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We investigated whether magnetic resonance imaging can visualize the distribution in the vitreous cavity via eye drops of ophthalmic solutions, gadolinium-based contrast agent, and 17O-water, and to clarify the usefulness of ultra-heavily T2-weighted sequences in the research of intraocular distribution. Five different solutions (V-ROHTO, TRAVATANZ, gadobutrol, H217O, and saline) were administered to excised pig eye specimens. The samples were scanned using T1 mapping, T2 mapping, 3D T2-weighted (echo times (TE): 500, 3200, and 4500 ms), a half-Fourier single-shot turbo-spin echo sequence (HASTE; TE: 440 and 3000 ms), and 3D-real inversion-recovery before eye drops administration. Subsequently, we used a plastic dropper to drop a 0.5 mL solution each, and images were obtained up to 26 h later. Temporal changes in the T1 and T2 values of the anterior chamber and vitreous cavity were compared. The other sequences were evaluated by determining temporal signal changes as signal intensity ratio (SIR) compared to "No drop." The T1 and T2 values of samples treated with gadobutrol and H217O decreased over time. The SIR of samples treated with gadobutrol and H217O showed remarkable changes in the 3D T2-weighted images, whereas no remarkable temporal changes were observed in the other solutions. Longer TEs resulted in remarkable changes. We demonstrated that visualization of distribution in the vitreous cavity via eye drops could be achieved with excised pig eyes using gadobutrol and H217O, but not with ophthalmic solutions. Ultra-heavily T2-weighted sequences may be promising for the early and highly sensitive visualization of the intraocular distribution of eye drops. [ABSTRACT FROM AUTHOR]

The Zr‐based Metal Organic Framework (MOF) UiO‐66(Zr) is widely employed owing to its good thermal and chemical stabilities. Although the long‐range structure of this MOF is preserved in the presence of water during several days, little is known about the formation of defects, which cannot be detected using diffraction techniques. We apply here 17O solid‐state NMR spectroscopy at 18.8 T to investigate the reactivity of UiO‐66, through the exchange of oxygen atoms between the different sites of the MOF and water. For that purpose, we have selectively enriched in 17O isotope the carboxylate groups of UiO‐66(Zr) by using it with 17O‐labeled terephthalic acid prepared using mechanochemistry. In the presence of water at 50 °C and a following dehydration at 150 °C, we observe an overall exchange of O atoms between COO− and μ3‐O2− sites. Furthermore, we demonstrate that the three distinct oxygen sites, μ3‐OH, μ3‐O2− and COO−, of UiO‐66(Zr) MOF can be enriched in 17O isotope by post‐synthetic hydrothermal treatment in the presence of 17O‐enriched water. These results demonstrate the lability of Zr−O bonds and the reactivity of UiO‐66(Zr) with water. [ABSTRACT FROM AUTHOR]

Proton nuclear (1H) is the observed nucleus on which most magnetic resonance imaging (MRI) applications depend. Most traditional 1H MRI can provide structural and functional information about organisms, while various non-proton nuclei (X-nuclei) MRI can provide more metabolic information. However, due to the relatively poor signal-to-noise ratio (SNR) of X-nuclei MRI, their applications are quite rare compared to 1H. Benefit from the rapid developments of MRI hardware and software technologies, X-nuclei MRI has recently attracted increasing interests in biomedical research. This review firstly introduces some current methods to improve the SNR of X-nuclei MRI. Secondly, this review describes biomedical applications of X-nuclei MRI, especially focusing on the current use of X-nuclei (13C, 17O, 19F, 23Na and 31P) MRI to study related diseases in different organs, including the brain, liver, kidney, heart and bone. Finally, perspectives studies on X-nuclei imaging and its potential applications are described in biomedical research.

