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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Dynamics of asymmetric non-polymeric binary glass formers—A nuclear magnetic resonance and dielectric spectroscopy study

We study a dynamically asymmetric binary glass former with the low-T{sub g} component m-tri-cresyl phosphate (m-TCP: T{sub g} = 206 K) and a spirobichroman derivative as a non-polymeric high-T{sub g} component (T{sub g} = 382 K) by means of {sup 1}H nuclear magnetic resonance (NMR), {sup 31}P NMR, and dielectric spectroscopy which allow component-selectively probing the dynamics. The entire concentration range is covered, and two main relaxation processes with two T{sub g} are identified, T{sub g1} and T{sub g2}. The slower one is attributed to the high-T{sub g} component (α{sub 1}-process), and the faster one is related to the m-TCP molecules (α{sub 2}-process). Yet, there are indications that a small fraction of m-TCP is associated also with the α{sub 1}-process. While the α{sub 1}-relaxation only weakly broadens upon adding m-TCP, the α{sub 2}-relaxation becomes extremely stretched leading to quasi-logarithmic correlation functions at low m-TCP concentrations—as probed by {sup 31}P NMR stimulated echo experiments. Frequency-temperature superposition does not apply for the α{sub 2}-process and it reflects an isotropic, liquid-like motion which is observed even below T{sub g1}, i.e., in the matrix of the arrested high-T{sub g} molecules. As proven by 2D {sup 31}P NMR, the corresponding dynamic heterogeneities are of transient nature, i.e., exchange occurs within the distribution G(lnτ{sub α2}). At T{sub g1} a crossover is found for the temperature dependence of (mean) τ{sub α2}(T) from non-Arrhenius above to Arrhenius below T{sub g1} which is attributed to intrinsic confinement effects. This “fragile-to-strong” transition also leads to a re-decrease of T{sub g2}(c{sub m−TCP}) at low concentration c{sub m−TCP}, i.e., a maximum is observed in T{sub g2}(c{sub m−TCP}) while T{sub g1}(c{sub m−TCP}) displays the well-known plasticizer effect. Although only non-polymeric components are involved, we re-discover essentially all features previously reported for polymer-plasticizer systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

Studies related to primitive chemistry. A proton and nitrogen-14 nuclear magnetic resonance amino acid and nucleic acid constituents and a and their possible relation to prebiotic

Preliminary proton nuclear magnetic resonance (NMR) studies were made to determine the applicability of this technique for the study of interactions between monomeric and polymeric amino acids with monomeric nucleic acid bases and nucleotides. Proton NMR results for aqueous solutions (D2O) demonstrated interactions between the bases cytosine and adenine and acidic and aromatic amino acids. Solutions of 5'-AMP admixed with amino acids exhibited more complex behavior but stacking between aromatic rings and destacking at high amino acids concentration was evident. The multisite nature of 5'-AMP was pointed out. Chemical shift changes for adenine and 5'-AMP with three water soluble polypeptides demonstrated that significant interactions exist. It was found that the linewidth-pH profile of each amino acid is unique. It is concluded that NMR techniques can give significant and quantitative data on the association of amino acid and nucleic acid constituents.

Manatt, S. L.↗
DOE OSTI2015

Material degradation of liquid organic semiconductors analyzed by nuclear magnetic resonance spectroscopy

Liquid organic light-emitting diodes (liquid OLEDs) are unique devices consisting only of liquid organic semiconductors in the active layer, and the device performances have been investigated recently. However, the device degradation, especially, the origin has been unknown. In this study, we show that material degradation occurs in liquid OLEDs, whose active layer is composed of carbazole with an ethylene glycol chain. Nuclear magnetic resonance (NMR) experiments clearly exhibit that the dimerization reaction of carbazole moiety occurs in the liquid OLEDs during driving the devices. In contrast, cleavages of the ethylene glycol chain are not detected within experimental error. The dimerization reaction is considered to be related to the device degradation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Nuclear Magnetic Resonance Spectra of Polyhydroxylated Fullerene C{sub 60}(OH){sub n}

