intensity and spectral resolution is one of the major challenges for the widespread application of multidimensional nuclear magnetic resonance (NMR) spectroscopy, especially in experiments conducted on complex heterogeneous biological systems such as bone. In most of these experiments, the NMR data collection time is ultimately governed by the proton spin-lattice relaxation times (T1). For over two decades, gadolinium(III)-DTPA (Gd-DTPA, DTPA = Diethylene triamine pentaacetic acid) has been one of the most widely used contrast-enhancement agents in magnetic resonance imaging (MRI). In this study, we demonstrate that Gd-DTPA can also be effectively used to enhance the longitudinal relaxation rates of protons in solid-state NMR experiments conducted on bone without significant line-broadening and chemical-shift-perturbation side effects. Using bovine cortical bone samples incubated in different concentrations of Gd-DTPA complex, the 1H T1 values were calculated from data collected by 1H spin-inversion recovery method detected in natural-abundance 13C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the 1H T1 values can be successfully reduced by a factor of 3.5 using as low as 10 mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the 13C CPMAS spectra. These results obtained from 13C-detected CPMAS experiments were further confirmed using 1H-detected ultrafast MAS experiments on Gd-DTPA doped bone samples. This approach considerably improves the signal-to-noise ratio per unit time of NMR experiments applied to bone samples by reducing the experimental time required to acquire the same number of scans.

  19. High-field 19.6 T 27Al solid-state MAS NMR of in vitro aluminated brain tissue

    NASA Astrophysics Data System (ADS)

    Bryant, Pamela L.; Lukiw, Walter J.; Gan, Zhehong; Hall, Randall W.; Butler, Leslie G.

    2004-10-01

    The combination of 27Al high-field solid-state NMR (19.6 T) with rapid spinning speeds (17.8 kHz) is used to acquire 27Al NMR spectra of total RNA human brain temporal lobe tissues exposed to 0.10 mM Al 3+ (as AlCl 3) and of human retinal pigment epithelial cells (ARPE-19), grown in 0.10 mM AlCl 3. The spectra of these model systems show multiple Al 3+ binding sites, good signal/noise ratios and apparent chemical shift dispersions. A single broad peak (-3 to 11 ppm) is seen for the aluminated ARPE-19 cells, consistent with reported solution-state NMR chemical shifts of Al-transferrin. The aluminated brain tissue has a considerably different 27Al MAS NMR spectrum. In addition to the transferrin-type resonance, additional peaks are seen. Tentative assignments include: -9 to -3 ppm, octahedral AlO 6 (phosphate and water); 9 ppm, condensed AlO 6 units (Al-O-Al bridges); 24 ppm, tetrahedral AlO 3N and/or octahedral Al-carbonate; and 35 ppm, more N-substituted aluminum and /or tetrahedral AlO 4. Thus, brain tissue is susceptible to a broad range of coordination by aluminum. Furthermore, the moderate 27Al C Q values (all less than 10 MHz) suggest future NMR studies may be performed at 9.4 T and a spin rate of 20 kHz.

  20. 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

  1. Semiconductor double quantum dot micromaser.

    PubMed

    Liu, Y-Y; Stehlik, J; Eichler, C; Gullans, M J; Taylor, J M; Petta, J R

    2015-01-16

    The coherent generation of light, from masers to lasers, relies upon the specific structure of the individual emitters that lead to gain. Devices operating as lasers in the few-emitter limit provide opportunities for understanding quantum coherent phenomena, from terahertz sources to quantum communication. Here we demonstrate a maser that is driven by single-electron tunneling events. Semiconductor double quantum dots (DQDs) serve as a gain medium and are placed inside a high-quality factor microwave cavity. We verify maser action by comparing the statistics of the emitted microwave field above and below the maser threshold. Copyright © 2015, American Association for the Advancement of Science.

  2. Metabolic Profiling of Cells in Response to Drug Treatment using (1)H High-resolution Magic Angle Spinning (HR-MAS) NMR Spectroscopy.

    PubMed

    Vermathen, Martina; Diserens, Gaëlle; Vermathen, Peter; Furrer, Julien

    2017-03-29

    High-resolution magic angle spinning (HR-MAS) is an NMR technique that provides access to well resolved liquid-like 1H NMR spectra of semi-solid samples. Therefore, 1H HR-MAS NMR spectroscopy has become an important tool for the direct analysis of biological samples such as tissues and cells in a mostly non-destructive way. Here, we focus on the application of HR-MAS NMR combined with multivariate statistical methods used for metabolic profiling of cells and in particular for the study of cellular metabolic responses to drug exposure. The principles of HR-MAS and the metabolomic approach are briefly described. As an example, a study on the metabolic response of different cell types towards treatment with a highly cytotoxic hexacationic ruthenium metallaprism as potential anti-cancer drug is presented. Specific metabolites and metabolic pathways are suggested to be associated with the cellular response. The study demonstrates the potential of HR-MAS metabolomics applied to cells for addressing the intracellular processes involved in the treatment with organometallic drugs.

  3. 13C MAS NMR studies of the effects of hydration on the cell walls of potatoes and Chinese water chestnuts.

    PubMed

    Tang, H; Belton, P S; Ng, A; Ryden, P

    1999-02-01

    13C NMR with magic angle spinning (MAS) has been employed to investigate the cell walls of potatoes and Chinese water chestnuts over a range of hydration levels. Both single-pulse excitation (SPEMAS) and cross-polarization (CPMAS) experiments were carried out. Hydration led to a substantial increase in signal intensities of galactan and galacturonan in the SPEMAS spectra and a decrease in line width, implying mobilization in the backbone and side chains of pectin. In CPMAS spectra of both samples, noncellulose components showed signal loss as hydration increased. However, the signals of some galacturonan in the 3(1) helix configuration remained in the spectra even when the water content was as high as 110%. Cellulose was unaffected. It is concluded that the pectic polysaccharides experience a distribution of molecular conformations and mobility, whereas cellulose remained as typical rigid solid.

  4. MAS-NMR investigations of the crystallization behaviour of lithium aluminum silicate (LAS) glasses containing P 2O 5 and TiO 2 nucleants

    NASA Astrophysics Data System (ADS)

    Ananthanarayanan, A.; Kothiyal, G. P.; Montagne, L.; Revel, B.

    2010-06-01

    Lithium aluminum silicate (LAS) glass of composition (mol%) 20.4Li 2O-4.0Al 2O 3-68.6SiO 2-3.0K 2O-2.6B 2O 3-0.5P 2O 5-0.9TiO 2 was prepared by melt quenching. The glass was then nucleated and crystallized based on differential thermal analysis (DTA) data and was characterized by 29Si, 31P, 11B and 27Al MAS-NMR. XRD and 29Si NMR showed that lithium metasilicate (Li 2SiO 3) is the first phase to c form followed by cristobalite (SiO 2) and lithium disilicate (Li 2Si 2O 5). 29Si MAS-NMR revealed a change in the network structure already for the glasses nucleated at 550 °C. Since crystalline Li 3PO 4, as observed by 31P MAS-NMR, forms concurrently with the silicate phases, we conclude that crystalline Li 3PO 4 does not act as a nucleating agent for lithium silicate phases. Moreover, 31P NMR indicates the formation of M-PO 4 ( M=B, Al or Ti) complexes. The presence of BO 3 and BO 4 structural units in all the glass/glass-ceramic samples is revealed through 11B MAS-NMR. B remains in the residual glass and the crystallization of silicate phases causes a reduction in the number of alkali ions available for charge compensation. As a result, the number of trigonally coordinated B (BO 3) increases at the expense of tetrahedrally coordinated B (BO 4). The 27Al MAS-NMR spectra indicate the presence of tetrahedrally coordinated Al species, which are only slightly perturbed by the crystallization.

  5. Sensitivity Gains, Linearity, and Spectral Reproducibility in Nonuniformly Sampled Multidimensional MAS NMR Spectra of High Dynamic Range.

    SciTech Connect

    Suiter, Christopher L.; Paramasivam, Sivakumar; Hou, Guangjin; Sun, Shangjin; Rice, David M.; Hoch, Jeffrey C.; Rovnyak, David S.; Polenova, Tatyana E.

    2014-04-22

    Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear 13C–13C correlation spectra. We demonstrate on model compounds and on 1–73-(U-13C,15N)/74–108-(U-15N) E. coli thioredoxin reassembly, that with appropriately constructed 50 % NUS schedules inherent sensitivity gains of 1.7–2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear 13C–13C MAS correlation experiments that yield high quality artifact-free datasets.

  6. Effects of T2-relaxation in MAS NMR spectra of the satellite transitions for quadrupolar nuclei: a 27Al MAS and single-crystal NMR study of alum KAl(SO4)2.12H2O.

    PubMed

    Andersen, Morten Daugaard; Jakobsen, Hans J; Skibsted, Jørgen

    2005-04-01

    Asymmetries in the manifold of spinning sidebands (ssbs) from the satellite transitions have been observed in variable-temperature 27Al MAS NMR spectra of alum (KAl(SO4)2.12H2O), recorded in the temperature range from -76 to 92 degrees C. The asymmetries decrease with increasing temperature and reflect the fact that the ssbs exhibit systematically different linewidths for different spectral regions of the manifold. From spin-echo 27Al NMR experiments on a single-crystal of alum, it is demonstrated that these variations in linewidth originate from differences in transverse (T2) relaxation times for the two inner (m=1/2<-->m=3/2 and m=-1/2<-->m=-3/2) and correspondingly for the two outer (m=3/2<-->m=5/2 and m=-3/2<-->m=-5/2) satellite transitions. T2 relaxation times in the range 0.5-3.5 ms are observed for the individual satellite transitions at -50 degrees C and 7.05 T, whereas the corresponding T1 relaxation times, determined from similar saturation-recovery 27Al NMR experiments, are almost constant (T1=0.07-0.10 s) for the individual satellite transitions. The variation in T2 values for the individual 27Al satellite transitions for alum is justified by a simple theoretical approach which considers the cross-correlation of the local fluctuating fields from the quadrupolar coupling and the heteronuclear (27Al-1H) dipolar interaction on the T2 relaxation times for the individual transitions. This approach and the observed differences in T2 values indicate that a single random motional process modulates both the quadrupolar and heteronuclear dipolar interactions for 27Al in alum at low temperatures.

  7. Effects of T2-relaxation in MAS NMR spectra of the satellite transitions for quadrupolar nuclei: a 27Al MAS and single-crystal NMR study of alum KAl(SO 4) 2 · 12H 2O

    NASA Astrophysics Data System (ADS)

    Andersen, Morten Daugaard; Jakobsen, Hans J.; Skibsted, Jørgen

    2005-04-01

    Asymmetries in the manifold of spinning sidebands (ssbs) from the satellite transitions have been observed in variable-temperature 27Al MAS NMR spectra of alum (KAl(SO 4) 2 · 12H 2O), recorded in the temperature range from -76 to 92 °C. The asymmetries decrease with increasing temperature and reflect the fact that the ssbs exhibit systematically different linewidths for different spectral regions of the manifold. From spin-echo 27Al NMR experiments on a single-crystal of alum, it is demonstrated that these variations in linewidth originate from differences in transverse ( T2) relaxation times for the two inner ( m = 1/2 ↔ m = 3/2 and m = -1/2 ↔ m = -3/2) and correspondingly for the two outer ( m = 3/2 ↔ m = 5/2 and m = -3/2 ↔ m = -5/2) satellite transitions. T2 relaxation times in the range 0.5-3.5 ms are observed for the individual satellite transitions at -50 °C and 7.05 T, whereas the corresponding T1 relaxation times, determined from similar saturation-recovery 27Al NMR experiments, are almost constant ( T1 = 0.07-0.10 s) for the individual satellite transitions. The variation in T2 values for the individual 27Al satellite transitions for alum is justified by a simple theoretical approach which considers the cross-correlation of the local fluctuating fields from the quadrupolar coupling and the heteronuclear ( 27Al- 1H) dipolar interaction on the T2 relaxation times for the individual transitions. This approach and the observed differences in T2 values indicate that a single random motional process modulates both the quadrupolar and heteronuclear dipolar interactions for 27Al in alum at low temperatures.

  8. Acetylation of raw cotton for oil spill cleanup application: an FTIR and 13C MAS NMR spectroscopic investigation.

    PubMed

    Adebajo, Moses O; Frost, Ray L

    2004-08-01

    Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy have been used to investigate the acetylation of raw cotton samples with acetic anhydride without solvents in the presence of different amounts of 4-dimethylaminopyridine (DMAP) catalyst. This is a continuation of our previous investigation of acetylation of commercial cotton in an effort to develop hydrophobic, biodegradable, cellulosic sorbent materials for cleaning up oil spills. The FTIR data have again provided a clear evidence for successful acetylation. The NMR results further confirm the successful acetylation. The extent of acetylation was quantitatively determined using the weight percent gain (WPG) due to acetylation and by calculating the ratio R between the intensity of the acetyl C=O stretching band at 1740-1745 cm(-1) and the intensity of C-O stretching vibration of the cellulose backbone at about 1020-1040 cm(-1). The FTIR technique was found to be highly sensitive and reliable for the determination of the extent of acetylation. The level of acetylation of the raw cotton samples was found to be much higher than that of cotton fabrics and the previously studied commercial cotton. The variation of the R and WPG with reaction time, amount of DMAP catalyst and different samples of raw cotton is discussed.

  9. Structural investigations of Pu{sup III} phosphate by X-ray diffraction, MAS-NMR and XANES spectroscopy

    SciTech Connect

    Popa, Karin; Raison, Philippe E.; Martel, Laura; Martin, Philippe M.; Solari, Pier L.; Bouëxière, Daniel; Konings, Rudy J.M.; Somers, Joseph

    2015-10-15

    PuPO{sub 4} was prepared by a solid state reaction method and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. High resolution XANES measurements confirm the +III valence state of plutonium, in agreement with valence bond derivation. The presence of the americium (as β{sup −} decay product of plutonium) in the +III oxidation state was determined based on XANES spectroscopy. High resolution solid state {sup 31}P NMR agrees with the XANES results and the presence of a solid-solution. - Graphical abstract: A full structural analysis of PuPO{sub 4} based on Rietveld analysis of room temperature X-ray diffraction data, XANES and MAS NMR measurements was performed. - Highlights: • The crystal structure of PuPO{sub 4} monazite is solved. • In PuPO{sub 4} plutonium is strictly trivalent. • The presence of a minute amount of Am{sup III} is highlighted. • We propose PuPO{sub 4} as a potential reference material for spectroscopic and microscopic studies.

  10. Acetylation of raw cotton for oil spill cleanup application: an FTIR and 13C MAS NMR spectroscopic investigation

    NASA Astrophysics Data System (ADS)

    Adebajo, Moses O.; Frost, Ray L.

    2004-08-01

    Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy have been used to investigate the acetylation of raw cotton samples with acetic anhydride without solvents in the presence of different amounts of 4-dimethylaminopyridine (DMAP) catalyst. This is a continuation of our previous investigation of acetylation of commercial cotton in an effort to develop hydrophobic, biodegradable, cellulosic sorbent materials for cleaning up oil spills. The FTIR data have again provided a clear evidence for successful acetylation. The NMR results further confirm the successful acetylation. The extent of acetylation was quantitatively determined using the weight percent gain (WPG) due to acetylation and by calculating the ratio R between the intensity of the acetyl CO stretching band at 1740-1745 cm -1 and the intensity of CO stretching vibration of the cellulose backbone at about 1020-1040 cm -1. The FTIR technique was found to be highly sensitive and reliable for the determination of the extent of acetylation. The level of acetylation of the raw cotton samples was found to be much higher than that of cotton fabrics and the previously studied commercial cotton. The variation of the R and WPG with reaction time, amount of DMAP catalyst and different samples of raw cotton is discussed.

  11. The Effect of Antitumor Glycosides on Glioma Cells and Tissues as Studied by Proton HR-MAS NMR Spectroscopy

    PubMed Central

    García-Álvarez, Isabel; Garrido, Leoncio; Romero-Ramírez, Lorenzo; Nieto-Sampedro, Manuel; Fernández-Mayoralas, Alfonso; Campos-Olivas, Ramón

    2013-01-01

    The effect of the treatment with glycolipid derivatives on the metabolic profile of intact glioma cells and tumor tissues, investigated using proton high resolution magic angle spinning (1H HR-MAS) nuclear magnetic resonance (NMR) spectroscopy, is reported here. Two compounds were used, a glycoside and its thioglycoside analogue, both showing anti-proliferative activity on glioma C6 cell cultures; however, only the thioglycoside exhibited antitumor activity in vivo. At the drug concentrations showing anti-proliferative activity in cell culture (20 and 40 µM), significant increases in choline containing metabolites were observed in the 1H NMR spectra of the same intact cells. In vivo experiments in nude mice bearing tumors derived from implanted C6 glioma cells, showed that reduction of tumor volume was associated with significant changes in the metabolic profile of the same intact tumor tissues; and were similar to those observed in cell culture. Specifically, the activity of the compounds is mainly associated with an increase in choline and phosphocholine, in both the cell cultures and tumoral tissues. Taurine, a metabolite that has been considered a biomarker of apoptosis, correlated with the reduction of tumor volume. Thus, the results indicate that the mode of action of the glycoside involves, at least in part, alteration of phospholipid metabolism, resulting in cell death. PMID:24194925

  12. Aluminum coordinations for aluminosilicate glasses at 1 atm. and 3GPa: a 27Al MAS NMR study

    NASA Astrophysics Data System (ADS)

    Allwardt, J. R.; Stebbins, J. F.; Withers, A. C.; Hirschmann, M. M.

    2003-12-01

    In this study, we used 27Al MAS NMR to investigate the distribution of different aluminum coordinations in ambient pressure and moderate pressure (3GPa) aluminosilicate glasses with compositions of Mx+(9-3x)Al2Si6O18, where M= Ca2+, Na+, and K+. These spectra were collected at 18.8 Tesla to minimize the peak broadening due to second-order quadrupolar effects, which causes overlapping peaks for different coordinations of Al. Aluminum is thought to be mostly tetrahedrally coordinated in ambient-pressure aluminosilicate glasses where M+(2-x)O >= Al2O3, but 27Al NMR studies have shown that small concentrations of high-coordinated Al are present in both charge balanced (Toplis et al. 2000; Stebbins et al. 2001) and "depolymerized" (M+(2-x)O > Al2O3) aluminosilicate glasses (Stebbins and Farnan 1992). The 27Al spectra of samples of this study show that these ambient pressure glasses all contain [5]Al. Interestingly, the NAS (Na-aluminosilicate) glass contains more [5]Al than the KAS glass (0.6 vs. 0.3, respectively), which is opposite of that observed for SiO[5] groups in binary silicate glasses (Stebbins and McMillan 1993). The CAS glass spectrum shows a shoulder at 25 ppm, but the [4]Al peak is too broad to assign a reliable percentage for the amount of [5]Al. Previous studies of high-pressure glasses have shown that Al transforms to higher coordinations with increasing pressures (Yarger et al. 1995). In this study, we observe that the 27Al MAS spectrum of the 3 GPa NAS glass shows that 7% [5]Al and 1% [6]Al species exist. Additionally, the spectra of the KAS glass shows that 2% [5]Al and possibly some [6]Al are present at 3 GPa. These spectra clearly show for the first time that pressure induced Al-coordination changes occur in aluminosilicate glasses at pressures of 3 GPa. Recent 27Al NMR spectra of high-pressure "depolymerized" aluminosilicate glasses with different fictive temperatures have shown that the amount of high-coordinated Al increases with increasing

  13. Red coralline algae assessed as marine pH proxies using 11B MAS NMR

    NASA Astrophysics Data System (ADS)

    Cusack, M.; Kamenos, N. A.; Rollion-Bard, C.; Tricot, G.

    2015-02-01

    Reconstructing pH from biogenic carbonates using boron isotopic compositions relies on the assumption that only borate, and no boric acid, is present. Red coralline algae are frequently used in palaeoenvironmental reconstruction due to their widespread distribution and regular banding frequency. Prior to undertaking pH reconstructions using red coralline algae we tested the boron composition of the red coralline alga Lithothamnion glaciale using high field NMR. In bulk analysed samples, thirty percent of boron was present as boric acid. We suggest that prior to reconstructing pH using coralline algae 1) species-specific boron compositions and 2) within-skeleton special distributions of boron are determined for multiple species. This will enable site selective boron analyses to be conducted validating coralline algae as palaeo-pH proxies based on boron isotopic compositions.

  14. Use of SPAM and FAM pulses in high-resolution MAS NMR spectroscopy of quadrupolar nuclei.

    PubMed

    Ball, Thomas J; Wimperis, Stephen

    2007-08-01

    The merits of SPAM and FAM pulses for enhancing the conversion of triple- to single-quantum coherences in the two-dimensional MQMAS experiment are compared using (87)Rb (spin I=3/2) and (27)Al (I=5/2) NMR of crystalline and amorphous materials. Although SPAM pulses are more easily optimized, our experiments and simulations suggest that FAM pulses yield greater signal intensity in all cases. In conclusion, we argue that, as originally suggested, SPAM and FAM pulses are best implemented in phase-modulated whole-echo MQMAS experiments and that the use of SPAM pulses to record separate echo and antiecho data sets, which are then combined, generally yields lower signal-to-noise ratios.

  15. Use of SPAM and FAM pulses in high-resolution MAS NMR spectroscopy of quadrupolar nuclei

    NASA Astrophysics Data System (ADS)

    Ball, Thomas J.; Wimperis, Stephen

    2007-08-01

    The merits of SPAM and FAM pulses for enhancing the conversion of triple- to single-quantum coherences in the two-dimensional MQMAS experiment are compared using 87Rb (spin I = 3/2) and 27Al ( I = 5/2) NMR of crystalline and amorphous materials. Although SPAM pulses are more easily optimized, our experiments and simulations suggest that FAM pulses yield greater signal intensity in all cases. In conclusion, we argue that, as originally suggested, SPAM and FAM pulses are best implemented in phase-modulated whole-echo MQMAS experiments and that the use of SPAM pulses to record separate echo and antiecho data sets, which are then combined, generally yields lower signal-to-noise ratios.

  16. Red coralline algae assessed as marine pH proxies using 11B MAS NMR.

    PubMed

    Cusack, M; Kamenos, N A; Rollion-Bard, C; Tricot, G

    2015-02-02

    Reconstructing pH from biogenic carbonates using boron isotopic compositions relies on the assumption that only borate, and no boric acid, is present. Red coralline algae are frequently used in palaeoenvironmental reconstruction due to their widespread distribution and regular banding frequency. Prior to undertaking pH reconstructions using red coralline algae we tested the boron composition of the red coralline alga Lithothamnion glaciale using high field NMR. In bulk analysed samples, thirty percent of boron was present as boric acid. We suggest that prior to reconstructing pH using coralline algae 1) species-specific boron compositions and 2) within-skeleton special distributions of boron are determined for multiple species. This will enable site selective boron analyses to be conducted validating coralline algae as palaeo-pH proxies based on boron isotopic compositions.

  17. Heteronuclear decoupling in MAS NMR in the intermediate to fast sample spinning regime

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Bjerring, Morten; Sharma, Kshama; Madhu, P. K.; Nielsen, Niels Chr.

    2016-01-01

    Heteronuclear spin decoupling in solid-state magic-angle spinning NMR is investigated to present methods overcoming interferences between rf irradiation and sample spinning in the intermediate to fast spinning regime. We demonstrate that a recent phase-alternated variant of refocused CW irradiation (rCWApA) provides efficient and robust decoupling in this regime. An extensive experimental and numerical comparison is presented for rCWApA and PISSARRO (phase-inverted supercycled sequence for attenuation of rotary resonance), previously introduced to quench rotary-resonance recoupling effects, under conditions with spinning frequencies between 30 and 60 kHz. Simulations are used to identify the effect of decoupling for various nuclear spin interactions.

  18. 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.

  19. Non-destructive and direct determination of the degree of substitution of carboxymethyl cellulose by HR-MAS (13)C NMR spectroscopy.

    PubMed

    Ferro, M; Castiglione, F; Panzeri, W; Dispenza, R; Santini, L; Karlsson, H J; de Wit, P P; Mele, A

    2017-08-01

    We report on the direct assessment of the degree of substitution (DS) of carboxymethyl cellulose (CMC) by High Resolution Magic Angle Spinning (HR-MAS) (13)C NMR spectroscopy. The method is applied to industrial CMCs with low and high viscosity and nominal DS, purified and technical samples, and from cellulose linters or wood. The preparation of a set of purified CMC working standards with accurate DS values for the method validation is also described. The DS values determined via HR-MAS (13)C NMR on the industrial samples are critically compared to the corresponding values achieved through the USP 37 〈281〉 method (ASH method) and the HPLC method, and the advantages and limitations of the HR-MAS NMR method highlighted. Finally, the HR-MAS NMR approach allowed the accurate DS assessment in CMC with low DS, characterized by a non-negligible fraction of non-functionalized cellulose. The proposed "effective DS" accounts for the DS of the solvent-exposed CMC. Copyright © 2017. Published by Elsevier Ltd.

  20. Enhanced sensitivity in high-resolution 1H solid-state NMR spectroscopy with DUMBO dipolar decoupling under ultra-fast MAS

    NASA Astrophysics Data System (ADS)

    Salager, Elodie; Stein, Robin S.; Steuernagel, Stefan; Lesage, Anne; Elena, Bénédicte; Emsley, Lyndon

    2009-02-01

    The solid-state NMR 1H homonuclear decoupling sequences in the DUMBO family are shown to be effective at ultra-fast MAS rates of up to 65 kHz. The sequences are applied to model compounds glycine and [2- 13C]- L-alanine as well as the dipeptide β- L-Asp- L-Ala in windowed and continuous phase-modulated versions. They are shown to achieve especially impressive resolution when implemented in a 2D constant-time experiment. At 65 kHz MAS, 1H resolution using homonuclear decoupling is similar to that obtained at lower MAS rates, but peak intensity, and therefore spectral sensitivity, is improved by a factor of 5 over homonuclear-decoupled spectra at 10 kHz MAS.

  1. Probing sol-gel matrices microenvironments by PGSE HR-MAS NMR.

    PubMed

    Ferreira, Ana S D; Barreiros, Susana; Cabrita, Eurico J

    2017-05-01

    We applied Pulsed Gradient Spin Echo diffusion with high-resolution magic angle spinning NMR to study sol-gel matrices used to encapsulate enzymes for biocatalysis (TMOS/MTMS and TMOS/BTMS) to gain insight into the local chemical microenvironment. Transport properties of solvents with different polarities (1-pentanol, acetonitrile and n-hexane) were studied through their apparent self-diffusion coefficients. The spin echo attenuation of the solvents shows two distinct diffusion domains, one with fast diffusion (Dfast ) associated with interparticle diffusion and another with slow diffusion (Dslow ) corresponding to the displacement inside the pores within the sol-gel particles. The analysis of the root mean square displacements at different diffusion times showed that the Dfast domain has a free diffusion regime in both matrices (the root mean square displacement is linearly dependent of the diffusion time), while the Dslow domain shows a different regime that depends on the matrix. We investigated the exchange regime between the two diffusion sites. In both matrices, n-hexane was in intermediate exchange between diffusion domains, while the polar solvents were in slow exchange in TMOS/BTMS and in intermediate exchange in TMOS/MTMS. Data were fitted for TMOS/BTMS with the Kärger model, and the physical parameters were obtained. The results add to the evidence that the pores are a hydrophobic environment but that the presence of some free hydrophilic groups inside the pore, as observed in the TMOS/BTMS, has a key role in slowing down the exchange of polar solvents and that this is relevant to explain previously reported enzyme activity in these materials. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  2. Assessing the Detection Limit of a Minority Solid-State Form of a Pharmaceutical by (1)H Double-Quantum Magic-Angle Spinning Nuclear Magnetic Resonance Spectroscopy.

    PubMed

    Maruyoshi, Keisuke; Iuga, Dinu; Watts, Abigail E; Hughes, Colan E; Harris, Kenneth D M; Brown, Steven P

    2017-07-25

    The lower detection limit for 2 distinct crystalline phases by (1)H magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) is investigated for a minority amount of cimetidine (anhydrous polymorph A) in a physical mixture with the anhydrous HCl salt of cimetidine. Specifically, 2-dimensional (1)H double-quantum (DQ) MAS NMR spectra of polymorph A and the anhydrous HCl salt constitute fingerprints for the presence of each of these solid forms. For solid-state NMR data recorded at a (1)H Larmor frequency of 850 MHz and a MAS frequency of 30 kHz on ∼10 mg of sample, it is shown that, by following the pair of cross-peaks at a (1)H DQ frequency of 7.4 + 11.6 = 19.0 ppm that are unique to polymorph A, the level of detection for polymorph A in a physical mixture with the anhydrous HCl salt is a concentration of 1% w/w. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  3. Signal intensities in ¹H-¹³C CP and INEPT MAS NMR of liquid crystals.

    PubMed

    Nowacka, A; Bongartz, N A; Ollila, O H S; Nylander, T; Topgaard, D

    2013-05-01

    Spectral editing with CP and INEPT in (13)C MAS NMR enables identification of rigid and mobile molecular segments in concentrated assemblies of surfactants, lipids, and/or proteins. In order to get stricter definitions of the terms "rigid" and "mobile", as well as resolving some ambiguities in the interpretation of CP and INEPT data, we have developed a theoretical model for calculating the CP and INEPT intensities as a function of rotational correlation time τc and C-H bond order parameter SCH, taking the effects of MAS into account. According to the model, the range of τc can at typical experimental settings (5kHz MAS, 1ms ramped CP at 80-100kHz B1 fields) be divided into four regimes: fast (τc<1ns), fast-intermediate (τc≈0.1μs), intermediate (τc≈1μs), and slow (τc>0.1ms). In the fast regime, the CP and INEPT intensities are independent of τc, but strongly dependent on |SCH|, with a cross-over from dominating INEPT to dominating CP at |SCH|>0.1. In the intermediate regime, neither CP nor INEPT yield signal on account of fast T1ρ and T2 relaxation. In both the fast-intermediate and slow regimes, there is exclusively CP signal. The theoretical predictions are tested by experiments on the glass-forming surfactant n-octyl-β-d-maltoside, for which τc can be varied continuously in the nano- to millisecond range by changing the temperature and the hydration level. The atomistic details of the surfactant dynamics are investigated with MD simulations. Based on the theoretical model, we propose a procedure for calculating CP and INEPT intensities directly from MD simulation trajectories. While MD shows that there is a continuous gradient of τc from the surfactant polar headgroup towards the methyl group at the end of the hydrocarbon chain, analysis of the experimental CP and INEPT data indicates that this gradient gets steeper with decreasing temperature and hydration level, eventually spanning four orders of magnitude at completely dry conditions

  4. Solid-state 19F MAS NMR study on the conformation and molecular mobility of poly(chlorotrifluoroethylene).

    PubMed

    Tatsuno, Hiroto; Aimi, Keitaro; Ando, Shinji

    2007-05-01

    The temperature dependence of molecular mobility and conformational changes of poly(chlorotrifluoro- ethylene) (PCTFE) have been investigated by solid-state (19)F magic angle spinning (MAS) NMR spectroscopy. The pulse techniques of dipolar-filter and T(1rho)-filter allow selective observation of the amorphous and crystalline domains, respectively. The temperature dependence of T(1rho) (F) revealed that the segmental motion in the amorphous domain becomes vigorous above ca 80 degrees C, which is well above the glass transition (T(g)) temperature (52 degrees C) and more close to the beta-relaxation temperature (95 degrees C). On the other hand, vigorous molecular motions in the crystalline domain occur above 120 degrees C, which is much below the melting temperature (212 degrees C). This indicates that the polymer chains in the PCTFE crystallites are more mobile than those of typical semicrystalline fluoropolymers like poly(vinylidene fluoride) (PVDF), which can be associated with structural imperfections in the crystallites. In addition, the density functional theory (DFT) calculations of (19)F magnetic shielding suggest that the high-frequency shifts observed for the crystalline signals above 80 degrees C can be ascribed to the conformational change around meso diads toward more twisted and/or helical conformations in the main chain.

  5. Anisotropic indirect nuclear spin-spin coupling in InP: 31P CP NMR study under slow MAS condition

    NASA Astrophysics Data System (ADS)

    Iijima, Takahiro; Hashi, Kenjiro; Goto, Atsushi; Shimizu, Tadashi; Ohki, Shinobu

    2006-02-01

    The indirect nuclear spin-spin interaction tensor between neighboring 113,115In- 31P spins in Fe-doped InP semiconductor has been studied by 31P NMR spectra measured using CP of 113In → 31P and 115In → 31P under slow MAS condition. The isotropic ( Jiso) and anisotropic ( Janiso = 2/3[ J∥ - J⊥]) parts of the indirect interaction tensor are obtained from the spectral simulation. The acceptable combinations of these values are found to be as follows: ( Jiso, Janiso) = (224 ± 5, 500 ± 100 Hz) or (-224 ± 5, 2100 ± 100 Hz). Although, the coupling constants estimated in this study are slightly different from previously reported values of ∣ Jiso∣ = 350 Hz, Janiso = 1298 Hz [M. Engelsberg, R.E. Norberg, Phys. Rev. B 5 (1972) 3395] and of ∣ Jiso∣ = 225 ± 10, Janiso = (813 ± 50) or (1733 ± 50) Hz [M. Tomaselli et al., Phys. Rev. B 58 (1998) 8627], all of these has the trend that Janiso is rather larger than Jiso.

  6. Hydration properties and phosphorous speciation in native, gelatinized and enzymatically modified potato starch analyzed by solid-state MAS NMR.

    PubMed

    Larsen, Flemming H; Kasprzak, Mirosław M; Lærke, Helle N; Knudsen, Knud Erik B; Pedersen, Sven; Jørgensen, Anne S; Blennow, Andreas

    2013-09-12

    Hydration of granular, gelatinized and molecularly modified states of potato starch in terms of molecular mobility were analyzed by (13)C and (31)P solid-state MAS NMR. Gelatinization (GEL) tremendously reduced the immobile fraction compared to native (NA) starch granules. This effect was enhanced by enzyme-assisted catalytic branching with branching enzyme (BE) or combined BE and β-amylase (BB) catalyzed exo-hydrolysis. Carbons of the glycosidic α-1,6 linkages required high hydration rates before adopting uniform chemical shifts indicating solid-state disorder and poor water accessibility. Comparative analysis of wheat and waxy maize starches demonstrated that starches were similar upon gelatinization independent of botanical origin and that the torsion angles of the glycosidic linkages were averages of the crystalline A and B type structures. In starch suspension phosphorous in immobile regions was only observed in NA starch. Moreover phosphorous was observed in a minor pH-insensitive form and as major phosphate in hydrated GEL and BE starches.

  7. LC/ESI-MS n and 1H HR-MAS NMR analytical methods as useful taxonomical tools within the genus Cystoseira C. Agardh (Fucales; Phaeophyceae).

    PubMed

    Jégou, Camille; Culioli, Gérald; Kervarec, Nelly; Simon, Gaëlle; Stiger-Pouvreau, Valérie

    2010-12-15

    Species of the genus Cystoseira are particularly hard to discriminate, due to the complexity of their morphology, which can be influenced by their phenological state and ecological parameters. Our study emphasized on the relevance of two kinds of analytical tools, (1) LC/ESI-MS(n) and (2) (1)H HR-MAS NMR, also called in vivo NMR, to identify Cystoseira specimens at the specific level and discuss their taxonomy. For these analyses, samples were collected at several locations in Brittany (France), where Cystoseira baccata, C. foeniculacea, C. humilis, C. nodicaulis and C. tamariscifolia were previously reported. To validate our chemical procedure, the sequence of the ITS2 has been obtained for each species to investigate their phylogenetic relationships at a molecular level. Our study highlighted the consistency of the two physico-chemical methods, compared to "classical" molecular approach, in studying taxonomy within the genus Cystoseira. Especially, LC/ESI-MS(n) and phylogenetic analyses converged into the discrimination of two taxonomical groups among the 5 species. The occurrence of some specific signals in the (1)H HR-MAS NMR spectra and/or some characteristic chemical compounds during LC/ESI-MS(n) analysis could be regarded as discriminating factors. LC/ESI-MS(n) and (1)H HR-MAS NMR turned out to be two relevant and innovative techniques to discriminate taxonomically this complex genus.

  8. Line shapes and widths of MAS sidebands for 27Al satellite transitions. multinuclear MAS NMR of tugtupite Na8Al2Be2Si8O24Cl2.

    PubMed

    Skibsted, J; Norby, P; Bildsøe, H; Jakobsen, H J

    1995-12-01

    A multinuclear 9Be, 23Na, 27Al, and 29Si magic-angle spinning (MAS) NMR study has been performed for the mineral tugtupite (Na8Al2Be2Si8O24Cl2). The extremely well-resolved spectra allow observation of separate spinning sidebands (ssb's) from the inner (+/- 1/2, +/- 3/2) and outer (+/- 3/2, +/- 5/2) 27Al satellite transitions, and are utilized in a detailed analysis of the line shapes and widths of the individual ssb's from simulations. The line widths of the ssb's from the inner and outer 27Al satellite transitions are found to decrease systematically with increasing order of the ssb's across the spectrum. Accurate values for the 9Be, 23Na, and 27Al quadrupole coupling parameters and isotropic chemical shifts are obtained from simulations of the manifolds of ssb's from the satellite transitions. MAS NMR of the 9Be satellite transitions for tugtupite, BeO, and beryl(Al2Be3Si6O18) shows that these transitions are particularly useful for determination of 9Be quadrupole couplings because of the small 9Be quadrupole moment. The 29Si shielding anisotropy of delta sigma = 48 ppm in tugtupite is the largest determined so far for a framework SiO4 tetrahedron. Finally, the crystal structure of the tugtupite sample has been refined by single-crystal X-ray diffraction, and correlations between the multinuclear NMR parameters and structural data are reported.

  9. Identification of Li-Ion Battery SEI Compounds through (7)Li and (13)C Solid-State MAS NMR Spectroscopy and MALDI-TOF Mass Spectrometry.

    PubMed

    Huff, Laura A; Tavassol, Hadi; Esbenshade, Jennifer L; Xing, Wenting; Chiang, Yet-Ming; Gewirth, Andrew A

    2016-01-13

    Solid-state (7)Li and (13)C MAS NMR spectra of cycled graphitic Li-ion anodes demonstrate SEI compound formation upon lithiation that is followed by changes in the SEI upon delithiation. Solid-state (13)C DPMAS NMR shows changes in peaks associated with organic solvent compounds (ethylene carbonate and dimethyl carbonate, EC/DMC) upon electrochemical cycling due to the formation of and subsequent changes in the SEI compounds. Solid-state (13)C NMR spin-lattice (T1) relaxation time measurements of lithiated Li-ion anodes and reference poly(ethylene oxide) (PEO) powders, along with MALDI-TOF mass spectrometry results, indicate that large-molecular-weight polymers are formed in the SEI layers of the discharged anodes. MALDI-TOF MS and NMR spectroscopy results additionally indicate that delithiated anodes exhibit a larger number of SEI products than is found in lithiated anodes.

  10. Magnesium silicate dissolution investigated by S1-29 MAS, H-1 Si-29 CPMAS, Mg-25 QCPMG, and H-1 Mg-25 CP QCPMG NMR

    SciTech Connect

    Davis, M C; Brouwer, Piet W; Wesolowski, David J; Anovitz, Lawrence {Larry} M

    2009-07-01

    Olivine-(Mg,Fe){sub 2}SiO{sub 4}-has been the subject of frequent investigation in the earth sciences because of its simple structure and rapid dissolution kinetics. Several studies have observed a preferential release of the divalent cation with respect to silicon during weathering under acidic conditions, which has been correlated to the formation of a silicon-rich leached layer. While leached layer formation has been inferred through the changing solution chemistry, a thorough spectroscopic investigation of olivine reacted under acidic conditions has not been conducted. The pure magnesium end member of the olivine series (forsterite-Mg2SiO4) was chosen for detailed investigations in this study because paramagnetic iron hinders NMR investigations by providing an extra mode of relaxation for neighboring nuclei, causing lineshapes to become significantly broadened and unobservable in the NMR spectrum. For reacting forsterite, spectroscopic interrogations using nuclear magnetic resonance (NMR) can elucidate the changing magnesium coordination and bonding environment. In this study, we combine analysis of the changing solution chemistry with advanced NMR techniques ({sup 29}Si MAS, {sup 1}H-{sup 29}Si CP MAS, {sup 25}Mg QCPMG, and {sup 1}H-{sup 25}Mg CP QCPMG NMR) to probe leached layer formation and secondary phase precipitation during the dissolution of forsterite at 150 C.

  11. The metabolic profile of lemon juice by proton HR-MAS NMR: the case of the PGI Interdonato Lemon of Messina.

    PubMed

    Cicero, Nicola; Corsaro, Carmelo; Salvo, Andrea; Vasi, Sebastiano; Giofré, Salvatore V; Ferrantelli, Vincenzo; Di Stefano, Vita; Mallamace, Domenico; Dugo, Giacomo

    2015-01-01

    We have studied by means of High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HR-MAS NMR) the metabolic profile of the famous Sicilian lemon known as 'Interdonato Lemon of Messina PGI'. The PGI Interdonato Lemon of Messina possesses high organoleptic and healthy properties and is recognised as one of the most nutrient fruits. In particular, some of its constituents are actively studied for their chemo-preventive and therapeutic properties. In this paper, we have determined by means of HR-MAS NMR spectroscopy the molar concentration of the main metabolites constituent the juice of PGI Interdonato Lemon of Messina in comparison with that of the not-PGI Interdonato Lemon of Turkey. Our aim is to develop an analytical technique, in order to determine a metabolic fingerprint able to reveal commercial frauds in national and international markets.

  12. Hysteresis effect of ammonium and water protons by 1H MAS NMR in (NH4)2CuBr4·2H2O

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Cho, Jiung

    2017-10-01

    The chemical shifts, linewidths, and spin-lattice relaxation times for ammonium and water protons in (NH4)2CuBr4·2H2O were investigated by 1H magic angle spinning nuclear magnetic resonance (MAS NMR) with a focus on the roles of NH4+ and H2O at high temperatures. The changes in the temperature dependence of the data near Td (=360 K) were related to variations of the H environments; the mechanism above Td was related to hydrogen-bond transfer involving breakage of the weak part of the hydrogen bond. The hysteresis effects for the ammonium and water protons in (NH4)2CuBr4·2H2O by MAS NMR were described with respect to heating and cooling.

  13. Nanoscopic yttrium oxide fluorides: non-aqueous fluorolytic sol-gel synthesis and structural insights by 19F and 89Y MAS NMR.

    PubMed

    Scholz, G; Dreger, M; Bertram, R; Kemnitz, E

    2015-08-14

    Nanoscopic yttrium acetate fluorides Y(CH(3)COO)(3-z)F(z) and yttrium oxide fluorides YO(3-z)/(2)F(z )were prepared with tunable Y/F molar ratios via the fluorolytic sol-gel route. All samples were characterized by X-ray diffraction, elemental analysis and thermal analysis. In addition, local structures of all samples were studied by (19)F MAS, (19)F-(89)Y CP MAS and (1)H-(89)Y CP MAS NMR spectroscopy and the respective chemical shifts are given. For both classes of compounds, only the fluorination using one equivalent of F (z = 1) leads to defined, well crystalline matrices: yttrium acetate fluoride Y(CH(3)COO)(2)F and r-YOF.

  14. Optimum levels of exchangeable protons in perdeuterated proteins for proton detection in MAS solid-state NMR spectroscopy.

    PubMed

    Akbey, Umit; Lange, Sascha; Trent Franks, W; Linser, Rasmus; Rehbein, Kristina; Diehl, Anne; van Rossum, Barth-Jan; Reif, Bernd; Oschkinat, Hartmut

    2010-01-01

    We present a systematic study of the effect of the level of exchangeable protons on the observed amide proton linewidth obtained in perdeuterated proteins. Decreasing the amount of D(2)O employed in the crystallization buffer from 90 to 0%, we observe a fourfold increase in linewidth for both (1)H and (15)N resonances. At the same time, we find a gradual increase in the signal-to-noise ratio (SNR) for (1)H-(15)N correlations in dipolar coupling based experiments for H(2)O concentrations of up to 40%. Beyond 40%, a significant reduction in SNR is observed. Scalar-coupling based (1)H-(15)N correlation experiments yield a nearly constant SNR for samples prepared with < or =30% H(2)O. Samples in which more H(2)O is employed for crystallization show a significantly reduced NMR intensity. Calculation of the SNR by taking into account the reduction in (1)H T (1) in samples containing more protons (SNR per unit time), yields a maximum SNR for samples crystallized using 30 and 40% H(2)O for scalar and dipolar coupling based experiments, respectively. A sensitivity gain of 3.8 is obtained by increasing the H(2)O concentration from 10 to 40% in the CP based experiment, whereas the linewidth only becomes 1.5 times broader. In general, we find that CP is more favorable compared to INEPT based transfer when the number of possible (1)H,(1)H interactions increases. At low levels of deuteration (> or =60% H(2)O in the crystallization buffer), resonances from rigid residues are broadened beyond detection. All experiments are carried out at MAS frequency of 24 kHz employing perdeuterated samples of the chicken alpha-spectrin SH3 domain.

  15. Fine-tuned characterization at the solid/solution interface of organotin compounds grafted onto cross-linked polystyrene by using high-resolution MAS NMR spectroscopy.

    PubMed

    Martins, José C; Mercier, Frédéric A G; Vandervelden, Alexander; Biesemans, Monique; Wieruszeski, Jean-Michel; Humpfer, Eberhard; Willem, Rudolph; Lippens, Guy

    2002-08-02

    The structural characterization of organotin compounds that are grafted onto insoluble cross-linked polymers has necessarily been limited to elemental analysis, infrared spectroscopy, and in a few instances, solid-state NMR spectroscopy. This important bottleneck in the development of such grafted systems has been addressed by using high-resolution magic angle spinning (hr-MAS) NMR spectroscopy. The great potential of this technique is demonstrated through the structural characterization of diphenylbutyl-(3,4) and dichlorobutylstannanes (5,6), grafted onto divinylbenzene cross-linked polystyrene by means of a suitable linker (1, 2). First, conditions suitable for the application of hr-MAS NMR spectroscopy were identified by characterizing the (1)H resonance line widths of the grafted organotin moiety following swelling of the functionalized beads in eight representative solvents. The presence of clearly identifiable tin coupling patterns in both the 1D (13)C and 2D (1)H-(13)C HSQC spectra, and the incorporation of (119)Sn chemical shift and connectivity information from hr-MAS 1D (119)Sn and 2D (1)H-(119)Sn HMQC spectra, provide an unprecedented level of characterization of grafted organotins directly at the solid/liquid interface. In addition, the use of hr-MAS (119)Sn NMR for reaction monitoring, impurity detection, and quantification and assessment of the extent of coordination reveals its promise as a novel tool for the investigation of polymer-grafted organotin compounds. The approach described here should be sufficiently general for extension to a variety of other nuclei of interest in polymer-supported organometallic chemistry.

  16. Investigation of cation environment and framework changes in silicotitanate exchange materials using solid-state 23Na, 29Si, and 133Cs MAS NMR

    NASA Astrophysics Data System (ADS)

    Cherry, Brian R.; Nyman, May; Alam, Todd M.

    2004-06-01

    Crystalline silicotitanate (CST), HNa 3Ti 4Si 2O 14·4H 2O and the Nb-substituted CST (Nb-CST), HNa 2Ti 3NbSi 2O 14·4H 2O, are highly selective Cs + sorbents, which makes them attractive materials for the selective removal of radioactive species from nuclear waste solutions. The structural basis for the improved Cs + selectivity in the niobium analogs was investigated through a series of solid-state magic angle spinning (MAS) NMR experiments. Changes in the local environment of the Na + and Cs + cations in both CST and Nb-CST materials as a function of weight percent cesium exchange were investigated using 23Na and 133Cs MAS NMR. Framework changes induced by Cs + loading and hydration state were investigated with 29Si MAS NMR. Multiple Cs + environments were observed in the CST and Nb-CST material. The relative population of these different Cs + environments varies with the extent of Cs + loading. Marked changes in the framework Si environment were noted with the initial incorporation of Cs +, however with increased Cs + loading the impact to the Si environment becomes less pronounced. The Cs + environment and Si framework structure were influenced by the Nb-substitution and were greatly affected by the amount of water present in the materials. The increased Cs + selectivity of the Nb-CST materials arises from both the chemistry and geometry of the tunnels and pores.

  17. 1H HR/MAS NMR in the suspended state: molecular recognition processes in liquid chromatography between steroids and a silica hydride-based cholesterol phase.

    PubMed

    Friebolin, Volker; Bayer, Marc P; Matyska, Maria T; Pesek, Joseph J; Albert, Klaus

    2009-05-01

    A mixture of eight steroids was separated by HPLC on a silica hydride-based stationary phase modified with a moiety of cholesteryl 10-undecanoate. Within the steroid mixture progesterone showed the longest retention time suggesting the strongest interaction with the stationary phase material. To obtain more detailed information upon the effective separation process, interaction studies were performed by high resolution/magic angle spinning (HR/MAS) NMR spectroscopy recorded in the suspended state. (1)H saturation transfer difference (STD) NMR experiments with T(1rho) suppression showed significant hydrophobic binding affinities of progesterone toward the cholesterol column material. These NMR results can be correlated directly to the chromatographic data obtained by HPLC.

  18. A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi-optical microwave transmission.

    PubMed

    Pike, Kevin J; Kemp, Thomas F; Takahashi, Hiroki; Day, Robert; Howes, Andrew P; Kryukov, Eugeny V; MacDonald, James F; Collis, Alana E C; Bolton, David R; Wylde, Richard J; Orwick, Marcella; Kosuga, Kosuke; Clark, Andrew J; Idehara, Toshitaka; Watts, Anthony; Smith, Graham M; Newton, Mark E; Dupree, Ray; Smith, Mark E

    2012-02-01

    A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer operating at 6.7 T is described and demonstrated. The 187 GHz TE(13) fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz (1)H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE(16) second-harmonic mode of the gyrotron) for DNP at 14.1T (600 MHz (1)H NMR). The pulsed microwave output from the gyrotron is converted to a quasi-optical Gaussian beam using a Vlasov antenna and transmitted to the NMR probe via an optical bench, with beam splitters for monitoring and adjusting the microwave power, a ferrite rotator to isolate the gyrotron from the reflected power and a Martin-Puplett interferometer for adjusting the polarisation. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample along the MAS rotation axis. The beam is focussed to a ~1 mm waist at the top of the rotor and then gradually diverges to give much more efficient coupling throughout the sample than designs using direct waveguide irradiation. The probe can be used in triple channel HXY mode for 600 MHz (1)H and double channel HX mode for 284 MHz (1)H, with MAS sample temperatures ≥85 K. Initial data at 6.7 T and ~1 W pulsed microwave power are presented with (13)C enhancements of 60 for a frozen urea solution ((1)H-(13)C CP), 16 for bacteriorhodopsin in purple membrane ((1)H-(13)C CP) and 22 for (15)N in a frozen glycine solution ((1)H-(15)N CP) being obtained. In comparison with designs which irradiate perpendicular to the rotation axis the approach used here provides a highly efficient use of the incident microwave beam and an NMR-optimised coil design. Copyright © 2011 Elsevier Inc. All rights reserved.

  19. A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi-optical microwave transmission

    NASA Astrophysics Data System (ADS)

    Pike, Kevin J.; Kemp, Thomas F.; Takahashi, Hiroki; Day, Robert; Howes, Andrew P.; Kryukov, Eugeny V.; MacDonald, James F.; Collis, Alana E. C.; Bolton, David R.; Wylde, Richard J.; Orwick, Marcella; Kosuga, Kosuke; Clark, Andrew J.; Idehara, Toshitaka; Watts, Anthony; Smith, Graham M.; Newton, Mark E.; Dupree, Ray; Smith, Mark E.