Abstract Two cap carbonates overlying Cryogenian panglacial deposits are found in North‐East Svalbard of which the younger (635 Ma) forms the base of the Ediacaran Period. It is represented by a transgressive succession in which laminated dolostone, typically around 20 m thick (Member D1), is succeeded transitionally by a similar thickness of impure carbonates (Member D2). In Spitsbergen, there is evidence of microbially influenced sediment stabilisation and carbonate precipitation in the lower part of D1, whilst the upper part of D1 and D2 show centimetre‐decimetre‐scale graded units with undulatory lamination interpreted as evidence of storm activity. Carbonate originated as possible freshwater whitings, as well as microbial precipitates. Exhumed and eroded hardgrounds display replacive 10–30 μm dolomite crystals with cathodoluminescence characteristics consistent with early diagenetic manganese and iron reduction. Regionally, carbon isotope values consistently decrease by around 2‰ from around −3‰ over 30 m of section which is both a temporal and a bathymetric signal, but not a global one. An exponential decline in carbonate production predicted by box models is fitted by a semi‐quantitative sedimentation model. A mass‐anomalous 17O depletion in carbonate‐associated sulphate in dolomite, inherited from precursor calcite, decreases from −0.6 to −0.3‰ in the basal 15 m of section and then approaches background values. The post‐glacial anomalous 17O depletion in carbonate‐associated sulphate and barite elsewhere has been interpreted in terms of ultra‐high pCO2 at the onset of deglaciation. Such anomalies, with larger amplitude, have been reported in Svalbard from underlying lacustrine and tufaceous limestones representing a hyperarid glacial environment. The anomalous sulphate could be produced contemporarily, or the internally drained landscape may have continued to release 17O‐anomalous sulphate as it was transgressed during cap carbonate deposition. The late Cryogenian to earliest Ediacaran record in Svalbard provides the most complete record of the basal 17O‐depletion event in the world.

Oxide-based materials are of key technological importance in different areas including advanced functional materials, solid state chemistry and catalysis. Many of the key questions concerning these areas involve understanding the chemical bond between the metal and the oxygen ions in the first or subsequent coordinating shells. The spectroscopic study of oxygen is therefore of fundamental importance to elucidate the complex interfacial coordination chemistry that underlies the development of metal-oxide supported catalysts and other advanced materials. Oxygen atoms at solid surfaces or lining the pores of zeolite frameworks play a vital role in stabilizing and defining the electronic and geometric structure of single metal atoms or clusters that act as catalytically active sites. In the case of paramagnetic species, EPR and its related hyperfine techniques offer a unique opportunity to explore and understand the nature of the chemical bonding in metal-oxide systems through the detection of the 17O hyperfine interaction. In this perspective we offer an overview of experimental considerations and relevant examples specific to 17O hyperfine spectroscopy of transition metal ions in zeolites relevant to catalysis. 17O hyperfine coupling values are obtained, which allow discriminating σ- and π-bonding channels in metal-oxygen bonds involving first-row transition metal ions. An exhaustive collection of 17O hyperfine and nuclear quadrupole couplings in different systems including molecular and biomolecular chemistry is provided, emphasizing the connection between interfacial and molecular inorganic coordination chemistry.

Two cap carbonates overlying Cryogenian panglacial deposits are found in North‐East Svalbard of which the younger (635 Ma) forms the base of the Ediacaran Period. It is represented by a transgressive succession in which laminated dolostone, typically around 20 m thick (Member D1), is succeeded transitionally by a similar thickness of impure carbonates (Member D2). In Spitsbergen, there is evidence of microbially influenced sediment stabilisation and carbonate precipitation in the lower part of D1, whilst the upper part of D1 and D2 show centimetre‐decimetre‐scale graded units with undulatory lamination interpreted as evidence of storm activity. Carbonate originated as possible freshwater whitings, as well as microbial precipitates. Exhumed and eroded hardgrounds display replacive 10–30 μm dolomite crystals with cathodoluminescence characteristics consistent with early diagenetic manganese and iron reduction. Regionally, carbon isotope values consistently decrease by around 2‰ from around −3‰ over 30 m of section which is both a temporal and a bathymetric signal, but not a global one. An exponential decline in carbonate production predicted by box models is fitted by a semi‐quantitative sedimentation model. A mass‐anomalous 17O depletion in carbonate‐associated sulphate in dolomite, inherited from precursor calcite, decreases from −0.6 to −0.3‰ in the basal 15 m of section and then approaches background values. The post‐glacial anomalous 17O depletion in carbonate‐associated sulphate and barite elsewhere has been interpreted in terms of ultra‐high pCO2 at the onset of deglaciation. Such anomalies, with larger amplitude, have been reported in Svalbard from underlying lacustrine and tufaceous limestones representing a hyperarid glacial environment. The anomalous sulphate could be produced contemporarily, or the internally drained landscape may have continued to release 17O‐anomalous sulphate as it was transgressed during cap carbonate deposition. The late Cryogenian to earliest Ediacaran record in Svalbard provides the most complete record of the basal 17O‐depletion event in the world. [ABSTRACT FROM AUTHOR]