Polyhydroxylated fullerene C{sub 60}(OH){sub n} (with an estimated number of hydroxyl groups n = 38–44) synthesized from pure fullerene by mixing a benzene solution of C{sub 60} with a NaOH aqueous solution in the presence of a catalyst was studied with {sup 1}H and {sup 13}C solid-state nuclear magnetic resonance. Possible features of the structure of a molecule shell were revealed from {sup 1}H NMR data. The {sup 13}C spectrum showed a peak splitting with an increase in temperature, which is probably due to fullerenol isomers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Quantifying Dynamic Water Storage in Unsaturated Bedrock with Borehole Nuclear Magnetic Resonance

Quantifying the volume of water that is stored in the subsurface is critical to studies of water availability to ecosystems, slope stability, and water-rock interactions. In a variety of settings, water is stored in fractured and weathered bedrock as rock moisture. However, few techniques are available to measure rock moisture in unsaturated rock, making direct estimates of water storage dynamics difficult to obtain. Here, we use borehole nuclear magnetic resonance (NMR) at two sites in seasonally dry California to quantify dynamic rock moisture storage. Additionally, we show strong agreement between NMR estimates of dynamic storage and estimates derived from neutron logging and mass balance techniques. The depths of dynamic storage are up to 9 m and likely reflect the depth extent of root water uptake. To our knowledge, these data are the first to quantify the volume and depths of dynamic water storage in the bedrock vadose zone via NMR.

58 GEOSCIENCES↗
DOE OSTI2022

Solid-State Nuclear Magnetic Resonance as a Tool to Probe the Impact of Mechanical Preprocessing on the Structure and Arrangement of Plant Cell Wall Polymers

Efficient separation of the plant cell wall polymers during lignocellulose processing has been historically challenging due to insolubility of the polymers and their propensity for recalcitrant reassembly. Methods, such as “lignin first” extraction techniques, have advanced efficient biomass use, but the molecular mechanisms for recalcitrance remain enigmatic. Here, we discuss how solid-state Nuclear Magnetic Resonance (NMR) approaches report on the 3D organization of cellulose, xylan, and lignin in the plant cell wall. Recent results illustrate that the organization of these polymers varies across biomass sources and sample preparation methods, with even minimal physical processing causing significant effects. These structural differences contribute to variable extraction efficiencies for bioproducts after downstream processing. We propose that solid-state NMR methods can be applied to follow biomass processing, providing an understanding of the polymer rearrangements that can lead to poor yields for the desired bioproducts. The utility of the technique is illustrated for mechanical processing using lab-scale vibratory ball milling of Sorghum bicolor .

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Analysis of Glycolate in Radioactive Waste by Ion Chromatography (IC) and Proton Nuclear Magnetic Resonance (H NMR)

Here, in preparation for implementing the Nitric-Glycolic (NG) acid flowsheet for the Savannah River Site (SRS) Liquid Waste System (LWS), analytical methods for determining glycolate at low concentration, below 20 mg/L in radioactive samples, were developed to support system management and safety. To accommodate the wide range of LWS matrix conditions, two alternative methods were developed, refined, and demonstrated for glycolate analysis in radioactive waste samples: ion chromatography (IC) and a proton nuclear magnetic resonance (H NMR). Investigators validated IC and H NMR methods for glycolate analysis, defined the range of applicability, and demonstrated key supporting analytical protocols. The deployed IC method is applicable in low to moderate ionic strength samples and requires sample pretreatment using a Dionex OnGuard II H + cartridge. The deployed H NMR method is more labor intensive but provides options for a broader range of matrices. Based on the results, high quality glycolate analysis of the Defense Waste Processing Facility (DWPF) condensate in Tank 22 is feasible by IC down to approximately 12 mg/L. Using H NMR, glycolate may be determined to 8 mg/L or lower depending on the run time with the potential for broader applicability of the method to higher ionic strength conditions in other tanks of the SRS LWS.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2015

Absolute shielding scales for Al, Ga, and In and revised nuclear magnetic dipole moments of {sup 27}Al, {sup 69}Ga, {sup 71}Ga, {sup 113}In, and {sup 115}In nuclei