    2012-02-01

    A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer operating at 6.7 T is described and demonstrated. The 187 GHz TE13 fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz 1H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE16 second-harmonic mode of the gyrotron) for DNP at 14.1 T (600 MHz 1H NMR). The pulsed microwave output from the gyrotron is converted to a quasi-optical Gaussian beam using a Vlasov antenna and transmitted to the NMR probe via an optical bench, with beam splitters for monitoring and adjusting the microwave power, a ferrite rotator to isolate the gyrotron from the reflected power and a Martin-Puplett interferometer for adjusting the polarisation. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample along the MAS rotation axis. The beam is focussed to a ˜1 mm waist at the top of the rotor and then gradually diverges to give much more efficient coupling throughout the sample than designs using direct waveguide irradiation. The probe can be used in triple channel HXY mode for 600 MHz 1H and double channel HX mode for 284 MHz 1H, with MAS sample temperatures ⩾85 K. Initial data at 6.7 T and ˜1 W pulsed microwave power are presented with 13C enhancements of 60 for a frozen urea solution (1H-13C CP), 16 for bacteriorhodopsin in purple membrane (1H-13C CP) and 22 for 15N in a frozen glycine solution (1H-15N CP) being obtained. In comparison with designs which irradiate perpendicular to the rotation axis the approach used here provides a highly efficient use of the incident microwave beam and an NMR-optimised coil design.

  20. High field 27Al MAS NMR and TPD studies of active sites in ethanol dehydration using thermally treated transitional aluminas as catalysts

    SciTech Connect

    Hu, Jian Zhi; Xu, Suochang; Kwak, Ja Hun; Hu, Mary Y.; Wan, Chuan; Zhao, Zhenchao; Szanyi, Janos; Bao, Xinhe; Han, Xiuwen; Wang, Yong; Peden, Charles H. F.

    2016-04-01

    Gamma-, sigma- and theta-Al2O3 are well known metastable “transitional” alumina structural polymorphs. Upon heating, Al2O3 transitions to the so-called and Al2O3 polymorphs and finally forms the thermally stable Al2O3. The poorly developed crystallinity and co-existence of the , , and Al2O3 prior to forming all Al2O3, making it difficult to characterize the structures as well as to quantify the various phases of the transition alumina. As a result, there are significant controversies in the literatures. In this work, a detailed NMR analysis was carried out at high magnetic field on three special aluminum oxide samples where the, , , Al2O3 phases are made dominant, respectively, by controlling the synthesis conditions. The goal is to simplify, including making unambiguous, spectral assignments in 27Al MAS NMR spectra of transition alumina that have not yet been commonly agreed previously. Specifically, quantitative 1D 27Al MAS NMR was used to quantify the ratios of the different alumina structural units, 2D MQMAS 27Al MAS was used for obtaining the highest spectral resolution to guide the analysis of the 1D spectrum, and a saturation pulse sequence was integrated into the 1D NMR to select the amorphous structures, including obtain spectra where the penta-coordinate sites are observed with enhanced relative intensity. Collectively, this study uniquely assigns Al-peaks (both octahedral and tetrahedral) to the Al2O3 and the Al2O3 phases and offers a new way of understanding, including quantifying, the different structural units and sites in transition alumina samples.

  1. Metabolic changes in rat lens after in vivo exposure to ultraviolet irradiation: measurements by high resolution MAS 1H NMR spectroscopy.

    PubMed

    Risa, Øystein; Saether, Oddbjørn; Löfgren, Stefan; Söderberg, Per G; Krane, Jostein; Midelfart, Anna

    2004-06-01

    In the present study, high-resolution magic angle spinning proton nuclear magnetic resonance (HR-MAS (1)H NMR) spectroscopy was used to investigate changes in the metabolic profile of intact rat lenses after UVB irradiation of the eyes. Three groups of Sprague-Dawley rats were exposed to UVB radiation at 2.5, 5.0, and 7.5 kJ/m(2). One eye was exposed, and the contralateral eye served as the control. One week after exposure, the lenses were removed and forward light-scattering was quantified. Thereafter, proton NMR spectra from the intact lenses were obtained. Relative changes in metabolite concentrations were determined. The lenses in all three groups showed significant increases in light-scattering after UVB irradiation. The high-quality HR-MAS (1)H NMR spectra permitted more than 30 different metabolites to be identified. UVB irradiation caused a significant decrease (P < 0.05) in concentrations of taurine, hypotaurine, tyrosine, phenylalanine, valine, myo-inositol, phosphocholine, betaine, succinate, and glutathione at all three UV doses. For glycine, glutamate, and lactate, significant decreases in concentration were observed at the two lowest UVR-B doses. The total amount of adenosine tri- and diphosphate and (ATP, ADP) decreased significantly and that of adenosine monophosphate AMP increased significantly at the two highest doses. Alanine was the only amino acid that increased after UVB irradiation. None of these metabolites exhibited a significant UVB dose-dependent relationship. This study demonstrates for the first time the potential of HR-MAS (1)H NMR spectroscopy as an analytical tool for use on intact lenses. Near-threshold UVR-B doses led to a generally significant decrease in water-soluble metabolites 1 week after exposure. The lack of dose-dependent changes in the metabolites indicates that repair processes during the first week after UVB irradiation overcome the immediate metabolic disturbances.

  2. Characterization of a chiral stationary phase by HR/MAS NMR spectroscopy and investigation of enantioselective interaction with chiral ligates by transferred NOE.

    PubMed

    Hellriegel, Christine; Skogsberg, Urban; Albert, Klaus; Lämmerhofer, Michael; Maier, Norbert M; Lindner, Wolfgang

    2004-03-31

    The surface chemistry of a chiral stationary phase (CSP) with a (tert-butyl carbamoyl) quinine selector immobilized on thiol-modified silica has been characterized by (1)H HR/MAS NMR and (29)Si CP/MAS NMR spectroscopy. The mostly well-resolved (1)H signals could be assigned to stem from the surface-bound selector and the latter suggested a bi- and trifunctional silane linkage. Suspended-state NMR spectroscopy thus proved a well-characterized surface chemistry as proposed. To study chiral recognition phenomena in the presence of the CSP, (1)H HR/MAS 2D transfer NOESY investigations in methanol-d(4) have been undertaken with various solutes including N-3,5-dinitrobenzoyl derivatives of leucine (DNB-Leu) and N-acetyl phenylalanine (Ac-Phe). Both (R)- and (S)-enantiomers of DNB-Leu and Ac-Phe interacted with the tBuCQN-CSP as indicated by negative cross-peaks in the trNOESY spectra, while the 2D NOESY of the dissolved solutes in absence of the chiral stationary phase showed positive cross-peaks. The intensities of the trNOE cross-peaks were much stronger for the (S)-enantiomers. This stereoselectivity paralleled the experimental chromatographic behavior, where the (S)-enantiomers revealed stronger binding and retention on the tBuCQN-CSP as well. Hence, we were able to correlate the retention behavior to the trNOE NMR spectroscopic data in a qualitative manner.

  3. Expanding the horizons for structural analysis of fully protonated protein assemblies by NMR spectroscopy at MAS frequencies above 100 kHz.

    PubMed

    Struppe, Jochem; Quinn, Caitlin M; Lu, Manman; Wang, Mingzhang; Hou, Guangjin; Lu, Xingyu; Kraus, Jodi; Andreas, Loren B; Stanek, Jan; Lalli, Daniela; Lesage, Anne; Pintacuda, Guido; Maas, Werner; Gronenborn, Angela M; Polenova, Tatyana

    2017-07-03

    The recent breakthroughs in NMR probe technologies resulted in the development of MAS NMR probes with rotation frequencies exceeding 100 kHz. Herein, we explore dramatic increases in sensitivity and resolution observed at MAS frequencies of 110-111 kHz in a novel 0.7 mm HCND probe that enable structural analysis of fully protonated biological systems. Proton- detected 2D and 3D correlation spectroscopy under such conditions requires only 0.1-0.5 mg of sample and a fraction of time compared to conventional (13)C-detected experiments. We discuss the performance of several proton- and heteronuclear- ((13)C-,(15)N-) based correlation experiments in terms of sensitivity and resolution, using a model microcrystalline fMLF tripeptide. We demonstrate the applications of ultrafast MAS to a large, fully protonated protein assembly of the 231-residue HIV-1 CA capsid protein. Resonance assignments of protons and heteronuclei, as well as (1)H-(15)N dipolar and (1)H(N) CSA tensors are readily obtained from the high sensitivity and resolution proton-detected 3D experiments. The approach demonstrated here is expected to enable the determination of atomic-resolution structures of large protein assemblies, inaccessible by current methodologies. Copyright © 2017. Published by Elsevier Inc.

  4. Solid state structure by X-ray and 13C CP/MAS NMR of new 5-[2-(N,N-dimethylamino)ethoxy]-4,7-dimethylcoumarins

    NASA Astrophysics Data System (ADS)

    Ostrowska, Kinga; Maciejewska, Dorota; Dobrzycki, Łukasz; Socha, Pawel

    2016-05-01

    5-[2-(N,N-dimethylamino)ethoxy]-4,7-dimethylcoumarin (1) and 6-acetyl-5-[2-(N,N-dimethylamino)ethoxy]-4,7-dimethylcoumarin (2), structurally related, were synthesized using both conventional and microwave-assisted approach. An impact of acetyl groups on the molecular structure of coumarin derivatives has been examined. Crystals of 2 were investigated using single crystal and powder X-ray diffraction techniques. Compound 2 crystallizes forming two polymorphs (denoted as 2_1 and 2_2), both belonging to P21/c space group. Both polymorphs are comparably stable and can be formed simultaneously during crystallization process. The solid state structure was also analysed using the fully resolved 13C CP/MAS NMR. The double signals with the intensity ratio of about 1:1 which were observed in the 13C CP/MAS NMR spectrum of compound 1 must arise due to the presence of two conformers of 1. In contrast, NMR spectrum recorded for powder mixture of two polymorphs of compound 2 displays no signal splitting. This is related to structural similarities of molecules in both polymorphs.

  5. FTIR and 1H MAS NMR investigations on the correlation between the frequency of stretching vibration and the chemical shift of surface OH groups of solids

    NASA Astrophysics Data System (ADS)

    Brunner, Eike; Karge, H. G.; Pfeifer, H.

    1992-03-01

    The study of surface hydroxyl groups of solids, especially of zeolites, belongs to the 'classical' topics of IR spectroscopy since physico-chemical information may be derived from the wavenumber (nu) OH of the stretching vibration of the different hydroxyls. On the other hand, the last decade has seen the development of high resolution solid-state NMR spectroscopy and through the use of the so-called magic-angle-spinning technique (MAS) the signals of different hydroxyl species can be resolved in the 1H NMR spectra of solids. The chemical shift (delta) H describing the position of these lines may be used as well as (nu) OH to characterize quantitatively the strength of acidity of surface OH groups of solids. In a first comparison of (nu) OH with (delta) H for several types of surface OH groups, a linear correlation between them could be found. The aim of this paper was to prove the validity of this correlation for a wide variety of hydroxyls. The IR measurements were carried out on a Perkin-Elmer FTIR spectrometer 1800 at the Fritz Haber Institute of the Max Planck Society, Berlin, and the 1H MAS NMR spectra were recorded on a Bruker MSL- 300 at the University of Leipzig.

  6. Obtaining aluminas from the thermal decomposition of their different precursors: An {sup 27}Al MAS NMR and X-ray powder diffraction studies

    SciTech Connect

    Chagas, L.H.; De Carvalho, G.S.G.; San Gil, R.A.S.; Chiaro, S.S.X.; Leitão, A.A.; Diniz, R.

    2014-01-01

    Graphical abstract: - Highlights: • We synthesized three precursors of alumina from different methods. • The calcination of the precursors generated several alumina polymorphs. • XRD and NMR were used for structural investigation of the polymorphs. • The synthesis route determines the structural and textural properties of the solids. - Abstract: A commercial sample of Boehmite was used as precursor of alumina polymorphs. For comparison, three other precursors were synthesized from different methods. Particularly, the use of excess of urea promoted a very crystalline form of basic aluminum carbonate. The characteristics of the four precursors were investigated by thermal, vibrational and X-ray powder diffraction (XRD) analysis. Additionally, the nuclear magnetic resonance, with magic angle spinning ({sup 27}Al MAS NMR), was used to verify the coordination of aluminum cations. Each precursor was calcined at various temperatures generating alumina polymorphs, which were structurally analyzed by XRD and {sup 27}Al MAS NMR. Due to interest in catalysis supports, special attention was given to the γ-Al{sub 2}O{sub 3} phase, which in addition to structural investigation was subjected to textural analysis. The results showed that, from different synthesis procedures and common route of calcination, one can obtain materials with the same composition but with different structural and textural properties, which in turn can significantly influence the performance of a supported catalyst.

  7. The combined use of quantum chemical calculations and CP/MAS NMR spectroscopy to investigate soil bound residues of labeled xenobiotics

    NASA Astrophysics Data System (ADS)

    Lewandowski, Hans; Philipp, Herbert; Meier, Robert J.; Narres, Hans-Dieter; Berns, Anne E.

    2010-05-01

    Application of solid state Nuclear Magnetic Resonance (NMR) spectroscopy to 13C- and 15N-labeled compounds is a powerful tool to study the interactions of xenobiotics with soil and its components. The type of interaction with soil components, like organic matter or the mineral phase, influences binding and release of a xenobiotic and its metabolites in soil. As such interactions to the soil matrix cause shifts in the initial positions of the NMR signals of the investigated labeled compound, NMR can be used to elucidate the binding type of bound residues. Density functional theory (DFT) calculations are excellent suited to support such NMR studies of xenobiotics. In a first step, DFT calculations were used to support the interpretation of the spectra of labeled xenobiotics, their metabolites and reaction products synthesized through reaction with model substances (representing specific functionalities of humic substances). In a second step, they allow to evaluate the influence of possible bonds on the initial chemical shift (e.g. towards higher or lower field). This can be especially helpful in the case of bonds like van-der-Waals interactions, for which it is difficult to prepare defined model substances. CP/MAS-NMR spectroscopy and DFT calculations were applied to study the interactions of several labeled xenobiotics and soil organic matter.

  8. Magnetotunneling absorption in double quantum wells

    SciTech Connect

    Lyo, S.K.

    1996-06-01

    Tunneling absorption is calculated in weakly coupled n-type asymmetric double quantum wells in an in-plane magnetic field using a linear response theory. Photon-assisted tunneling occurs between the ground sublevels of the quantum wells. We show that the absorption threshold, the resonance energy of absorption, and the linewidth depend sensitively on the magnetic field and the temperature.

  9. Determining hydrogen-bond interactions in spider silk with 1H-13C HETCOR fast MAS solid-state NMR and DFT proton chemical shift calculations.

    PubMed

    Holland, Gregory P; Mou, Qiushi; Yarger, Jeffery L

    2013-07-28

    Two-dimensional (2D) (1)H-(13)C heteronuclear correlation (HETCOR) solid-state NMR spectra collected with fast magic angle spinning (MAS) are used in conjunction with density functional theory (DFT) proton chemical shift calculations to determine the hydrogen-bonding strength for ordered β-sheet and disordered 310-helical structures in spider dragline silk. The hydrogen-bond strength is determined to be identical for both structures in spider silk with a 1.83-1.84 Å NH···OC hydrogen-bond distance.

  10. Satellite transitions acquired in real time by magic angle spinning (STARTMAS): ``Ultrafast'' high-resolution MAS NMR spectroscopy of spin I =3/2 nuclei

    NASA Astrophysics Data System (ADS)

    Thrippleton, Michael J.; Ball, Thomas J.; Wimperis, Stephen

    2008-01-01

    The satellite transitions acquired in real time by magic angle spinning (STARTMAS) NMR experiment combines a train of pulses with sample rotation at the magic angle to refocus the first- and second-order quadrupolar broadening of spin I =3/2 nuclei in a series of echoes, while allowing the isotropic chemical and quadrupolar shifts to evolve. The result is real-time isotropic NMR spectra at high spinning rates using conventional MAS equipment. In this paper we describe in detail how STARTMAS data can be acquired and processed with ease on commercial equipment. We also discuss the advantages and limitations of the approach and illustrate the discussion with numerical simulations and experimental data from four different powdered solids.

  11. Yeast-expressed human membrane protein aquaporin-1 yields excellent resolution of solid-state MAS NMR spectra.

    PubMed

    Emami, Sanaz; Fan, Ying; Munro, Rachel; Ladizhansky, Vladimir; Brown, Leonid S

    2013-02-01

    One of the biggest challenges in solid-state NMR studies of membrane proteins is to obtain a homogeneous natively folded sample giving high spectral resolution sufficient for structural studies. Eukaryotic membrane proteins are especially difficult and expensive targets in this respect. Methylotrophic yeast Pichia pastoris is a reliable producer of eukaryotic membrane proteins for crystallography and a promising economical source of isotopically labeled proteins for NMR. We show that eukaryotic membrane protein human aquaporin 1 can be doubly ((13)C/(15)N) isotopically labeled in this system and functionally reconstituted into phospholipids, giving excellent resolution of solid-state magic angle spinning NMR spectra.

  12. (23)Na multiple-quantum MAS NMR of the perovskites NaNbO(3) and NaTaO(3).

    PubMed

    Ashbrook, Sharon E; Le Pollès, Laurent; Gautier, Régis; Pickard, Chris J; Walton, Richard I

    2006-08-07

    The distorted perovskites NaTaO(3) and NaNbO(3) have been studied using (23)Na multiple-quantum (MQ) MAS NMR. NaTaO(3) was prepared by high temperature solid state synthesis and the NMR spectra are consistent with the expected room temperature structure of the material (space group Pbnm), with a single crystallographic sodium site. Two samples of NaNbO(3) were studied. The first, a commercially available sample which was annealed at 900 degrees C, showed two crystallographic sodium sites, as expected for the room temperature structure of the material (space group Pbcm). The second sample, prepared by a low temperature hydrothermal method, showed the presence of four sodium sites, two of which match the expected room temperature structure and the second pair, another polymorph of the material (space group P21ma). This is consistent with powder X-ray diffraction data which showed weak extra peaks which can be accounted for by the presence of this second polymorph. Density functional theory (DFT) calculations support our conclusions, and aid assignment of the NMR spectra. Finally, we discuss the measured NMR parameters in relation to other studies of sodium in high coordination sites in the solid state.

  13. Action Spectroscopy on Dense Samples of Photosynthetic Reaction Centers of Rhodobacter sphaeroides WT Based on Nanosecond Laser-Flash C Photo-CIDNP MAS NMR.

    PubMed

    Daviso, Eugenio; Diller, Anna; Gast, Peter; Alia, A; Lugtenburg, Johan; Müller, Marc G; Matysik, Jörg

    2010-03-01

    Photochemically induced dynamic nuclear polarization magic-angle spinning nuclear magnetic resonance (photo-CIDNP MAS NMR) allows for the investigation of the electronic structure of the photochemical machinery of photosynthetic reaction centers (RCs) at atomic resolution. For such experiments, either continuous radiation from white xenon lamps or green laser pulses are applied to optically dense samples. In order to explore their optical properties, optically thick samples of isolated and quinone-removed RCs of the purple bacteria of Rhodobacter sphaeroides wild type are studied by nanosecond laser-flash (13)C photo-CIDNP MAS NMR using excitation wavelengths between 720 and 940 nm. Action spectra of both the transient nuclear polarization as well as the nuclear hyperpolarization, remaining in the electronic ground state at the end of the photocycle, are obtained. It is shown that the signal intensity is limited by the amount of accessible RCs and that the different mechanisms of the photo-CIDNP production rely on the same photophysical origin, which is the photocycle induced by one single photon.

  14. High field 27Al MAS NMR and TPD studies of active sites in ethanol dehydration using thermally treated transitional aluminas as catalysts

    SciTech Connect

    Hu, Jian Zhi; Xu, Suochang; Kwak, Ja Hun; Hu, Mary Y.; Wan, Chuan; Zhao, Zhenchao; Szanyi, Janos; Bao, Xinhe; Han, Xiuwen; Wang, Yong; Peden, Charles H. F.

    2016-04-01

    High field quantitative 27Al MAS NMR and temperature programmed desorption (TPD) of ethanol are used to study the surface and phase transformation of gamma-Al2O3 during calcination in the temperature range of 500 to 1300 degrees C. Following ethanol adsorption, ethylene is generated during TPD with a desorption temperature > 200 degrees C. With increasing calcination temperature prior to TPD, the amount of ethylene produced decreases monotonically. Significantly, 27Al MAS NMR reveals that the amount of penta-coordinate Al3+ ions (Lewis acid sites) also decreases with increasing calcination temperature. In fact, a strong correlation between the amount of penta-coordinate Al3+ ions and the amount of strongly adsorbed ethanol molecules (i.e., the ones that convert to ethylene during TPD) is obtained. This result indicates that the penta-coordinate aluminum sites are the catalytic active sites on alumina surfaces during ethanol dehydration reaction across the entire course of gamma- to alpha-Al2O3 phase transformations.

  15. Solid state {sup 31}P/{sup 27}Al and {sup 31}P/{sup 23}Na MAS NMR dipolar dephasing investigations of connectivity in sodium aluminophosphate glasses

    SciTech Connect

    LANG,DAVID P.; ALAM,TODD M.; BENCOE,DENISE N.

    2000-05-01

    Solid state {sup 31}P/{sup 27}Al and {sup 31}P/{sup 23}Na MAS NMR dipolar dephasing experiments have been used to investigate the spatial distribution of aluminum and sodium cations with respect to the phosphate backbone for a series of sodium aluminophosphate glasses, xAl{sub 2}O{sub 3}{center_dot}50Na{sub 2}O{center_dot}(50{minus}x)P{sub 2}O{sub 5} (0{le} x {le} 17.5). From the {sup 31}P/{sup 27}Al and {sup 31}P/{sup 23}Na connectivity data gathered, information about the medium range order in these glasses is obtained. The expanded connectivity data allows for better identification and interpretation of the new resonances observed in the {sup 31}P MAS NMR spectra with the addition of alumina. The results of the dipolar dephasing experiments show that the sodium-phosphate distribution remains relatively unchanged for the glass series, and that the addition of aluminum occurs primarily through the depolymerization of the phosphate tetrahedral backbone.

  16. MAS NMR, DRIFT, and FT-Raman Characterization of SiO(2)-AlPO(4)-B(2)O(3) Ternary Catalytic Systems.

    PubMed

    Aramendía; Boráu; Jiménez; Marinas; Ruiz; Urbano

    1999-09-01

    This work deals with the preparation of SiO(2)-AlPO(4)-B(2)O(3) ternary systems from impregation of a SiO(2)-AlPO(4) solid previously synthesized with B(OH)(3) (0-10% B(OH)(3), by weight). Characterization of the resulting solids has been carried out from adsorption-desorption isotherms of nitrogen, DRIFT, FT-Raman, pyridine adsorption, and (1)H, (11)B, (27)Al, and (31)P MAS NMR. The textural properties are scarcely changed by the impregnation and calcination steps. Moreover, the MAS NMR experiments indicated that the components of the solids do not interact among them. The solids were tested in the dehydration-dehydrogenation of propan-2-ol, widely used to correlate catalytic activity with the surface acid-base properties of the solids. The catalytic results indicate that the effect of boron dopping is an increase in the overall acidity of the solids. Copyright 1999 Academic Press.

  17. Separation of small metabolites and lipids in spectra from biopsies by diffusion-weighted HR-MAS NMR: a feasibility study.

    PubMed

    Diserens, G; Vermathen, M; Precht, C; Broskey, N T; Boesch, C; Amati, F; Dufour, J-F; Vermathen, P

    2015-01-07

    High Resolution Magic Angle Spinning (HR-MAS) NMR allows metabolic characterization of biopsies. HR-MAS spectra from tissues of most organs show strong lipid contributions that are overlapping metabolite regions, which hamper metabolite estimation. Metabolite quantification and analysis would benefit from a separation of lipids and small metabolites. Generally, a relaxation filter is used to reduce lipid contributions. However, the strong relaxation filter required to eliminate most of the lipids also reduces the signals for small metabolites. The aim of our study was therefore to investigate different diffusion editing techniques in order to employ diffusion differences for separating lipid and small metabolite contributions in the spectra from different organs for unbiased metabonomic analysis. Thus, 1D and 2D diffusion measurements were performed, and pure lipid spectra that were obtained at strong diffusion weighting (DW) were subtracted from those obtained at low DW, which include both small metabolites and lipids. This subtraction yielded almost lipid free small metabolite spectra from muscle tissue. Further improved separation was obtained by combining a 1D diffusion sequence with a T2-filter, with the subtraction method eliminating residual lipids from the spectra. Similar results obtained for biopsies of different organs suggest that this method is applicable in various tissue types. The elimination of lipids from HR-MAS spectra and the resulting less biased assessment of small metabolites have potential to remove ambiguities in the interpretation of metabonomic results. This is demonstrated in a reproducibility study on biopsies from human muscle.

  18. Bonding Preferences of Non-Bridging Oxygens in Calcium Aluminosilicate Glass: Evidence from O-17 MAS and 3QMAS NMR on Calcium Aluminate Glass

    NASA Astrophysics Data System (ADS)

    Allwardt, J. R.; Lee, S.; Stebbins, J.

    2001-12-01

    Non-bridging oxygens (NBO's) play a significant role in the thermodynamic and transport properties in glasses and silicate melts. Previous oxygen-17 (O-17) triple quantum magic angle spinning (3QMAS NMR) data have shown the presence of NBO's in several calcium aluminosilicate (CAS) glasses on the CaAl2O4-SiO2 join (Stebbins and Xu 1997). The observed chemical shifts of these glasses are similar to those for the NBO in calcium silicate glasses (Stebbins et al. 1997 and Stebbins et al 1999); however, a recent O-17 MAS NMR study of crystalline CaAl2O4 showed that the NBO peak in an associated impurity phase is shifted to a higher frequency by 30 to 40 ppm from that of CAS and Ca-silicate glasses (Stebbins et al. in press). This finding suggests that Si is the preferred network cation for NBO's in aluminosilicate glasses and melts at the glass transition temperature. The preference for Si over that of Al as the network cation host for NBO's has also been suggested by Raman and other spectroscopic techniques (Mysen 1988). To investigate this apparent preference for Si-NBO, O-17 3QMAS and MAS experiments were conducted to examine the location of the NBO peak in the spectra of a calcium aluminate glass. Since the CaAl2O4 glass is difficult to make by conventional cooling methods, the binary eutectic composition (63CaO-37Al2O3) was chosen. The resulting O-17 MAS spectrum shows an intense, relatively narrow peak centered at 72 ppm, which nearly coincides with the peak location and width of the Al-O-Al peak in the crystalline Ca-aluminates (Stebbins et al. in press.) (70 ppm). There is a broader, less intense peak centered at 155 ppm that is assigned to the Al-NBO peak. This peak is in approximately the same location as that for a Ca-aluminate phase reported by Stebbins et al. (in press) (137 ppm). In addition, our 3QMAS data show that the peak maximum of the NBO in the Ca-aluminate (-85 and 150 ppm in isotropic and MAS dimensions, respectively) differs significantly from

  19. Formation and decomposition of N,N,N-trimethylanilinium cations on zeolite H-Y investigated by in situ stopped-flow MAS NMR spectroscopy.

    PubMed

    Wang, Wei; Seiler, Michael; Ivanova, Irina I; Sternberg, Ulrich; Weitkamp, Jens; Hunger, Michael

    2002-06-26

    Methylation of aniline by methanol on zeolite H-Y has been investigated by in situ (13)C MAS NMR spectroscopy under flow conditions. The in situ (13)C continuous-flow (CF) MAS NMR experiments were performed at reaction temperatures between 473 and 523 K, molar methanol-to-aniline ratios of 1:1 to 4:1, and modified residence times of (13)CH(3)OH between 20 and 100 (g x h)/mol. The methylation reaction was shown to start at 473 K. N,N,N-Trimethylanilinium cations causing a (13)C NMR signal at 58 ppm constitute the major product on the catalyst surface. Small amounts of protonated N-methylaniline ([PhNH(2)CH(3)](+)) and N,N-dimethylaniline ([PhNH(CH(3))(2)](+)) were also observed at ca. 39 and 48 ppm, respectively. After increase of the temperature to 523 K, the contents of N,N-dimethylanilinium cations and ring-alkylated reaction products strongly increased, accompanied by a decrease of the amount of N,N,N-trimethylanilinium cations. With application of the in situ stopped-flow (SF) MAS NMR technique, the decomposition of N,N,N-trimethylanilinium cations on zeolite H-Y to N,N-dimethylanilinium and N-methylanilinium cations was investigated to gain a deeper insight into the reaction mechanism. The results obtained allow the proposal of a mechanism consisting of three steps: (i) the conversion of methanol to surface methoxy groups and dimethyl ether (DME); (ii) the alkylation of aniline with methanol, methoxy groups, or DME leading to an equilibrium mixture of N,N,N-trimethylanilinium, N,N-dimethylanilinium, and N-methylanilinium cations attached to the zeolite surface; (iii) the deprotonation of N,N-dimethylanilinium and N-methylanilinium cations causing the formation of N,N-dimethylaniline (NNDMA) and N-methylaniline (NMA) in the gas phase, respectively. The chemical equilibrium between the anilinium cations carrying different numbers of methyl groups is suggested to play a key role for the products distribution in the gas phase.

  20. {sup 13}C chemical shift anisotropies for carbonate ions in cement minerals and the use of {sup 13}C, {sup 27}Al and {sup 29}Si MAS NMR in studies of Portland cement including limestone additions

    SciTech Connect

    Sevelsted, Tine F.; Herfort, Duncan

    2013-10-15

    {sup 13}C isotropic chemical shifts and chemical shift anisotropy parameters have been determined for a number of inorganic carbonates relevant in cement chemistry from slow-speed {sup 13}C MAS or {sup 13}C({sup 1}H) CP/MAS NMR spectra (9.4 T or 14.1 T) for {sup 13}C in natural abundance. The variation in the {sup 13}C chemical shift parameters is relatively small, raising some doubts that different carbonate species in Portland cement-based materials may not be sufficiently resolved in {sup 13}C MAS NMR spectra. However, it is shown that by combining {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR carbonate anions in anhydrous and hydrated phases can be distinguished, thereby providing valuable information about the reactivity of limestone in cement blends. This is illustrated for three cement pastes prepared from an ordinary Portland cement, including 0, 16, and 25 wt.% limestone, and following the hydration for up to one year. For these blends {sup 29}Si MAS NMR reveals that the limestone filler accelerates the hydration for alite and also results in a smaller fraction of tetrahedrally coordinated Al incorporated in the C-S-H phase. The latter result is more clearly observed in {sup 27}Al MAS NMR spectra of the cement–limestone blends and suggests that dissolved aluminate species in the cement–limestone blends readily react with carbonate ions from the limestone filler, forming calcium monocarboaluminate hydrate. -- Highlights: •{sup 13}C chemical shift anisotropies for inorganic carbonates from {sup 13}C MAS NMR. •Narrow {sup 13}C NMR chemical shift range (163–171 ppm) for inorganic carbonates. •Anhydrous and hydrated carbonate species by {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR. •Limestone accelerates the hydration for alite in Portland – limestone cements. •Limestone reduces the amount of aluminium incorporated in the C-S-H phase.

  1. Slow-down of 13C spin diffusion in organic solids by fast MAS: a CODEX NMR Study.

    PubMed

    Reichert, D; Bonagamba, T J; Schmidt-Rohr, K

    2001-07-01

    One- and two-dimensional 13C exchange nuclear magnetic resonance experiments under magic-angle spinning (MAS) can provide detailed information on slow segmental reorientations and chemical exchange in organic solids, including polymers and proteins. However, observations of dynamics on the time scale of seconds or longer are hampered by the competing process of dipolar 13C spin exchange (spin diffusion). In this Communication, we show that fast MAS can significantly slow down the dipolar spin exchange effect for unprotonated carbon sites. The exchange is measured quantitatively using the centerband-only detection of exchange technique, which enables the detection of exchange at any spinning speed, even in the absence of changes of isotropic chemical shifts. For chemically equivalent unprotonated 13C sites, the dipolar spin exchange rate is found to decrease slightly less than proportionally with the sample-rotation frequency, between 8 and 28 kHz. In the same range, the dipolar spin exchange rate for a glassy polymer with an inhomogeneously broadened MAS line decreases by a factor of 10. For methylene groups, no or only a minor slow-down of the exchange rate is found.

  2. Probing the location and distribution of paramagnetic centers in alkali metal-loaded zeolites through (7)Li MAS NMR.

    PubMed

    Terskikh, Victor V; Ratcliffe, Christopher I; Ripmeester, John A; Reinhold, Catherine J; Anderson, Paul A; Edwards, Peter P

    2004-09-15

    The nature and surroundings of lithium cations in lithium-exchanged X and A zeolites following loading with the alkali metals Na, K, Rb, and Cs have been studied through (7)Li solid-state NMR spectroscopy. It is demonstrated that the lithium in these zeolites is stable with respect to reduction by the other alkali metals. Even though the lithium cations are not directly involved in chemical interactions with the excess electrons introduced in the doping process, the corresponding (7)Li NMR spectra are extremely sensitive to paramagnetic species that are located inside the zeolite cavities. This sensitivity makes (7)Li NMR a useful probe to study the formation, distribution, and transformation of such species.

  3. Size- and site-dependent reconstruction in CdSe QDs evidenced by 77Se{1H} CP-MAS NMR spectroscopy.

    PubMed

    Lovingood, Derek D; Achey, Randall; Paravastu, Anant K; Strouse, Geoffrey F

    2010-03-17

    Evidence of size-dependent reconstruction in quantum dots leading to changes in bonding is observed through analysis of the (77)Se{(1)H} cross-polarization magic angle spinning and (77)Se spin-echo solid-state NMR for Cd(77)Se quantum dots. The CP-MAS and spin-echo data indicate discrete surface and core (77)Se sites exist with the QD, in which the surface is comprised of numerous reconstructed lattice planes. Due to the nearly 100% enrichment level for (77)Se, efficient spin coupling is observed between the surface (77)Se and sublayer (77)Se sites due to spin diffusion in the Cd(77)Se quantum dots. The observed chemical shift for the discrete (77)Se sites can be correlated to the effective mass approximation via the Ramsey expression, indicating a 1/r(2) size dependence for the change in chemical shift with size, while a plot of chemical shift versus the inverse band gap is linear. The correlation of NMR shift for the discrete sites allows a valence bond theory interpretation of the size-dependent changes in bonding character within the reconstructed QD. The NMR results provide a structural model for the QDs in which global reconstruction occurs below 4 nm in diameter, while an apparent self-limiting reconstruction process occurs above 4 nm.

  4. Investigation of the Use of Solid State Cp/mas NMR for Characterization of Thermoplastic Polyamides and Unique Thermally Curable Polyamides Containing the Cyclobutene Moiety.

    NASA Astrophysics Data System (ADS)

    Powell, Douglas Graham

    1990-08-01

    A series of model diamides was synthesized from mono- and disubstituted amines with the diacid chloride of cyclobutene-1,2-dicarboxylic acid. Relative rates of thermolysis (by DSC) were dependent on the number and type of substituents. Thermolysis products were Diels-Alder dimers and spontaneously formed polymers. Thermal imidization of cycloadducts was possible in some cases with concomitant oxidation to N, N^'-disubstituted aromatic bisimides. Polyamides were prepared from cyclobutene-1,2 -dicarboxylic acid using low temperature condensation reaction conditions. The unusual solubility characteristics of the diacid as well as the instability of the diacid chloride severely limited formation of high molecular weight polymers. Secondary monomers were synthesized in order to take advantage of the more predictable reactivity of the aromatic carboxyl group. Secondary monomers were polymerized with diamine comonomers using low temperature condensation methods. Solid state ^{13}C CP/MAS NMR confirmed the polymer structure. The thermalized product was found to be insoluble, although swellable, in polar aprotic solvents. Solid state ^{13 }C NMR spectra of the thermal products confirmed crosslinking by intermolecular Diels-Alder cycloaddition. Several important aliphatic polyamides were characterized using high resolution techniques with an emphasis on the ^{15}N nucleus. Chemical shifts from ^{15}N CP/MAS were found to correlate with the alpha and gamma crystal forms found in aliphatic polyamides. This chemical shift difference is rationalized as a conformationally dependent interaction of the amide nitrogen with its substituents. Evidence is presented from molecular orbital calculations which support this theory. Nylon 6 and nylon 11 were synthesized with 20% and 99% ^{15}N enrichment, respectively. ^{15}N CP/MAS of the enriched nylon 6 showed the amorphous region of the polymer for the first time. ^{15 }N relaxation times (T_1, T_1_rho) confirmed the assignment of the

  5. Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2016-01-21

    Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t{sub 1} and t{sub 3} periods, respectively. In addition to through-space and through-bond {sup 13}C/{sup 1}H and {sup 13}C/{sup 13}C chemical shift correlations, the 3D {sup 1}H/{sup 13}C/{sup 1}H experiment also provides a COSY-type {sup 1}H/{sup 1}H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices ({sup 1}H/{sup 1}H chemical shift correlation spectrum) at different {sup 13}C chemical shift frequencies from the 3D {sup 1}H/{sup 13}C/{sup 1}H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the

  6. Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS

    PubMed Central

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2016-01-01

    Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D 1H/13C/1H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t1 and t3 periods, respectively. In addition to through-space and through-bond 13C/1H and 13C/13C chemical shift correlations, the 3D 1H/13C/1H experiment also provides a COSY-type 1H/1H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices (1H/1H chemical shift correlation spectrum) at different 13C chemical shift frequencies from the 3D 1H/13C/1H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the 3D 1H/13C/1H experiment would be useful to study the structure and dynamics of a variety of chemical and biological

  7. Efficient Resonance Assignment of Proteins in MAS NMR by Simultaneous Intra- and Inter-residue 3D Correlation Spectroscopy

    PubMed Central

    Daviso, Eugenio; Eddy, Matthew T.; Andreas, Loren B.; Griffin, Robert G.; Herzfeld, Judith

    2013-01-01

    Resonance assignment is the first step in NMR structure determination. For magic angle spinning NMR, this is typically achieved with a set of heteronuclear correlation experiments (NCaCX, NCOCX, CONCa) that utilize SPECIFIC-CP 15N-13C transfers. However, the SPECIFIC-CP transfer efficiency is often compromised by molecular dynamics and probe performance. Here we show that one-bond ZF-TEDOR 15N-13C transfers provide simultaneous NCO and NCa transfers with at least as much sensitivity as SPECIFIC-CP for some non-crystalline samples. Furthermore, a 3D TEDOR-CC experiment provides heteronuclear sidechains correlations and robustness with respect to proton decoupling and radiofrequency power instabilities. We demonstrate transfer efficiencies and connectivities by application of 3D ZF-TEDOR-DARR to a model microcrystalline protein, GB1, and a less ideal system, GvpA in intact gas vesicles. PMID:23334347

  8. 13C CP MAS NMR and GIAO-CHF/DFT calculations of flavonoids: Morin, kaempferol, tricin, genistein, formononetin and 3,7-dihydroxyflavone

    NASA Astrophysics Data System (ADS)

    Zielińska, Agnieszka; Paradowska, Katarzyna; Jakowski, Jacek; Wawer, Iwona

    2008-02-01

    13C CP MAS NMR spectra of the flavonoids: morin, kaempferol, 3,7-dihydroxyflavone, tricin and isoflavones: genistein and formononetin were recorded to characterize solid-state conformations. Intramolecular hydrogen bonds forming five-, six- and seven-membered rings are present in the two morin molecules in the crystals - their 13C resonances have been assigned with the aid of the calculated shielding constants. Linear relationships between the calculated shielding constants σDFT (ppm) and chemical shifts ( δCPMAS, ppm) were obtained for all studied compounds. Higher correlation coefficients suggest that the conformation with "clockwise" orientation of both OH groups is more probable in the solid 3,7-dihydroxyflavone, whereas in the solid formononetin the OH and OCH 3 substituents are directed "anticlockwise". The barrier to the rotation of phenyl ring B decreases in the order: morin (2'-OH, 3-OH) > kaempferol (3-OH) > tricin.

  9. A study of structure and dynamics of poly(aspartic acid) sodium/poly(vinyl alcohol) blends by 13C CP/MAS NMR

    NASA Astrophysics Data System (ADS)

    Wang, P.; Ando, I.

    1999-09-01

    Solid state 13C CP/MAS NMR measurements have been carried out on poly(aspartic acid) sodium (PAANa)/poly(vinyl alcohol) (PVA) blends over a wide range of temperatures. From these experimental results, it is found that the main-chain conformations of PAANa in PAANa/PVA blends take the α-helix form over a wide range of blend ratios, and, in contrast, the conformation and dynamics of the side chains of PAANa are strongly influenced by the formation of an intermolecular hydrogen bond between the carboxyl group of the side chains and the hydroxyl group of PVA. The behavior of the proton spin-lattice relaxation times in the rotating frame ( T1 ρ(H)) and the laboratory frame ( T1(H)) indicates that when the blend ratio of PAANa and PVA is 1:1, they are miscible.

  10. Modification of structure and digestibility of chestnut starch upon cooking: a solid state (13)C CP MAS NMR and enzymatic degradation study.

    PubMed

    Pizzoferrato, L; Rotilio, G; Paci, M

    1999-10-01

    The modification of starch, which is the major component of the polysaccharide fraction of chestnuts (Castanea sativa), has been studied from the point of view of structure and digestibility to understand the modifications induced by cooking and, specifically, by the Maillard reaction. The study was carried out by enzymatic degradation kinetics, monitoring the glucose released upon time, and by solid state (13)C CP MAS NMR, which has the potential of monitoring the solid state phase changes occurring upon chemical modification due to the cooking process. Results obtained reveal that large changes are induced in the macromolecular structure of starchy materials and that these changes are correlated with changes of digestibility in terms of enzymatic degradation resistance. In the system studied, the extension of the Maillard reaction is not such as to exert a significant influence on structure and/or digestibility of chestnut starch.

  11. In Situ High Temperature High Pressure MAS NMR Study on the Crystallization of AlPO 4 -5

    SciTech Connect

    Zhao, Zhenchao; Xu, Suochang; Hu, Mary Y.; Bao, Xinhe; Hu, Jian Zhi

    2016-01-28

    A damped oscillating crystallization process of AlPO4-5 at the presence of small amount of water is demonstrated by in situ high temperature high pressure multinuclear MAS NMR. Crystalline AlPO4-5 is formed from an intermediate semicrystalline phase via continuous rearrangement of the local structure of amorphous precursor gel. Activated water catalyzes the rearrangement via repeatedly hydrolysis and condensation reaction. Strong interactions between organic template and inorganic species facilitate the ordered rearrangement. During the crystallization process, excess water, phosphate, and aluminums are expelled from the precursor. The oscillating crystallization reflects mass transportation between the solid and liquid phase during the crystallization process. This crystallization process is also applicable to AlPO4-5 crystallized in the presence of a relatively large amount of water.

  12. Structural, optical and luminescence properties of Dy3+ doped bismuth phosphate glasses: Insights from 31P MAS NMR, absorption and photoluminescence

    NASA Astrophysics Data System (ADS)

    Damodaraiah, S.; Prasad, V. Reddy; Ratnakaram, Y. C.

    2017-05-01

    An investigation was carried out to observe structural and optical properties of 0.5 mol% Dy3+ doped different compositions of bismuth phosphate glasses (5, 10, 15 and 20 mol% Bi2O3). The structural characterization was accomplished by X-ray diffraction (XRD), 31P magic angle spin nuclear magnetic resonance (MAS NMR) spectroscopy. The optical properties were studied using absorption and photo luminescence (PL) spectroscopy. Judd-Ofelt intensity parameters Ωλ (λ=2, 4 and 6) were evaluated from absorption spectra. From photoluminescence spectra, experimental branching ratios (βexp) and stimulated emission cross-sections (σP) were calculated. The decay profiles for 4F9/2 level were recorded and were fit exponential. The obtained results show the prepared Dy3+ doped bismuth phosphate glasses might be useful as good optical material for yellow emission.

  13. Crystal structure of silica-ZSM-12 by the combined use of high-resolution solid-state MAS NMR spectroscopy and synchrotron x-ray powder diffraction

    SciTech Connect

    Fyfe, C.A.; Kokotailo, G.T. ); Gies, H.; Marler, B. ); Cox, D.E. )

    1990-05-03

    The crystal structure of the synthetic zeolite silica-ZSM-12, 56 SiO{sub 2}, has been solved by the combined use of high-resolution solid-state MAS NMR spectroscopy and high-resolution synchrotron X-ray powder diffraction ZSM-12 crystallizes in the monoclinic space group C2/c with a{sub 0} = 24.863 {angstrom}, b{sub 0} = 5.012 {angstrom}, c{sub 0} = 24.328 {angstrom}, and {beta} = 107.7{degree}. The zeolite host structure is built from corner-linked SiO{sub 4} tetrahedra to give a three-dimensional 4-connected net. The pores of the structure are one-dimensional channels that do not intersect, with 12-membered ring pore openings of approximately 5.6 {times} 7.7 {angstrom}. The structure of ZSM-12 is frequently twinned with (100) as the twin plane, which indicates a new zeolite structure type.

  14. 29Si{1H} CP-MAS NMR comparison and ATR-FTIR spectroscopic analysis of the diatoms Chaetoceros muelleri and Thalassiosira pseudonana grown at different salinities.

    PubMed

    La Vars, Sian M; Johnston, Martin R; Hayles, John; Gascooke, Jason R; Brown, Melissa H; Leterme, Sophie C; Ellis, Amanda V

    2013-04-01

    Diatoms are key indicators of marine environmental health. To further understand how diatoms respond to varying degrees of salinity, either due to climate change or brine waste discharge into marine environments, two different diatom species were studied. Thalassiosira pseudonana and Chaetoceros muelleri were cultured at three different salinities namely, 26 practical salinity units (PSU or parts per thousand), 36 PSU (standard salinity for culturing of seawater species) and 46 PSU. Changes in silica and organic content within the cultured diatoms were analysed using solid-state (29)Si{(1)H} cross-polarization-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopies coupled with analysis of variance. (29)Si CP-MAS NMR showed that qualitatively the Q4:Q3 area ratios of C. muelleri, grown away from standard salinities, increased in response to the formation of more condensed (2 ≡SiOH → ≡Si-O-Si≡ + H2O) and/or an increase in closely associated organic matter to the Q4 component of the diatoms. This was not observed for T. pseudonana. However, both species showed the appearance of a new peak centered at 1575-1580 cm(-1) in the ATR-FTIR spectra, designated as the C═N band of nitrogenous purine-type compounds. Further, the C. muelleri species was shown to produce more extracellular polymeric substances at non-standard salinities. On this basis, results suggest that there is a strong relationship between diatom composition and salinity and that C. muelleri is more sensitive to its environment than T. pseudonana.

  15. Synthesis, Infra-red, CP/MAS-NMR characterization, structural study and electrical properties of the bis(4-amino-2-chloropyridinium) tetrachlorozincate (II) monohydrate

    NASA Astrophysics Data System (ADS)

    Karâa, Najla; Hamdi, Besma; Ben Salah, Abdelhamid; Zouari, Ridha

    2013-10-01

    Single crystals of the new ionic salt bis(4-amino-2-chloropyridinium) tetrachlorozincate (II) monohydrate, (C5H6N2Cl)2 ZnCl4ṡH2O, were grown by slow evaporation from aqueous solution at room temperature. The compound was characterized by IR, thermal analysis (TGA-DSC), single crystal X-ray diffraction, CP/MAS-NMR and impedance spectroscopy. The structure (4-amino-2-chloropyridinium)2 ZnCl4·H2O, [(CAP)2ZnCl4·H2O], consists of isolated H2O, isolated [ZnCl4]2- tetrahedral anions and 4-amino-2-chloropyridinium [C5H6N2Cl] + cations, CAP, which are connected together via N-H⋯Cl, N-H⋯O ((N: pyridinium) and (N: amine)), O-H⋯Cl and C-H⋯Cl hydrogen bonds. Cation-cation, offset-face-to-face interactions (π-π stacking) between identical antiparallel CAP (aromatic-aromatic), in which they may be effective in the stabilization of the crystal structure. Solid state CP/MAS-NMR spectra showed five isotropic resonances, 13C, confirming the solid state structure determined by X-ray diffraction. Impedance spectroscopy study, reported for a single crystal, revealed that the conduction in the material was due to a hopping process. This work aims to reveal the thermal properties of a new zinc (II) based organic-inorganic hybrid and the conductivity properties that these compounds exhibit.

  16. Structural elucidation of b-(Y,Sc){sub 2}Si{sub 2}O{sub 7} : combined use of {sub 89}Y MAS NMR and powder diffraction.

    SciTech Connect

    Allix, M.; Alba, M. D.; Florian, P.; Fernandez-Carrion, A. J.; Suchomel, M. R.; Escudero, A.; Suard, E.; Becerro, A. I.

    2011-08-01

    Although the structures of pure Sc{sub 2}Si{sub 2}O{sub 7} and {beta}-Y{sub 2}Si{sub 2}O{sub 7} have been described in the literature using the C2/m space group, {sup 29}Si magic angle spinning (MAS) NMR measurements of the intermediate members of the Sc{sub 2}Si{sub 2}O{sub 7}-{beta}-Y{sub 2}Si{sub 2}O{sub 7} system indicate a lowering of the symmetry to the C2 space group. Indeed, these compositions exhibit a unique Si crystallographic site and an Si-O-Si angle lower than 180{sup o}, incompatible with the C2/m space group. C2 is the only possible alternative. Space group Cm can be discarded with regard to its two different Si sites per unit cell. Moreover, {sup 89}Y MAS NMR data have revealed the existence of two different Y sites in the structure of the intermediate members of the Sc{sub 2}Si{sub 2}O{sub 7}-{beta}-Y{sub 2}Si{sub 2}O{sub 7} system, confirming the lowering of the symmetry to the C2 space group. The viability of the C2 model has therefore been tested and confirmed by refinement of synchrotron and neutron powder diffraction data for the different members of the system. The structural evolutions across the Sc{sub 2}Si{sub 2}O{sub 7}-{beta}-Y{sub 2}Si{sub 2}O{sub 7} system are discussed.

  17. Influence of sodium ion dynamics on the 23Na quadrupolar interaction in sodalite: a high-temperature 23Na MAS NMR study.

    PubMed

    Fechtelkord, M

    2000-01-01

    High-temperature 33Na MAS NMR experiments up to 873 K for a number of different sodalites (Na8[AlSiO4]6(NO3)2, Na8[AlSiO4]6(NO2)2, Na8[AlSiO4]6I2, Na7.9[AlSiO4]6(SCN)7.9 x 0.5H2O, Na8[AlGeO4]6(NO3)2, and Na7[AlSiO4]6(H3O2) x 4H2O) were carried out. The spectra of the first five sodalites consist of a quadrupolar MAS pattern with different quadrupolar coupling constants. The quadrupolar interaction for the thiocyanate sodalite, the nitrate aluminosilicate, and germanate sodalite decreases strongly passing a coalescence state on heating, while the quadrupolar interaction of the iodide and nitrite sample shows nearly no change. The basic hydrosodalite shows an asymmetric lineshape at room temperature and, between 350 and 370 K, a second line due to the evaporation of cage-water emerges. The linewidth increases with rising temperature. The temperature dependence of the quadrupolar interaction seems to be a function of the sodalite beta-cage expansion. Two conceivable jump mechanisms are proposed for a tetrahedral two-site jump between occupied and unoccupied tetrahedral sites.

  18. Terahertz detection using double quantum well devices

    NASA Astrophysics Data System (ADS)

    Khodier, Majid; Christodoulou, Christos G.; Simmons, Jerry A.

    2001-12-01

    This paper discusses the principle of operation of an electrically tunable THz detector, working around 2.54 THz, integrated with a bowtie antenna. The detection is based on the idea of photon-assisted tunneling (PAT) in a double quantum well (DQW) device. The bowtie antenna is used to collect the THz radiation and feed it to the detector for processing. The Bowtie antenna geometry is integrated with the DQW device to achieve broadband characteristic, easy design, and compatibility with the detector fabrication process. The principle of operation of the detector is introduced first. Then, results of different bowtie antenna layouts are presented and discussed.

  19. Mesoscopic admittance of a double quantum dot

    SciTech Connect

    Cottet, Audrey; Mora, Christophe; Kontos, Takis

    2011-03-15

    We calculate the mesoscopic admittance G({omega}) of a double quantum dot (DQD), which can be measured directly using microwave techniques. This quantity reveals spectroscopic information on the DQD and is also directly sensitive to a Pauli spin blockade effect. We then discuss the problem of a DQD coupled to a high quality photonic resonator. When the photon correlation functions can be developed along a random-phase-approximation-like scheme, the response of the resonator gives an access to G({omega}).