The hydration structure of nitroxide radicals in aqueous solutions is elucidated by advanced 17O hyperfine (hf) spectroscopy with support of quantum chemical calculations and MD simulations. A piperidine and a pyrrolidine‐based nitroxide radical are compared and show clear differences in the preferred directionality of H‐bond formation. We demonstrate that these scenarios are best represented in 17O hf spectra, where in‐plane coordination over σ ${\sigma }$ ‐type H‐bonding leads to little spin density transfer on the water oxygen and small hf couplings, whereas π ${{\rm \pi }}$ ‐type perpendicular coordination generates much larger hf couplings. Quantitative analysis of the spectra based on MD simulations and DFT predicted hf parameters is consistent with a distribution of close solvating water molecules, in which directionality is influenced by subtle steric effects of the ring and the methyl group substituents. [ABSTRACT FROM AUTHOR]

The hydration structure of nitroxide radicals in aqueous solutions is elucidated by advanced 17O hyperfine (hf) spectroscopy with support of quantum chemical calculations and MD simulations. A piperidine and a pyrrolidine‐based nitroxide radical are compared and show clear differences in the preferred directionality of H‐bond formation. We demonstrate that these scenarios are best represented in 17O hf spectra, where in‐plane coordination over σ ${\sigma }$ ‐type H‐bonding leads to little spin density transfer on the water oxygen and small hf couplings, whereas π ${{\rm \pi }}$ ‐type perpendicular coordination generates much larger hf couplings. Quantitative analysis of the spectra based on MD simulations and DFT predicted hf parameters is consistent with a distribution of close solvating water molecules, in which directionality is influenced by subtle steric effects of the ring and the methyl group substituents. [ABSTRACT FROM AUTHOR]

Many applications of oxide nanomaterials depend on their surface structure and properties. Solid-state nuclear magnetic resonance (NMR) spectroscopy has been used to obtain such key information in related studies. This paper summarizes two recently developed approaches based on solid-state NMR spectroscopy for determining the surface structure and properties of oxide nanomaterials, including surface-selective isotopic labeling 17O NMR and dynamic nuclear polarization surface enhanced NMR spectroscopy. The development trend for investigating oxide nanomaterials with solid-state NMR spectroscopy is also introduced.

The aim of this study was to evaluate the feasibility of kinetic analysis of cerebrospinal fluid (CSF) using 17O-labeled water tracer. Four subjects (two idiopathic normal pressure hydrocephalus (iNPH) and two possible AD dementia patients) were prospectively included. Injectable formulation of 17O-labeled water containing 10 mol% of H 2 17O (PSO17), was intrathecally administered to the subjects with the lateral decubitus position between the 3rd and 4th lumbar vertebrae. MRI acquisitions were performed in four-time points, before PSO17 administration, 1, 8, and 24 h after PSO17 administration. The 3-dimensional fast spin echo sequence was used. After image registration for all four-time points data, polygonal regions of interest (ROIs) were set in the 14 regions to obtain the signal intensity of CSF. Each signal intensity within the ROI was converted to 17O concentration [%]. The peak concentration at one hour after administration, the slope of concentration changes after PSO17 administration [%/s], and the root mean square error (RMSE) for evaluating the performance of a fitting were calculated. There was no significant difference in peak concentration between the iNPH and AD group. The slope in the AD group (−2.25 ± 1.62 × 10−3 [%/h]) was significantly smaller than in the iNPH group (−1.21 ± 2.31 × 10−3 [%/h]), which suggests the speed of CSF clearance in the iNPH group was slower than AD group. The RMSE indicating the fit to the concentration change in the AD group (4.86 ± 4.74 × 10−3) was also significantly smaller than in the iNPH group (8.64 ± 7.56 × 10−3). The kinetic evaluation of CSF using 17O-labeled water was feasible, and this preliminary study suggests that the differentiation of iNPH and possible AD dementia can be achieved using this method. [ABSTRACT FROM AUTHOR]