We present coupled cluster calculations of NMR shielding constants of aluminum, gallium, and indium in water-ion clusters. In addition, relativistic and dynamical corrections and the influence of the second solvation shell are evaluated. The final NMR shielding constants define new absolute shielding scales, 600.0 ± 4.1 ppm, 2044.4 ± 31.4 ppm, and 4507.7 ± 63.7 ppm for aluminum, gallium, and indium, respectively. The nuclear magnetic dipole moments for {sup 27}Al, {sup 69}Ga, {sup 71}Ga, {sup 113}In, and {sup 115}In isotopes are corrected by combining the computed shielding constants with experimental NMR frequencies. The absolute magnitude of the correction increases along the series and for indium isotopes it reaches approximately −8.0 × 10{sup −3} of the nuclear magneton.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Revealing Molecular Mechanisms in Hierarchical Nanoporous Carbon via Nuclear Magnetic Resonance

Hierarchical nanoporous carbons (HNC) have been proven to be an effective adsorbent for the adsorption of volatile organic compounds (VOCs) and CO 2 . However, questions remain regarding the hierarchical structure regulation, the adsorption mechanisms of adsorbate uptake, and interactions within the HNC. Here, we synthesize HNC from wood, using a microwave-induced heating method incorporating K 2 CO 3 activation. Our HNC exhibit Murray's law multiscale structures, prompting a molecular-scale study of adsorbate adsorption via nuclear magnetic resonance (NMR). NMR chemical shifts are consistent with ring-current effects from the adsorbent. Our NMR technique provides a convenient way to quantitate adsorption of adsorbate in HNC. VOC vapor adsorption results show NMR chemical-shift changes with time, suggesting initial adsorption into mesopores, followed by diffusion into micropores. Schroeder's paradox is demonstrated by differences in observed shifts for adsorbed liquid vis-à-vis vapor phase in these HNC. These HNC show high CO 2 adsorption capacity, portending applications to carbon capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Monitoring the internal swelling in cementitious mortars with single-sided 1H nuclear magnetic resonance

Moisture transport into concrete and mortar surfaces strongly influences the durability of structures. Transport processes are foremost controlled by the material's porosity. Cementitious materials, such as concrete and mortars, exhibit distinct changes in pore structure while drying and subsequent rewetting due to the internal shrinkage and swelling of the layered calcium-silicate hydrates. Mortars with different w/c-ratios and binders were dried and rewetted and the subsequent time dependent changes in water filled pore structure were monitored with single-sided {sup 1}H nuclear magnetic resonance. This technique combines a localized depiction of all pore water with a good time resolution. The NMR signal is split into the four pore species C-S-H interlayer water, gel pore water, interhydrate water, and capillary water by multi-exponential analysis. Two consecutive running processes in the swelling of cementitious mortars were identified and discussed based on recent models of the cement microstructure as well as its implications on the sorptivity.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Surface Terminations of LaAlO 3 Perovskite Nanoparticles as Viewed by Solid-State Nuclear Magnetic Resonance

Nanocrystal surfaces generally undergo reconstructions that differentiate them from the bulk structures, often in nontrivial ways. Understanding these terminations is critical across diverse fields, from heterogeneous catalysis to the formation of topological states and the synthesis of semiconductor nanomaterials. Determining surface structures is currently an interdisciplinary task, most often involving high-resolution electron microscopy and surface electron diffraction. These methods, however, do not provide a global view of the ensemble of structures present in a sample. Here, we show how surface-sensitive solid-state nuclear magnetic resonance (SSNMR) spectroscopy methods can bridge this gap. In this context, we investigated the surface structure of lanthanum aluminate (LaAlO 3 ) perovskite nanoparticles. Four distinct surface terminations have previously been observed for this material, but their relative abundances were unknown. Using an array of double- and triple-resonance SSNMR methods probing the relative proximities of surface 1 H, 27 Al, 17 O, and 139 La nuclei, we conclude the surface to be majority terminated (80%) by AlO x with substantial (20%) LaO x terminated regions.