  20. (119)Sn MAS NMR and first-principles calculations for the investigation of disorder in stannate pyrochlores.

    PubMed

    Mitchell, Martin R; Reader, Simon W; Johnston, Karen E; Pickard, Chris J; Whittle, Karl R; Ashbrook, Sharon E

    2011-01-14

    The local structure and cation disorder in Y(2)Ti(2-x)Sn(x)O(7) pyrochlores, materials proposed for the encapsulation of lanthanide- and actinide-bearing radioactive waste, is studied using (119)Sn (I = 1/2) NMR spectroscopy. NMR provides an excellent probe of disorder, as it is sensitive to the atomic scale environment without the need for any long-range periodicity. However, the complex and overlapping spectral resonances that often result can be difficult to interpret. Here, we demonstrate how (119)Sn DFT calculations can be used to aid the spectral interpretation and assignment, confirming that Sn occupies only the six-coordinate pyrochlore B site, and that the Sn chemical shift is sensitive to the number of Sn/Ti on the neighbouring B sites. Although distinct resonances are resolved experimentally when the Ti content is low, there is significant spectral overlap for Ti-rich compositions. We establish that this is a result of two competing contributions to the Sn chemical shift; an upfield shift resulting from the incorporation of the more polarizing Ti(4+) cation onto the neighbouring B sites, and a concomitant downfield shift arising from the decrease in unit cell size. Despite the considerably easier spectral acquisition, the lower resolution in the (119)Sn spectra hinders the extraction of the detailed structural information previously obtained using (89)Y NMR. However, the spectra we obtain are consistent with a random distribution of Sn/Ti on the pyrochlore B sites. Finally, we consider whether an equilibrium structure has been achieved by investigating materials that have been annealed for different durations.

  1. Analysis of 31P MAS NMR spectra and transversal relaxation of bacteriophage M13 and tobacco mosaic virus.

    PubMed Central

    Magusin, P C; Hemminga, M A

    1994-01-01

    Phosphorus magic angle spinning nuclear magnetic resonance (NMR) spectra and transversal relaxation of M13 and TMV are analyzed by use of a model, which includes both local backbone motions of the encapsulated nucleic acid molecules and overall rotational diffusion of the rod-shaped virions about their length axis. Backbone motions influence the sideband intensities by causing a fast restricted reorientation of the phosphodiesters. To evaluate their influence on the observed sideband patterns, we extend the model that we used previously to analyze nonspinning 31P NMR lineshapes (Magusin, P.C.M.M., and M. A. Hemminga. 1993a. Biophys. J. 64:1861-1868) to magic angle spinning NMR experiments. Backbone motions also influence the conformation of the phosphodiesters, causing conformational averaging of the isotropic chemical shift, which offers a possible explanation for the various linewidths of the centerband and the sidebands observed for M13 gels under various conditions. The change of the experimental lineshape of M13 as a function of temperature and hydration is interpreted in terms of fast restricted fluctuation of the dihedral angles between the POC and the OCH planes on both sides of the 31P nucleus in the nucleic acid backbone. Backbone motions also seem to be the main cause of transversal relaxation measured at spinning rates of 4 kHz or higher. At spinning rates less than 2 kHz, transversal relaxation is significantly faster. This effect is assigned to slow, overall rotation of the rod-shaped M13 phage about its length axis. Equations are derived to simulate the observed dependence of T2e on the spinning rate. PMID:8038391

  2. Dipolar Assisted Assignment Protocol (DAAP) for MAS solid-state NMR of rotationally aligned membrane proteins in phospholipid bilayers

    NASA Astrophysics Data System (ADS)

    Das, Bibhuti B.; Zhang, Hua; Opella, Stanley J.

    2014-05-01

    A method for making resonance assignments in magic angle spinning solid-state NMR spectra of membrane proteins that utilizes the range of heteronuclear dipolar coupling frequencies in combination with conventional chemical shift based assignment methods is demonstrated. The Dipolar Assisted Assignment Protocol (DAAP) takes advantage of the rotational alignment of the membrane proteins in liquid crystalline phospholipid bilayers. Improved resolution is obtained by combining the magnetically inequivalent heteronuclear dipolar frequencies with isotropic chemical shift frequencies. Spectra with both dipolar and chemical shift frequency axes assist with resonance assignments. DAAP can be readily extended to three- and four-dimensional experiments and to include both backbone and side chain sites in proteins.

  3. Structural investigations of PuIII phosphate by X-ray diffraction, MAS-NMR and XANES spectroscopy

    NASA Astrophysics Data System (ADS)

    Popa, Karin; Raison, Philippe E.; Martel, Laura; Martin, Philippe M.; Prieur, Damien; Solari, Pier L.; Bouëxière, Daniel; Konings, Rudy J. M.; Somers, Joseph

    2015-10-01

    PuPO4 was prepared by a solid state reaction method and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. High resolution XANES measurements confirm the +III valence state of plutonium, in agreement with valence bond derivation. The presence of the americium (as β- decay product of plutonium) in the +III oxidation state was determined based on XANES spectroscopy. High resolution solid state 31P NMR agrees with the XANES results and the presence of a solid-solution.

  4. Solubilization and localization of weakly polar lipids in unsonicated egg phosphatidylcholine: A sup 13 C MAS NMR study

    SciTech Connect

    Hamilton, J.A. ); Fujito, D.T.; Hammer, C.F. )

    1991-03-19

    The weakly polar lipids cholesteryl ester, triacylglycerol, and diacylglycerol incorporate to a limited extent into the lamellar structure of small unilamellar vesicles. The localization of the carbonyl group(s) at the aqueous interface was detected by ({sup 13}C)carbonyl chemical shift changes relative to the neat unhydrated lipid. This study uses {sup 13}C NMR to investigate the interactions of thes lipids with unsonicated (multilamellar) phosphatidylcholine, a model system for cellular membranes and surfaces of emulsion particles with low curvature. Magic angle spinning reduced the broad lines of the unsonicated dispersions to narrow lines comparable to those from sonicated dispersions. ({sup 13}C)Carbonyl chemical shifts revealed incorporation of the three lipids into the lamellar structure of the unsonicated phospholipids and a partial hydration of the carbonyl groups similar to that observed in small vesicles. Other properties of interfacial weakly polar lipids in multilayers were similar to those in small unilamellar bilayers. There is thus a general tendency of weakly polar lipids to incorparate at least to a small extent into the lamellar structure of phospholipids and take on interfacial properties that are distinct from their bulk-phase properties. This pool of surface-located lipid is likely to be directly involved in enzymatyic transformations and protein-mediated transport. The {sup 13}C magic angle spinning NMR method may be generally useful for determining the orientation of molecules in model membranes.

  5. Structure of SiO[sub 2] on Al[sub 2]O[sub 3] monolayer catalysts: Investigation by infrared spectroscopy and [sup 29]Si MAS NMR

    SciTech Connect

    Sheng, T.C. ); Lang, S.; Morrow, B.A. ); Gay, I.D. )

    1994-07-01

    Infrared spectroscopy and [sup 29]Si MAS NMR are used to probe the structure of SiO[sub 2] on Al[sub 2]O[sub 3] catalysts prepared by chemical vapor deposition of Si(OCH[sub 3])[sub 4][center dot]SiO[sub 2] loadings from about 0.2-2.5 statistical monolayers are studied. Infrared shows a gradual disappearance of AlOH vibrations as the SiO[sub 2] loading is increased. A population of inaccessible AlOH is also observed. The Si-O-X asymmetric stretching frequency shows a continuous variation with SiO[sub 2] content, consistent with X varying from Al at low levels to Si at high levels of silica. [sup 29]Si NMR shows composite peaks at all SiO[sub 2] levels. At the lowest level most intensity is concentrated in the -80 to -85 ppm range, corresponding to Si with attached -OAl groups. At the highest silica levels, the spectrum can be deconvoluted into peaks at -108, -100, and -92 ppm. These correspond to Si(OSi)[sub 4], Si(OSi)[sub 3]OH, and mixtures of Si(OSi)[sub 2](OH)[sub 2] with -OAl-containing species. A model is proposed for build up of the silica layer on these catalysts. Random deposition of silica on any available surface is shown to give a semiquantitative account of the experimental results. 31 refs., 6 fig., 2 tabs.

  6. Analysis of mercerization process based on the intensity change of deconvoluted resonances of (13)C CP/MAS NMR: Cellulose mercerized under cooling and non-cooling conditions.

    PubMed

    Miura, Kento; Nakano, Takato

    2015-08-01

    The area intensity change of C1, C4, and C6 in spectrum obtained by (13)C CP/MAS NMR and the mutual relationship between their changes were examined for cellulose samples treated with various concentrations of aqueous NaOH solutions under non-cooling and cooling conditions. The area intensity of C1-up and C6-down changed cooperatively with that of C4-down which corresponds to the crystallinity of samples: "-up" and "-down" are the up- and down- field component in a splitting peak of NMR spectrum, respectively. The intensity change of C1-up starts to decrease with decreasing in that of C4-down after that of C6-down is almost complete. These changes were more clearly observed for samples treated under cooling condition. It can be suggested that their characteristic change relates closely to the change in conformation of cellulose chains by induced decrystallization and the subsequent crystallization of cellulose II, and presumed that their changes at microscopic level relate to the macroscopic morphological changes such as contraction along the length of cellulose chains and recovery along the length. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Investigation of the Structure and Active Sites of TiO2 Nanorod Supported VOx Catalysts by High-Field and Fast-Spinning 51V MAS NMR

    SciTech Connect

    Hu, Jian Z.; Xu, Suochang; Li, Weizhen; Hu, Mary Y.; Deng, Xuchu; Dixon, David A.; Vasiliu, Monica; Craciun, Raluca; Wang, Yong; Bao, Xinhe; Peden, Charles HF

    2015-07-02

    Supported VOx/TiO2-Rod catalysts were studied by 51V MAS NMR at high field using a sample spinning rate of 55 kHz. The superior spectral resolution allows for the observation of at least five vanadate species. The assignment of these vanadate species was carried out by quantum mechanical calculations of 51V NMR chemical shifts of model V-surface structures. Methanol oxidative dehydrogenation (ODH) was used to establish the correlation between the reaction rate and the various surface V-sites. It is found that monomeric V-species dominated the catalyst at low vanadium loadings with two peaks observed at about -502 and -529 ppm. V-dimers with two bridged oxygen appeare at about -555 ppm. Vanadate dimers and polyvanadates connected by one bridged oxygen atom between two adjacent V atoms resonate at about -630 ppm. A positive correlation is found between the V-dimers related to the -555 ppm peak and the ODH rate while a better correlation is obtained by including monomeric contributions. This result indicates that surface V-dimers related to the -555 ppm peak are the major active sites for ODH reaction despite mono-V species are more catalytic active but their relative ratios are decreased dramatically at high V-loadings. Furthermore, a portion of the V-species is found invisible. In particular, the level of such invisibility increases with decreased level of V-loading, suggesting the existence of paramagnetic V-species at the surface.

  8. Al speciation in tropical podzols of the upper Amazon Basin: A solid-state 27Al MAS and MQMAS NMR study

    NASA Astrophysics Data System (ADS)

    Bardy, Marion; Bonhomme, Christian; Fritsch, Emmanuel; Maquet, Jocelyne; Hajjar, Redouane; Allard, Thierry; Derenne, Sylvie; Calas, Georges

    2007-07-01

    In the upper Amazon Basin, aluminum previously accumulated in lateritic formations is massively remobilised in soils by podzolization and exported in waters. We have investigated the speciation of aluminum in the clay-size fractions of eight horizons of waterlogged podzols lying in a depression of a plateau. The horizons illustrate the main steps involved in the podzolization of laterites. They belong to eluviated topsoil A horizons and illuviated subsoil Bhs, Bh and 2BCs horizons of weakly and better-expressed podzols located at the margin and centre of the depression. For the first time, aluminum speciation is quantitatively assessed in soils by spectroscopic methods, namely FTIR, 27Al magic angle spinning (MAS) and multiple-quantum magic angle spinning (MQMAS), nuclear magnetic resonance (NMR). The results thus obtained are compared to chemical extraction data. Solid-state 27Al MAS NMR spectra enable to distinguish Al bound to organic compounds from that incorporated in secondary mineral phases detected by FTIR. MQMAS experiments additionally show that both chemical shifts and quadrupolar constants are distributed for Al nuclei linked with organic compounds. Similar amounts of chelated Al are obtained from NMR spectra and chemical extractions. The study enables to highlight three major steps in the fate of aluminum. (i) Aluminum is first released by mineral weathering, feeds complexing sites of organic matter and accumulates in subsurface Bhs horizons of weakly expressed podzols (acidocomplexolysis). (ii) Complexes of aluminum with organic matter (Al-OM) then migrate downwards in sandy horizons of better-expressed podzols and accumulate at depth in less permeable 2BCs horizons. (iii) The minor amounts of aluminum present in the 2BCs horizon of the downslope podzol show that aluminum is eventually exported towards the river network, either complexed with organic matter or as Al 3+ ions after desorption from organic compounds, due to decreasing pH or

  9. Time dependency of metabolic changes in rat lens after in vivo UVB irradiation analysed by HR-MAS 1H NMR spectroscopy.

    PubMed

    Risa, Oystein; Saether, Oddbjørn; Kakar, Manoj; Mody, Vino; Löfgren, Stefan; Söderberg, Per G; Krane, Jostein; Midelfart, Anna

    2005-10-01

    The lens ability to protect against, and repair ultraviolet radiation (UVR) induced damages, is of crucial importance to avoid cataract development. The influence of UVR-induced damage and repair processes on the lens metabolites are not fully understood. Observation of short- and long-term changes in light scattering and the metabolic profile of pigmented rat lenses after threshold UVR exposure might serve to better understand the protective mechanisms in the lens. By using high resolution magic angle spinning (HR-MAS) 1H NMR spectroscopy it was possible to investigate the metabolites of intact rat lenses. Brown-Norway rats were exposed to 15 kJm(-2) UVB irradiation. One eye was exposed and the contralateral served as control. The rats were sacrificed 5, 25, 125, and 625 hr post-exposure and the lenses were removed. The degree of cataract was quantified by measurement of lens forward light scattering. Thereafter, proton NMR spectra from intact lenses were obtained and relative changes in metabolite concentrations were determined. The light scattering in the lens peaked at 25 hr post-exposure and decreased thereafter. The lowest level of light scattering was measured 625 hr after exposure. No significant changes in concentration were observed for the metabolites 5 and 25 hr post-exposure except the total amount of adenosine tri- and diphosphate (ATP/ADP) that showed a significant decrease already 5 hr after exposure. At 125 hr the lens concentrations of lactate, succinate, phospho-choline, taurine, betaine, myo-inositol, and ATP/ADP showed a significant decrease (p<0.05). Phenylalanine was the only metabolite that revealed a significant increase 125 hr post-exposure. At 625 hr most of the metabolic changes seemed to normalise back to control levels. However, the concentration of betaine and phospho-choline were still showing a significant decrease 625 hr after UVB irradiation. The impact of UVB irradiation on the metabolic profile did not follow the same time

  10. Atomic structure and dehydration mechanism of amorphous silica: Insights from 29Si and 1H solid-state MAS NMR study of SiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Na; Lee, Sung Keun

    2013-11-01

    Detailed knowledge of the atomic structure of hydrous species on surface of amorphous silica and the effect of temperature and particle size on their atomic configurations are essential to understand the nature of fluids-amorphous silicates interactions and the dehydration processes in the amorphous oxides. Here, we report the 29Si, 1H MAS, and 1H-29Si heteronuclear correlation (HetCor) NMR spectra of 7 nm and 14 nm amorphous silica nanoparticles—a model system for natural amorphous silica—where previously unknown details of changes in their atomic structures with varying dehydration temperature and particle size are revealed. Diverse hydroxyl groups with varying atomic configurations and molecular water apparently show distinct dehydration trends. The dehydration (i.e., removal of water) of amorphous silica nanoparticles mostly results in the increase of isolated silanol by removing water molecules from hydrogen-bonded silanols associated water molecules. With further increase in dehydration temperature, the intensity of isolated silanol peak decreases above ˜873 K, suggesting that the condensation of isolated silanol may occur mainly above ˜873 K. The entire dehydration (and dehydroxylation) process completes at ˜1473 K. Both the water (i.e., physisorbed water and hydrogen-bonded water) and hydrogen-bonded silanol species show a dramatic change in the slope of intensity variation at ˜873 K, indicating that most of silanols is hydrogen-bonded to water rather than to other silanols. The fraction of hydrogen-bonded proton species is also much smaller in 14 nm amorphous silica nanoparticles than in 7 nm amorphous silica nanoparticles mainly due to the presences of larger fractions of water and hydrogen-bonded silanol species. 29Si NMR results show that with increasing dehydration temperature, the fraction of Q4 species apparently increases at the expense of Q2 and Q3 species. The fractions of Q2 and Q3 structures in 7 nm amorphous silica nanoparticles are

  11. Proton-detected MAS NMR experiments based on dipolar transfers for backbone assignment of highly deuterated proteins

    NASA Astrophysics Data System (ADS)

    Chevelkov, Veniamin; Habenstein, Birgit; Loquet, Antoine; Giller, Karin; Becker, Stefan; Lange, Adam

    2014-05-01

    Proton-detected solid-state NMR was applied to a highly deuterated insoluble, non-crystalline biological assembly, the Salmonella typhimurium type iii secretion system (T3SS) needle. Spectra of very high resolution and sensitivity were obtained at a low protonation level of 10-20% at exchangeable amide positions. We developed efficient experimental protocols for resonance assignment tailored for this system and the employed experimental conditions. Using exclusively dipolar-based interspin magnetization transfers, we recorded two sets of 3D spectra allowing for an almost complete backbone resonance assignment of the needle subunit PrgI. The additional information provided by the well-resolved proton dimension revealed the presence of two sets of resonances in the N-terminal helix of PrgI, while in previous studies employing 13C detection only a single set of resonances was observed.

  12. Hybridizing cross-polarization with NOE or refocused-INEPT enhances the sensitivity of MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Mroue, Kamal H.; Ramamoorthy, Ayyalusamy

    2016-05-01

    Heteronuclear cross polarization (CP) has been commonly used to enhance the sensitivity of dilute low-γ nuclei in almost all solid-state NMR experiments. However, CP relies on heteronuclear dipolar couplings, and therefore the magnetization transfer efficiency becomes inefficient when the dipolar couplings are weak, as is often the case for mobile components in solids. Here, we demonstrate methods that combine CP with heteronuclear Overhauser effect (referred to as CP-NOE) or with refocused-INEPT (referred to as CP-RINEPT) to overcome the efficiency limitation of CP and enhance the signal-to-noise ratio (S/N) for mobile components. Our experimental results reveal that, compared to the conventional CP, significant S/N ratio enhancement can be achieved for resonances originating from mobile components, whereas the resonance signals associated with rigid groups are not significantly affected due to their long spin-lattice relaxation times. In fact, the S/N enhancement factor is also dependent on the temperature, CP contact time as well as on the system under investigation. Furthermore, we also demonstrate that CP-RINEPT experiment can be successfully employed to independently detect mobile and rigid signals in a single experiment without affecting the data collection time. However, the resolution of CP spectrum obtained from the CP-RINEPT experiment could be slightly compromised by the mandatory use of continuous wave (CW) decoupling during the acquisition of signals from rigid components. In addition, CP-RINEPT experiment can be used for spectral editing utilizing the difference in dynamics of different regions of a molecule and/or different components present in the sample, and could also be useful for the assignment of resonances from mobile components in poorly resolved spectra. Therefore, we believe that the proposed approaches are beneficial for the structural characterization of multiphase and heterogeneous systems, and could be used as a building block in

  13. (Na{sub 4}BH{sub 4}){sup 3+} guests inside aluminosilicate, gallosilicate and aluminogermanate sodalite host frameworks studied by {sup 1}H, {sup 11}B, and {sup 23}Na MAS NMR spectroscopy

    SciTech Connect

    Buhl, J.-Ch.; Murshed, M.M.

    2009-07-01

    We report tetrahydroborate aluminosilicate, gallosilicate and aluminogermanate sodalites studied by {sup 11}B, {sup 1}H and {sup 23}Na MAS NMR spectroscopy. The spectral parameters are consistent with the local environments of each investigated nucleus obtained from the crystal structures. The {sup 11}B MAS NMR spectra exhibit a sharp narrow line at about -49.0 ppm, which is assigned to BH{sub 4}{sup -} enclathrated into the sodalite framework matrix. The lineshape of the signal shows no quadrupolar interactions due to discreteness and high symmetry of the BH{sub 4}{sup -} unit as well as possible fast dynamic site exchange of hydrogen atoms. The {sup 23}Na MAS NMR signals also show a narrow Gaussian lineshape, which clearly indicates a single type of sodium coordination, and a centrosymmetrical charge distribution around the sodium atom. The {sup 1}H MAS NMR spectra can clearly distinguish between hydrogen in BH{sub 4}{sup -} anions (-0.6 ppm), H{sub 3}O{sub 2}{sup -} anions (1.2 ppm) and H{sub 2}O molecules (5.0 ppm). The structural properties of BH{sub 4}{sup -} intercalation into sodalite framework matrix help connect the microporous materials to hydride-containing A, X and Y type zeolites.

  14. 87Rb spin-lattice relaxation times in ferroelectric-paraelectric-incommensurate phases of Rb2CoBr4 using static NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2017-04-01

    To better elucidate the structural properties of Rb2CoBr4 in paraelectric, incommensurate, and ferroelectric phases, we studied the 87Rb nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times in laboratory frame T1 and in rotating frame T1ρ. The resonance frequency and the chemical shift do not change abruptly near the phase transition temperature of Ti = 333 K and TC = 192 K, whereas T1 and T1ρ display discontinuous changes near Ti and TC. The abrupt changes in the relaxation times near these temperatures seem to be a result of the structural phase transitions. The results are distinctly different from those reported for Rb2CoCl4.

  15. Double quantum dots defined in bilayer graphene

    NASA Astrophysics Data System (ADS)

    Żebrowski, D. P.; Peeters, F. M.; Szafran, B.

    2017-07-01

    Artificial molecular states of double quantum dots defined in bilayer graphene are studied with the atomistic tight-binding method and its low-energy continuum approximation. We indicate that the extended electron wave functions have opposite parities on sublattices of the layers and that the ground-state wave-function components change from bonding to antibonding with the interdot distance. In the weak-coupling limit, the one most relevant for quantum dots defined electrostatically, the signatures of the interdot coupling include, for the two-electron ground state, formation of states with symmetric or antisymmetric spatial wave functions split by the exchange energy. In the high-energy part of the spectrum the states with both electrons in the same dot are found with the splitting of energy levels corresponding to simultaneous tunneling of the electron pair from one dot to the other.

  16. The role of water in the degradation process of paper using (1)H HR-MAS NMR spectroscopy.

    PubMed

    Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Pietronero, Luciano; Mallamace, Francesco; Missori, Mauro

    2016-12-07

    The thermodynamic properties of water are essential for determining the corresponding properties of every biosystem it interacts with. Indeed, the comprehension of hydration mechanisms is fundamental for the understanding and the control of paper degradation pathways induced by natural or artificial aging. In fact, the interactions between water and cellulose at the accessible sites within the fibres' complex structure are responsible for the rupture of hydrogen bonds and the consequent swelling of the cellulose fibres and consumption of the amorphous regions. In this paper we study the hydration process of cellulose in naturally and artificially aged paper samples by measuring the proton spin-lattice (T1) and spin-spin (T2) relaxation times of the macroscopic magnetization through nuclear magnetic resonance (NMR) experiments. The observed behaviour of T1 and T2 is quite complex and strictly dependent on the water content of paper samples. This has been interpreted as due to the occurrence of different mechanisms regulating the water-cellulose interaction within the fibres. Furthermore, we have measured T1 as a function of the artificial aging time comparing the results with those measured on three paper samples dated back to the 15th century. We found that the evolution of T1 in model papers artificially aged is correlated with that of ancient paper, providing therefore a way for estimating the degradation of cellulosic materials in terms of an equivalent time of artificial aging. These results provide fundamental information for industrial applications and for the preservation and restoration of cultural heritage materials based on cellulose such as ancient paper or textiles.

  17. 31P MAS-NMR study of flux-grown rare-earth element orthophosphate (monazite/xenotime) solid solutions: Evidence of random cation distribution from paramagnetically shifted NMR resonances

    SciTech Connect

    Palke, A. C.; Stebbins, J. F.; Boatner, Lynn A

    2013-01-01

    We present 31P magic angle spinning nuclear magnetic resonance (MAS-NMR) spectra of flux-grown solid solutions of La1-xCexPO4 ( x between 0.027 and 0.32) having the monoclinic monazite structure, and of Y1-xMxPO4 (M = Vn+, Ce3+, Nd3+, x between 0.001 and 0.014) having the tetragonal zircon structure. Paramagnetically shifted NMR resonances are observed in all samples due to the presence of paramagnetic Vn+, Ce3+, and Nd3+ in the diamagnetic LaPO4 or YPO4. As a first-order observation, the number and relative intensity of these peaks is related to the symmetry and structure of the diamagnetic host phase. The presence of paramagnetic shifts allows for increased resolution between NMR resonances for distinct atomic species which leads to the observation of low intensity peaks related to PO4 species having more than one paramagnetic neighbor two or four atomic bonds away. Through careful analysis of peak areas and comparison with predictions for simple models, it was determined that solid solutions in the systems examined here are characterized by complete disorder (random distribution) of diamagnetic La3+ or Y3+ with the paramagnetic substitutional species Ce3+ and Nd3+. The increased resolution given by the paramagnetic interactions also leads to the observation of splitting of specific resonances in the 31P NMR spectra that may be caused by local, small-scale distortions from the substitution of ions having dissimilar ionic radii.

  18. In situ (1)H and (13)C MAS NMR kinetic study of the mechanism of H/D exchange for propane on zeolite H-ZSM-5.

    PubMed

    Arzumanov, Sergei S; Reshetnikov, Sergei I; Stepanov, Alexander G; Parmon, Valentin N; Freude, Dieter

    2005-10-27

    The kinetics of hydrogen (H/D) exchange between Brønsted acid sites of zeolite H-ZSM-5 and variously deuterated propanes (propane-d(8), propane-1,1,1,3,3,3-d(6), propane-2,2-d(2)) have been monitored in situ by (1)H MAS NMR spectroscopy within the temperature range of 503-556 K. The contribution of intramolecular hydrogen transfer to the H/D exchange in the adsorbed propane was estimated by monitoring the kinetics of (13)C-labeled carbon scrambling in propane-2-(13)C in situ with (13)C MAS NMR at 543-573 K. Possible mechanisms of the exchange have been verified on the basis of the analysis of the variation of protium concentration in both the methyl and the methylene groups of propane in dependence of the reaction time. The main route of the exchange consists of a direct exchange of the acidic OH groups of the zeolite with either the methyl groups or the methylene group presumably with a pentacoordinated carbonium ion intermediate. The assumption that the intramolecular H scrambling between the methyl groups and the methylene group of propane via carbenium-ion-type intermediates is the fastest process among the other possible routes does not account for the experimental kinetics of H/D exchange for propanes with different initial contents and locations of deuterium in a propane molecule. The rate constant (k(3)) for intramolecular H/D exchange between the methyl and the methylene groups is 4-5 times lower compared to those of the direct exchange of both the methyl (k(1)) and the methylene (k(2)) groups with Brønsted acid sites of the zeolite, the k(1) being ca. 1.5 times higher than k(2). At lower temperature (473 K), the exchange is slower, and the expected difference between k(1) and k(2) is more essential, k(1) = 3k(2). This accounts for earlier observed regioselectivity of the exchange for propane on H-ZSM-5 at 473 K. Faster direct exchange with the methyl groups compared to that with the methylene groups was attributed to a possible, more spatial

  19. Glass Structure by Scattering Methods and Spectroscopy — D. SOLID STATE NMR AS A STRUCTURAL TOOL IN GLASS SCIENCE

    NASA Astrophysics Data System (ADS)

    Eckert, Hellmut

    The following sections are included: * Introduction * Fundamentals of Solid State NMR * Nuclear magnetism and resonance * Spectroscopic technique * Internal interactions * Chemical shielding interaction * Direct magnetic dipole-dipole coupling * Nuclear electric quadrupolar interaction * Experimental separation strategies * Magic-angle spinning * Multi-dimensional NMR * Structural Issues in Non-crystalline Solids and Glasses * Short-Range Order in Oxide Glasses * Local coordination number and symmetry * Bond angle distribution functions * Spatial distribution of modifier cations and structural implications of the mixed-alkali effect * Short-Range Order in Non-Oxide Glasses * Chemical bond distribution and intermediate range order * Chemical equilibria and kinetics in glassforming liquids * Future Perspectives * Towards higher resolution for quadrupolar nuclei * Recovery of dipolar interactions in MAS-NMR: site connectivities * Double resonance NMR in heteronuclear systems * Zero- and double quantum NMR in homonuclear systems * Acknowledgments * References

  20. Effect of organic matter application on CP-MAS-13C-NMR spectra of humic acids from a brown soil

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    The humified SOM or humic substances (HS) composed of humic acid (HA), fulvic acid (FA) and humin (HM) represent the most microbially recalcitrant and stable reservoir of organic carbon in soil (Piccolo et al., 2004). OM applications can influence the amount and structural characteristics of HS(Dou et al., 2008). During the past few decades, there has been much research on HS, but their chemical structure is still not fully understood (Dong, 2006).CP-MAS-13C-NMR spectroscopy was considered as an effective method to study structures of HS without dissolving problem compared with liquid 13C-NMR (Conte et al., 1997; Dou et al., 2008). It can directly measure the carbon framework and reflect the nature of HS transformation after OM application (Spaccini et al., 2000). For that reason, this method was applied in this study. The objective of this paper was to clarify the effect of long term OM application on the changes of structural characteristics in HAs, which provided new information for improving soil fertility by OM application. The experiment was carried out on a brown soil (Paleudalf in USDA Soil Taxonomy) at Shenyang Agricultural University, Liaoning province, China (N41°48'-E123°25'). The experiment included 3 treatments: zero-treatment (CKbr), and two pig manure (PM) treatments (O1 and O2) at the rates of 0.9 t ha-1 and 1.8 t ha-1 of organic carbon, respectively. The samples of the HA fraction were extracted, separated and purified according to the method described by Dou et al. (1991). Elemental composition, Differential thermal analysis (DTA), -lgK value, FT-IR and CP-MAS- 13C-NMR of HAs were performed. Effects on the contents of orgaic carbon and its composition. The contents of TOC were from 8.77 g kg-1 to 12.25 g kg-1. The relative contents in TOC for WSS, HA, and FA were 6.87%, 14.2% and 19.8%. Comparing the CKbr, the contents of WSS, HA and FA for O1 and O2 increased, but relative contents of WSS and FA decreased. The content of the HA increased after

  1. Drug release from cast films of ethylene vinyl acetate (EVA) copolymer: Stability of drugs by 1H NMR and solid state 13C CP/MAS NMR.

    PubMed

    Kalachandra, S; Lin, D M; Stejskal, E O; Prakki, A; Offenbacher, S

    2005-07-01

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate copolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of polymer casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation (E*) were calculated using Arrhenius plots. Effect of EVA copolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the polymer. The highest E* observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film casting process.

  2. Fast MAS 1H NMR Study of Water Adsorption and Dissociation on the (100) Surface of Ceria Nanocubes: A Fully Hydroxylated, Hydrophobic Ceria Surface

    DOE PAGES

    Gill, Lance; Beste, Ariana; Chen, Banghao; ...

    2017-03-22

    1H nuclear magnetic resonance (NMR) spectroscopy was used to study hydroxylic surface species on ceria nanocubes, a crystalline, high-surface-area CeO2 that presents mostly (100) facets. Water adsorption and desorption experiments in combination with fast magic angle spinning (MAS, 20–40 kHz) 1H NMR provide high-resolution 1H spectra that allow the observation of ten resonance bands (water or hydroxyl) on or under the (100) surface. Assignments were made using a combination of adsorption and temperature-programmed desorption, quantitative spin counting, deuterium exchange, spin–lattice (T1) and spin–spin (T2) relaxation, and DFT calculations. In air, the (100) surface exists as a fully hydroxylated surface. Watermore » adsorption and dissociation on dry ceria surfaces occur first at oxygen vacancies, but Ce3+ centers are not required since water dissociation is barrier-less on the fully oxidized surface. Surface $-$OH functionality occurs in two resolved bands representing isolated $-$OH (1 ppm) and hydrogen-bonded $-$OH (9 ppm), the latter being dominant. Deuterium exchange of surface hydroxyls with D2O does not occur under mild or forcing conditions. Despite large differences in the T1 of surface hydroxyls and physisorbed water, surface hydroxyl T1 values are independent of the presence or absence of physisorbed water, demonstrating that the protons within these two functional group pools are not in intimate contact. These observations show that, once hydroxylated, the surface $-$OH functionality preferentially forms hydrogen bonds with surface lattice oxygen, i.e., the hydroxylated (100) surface of ceria is hydrophobic. Near this surface it is energetically more favorable for physisorbed water to hydrogen bond to itself rather than to the surface. DFT calculations support this notion. Impurity Na+ remaining in incompletely washed ceria nanocubes increases the surface hydrophilicity. In conclusion, sharp, low-field resonances observed in spectra of

  3. 1H HR-MAS NMR Based Metabolic Profiling of Cells in Response to Treatment with a Hexacationic Ruthenium Metallaprism as Potential Anticancer Drug

    PubMed Central

    Vermathen, Martina; Paul, Lydia E. H.; Diserens, Gaëlle

    2015-01-01

    1H high resolution magic angle spinning (HR-MAS) NMR spectroscopy was applied in combination with multivariate statistical analyses to study the metabolic response of whole cells to the treatment with a hexacationic ruthenium metallaprism [1]6+ as potential anticancer drug. Human ovarian cancer cells (A2780), the corresponding cisplatin resistant cells (A2780cisR), and human embryonic kidney cells (HEK-293) were each incubated for 24 h and 72 h with [1]6+ and compared to untreated cells. Different responses were obtained depending on the cell type and incubation time. Most pronounced changes were found for lipids, choline containing compounds, glutamate and glutathione, nucleotide sugars, lactate, and some amino acids. Possible contributions of these metabolites to physiologic processes are discussed. The time-dependent metabolic response patterns suggest that A2780 cells on one hand and HEK-293 cells and A2780cisR cells on the other hand may follow different cell death pathways and exist in different temporal stages thereof. PMID:26024484

  4. Effects of solvent concentration and composition on protein dynamics: 13C MAS NMR studies of elastin in glycerol-water mixtures.

    PubMed

    Demuth, Dominik; Haase, Nils; Malzacher, Daniel; Vogel, Michael

    2015-08-01

    We use (13)C CP MAS NMR to investigate the dependence of elastin dynamics on the concentration and composition of the solvent at various temperatures. For elastin in pure glycerol, line-shape analysis shows that larger-scale fluctuations of the protein backbone require a minimum glycerol concentration of ~0.6 g/g at ambient temperature, while smaller-scale fluctuations are activated at lower solvation levels of ~0.2 g/g. Immersing elastin in various glycerol-water mixtures, we observe at room temperature that the protein mobility is higher for lower glycerol fractions in the solvent and, thus, lower solvent viscosity. When decreasing the temperature, the elastin spectra approach the line shape for the rigid protein at 245 K for all studied samples, indicating that the protein ceases to be mobile on the experimental time scale of ~10(-5) s. Our findings yield evidence for a strong coupling between elastin fluctuations and solvent dynamics and, hence, such interaction is not restricted to the case of protein-water mixtures. Spectral resolution of different carbon species reveals that the protein-solvent couplings can, however, be different for side chain and backbone units. We discuss these results against the background of the slaving model for protein dynamics.

  5. Solid-state MAS NMR, TEM, and TGA studies of structural hydroxyl groups and water in nanocrystalline apatites prepared by dry milling.

    PubMed

    Pajchel, Lukasz; Kolodziejski, Waclaw

    2013-01-01

    A series of nanocrystalline calcium hydroxyapatites was prepared by dry milling and characterized using proton and (31)P MAS NMR, TEM, and TGA methods. The samples contained stubby rod-shaped crystals, which length and width varied in the 130-30 and 95-20 nm ranges, respectively. It was confirmed that concentration of structural hydroxyl groups in nanocrystalline apatites decreases with the decreasing crystal size. In the series of the studied apatites, the decrease was from 86 to ca. 50 % in reference to stoichiometric apatite. Water was found in the surface hydrated layer and in the c-axis channels, in which compartments existed as adsorbed and structural, respectively. Molecules of the adsorbed water were capable of moving from the crystal surface into the lattice c-axis channels of apatite. This process introduced considerable structural disorder within and around those channels and reduced the content of the structural hydroxyl groups, particularly in the region underneath the apatite crystal surface.

  6. A sequential assignment procedure for proteins that have intermediate line widths in MAS NMR spectra: amyloid fibrils of human CA150.WW2.

    PubMed

    Becker, Johanna; Ferguson, Neil; Flinders, Jeremy; van Rossum, Barth-Jan; Fersht, Alan R; Oschkinat, Hartmut

    2008-08-11

    The second WW domain (WW2) of CA150, a human transcriptional activator, forms amyloid fibrils in vitro under physiological conditions. Based on experimental constraints from MAS NMR spectroscopy experiments, alanine scanning and electron microscopy, a structural model of CA150.WW2 amyloid fibrils was calculated earlier. Here, the assignment strategy is presented and suggested as a general approach for proteins that show intermediate line width. The (13)C,(13)C correlation experiments were recorded on fully or partially (13)C-labelled fibrils. The earlier (13)C assignment (26 residues) was extended to 34 of the 40 residues by direct (13)C-excitation experiments by using a deuterated sample that showed strongly improved line width. A 3D HNC-TEDOR (transferred-echo double-resonance) experiment with deuterated CA150.WW2 fibrils yielded 14 amide nitrogen and proton resonance assignments. The obtained chemical shifts were compared with the chemical shifts determined with the natively folded WW domain. TALOS (Torsion angle likelihood obtained from shift and sequence similarity) predictions confirmed that, under physiological conditions, the fibrillar form of CA150.WW2 adopts a significantly different beta structure than the native WW-domain fold.

  7. Amino-acid selective experiments on uniformly 13C and 15N labeled proteins by MAS NMR: Filtering of lysines and arginines.

    PubMed

    Jehle, Stefan; Rehbein, Kristina; Diehl, Anne; van Rossum, Barth-Jan

    2006-12-01

    Amino-acid selective magic-angle spinning (MAS) NMR experiments can aid the assignment of ambiguous cross-peaks in crowded spectra of solid proteins. In particular for larger proteins, data analysis can be hindered by severe resonance overlap. In such cases, filtering techniques may provide a good alternative to site-specific spin-labeling to obtain unambiguous assignments that can serve as starting points in the assignment procedure. In this paper we present a simple pulse sequence that allows selective excitation of arginine and lysine residues. To achieve this, we make use of a combination of specific cross-polarization for selective excitation [M. Baldus, A.T. Petkova, J. Herzfeld, R.G. Griffin, Cross polarization in the tilted frame: assignment and spectral simplification in heteronuclear spin systems, Mol. Phys. 95 (1998) 1197-1207.] and spin diffusion for transfer along the amino-acid side-chain. The selectivity of the filter is demonstrated with the excitation of lysine and arginine side-chain resonances in a uniformly 13C and 15N labeled protein preparation of the alpha-spectrin SH3 domain. It is shown that the filter can be applied as a building block in a 13C-13C lysine-only correlation experiment.

  8. Analysis of local molecular motions of aromatic sidechains in proteins by 2D and 3D fast MAS NMR spectroscopy and quantum mechanical calculations.

    PubMed

    Paluch, Piotr; Pawlak, Tomasz; Jeziorna, Agata; Trébosc, Julien; Hou, Guangjin; Vega, Alexander J; Amoureux, Jean-Paul; Dracinsky, Martin; Polenova, Tatyana; Potrzebowski, Marek J

    2015-11-21

    We report a new multidimensional magic angle spinning NMR methodology, which provides an accurate and detailed probe of molecular motions occurring on timescales of nano- to microseconds, in sidechains of proteins. The approach is based on a 3D CPVC-RFDR correlation experiment recorded under fast MAS conditions (ν(R) = 62 kHz), where (13)C-(1)H CPVC dipolar lineshapes are recorded in a chemical shift resolved manner. The power of the technique is demonstrated in model tripeptide Tyr-(d)Ala-Phe and two nanocrystalline proteins, GB1 and LC8. We demonstrate that, through numerical simulations of dipolar lineshapes of aromatic sidechains, their detailed dynamic profile, i.e., the motional modes, is obtained. In GB1 and LC8 the results unequivocally indicate that a number of aromatic residues are dynamic, and using quantum mechanical calculations, we correlate the molecular motions of aromatic groups to their local environment in the crystal lattice. The approach presented here is general and can be readily extended to other biological systems.

  9. A (1)H HR-MAS NMR-Based Metabolomic Study for Metabolic Characterization of Rice Grain from Various Oryza sativa L. Cultivars.

    PubMed

    Song, Eun-Hye; Kim, Hyun-Ju; Jeong, Jaesik; Chung, Hyun-Jung; Kim, Han-Yong; Bang, Eunjung; Hong, Young-Shick

    2016-04-20

    Rice grain metabolites are important for better understanding of the plant physiology of various rice cultivars and thus for developing rice cultivars aimed at providing diverse processed products. However, the variation of global metabolites in rice grains has rarely been explored. Here, we report the identification of intra- or intercellular metabolites in rice (Oryza sativa L.) grain powder using a (1)H high-resolution magic angle spinning (HR-MAS) NMR-based metabolomic approach. Compared with nonwaxy rice cultivars, marked accumulation of lipid metabolites such as fatty acids, phospholipids, and glycerophosphocholine in the grains of waxy rice cultivars demonstrated the distinct metabolic regulation and adaptation of each cultivar for effective growth during future germination, which may be reflected by high levels of glutamate, aspartate, asparagine, alanine, and sucrose. Therefore, this study provides important insights into the metabolic variations of diverse rice cultivars and their associations with environmental conditions and genetic backgrounds, with the aim of facilitating efficient development and the improvement of rice grain quality through inbreeding with genetic or chemical modification and mutation.

  10. Solid state {sup 31}P MAS NMR spectroscopy and conductivity measurements on NbOPO{sub 4} and H{sub 3}PO{sub 4} composite materials

    SciTech Connect

    Risskov Sørensen, Daniel; Nielsen, Ulla Gro; Skou, Eivind M.

    2014-11-15

    A systematic study of composite powders of niobium oxide phosphate (NbOPO{sub 4}) and phosphoric acid (H{sub 3}PO{sub 4}) has been performed in order to characterize the material's ability to perform as an electrolyte material in medium temperature fuel cells and electrolyzers. Powders of H{sub 3}PO{sub 4} contents between 13.1 and 74.2 M% were produced and characterized with powder X-ray diffraction, {sup 31}P MAS NMR and impedance spectroscopy. NMR revealed that a significant degree of dehydration and vaporization of H{sub 3}PO{sub 4} takes place above 200 °C, and increases with temperature. At 500 °C the NbOPO{sub 4} and H{sub 3}PO{sub 4} has reacted to form niobium pyrophosphate (Nb{sub 2}P{sub 4}O{sub 15}). Impedance spectroscopy showed an increase in conductivity with increasing acid concentration, whereas the conductivity decreased slightly with increasing temperature. The highest conductivity measured was 2.5·10{sup −3} S/cm for a sample containing 74.2 M% of H{sub 3}PO{sub 4}. Lastly, it was shown that NbOPO{sub 4} has no significant conductivity of its own. - Graphical abstract: Conductivity of NbOPO{sub 4}/H{sub 3}PO{sub 4} composites as a function of equivalent P{sub 2}O{sub 5} content. The conductivity is insignificant for pure NbOPO{sub 4}. - Highlights: • Composites have been made from NbOPO{sub 4} and H{sub 3}PO{sub 4}. • The composites composition has been investigated with solid state NMR. • The composites have shown clear signs of acid dehydration upon heating. • The conductivity of the composites increases for increasing acid content. • NbOPO{sub 4} has no significant conductivity of its own.

  11. I: Low Frequency NMR and NQR Using a dc SQUID. II: Variable-temperature 13C CP/MAS of Organometallics

    SciTech Connect

    Ziegeweid, Marcia A.

    1995-11-01

    NMR and NQR at low frequencies are difficult prospects due to small nuclear spin polarization. Furthermore, the sensitivity of the inductive pickup circuitry of standard spectrometers is reduced as the frequency is lowered. I have used a cw-SQUID (Superconducting Quantum Interference Device) spectrometer, which has no such frequency dependence, to study the local atomic environment of 14N via the quadrupolar interaction. Because 14N has spin I = 1 and a 0-6 MHz frequency range, it is not possible to obtain well-resolved spectra in high magnetic fields. I have used a technique to observe 14N NQR resonances via their effect on neighboring protons mediated by the heteronuclear dipolar interaction to study peptides and narcotics. The sensitivity of the SQUID is not enough to measure low-frequency surface (or other low spin density) systems. The application of spin-polarized xenon has been previously used to enhance polarization in conventional NMR experiments. Because xenon only polarizes spins with which it is in contact, it is surface selective. While differences in chemical shifts between surface and bulk spins are not large, it is expected that the differences in quadrupole coupling constant should be very large due to the drastic change of the electric field gradient surrounding spins at the surface. With this in mind, I have taken preliminary steps to measure SQUID detected polarization transfer from Xe to another spin species at 4.2 K and in small magnetic fields (<50 G). In this regime, the spin-lattice relaxation of xenon is dependent on the applied magnetic field. The results of our efforts to characterize the relaxation of xenon are presented. The final section describes the solid-state variable-temperature (VT) one- and two-dimensional 13C cross polarization (CP)/magic angle spinning (MAS) NMR of Hf(η5-C5H5)21-C5H5)2, Zr

  12. Al coordination and water speciation in hydrous aluminosilicate glasses: direct evidence from high-resolution heteronuclear 1H-27Al correlation NMR.

    PubMed

    Xue, Xianyu; Kanzaki, Masami

    2007-02-01

    In order to shed light on the dissolution mechanisms of water in depolymerized aluminosilicate melts/glasses, a comprehensive one- (1D) and two-dimensional (2D) NMR study has been carried out on hydrous Ca- and Mg-aluminosilicate glasses of a haplobasaltic composition. The applied techniques include 1D 1H MAS NMR and 27Al-->1H cross-polarization (CP) MAS NMR, and 2D 1H NOESY and double-quantum (DQ) MAS NMR, 27Al triple-quantum (3Q) MAS NMR and 27Al-->1H heteronuclear correlation (HETCOR) and 3QMAS/HETCOR NMR. Ab initio calculations were also performed to place additional constraints on the 1H NMR characteristics of AlOH and Si(OH)Al groups. This study has revealed, for the first time, the presence of free OH (i.e. (Ca, Mg)OH), SiOH and AlOH species, in addition to molecular H2O, in hydrous glasses of a depolymerized aluminosilicate composition. The AlOH groups are mostly associated with four-coordinate Al, but some are associated with five- and six-coordinate Al.

  13. Hybrid Circuit QED with Double Quantum Dots

    NASA Astrophysics Data System (ADS)

    Petta, Jason

    2014-03-01

    Cavity quantum electrodynamics explores quantum optics at the most basic level of a single photon interacting with a single atom. We have been able to explore cavity QED in a condensed matter system by placing a double quantum dot (DQD) inside of a high quality factor microwave cavity. Our results show that measurements of the cavity field are sensitive to charge and spin dynamics in the DQD.[2,3] We can explore non-equilibrium physics by applying a finite source-drain bias across the DQD, which results in sequential tunneling. Remarkably, we observe a gain as large as 15 in the cavity transmission when the DQD energy level detuning is matched to the cavity frequency. These results will be discussed in the context of single atom lasing.[4] I will also describe recent progress towards reaching the strong-coupling limit in cavity-coupled Si DQDs. In collaboration with Manas Kulkarni, Yinyu Liu, Karl Petersson, George Stehlik, Jacob Taylor, and Hakan Tureci. We acknowledge support from the Sloan and Packard Foundations, ARO, DARPA, and NSF.

  14. Investigation of organic condensed phoshates: Synthesis and structural characterization by 31P MAS NMR and X-ray diffraction of the 3-phenylpropylamonium cyclohexaphosphate dihydrate

    NASA Astrophysics Data System (ADS)

    Hlel, F.; Thouvenot, R.; Smiri, L.

    2005-05-01

    Preparation, crystal structure and infra-red absorption spectra are reported for a new organic salt of the cyclohexaphosphate, [C6H5(CH2)3NH3]6P6O18 . 2 H2O. The new compound crystallizes in the triclinic system (P space group) with Z = 2 and the following unit cell dimensions: a = 10.528(3), b = 19.183(2), c = 9.839(3) Å, = 74.92(5), = 117.48(6) and = 99.90(5)°. The structure was solved by using 6709 independent reflections down to R value of 0.039. The ring anion exhibits internal symmetry. Its main geometrical features are those commonly observed in the atomic arrangements of cyclohexaphosphates. The three dimensional cohesion of this atomic arrangement is maintained through H-bonds between organic cations, water molecules and the external oxygen atoms of the P6O18-6 ring. The H-bond interactions induce local distortions of the ring leading to the existence of three different types of phosphate tetrahedra.Solid-state 31P magic-angle-spinning nuclear magnetic resonance (MAS NMR), performed at 162 MHz shows three isotropic resonances at -19.8, -22.6 and -24.5 ppm, confirming the non-equivalence of the three PO4 groups. They are characterized by different chemical shift tensor parameters, which are in agreement with the local geometrical features of the tetrahedra.

  15. Structural investigations of silicate-phosphate glasses containing MoO3 by FTIR, Raman and 31P MAS NMR spectroscopies

    NASA Astrophysics Data System (ADS)

    Szumera, Magdalena

    2014-09-01

    Molybdenum is a transition metal (refers to the “d” block of the periodic table) whose atom has an incomplete d sub-shell. It is known that in silicate glasses molybdenum may exist under four oxidation states: Mo6+, Mo5+, Mo4+ and Mo3+, simultaneously molybdenum cations, depending on their content in the glass network, may either be a glass forming component, or act as a modifier. The contemporary literature data show studies conducted mostly on the structure of silicate, phosphate, borate and borosilicate glasses containing molybdenum ions, but not silicate-phosphate glasses. Therefore, the author has undertaken detailed studies using FTIR, Raman and 31P MAS NMR techniques in order to examine the effect of MoO3 addition into the structure of silicate-phosphate glasses from SiO2sbnd P2O5sbnd K2Osbnd CaOsbnd MgO system. On the basis of obtained results it was concluded that molybdenum ions in the analysed glasses act as a modifier, which follows from the gradual breakage of oxygen bridges, i.e. Psbnd Osbnd P, Sisbnd Osbnd Si, and Sisbnd Osbnd P, and the following formation of connections such as Mo[MoO4]sbnd Osbnd Si and/or Mo[MoO4]sbnd Osbnd P. In summary, it is concluded that the increase of MoO3 content (up to 4.4 mol.%) in the structure of glasses of SiO2sbnd P2O5sbnd K2Osbnd MgOsbnd CaO system results in weakening of the structure and gradual increase of the degree of silico-oxygen and phosphor-oxygen frameworks depolymerisation.

  16. Structural investigations of silicate-phosphate glasses containing MoO3 by FTIR, Raman and 31P MAS NMR spectroscopies.

    PubMed

    Szumera, M

    2014-09-15

    Molybdenum is a transition metal (refers to the "d" block of the periodic table) whose atom has an incomplete d sub-shell. It is known that in silicate glasses molybdenum may exist under four oxidation states: Mo6+, Mo5+, Mo4+ and Mo3+, simultaneously molybdenum cations, depending on their content in the glass network, may either be a glass forming component, or act as a modifier. The contemporary literature data show studies conducted mostly on the structure of silicate, phosphate, borate and borosilicate glasses containing molybdenum ions, but not silicate-phosphate glasses. Therefore, the author has undertaken detailed studies using FTIR, Raman and 31P MAS NMR techniques in order to examine the effect of MoO3 addition into the structure of silicate-phosphate glasses from SiO2P2O5K2OCaOMgO system. On the basis of obtained results it was concluded that molybdenum ions in the analysed glasses act as a modifier, which follows from the gradual breakage of oxygen bridges, i.e. POP, SiOSi, and SiOP, and the following formation of connections such as Mo[MoO4]OSi and/or Mo[MoO4]OP. In summary, it is concluded that the increase of MoO3 content (up to 4.4 mol.%) in the structure of glasses of SiO2P2O5K2OMgOCaO system results in weakening of the structure and gradual increase of the degree of silico-oxygen and phosphor-oxygen frameworks depolymerisation. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. {sup 1}H and {sup 23}Na MAS NMR spectroscopy of cationic species in CO{sub 2} selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange

    SciTech Connect

    Arevalo-Hidalgo, Ana G.; Dugar, Sneha; Fu, Riqiang; Hernandez-Maldonado, Arturo J.

    2012-07-15

    The location of extraframework cations in Sr{sup 2+} and Ba{sup 2+} ion-exchanged SAPO-34 was estimated by means of {sup 1}H and {sup 23}Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO{sub 2} adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium. - Graphical abstract: MAS NMR was used to elucidate the position the cationic species in alkaline earth metal exchanged silicoaluminophosphates. These species played a significant role during the ion exchange process and, therefore, the materials ultimate CO{sub 2} adsorption performance. Highlights: Black-Right-Pointing-Pointer Location of extraframework Sr{sup 2+} or Ba{sup 2+} cations was estimated by means of {sup 1}H and {sup 23}Na MAS NMR. Black-Right-Pointing-Pointer Level of Sr{sup 2+} or Ba{sup 2+} ion exchange was limited by the presence of protons and sodium cations. Black-Right-Pointing-Pointer Presence of ammonium cations in the supercages facilitated the exchange. Black-Right-Pointing-Pointer Sr{sup 2+} and Ba{sup 2+} ion exchanged SAPOs are outstanding CO{sub 2} adsorbents.

  18. Investigation of relative metabolic changes in the organs and plasma of rats exposed to X-ray radiation using HR-MAS (1)H NMR and solution (1)H NMR.

    PubMed

    Jang, Won Gyo; Park, Ju Yeon; Lee, Jueun; Bang, Eunjung; Kim, So Ra; Lee, Eun Kyeong; Yun, Hyun Jin; Kang, Chang-Mo; Hwang, Geum-Sook

    2016-04-01

    Excess exposure to ionizing radiation generates reactive oxygen species and increases the cellular inflammatory response by modifying various metabolic pathways. However, an investigation of metabolic perturbations and organ-specific responses based on the amount of radiation during the acute phase has not been conducted. In this study, high-resolution magic-angle-spinning (HR-MAS) NMR and solution NMR-based metabolic profiling were used to investigate dose-dependent metabolic changes in multiple organs and tissues--including the jejunum, spleen, liver, and plasma--of rats exposed to X-ray radiation. The organs, tissues, and blood samples were obtained 24, 48, and 72 h after exposure to low-dose (2 Gy) and high-dose (6 Gy) X-ray radiation and subjected to metabolite profiling and multivariate analyses. The results showed the time course of the metabolic responses, and many significant changes were detected in the high-dose compared with the low-dose group. Metabolites with antioxidant properties showed acute responses in the jejunum and spleen after radiation exposure. The levels of metabolites related to lipid and protein metabolism were decreased in the jejunum. In addition, amino acid levels increased consistently at all post-irradiation time points as a consequence of activated protein breakdown. Consistent with these changes, plasma levels of tricarboxylic acid cycle intermediate metabolites decreased. The liver did not appear to undergo remarkable metabolic changes after radiation exposure. These results may provide insight into the major metabolic perturbations and mechanisms of the biological systems in response to pathophysiological damage caused by X-ray radiation.

  19. Modeling Ti/Ge Distribution in LiTi2-xGex(PO4)3 NASICON Series by (31)P MAS NMR and First-Principles DFT Calculations.

    PubMed

    Diez-Gómez, Virginia; Arbi, Kamel; Sanz, Jesús

    2016-08-03

    Ti/Ge distribution in rhombohedral LiTi2-xGex(PO4)3 NASICON series has been analyzed by (31)P magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and first-principles density functional theory (DFT) calculations. Nuclear magnetic resonance is an excellent probe to follow Ti/Ge disorder, as it is sensitive to the atomic scale environment without long-range periodicity requirements. In the samples considered here, PO4 units are surrounded by four Ti/Ge octahedra, and then, five different components ascribed to P(OTi)4, P(OTi)3(OGe), P(OTi)2(OGe)2, P(OTi)(OGe)3, and P(OGe)4 environments are expected in (31)P MAS NMR spectra of R3̅c NASICON samples. However, (31)P MAS NMR spectra of analyzed series display a higher number of signals, suggesting that, although the overall symmetry remains R3̅c, partial substitution causes a local decrement in symmetry. With the aid of first-principles DFT calculations, 10 detected (31)P NMR signals have been assigned to different Ti4-nGen arrangements in the R3 subgroup symmetry. In this assignment, the influence of octahedra of the same or different R2(PO4)3 structural units has been considered. The influence of bond distances, angles and atom charges on (31)P NMR chemical shieldings has been discussed. Simulation of the LiTi2-xGex(PO4)3 series suggests that detection of 10 P environments is mainly due to the existence of two oxygen types, O1 and O2, whose charges are differently affected by Ge and Ti occupation of octahedra. From the quantitative analysis of detected components, a random Ti/Ge distribution has been deduced in next nearest neighbor (NNN) sites that surround tetrahedral PO4 units. This random distribution was supported by XRD data displaying Vegard's law.

  20. Metabolic profiling of ob/ob mouse fatty liver using HR-MAS (1)H-NMR combined with gene expression analysis reveals alterations in betaine metabolism and the transsulfuration pathway.

    PubMed

    Gogiashvili, Mikheil; Edlund, Karolina; Gianmoena, Kathrin; Marchan, Rosemarie; Brik, Alexander; Andersson, Jan T; Lambert, Jörg; Madjar, Katrin; Hellwig, Birte; Rahnenführer, Jörg; Hengstler, Jan G; Hergenröder, Roland; Cadenas, Cristina

    2017-02-01

    Metabolic perturbations resulting from excessive hepatic fat accumulation are poorly understood. Thus, in this study, leptin-deficient ob/ob mice, a mouse model of fatty liver disease, were used to investigate metabolic alterations in more detail. Metabolites were quantified in intact liver tissues of ob/ob (n = 8) and control (n = 8) mice using high-resolution magic angle spinning (HR-MAS) (1)H-NMR. In addition, after demonstrating that HR-MAS (1)H-NMR does not affect RNA integrity, transcriptional changes were measured by quantitative real-time PCR on RNA extracted from the same specimens after HR-MAS (1)H-NMR measurements. Importantly, the gene expression changes obtained agreed with those observed by Affymetrix microarray analysis performed on RNA isolated directly from fresh-frozen tissue. In total, 40 metabolites could be assigned in the spectra and subsequently quantified. Quantification of lactate was also possible after applying a lactate-editing pulse sequence that suppresses the lipid signal, which superimposes the lactate methyl resonance at 1.3 ppm. Significant differences were detected for creatinine, glutamate, glycine, glycolate, trimethylamine-N-oxide, dimethylglycine, ADP, AMP, betaine, phenylalanine, and uridine. Furthermore, alterations in one-carbon metabolism, supported by both metabolic and transcriptional changes, were observed. These included reduced demethylation of betaine to dimethylglycine and the reduced expression of genes coding for transsulfuration pathway enzymes, which appears to preserve methionine levels, but may limit glutathione synthesis. Overall, the combined approach is advantageous as it identifies changes not only at the single gene or metabolite level but also deregulated pathways, thus providing critical insight into changes accompanying fatty liver disease. Graphical abstract A Evaluation of RNA integrity before and after HR-MAS (1)H-NMR of intact mouse liver tissue. B Metabolite concentrations and gene

  1. Double-quantum homonuclear rotary resonance: Efficient dipolar recovery in magic-angle spinning nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Nielsen, N. C.; Bildsøe, H.; Jakobsen, H. J.; Levitt, M. H.

    1994-08-01

    We describe an efficient method for the recovery of homonuclear dipole-dipole interactions in magic-angle spinning NMR. Double-quantum homonuclear rotary resonance (2Q-HORROR) is established by fulfilling the condition ωr=2ω1, where ωr is the sample rotation frequency and ω1 is the nutation frequency around an applied resonant radio frequency (rf) field. This resonance can be used for double-quantum filtering and measurement of homonuclear dipolar interactions in the presence of magic-angle spinning. The spin dynamics depend only weakly on crystallite orientation allowing good performance for powder samples. Chemical shift effects are suppressed to zeroth order. The method is demonstrated for singly and doubly 13C labeled L-alanine.

  2. Investigating the Surface Structure of γ-Al 2 O 3 Supported WO X Catalysts by High Field 27 Al MAS NMR and Electronic Structure Calculations

    SciTech Connect

    Wan, Chuan; Hu, Mary Y.; Jaegers, Nicholas R.; Shi, Dachuan; Wang, Huamin; Gao, Feng; Qin, Zhaohai; Wang, Yong; Hu, Jian Zhi

    2016-10-13

    The metal-support interaction in γ-Al2O3 supported WOX catalysts is investigated by a combination of high field quantitative single pulse (SP) 27Al MAS NMR spectroscopy, 2D MQMAS, 1H-27Al CP/MAS, and electronic structure calculations. NMR allows the observation of at least seven different Al sites, including a pentahedral Al site, three different tetrahedral Al sites, and three octahedral Al sites. It is found that the penta-coordinated Al (AlP) site density decreases monotonically with an increased WOX loading while the octahedral Al (AlO) site density increases concurrently. This suggests that the Alp sites are the preferred surface anchoring positions for the WOX species. Importantly, the AlP site isotropic chemical shift observed for the unsupported γ-Al2O3 at about 38 ppm migrates into the octahedral region with a new isotropic chemical shift value appearing near 7 ppm when the Alp site is anchored by WOX species. Density functional theory (DFT) computational modeling of the NMR parameters on proposed cluster models is carried out to accurately interpret the dramatic chemical shift changes from which the detailed anchoring mechanisms are obtained. It is found that tungsten dimers and monomers are the preferred supported surface species on γ-Al2O3, wherein one monomeric and several dimeric structures are identified as the most likely surface anchoring structures.

  3. Spins of Andreev states in double quantum dots

    NASA Astrophysics Data System (ADS)

    Su, Zhaoen; Chen, Jun; Yu, Peng; Hocervar, Moira; Plissard, Sebastien; Car, Diana; Tacla, Alexandre; Daley, Andrew; Pekker, David; Bakkers, Erik; Frolov, Sergey

    Andreev (or Shiba) states in coupled double quantum dots is an open field. Here we demonstrate the realization of Andreev states in double quantum dots in an InSb nanowire coupled to two NbTiN superconductors. The magnetic field dependence of the Andreev states has been explored to resolve the spins in different double dot configurations. The experiment helps to understand the interplay between pair correlation, exchange energy and charging energy with a well-controlled system. It also opens the possibility to implement Majorana modes in Kitaev chains made of such dots.

  4. Mapping strain exerted on blood vessel walls using deuterium double-quantum-filtered MRI

    PubMed Central

    Sharf, Yehuda; Seo, Yoshiteru; Eliav, Uzi; Akselrod, Solang; Navon, Gil

    1998-01-01

    A technique is described for displaying distinct tissue layers of large blood vessel walls as well as measuring their mechanical strain. The technique is based on deuterium double-quantum-filtered (DQF) spectroscopic imaging. The effectiveness of the double-quantum filtration in suppressing the signal of bulk water is demonstrated on a phantom consisting of rat tail tendon fibers. Only intrafibrillar water is displayed, excluding all other signals of water molecules that reorient isotropically. One- and two-dimensional spectroscopic imaging of bovine aorta and coronary arteries show the characteristic DQF spectrum of each of the tissue layers. This property is used to obtain separate images of the outer layer, the tunica adventitia, or the intermediate layer, the tunica media, or both. To visualize the effect of elongation, the average residual quadrupole splitting <Δνq> is calculated for each pixel. Two-dimensional deuterium quadrupolar splitting images are obtained for a fully relaxed and a 55% elongated sample of bovine coronary artery. These images indicate that the strong effect of strain is associated with water molecules in the tunica adventitia whereas the DQF NMR signal of water in the tunica media is apparently strain-insensitive. After appropriate calibration, these average quadrupolar splitting images can be interpreted as strain maps. PMID:9539698

  5. Mapping strain exerted on blood vessel walls using deuterium double-quantum-filtered MRI.

    PubMed

    Sharf, Y; Seo, Y; Eliav, U; Akselrod, S; Navon, G

    1998-04-14

    A technique is described for displaying distinct tissue layers of large blood vessel walls as well as measuring their mechanical strain. The technique is based on deuterium double-quantum-filtered (DQF) spectroscopic imaging. The effectiveness of the double-quantum filtration in suppressing the signal of bulk water is demonstrated on a phantom consisting of rat tail tendon fibers. Only intrafibrillar water is displayed, excluding all other signals of water molecules that reorient isotropically. One- and two-dimensional spectroscopic imaging of bovine aorta and coronary arteries show the characteristic DQF spectrum of each of the tissue layers. This property is used to obtain separate images of the outer layer, the tunica adventitia, or the intermediate layer, the tunica media, or both. To visualize the effect of elongation, the average residual quadrupole splitting is calculated for each pixel. Two-dimensional deuterium quadrupolar splitting images are obtained for a fully relaxed and a 55% elongated sample of bovine coronary artery. These images indicate that the strong effect of strain is associated with water molecules in the tunica adventitia whereas the DQF NMR signal of water in the tunica media is apparently strain-insensitive. After appropriate calibration, these average quadrupolar splitting images can be interpreted as strain maps.

  6. Circuit QED in a double quantum dot system

    SciTech Connect

    Toida, Hiraku; Nakajima, Takashi; Komiyama, Susumu

    2013-12-04

    Strong coupling peculiar feature is demonstrated in a coupled qubit-resonator system consisting of a GaAs double quantum dot and a coplanar waveguide resonator. Qubit-resonator coupling strength (g and the decoherence rate Γ are directly derived from the experiment, assuring a strong coupling condition (g/Γ ≈ 2)

  7. Donor-acceptor stacking arrangements in bulk and thin-film high-mobility conjugated polymers characterized using molecular modelling and MAS and surface-enhanced solid-state NMR spectroscopy.

    PubMed

    Chaudhari, Sachin R; Griffin, John M; Broch, Katharina; Lesage, Anne; Lemaur, Vincent; Dudenko, Dmytro; Olivier, Yoann; Sirringhaus, Henning; Emsley, Lyndon; Grey, Clare P

    2017-04-01

    Conjugated polymers show promising properties as cheap, sustainable and solution-processable semiconductors. A key challenge in the development of these materials is to determine the polymer chain structure, conformation and packing in both the bulk polymer and in thin films typically used in devices. However, many characterisation techniques are unable to provide atomic-level structural information owing to the presence of disorder. Here, we use molecular modelling, magic-angle spinning (MAS) and dynamic nuclear polarisation surface-enhanced NMR spectroscopy (DNP SENS) to characterise the polymer backbone group conformations and packing arrangement in the high-mobility donor-acceptor copolymer diketopyrrolo-pyrrole-dithienylthieno[3,2-b]thiophene (DPP-DTT). Using conventional (1)H and (13)C solid-state MAS NMR coupled with density functional theory calculations and molecular dynamics simulations, we find that the bulk polymer adopts a highly planar backbone conformation with a laterally-shifted donor-on-acceptor stacking arrangement. DNP SENS enables acquisition of (13)C NMR data for polymer films, where sensitivity is limiting owing to small sample volumes. The DNP signal enhancement enables a two-dimensional (1)H-(13)C HETCOR spectrum to be recorded for a drop-cast polymer film, and a (13)C CPMAS NMR spectrum to be recorded for a spin-coated thin-film with a thickness of only 400 nm. The results show that the same planar backbone structure and intermolecular stacking arrangement is preserved in the films following solution processing and annealing, thereby rationalizing the favourable device properties of DPP-DTT, and providing a protocol for the study of other thin film materials.

  8. The use of a selective saturation pulse to suppress t1 noise in two-dimensional 1H fast magic angle spinning solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Robertson, Aiden J.; Pandey, Manoj Kumar; Marsh, Andrew; Nishiyama, Yusuke; Brown, Steven P.

    2015-11-01

    A selective saturation pulse at fast magic angle spinning (MAS) frequencies (60+ kHz) suppresses t1 noise in the indirect dimension of two-dimensional 1H MAS NMR spectra. The method is applied to a synthetic nucleoside with an intense methyl 1H signal due to triisopropylsilyl (TIPS) protecting groups. Enhanced performance in terms of suppressing the methyl signal while minimising the loss of signal intensity of nearby resonances of interest relies on reducing spin diffusion - this is quantified by comparing two-dimensional 1H NOESY-like spin diffusion spectra recorded at 30-70 kHz MAS. For a saturation pulse centred at the methyl resonance, the effect of changing the nutation frequency at different MAS frequencies as well as the effect of changing the pulse duration is investigated. By applying a pulse of duration 30 ms and nutation frequency 725 Hz at 70 kHz MAS, a good compromise of significant suppression of the methyl resonance combined with the signal intensity of resonances greater than 5 ppm away from the methyl resonance being largely unaffected is achieved. The effectiveness of using a selective saturation pulse is demonstrated for both homonuclear 1H-1H double quantum (DQ)/single quantum (SQ) MAS and 14N-1H heteronuclear multiple quantum coherence (HMQC) two-dimensional solid-state NMR experiments.

  9. The use of a selective saturation pulse to suppress t1 noise in two-dimensional (1)H fast magic angle spinning solid-state NMR spectroscopy.

    PubMed

    Robertson, Aiden J; Pandey, Manoj Kumar; Marsh, Andrew; Nishiyama, Yusuke; Brown, Steven P

    2015-11-01

    A selective saturation pulse at fast magic angle spinning (MAS) frequencies (60+kHz) suppresses t1 noise in the indirect dimension of two-dimensional (1)H MAS NMR spectra. The method is applied to a synthetic nucleoside with an intense methyl (1)H signal due to triisopropylsilyl (TIPS) protecting groups. Enhanced performance in terms of suppressing the methyl signal while minimising the loss of signal intensity of nearby resonances of interest relies on reducing spin diffusion--this is quantified by comparing two-dimensional (1)H NOESY-like spin diffusion spectra recorded at 30-70 kHz MAS. For a saturation pulse centred at the methyl resonance, the effect of changing the nutation frequency at different MAS frequencies as well as the effect of changing the pulse duration is investigated. By applying a pulse of duration 30 ms and nutation frequency 725 Hz at 70 kHz MAS, a good compromise of significant suppression of the methyl resonance combined with the signal intensity of resonances greater than 5 ppm away from the methyl resonance being largely unaffected is achieved. The effectiveness of using a selective saturation pulse is demonstrated for both homonuclear (1)H-(1)H double quantum (DQ)/single quantum (SQ) MAS and (14)N-(1)H heteronuclear multiple quantum coherence (HMQC) two-dimensional solid-state NMR experiments.

  10. Pressure induced structural and density changes in Ca and Mg aluminosilicate glasses (MO/Al2O3≤1) recovered from 1-3 GPa: 27Al, 17O, 29Si MAS NMR and density

    NASA Astrophysics Data System (ADS)

    Bista, S.; Stebbins, J. F.

    2016-12-01

    Numerous studies have shown that at least in Na and K aluminosilicate melts and glasses, the presence of NBO facilitates the increase in Al coordination with pressure, for example albite and jadeite compositions show little structural change at 2-3 GPa. Much less is known about higher field strength cations such as Ca and Mg, despite their importance in mafic magmas. Therefore, in this study, we have studied several compositions of Ca and Mg aluminosilicate glasses with little to no NBO in the metaluminous and peraluminous regions. Our 27Al MAS NMR on the glasses recovered from high T and P show surprisingly rapid increases in average Al coordination with pressure, with the largest increases recorded in the Mg system. In Ca aluminosilicate glasses, the average Al coordination increase in peralkaline and peraluminous glasses follow a much more rapid rise compared to the metaluminous, although the metaluminous composition also shows a significant change in Al coordination unlike the Na aluminosilicate glasses of similar composition. In Mg aluminosilicate glasses, the average Al coordination increase in both peralkaline and metaluminous compositions are similar. Our study shows that the mechanism of the coordination increase with pressure is more complex than the simple consumption of NBO, especially with the high field strength and smaller size modifier cations like Mg. We also observed shifts in 29Si and 17O MAS NMR spectra suggesting increase in high coordinated Al neighbors, but these changes are harder to uniquely interpret.

  11. SU(4) Kondo entanglement in double quantum dot devices

    NASA Astrophysics Data System (ADS)

    Bonazzola, Rodrigo; Andrade, J. A.; Facio, Jorge I.; García, D. J.; Cornaglia, Pablo S.

    2017-08-01

    We analyze, from a quantum information theory perspective, the possibility of realizing an SU(4) entangled Kondo regime in semiconductor double quantum dot devices. We focus our analysis on the ground-state properties and consider the general experimental situation where the coupling parameters of the two quantum dots differ. We model each quantum dot with an Anderson-type Hamiltonian including an interdot Coulomb repulsion and tunnel couplings for each quantum dot to independent fermionic baths. We find that the spin and pseudospin entanglements can be made equal, and the SU(4) symmetry recovered, if the gate voltages are chosen in such a way that the average charge occupancies of the two quantum dots are equal, and the double occupancy on the double quantum dot is suppressed. We present density matrix renormalization group numerical results for the spin and pseudospin entanglement entropies, and analytical results for a simplified model that captures the main physics of the problem.

  12. A solid state NMR study of layered double hydroxides intercalated with para-amino salicylate, a tuberculosis drug.

    PubMed

    Jensen, Nicholai Daugaard; Bjerring, Morten; Nielsen, Ulla Gro

    2016-09-01

    Para-amino salicylate (PAS), a tuberculosis drug, was intercalated in three different layered double hydroxides (MgAl, ZnAl, and CaAl-LDH) and the samples were studied by multi-nuclear ((1)H, (13)C, and (27)Al) solid state NMR (SSNMR) spectroscopy in combination with powder X-ray diffraction (PXRD), elemental analysis and IR-spectroscopy to gain insight into the bulk and atomic level structure of these LDHs especially with a view to the purity of the LDH-PAS materials and the concentration of impurities. The intercalations of PAS in MgAl-, ZnAl-, and CaAl-LDH's were confirmed by (13)C SSNMR and PXRD. Moreover, (13)C MAS NMR and infrared spectroscopy show that PAS did not decompose during synthesis. Large amounts (20-41%) of amorphous aluminum impurities were detected in the structure using (27)Al single pulse and 3QMAS NMR spectra, which in combination with (1)H single and double quantum experiments also showed that the M(II):Al ratio was higher than predicted from the bulk metal composition of MgAl-PAS and ZnAl-PAS. Moreover, the first high-resolution (1)H SSNMR spectra of a CaAl LDH is reported and assigned using (1)H single and double quantum experiments in combination with (27)Al{(1)H} HETCOR.

  13. Quantized charge pumping through a carbon nanotube double quantum dot

    NASA Astrophysics Data System (ADS)

    Chorley, S. J.; Frake, J.; Smith, C. G.; Jones, G. A. C.; Buitelaar, M. R.

    2012-04-01

    We demonstrate single-electron pumping in a gate-defined carbon nanotube double quantum dot. By periodic modulation of the potentials of the two quantum dots, we move the system around charge triple points and transport exactly one electron or hole per cycle. We investigate the pumping as a function of the modulation frequency and amplitude and observe good current quantization up to frequencies of 18 MHz where rectification effects cause the mechanism to break down.

  14. Probing Oxide-Ion Mobility in the Mixed Ionic–Electronic Conductor La2NiO4+δ by Solid-State 17O MAS NMR Spectroscopy

    PubMed Central

    2016-01-01

    While solid-state NMR spectroscopic techniques have helped clarify the local structure and dynamics of ionic conductors, similar studies of mixed ionic–electronic conductors (MIECs) have been hampered by the paramagnetic behavior of these systems. Here we report high-resolution 17O (I = 5/2) solid-state NMR spectra of the mixed-conducting solid oxide fuel cell (SOFC) cathode material La2NiO4+δ, a paramagnetic transition-metal oxide. Three distinct oxygen environments (equatorial, axial, and interstitial) can be assigned on the basis of hyperfine (Fermi contact) shifts and quadrupolar nutation behavior, aided by results from periodic DFT calculations. Distinct structural distortions among the axial sites, arising from the nonstoichiometric incorporation of interstitial oxygen, can be resolved by advanced magic angle turning and phase-adjusted sideband separation (MATPASS) NMR experiments. Finally, variable-temperature spectra reveal the onset of rapid interstitial oxide motion and exchange with axial sites at ∼130 °C, associated with the reported orthorhombic-to-tetragonal phase transition of La2NiO4+δ. From the variable-temperature spectra, we develop a model of oxide-ion dynamics on the spectral time scale that accounts for motional differences of all distinct oxygen sites. Though we treat La2NiO4+δ as a model system for a combined paramagnetic 17O NMR and DFT methodology, the approach presented herein should prove applicable to MIECs and other functionally important paramagnetic oxides. PMID:27538437

  15. Probing Oxide-Ion Mobility in the Mixed Ionic-Electronic Conductor La2NiO4+δ by Solid-State (17)O MAS NMR Spectroscopy.

    PubMed

    Halat, David M; Dervişoğlu, Rıza; Kim, Gunwoo; Dunstan, Matthew T; Blanc, Frédéric; Middlemiss, Derek S; Grey, Clare P

    2016-09-14

    While solid-state NMR spectroscopic techniques have helped clarify the local structure and dynamics of ionic conductors, similar studies of mixed ionic-electronic conductors (MIECs) have been hampered by the paramagnetic behavior of these systems. Here we report high-resolution (17)O (I = 5/2) solid-state NMR spectra of the mixed-conducting solid oxide fuel cell (SOFC) cathode material La2NiO4+δ, a paramagnetic transition-metal oxide. Three distinct oxygen environments (equatorial, axial, and interstitial) can be assigned on the basis of hyperfine (Fermi contact) shifts and quadrupolar nutation behavior, aided by results from periodic DFT calculations. Distinct structural distortions among the axial sites, arising from the nonstoichiometric incorporation of interstitial oxygen, can be resolved by advanced magic angle turning and phase-adjusted sideband separation (MATPASS) NMR experiments. Finally, variable-temperature spectra reveal the onset of rapid interstitial oxide motion and exchange with axial sites at ∼130 °C, associated with the reported orthorhombic-to-tetragonal phase transition of La2NiO4+δ. From the variable-temperature spectra, we develop a model of oxide-ion dynamics on the spectral time scale that accounts for motional differences of all distinct oxygen sites. Though we treat La2NiO4+δ as a model system for a combined paramagnetic (17)O NMR and DFT methodology, the approach presented herein should prove applicable to MIECs and other functionally important paramagnetic oxides.

  16. 13C and 15N—Chemical Shift Anisotropy of Ampicillin and Penicillin-V Studied by 2D-PASS and CP/MAS NMR

    NASA Astrophysics Data System (ADS)

    Antzutkin, Oleg N.; Lee, Young K.; Levitt, Malcolm H.

    1998-11-01

    The principal values of the chemical shift tensors of all13C and15N sites in two antibiotics, ampicillin and penicillin-V, were determined by 2-dimensionalphaseadjustedspinningsideband (2D-PASS) and conventional CP/MAS experiments. The13C and15N chemical shift anisotropies (CSA), and their confidence limits, were evaluated using a Mathematica program. The CSA values suggest a revised assignment of the 2-methyl13C sites in the case of ampicillin. We speculate on a relationship between the chemical shift principal values of many of the13C and15N sites and the β-lactam ring conformation.

  17. The Local Structural State of Aluminosilicate Garnet Solid Solutions: An Investigation of Grospydite Garnet from the Roberts Victor Kimberlite Using Paramagnetically Shifted 27Al and 29Si MAS NMR Resonances

    NASA Astrophysics Data System (ADS)

    Geiger, C. A.; Palke, A. C.; Stebbins, J. F.

    2014-12-01

    Most rock-forming silicates are substitutional solid solutions. Over the years extensive research has been done to determine their structural and crystal chemical properties. Here, the distribution of cations, or order-disorder behavior, is of central importance. In the case of aluminosilicate garnet solid solutions (X3Al2Si3O12 with X = Mg, Fe2+, Mn2+ and Ca) it has been shown that both synthetic and natural crystals have random long-range X-cation disorder in space group Ia-3d, as given by X-ray single-crystal diffraction measurements. However, the structural state of natural garnets at the local scale is not known. Garnet from a grospydite xenolith from the Roberts Victor kimberlite, South Africa, was studied by 27Al and 29Si MAS NMR spectroscopy. The research thrust was placed on measuring and analyzing paramagnetically shifted resonances to determine the local (short range) structural state of the X-cations in a grossular-rich ternary aluminosilicate garnet solid solution. The garnet crystals are compositionally homogeneous based on microprobe analysis, showing no measurable zoning, and have the formula Grs46.7Prp30.0Alm23.3. The garnet is cubic with the standard garnet space group Ia-3d. The 27Al MAS NMR spectrum shows a very broad asymmetric resonance located between about 100 and -50 ppm. It consists of a number of individual overlapping paramagnetically shifted resonances, which are difficult to analyze quantitatively. The 29Si MAS NMR spectrum, showing better resolution, has two observable resonances termed S0 and S4. S0 is located between about -60 ppm and -160 ppm and S4 is centered at roughly 95 ppm. Both S0 and S4 are composite resonances in nature containing many overlapping individual peaks. S0 contains information on local cation configurations whereby an isolated SiO4 group in the garnet structure does not have an edge-shared Fe2+-containing dodecahedron. S4 involves local configurations where there is one edge-shared dodecahedron containing Fe2

  18. Efficient polarization transfer between spin-1/2 and ¹⁴N nuclei in solid-state MAS NMR spectroscopy.

    PubMed

    Basse, Kristoffer; Jain, Sheetal Kumar; Bakharev, Oleg; Nielsen, Niels Chr

    2014-07-01

    Polarization transfer between spin-1/2 nuclei and quadrupolar spin-1 nuclei such as (14)N in solid-state NMR is severely challenged by the typical presence of large quadrupole coupling interactions. This has effectively prevented the use of the abundant (14)N spin as a probe to structural information and its use as an element in multi-dimensional solid-state NMR correlation experiments for assignment and structural characterization. In turn, this has been a contributing factor to the extensive use of isotope labeling in biological solid-state NMR, where (14)N is replaced with (15)N. The alternative strategy of using the abundant (14)N spins calls for methods enabling efficient polarization transfer between (14)N and its binding partners. This work demonstrates that the recently introduced (RESPIRATION)CP transfer method can be optimized to achieve efficient (1)H ↔(14)N polarization transfer under magic angle spinning conditions. The method is demonstrated numerically and experimentally on powder samples of NH4NO3 and L-alanine.

  19. Characterization of the wound-induced material in Citrus paradisi fruit peel by carbon-13 CP-MAS solid state NMR spectroscopy.

    PubMed

    Lai, Simona; Lai, Adolfo; Stange, Richard R; McCollum, T Greg; Schirra, Mario

    2003-05-01

    Grapefruit, Citrus paradisi, were injured, inoculated with Penicillium digitatum and incubated under conditions favourable for the accumulation of defence related material. Histochemical examination revealed that tissues adjacent to inoculated injuries contained phloroglucinol-HCl (PG-HCl) reactive material. Solvent washed cell wall preparations of intact and injured-inoculated peel were further purified using a mixture of cell wall degrading enzymes. Samples from injured inoculated tissue contained PG-HCl reactive globular material in addition to the fragments of xylem and cuticle found in controls. The principal chemical moieties of the material that accumulates in grapefruit injuries during wound-healing were studied by solid state 13C cross-polarization magic angle spinning NMR. A complete assignment of the NMR signals was made. From the analysis evidence was found that cellulose and hemicellulose are the biopolymers present in the intact peel samples, in addition, relevant quantities of cutin were found in the residues of enzyme digest. The NMR difference spectrum intact- wounded peels showed resonances which were attributed to all major functional groups of the aromatic-aliphatic suberin polyester of new material produced by the wounds. Information on the latter polyester was obtained by analyzing the T(1)rho (1H) relaxation.

  20. Investigating albendazole desmotropes by solid-state NMR spectroscopy.

    PubMed

    Chattah, Ana K; Zhang, Rongchun; Mroue, Kamal H; Pfund, Laura Y; Longhi, Marcela R; Ramamoorthy, Ayyalusamy; Garnero, Claudia

    2015-03-02

    Characterization of the molecular structure and physicochemical solid-state properties of the solid forms of pharmaceutical compounds is a key requirement for successful commercialization as potential active ingredients in drug products. These properties can ultimately have a critical effect on the solubility and bioavailability of the final drug product. Here, the desmotropy of Albendazole forms I and II was investigated at the atomic level. Ultrafast magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy, together with powder X-ray diffraction, thermal analysis, and Fourier transform infrared spectroscopy, were performed on polycrystalline samples of the two solids in order to fully characterize and distinguish the two forms. High-resolution one-dimensional (1)H, (13)C, and (15)N together with two-dimensional (1)H/(1)H single quantum-single quantum, (1)H/(1)H single quantum-double quantum, and (1)H/(13)C chemical shift correlation solid-state NMR experiments under MAS conditions were extensively used to decipher the intramolecular and intermolecular hydrogen bonding interactions present in both solid forms. These experiments enabled the unequivocal identification of the tautomers of each desmotrope. Our results also revealed that both solid forms may be described as dimeric structures, with different intermolecular hydrogen bonds connecting the tautomers in each dimer.

  1. An infrared and 1H MAS NMR investigation of strong hydrogen bonding in ussingite, Na2AlSi3O8(OH)

    NASA Astrophysics Data System (ADS)

    Johnson, E. A.; Rossman, G. R.

    The mineral ussingite, Na2AlSi3O8(OH), an ``interrupted'' tectosilicate, has strong hydrogen bonding between OH and the other nonbridging oxygen atom in the structure. Infrared spectra contain a strongly polarized, very broad OH-stretching band with an ill-defined maximum between 1500 and 1800 cm-1, and a possible OH librational bending mode at 1295 cm-1. The IR spectra confirm the orientation of the OH vector within the triclinic unit cell as determined from X-ray refinement (Rossi et al. 1974). There are three distinct bands in the 1H NMR spectrum of ussingite: a predominant band at 13.5 ppm (TMS) representing 90% of the structural hydrogen, a second band at 15.9 ppm corresponding to 8% of the protons, and a third band at 11.0 ppm accounting for the remaining 2% of structural hydrogen. From the correlation between hydrogen bond length and 1H NMR chemical shift (Sternberg and Brunner 1994), the predominant hydrogen bond length (H...O) was calculated to be 1.49 Å, in comparison to the hydrogen bond length determined from X-ray refinement (1.54 Å). The population of protons at 15.9 ppm is consistent with 5-8% Al-Si disorder. Although the ussingite crystal structure and composition are similar to those of low albite, the bonding environment of OH in low albite and other feldspars, as characterized through IR and 1H NMR, is fundamentally different from the strong hydrogen bonding found in ussingite.

  2. Carbonation of C–S–H and C–A–S–H samples studied by {sup 13}C, {sup 27}Al and {sup 29}Si MAS NMR spectroscopy

    SciTech Connect

    Sevelsted, Tine F.; Skibsted, Jørgen

    2015-05-15

    Synthesized calcium silicate hydrate (C–S–H) samples with Ca/Si ratios of 0.66, 1.0, and 1.5 have been exposed to atmospheric CO{sub 2} at room temperature and high relative humidity and studied after one to 12 weeks. {sup 29}Si NMR reveals that the decomposition of C–S–H caused by carbonation involves two steps and that the decomposition rate decreases with increasing Ca/Si ratio. The first step is a gradual decalcification of the C–S–H where calcium is removed from the interlayer and defect sites in the silicate chains until Ca/Si = 0.67 is reached, ideally corresponding to infinite silicate chains. In the seconds step, calcium from the principal layers is consumed, resulting in the final decomposition of the C–S–H and the formation of an amorphous silica phase composed of Q{sup 3} and Q{sup 4} silicate tetrahedra. The amount of solid carbonates and of carbonate ions in a hydrous environment increases with increasing Ca/Si ratio for the C–S–H, as shown by {sup 13}C NMR. For C–A–S–H samples with Ca/Si = 1.0 and 1.5, {sup 27}Al NMR demonstrates that all aluminium sites associated with the C–S–H are consumed during the carbonation reactions and incorporated mainly as tetrahedral Al(–OSi){sub 4} units in the amorphous silica phase. A small amount of penta-coordinated Al sites has also been identified in the silica phase.

  3. Spin-transfer pathways in paramagnetic lithium transition-metal phosphates from combined broadband isotropic solid-state MAS NMR spectroscopy and DFT calculations.

    PubMed

    Clément, Raphaële J; Pell, Andrew J; Middlemiss, Derek S; Strobridge, Fiona C; Miller, Joel K; Whittingham, M Stanley; Emsley, Lyndon; Grey, Clare P; Pintacuda, Guido

    2012-10-17

    Substituted lithium transition-metal (TM) phosphate LiFe(x)Mn(1-x)PO(4) materials with olivine-type structures are among the most promising next generation lithium ion battery cathodes. However, a complete atomic-level description of the structure of such phases is not yet available. Here, a combined experimental and theoretical approach to the detailed assignment of the (31)P NMR spectra of the LiFe(x)Mn(1-x)PO(4) (x = 0, 0.25, 0.5, 0.75, 1) pure and mixed TM phosphates is developed and applied. Key to the present work is the development of a new NMR experiment enabling the characterization of complex paramagnetic materials via the complete separation of the individual isotropic chemical shifts, along with solid-state hybrid DFT calculations providing the separate hyperfine contributions of all distinct Mn-O-P and Fe-O-P bond pathways. The NMR experiment, referred to as aMAT, makes use of short high-powered adiabatic pulses (SHAPs), which can achieve 100% inversion over a range of isotropic shifts on the order of 1 MHz and with anisotropies greater than 100 kHz. In addition to complete spectral assignments of the mixed phases, the present study provides a detailed insight into the differences in electronic structure driving the variations in hyperfine parameters across the range of materials. A simple model delimiting the effects of distortions due to Mn/Fe substitution is also proposed and applied. The combined approach has clear future applications to TM-bearing battery cathode phases in particular and for the understanding of complex paramagnetic phases in general.

  4. Stoichiometric compounds of magnesium dichloride with ethanol for the supported Ziegler-Natta catalysis: first recognition and multidimensional MAS NMR study.

    PubMed

    Sozzani, Piero; Bracco, Silvia; Comotti, Angiolina; Simonutti, Roberto; Camurati, Isabella

    2003-10-22

    Ethanol associates easily with MgCl(2) to form adducts of complex architecture, but until now available characterization methods have failed to identify the pure stoichiometric compounds and their structures. To remedy this, we set about applying homonuclear and heteronuclear 2D correlated solid-state NMR spectroscopy to identify the pure compounds and the ethanol-to-magnesium coordination pattern. High spinning speed and Lee-Goldburg sequences were able to reduce the hydrogen spin-diffusion and homonuclear coupling in the crystalline solid, thus achieving high resolution also in the hydrogen domain. On this basis, the pure adducts, of interest as catalyst supports for Ziegler-Natta polymerization, were isolated for the first time. Magnesium coordination sites with given numbers of ligands and their multiplicity in the crystal cells were determined in the new-found stoichiometric complexes. Variable temperature and 2D carbon-carbon exchange NMR, as well as relaxation times in the fast motion regime, revealed the disordering phenomena generated by ethanol dynamics in the crystal. Decoding the intriguing polymorphism of the precursors permits to trace the genealogy of tailored MgCl(2) titanate granules, active as highly productive catalysts for the stereospecific polymerization of olefins.

  5. New insights into oxygen environments generated during phosphate glass alteration: a combined 17O MAS and MQMAS NMR and first principles calculations study.

    PubMed

    Forler, Nina; Vasconcelos, Filipe; Cristol, Sylvain; Paul, Jean-François; Montagne, Lionel; Charpentier, Thibault; Mauri, Francesco; Delevoye, Laurent

    2010-08-21

    In the present study, we used a combination of (17)O NMR methods at a high magnetic field with first-principles calculations in order to characterize the oxygen sites in a series of hydroxylated sodium phosphate compounds, namely the hydrogen pyrophosphate Na(2)H(2)P(2)O(7) and the hydrogen orthophosphates NaH(2)PO(4), NaH(2)PO(4) x H(2)O and NaH(2)PO(4) x 2 H(2)O. The chemical shifts and quadrupolar parameters of these compounds were interpreted in terms of local and semi-local environment, i.e., the chemical composition of the immediate surroundings and the nature of the bonds, e.g. hydrogen bonding. The magnitude of the quadrupolar interaction and its asymmetry were revealed to be a precise indicator of the local structure in sodium hydrogen phosphates. Our (17)O NMR experimental and computing approach allowed for identification and quantification of the different crystalline phases involved in the weathering mechanism of a sodium phosphate glass, even in small amount.

  6. Structural, (197)Au Mössbauer and solid state (31)P CP/MAS NMR studies on bis (cis-bis(diphenylphosphino)ethylene) gold(I) complexes [Au(dppey)(2)]X for X = PF(6), I.

    PubMed

    Healy, Peter C; Loughrey, Bradley T; Bowmaker, Graham A; Hanna, John V

    2008-07-28

    (197)Au Mössbauer spectra for the d(10) gold(i) phosphine complexes, [Au(dppey)(2)]X (X = PF(6), I; dppey = (cis-bis(diphenylphosphino)ethylene), and the single crystal X-ray structure and solid state (31)P CPMAS NMR spectrum of [Au(dppey)(2)]I are reported here. In [Au(dppey)(2)]I the AuP(4) coordination geometry is distorted from the approximately D(2) symmetry observed for the PF(6)(-) complex with Au-P bond lengths 2.380(2)-2.426(2) A and inter-ligand P-Au-P angles 110.63(5)-137.71(8) degrees . Quadrupole splitting parameters derived from the Mössbauer spectra are consistent with the increased distortion of the AuP(4) coordination sphere with values of 1.22 and 1.46 mm s(-1) for the PF(6)(-) and I(-) complexes respectively. In the solid state (31)P CP MAS NMR spectrum of [Au(dppey)(2)]I, signals for each of the four crystallographically independent phosphorus nuclei are observed, with the magnitude of the (197)Au quadrupole coupling being sufficiently large to produce a collapse of (1)J(Au-P) splitting from quartets to doublets. The results highlight the important role played by the counter anion in the determination of the structural and spectroscopic properties of these sterically crowded d(10) complexes.

  7. Computational modeling of electrophotonics nanomaterials: Tunneling in double quantum dots

    SciTech Connect

    Vlahovic, Branislav Filikhin, Igor

    2014-10-06

    Single electron localization and tunneling in double quantum dots (DQD) and rings (DQR) and in particular the localized-delocalized states and their spectral distributions are considered in dependence on the geometry of the DQDs (DQRs). The effect of violation of symmetry of DQDs geometry on the tunneling is studied in details. The cases of regular and chaotic geometries are considered. It will be shown that a small violation of symmetry drastically affects localization of electron and that anti-crossing of the levels is the mechanism of tunneling between the localized and delocalized states in DQRs.

  8. Quantum criticality in a double-quantum-dot system.

    PubMed

    Zaránd, Gergely; Chung, Chung-Hou; Simon, Pascal; Vojta, Matthias

    2006-10-20

    We discuss the realization of the quantum-critical non-Fermi-liquid state, originally discovered within the two-impurity Kondo model, in double-quantum-dot systems. Contrary to common belief, the corresponding fixed point is robust against particle-hole and various other asymmetries and is unstable only to charge transfer between the two dots. We propose an experimental setup where such charge transfer processes are suppressed, allowing a controlled approach to the quantum-critical state. We also discuss transport and scaling properties in the vicinity of the critical point.

  9. Diffusion thermopower of a serial double quantum dot

    NASA Astrophysics Data System (ADS)

    Thierschmann, H.; Henke, M.; Knorr, J.; Maier, L.; Heyn, C.; Hansen, W.; Buhmann, H.; Molenkamp, L. W.

    2013-12-01

    We have experimentally studied the diffusion thermopower of a serial double quantum dot, defined electrostatically in a GaAs/AlGaAs heterostructure. We present the thermopower stability diagram for a temperature difference ΔT = (20 ± 10) mK across the device and find a maximum thermovoltage signal of several μV in the vicinity of the triple points. Along a constant energy axis in this regime, the data show a characteristic pattern which is in agreement with Mott's relation and can be well understood within a model of sequential transport.

  10. Magnetic field induced minigap in double quantum wells

    SciTech Connect

    Simmons, J.A.; Lyo, S.K.; Klem, J.F.; Harff, N.E. |

    1994-07-01

    We report discovery of a partial energy gap, or minigap, in strongly coupled double quantum wells (QWs), due to an anticrossing of the two QW dispersion curves. The anticrossing and minigap are induced by an in-plane magnetic field B{sub {parallel}}, and give rise to large distortions in the Fermi surface and density of states, including a Van Hove singularity. Sweeping B{sub {parallel}} moves the minigap through the Fermi level, with the upper and lower gap edges producing a sharp maximum and minimum in the low-temperature in-plane conductance, in agreement with theoretical calculations. The gap energy may be directly determined from the data.

  11. Quantum efficiency of a double quantum dot microwave photon detector

    NASA Astrophysics Data System (ADS)

    Wong, Clement; Vavilov, Maxim

    Motivated by recent interest in implementing circuit quantum electrodynamics with semiconducting quantum dots, we study charge transfer through a double quantum dot (DQD) capacitively coupled to a superconducting cavity subject to a microwave field. We analyze the DQD current response using input-output theory and determine the optimal parameter regime for complete absorption of radiation and efficient conversion of microwave photons to electric current. For experimentally available DQD systems, we show that the cavity-coupled DQD operates as a photon-to-charge converter with quantum efficiencies up to 80% C.W. acknowledges support by the Intelligence Community Postdoctoral Research Fellowship Program.

  12. Proton-detected 3D (15)N/(1)H/(1)H isotropic/anisotropic/isotropic chemical shift correlation solid-state NMR at 70kHz MAS.

    PubMed

    Pandey, Manoj Kumar; Yarava, Jayasubba Reddy; Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2016-01-01

    Chemical shift anisotropy (CSA) tensors offer a wealth of information for structural and dynamics studies of a variety of chemical and biological systems. In particular, CSA of amide protons can provide piercing insights into hydrogen-bonding interactions that vary with the backbone conformation of a protein and dynamics. However, the narrow span of amide proton resonances makes it very difficult to measure (1)H CSAs of proteins even by using the recently proposed 2D (1)H/(1)H anisotropic/isotropic chemical shift (CSA/CS) correlation technique. Such difficulties due to overlapping proton resonances can in general be overcome by utilizing the broad span of isotropic chemical shifts of low-gamma nuclei like (15)N. In this context, we demonstrate a proton-detected 3D (15)N/(1)H/(1)H CS/CSA/CS correlation experiment at fast MAS frequency (70kHz) to measure (1)H CSA values of unresolved amide protons of N-acetyl-(15)N-l-valyl-(15)N-l-leucine (NAVL).

  13. High-resolution MAS 1H NMR spectroscopic analysis of rabbit cornea after treatment with dexamethasone and exposure to UV-B radiation.

    PubMed

    Saether, Oddbjørn; Krane, Jostein; Risa, Øystein; Cejková, Jitka; Midelfart, Anna

    2005-12-01

    Metabolic changes in rabbit cornea after combined long-term steroid treatment and UV-B exposure were investigated. Corneas were exposed to UV-B radiation (2.05 J/cm2) after 36 days topical pretreatment with either 0.1% dexamethasone or saline. Twenty-four hours after UV-B exposure, corneas were excised and aqueous humour aspirated. Intact corneal tissues were analyzed by magic angle spinning proton NMR spectroscopy and pattern recognition methods. UV-B decreased corneal ascorbate (63% reduction), taurine (62%), and choline (63%), whereas glucose was elevated. Dexamethasone pretreatment further depleted corneal taurine and ascorbate, decreased aqueous ascorbate (85%), and accumulated glucose in cornea and aqueous humour. The results reflect antioxidative mechanisms and osmoregulation.

  14. Andreev molecules in semiconductor nanowire double quantum dots.

    PubMed

    Su, Zhaoen; Tacla, Alexandre B; Hocevar, Moïra; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Daley, Andrew J; Pekker, David; Frolov, Sergey M

    2017-09-19

    Chains of quantum dots coupled to superconductors are promising for the realization of the Kitaev model of a topological superconductor. While individual superconducting quantum dots have been explored, control of longer chains requires understanding of interdot coupling. Here, double quantum dots are defined by gate voltages in indium antimonide nanowires. High transparency superconducting niobium titanium nitride contacts are made to each of the dots in order to induce superconductivity, as well as probe electron transport. Andreev bound states induced on each of dots hybridize to define Andreev molecular states. The evolution of these states is studied as a function of charge parity on the dots, and in magnetic field. The experiments are found in agreement with a numerical model.Quantum dots in a nanowire are one possible approach to creating a solid-state quantum simulator. Here, the authors demonstrate the coupling of electronic states in a double quantum dot to form Andreev molecule states; a potential building block for longer chains suitable for quantum simulation.

  15. The Amblygonite (LiAlPO{sub 4}F)-Montebrasite (LiAlPO{sub 4}OH) Solid Solution: A Combined powder and single-crystal neutron diffraction and solid-state {sup 6}Li MAS, CP MAS, and REDOR NMR study

    SciTech Connect

    Groat, Lee A.; Chakoumakos, Bryan C.; Brouwer, Darren H.; Hoffman, Christina M.; Fyfe, Colin A.; Morell, Heiko; Schultz, Arthur J.

    2003-01-01

    The amblygonite-montebrasite series of minerals, common constituents of granitic pegmatites and topaz-bearing granites, show complete solid solution with ideal composition LiAlPO{sub 4}(F, OH). These compounds are ideal for studying F {leftrightarrow} OH solid solution in minerals because natural members of the series generally show little deviation from the ideal composition. In this study, we used powder and single-crystal neutron diffraction and solid-state {sup 6}Li MAS, CP MAS, and REDOR NMR techniques to study the effect of F {leftrightarrow} OH substitution on the series. Lattice parameters refined from single-crystal neutron diffraction data show increasing b and decreasing a, c, and V with increasing F/(F + OH). The volume is highest for the OH end-member because of the presence of an additional atom (H). The a and c parameters decrease with increasing F/(F + OH) because the O-H vector is close to the a-c plane and the Al-OH/F vectors are approximately parallel to c. Lattice parameters refined from neutron powder diffraction patterns collected at lower T show that thermal contraction increases with F/(F + OH), presumably because the F anion takes up less space than the OH molecule. The results show that the OH/F position is always fully occupied. The H displacement ellipsoid shows little change with occupancy, which obviously corresponds negatively with increasing F/(F + OH). However, the Li displacement ellipsoid becomes extremely large and anisotropic with increasing F fraction. Most of the distortion is associated with the U{sub 3} eigenvalue, which lies between the c and c* directions. U{sub eq} values corresponding to the Li atom show a greater reduction with decreasing temperature than the other atoms. The temperature dependence of Li is the same regardless of F content. Even when extrapolated to absolute zero the Li displacement ellipsoid is very large, which implies a large static disorder.

  16. Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR

    NASA Astrophysics Data System (ADS)

    Wu, Chin H.; De Angelis, Anna A.; Opella, Stanley J.

    2014-09-01

    The efficiency and selectivity of SPECIFIC-CP, a widely used method for selective double cross-polarization in triple-resonance magic angle spinning solid-state NMR, is improved by performing the tangential-shaped 13C irradiation at an offset frequency that meets the Lee-Goldburg condition (LG-SPECIFIC-CP). This is demonstrated on polycrystalline samples of uniformly 13C, 15N labeled N-acetyl-leucine and N-formyl-Met-Leu-Phe-OH (MLF) at 700 MHz and 900 MHz 1H resonance frequencies, respectively. For the single 13Cα of N-acetyl-leucine, relative to conventional broad band cross-polarization, the SPECIFIC-CP signal has 47% of the intensity. Notably, the LG-SPECIFIC-CP signal has 72% of the intensity, essentially the theoretical maximum. There were no other changes in the experimental parameters. The three 13Cα signals in MLF show some variation in intensities, reflecting the relatively narrow bandwidth of a frequency-offset procedure, and pointing to future developments for this class of experiment.