Materials↗
DOE OSTI2024

Structural Studies of Alloyed and Nanoparticle Transition Metal Dichalcogenides by Selenium-77 Solid-State Nuclear Magnetic Resonance Spectroscopy

Layered transition metal dichalcogenides (TMDCs) such as MoS 2 , MoSe 2 , and WSe 2 are under intense investigation because they are atomically thin semiconductors with photophysical properties that can be tuned by changing their composition or morphology. Mechanochemical processing has been proposed as a method to obtain alloyed TMDCs in the series Mo 1–x W x S y Se 2–y (x = 0–1; y = 0–2). However, elucidating the chemical transformations occurring at the atomic scale following mechanochemical processing can be challenging because the products are often amorphous or microcrystalline. To address this challenge, we probe TMDC mixing and alloying by using a combination of powder X-ray diffraction, Raman spectroscopy, diffuse reflectance spectroscopy, 77 Se solid-state nuclear magnetic resonance (SSNMR) spectroscopy, and planewave density functional theory (DFT) calculations. The nature of the milling material and reaction atmosphere are shown to be essential factors in limiting the formation of undesired oxide byproducts. We demonstrate acquisition of 77 Se SSNMR spectra using different combinations of Carr-Purcell Meiboom-Gill acquisition (CPMG) pulse sequences, magic angle spinning (MAS), and MAS dynamic nuclear polarization. Further, the combination of SSNMR with the other characterization methods clearly demonstrates that high energy impact ball milling induces molecular level alloying of Mo, W and chalcogen atoms in the family Mo 1–x W x S y Se 2–y . Gauge including projector augmented wave DFT calculations yield accurate 77 Se chemical shift (CS) tensor components. 77 Se SSNMR spectroscopy was also applied to study the structure of WSe 2 nanocrystals intercalated with ethylenediamine. The intercalated WSe 2 nanocrystals exhibit a more positive isotropic 77 Se CS as compared to bulk WSe 2 , however, the 77 Se CS anisotropy is the same, confirming the WSe 2 layers have a similar structure as in their bulk counterparts.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Determination of Phase Composition of Cobalt Nanoparticles Using {sup 59}Co Internal Field Nuclear Magnetic Resonance

It is well known that cobalt exhibits polymorphism, i.e., the co-existence of both the hcp and fcc phases. In particular, the method of synthesis and other thermodynamic conditions is known to play a crucial role in determining the particular phase of cobalt. In this work, we have compared the phase composition of the cobalt nanoparticles synthesized using two different solvents (water) and ethanol (Co@C). XRD measurements confirm the existence of fcc phase in commercial cobalt nanoparticles (Co@A), co-existence of fcc and hcp phases in Co@B, while the existence of the hcp phase in Co@C. We have studied these cobalt nanoparticles using {sup 59}Co internal field nuclear magnetic resonance (IFNMR) for verification of phase composition. Our studies reveal that the Co@A has fcc as a major phase with minor quantity hcp phase. Co@B exhibits approximately equal amount of fcc and hcp phase while Co@C exhibits hcp as a major phase with minor fcc phase. Our SEM micrograph studies confirm that the cobalt particles have spherical shape in the fcc phase. The cobalt particles exhibit both spherical and dendrite morphology confirming the co-existence of fcc and hcp phases, while the sample with pure hcp phase exhibits the dendrite morphology. Our studies also throw light on understanding the effect of solvent in the phase formation of the cobalt nanoparticles.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Evaluation of hydrogen storage in sandstone reservoirs using 1 H nuclear magnetic resonance spectroscopy

Evaluation of the hydrogen storage capacity of porous rocks is crucial for underground hydrogen storage. Using 1 H nuclear magnetic resonance (NMR) spectroscopy, we successfully characterized the hydrogen responses and identified storage mechanisms in Berea sandstone under varying water saturation. Here, the results indicate that the injected hydrogen behaves as a free gas phase and is capable of occupying the empty pore volume regardless of the saturation state. No hysteresis was observed during injection and production cycles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1985

Introduction to Nuclear Magnetic Resonance

The purpose of this paper is to try to give a short overview of what the status is on nuclear magnetic resonance (NMR). It's a subject where one really has to spend some time to look at the physics in detail to develop a proper working understanding. I feel it's not appropriate to present to you density matrices, Hamiltonians of all sorts, and differential equations representing the motion of spins. I'm really going to present some history and status, and show a few very simple concepts involved in NMR. It is a form of radio frequency spectroscopy and there are a great number of nuclei that can be studied very usefully with the technique. NMR requires a magnet, a r.f. transmitter/receiver system, and a data acquisition system.