  17. MAS NMR Study of the Metastable Solid Solutions Found in the LiFePO4/FePO4 System

    SciTech Connect

    Cabana, Jordi; Shirakawa, Junichi; Chen, Guoying; Richardson, Thomas; Grey, Clare P.

    2009-10-09

    Li and 3IP NMR experiments were conducted on a series of single- or two-phase samples in the LiFePCvFePCM system with different overall lithium contents, and containing the two end-members and/or two metastable solid solution hases, Lio.6FeP04 or Lio.34FeP04. These experiments were carried out at different temperatures in order to search for vacancy/charge ordering and ion/electron mobility in the metastable phases. Evidence for Li+-Fe2+ interactions was bserved for both Lio.6FeP04 and Lio.34FePC>4. The strength of this interaction leads to the formation of LiFePCvlike clusters in the latter, as shown by the room temperature data. Different motional processes are proposed to exist as the temperature is increased and various scenarios are discussed. While concerted lithium-electron hopping and/or correlations explains the data below 125C, evidence for some uncorrelated motion is found at higher temperatures, together with the onset of phase mixing.

  18. Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR

    PubMed Central

    Wu, C.H.; De Angelis, Anna A.; Opella, Stanley J.

    2014-01-01

    The efficiency and selectivity of SPECIFIC-CP, a widely used method for selective double cross-polarization in triple-resonance magic angle spinning solid-state NMR, is improved by performing the tangential-shaped 13C irradiation at an offset frequency that meets the Lee-Goldburg condition (LG-SPECIFIC-CP). This is demonstrated on polycrystalline samples of uniformly 13C, 15N labeled N-acetyl-leucine and N-formyl-Met-Leu-Phe-OH (MLF) at 700 MHz and 900 MHz 1H resonance frequencies, respectively. For the single 13Cα of N-acetyl-leucine, relative to conventional broad band cross-polarization, the SPECIFIC-CP signal has 47% of the intensity. Notably, the LG-SPECIFIC-CP signal has 72% of the intensity, essentially the theoretical maximum. There were no other changes in the experimental parameters. The three 13Cα signals in MLF show some variation in intensities, reflecting the relatively narrow bandwidth of a frequency-offset procedure, and pointing to future developments for this class of experiment. PMID:25051542

  19. A generalized theoretical framework for the description of spin decoupling in solid-state MAS NMR: Offset effect on decoupling performance.

    PubMed

    Tan, Kong Ooi; Agarwal, Vipin; Meier, Beat H; Ernst, Matthias

    2016-09-07

    We present a generalized theoretical framework that allows the approximate but rapid analysis of residual couplings of arbitrary decoupling sequences in solid-state NMR under magic-angle spinning conditions. It is a generalization of the tri-modal Floquet analysis of TPPM decoupling [Scholz et al., J. Chem. Phys. 130, 114510 (2009)] where three characteristic frequencies are used to describe the pulse sequence. Such an approach can be used to describe arbitrary periodic decoupling sequences that differ only in the magnitude of the Fourier coefficients of the interaction-frame transformation. It allows a ∼100 times faster calculation of second-order residual couplings as a function of pulse sequence parameters than full spin-dynamics simulations. By comparing the theoretical calculations with full numerical simulations, we show the potential of the new approach to examine the performance of decoupling sequences. We exemplify the usefulness of this framework by analyzing the performance of commonly used high-power decoupling sequences and low-power decoupling sequences such as amplitude-modulated XiX (AM-XiX) and its super-cycled variant SC-AM-XiX. In addition, the effect of chemical-shift offset is examined for both high- and low-power decoupling sequences. The results show that the cross-terms between the dipolar couplings are the main contributions to the line broadening when offset is present. We also show that the SC-AM-XIX shows a better offset compensation.

  20. Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR.

    PubMed

    Wu, Chin H; De Angelis, Anna A; Opella, Stanley J

    2014-09-01

    The efficiency and selectivity of SPECIFIC-CP, a widely used method for selective double cross-polarization in triple-resonance magic angle spinning solid-state NMR, is improved by performing the tangential-shaped (13)C irradiation at an offset frequency that meets the Lee-Goldburg condition (LG-SPECIFIC-CP). This is demonstrated on polycrystalline samples of uniformly (13)C, (15)N labeled N-acetyl-leucine and N-formyl-Met-Leu-Phe-OH (MLF) at 700MHz and 900MHz (1)H resonance frequencies, respectively. For the single (13)Cα of N-acetyl-leucine, relative to conventional broad band cross-polarization, the SPECIFIC-CP signal has 47% of the intensity. Notably, the LG-SPECIFIC-CP signal has 72% of the intensity, essentially the theoretical maximum. There were no other changes in the experimental parameters. The three (13)Cα signals in MLF show some variation in intensities, reflecting the relatively narrow bandwidth of a frequency-offset procedure, and pointing to future developments for this class of experiment. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. Molecular ordering of mixed surfactants in mesoporous silicas: A solid-state NMR study

    SciTech Connect

    Kobayashi, Takeshi; Mao, Kanmi; Wang, Shy-Guey; Lin, Victor S.-Y.; Pruski, Marek

    2011-02-17

    The use of mixed surfactants in the synthesis of mesoporous silica nanoparticles (MSNs) is of importance in the context of adjusting pore structures, sizes and morphologies. In the present study, the arrangement of molecules in micelles produced from a mixture of two surfactants, cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) was detailed by solid-state NMR spectroscopy. Proximities of methyl protons in the trimethylammonium headgroup of CTAB and protons in the pyridinium headgroup of CPB were observed under fast magic angle spinning (MAS) by {sup 1}H-{sup 1}H double quantum (DQ) MAS NMR and NOESY. This result suggested that CTAB and CPB co-exist in the pores without forming significant monocomponent domain structures. {sup 1}H-{sup 29}Si heteronuclear correlation (HETCOR) NMR showed that protons in the headgroups of CTAB are in closer proximity to the silica surface than those in the CPB headgroups. The structural information obtained in this investigation leads to better understanding of the mechanisms of self-assembly and their role in determining the structure and morphology of mesoporous materials.

  2. Extra-framework aluminium species in hydrated faujasite zeolite as investigated by two-dimensional solid-state NMR spectroscopy and theoretical calculations.

    PubMed

    Li, Shenhui; Zheng, Anmin; Su, Yongchao; Fang, Hanjun; Shen, Wanling; Yu, Zhiwu; Chen, Lei; Deng, Feng

    2010-04-21

    Extra-framework aluminium (EFAL) species in hydrated dealuminated HY zeolite were thoroughly investigated by various two-dimensional solid-state NMR techniques as well as density functional theoretical calculations. (27)Al MQ MAS NMR experiments demonstrated that five-coordinated and four-coordinated extra-framework aluminium subsequently disappeared with the increase of water loading, and the quadrupole interaction of each aluminium species decreased gradually during the hydration process. (1)H double quantum MAS NMR revealed that the EFAL species in the hydrated zeolite consisted of three components: a hydroxyl AlOH group, and two types of water molecule (rigid and mobile water). (1)H-(27)Al LG-CP HETCOR experiments indicated that both the extra-framework and the framework Al atoms were in close proximity to the rigid water in the fully rehydrated zeolite. The experimental results were further confirmed by DFT theoretical calculations. Moreover, theoretical calculation results further demonstrated that the EFAL species in the hydrated zeolite consisted of the three components and the calculated (1)H NMR chemical shift for each component agreed well with our NMR observations. It is the rigid water that connects the extra-framework aluminium with the four-coordinated framework aluminium through strong hydrogen bonds.

  3. Single-crystal X-ray diffraction and NMR crystallography of a 1:1 cocrystal of dithianon and pyrimethanil.

    PubMed

    Pöppler, Ann Christin; Corlett, Emily K; Pearce, Harriet; Seymour, Mark P; Reid, Matthew; Montgomery, Mark G; Brown, Steven P

    2017-03-01

    A single-crystal X-ray diffraction structure of a 1:1 cocrystal of two fungicides, namely dithianon (DI) and pyrimethanil (PM), is reported [systematic name: 5,10-dioxo-5H,10H-naphtho[2,3-b][1,4]dithiine-2,3-dicarbonitrile-4,6-dimethyl-N-phenylpyrimidin-2-amine (1/1), C14H4N2O2S2·C12H13N2]. Following an NMR crystallography approach, experimental solid-state magic angle spinning (MAS) NMR spectra are presented together with GIPAW (gauge-including projector augmented wave) calculations of NMR chemical shieldings. Specifically, experimental (1)H and (13)C chemical shifts are determined from two-dimensional (1)H-(13)C MAS NMR correlation spectra recorded with short and longer contact times so as to probe one-bond C-H connectivities and longer-range C...H proximities, whereas H...H proximities are identified in a (1)H double-quantum (DQ) MAS NMR spectrum. The performing of separate GIPAW calculations for the full periodic crystal structure and for isolated molecules allows the determination of the change in chemical shift upon going from an isolated molecule to the full crystal structure. For the (1)H NMR chemical shifts, changes of 3.6 and 2.0 ppm correspond to intermolecular N-H...O and C-H...O hydrogen bonding, while changes of -2.7 and -1.5 ppm are due to ring current effects associated with C-H...π interactions. Even though there is a close intermolecular S...O distance of 3.10 Å, it is of note that the molecule-to-crystal chemical shifts for the involved sulfur or oxygen nuclei are small.

  4. Two-dimensional Electronic Double-Quantum Coherence Spectroscopy

    PubMed Central

    Kim, Jeongho; Mukamel, Shaul

    2009-01-01

    CONSPECTUS The theory of electronic structure of many-electron systems like molecules is extraordinarily complicated. A lot can be learned by considering how electron density is distributed, on average, in the average field of the other electrons in the system. That is, mean field theory. However, to describe quantitatively chemical bonds, reactions, and spectroscopy requires consideration of the way that electrons avoid each other by the way they move; this is called electron correlation (or in physics, the many-body problem for fermions). While great progress has been made in theory, there is a need for incisive experimental tests that can be undertaken for large molecular systems in the condensed phase. Here we report a two-dimensional (2D) optical coherent spectroscopy that correlates the double excited electronic states to constituent single excited states. The technique, termed two-dimensional double-coherence spectroscopy (2D-DQCS), makes use of multiple, time-ordered ultrashort coherent optical pulses to create double- and single-quantum coherences over time intervals between the pulses. The resulting two-dimensional electronic spectrum maps the energy correlation between the first excited state and two-photon allowed double-quantum states. The principle of the experiment is that when the energy of the double-quantum state, viewed in simple models as a double HOMO to LUMO excitation, equals twice that of a single excitation, then no signal is radiated. However, electron-electron interactions—a combination of exchange interactions and electron correlation—in real systems generates a signal that reveals precisely how the energy of the double-quantum resonance differs from twice the single-quantum resonance. The energy shift measured in this experiment reveals how the second excitation is perturbed by both the presence of the first excitation and the way that the other electrons in the system have responded to the presence of that first excitation. We

  5. (29)Si, (47)Ti, (49)Ti and (195)Pt solid state MAS NMR spectroscopic investigations of ternary silicides TPtSi, germanides TPtGe (T = Ti, Zr, Hf) and stannide TiPtSn.

    PubMed

    Benndorf, Christopher; Eckert, Hellmut; Pöttgen, Rainer

    2016-05-10

    Eight ternary tetrelides TPtX (T = Ti, Zr, Hf; X = Si, Ge, Sn) were synthesized from the elements by arc-melting and subsequent annealing. TiPtSi, ZrPtSi, ZrPtGe, HfPtSi and HfPtGe crystallize with the orthorhombic TiNiSi type structure, in the space group Pnma. The structures of HfPtSi (a = 654.44(9), b = 387.97(6), c = 750.0(1) pm, wR2 = 0.0592, 411 F(2) values, 20 variables) and HfPtGe (a = 660.36(7), b = 395.18(4), c = 763.05(8) pm, wR2 = 0.0495, 430 F(2) values, 20 variables) were refined from single crystal X-ray diffractometer data. TiPtSn adopts the cubic MgAgAs type. TiPtGe is dimorphic with a TiNiSi type high-temperature modification which transforms to cubic LT-TiPtGe (MgAgAs type). All phases were investigated by high resolution (29)Si, (47)Ti, (49)Ti and (195)Pt solid state MAS NMR spectroscopy. In the cubic compounds, the (47/49)Ti NMR signals are easily detected owing to the absence of quadrupolar broadening effects. The (195)Pt resonances of the orthorhombic compounds are characterized by strongly negative isotropic Knight shifts and large Knight shift anisotropies, whereas positive isotropic Knight shifts and no anisotropies are observed for the cubic compounds. These results indicate that the phase transition in TiPtGe is associated with dramatic changes in the electronic properties. Within each group of isotypic compounds the isotropic (29)Si, (47/49)Ti and (195)Pt Knight shifts show systematic dependences on the transition metal or tetrel atomic number, suggesting that the numerical values are influenced by the electronegativities of the metallic (or metalloid) neighbours.

  6. Lithium Ion Mobility in Lithium Phosphidosilicates: Crystal Structure, (7) Li, (29) Si, and (31) P MAS NMR Spectroscopy, and Impedance Spectroscopy of Li8 SiP4 and Li2 SiP2.

    PubMed

    Toffoletti, Lorenzo; Kirchhain, Holger; Landesfeind, Johannes; Klein, Wilhelm; van Wüllen, Leo; Gasteiger, Hubert A; Fässler, Thomas F

    2016-12-05

    The need to improve electrodes and Li-ion conducting materials for rechargeable all-solid-state batteries has drawn enhanced attention to the investigation of lithium-rich compounds. The study of the ternary system Li-Si-P revealed a series of new compounds, two of which, Li8 SiP4 and Li2 SiP2 , are presented. Both phases represent members of a new family of Li ion conductors that display Li ion conductivity in the range from 1.15(7)×10(-6) Scm(-1) at 0 °C to 1.2(2)×10(-4) Scm(-1) at 75 °C (Li8 SiP4 ) and from 6.1(7)×10(-8) Scm(-1) at 0 °C to 6(1)×10(-6) Scm(-1) at 75 °C (Li2 SiP2 ), as determined by impedance measurements. Temperature-dependent solid-state (7) Li NMR spectroscopy revealed low activation energies of about 36 kJ mol(-1) for Li8 SiP4 and about 47 kJ mol(-1) for Li2 SiP2 . Both compounds were structurally characterized by X-ray diffraction analysis (single crystal and powder methods) and by (7) Li, (29) Si, and (31) P MAS NMR spectroscopy. Both phases consist of tetrahedral SiP4 anions and Li counterions. Li8 SiP4 contains isolated SiP4 units surrounded by Li atoms, while Li2 SiP2 comprises a three-dimensional network based on corner-sharing SiP4 tetrahedra, with the Li ions located in cavities and channels. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Bound magnetic polaron in a semimagnetic double quantum well

    NASA Astrophysics Data System (ADS)

    Kalpana, P.; Jayakumar, K.

    2017-09-01

    The effect of different combinations of the concentration of Mn2+ ion in the Quantum well Cd1-xinMnxin Te and the barrier Cd1-xoutMnxout Te on the Bound Magnetic Polaron (BMP) in a Diluted Magnetic Semiconductors (DMS) Double Quantum Well (DQW) has been investigated. The Schrodinger equation is solved variationally in the effective mass approximation through which the Spin Polaronic Shift (SPS) due to the formation of BMP has been estimated for various locations of the donor impurity in the DQW. The results show that the effect of the increase of Mn2+ ion composition with different combinations on SPS is predominant for On Centre Well (OCW) impurity when compared to all other impurity locations when there is no application of magnetic field (γ = 0), γ being a dimensionless parameter for the magnetic field, and the same is predominant for On Centre Barrier (OCB) impurity with the application of external magnetic field (γ = 0.15).

  8. Injection Locking of a Semiconductor Double Quantum Dot Micromaser

    PubMed Central

    Liu, Y.-Y.; Stehlik, J.; Gullans, M. J.; Taylor, J. M.; Petta, J. R.

    2016-01-01

    Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models. PMID:28127226

  9. Normal, superconducting and topological regimes of hybrid double quantum dots.

    PubMed

    Sherman, D; Yodh, J S; Albrecht, S M; Nygård, J; Krogstrup, P; Marcus, C M

    2017-03-01

    Epitaxial semiconductor-superconductor hybrid materials are an excellent basis for studying mesoscopic and topological superconductivity, as the semiconductor inherits a hard superconducting gap while retaining tunable carrier density. Here, we investigate double-quantum-dot structures made from InAs nanowires with a patterned epitaxial Al two-facet shell that proximitizes two gate-defined segments along the nanowire. We follow the evolution of mesoscopic superconductivity and charging energy in this system as a function of magnetic field and voltage-tuned barriers. Interdot coupling is varied from strong to weak using side gates, and the ground state is varied between normal, superconducting and topological regimes by applying a magnetic field. We identify the topological transition by tracking the spacing between successive co-tunnelling peaks as a function of axial magnetic field and show that the individual dots host weakly hybridized Majorana modes.

  10. Pumped double quantum dot with spin-orbit coupling.

    PubMed

    Khomitsky, Denis; Sherman, Eugene

    2011-03-11

    We study driven by an external electric field quantum orbital and spin dynamics of electron in a one-dimensional double quantum dot with spin-orbit coupling. Two types of external perturbation are considered: a periodic field at the Zeeman frequency and a single half-period pulse. Spin-orbit coupling leads to a nontrivial evolution in the spin and orbital channels and to a strongly spin- dependent probability density distribution. Both the interdot tunneling and the driven motion contribute into the spin evolution. These results can be important for the design of the spin manipulation schemes in semiconductor nanostructures.PACS numbers: 73.63.Kv,72.25.Dc,72.25.Pn.

  11. Indirect excitons in (111) GaAs double quantum wells

    NASA Astrophysics Data System (ADS)

    Hubert, C.; Biermann, K.; Hernández-Mínguez, A.; Santos, P. V.

    2017-08-01

    We study the dynamics of indirect (or dipolar) excitons (interwell IXs) in GaAs (111) double quantum wells (DQWs) subjected to a transverse electric field. In comparison with single (111) QWs, these DQWs can store, for a comparable applied fields and optical excitation density, a density of interwell IXs much larger than in SQWs, thus leading to stronger interwell IX- IX repulsive interactions. We show by means of spatially-resolved optical spectroscopy that interwell IXs in (111) DWQs can be transported over distances exceeding 60 μm. From the spectral dependence of the interwell IX spatial distribution profiles, we show that the long transport distances are due to drift forces arising from the strong interwell IX- IX interactions.

  12. Simulating electron spin entanglement in a double quantum dot

    NASA Astrophysics Data System (ADS)

    Rodriguez-Moreno, M. A.; Hernandez de La Luz, A. D.; Meza-Montes, Lilia

    2011-03-01

    One of the biggest advantages of having a working quantum-computing device when compared with a classical one, is the exponential speedup of calculations. This exponential increase is based on the ability of a quantum system to create and operate on entangled states. In order to study theoretically the entanglement between two electron spins, we simulate the dynamics of two electron spins in an electrostatically-defined double quantum dot with a finite barrier height between the dots. Electrons are initially confined to separated quantum dots. Barrier height is varied and the spin entanglement as a function of this variation is investigated. The evolution of the system is simulated by using a numerical approach for solving the time-dependent Schrödinger equation for two particles. Partially supported by VIEP-BUAP.

  13. Injection Locking of a Semiconductor Double Quantum Dot Micromaser.

    PubMed

    Liu, Y-Y; Stehlik, J; Gullans, M J; Taylor, J M; Petta, J R

    2015-11-01

    Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models.

  14. Dynamical cooling of nuclear spins in double quantum dots.

    PubMed

    Rudner, M S; Levitov, L S

    2010-07-09

    Electrons trapped in quantum dots can exhibit quantum-coherent spin dynamics over long timescales. These timescales are limited by the coupling of electron spins to the disordered nuclear spin background, which is a major source of noise and dephasing in such systems. We propose a scheme for controlling and suppressing fluctuations of nuclear spin polarization in double quantum dots, which uses nuclear spin pumping in the spin-blockade regime. We show that nuclear spin polarization fluctuations can be suppressed when electronic levels in the two dots are properly positioned near resonance. The proposed mechanism is analogous to that of optical Doppler cooling. The Overhauser shift due to fluctuations of nuclear polarization brings electron levels in and out of resonance, creating internal feedback to suppress fluctuations. Estimates indicate that a better than 10-fold reduction of fluctuations is possible.

  15. Multi-electron double quantum dot spin qubits

    NASA Astrophysics Data System (ADS)

    Nielsen, Erik; Kestner, Jason; Barnes, Edwin; Das Sarma, Sankar

    2013-03-01

    Double quantum dot (DQD) spin quits in a solid state environment typically consist of two electron spins confined to a DQD potential. We analyze the viability and potential advantages of DQD qubits which use greater then two electrons, and present results for six-electron qubits using full configuration interaction methods. The principal results of this work are that such six electron DQDs can retain an isolated low-energy qubit space that is more robust to charge noise due to screening. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  16. Quantum state transfer in double-quantum-well devices

    NASA Technical Reports Server (NTRS)

    Jakumeit, Jurgen; Tutt, Marcel; Pavlidis, Dimitris

    1994-01-01

    A Monte Carlo simulation of double-quantum-well (DQW) devices is presented in view of analyzing the quantum state transfer (QST) effect. Different structures, based on the AlGaAs/GaAs system, were simulated at 77 and 300 K and optimized in terms of electron transfer and device speed. The analysis revealed the dominant role of the impurity scattering for the QST. Different approaches were used for the optimization of QST devices and basic physical limitations were found in the electron transfer between the QWs. The maximum transfer of electrons from a high to a low mobility well was at best 20%. Negative differential resistance is hampered by the almost linear rather than threshold dependent relation of electron transfer on electric field. By optimizing the doping profile the operation frequency limit could be extended to 260 GHz.

  17. Pauli spin blockade in CMOS double quantum dot devices

    NASA Astrophysics Data System (ADS)

    Kotekar-Patil, D.; Corna, A.; Maurand, R.; Crippa, A.; Orlov, A.; Barraud, S.; Hutin, L.; Vinet, M.; Jehl, X.; De Franceschi, S.; Sanquer, M.

    2017-03-01

    Silicon quantum dots are attractive candidates for the development of scalable, spin-based qubits. Pauli spin blockade in double quantum dots provides an efficient, temperature independent mechanism for qubit readout. Here we report on transport experiments in double gate nanowire transistors issued from a CMOS process on 300 mm silicon-on-insulator wafers. At low temperature the devices behave as two few-electron quantum dots in series. We observe signatures of Pauli spin blockade with a singlet-triplet splitting ranging from 0.3 to 1.3 meV. Magneto-transport measurements show that transitions which conserve spin are shown to be magnetic-field independent up to B = 6 T.

  18. Full characterization of a carbon nanotube parallel double quantum dot

    NASA Astrophysics Data System (ADS)

    Abulizi, Gulibusitan; Baumgartner, Andreas; Schönenberger, Christian

    2016-12-01

    We have measured the differential conductance of a parallel carbon nanotube (CNT) double quantum dot (DQD) with strong inter-dot capacitance and inter-dot tunnel coupling. Nominally, the device consists of a single CNT with two contacts. However, we identify two sets of Coulomb blockade (CB) diamonds that do not block transport individually, which suggest that two quantum dots (QDs) are contacted in parallel. We find strong and periodic anti-crossings in the gate and bias dependence, which are only possible if the QDs have similar characteristics. We discuss qualitatively the level spectrum and the involved transport processes in this device and extract the DQD coupling parameters. These results lead us to believe that clean and undoped QDs are formed parallel to the CNT axis, possibly on the outer and inner shells of a multi-wall CNT, or in a double-stranded CNT bundle.

  19. Quantum state transfer in double-quantum-well devices

    NASA Technical Reports Server (NTRS)

    Jakumeit, Jurgen; Tutt, Marcel; Pavlidis, Dimitris

    1994-01-01

    A Monte Carlo simulation of double-quantum-well (DQW) devices is presented in view of analyzing the quantum state transfer (QST) effect. Different structures, based on the AlGaAs/GaAs system, were simulated at 77 and 300 K and optimized in terms of electron transfer and device speed. The analysis revealed the dominant role of the impurity scattering for the QST. Different approaches were used for the optimization of QST devices and basic physical limitations were found in the electron transfer between the QWs. The maximum transfer of electrons from a high to a low mobility well was at best 20%. Negative differential resistance is hampered by the almost linear rather than threshold dependent relation of electron transfer on electric field. By optimizing the doping profile the operation frequency limit could be extended to 260 GHz.

  20. Dissipative electronic transport through double quantum dots irradiated with microwaves

    NASA Astrophysics Data System (ADS)

    Brandes, Tobias; Aguado, Ramon; Platero, Gloria

    2003-03-01

    Double quantum dots in the strong Coulomb blockade regime are realizations of two-level systems defined from two tunnel--splitted ground states, which are separated by a large energy gap from the remaining many--particle states. The interactions between electrons and bosonic degrees of freedom (photons, phonons) in these systems can be tested and manipulated in electronic transport experiments [1]. Monochromatic classical radiation (AC fields, microwaves) gives rise to various non-linear effects such as photo-sidebands or dynamical localization (coherent supression of tunneling) that show up in the time-averaged, stationary electronic current [2]. On the other hand, quantum noise of a dissipative environment strongly influences the transport properties of coupled quantum dots [3,4]. In this contribution, we quantitatively investigate the combined influence of a classical, monochromatic time-dependent AC field and a dissipative boson environment on the non-linear transport through a double quantum dot. We develop a Floquet-like theory [5] that takes into account the effect of the electron reservoirs (leads) and can be numerically evaluated for arbitrary strong AC fields and arbitrary boson environment. In limiting cases we reproduce previous analytical results (polaron tunneling, Tien-Gordon formula). [1] T. Fujisawa, T. H. Oosterkamp, W. G. van der Wiel, B. W. Broer, R. Aguado, S. Tarucha, and L. P. Kouwenhoven, Science 282, 932 (1998); R. H. Blick, D. Pfannkuche, R. J. Haug, K. v. Klitzing, and K. Eberl, Phys. Rev. Lett. 80, 4032 (1998). [2] T. H. Stoof, Yu. V. Nazarov, Phys. Rev. B 53, 1050 (1996). [3] T. Brandes, B. Kramer, Phys. Rev. Lett. 83, 3021 (1999); T. Brandes, F. Renzoni, R. H. Blick, Phys. Rev. B 64, 035319 (2001); T. Brandes, T. Vorrath, Phys. Rev. B 66, 075341 (2002). [4] R. Aguado and L. P. Kouwenhoven, Phys. Rev. Lett, 84, 1986 (2000). [5] M. Grifoni, P. Hänggi, Phys. Rep. 304, 229 (1998).

  1. Metabolic profiling of apples from different production systems before and after controlled atmosphere (CA) storage studied by (1)H high resolution-magic angle spinning (HR-MAS) NMR.

    PubMed

    Vermathen, Martina; Marzorati, Mattia; Diserens, Gaëlle; Baumgartner, Daniel; Good, Claudia; Gasser, Franz; Vermathen, Peter

    2017-10-15

    Determination of metabolic alterations in apples induced by such processes as different crop protection strategies or storage, are of interest to assess correlations with fruit quality or fruit disorders. Preliminary results proposed the metabolic discrimination of apples from organic (BIO), integrated (IP) and low-input (LI) production. To determine contributions of temporal metabolic developments and to define the type of metabolic changes during storage, (1)H high resolution-magic angle spinning (HR-MAS) NMR spectroscopy of apple pulp was performed before and after two time points of controlled atmosphere storage. Statistical analysis revealed similar metabolic changes over time for IP-, LI- and BIO-samples, mainly decreasing lipid and sucrose, and increasing fructose, glucose and acetaldehyde levels, which are potential contributors to fruit aroma. Across the production systems, BIO apples had consistently higher levels of fructose and monomeric phenolic compounds but lower levels of condensed polyphenols than LI and IP apples, while the remaining metabolites assimilated. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Combined MAS NMR and X-ray powder diffraction structural characterization of hydrofluorocarbon-134 adsorbed on zeolite NaY: Observation of cation migration and strong sorbate-cation interactions

    SciTech Connect

    Grey, C.P.; Poshni, F.I.; Gualtieri, A.F.; Norby, P. |; Hanson, J.C.; Corbin, D.R.

    1997-02-26

    {sup 23}Na MAS NMR and synchrotron X-ray powder diffraction methods have been used to study the binding of hydrofluorocarbon-134 (HFC-134, CF{sub 2}HCF{sub 2}H) in zeolite NaY. A contraction of the volume of the unit cell is observed on gas adsorption, and the interaction of HFC-134 with the extraframework sodium cations is so strong that extraframework sodium cations in the sodalite cages (site I`) migrate into the supercages. These sodium cations are found on positions close to the site III` positions of zeolite NaX. Both ends of the HFC molecules are bound sodium cations, the HFC molecule bridging the site II and III` cations in the supercages. The strong cation-HFC interaction results in a considerable displacement of the sodium site II cation along the [111] direction into the supercage and an increase in the T-O-T bond angle for the three oxygen atoms coordinated to this cation. A decrease in the {sup 23}Na quadrupole coupling constant on HFC adsorption from 4.4 to less than 2.8 MHz, for the sodium cations originally located in the sodalite cages (site I`), is consistent with the sodium cation migrations. 26 refs., 7 figs., 5 tabs.

  3. Characterization of white Portland cement hydration and the C-S-H structure in the presence of sodium aluminate by {sup 27}Al and {sup 29}Si MAS NMR spectroscopy

    SciTech Connect

    Andersen, Morten Daugaard; Jakobsen, Hans J.; Skibsted, Joergen

    2004-05-01

    The effects of hydrating a white Portland cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO{sub 2}) at 5 and 20 deg. C are investigated by {sup 27}Al and {sup 29}Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO{sub 2} accelerates the hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO{sub 4}/AlO{sub 4} tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the hydration (6 h to 2 years) but increases for higher concentration of the NaAlO{sub 2} solution. The average chain lengths of 'pure' silicate and SiO{sub 4}/AlO{sub 4} tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO{sub 2} reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.

  4. Characterization of polysulfone and polysulfone/vanillin microcapsules by 1H NMR spectroscopy, solid-state 13C CP/MAS-NMR spectroscopy, and N2 adsorption-desorption analyses.

    PubMed

    Peña, Brisa; de Ménorval, Louis-Charles; Garcia-Valls, Ricard; Gumí, Tània

    2011-11-01

    Textile detergent and softener industries have incorporated perfume microencapsulation technology to improve their products. Perfume encapsulation allows perfume protection until use and provides a long-lasting fragrance release. But, certain industrial microcapsules show low encapsulation capacity and low material stability. Polysulfone capsules have been already proposed to solve these drawbacks. Among them, PSf/Vanillin capsules were considered as a desirable system. They present both good material stability and high encapsulation capacity. However, several factors such as the final location of the perfume in the polymeric matrix, the aggregation state that it has in the capsule and its interaction with the capsule components have not been studied yet. These factors can provide vast information about the capsule performance and its improvement. With the aim to characterize these parameters, the physical and chemical properties of PSf/Vanillin capsules have been investigated by nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and N(2) adsorption-desorption measurements. AFM micrograph and N(2) isotherms confirm that the presence of vanillin modify the physical structure of PSf/Vanillin microcapsules as it is trapped in the capsule porosity. NMR results show that vanillin is present in solid state in PSf/Vanillin microcapsules.

  5. Applications of high-resolution 1H solid-state NMR.

    PubMed

    Brown, Steven P

    2012-02-01

    This article reviews the large increase in applications of high-resolution (1)H magic-angle spinning (MAS) solid-state NMR, in particular two-dimensional heteronuclear and homonuclear (double-quantum and spin-diffusion NOESY-like exchange) experiments, in the last five years. These applications benefit from faster MAS frequencies (up to 80 kHz), higher magnetic fields (up to 1 GHz) and pulse sequence developments (e.g., homonuclear decoupling sequences applicable under moderate and fast MAS). (1)H solid-state NMR techniques are shown to provide unique structural insight for a diverse range of systems including pharmaceuticals, self-assembled supramolecular structures and silica-based inorganic-organic materials, such as microporous and mesoporous materials and heterogeneous organometallic catalysts, for which single-crystal diffraction structures cannot be obtained. The power of NMR crystallography approaches that combine experiment with first-principles calculations of NMR parameters (notably using the GIPAW approach) are demonstrated, e.g., to yield quantitative insight into hydrogen-bonding and aromatic CH-π interactions, as well as to generate trial three-dimensional packing arrangements. It is shown how temperature-dependent changes in the (1)H chemical shift, linewidth and DQ-filtered signal intensity can be analysed to determine the thermodynamics and kinetics of molecular level processes, such as the making and breaking of hydrogen bonds, with particular application to proton-conducting materials. Other applications to polymers and biopolymers, inorganic compounds and bioinorganic systems, paramagnetic compounds and proteins are presented. The potential of new technological advances such as DNP methods and new microcoil designs is described.

  6. Computer-automated tuning of semiconductor double quantum dots into the single-electron regime

    SciTech Connect

    Baart, T. A.; Vandersypen, L. M. K.; Eendebak, P. T.; Reichl, C.; Wegscheider, W.

    2016-05-23

    We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.

  7. Lead hydro sodalite [Pb2(OH)(H2O)3]2[Al3Si3O12]2: synthesis and structure determination by combining X-ray rietveld refinement, 1H MAS NMR FTIR and XANES spectroscopy.

    PubMed

    Eiden-Assmann, S; Schneider, A M; Behrens, P; Wiebcke, M; Engelhardt, G; Felsche, J

    2000-01-01

    Ion exchange of the sodium hydro sodalites [Na3(H2O)4]2-[Al3Si3O12]2 [Na4(H3O2)]2[Al3Si3O12]2 and [Na4(OH)]2[Al3Si3O12]2 with aqueous Pb(NO3)2 solutions yielded, whichever reactant sodalite phase was used, the same lead hydro sodalite, [Pb2(OH)-(H2O)3]2[Al3Si3O12]2. Thus, in the case of the non-basic reactant [Na3(H2O)4]2-[Al3Si3O12]2 an overexchange occurs with respect to the number of nonframework cationic charges. Rietveld structure refinement of the lead hydro sodalite based on powder X-ray diffraction data (cubic, a = 9.070 A, room temperature, space group P43n) revealed that the two lead cations within each polyhedral sodalite cage form an orientationally disordered dinuclear [Pb2(micro-OH)(micro-H2O)(H2O)2]3+ complex. Due to additional lead framework oxygen bonds the coordination environment of each metal cation (CN 3+3) is approximately spherical, and clearly the lead 6s electron lone pair is stereochemically inactive. This is also suggested by the absence of a small peak at 13.025 keV, attributed in other Pb2+-O compounds to an electronic 2p-6s transition, in the PbL3 edge XANES spectrum. 1H MAS NMR and FTIR spectra show that the hydrogen atoms of the aqua hydroxo complex (which could not be determined in the Rietveld analysis) are involved in hydrogen bonds of various strengths.

  8. Experimental (X-ray, (13)C CP/MAS NMR, IR, RS, INS, THz) and Solid-State DFT Study on (1:1) Co-Crystal of Bromanilic Acid and 2,6-Dimethylpyrazine.

    PubMed

    Łuczyńska, Katarzyna; Drużbicki, Kacper; Lyczko, Krzysztof; Dobrowolski, Jan Cz

    2015-06-04

    A combined structural, vibrational spectroscopy, and solid-state DFT study of the hydrogen-bonded complex of bromanilic acid with 2,6-dimethylpyrazine is reported. The crystallographic structure was determined by means of low-temperature single-crystal X-ray diffraction, which reveals the molecular units in their native protonation states, forming one-dimensional infinite nets of moderate-strength O···H-N hydrogen bonds. The nature of the crystallographic forces, stabilizing the studied structure, has been drawn by employing the noncovalent interactions analysis. It was found that, in addition to the hydrogen bonding, the intermolecular forces are dominated by stacking interactions and C-H···O contacts. The thermal and calorimetric analysis was employed to probe stability of the crystal phase. The structural analysis was further supported by a computationally assisted (13)C CP/MAS NMR study, providing a complete assignment of the recorded resonances. The vibrational dynamics was explored by combining the optical (IR, Raman, TDs-THz) and inelastic neutron scattering (INS) spectroscopy techniques with the state-of-the-art solid-state density functional theory (DFT) computations. Despite the quasi-harmonic approximation assumed throughout the study, an excellent agreement between the theoretical and experimental data was achieved over the entire spectral range, allowing for a deep and possibly thorough understanding of the vibrational characteristics of the system. Particularly, the significant influence of the long-range dipole coupling on the IR spectrum has been revealed. On the basis of a wealth of information gathered, the recent implementation of a dispersion-corrected linear-response scheme has been extensively examined.

  9. XRD and {sup 29}Si MAS-NMR spectroscopy across the {beta}-Lu{sub 2}Si{sub 2}O{sub 7}-{beta}-Y{sub 2}Si{sub 2}O{sub 7} solid solution

    SciTech Connect

    Becerro, Ana I.

    2005-01-15

    Samples in the system Lu{sub 2-x}Y{sub x}Si{sub 2}O{sub 7} (0=MAS NMR spectra of the different members of the system agree with the XRD results, showing a linear decrease of the {sup 29}Si chemical shift with increasing Y content. Finally, a correlation reported in the literature to predict {sup 29}Si chemical shifts in silicates is applied here to obtain the theoretical variation in {sup 29}Si chemical shift values in the system Lu{sub 2}Si{sub 2}O{sub 7}-Y{sub 2}Si{sub 2}O{sub 7} and the results compare favorably with the values obtained experimentally.

  10. Double quantum dot Cooper-pair splitter at finite couplings

    NASA Astrophysics Data System (ADS)

    Hussein, Robert; Jaurigue, Lina; Governale, Michele; Braggio, Alessandro

    2016-12-01

    We consider the subgap physics of a hybrid double-quantum dot Cooper-pair splitter with large single-level spacings, in the presence of tunneling between the dots and finite Coulomb intra- and interdot Coulomb repulsion. In the limit of a large superconducting gap, we treat the coupling of the dots to the superconductor exactly. We employ a generalized master-equation method, which easily yields currents, noise, and cross-correlators. In particular, for finite inter- and intradot Coulomb interaction, we investigate how the transport properties are determined by the interplay between local and nonlocal tunneling processes between the superconductor and the dots. We examine the effect of interdot tunneling on the particle-hole symmetry of the currents with and without spin-orbit interaction. We show that spin-orbit interaction in combination with finite Coulomb energy opens the possibility to control the nonlocal entanglement and its symmetry (singlet/triplet). We demonstrate that the generation of nonlocal entanglement can be achieved even without any direct nonlocal coupling to the superconducting lead.

  11. Harmonic Generation in InAs Nanowire Double Quantum Dots

    NASA Astrophysics Data System (ADS)

    Schroer, M. D.; Jung, M.; Petersson, K. D.; Petta, J. R.

    2012-02-01

    InAs nanowires provide a useful platform for investigating the physics of confined electrons subjected to strong spin-orbit coupling. Using tunable, bottom-gated double quantum dots, we demonstrate electrical driving of single spin resonance.ootnotetextS. Nadj-Perge et al., Nature 468, 1084 (2010)^,ootnotetextM.D. Schroer et al., Phys. Rev. Lett. 107, 176811 (2011) We observe a standard spin response when the applied microwave frequency equals the Larmour frequency f0. However, we also observe an anomalous signal at frequencies fn= f0/ n for integer n up to n ˜5. This is equivalent to generation of harmonics of the spin resonance field. While a f0/2 signal has observed,ootnotetextE.A. Laird et al., Phys. Rev. Lett. 99, 246601 (2007) we believe this is the first observation of higher harmonics in spin resonance. Possible mechanisms will be discussed.ootnotetextE.I. Rashba, arXiv:1110.6569 (2011) Acknowledgements: Research supported by the Sloan and Packard Foundations, the NSF, and Army Research Office.

  12. Electron transport in coupled double quantum wells and wires

    SciTech Connect

    Harff, N.E.; Simmons, J.A.; Lyo, S.K.

    1997-04-01

    Due to inter-quantum well tunneling, coupled double quantum wells (DQWs) contain an extra degree of electronic freedom in the growth direction, giving rise to new transport phenomena not found in single electron layers. This report describes work done on coupled DQWs subject to inplane magnetic fields B{sub {parallel}}, and is based on the lead author`s doctoral thesis, successfully defended at Oregon State University on March 4, 1997. First, the conductance of closely coupled DQWs in B{sub {parallel}} is studied. B{sub {parallel}}-induced distortions in the dispersion, the density of states, and the Fermi surface are described both theoretically and experimentally, with particular attention paid to the dispersion anticrossing and resulting partial energy gap. Measurements of giant distortions in the effective mass are found to agree with theoretical calculations. Second, the Landau level spectra of coupled DQWs in tilted magnetic fields is studied. The magnetoresistance oscillations show complex beating as Landau levels from the two Fermi surface components cross the Fermi level. A third set of oscillations resulting from magnetic breakdown is observed. A semiclassical calculation of the Landau level spectra is then performed, and shown to agree exceptionally well with the data. Finally, quantum wires and quantum point contacts formed in DQW structures are investigated. Anticrossings of the one-dimensional DQW dispersion curves are predicted to have interesting transport effects in these devices. Difficulties in sample fabrication have to date prevented experimental verification. However, recently developed techniques to overcome these difficulties are described.

  13. Finite coupling effects in double quantum dots near equilibrium

    NASA Astrophysics Data System (ADS)

    Xu, Xiansong; Thingna, Juzar; Wang, Jian-Sheng

    2017-01-01

    A weak coupling quantum master equation provides reliable steady-state results only in the van Hove limit, i.e., when the system-lead coupling approaches zero. Recently, J. Thingna et al. [Phys. Rev. E 88, 052127 (2013), 10.1103/PhysRevE.88.052127] proposed an alternative approach, based on an analytic continuation of the Redfield solution, to evaluate the steady-state reduced density matrix up to second order in the system-bath coupling. The approach provides accurate results for harmonic oscillator and spin-bosonic systems. We apply this approach to study steady-state fermionic systems and the calculation on an exactly solvable double quantum dot system shows that the method is rigorously valid up to second order in system-lead coupling only near equilibrium, i.e., linear response regime. We further compare to the Redfield and the secular Redfield (Lindblad-type) master equations that are inaccurate in all parameter regimes. Lastly, we consider the nontrivial problem of strong Coulomb interaction and illustrate the interplay between system-lead coupling, interdot tunneling, and Coulomb strength that can be captured only via the analytic continuation method.

  14. BaBa-xy16: robust and broadband homonuclear DQ recoupling for applications in rigid and soft solids up to the highest MAS frequencies.

    PubMed

    Saalwächter, Kay; Lange, Frank; Matyjaszewski, Krzysztof; Huang, Chih-Feng; Graf, Robert

    2011-09-01

    We here present a substantially improved version of the popular Back-to-Back (BaBa) homonuclear double-quantum (DQ) MAS recoupling pulse sequence. By combining the original pulse sequence with a virtual π pulse train with xy-16 phase cycling along with time-reversed DQ reconversion, a truly broadband and exceptionally robust pulse sequence is obtained. The sequence has moderate radio-frequency power requirements, amounting to only one 360° nutation per rotor cycle, it is robust with respect to rf power and tune-up errors, and its broadband performance increases with increasing spinning frequency, here tested up to 63 kHz. The experiment can be applied to many spin-1/2 nuclei in rigid solids with substantial frequency offsets and CSAs, which is demonstrated on the example of 31P NMR of a magnesium ultraphosphate, comparing experimental data with multi-spin simulations, and we also show simulations addressing the performance in 13C NMR of bio(macro)molecules. 1H-based studies of polymer dynamics are highlighted for the example of a rigid solid with strongly anisotropic mobility, represented by a polymer inclusion compound, and for the example of soft materials with weak residual dipole-dipole couplings, represented by homogeneous and inhomogeneous elastomers. We advocate the use of normalized (relaxation-corrected) DQ build-up curves for a quantitative assessment of weak average dipole-dipole couplings and even distributions thereof.

  15. Single electron pumping in InAs nanowire double quantum dots

    NASA Astrophysics Data System (ADS)

    Fuhrer, A.; Fasth, C.; Samuelson, L.

    2007-07-01

    Closely spaced local gate electrodes are used to electrically define a double quantum dot along an InAs nanowire crystal. By applying a periodic pulse sequence to two plunger gate electrodes controlling the double quantum dot charge configuration, the device is operated as a single electron pump. The authors find that within measurement accuracy, the pumping current equals one electron per cycle for frequencies up to 2MHz, demonstrating the suitability of nanowire based quantum dots for pumping applications.

  16. QCAD simulation and optimization of semiconductor double quantum dots

    SciTech Connect

    Nielsen, Erik; Gao, Xujiao; Kalashnikova, Irina; Muller, Richard Partain; Salinger, Andrew Gerhard; Young, Ralph Watson

    2013-12-01

    We present the Quantum Computer Aided Design (QCAD) simulator that targets modeling quantum devices, particularly silicon double quantum dots (DQDs) developed for quantum qubits. The simulator has three di erentiating features: (i) its core contains nonlinear Poisson, e ective mass Schrodinger, and Con guration Interaction solvers that have massively parallel capability for high simulation throughput, and can be run individually or combined self-consistently for 1D/2D/3D quantum devices; (ii) the core solvers show superior convergence even at near-zero-Kelvin temperatures, which is critical for modeling quantum computing devices; (iii) it couples with an optimization engine Dakota that enables optimization of gate voltages in DQDs for multiple desired targets. The Poisson solver includes Maxwell- Boltzmann and Fermi-Dirac statistics, supports Dirichlet, Neumann, interface charge, and Robin boundary conditions, and includes the e ect of dopant incomplete ionization. The solver has shown robust nonlinear convergence even in the milli-Kelvin temperature range, and has been extensively used to quickly obtain the semiclassical electrostatic potential in DQD devices. The self-consistent Schrodinger-Poisson solver has achieved robust and monotonic convergence behavior for 1D/2D/3D quantum devices at very low temperatures by using a predictor-correct iteration scheme. The QCAD simulator enables the calculation of dot-to-gate capacitances, and comparison with experiment and between solvers. It is observed that computed capacitances are in the right ballpark when compared to experiment, and quantum con nement increases capacitance when the number of electrons is xed in a quantum dot. In addition, the coupling of QCAD with Dakota allows to rapidly identify which device layouts are more likely leading to few-electron quantum dots. Very efficient QCAD simulations on a large number of fabricated and proposed Si DQDs have made it possible to provide fast feedback for design

  17. Excited States in an InAs Nanowire Double Quantum Dot measured by Time-Resolved Charge Detection

    NASA Astrophysics Data System (ADS)

    Choi, Theodore; Shorubalko, Ivan; Gustavsson, Simon; Schön, Silke; Ensslin, Klaus

    2009-04-01

    We present real-time detection of single electrons in an InAs nanowire double quantum dot. Two self-aligned quantum point contacts in an underlying two-dimensional electron gas material serve as highly sensitive charge detectors for the double quantum dot. We examine the excitated states of the double quantum dot by finite bias spectroscopy. The excited states are characterized by measuring the tunneling-in and tunneling-out rates of the quantum dots.

  18. 1H and 13C MAS NMR analysis for the role of chemically inequivalent a-N(CH3)4 and b-N(CH3)4 ions in [N(CH3)4]2CuCl4

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2014-01-01

    The spin-lattice relaxation times in the laboratory frame, T1, and in the rotating frame, T1ρ, for 1H and 13C in [N(CH3)4]2CuCl4 were measured by static NMR and magic angle spinning (MAS) NMR as functions of temperature. The intensities of the 1H and 13C signals changed near phase transition temperatures TC1 and TC3, which indicated that N(CH3)4 plays an important role in these phase transitions. It was thus apparent that the T1 and T1ρ for 1H are governed by the same molecular motions. Two inequivalent ions, a-N(CH3)4 and b-N(CH3)4, were identified by 13C cross-polarization (CP)/MAS NMR. From these results, the behaviors of these two chemically inequivalent N(CH3)4 groups in the paraelastic and ferroelastic phases are discussed.

  19. Probing interband coulomb interactions in semiconductor nanostructures with 2D double-quantum coherence spectroscopy.

    PubMed

    Velizhanin, Kirill A; Piryatinski, Andrei

    2011-05-12

    Employing the interband exciton scattering model, we have derived a closed set of equations determining the 2D double-quantum coherence signal sensitive to the interband Coulomb interactions (i.e., many-body Coulomb interactions leading to the couplings between exciton and biexciton bands) in semiconductor nanostructures such as nanocrystals, quantum wires, wells, and carbon nanotubes. Our general analysis of 2D double-quantum coherence resonances has demonstrated that the interband Coulomb interactions lead to new cross-peaks whose appearance can be interpreted as a result of exciton and biexciton state mixing. The presence of the strongly coupled resonant states and weakly coupled background of off-resonant states can significantly simplify cross-peak analysis by eliminating the congested background spectrum. Our simulations of the 2D double-quantum coherence signal in PbSe NCs have validated this approach.

  20. Investigation of intermolecular double-quantum off-resonance longitudinal relaxation in the tilted rotating frame

    NASA Astrophysics Data System (ADS)

    Cai, Honghao; Zheng, Bingwen; Ke, Hanping; Chen, Zhong

    2015-11-01

    A modified correlation spectroscopy revamped by asymmetric z-gradients echo detection (CRAZED) sequence was applied to investigate the behavior of intermolecular double-quantum longitudinal relaxation processes in the tilted rotating frame. Theoretical formalism based on dipolar field theory was presented in detail. Spectroscopic measurements and quantitative analysis demonstrated that the signal intensities and intermolecular double-quantum off-resonance longitudinal relaxation time in the rotating frame (T1ρ, DQC eff) are inversely correlated with the tilt angle (θ), while positively correlated with the effective frequency of spin-locking field (ωe). Magnetic resonance imaging experiments of an agarose phantom also prove the validity of the theoretical analysis and demonstrated the feasibility of imaging based on T1ρ, DQC eff . The rotating-frame double-quantum relaxation measurements are useful for probing slow-motion molecules and this study provides the guidance for optimization of the spin-lock experiments.

  1. Controlled energy-selected electron capture and release in double quantum dots

    NASA Astrophysics Data System (ADS)

    Pont, Federico M.; Bande, Annika; Cederbaum, Lorenz S.

    2013-12-01

    Highly accurate quantum electron dynamics calculations demonstrate that energy can be efficiently transferred between quantum dots. Specifically, in a double quantum dot an incoming electron is captured by one dot and the excess energy is transferred to the neighboring dot and used to remove an electron from this dot. This process is due to long-range electron correlation and shown to be operative at rather large distances between the dots. The efficiency of the process is greatly enhanced by preparing the double quantum dot such that the incoming electron is initially captured by a two-electron resonance state of the system. In contrast to atoms and molecules in nature, double quantum dots can be manipulated to achieve this enhancement. This mechanism leads to a surprisingly narrow distribution of the energy of the electron removed in the process which is explained by resonance theory. We argue that the process could be exploited in practice.

  2. 27Al, 47,49Ti, 31P, and 13C MAS NMR Study of VX, GD, and HD Reactions with Nanosize Al2O3, Conventional Al2O3 and TiO2, and Aluminum and Titanium Metal

    DTIC Science & Technology

    2007-01-01

    reactions involved and peak assignments for titanophosphonate 3, Ti(m) and anatase (see text). 17568 J. Phys. Chem. C , Vol. 111, No. 47, 2007 Wagner et al...postulated to be Ti(O)[O2P(CH3)OPin]2, in agreement with elemental analysis. High-field 47,49Ti MAS NMR of anatase shows marked narrowing of its signals...Metal 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: Reactions of VX, GD, and HD with Al2O3, TiO2 ( anatase and rutile), aluminum, and titanium metal

  3. Few-hole double quantum dot in an undoped GaAs/AlGaAs heterostructure

    SciTech Connect

    Tracy, L. A.; Hargett, T. W.; Reno, J. L.

    2014-03-24

    We demonstrate a hole double quantum dot in an undoped GaAs/AlGaAs heterostructure. The interdot coupling can be tuned over a wide range, from formation of a large single dot to two well-isolated quantum dots. Using charge sensing, we show the ability to completely empty the dot of holes and control the charge occupation in the few-hole regime. The device should allow for control of individual hole spins in single and double quantum dots in GaAs.

  4. Ferromagnets-induced splitting of molecular states of T-shaped double quantum dots

    NASA Astrophysics Data System (ADS)

    Wójcik, Krzysztof P.

    2015-05-01

    The exchange field for molecular states of double quantum dot, induced by two ferromagnets coupled to the device in T-shaped configuration, is defined and calculated. It is found, that in the regime of strong coupling between quantum dots, the dependence of the exchange field on this coupling becomes nontrivial. In particular, it changes the sign a few times to eventually vanish in the limit of infinite inter-dot coupling. The excitation energies of double quantum dot are calculated and the results used to predict the conditions for suppression of the two-stage Kondo effect in the considered nanostructure.

  5. Exchange-Induced Spin Blockade in a Two-Electron Double Quantum Dot.

    PubMed

    Imanaka, D; Sharmin, S; Hashisaka, M; Muraki, K; Fujisawa, T

    2015-10-23

    We have experimentally identified the exchange-induced spin blockade in a GaAs double quantum dot. The transport is suppressed only when the eigenstates are well-defined singlet and triplet states, and thus sensitive to dynamic nuclear-spin polarization that causes singlet-triplet mixing. This gives rise to unusual current spectra, such as a sharp current dip and an asymmetric current profile near the triplet resonance of a double quantum dot. Numerical simulations suggest that the current dip is a signature of identical nuclear-spin polarization in the two dots, which is attractive for coherent spin manipulations in a material with nuclear spins.

  6. Donor–acceptor stacking arrangements in bulk and thin-film high-mobility conjugated polymers characterized using molecular modelling and MAS and surface-enhanced solid-state NMR spectroscopy† †Electronic supplementary information (ESI) available: Additional computational and experimental details, including the DNP sample preparation. See DOI: 10.1039/c7sc00053g Click here for additional data file.

    PubMed Central

    Chaudhari, Sachin R.; Broch, Katharina; Lesage, Anne; Lemaur, Vincent; Dudenko, Dmytro; Olivier, Yoann; Sirringhaus, Henning; Emsley, Lyndon; Grey, Clare P.

    2017-01-01

    Conjugated polymers show promising properties as cheap, sustainable and solution-processable semiconductors. A key challenge in the development of these materials is to determine the polymer chain structure, conformation and packing in both the bulk polymer and in thin films typically used in devices. However, many characterisation techniques are unable to provide atomic-level structural information owing to the presence of disorder. Here, we use molecular modelling, magic-angle spinning (MAS) and dynamic nuclear polarisation surface-enhanced NMR spectroscopy (DNP SENS) to characterise the polymer backbone group conformations and packing arrangement in the high-mobility donor–acceptor copolymer diketopyrrolo-pyrrole-dithienylthieno[3,2-b]thiophene (DPP-DTT). Using conventional 1H and 13C solid-state MAS NMR coupled with density functional theory calculations and molecular dynamics simulations, we find that the bulk polymer adopts a highly planar backbone conformation with a laterally-shifted donor-on-acceptor stacking arrangement. DNP SENS enables acquisition of 13C NMR data for polymer films, where sensitivity is limiting owing to small sample volumes. The DNP signal enhancement enables a two-dimensional 1H–13C HETCOR spectrum to be recorded for a drop-cast polymer film, and a 13C CPMAS NMR spectrum to be recorded for a spin-coated thin-film with a thickness of only 400 nm. The results show that the same planar backbone structure and intermolecular stacking arrangement is preserved in the films following solution processing and annealing, thereby rationalizing the favourable device properties of DPP-DTT, and providing a protocol for the study of other thin film materials. PMID:28507688

  7. Structure in solid state of 3,3‧-diindolylmethane derivatives, potent cytotoxic agents against human tumor cells, followed X-ray diffraction and 13C CP/MAS NMR analyses

    NASA Astrophysics Data System (ADS)

    Maciejewska, Dorota; Wolska, Irena; Niemyjska, Maria; Żero, Paweł

    2005-10-01

    The 5,5'-disubstituted-3,3'-diindolylmethanes 1, 2 have been prepared and their structure was analyzed by X-ray and NMR techniques. The X-ray diffraction studies revealed interesting C-H⋯ π intermolecular interactions which may play role in characterization of their biological features. In 1H and 13C NMR spectra in solution and in 13C CPMAS NMR spectra in solid state only a single pattern of signals was observed. Both compounds reduce the growth of MCF7 (breast), NCI-H460 (lung), and SF-268 (NCS) cells dramatically.

  8. Refocused double-quantum editing for lactate detection at 7 T.

    PubMed

    Boer, Vincent O; Luijten, Peter R; Klomp, Dennis W J

    2013-01-01

    Lactate is an important marker for anaerobic glucose metabolism, and it is therefore of particular interest in, for example, cerebral ischemia, skeletal muscle disorders, and in the monitoring of oncology treatments. However, the in vivo detection of lactate with magnetic resonance spectroscopy is complicated by the overlap of the low-intensity lactate methyl resonance with lipid signal. Therefore, double-quantum filters have been employed to dephase the overlapping lipid signal, as they allow for a very high lipid suppression efficiency. For reliable lactate detection in lipid-rich environment, very large crushing gradients have to be employed to dephase the lipid signal under the noise level. Double-quantum filters are generally associated with signal loss of the metabolite of interest. For lactate, half of the signal is lost by selecting either the double- or the zero-quantum coherences. Moreover, owing to incomplete refocusing, traditional double-quantum filters with very large crusher gradients exhibit additional loss of the already low-lactate signal. In this study, a refocused double-quantum filter is described, which does not suffer from this source of additional signal loss. Therefore, it becomes possible to detect lactate at lower concentrations, or in lipid-rich environments. Lactate measurements are shown in the human calf muscle at 7 T.

  9. In vivo detection of GABA in human brain using a localized double-quantum filter technique.

    PubMed

    Keltner, J R; Wald, L L; Frederick, B D; Renshaw, P F

    1997-03-01

    A proton MR spectral editing technique employing a spatially localized, double-quantum filter (DQF) was used to measure gamma-aminobutyric acid (GABA) in the human brain at 1.5 T. The double-quantum method provided robust, single-shot suppression of uncoupled resonances from choline, creatine, and NAA and allowed detection of the gamma CH2 GABA (3.0 ppm) resonance with 30% efficiency. Spatial localization of the GABA measurement was achieved by incorporating PRESS localization within the double-quantum excitation and detection sequence. A calibration technique was developed to adjust the relative phases of the RF pulses to maximize the in vivo double-quantum detection efficiency for an arbitrary voxel location. The sequence efficiency, degree of suppression of uncoupled reasonances, and characterization of the in vivo DQF technique was examined in phantom experiments and in a study of the occipital lobe of 10 normal subjects. The ratio of the 3.0-ppm GABA resonance to the 3.0-ppm creatine resonance was found to be 0.20 +/- 0.05 (SD).

  10. Ultra-low temperature MAS-DNP

    NASA Astrophysics Data System (ADS)

    Lee, Daniel; Bouleau, Eric; Saint-Bonnet, Pierre; Hediger, Sabine; De Paëpe, Gaël

    2016-03-01

    Since the infancy of NMR spectroscopy, sensitivity and resolution have been the limiting factors of the technique. Regular essential developments on this front have led to the widely applicable, versatile, and powerful spectroscopy that we know today. However, the Holy Grail of ultimate sensitivity and resolution is not yet reached, and technical improvements are still ongoing. Hence, high-field dynamic nuclear polarization (DNP) making use of high-frequency, high-power microwave irradiation of electron spins has become very promising in combination with magic angle sample spinning (MAS) solid-state NMR experiments. This is because it leads to a transfer of the much larger polarization of these electron spins under suitable irradiation to surrounding nuclei, greatly increasing NMR sensitivity. Currently, this boom in MAS-DNP is mainly performed at minimum sample temperatures of about 100 K, using cold nitrogen gas to pneumatically spin and cool the sample. This Perspective deals with the desire to improve further the sensitivity and resolution by providing "ultra"-low temperatures for MAS-DNP, using cryogenic helium gas. Different designs on how this technological challenge has been overcome are described. It is shown that stable and fast spinning can be attained for sample temperatures down to 30 K using a large cryostat developed in our laboratory. Using this cryostat to cool a closed-loop of helium gas brings the additional advantage of sample spinning frequencies that can greatly surpass those achievable with nitrogen gas, due to the differing fluidic properties of these two gases. It is shown that using ultra-low temperatures for MAS-DNP results in substantial experimental sensitivity enhancements and according time-savings. Access to this temperature range is demonstrated to be both viable and highly pertinent.

  11. Quantum Entanglement in Double Quantum Systems and Jaynes-Cummings Model.

    PubMed

    Jakubczyk, Paweł; Majchrowski, Klaudiusz; Tralle, Igor

    2017-12-01

    In the paper, we proposed a new approach to producing the qubits in electron transport in low-dimensional structures such as double quantum wells or double quantum wires (DQW). The qubit could arise as a result of quantum entanglement of two specific states of electrons in DQW structure. These two specific states are the symmetric and antisymmetric (with respect to inversion symmetry) states arising due to tunneling across the structure, while entanglement could be produced and controlled by means of the source of nonclassical light. We examined the possibility to produce quantum entanglement in the framework of Jaynes-Cummings model and have shown that at least in principle, the entanglement can be achieved due to series of "revivals" and "collapses" in the population inversion due to the interaction of a quantized single-mode EM field with a two-level system.

  12. Charge Sensed Pauli Blockade in a Metal–Oxide–Semiconductor Lateral Double Quantum Dot

    SciTech Connect

    Nguyen, Khoi T.; Lilly, Michael P.; Nielsen, Erik; Bishop, Nathan; Rahman, Rajib; Young, Ralph; Wendt, Joel; Dominguez, Jason; Pluym, Tammy; Stevens, Jeffery; Lu, Tzu-Ming; Muller, Richard; Carroll, Malcolm S.

    2013-12-11

    We report Pauli blockade in a multielectron silicon metal–oxide–semiconductor double quantum dot with an integrated charge sensor. The current is rectified up to a blockade energy of 0.18 ± 0.03 meV. The blockade energy is analogous to singlet–triplet splitting in a two electron double quantum dot. Built-in imbalances of tunnel rates in the MOS DQD obfuscate some edges of the bias triangles. A method to extract the bias triangles is described, and a numeric rate-equation simulation is used to understand the effect of tunneling imbalances and finite temperature on charge stability (honeycomb) diagram, in particular the identification of missing and shifting edges. A bound on relaxation time of the triplet-like state is also obtained from this measurement.

  13. Coherent tunneling through a double quantum dot coupled to Majorana bound states

    NASA Astrophysics Data System (ADS)

    Ivanov, T. I.

    2017-07-01

    We consider a double quantum dot coupled to a one-dimensional superconducting quantum wire with Majorana bound states at the ends of the wire. We compute the conductance of the double dot in the coherent tunneling regime. When only one of the dots is coupled to one Majorana bound state the conductance is enhanced/diminished in the vicinity of zero voltage if it has minimum/maximum at this voltage with no Majorana bound state and has two local maximums/minimums at voltage equal plus or minus the Majorana bound states overlapping energy. When each dot is coupled to one Majorana bound state with zero overlapping energy it is possible by tuning the magnetic flux through the system to change the zero-voltage conductance from minimum to local maximum. We show that when both electron levels in the double quantum dot are below the right chemical potential the Fano resonance occurs only for the lower energy level.

  14. In-plane magneto-plasmons in grating gated double quantum well field effect transistors.

    SciTech Connect

    Simmons, Jerry Alvon; Wanke, Michael Clement; Peralta, Xomalin G.; Lilly, Michael Patrick; Allen, S. James; Reno, John Louis; Burke, Peter J.; Eisenstein, James Philip

    2003-06-01

    Coupled double quantum well field-effect transistors with a grating gate exhibit a terahertz ({approx}600 GHz) photoconductive response that resonates with standing two dimensional plasma oscillations under the gate and may be the basis for developing a fast, tunable terahertz detector. The application of a precisely aligned in-plane magnetic field produces no detectable change in the device DC conductance but produces a dramatic inversion, growth of the terahertz photoconductive response and frequency shift of the standing plasmon resonances. The frequency shift can be described by a significant mass increase produced by the in-plane field. The mass increase is substantially larger than that calculated from a single well and we presume that a proper treatment of the coupled double quantum well may resolve this discrepancy.

  15. Tunable few-electron double quantum dots with integrated charge read-out

    NASA Astrophysics Data System (ADS)

    Elzerman, J. M.; Hanson, R.; Greidanus, J. S.; Willems van Beveren, L. H.; De Franceschi, S.; Vandersypen, L. M. K.; Tarucha, S.; Kouwenhoven, L. P.

    2004-11-01

    We report on the realization of few-electron double quantum dots defined in a two-dimensional electron gas by means of surface gates on top of a GaAs/AlGaAs heterostructure. Two quantum point contacts (QPCs) are placed in the vicinity of the double quantum dot and serve as charge detectors. These enable determination of the number of conduction electrons on each dot. This number can be reduced to zero, while still allowing transport measurements through the double dot. The coupling between the two dots can be controlled even in the few-electron regime. Microwave radiation is used to pump an electron from one dot to the other by absorption of a single photon. The experiments demonstrate that this quantum dot circuit can serve as a good starting point for a scalable spin-qubit system.

  16. Lateral p -n Junction in an Inverted InAs /GaSb Double Quantum Well

    NASA Astrophysics Data System (ADS)

    Karalic, Matija; Mittag, Christopher; Tschirky, Thomas; Wegscheider, Werner; Ensslin, Klaus; Ihn, Thomas

    2017-05-01

    We present transport measurements on a lateral p -n junction in an inverted InAs /GaSb double quantum well at zero and nonzero perpendicular magnetic fields. At a zero magnetic field, the junction exhibits diodelike behavior in accordance with the presence of a hybridization gap. With an increasing magnetic field, we explore the quantum Hall regime where spin-polarized edge states with the same chirality are either reflected or transmitted at the junction, whereas those of opposite chirality undergo a mixing process, leading to full equilibration along the width of the junction independent of spin. These results lay the foundations for using p -n junctions in InAs /GaSb double quantum wells to probe the transition between the topological quantum spin Hall and quantum Hall states.

  17. New double quantum coherence filter for localized detection of glutathione in vivo.

    PubMed

    Zhao, Tiejun; Heberlein, Keith; Jonas, Carolyn; Jones, Dean P; Hu, Xiaoping

    2006-03-01

    In this work, a new double quantum filter for glutathione (GSH) editing is introduced, combined with the point-resolved spectroscopy localization sequence (PRESS), and demonstrated in vivo. Compared to the conventional double quantum coherence filter, the new filter has two major advantages. First, it eliminates the need for calibration scans for optimizing the signal yield, making it more efficient and convenient for routine use. Second, it removes the influence of water saturation pulses on the GSH yield, further improving its accuracy. With this method, GSH concentrations in the left and right parietal lobes of five healthy volunteers were determined to be 0.91+/-0.16 mM and 0.89+/-0.16 mM, respectively, in agreement with previous studies.

  18. Dynamic control of coherent pulses via Fano-type interference in asymmetric double quantum wells

    SciTech Connect

    Wu Jinhui; Gao Jinyue; Xu Jihua; Silvestri, L.; La Rocca, G. C.; Bassani, F.; Artoni, M.

    2006-05-15

    We study the temporal and spatial dynamics of two light pulses, a probe and a switch, propagating through an asymmetric double quantum well where tunneling-induced quantum interference may be observed. When such an interference takes place, in the absence of the switch, the quantum well is transparent to the probe which propagates over sufficiently long distances at very small group velocities. In the presence of a relatively strong switch, however, the probe pulse is absorbed due to the quenching of tunneling-induced quantum interference. The probe may be made to vanish even when switch and probe are somewhat delayed with respect to one another. Conversely, our asymmetric double quantum well may be rendered either opaque or transparent to the switch pulse. Such a probe-switch 'reciprocity' can be used to devise a versatile all-optical quantum interference-based solid-state switch for optical communication devices.

  19. Charge sensed Pauli blockade in a metal-oxide-semiconductor lateral double quantum dot.

    PubMed

    Nguyen, Khoi T; Lilly, Michael P; Nielsen, Erik; Bishop, Nathan; Rahman, Rajib; Young, Ralph; Wendt, Joel; Dominguez, Jason; Pluym, Tammy; Stevens, Jeffery; Lu, Tzu-Ming; Muller, Richard; Carroll, Malcolm S

    2013-01-01

    We report Pauli blockade in a multielectron silicon metal-oxide-semiconductor double quantum dot with an integrated charge sensor. The current is rectified up to a blockade energy of 0.18 ± 0.03 meV. The blockade energy is analogous to singlet-triplet splitting in a two electron double quantum dot. Built-in imbalances of tunnel rates in the MOS DQD obfuscate some edges of the bias triangles. A method to extract the bias triangles is described, and a numeric rate-equation simulation is used to understand the effect of tunneling imbalances and finite temperature on charge stability (honeycomb) diagram, in particular the identification of missing and shifting edges. A bound on relaxation time of the triplet-like state is also obtained from this measurement.

  20. Impurity-related nonlinear optical rectification in double quantum dot under electric field

    NASA Astrophysics Data System (ADS)

    Bejan, D.

    2016-11-01

    The characteristics of donor-impurity-related nonlinear optical rectification in asymmetric double quantum dot under electric field are investigated within the compact density-matrix formalism and the effective mass approximation. The results show that: (i) the binding energy of the ground state varies strongly with the impurity position and it is raised or decreased by the applied field, depending on the impurity position; (ii) the optical rectification spectra are rather sensitive to the impurity position and the electric field intensity; (iii) the changes in the impurity position within the double quantum dot and the electric field value may induce red or blue shift of the resonant peaks of the nonlinear optical rectification.

  1. Phonon-assisted gain in a semiconductor double quantum dot maser.

    PubMed

    Gullans, M J; Liu, Y-Y; Stehlik, J; Petta, J R; Taylor, J M

    2015-05-15

    We develop a microscopic model for the recently demonstrated double-quantum-dot maser. In characterizing the gain of this device we find that, in addition to the direct stimulated emission of photons, there is a large contribution from the simultaneous emission of a photon and a phonon, i.e., the phonon sideband. We show that this phonon-assisted gain typically dominates the overall gain, which leads to masing. Recent experimental data are well fit with our model.

  2. Charge sensing of a few-donor double quantum dot in silicon

    SciTech Connect

    Watson, T. F. Weber, B.; Büch, H.; Fuechsle, M.; Simmons, M. Y.

    2015-12-07

    We demonstrate the charge sensing of a few-donor double quantum dot precision placed with atomic resolution scanning tunnelling microscope lithography. We show that a tunnel-coupled single electron transistor (SET) can be used to detect electron transitions on both dots as well as inter-dot transitions. We demonstrate that we can control the tunnel times of the second dot to the SET island by ∼4 orders of magnitude by detuning its energy with respect to the first dot.

  3. Two-Dimensional Double-Quantum Spectra Reveal Collective Resonances in an Atomic Vapor

    PubMed Central

    Dai, Xingcan; Richter, Marten; Li, Hebin; Bristow, Alan D.; Falvo, Cyril; Mukamel, Shaul; Cundiff, Steven T.

    2013-01-01

    We report the observation of double-quantum coherence signals in a gas of potassium atoms at twice the frequency of the one-quantum coherences. Since a single atom does not have a state at the corresponding energy, this observation must be attributed to a collective resonance involving multiple atoms. These resonances are induced by weak interatomic dipole-dipole interactions, which means that the atoms cannot be treated in isolation, even at a low density of 1012 cm−3. PMID:23003037

  4. Charge sensing of a few-donor double quantum dot in silicon

    NASA Astrophysics Data System (ADS)

    Watson, T. F.; Weber, B.; Büch, H.; Fuechsle, M.; Simmons, M. Y.

    2015-12-01

    We demonstrate the charge sensing of a few-donor double quantum dot precision placed with atomic resolution scanning tunnelling microscope lithography. We show that a tunnel-coupled single electron transistor (SET) can be used to detect electron transitions on both dots as well as inter-dot transitions. We demonstrate that we can control the tunnel times of the second dot to the SET island by ˜4 orders of magnitude by detuning its energy with respect to the first dot.

  5. Numerical Solutions and Structures of Double Quantum Jet Solving by an Upwind Scheme

    NASA Astrophysics Data System (ADS)

    Lin, San-Yih

    2005-11-01

    The solutions of a double quantum jet are analyzed by solving the quantum fluid dynamical formulation (QFD) of the Schr"odinger equation. The QFD equations are obtained by expressing the Schr"odinger wave function as =ρ^1/2(iS/)and u=(u,v). In QFD, Q=-ρ-1/2δρ^1/2 is called as quantum potential. An upwind method is developed to solve the QFD equations. The method use a third-order upwind method to discrete convection terms and the central finite difference method to discrete the quantum potential. A fourth-order Runge-Kutta method is used for time marching. Two cases, one-dimensional free particle with external potential and two-dimensional free particle with external potential, are presented to illustrate the accuracy of the QFD solver. The computational results are compared well with the results obtained by solving the Schr"odinger equation. Finally, the QFD solver is applied to solve the solutions of a double quantum jet and to investigate its structures. First, a mathematical formulation is derived to describe the double quantum jet. The jet has the probability density equals 2 and the velocity equals 2 at the inlet of the jet. Then, the solutions are computed by the QFD solver. The structures of the solutions are affected by the strength of the quantum potential. The interesting phenomena of quantum clustering are found.

  6. (13)C NMR Metabolomics: INADEQUATE Network Analysis.

    PubMed

    Clendinen, Chaevien S; Pasquel, Christian; Ajredini, Ramadan; Edison, Arthur S

    2015-06-02

    The many advantages of (13)C NMR are often overshadowed by its intrinsically low sensitivity. Given that carbon makes up the backbone of most biologically relevant molecules, (13)C NMR offers a straightforward measurement of these compounds. Two-dimensional (13)C-(13)C correlation experiments like INADEQUATE (incredible natural abundance double quantum transfer experiment) are ideal for the structural elucidation of natural products and have great but untapped potential for metabolomics analysis. We demonstrate a new and semiautomated approach called INETA (INADEQUATE network analysis) for the untargeted analysis of INADEQUATE data sets using an in silico INADEQUATE database. We demonstrate this approach using isotopically labeled Caenorhabditis elegans mixtures.

  7. Measurement of temporal correlations of the overhauser field in a double quantum dot.

    PubMed

    Reilly, D J; Taylor, J M; Laird, E A; Petta, J R; Marcus, C M; Hanson, M P; Gossard, A C

    2008-12-05

    In quantum dots made from materials with nonzero nuclear spins, hyperfine coupling creates a fluctuating effective Zeeman field (Overhauser field) felt by electrons, which can be a dominant source of spin qubit decoherence. We characterize the spectral properties of the fluctuating Overhauser field in a GaAs double quantum dot by measuring correlation functions and power spectra of the rate of singlet-triplet mixing of two separated electrons. Away from zero field, spectral weight is concentrated below 10 Hz, with approximately 1/f2 dependence on frequency f. This is consistent with a model of nuclear spin diffusion, and indicates that decoherence can be largely suppressed by echo techniques.

  8. Spin bottleneck in resonant tunneling through double quantum dots with different Zeeman splittings.

    PubMed

    Huang, S M; Tokura, Y; Akimoto, H; Kono, K; Lin, J J; Tarucha, S; Ono, K

    2010-04-02

    We investigated the electron transport property of the InGaAs/GaAs double quantum dots, the electron g factors of which are different from each other. We found that in a magnetic field, the resonant tunneling is suppressed even if one of the Zeeman sublevels is aligned. This is because the other misaligned Zeeman sublevels limit the total current. A finite broadening of the misaligned sublevel partially relieves this bottleneck effect, and the maximum current is reached when interdot detuning is half the Zeeman energy difference.

  9. Two-electron double quantum dot coupled to coherent photon and phonon fields

    NASA Astrophysics Data System (ADS)

    Sato, Yuya; Chen, Jason C. H.; Hashisaka, Masayuki; Muraki, Koji; Fujisawa, Toshimasa

    2017-09-01

    Two-electron states of a double quantum dot (DQD) under irradiation of coherent boson (photon and phonon) fields are studied by measuring spin-flip tunneling current in the Pauli spin blockade regime. This measurement scheme allows us to investigate Rabi splitting and associated boson dressed states particularly in the deep dispersive regime where the detuning δ ≡ℏ ω -EAB between the boson energy ℏ ω and energy spacing EAB of the two-level system is significantly large (δ ˜ℏ ω ), where the permanent dipole moment in the DQD plays a significant role in the hybridization.

  10. Out-of-phase Andreev transports in a double-quantum-dot Cooper-pair splitter

    SciTech Connect

    Gong, Wei-Jiang Wang, Xiao-Qi; Zhu, Yu-Lian; Gao, Zhen; Wu, Hai-Na

    2016-06-07

    We investigate the Andreev transports through a double-quantum-dot Cooper-pair splitter with an additional direct coupling between the dots. It is found that when finite magnetic flux is applied through this structure, its induced phase adjusts the local and crossed Andreev reflections in different manners. Moreover, in the presence of appropriate magnetic flux, the crossed Andreev reflection can be efficiently enhanced, accompanied by the suppression of the local Andreev reflection. Such a result exists in both the linear and nonlinear transport regions, even in the case of strong intradot Coulomb interaction. Therefore, such a work provides a promising scheme to enhance the splitting of the Cooper pair.

  11. The electronic properties of concentric double quantum ring and possibility designing XOR gate

    NASA Astrophysics Data System (ADS)

    AL-Badry, Lafy. F.

    2017-03-01

    In this paper I have investigated the Aharonov-Bohm oscillation in concentric double quantum ring. The outer ring attached to leads while the inner ring only tunnel-coupled to the outer ring. The effect of inner ring on electron transport properties through outer ring studied and found that the conductance spectrum consists of two types of oscillations. One is the normal Aharonov-Bohm oscillation, and other is a small oscillations superposed above AB oscillation. The AB oscillation utilized to designing nanoscale XOR gate by choosing the magnetic flux and tuning the gate voltages which realization XOR gate action.

  12. Effect of spin-flip scattering on the electron transport through double quantum dots

    NASA Astrophysics Data System (ADS)

    Yang, Fu-Bin; Huang, Rui; Cheng, Yan

    2015-05-01

    We systematically investigate the electron transport through double quantum dots (DQD) with particular emphasis on the spin-flip scattering of an electron in the DQD. By means of the slave-boson mean-field approximation, we calculate the linear conductance and the transmission in the Kondo regime at zero temperature. The obtained results show that both the linear conductance and transmission probability are quite sensitive to the spin-flip strength when the DQD structure is changed among the serial, parallel and T-shaped. It is suggested that such a theoretical model can be used to study the physical phenomenon related to the spin manipulation transport.

  13. InSb nanowire double quantum dots coupled to a superconducting microwave cavity

    NASA Astrophysics Data System (ADS)

    Wang, R.; Deacon, R. S.; Car, D.; Bakkers, E. P. A. M.; Ishibashi, K.

    2016-05-01

    By employing a micrometer precision mechanical transfer technique, we embed individual InSb nanowires into a superconducting coplanar waveguide resonator. We investigate the characteristics of a double quantum dot formed in an InSb nanowire interacting with a single mode microwave field. The charge stability diagram can be obtained from the amplitude and phase response of the resonator independently from the dc transport measurement. As the charge transits between dot-dot, or dot-lead, the change of resonator transmission is compared and the charge-cavity coupling strength is extracted to be in the magnitude of several MHz.

  14. Preparing and preserving the double quantum coherence in NV- centers in Diamond at low fields

    NASA Astrophysics Data System (ADS)

    Moussa, Osama; Hincks, Ian; Cory, David G.

    2014-12-01

    We present and demonstrate a simple idea to excite and preserve the double-quantum-coherence (DQC) in the ground state of the electron spin of the Nitrogen-vacancy (NV) color center in diamond. We measure the coherence time of the DQC and compare it to the single quantum coherence time, both, in a Ramsey fringe experiment and under a Hahn echo sequence. We also demonstrate a robust pulse sequence based on the DANTE pulse sequence for selectively isolating the signal from the electron transitions conditional on the state of the always-present Nitrogen spin.

  15. Fabrication and characterization of p-channel Si double quantum dots

    SciTech Connect

    Yamada, Ko; Kambara, Tomohiro; Oda, Shunri; Kodera, Tetsuo

    2014-09-15

    Lithographically defined p-channel Si single hole transistors (SHTs) and double quantum dot (DQD) devices are fabricated and characterized. Coulomb oscillations are clearly evident at a temperature of 4.2 K. The charging energy and the diameter of the SHT are estimated from the Coulomb diamonds. Honeycomb-like charge stability diagrams are observed from measurements of the DQD devices. Single hole transitions through the DQD are detected using an integrated SHT as a charge sensor, and a few-hole regime of the DQD is observed.

  16. Multistability and spin diffusion enhanced lifetimes in dynamic nuclear polarization in a double quantum dot

    NASA Astrophysics Data System (ADS)

    Forster, F.; Mühlbacher, M.; Schuh, D.; Wegscheider, W.; Giedke, G.; Ludwig, S.

    2015-12-01

    The control of nuclear spins in quantum dots is essential to explore their many-body dynamics and exploit their prospects for quantum information processing. We present a unique combination of dynamic nuclear spin polarization and electric-dipole-induced spin resonance in an electrostatically defined double quantum dot (DQD) exposed to the strongly inhomogeneous field of two on-chip nanomagnets. Our experiments provide direct and unrivaled access to the nuclear spin polarization distribution and allow us to establish and characterize multiple fixed points. Further, we demonstrate polarization of the DQD environment by nuclear spin diffusion which significantly stabilizes the nuclear spins inside the DQD.

  17. Quantum confinement of a hydrogenic donor in a double quantum well: Through diamagnetic susceptibility

    SciTech Connect

    Vignesh, G.; Nithiananthi, P.

    2015-06-24

    Diamagnetic susceptibility of a randomly distributed donor in a GaAs/Al{sub 0.3}Ga{sub 0.7}As Double Quantum Well has been calculated in its ground state as a function of barrier and well width. It is shown that the modification in the barrier and well dimension significantly influences the dimensional character of the donor through modulating the subband distribution and in turn the localization of the donor. The effect of barrier and well thickness on the interparticle distance has also been observed. Interestingly it opens up the possibility of tuning the susceptibility and monitoring the tunnel coupling among the wells.

  18. Spectral properties of a double-quantum-dot structure: A causal Green's function approach

    NASA Astrophysics Data System (ADS)

    You, J. Q.; Zheng, Hou-Zhi

    1999-09-01

    Spectral properties of a double quantum dot (QD) structure are studied by a causal Green's function (GF) approach. The double QD system is modeled by an Anderson-type Hamiltonian in which both the intra- and interdot Coulomb interactions are taken into account. The GF's are derived by an equation-of-motion method and the real-space renormalization-group technique. The numerical results show that the average occupation number of electrons in the QD exhibits staircase features and the local density of states depends appreciably on the electron occupation of the dot.

  19. Tunneling relaxation of holes in double quantum wells with nonideal heteroboundaries

    SciTech Connect

    Vas`ko, F.T.; Raichev, O.E.

    1995-09-01

    This paper presents a calculation of the tunneling relaxation rate of holes in double quantum wells when the holes are scattered at heteroboundary roughnesses. Because of mixing of the light- and heavy-hole states (which are described analytically in the approximation of strongly differing effective masses), the interwell tunneling mechanism changes at the splitting energy of the tunnel-coupled levels increases. The dependence of the tunneling relaxation rate on the splitting energy is compared with the experimental results. 7 refs., 2 figs.

  20. Electromagnetically induced transparency in an asymmetric double quantum well under non-resonant, intense laser fields

    NASA Astrophysics Data System (ADS)

    Niculescu, E. C.

    2017-02-01

    Electromagnetically induced transparency in an asymmetric double quantum well subjected to a non-resonant, intense laser field is theoretically investigated. We found that the energy levels configuration could be switched between a Λ-type and a ladder-type scheme by varying the non-resonant radiation intensity. This effect is due to the laser-induced electron tunneling between the wells and it allows a substantial flexibility in the manipulation of the optical properties. The dependence of the susceptibilities on the control field Rabi frequency, intensity of the nonresonant laser, and the control field detuning for both configurations are discussed and compared.

  1. Double quantum coherence electron spin resonance on coupled Cu(II)-Cu(II) electron spins

    NASA Astrophysics Data System (ADS)

    Becker, James S.; Saxena, Sunil

    2005-10-01

    We demonstrate for the first time the ability to generate double quantum coherences (DQCs) for the case of Cu(II). We show that small splittings (˜7 MHz) from the Cu(II)-Cu(II) electron-electron magnetic dipolar interaction can be reliably resolved even though the inhomogeneously broadened Cu(II) linewidth is ˜2 GHz. A Cu(II)-Cu(II) distance of 2.0 nm was measured on a model peptide system, thus, demonstrating that distances on the nanometer scale may be measured using DQC electron spin resonance (ESR).

  2. Multi-bit dark state memory: Double quantum dot as an electronic quantum memory

    NASA Astrophysics Data System (ADS)

    Aharon, Eran; Pozner, Roni; Lifshitz, Efrat; Peskin, Uri

    2016-12-01

    Quantum dot clusters enable the creation of dark states which preserve electrons or holes in a coherent superposition of dot states for a long time. Various quantum logic devices can be envisioned to arise from the possibility of storing such trapped particles for future release on demand. In this work, we consider a double quantum dot memory device, which enables the preservation of a coherent state to be released as multiple classical bits. Our unique device architecture uses an external gating for storing (writing) the coherent state and for retrieving (reading) the classical bits, in addition to exploiting an internal gating effect for the preservation of the coherent state.

  3. Effects of intersubband interaction on multisubband electron transport in single and double quantum wells

    NASA Astrophysics Data System (ADS)

    Hai, G.-Q.; Studart, N.; Marques, G. E.; Peeters, F. M.; Koenraad, P. M.

    1998-07-01

    The multisubband electron transport properties are studied for doped single quantum well and gated double asymmetric quantum well structures. The effects due to intersubband interaction and screening of the ionized impurity scattering are also investigated. We show that intersubband coupling plays an essential role in describing the screening properties as well as the effect of ionized impurity scattering on the mobility in a doped single quantum well. For coupled double quantum well structures, negative transconductance is found theoretically which is due to resonant tunneling between the two quantum wells.

  4. Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

    SciTech Connect

    Chen, Yuan; Deng, Li; Chen, Aixi

    2015-02-15

    We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.

  5. InSb nanowire double quantum dots coupled to a superconducting microwave cavity

    SciTech Connect

    Wang, R.; Deacon, R. S. Ishibashi, K.; Car, D.; Bakkers, E. P. A. M.

    2016-05-16

    By employing a micrometer precision mechanical transfer technique, we embed individual InSb nanowires into a superconducting coplanar waveguide resonator. We investigate the characteristics of a double quantum dot formed in an InSb nanowire interacting with a single mode microwave field. The charge stability diagram can be obtained from the amplitude and phase response of the resonator independently from the dc transport measurement. As the charge transits between dot-dot, or dot-lead, the change of resonator transmission is compared and the charge-cavity coupling strength is extracted to be in the magnitude of several MHz.

  6. Sisyphus Thermalization of Photons in a Cavity-Coupled Double Quantum Dot

    NASA Astrophysics Data System (ADS)

    Gullans, M. J.; Stehlik, J.; Liu, Y.-Y.; Eichler, C.; Petta, J. R.; Taylor, J. M.

    2016-07-01

    We investigate the nonclassical states of light that emerge in a microwave resonator coupled to a periodically driven electron in a nanowire double quantum dot (DQD). Under certain drive configurations, we find that the resonator approaches a thermal state at the temperature of the surrounding substrate with a chemical potential given by a harmonic of the drive frequency. Away from these thermal regions we find regions of gain and loss, where the system can lase, or regions where the DQD acts as a single-photon source. These effects are observable in current devices and have broad utility for quantum optics with microwave photons.

  7. Double quantum well states in Cu/Co/Cu grown on Co(001)

    NASA Astrophysics Data System (ADS)

    Ling, W. L.; Rotenberg, Eli; Choi, H. J.; Wolfe, J. H.; Toyama, F.; Paik, Silena; Smith, N. V.; Qiu, Z. Q.

    2002-03-01

    A double quantum well (QW) system of Cu/Co(1 ML)/Cu grown on Co/Cu(001) has been investigated by photoemission spectroscopy. Energy spectra of the valence band from one of the Cu QW's have been measured as a function of the other Cu QW thickness. The results show strong resonance between the two Cu QW states across a 1 ML Co barrier. In particular, we observe that quantum well coupling removes the degeneracy of the two Cu QW states, resulting in a state crossing effect. A phase accumulation model is developed to explain these observations.

  8. Vibrational effects in charge transport through a molecular double quantum dot

    NASA Astrophysics Data System (ADS)

    Sowa, Jakub K.; Mol, Jan A.; Briggs, G. Andrew D.; Gauger, Erik M.

    2017-02-01

    Recent progress in the field of molecular electronics has revealed the fundamental importance of the coupling between the electronic degrees of freedom and specific vibrational modes. Considering the examples of a molecular dimer and a carbon nanotube double quantum dot, we here theoretically investigate transport through a two-site system that is strongly coupled to a single vibrational mode. Using a quantum master equation approach, we demonstrate that, depending on the relative positions of the two dots, electron-phonon interactions can lead to negative differential conductance and suppression of the current through the system. We also discuss the experimental relevance of the presented results and possible implementations of the studied system.

  9. Fluctuation theorem for a double quantum dot coupled to a point-contact electrometer

    SciTech Connect

    Golubev, D.; Utsumi, Y.; Marthaler, M.; Schön, G.

    2013-12-04

    Motivated by recent experiments on the real-time single-electron counting through a semiconductor GaAs double quantum dot (DQD) by a nearby quantum point contact (QPC), we develop the full-counting statistics of coupled DQD and QPC system. By utilizing the time-scale separation between the dynamics of DQD and QPC, we derive the modified master equation with tunneling rates depending on the counting fields, which fulfill the detailed fluctuation theorem. Furthermore, we derive universal relations between the non-linear corrections to the current and noise, which can be verified in experiments.

  10. Sisyphus Thermalization of Photons in a Cavity-Coupled Double Quantum Dot

    PubMed Central

    Gullans, M. J.; Stehlik, J.; Liu, Y.-Y.; Eichler, C.; Petta, J. R.; Taylor, J. M.

    2016-01-01

    We investigate the non-classical states of light that emerge in a microwave resonator coupled to a periodically-driven electron in a nanowire double quantum dot (DQD). Under certain drive configurations, we find that the resonator approaches a thermal state at the temperature of the surrounding substrate with a chemical potential given by a harmonic of the drive frequency. Away from these thermal regions we find regions of gain and loss, where the system can lase, or regions where the DQD acts as a single-photon source. These effects are observable in current devices and have broad utility for quantum optics with microwave photons. PMID:27517784

  11. Stability of excitons in double quantum well: Through electron and holes transmission probabilities

    NASA Astrophysics Data System (ADS)

    Vignesh, G.; Nithiananthi, P.

    2017-05-01

    Stability of excitons has been analyzed using the transmission probability of its constituent particles in GaAs/Al0.3Ga0.7As Double Quantum Well (DQW) structure by varying well and barrier layer thickness. The effective mass approximation is used and anisotropy in material properties are also considered to get realistic situations. It is observed that tuning barrier layer avails many resonance peaks for the transmission and tuning well width admits maximum transmission at narrow well widths. Every saddle point of the observed transmission coefficients decides the formation, strength and transportation of excitons in DQW.

  12. Structural investigation of α-LaZr2F11 by coupling X-ray powder diffraction, 19F solid state NMR and DFT calculations

    NASA Astrophysics Data System (ADS)

    Martineau, Charlotte; Legein, Christophe; Body, Monique; Péron, Olivier; Boulard, Brigitte; Fayon, Franck

    2013-03-01

    α-LaZr2F11 has been synthesized by solid state reaction. Its crystal structure has been refined from X-ray powder diffraction data (space group no. 72 Ibam, a=7.785(1) Å, b=10.086(1) Å and c=11.102(1) Å). α-LaZr2F11 contains one La, one Zr and four F inequivalent crystallographic sites. F3 and F4 are shared between one ZrF73- polyhedron and one LaF85- polyhedron, while F1 and F2 bridge two ZrF73- polyhedra. 19F 1D MAS NMR spectra of α-LaZr2F11 are in agreement with the proposed structural model. Assignment of the 19F resonances to the corresponding crystallographic sites has been performed on the basis of both their relative intensities and their correlation patterns in a 19F 2D dipolar-based double-quantum recoupling MAS NMR spectrum. DFT calculations of the 19F chemical shielding tensors have been performed using the GIPAW method implemented in the NMR-CASTEP code, for the experimental structure and two PBE-DFT geometry optimized structures of α-LaZr2F11 (atomic position optimization and full geometry optimization with rescaling of the unit cell volume to the experimental value). Computations were done with and without using a modified La pseudopotential allowing the treatment of the 4f localized empty orbitals of La3+. A relatively nice agreement between the experimental 19F isotropic and anisotropic chemical shifts and the values calculated for the proposed structural model is obtained.

  13. Modifications under irradiation of a self-assembled monolayer grafted on a nano-porous silica glass: a solid-state NMR characterization

    SciTech Connect

    Le Caer, S.; Chatelain, C.; Renault, J.Ph.; Brunet, F.; Charpentier, T.; Durand, D.; Dauvois, V.

    2012-02-15

    Controlled pore glasses with a pore size of 8 nm are grafted with chlorodimethylsilane (ClSi(CH{sub 3}){sub 2}H). The surface of the glass is carefully characterized before and after irradiation with 10 MeV electrons by solid-state NMR measurements. {sup 1}H MAS NMR experiments in one and two dimensions (2D double quantum and 2D exchange) have been used to reveal the grafting of the chlorodimethylsilane at the silica surface and evidence the formation of a homogeneous layer on the surface. Irradiation leads to a high H{sub 2} yield (3.3 * 10{sup -7} mol/J) due to the efficient cleavage of the Si H bond. Methane is detected in smaller quantities (5.5 * 10{sup -8} mol/J), indicating that the Si-H bond is preferentially cleaved over the Si-C bond. The H{sub 2} production arising from OH groups on the surface is very minor in comparison to the S- H and Si-C radiolysis. (authors)

  14. Anisotropic Pauli Spin Blockade of Holes in a GaAs Double Quantum Dot.

    PubMed

    Wang, Daisy Q; Klochan, Oleh; Hung, Jo-Tzu; Culcer, Dimitrie; Farrer, Ian; Ritchie, David A; Hamilton, Alex R

    2016-12-14

    Electrically defined semiconductor quantum dots are attractive systems for spin manipulation and quantum information processing. Heavy-holes in both Si and GaAs are promising candidates for all-electrical spin manipulation, owing to the weak hyperfine interaction and strong spin-orbit interaction. However, it has only recently become possible to make stable quantum dots in these systems, mainly due to difficulties in device fabrication and stability. Here, we present electrical transport measurements on holes in a gate-defined double quantum dot in a GaAs/AlxGa1-xAs heterostructure. We observe clear Pauli spin blockade and demonstrate that the lifting of this spin blockade by an external magnetic field is highly anisotropic. Numerical calculations of heavy-hole transport through a double quantum dot in the presence of strong spin-orbit coupling show quantitative agreement with experimental results and suggest that the observed anisotropy can be explained by both the anisotropic effective hole g-factor and the surface Dresselhaus spin-orbit interaction.

  15. Pauli Spin Blockade in a Highly Tunable Silicon Double Quantum Dot

    PubMed Central

    Lai, N. S.; Lim, W. H.; Yang, C. H.; Zwanenburg, F. A.; Coish, W. A.; Qassemi, F.; Morello, A.; Dzurak, A. S.

    2011-01-01

    Double quantum dots are convenient solid-state platforms to encode quantum information. Two-electron spin states can be detected and manipulated using quantum selection rules based on the Pauli exclusion principle, leading to Pauli spin blockade of electron transport for triplet states. Coherent spin states would be optimally preserved in an environment free of nuclear spins, which is achievable in silicon by isotopic purification. Here we report on a deliberately engineered, gate-defined silicon metal-oxide-semiconductor double quantum dot system. The electron occupancy of each dot and the inter-dot tunnel coupling are independently tunable by electrostatic gates. At weak inter-dot coupling we clearly observe Pauli spin blockade and measure a large intra-dot singlet-triplet splitting > 1 meV. The leakage current in spin blockade has a peculiar magnetic field dependence, unrelated to electron-nuclear effects and consistent with the effect of spin-flip cotunneling processes. The results obtained here provide excellent prospects for realising singlet-triplet qubits. PMID:22355627

  16. Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane.

    PubMed

    Knapp, T J; Mohr, R T; Li, Yize Stephanie; Thorgrimsson, Brandur; Foote, Ryan H; Wu, Xian; Ward, Daniel R; Savage, D E; Lagally, M G; Friesen, Mark; Coppersmith, S N; Eriksson, M A

    2016-04-15

    We report the fabrication and characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. In the past, all gate-defined quantum dots in Si/SiGe heterostructures were formed on top of strain-graded virtual substrates. The strain grading process necessarily introduces misfit dislocations into a heterostructure, and these defects introduce lateral strain inhomogeneities, mosaic tilt, and threading dislocations. The use of a SiGe nanomembrane as the virtual substrate enables the strain relaxation to be entirely elastic, eliminating the need for misfit dislocations. However, in this approach the formation of the heterostructure is more complicated, involving two separate epitaxial growth procedures separated by a wet-transfer process that results in a buried non-epitaxial interface 625 nm from the quantum dot. We demonstrate that in spite of this buried interface in close proximity to the device, a double quantum dot can be formed that is controllable enough to enable tuning of the inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of an applied magnetic field.

  17. Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

    NASA Astrophysics Data System (ADS)

    Knapp, T. J.; Mohr, R. T.; Li, Yize Stephanie; Thorgrimsson, Brandur; Foote, Ryan H.; Wu, Xian; Ward, Daniel R.; Savage, D. E.; Lagally, M. G.; Friesen, Mark; Coppersmith, S. N.; Eriksson, M. A.

    2016-04-01

    We report the fabrication and characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. In the past, all gate-defined quantum dots in Si/SiGe heterostructures were formed on top of strain-graded virtual substrates. The strain grading process necessarily introduces misfit dislocations into a heterostructure, and these defects introduce lateral strain inhomogeneities, mosaic tilt, and threading dislocations. The use of a SiGe nanomembrane as the virtual substrate enables the strain relaxation to be entirely elastic, eliminating the need for misfit dislocations. However, in this approach the formation of the heterostructure is more complicated, involving two separate epitaxial growth procedures separated by a wet-transfer process that results in a buried non-epitaxial interface 625 nm from the quantum dot. We demonstrate that in spite of this buried interface in close proximity to the device, a double quantum dot can be formed that is controllable enough to enable tuning of the inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of an applied magnetic field.

  18. Tunable double quantum dots in InAs nanowires defined by local gate electrodes.

    NASA Astrophysics Data System (ADS)

    Fasth, Carina; Fuhrer, Andreas; Samuelson, Lars

    2006-03-01

    We present low-temperature transport measurements on quantum dots induced in homogeneous InAs quantum wires 50 nm in diameter. Quantum dots are induced by electrical depletion of the wire using local gate electrodes with down to 30 nm electrode spacing. This scheme has permitted the realization of fully gate-defined multiple quantum dots along the nanowire [1]. Tunability in double quantum dots is a prerequisite for the system to be operated as a quantum gate. We demonstrate control over the lead tunnel barrier transparencies and, in the case of double quantum dots, the interdot coupling. Using the local gate electrodes also as plunger gates we measure double dot honeycomb stability diagrams which show the transition from a single large dot to two weakly coupled dots at 4.2K. The induced quantum dots can be tuned into the few-electron regime which is shown from Coulomb blockade measurements. We extract values of orbital energy-level spacings, capacitances and capacitive and tunnel interdot coupling for this system. [1] C. Fasth et al., NanoLett 5, 1487 (2005).

  19. Pauli spin blockade in a highly tunable silicon double quantum dot.

    PubMed

    Lai, N S; Lim, W H; Yang, C H; Zwanenburg, F A; Coish, W A; Qassemi, F; Morello, A; Dzurak, A S

    2011-01-01

    Double quantum dots are convenient solid-state platforms to encode quantum information. Two-electron spin states can be detected and manipulated using quantum selection rules based on the Pauli exclusion principle, leading to Pauli spin blockade of electron transport for triplet states. Coherent spin states would be optimally preserved in an environment free of nuclear spins, which is achievable in silicon by isotopic purification. Here we report on a deliberately engineered, gate-defined silicon metal-oxide-semiconductor double quantum dot system. The electron occupancy of each dot and the inter-dot tunnel coupling are independently tunable by electrostatic gates. At weak inter-dot coupling we clearly observe Pauli spin blockade and measure a large intra-dot singlet-triplet splitting > 1 meV. The leakage current in spin blockade has a peculiar magnetic field dependence, unrelated to electron-nuclear effects and consistent with the effect of spin-flip cotunneling processes. The results obtained here provide excellent prospects for realising singlet-triplet qubits.

  20. Strong spin Seebeck effect in Kondo T-shaped double quantum dots

    NASA Astrophysics Data System (ADS)

    Wójcik, K. P.; Weymann, I.

    2017-02-01

    We investigate, taking a theoretical approach, the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot strongly coupled to two ferromagnetic leads, focusing on the transport regime in which the system exhibits the two-stage Kondo effect. We study the dependence of the (spin) Seebeck coefficient, the corresponding power factor and the figure of merit on temperature, leads’ spin polarization and dot level position. We show that the thermal conductance fulfills a modified Wiedemann-Franz law, also in the regime of suppression of subsequent stages of the Kondo effect by the exchange field resulting from the presence of ferromagnets. Moreover, we demonstrate that the spin thermopower is enhanced at temperatures corresponding to the second stage of Kondo screening. Very interestingly, the spin-thermoelectric response of the system is found to be highly sensitive to the spin polarization of the leads. In some cases spin polarization of the order of 1% is sufficient for a strong spin Seebeck effect to occur. This is explained as a consequence of the interplay between the two-stage Kondo effect and the exchange field induced in the double quantum dot. Due to the possibility of tuning the exchange field by the choice of gate voltage, the spin thermopower may also be tuned to be maximal for desired spin polarization of the leads. All calculations are performed with the aid of the numerical renormalization group technique.

  1. Strong spin Seebeck effect in Kondo T-shaped double quantum dots.

    PubMed

    Wójcik, K P; Weymann, I

    2017-02-08

    We investigate, taking a theoretical approach, the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot strongly coupled to two ferromagnetic leads, focusing on the transport regime in which the system exhibits the two-stage Kondo effect. We study the dependence of the (spin) Seebeck coefficient, the corresponding power factor and the figure of merit on temperature, leads' spin polarization and dot level position. We show that the thermal conductance fulfills a modified Wiedemann-Franz law, also in the regime of suppression of subsequent stages of the Kondo effect by the exchange field resulting from the presence of ferromagnets. Moreover, we demonstrate that the spin thermopower is enhanced at temperatures corresponding to the second stage of Kondo screening. Very interestingly, the spin-thermoelectric response of the system is found to be highly sensitive to the spin polarization of the leads. In some cases spin polarization of the order of 1% is sufficient for a strong spin Seebeck effect to occur. This is explained as a consequence of the interplay between the two-stage Kondo effect and the exchange field induced in the double quantum dot. Due to the possibility of tuning the exchange field by the choice of gate voltage, the spin thermopower may also be tuned to be maximal for desired spin polarization of the leads. All calculations are performed with the aid of the numerical renormalization group technique.

  2. Charge Dynamics and Spin Blockade in a Hybrid Double Quantum Dot in Silicon

    NASA Astrophysics Data System (ADS)

    Urdampilleta, Matias; Chatterjee, Anasua; Lo, Cheuk Chi; Kobayashi, Takashi; Mansir, John; Barraud, Sylvain; Betz, Andreas C.; Rogge, Sven; Gonzalez-Zalba, M. Fernando; Morton, John J. L.