Manatt, Stanley L.↗
DOE OSTI2018

Nuclear magnetic shielding constants of Dirac one-electron atoms in some low-lying discrete energy eigenstates

We present tabulated data for the nuclear magnetic shielding constants (σ) of the Dirac one-electron atoms with a pointlike, motionless and spinless nucleus of charge Ze. Utilizing the exact general analytical formula for σ derived by us (Stefańska, 2016) valid for an arbitrary discrete energy eigenstate, we have computed the numerical values of the magnetic shielding factors for the ground state and for the first and the second set of excited states, i.e.: 2s{sub 1∕2}, 2p{sub 1∕2}, 2p{sub 3∕2}, 3s{sub 1∕2}, 3p{sub 1∕2}, 3p{sub 3∕2}, 3d{sub 3∕2}, and 3d{sub 5∕2}, of the relativistic hydrogenic ions with the nuclear charge numbers from the range 1⩽Z⩽137. The comparisons of our results with the numerical values reported by other authors for some atomic states are also presented.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Characterization of Red/Green Cyanobacteriochrome NpR6012g4 by Solution Nuclear Magnetic Resonance Spectroscopy: A Hydrophobic Pocket for the C15- E,anti Chromophore in the Photoproduct

Cyanobacteriochromes (CBCRs) are cyanobacterial photosensory proteins distantly related to phytochromes. Like phytochromes, CBCRs reversibly photoconvert between a dark-stable state and a photoproduct via photoisomerization of the 15,16-double bond of their linear tetrapyrrole (bilin) chromophores. CBCRs provide cyanobacteria with complete coverage of the visible spectrum and near-ultraviolet region. One CBCR subfamily, the canonical red/green CBCRs typified by AnPixJg2 and NpR6012g4, can function as sensors of light color or intensity because of their great variation in photoproduct stability. The mechanistic basis for detection of green light by the photoproduct state in this subfamily has proven to be a challenging research topic, with competing hydration and trapped-twist models proposed. Here, we use 13 C-edited and 15 N-edited 1 H- 1 H NOESY solution nuclear magnetic resonance spectroscopy to probe changes in chromophore configuration and protein-chromophore interactions in the NpR6012g4 photocycle. Our results confirm a C15-Z,anti configuration for the red-absorbing dark state and reveal a C15-E,anti configuration for the green-absorbing photoproduct. The photoactive chromophore D-ring is located in a hydrophobic environment in the photoproduct, surrounded by both aliphatic and aromatic residues. Here, characterization of variant proteins demonstrates that no aliphatic residue is essential for photoproduct tuning. Taken together, our results support the trapped-twist model over the hydration model for the red/green photocycle of NpR6012g4.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Characterization of Red/Green Cyanobacteriochrome NpR6012g4 by Solution Nuclear Magnetic Resonance Spectroscopy: A Protonated Bilin Ring System in Both Photostates

Cyanobacteriochromes (CBCRs) are cyanobacterial photoreceptors distantly related to phytochromes. Both CBCRs and phytochromes use photoisomerization of a linear tetrapyrrole (bilin) chromophore to photoconvert between two states with distinct spectral and biochemical properties, the dark state and the photoproduct. The isolated CBCR domain NpR6012g4 from Nostoc punctiforme is a well-characterized member of the canonical red/green CBCR subfamily, photosensory domains that can function as sensors for light color or intensity to regulate phototactic responses of filamentous cyanobacteria. Such red/green CBCRs utilize conserved Phe residues to tune the photoproduct for green light absorption, but conflicting interpretations of the photoproduct chromophore structure have been proposed. In the hydration model, the proposed photoproduct state is extensively solvated, with a loosely bound, conformationally flexible chromophore. In the trapped-twist model, the photoproduct chromophore is sterically constrained by hydrophobic amino acids, including the known Phe residues. Here, we have characterized chromophore structure in NpR6012g4 using solution nuclear magnetic resonance spectroscopy and a series of labeled chromophores. Four NH resonances are assigned for both the red-absorbing dark state and the green-absorbing photoproduct. Moreover, observed 13 C chemical shifts are in good agreement with those obtained for protonated rather than deprotonated bilins in ab initio calculations. Our results demonstrate that NpR6012g4 has a protonated, cationic bilin π system in both photostates, consistent with a photoproduct structure in which the chromophore is not extensively hydrated.

59 BASIC BIOLOGICAL SCIENCES↗