    2015-07-01

    Electron spin qubits in silicon, whether in quantum dots or in donor atoms, have long been considered attractive qubits for the implementation of a quantum computer because of silicon's "semiconductor vacuum" character and its compatibility with the microelectronics industry. While donor electron spins in silicon provide extremely long coherence times and access to the nuclear spin via the hyperfine interaction, quantum dots have the complementary advantages of fast electrical operations, tunability, and scalability. Here, we present an approach to a novel hybrid double quantum dot by coupling a donor to a lithographically patterned artificial atom. Using gate-based rf reflectometry, we probe the charge stability of this double quantum-dot system and the variation of quantum capacitance at the interdot charge transition. Using microwave spectroscopy, we find a tunnel coupling of 2.7 GHz and characterize the charge dynamics, which reveals a charge T2* of 200 ps and a relaxation time T1 of 100 ns. Additionally, we demonstrate a spin blockade at the inderdot transition, opening up the possibility to operate this coupled system as a singlet-triplet qubit or to transfer a coherent spin state between the quantum dot and the donor electron and nucleus.

  3. Spin-polarized conductance in double quantum dots with ferromagnetic contacts

    NASA Astrophysics Data System (ADS)

    Weymann, Ireneusz; Wojcik, Krzysztof

    2014-03-01

    We study the transport properties of double quantum dots in T-shape geometry strongly coupled to external ferromagnetic contacts. The analysis is performed with the aid of the numerical renormalization group method, which allows us to study the behavior of respective spectral functions and the linear conductance through the system in the full parameter space of the model. The considered device enables a unique possibility to explore the interplay of the Fano and Kondo effects with ferromagnetic-contact induced exchange field. We show that the presence of gate-tunable exchange field leads to strong dependence of the spin polarization of conductance on the position of the dot levels. By tuning the level of the decoupled dot, the conductance may become fully spin polarized. Moreover, when changing the dot level positions, one can also tune the sign of the spin polarization. The increased spin polarization of the conductance is a consequence of a subtle interplay between the interference effects, the Kondo effect and the exchange field. Double quantum dots with ferromagnetic contacts can be thus considered as efficient spin current sources, where the degree of spin polarization can be tuned by purely electrical means, without the necessity to apply external magnetic field. We acknowledge support from the project No. IP2011 059471 and the EU grant No. CIG-303 689.

  4. Solvent signal suppression for high-resolution MAS-DNP

    NASA Astrophysics Data System (ADS)

    Lee, Daniel; Chaudhari, Sachin R.; De Paëpe, Gaël

    2017-05-01

    Dynamic nuclear polarization (DNP) has become a powerful tool to substantially increase the sensitivity of high-field magic angle spinning (MAS) solid-state NMR experiments. The addition of dissolved hyperpolarizing agents usually results in the presence of solvent signals that can overlap and obscure those of interest from the analyte. Here, two methods are proposed to suppress DNP solvent signals: a Forced Echo Dephasing experiment (FEDex) and TRAnsfer of Populations in DOuble Resonance Echo Dephasing (TRAPDORED) NMR. These methods reintroduce a heteronuclear dipolar interaction that is specific to the solvent, thereby forcing a dephasing of recoupled solvent spins and leaving acquired NMR spectra free of associated resonance overlap with the analyte. The potency of these methods is demonstrated on sample types common to MAS-DNP experiments, namely a frozen solution (of L-proline) and a powdered solid (progesterone), both containing deuterated glycerol as a DNP solvent. The proposed methods are efficient, simple to implement, compatible with other NMR experiments, and extendable past spectral editing for just DNP solvents. The sensitivity gains from MAS-DNP in conjunction with FEDex or TRAPDORED then permits rapid and uninterrupted sample analysis.

  5. Singlet-triplet electron spin qubit in Si/SiGe double quantum dot

    NASA Astrophysics Data System (ADS)

    Wu, Xian

    In this thesis, we study the electronic properties of devices made from Si/SiGe heterostructures and demonstrate universal control of a two-electron spin qubit in a double quantum dot. First, we introduce the basic concepts of a quantum bit (qubit), which is the fundamental building block of a quantum computer. We choose to use electron spin states in a solid state device as the hardware for implementing a qubit. The solid state device is made in a Si/SiGe heterostructure, in which a two dimensional electron gas (2DEG) forms at the interface of a Si layer and a SiGe layer at cryogenic temperatures. Metal gates are patterned on top of the heterostrucutres to confine electrons in the two lateral directions. We characterize the material by fabricating Hall bars and performing magnetotransport measurements on those Hall bars to extract the carrier density and mobility of the 2DEG formed in each material. We study the surface effects of modulation doped heterostructures on the 2DEG formed underneath and demonstrate that the quality of the surface affects the property of the buried 2DEG in a Si/SiGe heterostructure. In a double quantum dot, the spin singlet state and the spin-zero triplet state of two electrons can be used as the qubit basis states. The energy difference between singlet and triplet states induces rotations about the Z axis in the Bloch sphere. The difference in magnetic field DeltaB between the two sides of the double dot, arising from the coupling to the nuclear spins in the host material, drives singlet-triplet state rotation about the X axis in the Blochsphere. X rotation is poor because this nuclear Delta B is unstable. We fabricate a Si/SiGe double quantum dot with an integrated micromagnet, which generates a larger and more stable Delta B to improve X rotation. Using this DeltaB, we demonstrate coherent rotation of the qubit's Bloch vector about two different axes of the Bloch sphere. The inhomogeneous spin coherence time T 2* is determined. We

  6. Efficient dipolar double quantum filtering under magic angle spinning without a 1H decoupling field

    NASA Astrophysics Data System (ADS)

    Courtney, Joseph M.; Rienstra, Chad M.

    2016-08-01

    We present a systematic study of dipolar double quantum (DQ) filtering in 13C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n ⩾ 7, provided that the 13C nutation frequency is on the order of 100 kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between 13C and 1H fields. For 13C nutation frequencies greater than 75 kHz, optimal performance is observed without an applied 1H field. At spinning rates exceeding 20 kHz, symmetry conditions as low as n = 3 were found to perform adequately.

  7. Entanglement of two-electron spin states in a double quantum dot

    NASA Astrophysics Data System (ADS)

    Bagrov, V. G.; Gitman, D. M.; Levin, A. D.; Meireles, M. S.

    Recently, an implementation of a universal set of one- and two-quantum-bit gates for quantum computation using spin states of coupled single-electron quantum dots was proposed. It was demonstrated that it is possible to execute a coherent control of a quantum system based on two-electron spin states in a double quantum dot, allowing state preparation, coherent manipulation, and projective readout. This possibility is based on rapid electrical control of the spin exchange interaction. These results motivated us to develop a formal theoretical study of the corresponding model of two coupled spins placed in a magnetic field and subjected to a time-dependent mutual Heisenberg interaction. Using possible exact solutions of the corresponding quantum problem, we study entangling of different separable initial states in this model. It is demonstrated that the entanglement due to a time-dependent Heisenberg interaction is dominating in comparison with the entanglement due to the action of an external magnetic field.

  8. Simultaneous Spectral Editing for γ-Aminobutyric Acid and Taurine Using Double Quantum Coherence Transfer

    NASA Astrophysics Data System (ADS)

    Lei, Hao; Peeling, James

    2000-03-01

    Conventional double quantum (DQ) editing techniques recover resonances of one metabolite at a time and are thus inefficient for monitoring metabolic changes involving several metabolites. A DQ coherence transfer double editing sequence using a dual-band DQ coherence read pulse is described here. The sequence permits simultaneous spectral editing for two metabolites with similar J coupling constants in a single scan. Simultaneous editing for taurine and γ-aminobutyric acid (GABA) is demonstrated using solution phantoms and rat brain tissue. Selectivity of the double editing sequence for the target metabolites is as good as that achieved using conventional DQ editing which selects each metabolite individually. With experimental parameters of the double editing sequence chosen to optimize GABA editing, the sensitivity for GABA detection is the same as that with GABA editing only, while the sensitivity for taurine detection is decreased slightly compared to that with taurine editing only.

  9. Transient negative photoconductance in a charge transfer double quantum well under optical intersubband excitation

    NASA Astrophysics Data System (ADS)

    Rüfenacht, M.; Tsujino, S.; Sakaki, H.

    1998-06-01

    Recently, it was shown that an electron-hole radiative recombination is induced by a mid-infrared light exciting an intersubband transition in a charge transfer double quantum well (CTDQW). This recombination was attributed to an upstream transfer of electrons from an electron-rich well to a hole-rich well. In this study, we investigated the electrical response of a CTDQW under intersubband optical excitation, and found that a positive photocurrent, opposite in sign and proportional to the applied electric field, accompanies the intersubband-transition-induced luminescence (ITIL) signal. A negative photocurrent component was also observed and attributed to heating processes. This work brings a further evidence of the ITIL process and shows that an important proportion of the carriers are consumed by the transfer of electrons.

  10. Detector-induced backaction on the counting statistics of a double quantum dot

    PubMed Central

    Li, Zeng-Zhao; Lam, Chi-Hang; Yu, Ting; You, J. Q.

    2013-01-01

    Full counting statistics of electron transport is of fundamental importance for a deeper understanding of the underlying physical processes in quantum transport in nanoscale devices. The backaction effect from a detector on the nanoscale devices is also essential due to its inevitable presence in experiments. Here we investigate the backaction of a charge detector in the form of a quantum point contact (QPC) on the counting statistics of a biased double quantum dot (DQD). We show that this inevitable QPC-induced backaction can have profound effects on the counting statistics under certain conditions, e.g., changing the shot noise from being sub-Poissonian to super-Poissonian, and changing the skewness from being positive to negative. Also, we show that both Fano factor and skewness can be either enhanced or suppressed by increasing the energy difference between two single-dot levels of the DQD under the detector-induced backaction. PMID:24149587

  11. Control over hysteresis curves and thresholds of optical bistability in different semiconductor double quantum wells

    NASA Astrophysics Data System (ADS)

    H, R. Hamedi; M, R. Mehmannavaz; Hadi, Afshari

    2015-08-01

    The effects of optical field on the phenomenon of optical bistability (OB) are investigated in a K-type semiconductor double quantum well (SDQW) under various parametric conditions. It is shown that the OB threshold can be manipulated by increasing the intensity of coupling field. The dependence of the shift of OB hysteresis curve on probe wavelength detuning is then explored. In order to demonstrate controllability of the OB in this SDQW, we compare the OB features of three different configurations which could arise in this SDQW scheme, i.e., K-type, Y-type, and inverted Y-type systems. The controllability of this semiconductor nanostructure medium makes the presented OB scheme more valuable for applications in all-optical switches, information storage, and logic circuits of all optical information processing. Project supported by the Lithuanian Research Council (Grant No. VP1-3.1-ŠM-01-V-03-001).

  12. Controlled high-fidelity navigation in the charge stability diagram of a double quantum dot.

    PubMed

    Coden, Diego S Acosta; Romero, Rodolfo H; Räsänen, Esa

    2015-03-25

    We propose an efficient control protocol for charge transfer in a double quantum dot. We consider numerically a two-dimensional model system, where the quantum dots are subjected to time-dependent electric fields corresponding to experimental gate voltages. Our protocol enables navigation in the charge stability diagram from a state to another through controllable variation of the fields. We show that the well-known adiabatic Landau-Zener transition-when supplemented with a time-dependent field tailored with optimal control theory-can remarkably improve the transition speed. The results also lead to a simple control scheme obtained from the experimental charge stability diagram that requires only a single parameter. Eventually, we can achieve the ultrafast performance of the composite pulse protocol that allows the system to be driven at the quantum speed limit.

  13. Cavity-photon-switched coherent transient transport in a double quantum waveguide

    SciTech Connect

    Abdullah, Nzar Rauf Gudmundsson, Vidar; Tang, Chi-Shung; Manolescu, Andrei

    2014-12-21

    We study a cavity-photon-switched coherent electron transport in a symmetric double quantum waveguide. The waveguide system is weakly connected to two electron reservoirs, but strongly coupled to a single quantized photon cavity mode. A coupling window is placed between the waveguides to allow electron interference or inter-waveguide transport. The transient electron transport in the system is investigated using a quantum master equation. We present a cavity-photon tunable semiconductor quantum waveguide implementation of an inverter quantum gate, in which the output of the waveguide system may be selected via the selection of an appropriate photon number or “photon frequency” of the cavity. In addition, the importance of the photon polarization in the cavity, that is, either parallel or perpendicular to the direction of electron propagation in the waveguide system is demonstrated.

  14. Magnetic breakdown and Landau level spectra of a tunable double-quantum-well Fermi surface

    SciTech Connect

    Simmons, J.A.; Harff, N.E.; Lyo, S.K.; Klem, J.F.; Boebinger, G.S.; Pfeiffer, L.N.; West, K.W.

    1997-12-31

    By measuring longitudinal resistance, the authors map the Landau level spectra of double quantum wells as a function of both parallel (B{sub {parallel}}) and perpendicular (B{sub {perpendicular}}) magnetic fields. In this continuously tunable highly non-parabolic system, the cyclotron masses of the two Fermi surface orbits change in opposite directions with B{sub {parallel}}. This causes the two corresponding ladders of Landau levels formed at finite B{sub {perpendicular}} to exhibit multiple crossings. They also observe a third set of landau levels, independent of B{sub {parallel}}, which arise from magnetic breakdown of the Fermi surface. Both semiclassical and full quantum mechanical calculations show good agreement with the data.

  15. THz Acoustic Spectroscopy by using Double Quantum Wells and Ultrafast Optical Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wei, Fan Jun; Yeh, Yu-Hsiang; Sheu, Jinn-Kong; Lin, Kung-Hsuan

    2016-06-01

    GaN is a pivotal material for acoustic transducers and acoustic spectroscopy in the THz regime, but its THz phonon properties have not been experimentally and comprehensively studied. In this report, we demonstrate how to use double quantum wells as a THz acoustic transducer for measuring generated acoustic phonons and deriving a broadband acoustic spectrum with continuous frequencies. We experimentally investigated the sub-THz frequency dependence of acoustic attenuation (i.e., phonon mean-free paths) in GaN, in addition to its physical origins such as anharmonic scattering, defect scattering, and boundary scattering. A new upper limit of attenuation caused by anharmonic scattering, which is lower than previously reported values, was obtained. Our results should be noteworthy for THz acoustic spectroscopy and for gaining a fundamental understanding of heat conduction.

  16. Noise spectrum of quantum transport through double quantum dots: Renormalization and non-Markovian effects

    NASA Astrophysics Data System (ADS)

    Shi, Pengqin; Hu, Menghan; Ying, Yaofeng; Jin, Jinshuang

    2016-09-01

    Based on the time-nonlocal particle number-resolved master equation, we investigate the sequential electron transport through the interacting double quantum dots. Our calculations show that there exists the effect of energy renormalization in the dispersion of the bath interaction spectrum and it is sensitive to the the bandwidth of the bath. This effect would strongly affect the stationary current and its zero-frequency shot noise for weak inter-dot coherent coupling strength, but for strong inter-dot coupling regime, it is negligible due to the strong intrinsic Rabi coherent dynamics. Moreover, the possible observable effects of the energy renormalization in the noise spectrum are also investigated through the Rabi coherence signal. Finally, the non-Markovian effect is manifested in the finite-frequency noise spectrum with the appearance of quasisteps, and the magnitude of these quasisteps are modified by the dispersion function.

  17. Phase control of light propagation via Fano interference in asymmetric double quantum wells

    SciTech Connect

    Yang, Wen-Xing; Lu, Jia-Wei; Zhou, Zhi-Kang; Yang, Long; Lee, Ray-Kuang

    2014-05-28

    We investigate the light propagation and dynamical control of a weak pulsed probe field in asymmetric double quantum wells via Fano interference, which is caused by tunneling from the excited subbands to the same continuum. Our results show that the system can produce anomalous and normal dispersion regions with negligible absorption by choosing appropriate coupling strength of the tunneling and the Fano interference. Interesting enough, the dispersion can be switched between normal and anomalous by adjusting the relative phase between the pulsed probe and coherent control fields owing to the existence of the perfectly Fano interference. Thus, the relative phase can be regarded as a switch to manipulate light propagation with subluminal or superluminal. The temporal and spatial dynamics of the pulsed probe field with hyperbolic secant envelope are analyzed.

  18. Infra-red tunneling absorption in semiconductor double quantum wells in tilted magnetic fields

    SciTech Connect

    Lyo, S.K.

    1996-12-31

    Using a linear response theory, interwell-tunneling absorption is calculated in a double-quantum-well structure with a wide center barrier in tilted magnetic fields. Tunneling absorption of infra-red photons occurs between the ground sublevels of the two quantum wells, with an energy difference that is tunable. In zero magnetic field, the absorption intensity decreases significantly as the linewidth increases with temperature. The absorption also depends strongly on the carrier densities of the wells. In magnetic fields, both the in-plane and perpendicular components of the field sensitively control and tune the absorption lineshape in very different ways, affecting the absorption threshold, the resonance energy of absorption, and the linewidth.

  19. Magnetoresistance of One-Dimensional Subbands in Tunnel-Coupled Double Quantum Wires

    SciTech Connect

    Blount, M.A.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.

    1999-04-27

    We study the low-temperature in-plane magnetoresistance of tunnel-coupled quasi-one-dimensional quantum wires. The wires are defined by two pairs of mutually aligned split gates on opposite sides of a < 1 micron thick AlGaAs/GaAs double quantum well heterostructure, allowing independent control of their widths. In the ballistic regime, when both wires are defined and the field is perpendicular to the current, a large resistance peak at ~6 Tesla is observed with a strong gate voltage dependence. The data is consistent with a counting model whereby the number of subbands crossing the Fermi level changes with field due to the formation of an anticrossing in each pair of 1D subbands.

  20. Nuclear spin dynamics in double quantum dots: Multistability, dynamical polarization, criticality, and entanglement

    NASA Astrophysics Data System (ADS)

    Schuetz, M. J. A.; Kessler, E. M.; Vandersypen, L. M. K.; Cirac, J. I.; Giedke, G.

    2014-05-01

    We theoretically study the nuclear spin dynamics driven by electron transport and hyperfine interaction in an electrically defined double quantum dot in the Pauli-blockade regime. We derive a master-equation-based framework and show that the coupled electron-nuclear system displays an instability towards the buildup of large nuclear spin polarization gradients in the two quantum dots. In the presence of such inhomogeneous magnetic fields, a quantum interference effect in the collective hyperfine coupling results in sizable nuclear spin entanglement between the two quantum dots in the steady state of the evolution. We investigate this effect using analytical and numerical techniques, and demonstrate its robustness under various types of imperfections.

  1. Effects of electric field and structure on the electromagnetically induced transparency in double quantum dot

    NASA Astrophysics Data System (ADS)

    Bejan, D.

    2017-05-01

    We theoretically investigated the effects of electric field and structural parameters of the confining potential on the optical properties of a GaAs/AlGaAs double quantum dot related to the occurrence of the electromagnetically induced transparency phenomenon, using the compact density-matrix formalism and the effective mass approximation. The dependences of the absorption coefficient, refraction index and light group velocity on the Rabi frequency of the control field, intensity of the static electric field, asymmetry parameter of the potential and dot dimension are discussed in detail. It is found that electromagnetically induced transparency occurs in the system for intermediate field values and its transparency window for probe field absorption and sub- and super-luminal frequency interval of the probe field are blueshifted by the increment of the electric field strength and dot dimension but are redshifted by the augment of the asymmetry parameter of the potential.

  2. Magnetic-field-induced charge redistribution in disordered graphene double quantum dots

    NASA Astrophysics Data System (ADS)

    Chiu, K. L.; Connolly, M. R.; Cresti, A.; Griffiths, J. P.; Jones, G. A. C.; Smith, C. G.

    2015-10-01

    We have studied the transport properties of a large graphene double quantum dot under the influence of a background disorder potential and a magnetic field. At low temperatures, the evolution of the charge-stability diagram as a function of the B field is investigated up to 10 T. Our results indicate that the charging energy of the quantum dot is reduced, and hence the effective size of the dot increases at a high magnetic field. We provide an explanation of our results using a tight-binding model, which describes the charge redistribution in a disordered graphene quantum dot via the formation of Landau levels and edge states. Our model suggests that the tunnel barriers separating different electron/hole puddles in a dot become transparent at high B fields, resulting in the charge delocalization and reduced charging energy observed experimentally.

  3. Large spin figure of merit in a double quantum dot coupled to noncollinear ferromagnetic electrodes.

    PubMed

    Zheng, Jun; Chi, Feng; Guo, Yong

    2012-07-04

    The spin thermoelectric effects are studied in a Rashba double quantum dot (QD) attached to ferromagnetic leads with noncollinear magnetic moments. The spin conductance G(s), spin thermopower S(s), electron thermal conductance κ(el) and spin thermoelectric figure of merit Z(s)T are calculated by using Green's function method. We find that the magnitude of the spin figure of merit can be remarkably enhanced by the coexistence of the Rashba spin-orbit interaction in the QDs and the leads' spin polarization, and can reach even as high as 3 by optimizing the parameters of the structure. The angle between the leads' magnetic moments can act as a powerful means to manipulate the properties of the spin figure of merit.

  4. Spin-resolved bunching and noise characteristics in double quantum dots coupled to ferromagnetic electrodes.

    PubMed

    Luo, JunYan; Jiao, HuJun; Xiong, BiTao; He, Xiao-Ling; Wang, Changrong

    2013-04-17

    We study spin-resolved noise in Coulomb blockaded double quantum dots coupled to ferromagnetic electrodes. The modulation of the interdot coupling and spin polarization in the electrodes gives rise to an intriguing dynamical spin ↑-↑ (↓-↓) blockade mechanism: bunching of up (down) spins due to dynamical blockade of an up (down) spin. In contrast to the conventional dynamical spin ↑-↓ bunching (bunching of up spins associated with a dynamical blockade of a down spin), this new bunching behavior is found to be intimately associated with the spin mutual-correlation, i.e. the noise fluctuation between opposite spin currents. We further demonstrate that the dynamical spin ↑-↑ and ↑-↓ bunching of tunneling events may be coexistent in the regime of weak interdot coupling and low spin polarization.

  5. Spin filtering and quantum phase transition in double quantum dots attached to spin-polarized leads.

    PubMed

    Wang, Wei-zhong

    2011-05-20

    We study the spin filtering and quantum phase transition (QPT) in double quantum dots attached to spin-polarized leads. For spin-independent leads, we observe a Kosterlitz-Thouless transition between the local triplet and doublet. For spin-polarized leads, the above QPT becomes first order, and Kondo splitting, gate-controlled spin reversal and a perfect spin filtering are observed. The breaking of spin-rotation SU(2) symmetry and the interdot transport mediated by the conduction electron are responsible for the fully spin-polarized conductance. Because spin-polarized leads suppress the Kondo effect, in order to obtain a large conductance with perfect spin filtering, one should choose leads with small spin polarization, such as Rashba spin-orbital coupling leads.

  6. Quantum efficiency of a single microwave photon detector based on a semiconductor double quantum dot

    NASA Astrophysics Data System (ADS)

    Wong, Clement H.; Vavilov, Maxim G.

    2017-01-01

    Motivated by recent interest in implementing circuit quantum electrodynamics with semiconducting quantum dots, we consider a double quantum dot (DQD) capacitively coupled to a superconducting resonator that is driven by the microwave field of a superconducting transmission line. We analyze the DQD current response using input-output theory and show that the resonator-coupled DQD is a sensitive microwave single photon detector. Using currently available experimental parameters of DQD-resonator coupling and dissipation, including the effects of 1 /f charge noise and phonon noise, we determine the parameter regime for which incident photons are completely absorbed and near-unit ≳98 % efficiency can be achieved. We show that this regime can be reached by using very high quality resonators with quality factor Q ≃105 .

  7. Spin-valley resolved photon-assisted tunneling in carbon nanotube double quantum dots

    NASA Astrophysics Data System (ADS)

    Osika, E. N.; Szafran, B.

    2017-05-01

    We consider photon-assisted tunneling (PAT) and the Landau-Zener-Stueckelberg (LZS) interference for double quantum dots induced electrostatically along a semiconducting carbon nanotube. An atomistic tight-binding approach and the time-dependent configuration-interaction method are employed to describe systems of a few confined electrons and holes. We reproduce the patterns of the LZS interference recently observed for quantum double dots describing transport across hole-localized states. Moreover, we indicate that for charge configurations for which the ground state is Pauli-blocked, PAT can be used for resolution of the transitions that involve spin-flip or intervalley transitions without the spin-valley conserving background signal.

  8. Implications of simultaneous requirements for low-noise exchange gates in double quantum dots

    NASA Astrophysics Data System (ADS)

    Nielsen, Erik; Young, Ralph W.; Muller, Richard P.; Carroll, M. S.

    2010-08-01

    Achieving low-error, exchange-interaction operations in quantum dots for quantum computing imposes simultaneous requirements on the exchange energy’s dependence on applied voltages. A double quantum dot qubit, approximated with a quadratic potential, is solved using a full configuration interaction method. This method is more accurate than Heitler-London and Hund-Mulliken approaches and captures new and significant qualitative behavior. We show that multiple regimes can be found in which the exchange energy’s dependence on the bias voltage between the dots is compatible with current quantum error correction codes and state-of-the-art electronics. Identifying such regimes may prove valuable for the construction and operation of quantum gates that are robust to charge fluctuations, particularly in the case of dynamically corrected gates.

  9. Double-quantum vibrational energy transfer in the O3-CO and O3-OCS systems

    NASA Technical Reports Server (NTRS)

    Hui, K.-K.; Cool, T. A.

    1976-01-01

    Using the CO2 laser induced fluorescence technique at 298 K for excitation of the P(30) transition in O3 or the P(22) transition in OCS, double-quantum vibrational energy transfer was studied in the O3-CO and O3-OCS binary gas systems. Rapid rates were observed for energy transfer from the CO (nu = 1) to the coupled O3(200), O3(101), and O3(002) levels, as well as for the transfer from the coupled O3(001) and O3(100) levels to the OCS(020) level. Deactivation of OCS by N2, Ar, and OCS was studied and deactivation rate constants were measured. The experimental results are compared with those calculated using the first order perturbation theory of dipole transition-moment interactions (Sharma and Brau, 1969) as modified by Tam (1972). An attempt is made to interpret the obtained results.

  10. THz Acoustic Spectroscopy by using Double Quantum Wells and Ultrafast Optical Spectroscopy

    PubMed Central

    Wei, Fan Jun; Yeh, Yu-Hsiang; Sheu, Jinn-Kong; Lin, Kung-Hsuan

    2016-01-01

    GaN is a pivotal material for acoustic transducers and acoustic spectroscopy in the THz regime, but its THz phonon properties have not been experimentally and comprehensively studied. In this report, we demonstrate how to use double quantum wells as a THz acoustic transducer for measuring generated acoustic phonons and deriving a broadband acoustic spectrum with continuous frequencies. We experimentally investigated the sub-THz frequency dependence of acoustic attenuation (i.e., phonon mean-free paths) in GaN, in addition to its physical origins such as anharmonic scattering, defect scattering, and boundary scattering. A new upper limit of attenuation caused by anharmonic scattering, which is lower than previously reported values, was obtained. Our results should be noteworthy for THz acoustic spectroscopy and for gaining a fundamental understanding of heat conduction. PMID:27346494

  11. Electron spin resonance and spin-valley physics in a silicon double quantum dot.

    PubMed

    Hao, Xiaojie; Ruskov, Rusko; Xiao, Ming; Tahan, Charles; Jiang, HongWen

    2014-05-14

    Silicon quantum dots are a leading approach for solid-state quantum bits. However, developing this technology is complicated by the multi-valley nature of silicon. Here we observe transport of individual electrons in a silicon CMOS-based double quantum dot under electron spin resonance. An anticrossing of the driven dot energy levels is observed when the Zeeman and valley splittings coincide. A detected anticrossing splitting of 60 MHz is interpreted as a direct measure of spin and valley mixing, facilitated by spin-orbit interaction in the presence of non-ideal interfaces. A lower bound of spin dephasing time of 63 ns is extracted. We also describe a possible experimental evidence of an unconventional spin-valley blockade, despite the assumption of non-ideal interfaces. This understanding of silicon spin-valley physics should enable better control and read-out techniques for the spin qubits in an all CMOS silicon approach.

  12. Effects of phonon scattering on the magneto-conductance in single and double quantum wires

    NASA Astrophysics Data System (ADS)

    Huang, D.; Lyo, S. K.

    2003-03-01

    We present an exact numerical formalism for the solution of the Boltzmann equation dominated by elastic (e.g., interface-roughness) and phonon scattering in a quasi-one-dimensional system. The result is employed to study the temperature-dependent conductance of a single and tunnel-coupled double quantum wells (DQWs) as a function of a perpendicular magnetic field. According to recent studies, the zero-temperature conductance is enhanced dramatically as a function of the field when the Fermi level lies inside the anticrossing gap of the DQWs. [S. K. Lyo, J. Phys.-Condens. Matter 8, L703 (1996), D. Huang and S. K. Lyo, ibid, 12, 3383 (2000), S. V. Korepov and M. A. Liberman, Phys. Rev. B 60, 13770 (1999)] Our results show that phonon scattering modifies the conductance and its enhancement significantly at temperatures corresponding to the gap energy or the sublevel separation or higher.

  13. Simultaneous spectral editing for gamma-aminobutyric acid and taurine using double quantum coherence transfer.

    PubMed

    Lei, H; Peeling, J

    2000-03-01

    Conventional double quantum (DQ) editing techniques recover resonances of one metabolite at a time and are thus inefficient for monitoring metabolic changes involving several metabolites. A DQ coherence transfer double editing sequence using a dual-band DQ coherence read pulse is described here. The sequence permits simultaneous spectral editing for two metabolites with similar J coupling constants in a single scan. Simultaneous editing for taurine and gamma-aminobutyric acid (GABA) is demonstrated using solution phantoms and rat brain tissue. Selectivity of the double editing sequence for the target metabolites is as good as that achieved using conventional DQ editing which selects each metabolite individually. With experimental parameters of the double editing sequence chosen to optimize GABA editing, the sensitivity for GABA detection is the same as that with GABA editing only, while the sensitivity for taurine detection is decreased slightly compared to that with taurine editing only.

  14. Photoemission and Masing in a Cavity-Coupled Semiconductor Double Quantum Dot

    NASA Astrophysics Data System (ADS)

    Petta, Jason

    2015-05-01

    Semiconductor circuit QED devices are exciting platforms for studying the coupled dynamics of single charges, photons, and phonons. I will describe a newly discovered maser, which is driven by single electron tunneling events that result in gigahertz frequency photon emission. Semiconductor double quantum dots, sometimes referred to as electrically tunable ``artificial molecules,'' serve as the gain medium and are placed inside of a high quality factor microwave cavity. Maser action is verified by comparing the statistics of the emitted microwave field above and below the maser threshold. Furthermore, by driving the cavity with a seed tone, it is possible to injection lock the maser, greatly reducing the emission linewidth. The frequency range over which the maser can be injection locked closely follows predictions from Adler's equation. Research was performed in collaboration with Yinyu Liu, Jiri Stehlik, Christopher Eichler, Michael Gullans, and Jacob Taylor. We acknowledge support from the Sloan and Packard Foundations, ARO, DARPA, and the NSF.

  15. Pauli Spin Blockade of Heavy Holes in a Silicon Double Quantum Dot.

    PubMed

    Li, Ruoyu; Hudson, Fay E; Dzurak, Andrew S; Hamilton, Alexander R

    2015-11-11

    In this work, we study hole transport in a planar silicon metal-oxide-semiconductor based double quantum dot. We demonstrate Pauli spin blockade in the few hole regime and map the spin relaxation induced leakage current as a function of interdot level spacing and magnetic field. With varied interdot tunnel coupling, we can identify different dominant spin relaxation mechanisms. Application of a strong out-of-plane magnetic field causes an avoided singlet-triplet level crossing, from which the heavy hole g-factor ~0.93 and the strength of spin-orbit interaction ~110 μeV can be obtained. The demonstrated strong spin-orbit interaction of heavy holes promises fast local spin manipulation using only electric fields, which is of great interest for quantum information processing.

  16. Optical phonon lasing and its detection in transport through semiconduc- tor double quantum dots

    NASA Astrophysics Data System (ADS)

    Okuyama, Rin; Eto, Mikio; Brandes, Tobias

    2014-03-01

    We theoretically propose optical phonon lasing for a double quantum dot (DQD) fabricated in a semiconductor substrate. No additional cavity or resonator is required. We show that the DQD couples to only two phonon modes that act as a natural cavity. The pumping to the upper level is realized by an electric current through the DQD under a finite bias. Using the rate equation in the Born-Markov-Secular approximation, we analyze the enhanced phonon emission when the level spacing in the DQD is tuned to the phonon energy. We find the phonon lasing when the pumping rate is much larger than the phonon decay rate, whereas anti-bunching of phonon emission is observed when the pumping rate is smaller.[1] Our theory can be also applicable to DQDs embedded in nanomechanical resonators to control the vibrating modes. We discuss detection of amplified modes using the electric current and its noise through the DQD, and another DQD fabricated nearby.

  17. Optimal control of a charge qubit in a double quantum dot with a Coulomb impurity

    NASA Astrophysics Data System (ADS)

    Coden, Diego S. Acosta; Romero, Rodolfo H.; Ferrón, Alejandro; Gomez, Sergio S.

    2017-02-01

    We study the efficiency of modulated external electric pulses to produce efficient and fast charge localization transitions in a two-electron double quantum dot. We use a configuration interaction method to calculate the electronic structure of a quantum dot model within the effective mass approximation. The interaction with the electric field is considered within the dipole approximation and optimal control theory is applied to design high-fidelity ultrafast pulses in pristine samples. We assessed the influence of the presence of Coulomb charged impurities on the efficiency and speed of the pulses. A protocol based on a two-step optimization is proposed for preserving both advantages of the original pulse. The processes affecting the charge localization is explained from the dipole transitions of the lowest lying two-electron states, as described by a discrete model with an effective electron-electron interaction.

  18. Efficient dipolar double quantum filtering under magic angle spinning without a (1)H decoupling field.

    PubMed

    Courtney, Joseph M; Rienstra, Chad M

    2016-08-01

    We present a systematic study of dipolar double quantum (DQ) filtering in (13)C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n⩾7, provided that the (13)C nutation frequency is on the order of 100kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between (13)C and (1)H fields. For (13)C nutation frequencies greater than 75kHz, optimal performance is observed without an applied (1)H field. At spinning rates exceeding 20kHz, symmetry conditions as low as n=3 were found to perform adequately.

  19. Nuclear state preparation via Landau-Zener-Stückelberg transitions in double quantum dots.

    PubMed

    Ribeiro, Hugo; Burkard, Guido

    2009-05-29

    We theoretically model a nuclear-state preparation scheme that increases the coherence time of a two-spin qubit in a double quantum dot. The two-electron system is tuned repeatedly across a singlet-triplet level anticrossing with alternating slow and rapid sweeps of an external bias voltage. Using a Landau-Zener-Stückelberg model, we find that in addition to a small nuclear polarization that weakly affects the electron spin coherence, the slow sweeps are only partially adiabatic and lead to a weak nuclear spin measurement and a nuclear-state narrowing which prolongs the electron spin coherence. This resolves some open problems brought up by a recent experiment [D. J. Reilly, Science 321, 817 (2008).10.1126/science.1159221]. Based on our description of the weak measurement, we simulate a system with up to n=200 nuclear spins per dot. Scaling in n indicates a stronger effect for larger n.

  20. Counter-diabatic driving for fast spin control in a two-electron double quantum dot

    PubMed Central

    Ban, Yue; Chen, Xi

    2014-01-01

    The techniques of shortcuts to adiabaticity have been proposed to accelerate the “slow” adiabatic processes in various quantum systems with the applications in quantum information processing. In this paper, we study the counter-diabatic driving for fast adiabatic spin manipulation in a two-electron double quantum dot by designing time-dependent electric fields in the presence of spin-orbit coupling. To simplify implementation and find an alternative shortcut, we further transform the Hamiltonian in term of Lie algebra, which allows one to use a single Cartesian component of electric fields. In addition, the relation between energy and time is quantified to show the lower bound for the operation time when the maximum amplitude of electric fields is given. Finally, the fidelity is discussed with respect to noise and systematic errors, which demonstrates that the decoherence effect induced by stochastic environment can be avoided in speeded-up adiabatic control. PMID:25174453

  1. Magnetoresistance of One-Dimensional Subbands in Tunnel-Coupled Double Quantum Wires

    SciTech Connect

    Moon, J.S.; Blount, M.A.; Simmons, J.A.; Wendt, J.R.; Lyo, S.K.; Reno, J.L.

    1999-08-04

    The authors study the low-temperature in-plane magnetoresistance of tunnel-coupled quasi-one-dimensional quantum wires. The wires are defined by two pairs of mutually aligned split gates on opposite sides of a {le} 1 micron thick AlGaAs/GaAs double quantum well heterostructure, allowing independent control of the width of each quantum well. In the ballistic regime, when both wires are defined and the field is perpendicular to the current, a large resistance peak at {approximately}6 Tesla is observed with a strong gate voltage dependence. The data is consistent with a counting model whereby the number of subbands crossing the Fermi level changes with field due to the formation of an anticrossing in each pair of 1D subbands.

  2. Tunnel magnetoresistance and linear conductance of double quantum dots strongly coupled to ferromagnetic leads

    SciTech Connect

    Weymann, Ireneusz

    2015-05-07

    We analyze the spin-dependent linear-response transport properties of double quantum dots strongly coupled to external ferromagnetic leads. By using the numerical renormalization group method, we determine the dependence of the linear conductance and tunnel magnetoresistance on the degree of spin polarization of the leads and the position of the double dot levels. We focus on the transport regime where the system exhibits the SU(4) Kondo effect. It is shown that the presence of ferromagnets generally leads the suppression of the linear conductance due to the presence of an exchange field. Moreover, the exchange field gives rise to a transition from the SU(4) to the orbital SU(2) Kondo effect. We also analyze the dependence of the tunnel magnetoresistance on the double dot levels' positions and show that it exhibits a very nontrivial behavior.

  3. Fano-Andreev effect in a T-shape double quantum dot in the Kondo regime

    NASA Astrophysics Data System (ADS)

    Calle, A. M.; Pacheco, M.; Martins, G. B.; Apel, V. M.; Lara, G. A.; Orellana, P. A.

    2017-04-01

    In the present work, we investigate the electronic transport through a T-shape double quantum dot system coupled to two normal leads and to one superconducting lead. We explore the interplay between Kondo and Andreev states due to proximity effects. We find that Kondo resonance is modified by the Andreev bound states, which manifest through Fano antiresonances in the local density of states of the embedded quantum dot and normal transmission. This means that there is a correlation between Andreev bound states and Fano resonances that is robust under the influence of high electronic correlation. We have also found that the dominant couplings at the quantum dots are characterized by a crossover region that defines the range where the Fano-Kondo and the Andreev-Kondo effect prevail in each quantum dot. Likewise, we find that the interaction between Kondo and Andreev bound states has a notable influence on the Andreev transport.

  4. Suppression of sodium nuclear magnetic resonance double-quantum coherence by chemical shift and relaxation reagents

    NASA Astrophysics Data System (ADS)

    Hutchison, Robert B.; Huntley, James J. A.; Jin, Haoran; Shapiro, Joseph I.

    1992-12-01

    An investigation into the signal suppression behavior of the paramagnetic shift and relaxation reagents, Dy(P3O10)27- and Gd(P3O10)27-, with regard to their use in the nuclear magnetic resonance spectroscopic study of sodium has been performed. Measurements of T1 and T2 relaxation time constants of sodium in normal saline, Krebs-Henseleit buffer, and human blood serum, as a function of concentration of these reagents showed that, although closely coupled in the saline and K-H buffer environments, in plasma T1 and T2 become decoupled, transverse relaxation dominating in comparison to longitudinal relaxation. Linewidth measurements further suggest that relaxation in the plasma milieu is controlled primarily by inherent T2 relaxation, rather than by field inhomogeneity or diffusion effects. Quantitative single-quantum (1Q) and double-quantum (2Q) intensity measurements, biexponential T2 relaxation measurements, and parametric studies of the preparation time of the 2Q pulse sequence, were obtained in suspensions of bovine serum albumin and human erythrocytes. The observed suppression of sodium 2Q coherence by paramagnetic shift and relaxation reagents was found to exhibit a complex behavior in albumin solutions, involving the biexponential T2 decay to be expected during the preparation time of the 2Q filter pulse sequence, as well as the optimum preparation time for production of the double-quantum coherence itself. The controlling factor for both of these effects is the biexponential amplitude function in the expression for the transverse magnetization observed following application of the 2Q pulse sequence. This in turn is determined entirely by the values for the slow and fast components of biexponential relaxation in sodium, which themselves depend upon the concentration of the macromolecular binding sites for quadrupolar interaction. A similar behavior has been observed in suspensions of human erythrocytes.

  5. Quantum interference and Kondo effects in an Aharonov-Bohm-Casher interferometer containing a laterally coupled double quantum dot

    NASA Astrophysics Data System (ADS)

    Kubo, T.; Tokura, Y.; Tarucha, S.

    2010-01-01

    We theoretically investigate spin-dependent electron transport through an Aharonov-Bohm-Casher interferometer containing a laterally coupled double quantum dot. In particular, we numerically calculate the Aharonov-Bohm and Aharonov-Casher oscillations of the linear conductance in the Kondo regime. We show that the AC oscillation in the Kondo regime deviates from the sinusoidal form.

  6. Nondestructive NMR determination of oil composition in transformed canola seeds.

    PubMed

    Hutton, W C; Garbow, J R; Hayes, T R

    1999-12-01

    Magic-angle spinning (MAS) 13C nuclear magnetic resonance (NMR) spectroscopy is a convenient method for nondestructive, quantitative characterization of seed oil composition. We describe results for intact hybrid and transformed canola seeds. The MAS 13C NMR technique complements and agrees with gas chromatography results. The spectral resolution approaches that of neat, liquid oils. MAS 13C NMR data allow quantitative analysis of major oil components, including saturates and oleic, linoleic, and linolenic acyl chains. 13C NMR directly and quantitatively elucidates, triglyceride regiochemistry and acyl chain cis-trans isomers that cannot be quickly detected by other methods. MAS 13C NMR can serve as the primary method for development of near-infrared seed oil calibrations. These NMR methods are nondestructive and attractive for plant-breeding programs or other studies (e.g., functional genomics) where loss of seed viability is inconvenient.

  7. SU(4)-SU(2) crossover and spin-filter properties of a double quantum dot nanosystem

    NASA Astrophysics Data System (ADS)

    Lopes, V.; Padilla, R. A.; Martins, G. B.; Anda, E. V.

    2017-06-01

    The SU(4)-SU(2) crossover, driven by an external magnetic field h , is analyzed in a capacitively coupled double quantum dot device connected to independent leads. As one continuously charges the dots from empty to quarter filled, by varying the gate potential Vg, the crossover starts when the magnitude of the spin polarization of the double quantum dot, as measured by - , becomes finite. Although the external magnetic field breaks the SU(4) symmetry of the Hamiltonian, the ground state preserves it in a region of Vg, where - =0 . Once the spin polarization becomes finite, it initially increases slowly until a sudden change occurs, in which (polarization direction opposite to the magnetic field) reaches a maximum and then decreases to negligible values abruptly, at which point an orbital SU(2) ground state is fully established. This crossover from one Kondo state, with emergent SU(4) symmetry, where spin and orbital degrees of freedom all play a role, to another, with SU(2) symmetry, where only orbital degrees of freedom participate, is triggered by a competition between g μBh , the energy gain by the Zeeman-split polarized state and the Kondo temperature TKS U (4 ), the gain provided by the SU(4) unpolarized Kondo-singlet state. At fixed magnetic field, the knob that controls the crossover is the gate potential, which changes the quantum dots occupancies. If one characterizes the occurrence of the crossover by Vgmax, the value of Vg where reaches a maximum, one finds that the function f relating the Zeeman splitting, Bmax, which corresponds to Vgmax, i.e., Bmax=f (Vgmax) , has a similar universal behavior to that of the function relating the Kondo temperature to Vg. In addition, our numerical results show that near the SU(4) Kondo temperature and for relatively small magnetic fields the device has a ground state that restricts the electronic population at the dots to be spin polarized along the magnetic field. These two

  8. Characterizations of F-superconductors and selected F-compounds, amorphous carbon, and (VO)2P2O7 by F-19, C-13, H-1, and P-31 NMR, and a new probe for multiple pulse, MAS, and DAS NMR

    NASA Astrophysics Data System (ADS)

    Pan, Hongjun

    1991-04-01

    NMR signals of F-19 were measured in the polycrystalline inorganic conductor Ag2F and in the polycrystalline insulators AgF, YOF, EuOF, YF3, CuF2, BaF2, and KF to compare them to the signals found in the so-called 1-2-3-type compounds with claimed formulas RBa2Cu3O(7-x)F(x) (R = Y and Eu). No evidence for a Knight-shifted, built-in fluorine-signal was found in the 1-2-3-type superconductors. The only signal found was from the BaF2 which is an impurity in the superconductors.

  9. Level Spectrum and Charge Relaxation in a Silicon Double Quantum Dot Probed by Dual-Gate Reflectometry.

    PubMed

    Crippa, Alessandro; Maurand, Romain; Kotekar-Patil, Dharmraj; Corna, Andrea; Bohuslavskyi, Heorhii; Orlov, Alexei O; Fay, Patrick; Laviéville, Romain; Barraud, Sylvain; Vinet, Maud; Sanquer, Marc; De Franceschi, Silvano; Jehl, Xavier

    2017-02-08

    We report on dual-gate reflectometry in a metal-oxide-semiconductor double-gate silicon transistor operating at low temperature as a double quantum dot device. The reflectometry setup consists of two radio frequency resonators respectively connected to the two gate electrodes. By simultaneously measuring their dispersive responses, we obtain the complete charge stability diagram of the device. Electron transitions between the two quantum dots and between each quantum dot and either the source or the drain contact are detected through phase shifts in the reflected radio frequency signals. At finite bias, reflectometry allows probing charge transitions to excited quantum-dot states, thereby enabling direct access to the energy level spectra of the quantum dots. Interestingly, we find that in the presence of electron transport across the two dots the reflectometry signatures of interdot transitions display a dip-peak structure containing quantitative information on the charge relaxation rates in the double quantum dot.

  10. Direct measurement on the geometric phase of a double quantum dot qubit via quantum point contact device

    PubMed Central

    Liu, Bao; Zhang, Feng-Yang; Song, Jie; Song, He-Shan

    2015-01-01

    We propose a direct measurement scheme to read out the geometric phase of a coupled double quantum dot system via a quantum point contact(QPC) device. An effective expression of the geometric phase has been derived, which relates the geometric phase of the double quantum dot qubit to the current through QPC device. All the parameters in our expression are measurable or tunable in experiment. Moreover, since the measurement process affects the state of the qubit slightly, the geometric phase can be protected. The feasibility of the scheme has been analyzed. Further, as an example, we simulate the geometrical phase of a qubit when the QPC device is replaced by a single electron transistor(SET). PMID:26121538

  11. Coupled-Double-Quantum-Dot Environmental Information Engines: A Numerical Analysis

    NASA Astrophysics Data System (ADS)

    Tanabe, Katsuaki

    2016-06-01

    We conduct numerical simulations for an autonomous information engine comprising a set of coupled double quantum dots using a simple model. The steady-state entropy production rate in each component, heat and electron transfer rates are calculated via the probability distribution of the four electronic states from the master transition-rate equations. We define an information-engine efficiency based on the entropy change of the reservoir, implicating power generators that employ the environmental order as a new energy resource. We acquire device-design principles, toward the realization of corresponding practical energy converters, including that (1) higher energy levels of the detector-side reservoir than those of the detector dot provide significantly higher work production rates by faster states' circulation, (2) the efficiency is strongly dependent on the relative temperatures of the detector and system sides and becomes high in a particular Coulomb-interaction strength region between the quantum dots, and (3) the efficiency depends little on the system dot's energy level relative to its reservoir but largely on the antisymmetric relative amplitudes of the electronic tunneling rates.

  12. Yield Enhancement of a Double-Quantum Filter Sequence Designed for the Edited Detection of GABA

    NASA Astrophysics Data System (ADS)

    Wilman, Alan H.; Allen, Peter S.

    1995-11-01

    To overcome limitations in the signal to noise ratio (S/N) of previously proposed multiple-quantum filters (MQFs), designed for editing the GABA A2multiplet from the creatine (Cr) singlet in proton spectroscopy of brain, a new double-quantum filter is proposed which significantly enhancesS/N(thereby making it comparable with the spin-echo difference editing technique) while maintaining the superior Cr suppression and zero vulnerability to subtraction errors of previously proposed MQFs. TheS/Nenhancement results primarily from a significant reduction in transverse-relaxation losses, achieved by shortening the filter sequence by ∼70%, first by altering the criterion that determines the initial evolution period and, second, by effectively eliminating the refocusing time prior to the start of acquisition. The altered evolution time criterion also leads to an increase in the intrinsic yield of the filter from 25 to 39%. The analysis of the filter design was verifiedin vitroon phantoms of GABA in D2O, and the maintenance of editing capability, i.e., Cr suppression by more than 1600, was demonstrated on rat brain extracts.

  13. Pulse propagation and optically controllable switch in coupled semiconductor-double-quantum-dot nanostructures

    SciTech Connect

    Hamedi, H. R. E-mail: hamid.hamedi@tfai.vu.lt

    2016-05-14

    The problem of pulse propagation is theoretically investigated through a coupled semiconductor-double-quantum-dot (SDQD) nanostructure. Solving the coupled Maxwell–Bloch equations for the SDQD and field simultaneously, the dynamic control of pulse propagation through the medium is numerically explored. It is found that when all the control fields are in exact resonance with their corresponding transitions, a weak Gaussian-shaped probe pulse is transmitted through the medium nearly without any significant absorption and losses so that it can preserve its shape for quite a long propagation distance. In contrast, when one of the control fields is not in resonance with its corresponding transition, the probe pulse will be absorbed by the QD medium after a short distance. Then we consider the probe pulses with higher intensities. It is realized that an intense probe pulse experiences remarkable absorption and broadening during propagation. Finally, we demonstrate that this SDQD system can be employed as an optically controllable switch for the wave propagation to transit from an absorbing phase to a perfect transparency for the probe field. The required time for such switch is also estimated through realistic values.

  14. Coupling capacitance between double quantum dots tunable by the number of electrons in Si quantum dots

    SciTech Connect

    Uchida, Takafumi Arita, Masashi; Takahashi, Yasuo; Fujiwara, Akira

    2015-02-28

    Tunability of capacitive coupling in the Si double-quantum-dot system is discussed by changing the number of electrons in quantum dots (QDs), in which the QDs are fabricated using pattern-dependent oxidation (PADOX) of a Si nanowire and multi-fine-gate structure. A single QD formed by PADOX is divided into multiple QDs by additional oxidation through the gap between the fine gates. When the number of electrons occupying the QDs is large, the coupling capacitance increases gradually and almost monotonically with the number of electrons. This phenomenon is attributed to the gradual growth in the effective QD size due to the increase in the number of electrons in the QDs. On the other hand, when the number of electrons changes in the few-electron regime, the coupling capacitance irregularly changes. This irregularity can be observed even up to 40 electrons. This behavior is attributable the rough structure of Si nano-dots made by PADOX. This roughness is thought to induce complicated change in the electron wave function when an electron is added to or subtracted from a QD.

  15. Current cross-correlations in double quantum dot based Cooper pair splitters with ferromagnetic leads

    NASA Astrophysics Data System (ADS)

    Wrześniewski, Kacper; Trocha, Piotr; Weymann, Ireneusz

    2017-05-01

    We investigate the current cross-correlations in a double quantum dot based Cooper pair splitter coupled to one superconducting and two ferromagnetic electrodes. The analysis is performed by assuming a weak coupling between the double dot and ferromagnetic leads, while the coupling to the superconductor is arbitrary. Employing the perturbative real-time diagrammatic technique, we study the Andreev transport properties of the device, focusing on the Andreev current cross-correlations, for various parameters of the model, both in the linear and nonlinear response regimes. Depending on parameters and transport regime, we find both positive and negative current cross-correlations. Enhancement of the former type of cross-correlations indicates transport regimes, in which the device works with high Cooper pair splitting efficiency, contrary to the latter type of correlations, which imply negative influence on the splitting. The processes and mechanisms leading to both types of current cross-correlations are thoroughly examined and discussed, giving a detailed insight into the Andreev transport properties of the considered device.

  16. Resolution enhancement in MR spectroscopy of red bone marrow fat via intermolecular double-quantum coherences

    NASA Astrophysics Data System (ADS)

    Bao, Jianfeng; Cui, Xiaohong; Huang, Yuqing; Zhong, Jianhui; Chen, Zhong

    2015-08-01

    High-resolution 1H magnetic resonance spectroscopy (MRS) is generally inaccessible in red bone marrow (RBM) tissues using conventional MRS techniques. This is because signal from these tissues suffers from severe inhomogeneity in the main static B0 field originated from the intrinsic honeycomb structures in trabecular bone. One way to reduce effects of B0 field inhomogeneity is by using the intermolecular double quantum coherence (iDQC) technique, which has been shown in other systems to obtain signals insensitive to B0 field inhomogeneity. In the present study, we employed an iDQC approach to enhance the spectral resolution of RBM. The feasibility and performance of this method for achieving high resolution MRS was verified by experiments on phantoms and pig vertebral bone samples. Unsaturated fatty acid peaks which overlap in the conventional MRS were well resolved and identified in the iDQC spectrum. Quantitative comparison of fractions of three types of fatty acids was performed between iDQC spectra on the in situ RMB and conventional MRS on the extracted fat from the same RBM. Observations of unsaturated fatty acids with iDQC MRS may provide valuable information and may hold potential in diagnosis of diseases such as obesity, diabetes, and leukemia.

  17. Spin-orbit effects on the full dynamics of double quantum dot qubit states

    NASA Astrophysics Data System (ADS)

    Cota, Ernesto; Rolon, Juan E.; Platero, Gloria; Ulloa, Sergio E.

    2012-02-01

    We study spin-obit interaction (SOI) and relaxation effects on the measurement of the extended singlet state return probability P(S) in a double quantum dot (DQD) system with two electrons, in the presence of hyperfine interaction (HFI) and weak external magnetic fields. Using appropriate pulse cycles to change the detuning between the two quantum dots, we describe the full dynamical behavior of the system taking into account the complete set of states. We find that the mixing of the ms=1;(T+) triplet with the (0,2) local singlet, induced by SOI via non-spin-conserving tunneling transitions, has an important effect on the measurement of P(S), and a clear experimental signature. The numerical results are also analyzed in terms of a Feshbach projection to the effective low-energy dynamics, which explain the role of SOI on the relaxation and overall dynamics relevant in experiments. We also explore the case of the Landau-Zener-St"uckelberg interferometry realized via voltage sweeps through the S-T+anticrossing generated by HFI in the DQD energy spectrum [1]. We focus on studying the effects of SOI and relaxation on the interferometric properties of the system in this regime. [1] J.R. Petta, H. Lu and A.C. Gossard, Science 327, 669 (2010).

  18. Impact of g -factors and valleys on spin qubits in a silicon double quantum dot

    NASA Astrophysics Data System (ADS)

    Hwang, J. C. C.; Yang, C. H.; Veldhorst, M.; Hendrickx, N.; Fogarty, M. A.; Huang, W.; Hudson, F. E.; Morello, A.; Dzurak, A. S.

    2017-07-01

    We define single electron spin qubits in a silicon metal-oxide-semiconductor double quantum dot system. By mapping the qubit resonance frequency as a function of a gate-induced electric field, the spectrum reveals an anticrossing that is consistent with an intervalley spin-orbit coupling. We fit the data from which we extract an intervalley coupling strength of 43 MHz. In addition, we observe a narrow resonance near the primary qubit resonance when we operate the device in the (1 ,1 ) charge configuration. The experimental data are consistent with a simulation involving two weakly exchanged-coupled spins with a Zeeman energy difference of 1 MHz, of the same order as the Rabi frequency. We conclude that the narrow resonance is the result of driven transitions between the T- and T+ triplet states, using an electron spin resonance signal of frequency located halfway between the resonance frequencies of the two individual spins. The findings presented here offer an alternative method of implementing two-qubit gates, of relevance to the operation of larger-scale spin qubit systems.

  19. Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

    NASA Astrophysics Data System (ADS)

    Knapp, T. J.; Mohr, R. T.; Li, Yize Stephanie; Thorgrimsson, Brandur; Foote, Ryan H.; Wu, Xian; Ward, Daniel R.; Savage, D. E.; Lagally, M. G.; Friesen, Mark; Coppersmith, S. N.; Eriksson, M. A.

    We report the characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. Previously, all heterostructures used to form quantum dots were created using the strain-grading method of strain relaxation, a method that necessarily introduces misfit dislocations into a heterostructure and thereby degrades the reproducibility of quantum devices. Using a SiGe nanomembrane as a virtual substrate eliminates the need for misfit dislocations but requires a wet-transfer process that results in a non-epitaxial interface in close proximity to the quantum dots. We show that this interface does not prevent the formation of quantum dots, and is compatible with a tunable inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of the applied magnetic field. This work was supported in part by ARO (W911NF-12-0607), NSF (DMR-1206915, PHY-1104660), and the United States Department of Defense. The views and conclusions contained in this document are those of the author and should not be interpreted as representing the official policies, either expressly or implied, of the US Government. T.J. Knapp et al. (2015). arXiv:1510.08888 [cond-mat.mes-hall].

  20. Transport and charge sensing in Si/SiGe double-quantum dots

    NASA Astrophysics Data System (ADS)

    Simmons, Christie; Thalakulam, Madhu; Sackmann, E. K.; van Bael, B. J.; Savage, D. E.; Lagally, M. G.; Joynt, R.; Friesen, M.; Coppersmith, S. N.; Eriksson, M. A.

    2009-03-01

    Gated quantum dots in Si/SiGe are of interest because spins in silicon are weakly coupled to the host material. We demonstrate that Coulomb blockade measurements through a single quantum dot are well correlated with charge sensing in a nearby quantum point contact. Charge sensing enables the determination of the absolute number of electrons in the system, and we present data demonstrating a one-electron single quantum dot. Incorporated with a double quantum dot, charge sensing can be used to probe the inter-dot motion of a single electron at fixed total charge in the double dot. The tunnel coupling between the two dots directly effects the charge localization and thus the sharpness of this inter-dot transition. Here we demonstrate gated electrical control of the exchange coupling -- an important step towards qubit implementation -- showing a smooth transition between two well-isolated dots, two dots so strongly coupled that they act as a single large quantum dot, and the intermediate regime.

  1. Current cross-correlations in double quantum dot based Cooper pair splitters with ferromagnetic leads.

    PubMed

    Wrześniewski, Kacper; Trocha, Piotr; Weymann, Ireneusz

    2017-05-17

    We investigate the current cross-correlations in a double quantum dot based Cooper pair splitter coupled to one superconducting and two ferromagnetic electrodes. The analysis is performed by assuming a weak coupling between the double dot and ferromagnetic leads, while the coupling to the superconductor is arbitrary. Employing the perturbative real-time diagrammatic technique, we study the Andreev transport properties of the device, focusing on the Andreev current cross-correlations, for various parameters of the model, both in the linear and nonlinear response regimes. Depending on parameters and transport regime, we find both positive and negative current cross-correlations. Enhancement of the former type of cross-correlations indicates transport regimes, in which the device works with high Cooper pair splitting efficiency, contrary to the latter type of correlations, which imply negative influence on the splitting. The processes and mechanisms leading to both types of current cross-correlations are thoroughly examined and discussed, giving a detailed insight into the Andreev transport properties of the considered device.

  2. Waiting time distribution revealing the internal spin dynamics in a double quantum dot

    NASA Astrophysics Data System (ADS)

    Ptaszyński, Krzysztof

    2017-07-01

    Waiting time distribution and the zero-frequency full counting statistics of unidirectional electron transport through a double quantum dot molecule attached to spin-polarized leads are analyzed using the quantum master equation. The waiting time distribution exhibits a nontrivial dependence on the value of the exchange coupling between the dots and the gradient of the applied magnetic field, which reveals the oscillations between the spin states of the molecule. The zero-frequency full counting statistics, on the other hand, is independent of the aforementioned quantities, thus giving no insight into the internal dynamics. The fact that the waiting time distribution and the zero-frequency full counting statistics give a nonequivalent information is associated with two factors. Firstly, it can be explained by the sensitivity to different timescales of the dynamics of the system. Secondly, it is associated with the presence of the correlation between subsequent waiting times, which makes the renewal theory, relating the full counting statistics and the waiting time distribution, no longer applicable. The study highlights the particular usefulness of the waiting time distribution for the analysis of the internal dynamics of mesoscopic systems.

  3. Enhanced spin figure of merit in an Aharonov-Bohm ring with a double quantum dot

    SciTech Connect

    Zhou, Xingfei; Qi, Fenghua; Jin, Guojun

    2014-04-21

    We theoretically investigate the thermoelectric effects in an Aharonov-Bohm ring with a serially coupled double quantum dot embedded in one arm. An external magnetic field is perpendicularly applied to the two dots. Using the nonequilibrium Green's function method in the linear-response regime, we calculate the charge and spin figures of merit. When the energy levels of the two quantum dots are equal and the system is connected to two normal leads, a large spin figure of merit (Z{sub s}T ≈ 4.5) accompanying with a small charge figure of merit (Z{sub c}T ≈ 0) can be generated due to the remarkable bipolar effect. Further, when the system is connected to two ferromagnetic leads, the spin figure of merit can reach even a higher value about 9. Afterwards, we find that Z{sub s}T is enhanced while Z{sub c}T is reduced in the coaction of the Aharonov-Bohm flux and Rashba spin-orbit coupling. It is argued that the bipolar effect is positive (negative) to spin (charge) figure of merit in the presence of level detuning of the two quantum dots and intradot Coulomb interactions, respectively. Also, we propose a possible experiment to verify our results.

  4. Real-time tuning of a double quantum dot using a Josephson parametric amplifier

    NASA Astrophysics Data System (ADS)

    Stehlik, J.; Liu, Y.-Y.; Quintana, C. M.; Eichler, C.; Hartke, T. R.; Petta, J. R.

    Josephson parametric amplifiers (JPAs) have enabled advances in readout of quantum systems. Here we demonstrate JPA-assisted readout of a cavity-coupled double quantum dot (DQD). Utilizing a JPA we improve the signal-to-noise ratio (SNR) by a factor of 2000 compared to the situation with the parametric amplifier turned off. At an interdot charge transition we achieve a SNR of 76 (19 dB) with an integration time τ = 400 ns, which is limited by the linewidth of our cavity. By measuring the SNR as a function of τ we extract an equivalent charge sensitivity of 8 ×10-5 e /√{ Hz} . We develop a dual-gate-voltage rastering scheme that allows us to acquire a DQD charge stability diagram in just 20 ms. Such rapid data acquisition rates enable device tuning in live ``video-mode,'' where the results of parameter changes are immediately displayed. Live tuning allows the DQD confinement potential to be rapidly tuned, a capability that will become increasingly important as semiconductor spin qubits are scaled to a larger number of dots. Research is supported by the Packard Foundation, ARO Grant No. W911NF-15-1-0149, DARPA QuEST Grant No. HR0011-09-1-0007, and the NSF (Grants No. DMR-1409556 and DMR-1420541).

  5. Photoluminescence studies of modulation doped coupled double quantum wells in magnetic fields

    SciTech Connect

    Kim, Y.; Perry, C.H. |; Simmons, J.A.; Klem, J.F.; Jones, E.D.; Rickel, D.G.

    1996-09-01

    We have studied the photoluminescence spectra of a series of mudulation doped couple double quantum well structures in parallel and perpendicular magnetic fields to 62 tesla at 4K and 77K, for B{parallel}a, the spectra display distinct Landau level transitions which show anti-crossing with the e1-hh1 exciton. At high fields, the lowest conduction band-valence exciton approaches the extrapolated 0- 0 Landau level. About 25 Tesla, there is valence band mixing of the e1-lh1, e1-hh2, e1-hh1 transitions. The spectral peaks display a diamagnetic shift in low in-plane magnetic fields which become linear in high fields. At magnetic fields beyond 40T, spin splitting is observed for both B{parallel}z and B{perpendicular} geometries. The partial energy gap discovered in conductance measurements in in-plane fields was not conclusively observed using photoluminescence spectroscopy, although anomalies in the energy dependence of the lowest level with magnetic field were evident at similar field values.

  6. Electron bilayers in an undoped Si/SiGe double-quantum-well heterostructure

    NASA Astrophysics Data System (ADS)

    Lu, Tzu-Ming; Laroche, Dominique; Huang, Shih-Hsien; Nielsen, Erik; Chuang, Yen; Li, Jiun-Yun; Liu, Cheewee

    We report the design, fabrication, and the magneto-transport study of an undoped Si/SiGe double quantum well heterostructure. We show that employing asymmetric quantum wells for our single-side-gated devices allows us to observe a cross-over from single-layer-like to bi-layer-llike behavior in the mobility-density dependence. We also observe an integer quantum Hall state at filling factor ν = 2, which is expected to arise from inter-layer effects for Si electrons. This state could be due to either inter-layer coherence, or the symmetric-antisymmetric tunneling gap. This work has been supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy (DOE). Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  7. Parity qubits and poor man's Majorana bound states in double quantum dots

    NASA Astrophysics Data System (ADS)

    Leijnse, Martin; Flensberg, Karsten

    2012-10-01

    We study a double quantum dot connected via a common superconducting lead and show that this system can be tuned to host one Majorana bound state (MBS) on each dot. We call them “poor man's Majorana bound states” since they are not topologically protected, but otherwise share the properties of MBS formed in topological superconductors. We describe the conditions for the existence of the two spatially separated MBS, which include breaking of spin degeneracy in the two dots, with the spins polarized in different directions. Therefore, we propose to use a magnetic field configuration where the field directions on the two dots form an angle. By control of this angle the cross Andreev reflection and the tunnel amplitudes can be tuned to be approximately equal, which is a requirement for the formation of the MBS. We show that the fermionic state encoded in the two Majoranas constitutes a parity qubit, which is nonlocal and can only be measured by probing both dots simultaneously. Using a many-particle basis for the MBS, we discuss the role of interactions and show that interactions between electrons on different dots always shift the condition for degeneracy. We also show how the MBS can be probed by transport measurements and discuss how the combination of several such double dot systems allows for entanglement of parity qubits and measurement of their dephasing times.

  8. Molecular states in double quantum wells: nanochemistry for metatmaterials with new optical properties

    NASA Astrophysics Data System (ADS)

    Gutierrez, Rafael M.; Castañeda, Arcesio

    2009-08-01

    Quantum mechanics explains the existence and properties of the chemical bond responsible for the formation of molecules from isolated atoms. In this work we study quantum states of Double Quantum Wells, DQW, formed from isolated Single Quantum Wells, SQWs, that can be considered metamaterials. Using the quantum chemistry definition of the covalent bond, we discuss molecular states in DQW as a kind of nanochemistry of metamaterials with new properties, in particular new optical properties. An important particularity of such nanochemistry, is the possible experimental control of the geometrical parameters and effective masses characterizing the semiconductor heterostructures represented by the corresponding DQW. This implies a great potential for new applications of the controlled optical properties of the metamaterials. The use of ab initio methods of intensive numerical calculations permits to obtain macroscopic optical properties of the metamaterials from the fundamental components: the spatial distribution of the atoms and molecules constituting the semiconductor layers. The metamaterial new optical properties emerge from the coexistence of many body processes at atomic and molecular level and complex quantum phenomena such as covalent-like bonds at nanometric dimensions.

  9. Edge magnetoplasmons in double quantum wells: Influence of Coulomb coupling and tunneling

    NASA Astrophysics Data System (ADS)

    Vasilopoulos, P.; Balev, O. G.

    1998-12-01

    A random-phase approximation (RPA) treatment of fundamental edge magnetoplasmons (EMPs) in a double quantum well (DQW) is presented for strong magnetic fields, low temperatures, and total filling factor ν=2. It is valid for lateral confining potentials that allow Landau-level flattening to be neglected. The cyclotron and Zeeman energies are larger than the DQW energy splitting ( Δ2+4 T2) 1/2, where Δ is the splitting of the isolated wells and T the tunneling strength. For negligible T the inter-well Coulomb coupling drastically renormalizes the fundamental EMP of the corresponding single quantum well ( ν=1) and gives rise to two DQW fundamental EMPs. These modes can be affected further by varying the inter-well distance, along the z axis, and/or the separation of the wells' edges along the y axis. The charge profile of the fast and slow mode varies, respectively, in an acoustic and optical manner along the y axis. For strong T these modes can be modified essentially when Δ is changed by applying a transverse electric field to the DQW.

  10. A Planar Quantum Transistor Based on 2D-2D Tunneling in Double Quantum Well Heterostructures

    SciTech Connect

    Baca, W.E.; Blount, M.A.; Hafich, M.J.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.

    1998-12-14

    We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.

  11. Transport and Charge Manipulation in a Single Electron Silicon Double Quantum Dot

    NASA Astrophysics Data System (ADS)

    Wang, K.; Payette, C.; Dovzhenko, Y.; Petta, J. R.

    2013-03-01

    Silicon is one of the most promising candidates for ultra-coherent qubits due to its relatively early position in periodical table and the absence of nuclear spin in its naturally abundant isotope. Here we demonstrate a reliable recipe that enables us to reproducibly fabricate an accumulation mode few electron double quantum dot (DQD). We demonstrate tunable interdot tunnel coupling at single electron occupancy in the device. The charge state of the qubit is monitored by measuring the amplitude of the radio frequency signal that is reflected from a resonant circuit coupled to a charge sensor. By applying microwave radiation to the depletion gates, we probe the energy level structure of the DQD using photon assisted tunneling (PAT). We apply bursts of microwave radiation and monitor the dependence of the PAT peak height on the burst period to extract the charge relaxation time, T1. By experimentally tuning the charge qubit Hamiltonian, we measure the tunnel coupling and detuning dependence of T1. Supported by the United States Department of Defense. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressly or implied, of the U.S. Government.

  12. Intrinsic errors in transporting a single-spin qubit through a double quantum dot

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Barnes, Edwin; Kestner, J. P.; Das Sarma, S.

    2017-07-01

    Coherent spatial transport or shuttling of a single electron spin through semiconductor nanostructures is an important ingredient in many spintronic and quantum computing applications. In this work we analyze the possible errors in solid-state quantum computation due to leakage in transporting a single-spin qubit through a semiconductor double quantum dot. In particular, we consider three possible sources of leakage errors associated with such transport: finite ramping times, spin-dependent tunneling rates between quantum dots induced by finite spin-orbit couplings, and the presence of multiple valley states. In each case we present quantitative estimates of the leakage errors, and discuss how they can be minimized. The emphasis of this work is on how to deal with the errors intrinsic to the ideal semiconductor structure, such as leakage due to spin-orbit couplings, rather than on errors due to defects or noise sources. In particular, we show that in order to minimize leakage errors induced by spin-dependent tunnelings, it is necessary to apply pulses to perform certain carefully designed spin rotations. We further develop a formalism that allows one to systematically derive constraints on the pulse shapes and present a few examples to highlight the advantage of such an approach.

  13. Qubit detection with a T-shaped double quantum dot detector

    NASA Astrophysics Data System (ADS)

    Luo, JunYan; Jiao, HuJun; Hu, Jing; He, Xiao-Ling; Lang, XiaoLi; Wang, Shi-Kuan

    2015-07-01

    We propose to continuously monitor a charge qubit by utilizing a T-shaped double quantum dot detector, in which the qubit and double dot are arranged in such a unique way that the detector turns out to be particularly susceptible to the charge states of the qubit. Special attention is paid to the regime where acquisition of qubit information and backaction upon the measured system exhibit nontrivial correlation. The intrinsic dynamics of the qubit gives rise to dynamical blockade of tunneling events through the detector, resulting in a super-Poissonian noise. However, such a pronounced enhancement of the detector's shot noise does not necessarily produce a rising dephasing rate. In contrast, an inhibition of dephasing is entailed by the reduction of information acquisition in the dynamically blockaded regimes. We further reveal the important impact of the charge fluctuations on the measurement characteristics. Noticeably, under the condition of symmetric junction capacitances the noise pedestal of the circuit current is completely suppressed, leading to a divergent signal-to-noise ratio, and eventually to a violation of the Korotkov-Averin bound in quantum measurement. Our study offers the possibility for a double dot detector to reach the quantum limited effectiveness in a transparent manner.

  14. Charge dynamics and spin blockade in a hybrid double quantum dot in silicon

    NASA Astrophysics Data System (ADS)

    Chatterjee, Anasua; Urdampilleta, Matias; Lo, Cheuk Chi; Mansir, John; Barraud, Sylvain; Betz, Andreas; Gonzalez-Zalba, M. Fernando; Morton, John J. L.

    Hybrid architectures combining donor atoms and quantum dots in silicon can take advantage of fast gate voltage based spin manipulations to form a hybrid singlet-triplet qubit, with access to the quantum memory offered by the nuclear spin of the donor via the hyperfine interaction. Additionally, spin buses using quantum dot chains could mediate the transfer of quantum information between long-lived donor spins. We present an approach to a novel hybrid double quantum dot by coupling a donor to an artificial atom in a CMOS-compatible nanotransistor. Using gate-based RF-reflectometry, we probe the charge stability of the system and its quantum capacitance. Through microwave spectroscopy, we find a tunnel coupling of 2.7GHz and characterize the charge dynamics, revealing a charge T1 of 100ns. We also show spin blockade at the inderdot transition and investigate the spin dynamics, opening up the possibility to operate this coupled system as a singlet-triplet qubit and to coherently transfer spin information between the quantum dot and the donor electron and nucleus. We acknowledge support from the TOLOP project (FP7/318397), the EPSRC, ARC, and the UNDEDD project, the Royal Commission for the Exhibition of 1851 and the Royal Society.

  15. A localized double-quantum filter for the in vivo detection of brain glucose.

    PubMed

    Keltner, J R; Wald, L L; Ledden, P J; Chen, Y C; Matthews, R T; Küestermann, E H; Baker, J R; Rosen, B R; Jenkins, B G

    1998-04-01

    A double-quantum filter (DQF) sequence with PRESS localization was developed for in vivo detection of the glucose resonances in the 3.85-ppm region of the brain proton spectrum. The efficiency and spectral editing characteristics were studied in phantom and animal experiments. Approximately 45% detection efficiency was achieved at 4.7 T with TE = 68 ms. Since the efficiency of the DQF method is dependent on the relative phases of the RF pulses, a phase calibration procedure was used to correct for phase shifts induced by the spatial localization. In addition to detecting the 3.85-ppm glucose resonances with approximately 45% efficiency, the DQF sequence simultaneously detects 1.3-ppm lactate resonance with approximately 20% efficiency. The use of the DQF technique for simultaneously monitoring both the input and output of anaerobic glycolysis in the brain was demonstrated by detecting brain glucose and lactate in the same acquisition after iv injection of glucose followed by the induction of global ischemia.

  16. Electrical and Optical Gain Lever Effects in InGaAs Double Quantum Well Diode Lasers

    SciTech Connect

    Pocha, M D; Goddard, L L; Bond, T C; Nikolic, R J; Vernon, S P; Kallman, J S; Behymer, E M

    2007-01-03

    In multisection laser diodes, the amplitude or frequency modulation (AM or FM) efficiency can be improved using the gain lever effect. To study gain lever, InGaAs double quantum well (DQW) edge emitting lasers have been fabricated with integrated passive waveguides and dual sections providing a range of split ratios from 1:1 to 9:1. Both the electrical and the optical gain lever have been examined. An electrical gain lever with greater than 7 dB enhancement of AM efficiency was achieved within the range of appropriate DC biasing currents, but this gain dropped rapidly outside this range. We observed a 4 dB gain in the optical AM efficiency under non-ideal biasing conditions. This value agreed with the measured gain for the electrical AM efficiency under similar conditions. We also examined the gain lever effect under large signal modulation for digital logic switching applications. To get a useful gain lever for optical gain quenched logic, a long control section is needed to preserve the gain lever strength and a long interaction length between the input optical signal and the lasing field of the diode must be provided. The gain lever parameter space has been fully characterized and validated against numerical simulations of a semi-3D hybrid beam propagation method (BPM) model for the coupled electron-photon rate equation. We find that the optical gain lever can be treated using the electrical injection model, once the absorption in the sample is known.

  17. Steady state conductance in a double quantum dot array: the nonequilibrium equation-of-motion Green function approach.

    PubMed

    Levy, Tal J; Rabani, Eran

    2013-04-28

    We study steady state transport through a double quantum dot array using the equation-of-motion approach to the nonequilibrium Green functions formalism. This popular technique relies on uncontrolled approximations to obtain a closure for a hierarchy of equations; however, its accuracy is questioned. We focus on 4 different closures, 2 of which were previously proposed in the context of the single quantum dot system (Anderson impurity model) and were extended to the double quantum dot array, and develop 2 new closures. Results for the differential conductance are compared to those attained by a master equation approach known to be accurate for weak system-leads couplings and high temperatures. While all 4 closures provide an accurate description of the Coulomb blockade and other transport properties in the single quantum dot case, they differ in the case of the double quantum dot array, where only one of the developed closures provides satisfactory results. This is rationalized by comparing the poles of the Green functions to the exact many-particle energy differences for the isolate system. Our analysis provides means to extend the equation-of-motion technique to more elaborate models of large bridge systems with strong electronic interactions.

  18. Observation of NMR noise from solid samples

    PubMed Central

    Schlagnitweit, Judith; Dumez, Jean-Nicolas; Nausner, Martin; Jerschow, Alexej; Elena-Herrmann, Bénédicte; Müller, Norbert

    2010-01-01

    We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio frequency, can be obtained from solid samples. Experimental results are shown for static and magic-angle spinning conditions. In addition, a tuning procedure based on the probes’ NMR noise characteristics and similar to the one described previously for liquids probes can also be used to optimize signal-to-noise ratios in 1H-MAS experiments. PMID:20850362

  19. Solid-state NMR spectroscopy of proteins.

    PubMed

    Müller, Henrik; Etzkorn, Manuel; Heise, Henrike

    2013-01-01

    Solid-state NMR spectroscopy proved to be a versatile tool for characterization of structure and dynamics of complex biochemical systems. In particular, magic angle spinning (MAS) solid-state NMR came to maturity for application towards structural elucidation of biological macromolecules. Current challenges in applying solid-state NMR as well as progress achieved recently will be discussed in the following chapter focusing on conceptual aspects important for structural elucidation of proteins.

  20. Proton Environments in Biomimetic Calcium Phosphates Formed from Mesoporous Bioactive CaO-SiO2-P2O5 Glasses in Vitro: Insights from Solid-State NMR.

    PubMed

    Mathew, Renny; Turdean-Ionescu, Claudia; Yu, Yang; Stevensson, Baltzar; Izquierdo-Barba, Isabel; García, Ana; Arcos, Daniel; Vallet-Regí, María; Edén, Mattias

    2017-06-22

    When exposed to body fluids, mesoporous bioactive glasses (MBGs) of the CaO-SiO2-P2O5 system develop a bone-bonding surface layer that initially consists of amorphous calcium phosphate (ACP), which transforms into hydroxy-carbonate apatite (HCA) with a very similar composition as bone/dentin mineral. Information from various (1)H-based solid-state nuclear magnetic resonance (NMR) experiments was combined to elucidate the evolution of the proton speciations both at the MBG surface and within each ACP/HCA constituent of the biomimetic phosphate layer formed when each of three MBGs with distinct Ca, Si, and P contents was immersed in a simulated body fluid (SBF) for variable periods between 15 min and 30 days. Directly excited magic-angle-spinning (MAS) (1)H NMR spectra mainly reflect the MBG component, whose surface is rich in water and silanol (SiOH) moieties. Double-quantum-single-quantum correlation (1)H NMR experimentation at fast MAS revealed their interatomic proximities. The comparatively minor H species of each ACP and HCA component were probed selectively by heteronuclear (1)H-(31)P NMR experimentation. The initially prevailing ACP phase comprises H2O and "nonapatitic" HPO4(2-)/PO4(3-) groups, whereas for prolonged MBG soaking over days, a well-progressed ACP → HCA transformation was evidenced by a dominating O(1)H resonance from HCA. We show that (1)H-detected (1)H → (31)P cross-polarization NMR is markedly more sensitive than utilizing powder X-ray diffraction or (31)P NMR for detecting the onset of HCA formation, notably so for P-bearing (M)BGs. In relation to the long-standing controversy as to whether bone mineral comprises ACP and/or forms via an ACP precursor, we discuss a recently accepted structural core-shell picture of both synthetic and biological HCA, highlighting the close relationship between the disordered surface layer and ACP.

  1. A (25)Mg, (89)Y and (115)In solid state MAS NMR study of YT2X and Y(T0.5T'0.5)2X (T/T' = Pd, Ag, Au; X = Mg, In) Heusler phases.

    PubMed

    Benndorf, Christopher; Stein, Sebastian; Heletta, Lukas; Kersting, Marcel; Eckert, Hellmut; Pöttgen, Rainer

    2016-12-20

    Yttrium-transition metal-magnesium (indium) Heusler phases YPd2Mg, YPd2In, YAg2Mg, YAg2In, YAu2Mg, and YAu2In and their quaternary compounds (solid solutions) Y(Pd0.5Ag0.5)2Mg, Y(Pd0.5Ag0.5)2In, Y(Pd0.5Au0.5)2Mg, Y(Pd0.5Au0.5)2In, Y(Ag0.5Au0.5)2Mg and Y(Ag0.5Au0.5)2In were synthesized from the elements in sealed niobium ampoules in a high-frequency furnace or by arc-melting, respectively. All compounds crystallize with the cubic MnCu2Al type structure (Heusler phase), space group Fm3[combining macron]m. The structure of Y(Ag0.39Au0.61)2Mg was refined from single crystal X-ray diffractometer data: a = 689.97(5) pm, wR2 = 0.0619, 52 F(2) values, 6 parameters. Magnetic susceptibility measurements show Pauli paramagnetic behavior for all samples. The compounds were investigated by (25)Mg, (89)Y and (115)In solid state MAS NMR spectroscopy. Large positive resonance shifts are observed for all nuclei. A review of the present data in the context of literature data on isotypic Heusler phases with Cd and Sn indicates that the (89)Y shifts show a correlation with the electronegativity of the main group atoms (Mg, Cd, In, Sn). The solid solutions Y(Ag1-xTx)2Mg (x = 0.1, 0.25, 0.33, 0.5; T = Pd, Au) clearly show Vegard-like behavior concerning their lattice parameters, and their main group element resonance shifts arising from spin and orbital contributions are close to the interpolated values of the corresponding end-member compounds.

  2. Direct Observation of Lattice Aluminum Environments in Li Ion Cathodes LiNi 1–yz Co y Al z O 2 and Al-Doped LiNi x Mn y Co z O 2 via 27 Al MAS NMR Spectroscopy

    SciTech Connect

    Dogan, Fulya; Vaughey, John T.; Iddir, Hakim; Key, Baris

    2016-07-06

    Direct observations of local lattice aluminum environments have been a major challenge for aluminum -bearing Li ion battery materials, such as LiNi1-y-zCoyAlzO2 Al(NCA) and aluminum-doped LiNixMnyCozO2 (NMC). Al-27 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is the only structural probe currently available that can qualitatively and quantitatively characterize lattice and nonlattice (i.e., surface, coatings, segregation, secondary phase etc.) aluminum coordination and provide information that helps discern its effect in the lattice. In the present study, we use NMR to gain new insights into transition metal (TM)-O-Al coordination and evolution of lattice aluminum sites upon cycling. With the aid of first-principles DFT calculations, we show direct evidence of lattice Al sites, nonpreferential Ni/Co-O-Al ordering in NCA, and the lack of bulk lattice aluminum in aluminum -"doped" NMC. Aluminum coordination of the paramagnetic (lattice) and diamagnetic (nonlattice) nature is investigated for Al-doped NMC and NCA. For the latter, the evolution of the lattice site(s) upon cycling is also studied. A clear reordering of lattice aluminum environments due to nickel migration is observed in NCA upon extended cycling.

  3. Interplay of charge and spin coherence in Landau-Zener interferometry in double quantum dots

    NASA Astrophysics Data System (ADS)

    Ribeiro, Hugo

    2013-03-01

    Landau-Zener-Stückelberg-Majorana (LZSM) physics has been exploited to coherently manipulate two-electron spin states in a GaAs double quantum dot (DQD) at a singlet (S)-triplet (T+) anti-crossing. The anti-crossing results from the hyperfine interaction with the nuclear spins of the host material. However, the fluctuations of the nuclear spin bath result in spin dephasing within T2* ~ 10 - 20 ns. As a consequence, the sweep through the anti-crossing would have to be performed on a timescale comparable to T2* to achieve LZSM oscillations with 100% visibility. Moreover, the S-T+ anti-crossing is located near the (1 , 1) - (2 , 0) interdot charge transition, where (nl ,nr) denotes the number of electrons in the left and right quantum dot. As a result the singlet state involved in the dynamics is a superpostion of (1 , 1) and (2 , 0) singlet states. Here we show that it is possible to increase the oscillation visibility while keeping sweep times less than T2* using a tailored pulse with a detuning dependent level velocity. The pulse includes a slow level velocity portion that is chosen to coincide with the passage through the S-T+ anti-crossing and two fast level velocity portions. The latter minimize the time spent in regions where spin and charge degrees of freedom are entangled, which renders the qubit susceptible to charge noise. The slow level velocity portion of the pulse results in a stronger effective coupling between the spins states, which increases the oscillations visibility [3,4]. In particular, we were able to obtain a visibility of ~ 0 . 5 for LZSM oscillations. This constitutes an important step towards the implementation of a Hadamard gate. Work performed in collaboration with Jason Petta, Guido Burkard, Hong Lu, and Arthur Gossard. Research at Princeton supported by the Sloan and Packard Foundations and the NSF. H. R. and G. B. acknowledge funding from the DFG within SPP 1285 and SFB 767.

  4. Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe

    NASA Astrophysics Data System (ADS)

    Yakunin, M. V.; Suslov, A. V.; Popov, M. R.; Novik, E. G.; Dvoretsky, S. A.; Mikhailov, N. N.

    2016-02-01

    We present an experimental study of the double-quantum-well (DQW) system made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage Vg. This large overlap manifests itself in a much higher critical field Bc separating the range above it with a plain behavior of the Hall magnetoresistance ρx y(B ) , where the quantum peculiarities shift linearly with Vg, and the range below with a complicated behavior. In the latter case, specific structures in ρx y(B ) are formed like a double-N -shaped ρx y(B ) , reentrant sign-alternating quantum Hall effect with transitions into a zero-filling-factor state, etc., which are clearly manifested here due to better magnetic quantization at high fields, as compared to the features seen earlier in a single HgTe QW. The coexisting electrons and holes were found in the whole investigated range of positive and negative Vg as revealed (i) from fits to the low-field N -shaped ρx y(B ) , (ii) from the Fourier analysis of oscillations in ρx x(B ) , and (iii) from a specific behavior of ρx y(B ) at high positive Vg. A peculiar feature here is that the found electron density n remains almost constant in the whole range of investigated Vg while the hole density p drops down from the value a factor of 6 larger than n at extreme negative Vg to almost zero at extreme positive Vg passing through the charge-neutrality point. We show that this difference between n and p stems from an order of magnitude larger density of states for holes in the lateral valence subband maxima than for electrons in the conduction subband minimum. We analyze our observations on the basis of a calculated picture of magnetic levels in a DQW and suggest that their specificity is due to (i) a nonmonotonic course of the valence subband magnetic levels and an

  5. Magnetic interlayer coupling between Co films across Cu/Ni30Cu70/Cu(100) double quantum wells

    SciTech Connect

    Zhang, Z.D.; Choi, H.J.; Kawakami, R.K.; Escorcia-Aparicio, E.J.; Bowen, M.O.; Rotenberg, E.; Smith, N.V.; Qiu, Z.Q.

    1999-05-18

    Magnetic interlayer coupling between two Co layers across Cu/Ni 30 Cu 70 /Cu(100) was investigated by the surface magneto-optic Kerr effect. The Ni 30 Cu 70 layer at the center of the Cu layer was shown to shift the peak positions, rather than to change the strength, of the magnetic interlayer coupling. The density of states near the Fermi level was investigated by photoemission spectroscopy. We show that the peak-position shift in the magnetic interlayer coupling is associated with the quantum-well behavior in a symmetric double-quantum-well system. The phase accumulation model was applied to explain the results quantitatively.

  6. Interlayer current near the edge of an InAs/GaSb double quantum well in proximity with a superconductor

    NASA Astrophysics Data System (ADS)

    Kononov, A.; Egorov, S. V.; Titova, N.; Semyagin, B. R.; Preobrazhenskii, V. V.; Putyato, M. A.; Emelyanov, E. A.; Deviatov, E. V.

    2017-04-01

    We investigate charge transport through the junction between a niobium superconductor and the edge of a two-dimensional electron-hole bilayer, realized in an InAs/GaSb double quantum well. For the transparent interface with a superconductor, we demonstrate that the junction resistance is determined by the interlayer charge transfer near the interface. From an analysis of experimental I-V curves, we conclude that the proximity-induced superconductivity efficiently couples electron and hole layers at low currents. The critical current demonstrates periodic dependence on the in-plane magnetic field, while it is monotonic for the field that is normal to the bilayer plane.

  7. Double-core excitations in formamide can be probed by X-ray double-quantum-coherence spectroscopy

    PubMed Central

    Zhang, Yu; Healion, Daniel; Biggs, Jason D.; Mukamel, Shaul

    2013-01-01

    The attosecond, time-resolved X-ray double-quantum-coherence four-wave mixing signals of formamide at the nitrogen and oxygen K-edges are simulated using restricted excitation window time-dependent density functional theory and the excited core hole approximation. These signals, induced by core exciton coupling, are particularly sensitive to the level of treatment of electron correlation, thus providing direct experimental signatures of electron and core-hole many-body effects and a test of electronic structure theories. PMID:24981529

  8. Aharonov-Bohm oscillations changed by indirect interdot tunneling via electrodes in parallel-coupled vertical double quantum dots.

    PubMed

    Hatano, T; Kubo, T; Tokura, Y; Amaha, S; Teraoka, S; Tarucha, S

    2011-02-18

    Aharonov-Bohm (AB) oscillations are studied for a parallel-coupled vertical double quantum dot with a common source and drain electrode. We observe AB oscillations of current via a one-electron bonding state as the ground state and an antibonding state as the excited state. As the center gate voltage becomes more negative, the oscillation period is clearly halved for both the bonding and antibonding states, and the phase changes by half a period for the antibonding state. This result can be explained by a calculation that takes account of the indirect interdot coupling via the two electrodes.

  9. Vanishing current hysteresis under competing nuclear spin pumping processes in a quadruplet spin-blockaded double quantum dot

    SciTech Connect

    Amaha, S.; Hatano, T.; Tarucha, S.; Gupta, J. A.; Austing, D. G.

    2015-04-27

    We investigate nuclear spin pumping with five-electron quadruplet spin states in a spin-blockaded weakly coupled vertical double quantum dot device. Two types of hysteretic steps in the leakage current are observed on sweeping the magnetic field and are associated with bidirectional polarization of nuclear spin. Properties of the steps are understood in terms of bias-voltage-dependent conditions for the mixing of quadruplet and doublet spin states by the hyperfine interaction. The hysteretic steps vanish when up- and down-nuclear spin pumping processes are in close competition.

  10. Observation of hysteretic transport due to dynamic nuclear spin polarization in a GaAs lateral double quantum dot.

    PubMed

    Kobayashi, Takashi; Hitachi, Kenichi; Sasaki, Satoshi; Muraki, Koji

    2011-11-18

    We report a new transport feature in a GaAs lateral double quantum dot that emerges for magnetic-field sweeps and shows hysteresis due to dynamic nuclear spin polarization (DNP). This DNP signal appears in the Coulomb blockade regime by virtue of the finite interdot tunnel coupling and originates from the crossing between ground levels of the spin triplet and singlet extensively used for nuclear spin manipulations in pulsed-gate experiments. The magnetic-field dependence of the current level is suggestive of unbalanced DNP between the two dots, which opens up the possibility of controlling electron and nuclear spin states via dc transport.

  11. Charge Number Dependence of the Dephasing Rates of a Graphene Double Quantum Dot in a Circuit QED Architecture.

    PubMed

    Deng, Guang-Wei; Wei, Da; Johansson, J R; Zhang, Miao-Lei; Li, Shu-Xiao; Li, Hai-Ou; Cao, Gang; Xiao, Ming; Tu, Tao; Guo, Guang-Can; Jiang, Hong-Wen; Nori, Franco; Guo, Guo-Ping

    2015-09-18

    We use an on-chip superconducting resonator as a sensitive meter to probe the properties of graphene double quantum dots at microwave frequencies. Specifically, we investigate the charge dephasing rates in a circuit quantum electrodynamics architecture. The dephasing rates strongly depend on the number of charges in the dots, and the variation has a period of four charges, over an extended range of charge numbers. Although the exact mechanism of this fourfold periodicity in dephasing rates is an open problem, our observations hint at the fourfold degeneracy expected in graphene from its spin and valley degrees of freedom.

  12. Effects of electromagnetic fields on the nonlinear optical properties of asymmetric double quantum well under intense laser field

    NASA Astrophysics Data System (ADS)

    Yesilgul, U.; Sari, H.; Ungan, F.; Martínez-Orozco, J. C.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.; Sökmen, I.

    2017-03-01

    In this study, the effects of electric and magnetic fields on the optical rectification and second and third harmonic generation in asymmetric double quantum well under the intense non-resonant laser field is theoretically investigated. We calculate the optical rectification and second and third harmonic generation within the compact density-matrix approach. The theoretical findings show that the influence of electric, magnetic, and intense laser fields leads to significant changes in the coefficients of nonlinear optical rectification, second and third harmonic generation.

  13. Indirectly detected chemical shift correlation NMR spectroscopy in solids under fast magic angle spinning

    SciTech Connect

    Mao, Kanmi

    2011-01-01

    on decoupling efficiency as well as scaling factors. Indirect detection with assistance of PMLGm$\\bar{x}$ during INEPTR transfer proved to offer the highest sensitivity gains of 3-10. In addition, the CRAMPS sequence was applied under fast MAS to increase the 1H resolution during t1 evolution in the traditional, 13C detected HETCOR scheme. Two naturally abundant solids, tripeptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (f-MLF-OH) and brown coal, with well ordered and highly disordered structures, respectively, are studied to confirm the capabilities of these techniques. Concomitantly, a simple optimization of 1H homonuclear dipolar decoupling at MAS rates exceeding 10 kHz was developed (Chapter 4). The fine-tuned decoupling efficiency can be obtained by minimizing the signal loss due to transverse relaxation in a simple spin-echo experiment, using directly the sample of interest. The excellent agreement between observed decoupling pattern and earlier theoretical predictions confirmed the utility of this strategy. The properties of naturally abundant surface-bound fluorocarbon groups in mesoporous silica nanoparticles (MSNs) were investigated by the above-mentioned multidimensional solid-state NMR experiments and theoretical modeling (Chapter 5). Two conformations of (pentafluorophenyl)propyl groups (abbreviated as PFP) were determined as PFP-prone and PFP-upright, whose aromatic rings are located above the siloxane bridges and in roughly upright position, respectively. Several 1D and 2D NMR techniques were implemented in the characterizations, including indirectly detected 1H{l_brace}13C{r_brace} and 19F{l_brace}13C{r_brace} 2D HETCOR, Carr-Purcell-Meiboom-Gill (CPMG) assisted 29Si direct polarization and 29Si19F 2D experiments, 2D double-quantum (DQ) 19F MAS NMR spectra and spin-echo measurements

  14. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1989-01-01

    This report covers the progress made on the title project during the past reporting 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 in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines the authors are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. The authors have been reinvestigating the prospects of using zero field NMR types of techniques for two dimensional NMR structural analysis of complex organic solids such as coals. Currently MAS spin rates are not sufficiently high to permit zero field in high field NMR for protons in typical organic solids, however they are compatible with {sup 13}C-{sup 13}C dipolar couplings. In collaboration with Dr. Robert Tycko of AT T Bell Laboratories, inventor of the zero field in high field NMR method, the authors have performed the first zero field in high field {sup 13}C NMR experiments. These results are described. 9 refs., 2 figs.

  15. An equation of motion analysis of the two stage Kondo effect in T-shaped double-quantum-dot systems

    NASA Astrophysics Data System (ADS)

    Crisan, M.; Grosu, I.; Ţifrea, I.

    2015-02-01

    We use the equation of motion method in connection with a generalized Anderson Hamiltonian to evaluate the electronic transmission in a T-shaped double quantum dot system. We consider the strong Coulomb interaction regime (U1 → ∞, U2 → ∞) using a decoupling procedure that includes terms beyond the standard Hartree-Fock approximation. The typical manifestation of the two stage Kondo effect is reflected in system's electronic transmission coefficient that presents both a large Lorentzian and a sharp dip around ω = 0. We provide an analytical result for the first stage Kondo temperature that includes corrections due to the presence of an additional quantum dot in the system. For the second stage Kondo effect, we identify the logarithmic correction that is responsible for the additional dip in the system's electronic transmission coefficient. The Anderson model is used in connection with the T-shaped double-quantum-dot system. We include terms beyond Hartree-Fock approximation for the equation of motion method. We evaluate the first stage Kondo temperature in the strong Coulomb interaction limit.

  16. Tunable photonic cavity coupled to a voltage-biased double quantum dot system: Diagrammatic nonequilibrium Green's function approach

    NASA Astrophysics Data System (ADS)

    Agarwalla, Bijay Kumar; Kulkarni, Manas; Mukamel, Shaul; Segal, Dvira

    2016-07-01

    We investigate gain in microwave photonic cavities coupled to voltage-biased double quantum dot systems with an arbitrarily strong dot-lead coupling and with a Holstein-like light-matter interaction, by employing the diagrammatic Keldysh nonequilibrium Green's function approach. We compute out-of-equilibrium properties of the cavity: its transmission, phase response, mean photon number, power spectrum, and spectral function. We show that by the careful engineering of these hybrid light-matter systems, one can achieve a significant amplification of the optical signal with the voltage-biased electronic system serving as a gain medium. We also study the steady-state current across the device, identifying elastic and inelastic tunneling processes which involve the cavity mode. Our results show how recent advances in quantum electronics can be exploited to build hybrid light-matter systems that behave as microwave amplifiers and photon source devices. The diagrammatic Keldysh approach is primarily discussed for a cavity-coupled double quantum dot architecture, but it is generalizable to other hybrid light-matter systems.

  17. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1989-01-01

    This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concern how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines we are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. During the last quarter the authors have concentrated on improvements in cross polarization (CP) sequences with a goal of making the CP process insensitive to experimental conditions such as the magic angle spinning (MAS) rate. In order to be able to use fields the order of 7.0 T or higher, CP efficiency must be maintained at MAS rates of over 10 kHz. The standard sequences have severe limitations at these rates which lead to intensity distortions in {sup 13}C CPMAS spectra. Thus in order to be able to take advantage of the increases in sensitivity and resolution that accompany high field operation, improvements in the NMR methods are required. The new sequences the authors are developing will be especially important for quantitative analysis of coal structure by {sup 13}C solid state NMR at high field strengths. 13 refs., 7 figs., 2 tabs.

  18. (1)H-(2)H cross-polarization NMR in fast spinning solids by adiabatic sweeps.

    PubMed

    Wi, Sungsool; Schurko, Robert; Frydman, Lucio

    2017-03-14

    Cross-polarization (CP) experiments employing frequency-swept radiofrequency (rf) pulses have been successfully used in static spin systems for obtaining broadband signal enhancements. These experiments have been recently extended to heteronuclear I, S = spin-1/2 nuclides under magic-angle spinning (MAS), by applying adiabatic inversion pulses along the S (low-γ) channel while simultaneously applying a conventional spin-locking pulse on the I-channel ((1)H). This study explores an extension of this adiabatic frequency sweep concept to quadrupolar nuclei, focusing on CP from (1)H (I = 1/2) to (2)H spins (S = 1) undergoing fast MAS (νr = 60 kHz). A number of new features emerge, including zero- and double-quantum polarization transfer phenomena that depend on the frequency offsets of the swept pulses, the rf pulse powers, and the MAS spinning rate. An additional mechanism found operational in the (1)H-(2)H CP case that was absent in the spin-1/2 counterpart, concerns the onset of a pseudo-static zero-quantum CP mode, driven by a quadrupole-modulated rf/dipolar recoupling term arising under the action of MAS. The best CP conditions found at these fast spinning rates correspond to double-quantum transfers, involving weak (2)H rf field strengths. At these easily attainable (ca. 10 kHz) rf field conditions, adiabatic level-crossings among the {|1⟩,|0⟩,|-1⟩} mS energy levels, which are known to complicate the CP MAS of quadrupolar nuclei, are avoided. Moreover, the CP line shapes generated in this manner are very close to the ideal (2)H MAS spectral line shapes, facilitating the extraction of quadrupolar coupling parameters. All these features were corroborated with experiments on model compounds and justified using numerical simulations and average Hamiltonian theory models. Potential applications of these new phenomena, as well as extensions to higher spins S, are briefly discussed.

  19. 1H-2H cross-polarization NMR in fast spinning solids by adiabatic sweeps

    NASA Astrophysics Data System (ADS)

    Wi, Sungsool; Schurko, Robert; Frydman, Lucio

    2017-03-01

    Cross-polarization (CP) experiments employing frequency-swept radiofrequency (rf) pulses have been successfully used in static spin systems for obtaining broadband signal enhancements. These experiments have been recently extended to heteronuclear I, S = spin-1/2 nuclides under magic-angle spinning (MAS), by applying adiabatic inversion pulses along the S (low-γ) channel while simultaneously applying a conventional spin-locking pulse on the I-channel (1H). This study explores an extension of this adiabatic frequency sweep concept to quadrupolar nuclei, focusing on CP from 1H (I = 1/2) to 2H spins (S = 1) undergoing fast MAS (νr = 60 kHz). A number of new features emerge, including zero- and double-quantum polarization transfer phenomena that depend on the frequency offsets of the swept pulses, the rf pulse powers, and the MAS spinning rate. An additional mechanism found operational in the 1H-2H CP case that was absent in the spin-1/2 counterpart, concerns the onset of a pseudo-static zero-quantum CP mode, driven by a quadrupole-modulated rf/dipolar recoupling term arising under the action of MAS. The best CP conditions found at these fast spinning rates correspond to double-quantum transfers, involving weak 2H rf field strengths. At these easily attainable (ca. 10 kHz) rf field conditions, adiabatic level-crossings among the {|1 ⟩ ,|0 ⟩ ,|-1 ⟩ } mS energy levels, which are known to complicate the CP MAS of quadrupolar nuclei, are avoided. Moreover, the CP line shapes generated in this manner are very close to the ideal 2H MAS spectral line shapes, facilitating the extraction of quadrupolar coupling parameters. All these features were corroborated with experiments on model compounds and justified using numerical simulations and average Hamiltonian theory models. Potential applications of these new phenomena, as well as extensions to higher spins S, are briefly discussed.

  20. Implementing SPAM into STMAS: A net sensitivity improvement in high-resolution NMR of quadrupolar nuclei

    NASA Astrophysics Data System (ADS)

    Amoureux, J. P.; Delevoye, L.; Fink, G.; Taulelle, F.; Flambard, A.; Montagne, L.

    2005-08-01

    Gan and Kwak recently introduced two new tools for high-resolution 2D NMR methods applied to quadrupolar nuclei: double-quantum filtering in STMAS (DQF-STMAS) and the soft-pulse added mixing (SPAM) idea. Double-quantum filtering suppresses all undesired signals in the STMAS method with limited loss in sensitivity. With SPAM, all pathways are added constructively after the second hard-pulse instead of using a single pathway as previously. Here, the sensitivity, advantages and drawbacks of DQF-STMAS are compared to 3QMAS. Additionally, SPAM can be included into DQF-STMAS method, resulting in a net sensitivity gain with respect to 3QMAS of ca. 10-15.