With Ni/CeO2 as an example, which has important applications in catalysis, 17O solid-state nuclear magnetic resonance (NMR) spectroscopy was applied to explore and analyze the concentration of surface Ni ions, according to the changes in the 17O NMR intensity of surface oxygen ions. The results indicate that the Ni concentrations in the first and second top metal ion layers in 10% NiCe-500 and 20% NiCe-300 are within the ranges of 9%~17% and 8%~15%, respectively. This approach may be extended to study the concentration of the doped paramagnetic elements in the surface for a variety of doped oxide materials.

MIL‐53(Al) is a member of the most extensively studied metal–organic framework (MOF) families owing to its "flexible" framework and superior stability. 17O solid‐state NMR (SSNMR) spectroscopy is an ideal site‐specific characterization tool as it probes local oxygen environments. Because oxygen local structure is often altered during phase change, 17O SSNMR can be used to follow phase transitions. However, 17O is a challenging nucleus to study via SSNMR due to its low sensitivity and resolution arising from the very low natural abundance of 17O isotope and its quadrupolar nature. In this work, we describe that by using 17O isotopic enrichment and performing 17O SSNMR experiments at an ultrahigh magnetic field of 35.2 T, all chemically and crystallographically inequivalent oxygen sites in two representative MIL‐53(Al) (as‐made and water adsorbed) phases can be completely resolved. The number of signals in each phase is consistent with that predicted from the space group refined from powder X‐ray diffraction data. The 17O 1D magic‐angle spinning (MAS) and 2D triple‐quantum MAS (3QMAS) spectra at 35.2 T furnish fine information about the host–guest interactions and the structural changes associated with phase transition. The ability to completely resolve multiple chemically and crystallographically inequivalent oxygen sites in MOFs at very high magnetic field, as illustrated in this work, significantly enhances the potential for using the NMR crystallography approach to determine crystal structures of new MOFs and verify the structures of existing MOFs obtained from refining powder X‐ray diffraction data. [ABSTRACT FROM AUTHOR]

In recent years, there has been increasing interest in developing cost‐efficient, fast, and user‐friendly 17O enrichment protocols to help to understand the structure and reactivity of materials by using 17O NMR spectroscopy. Here, we show for the first time how ball milling (BM) can be used to selectively and efficiently enrich the surface of fumed silica, which is widely used at industrial scale. Short milling times (up to 15 min) allowed modulation of the enrichment level (up to ca. 5 %) without significantly changing the nature of the material. High‐precision 17O compositions were measured at different milling times by using large‐geometry secondary‐ion mass spectrometry (LG‐SIMS). High‐resolution 17O NMR analyses (including at 35.2 T) allowed clear identification of the signals from siloxane (Si−O−Si) and silanols (Si−OH), while DNP analyses, performed by using direct 17O polarization and indirect 17O{1H} CP excitation, agreed with selective labeling of the surface. Information on the distribution of Si−OH environments at the surface was obtained from 2D 1H−17O D‐HMQC correlations. Finally, the surface‐labeled silica was reacted with titania and using 17O DNP, their common interface was probed and Si−O−Ti bonds identified. [ABSTRACT FROM AUTHOR]

The δD and δ18O values of water are key measurements in polar ice-core research, owing to their strong and well-understood relationship with local temperature. Deuterium excess, d, the deviation from the average linear relationship between δD and δ18O, is also commonly used to provide information about the oceanic moisture sources where polar precipitation originates. Measurements of δ17O and “17O excess” (Δ17O) are also of interest because of their potential to provide information complementary to d. Such measurements are challenging because of the greater precision required, particularly for Δ17O. Here, high-precision measurements are reported for δ17O, δ18O, and δD on a new ice core from the South Pole, using a continuous-flow measurement system coupled to two cavity ring-down laser spectroscopy instruments. Replicate measurements show that at 0.5 cm resolution, external precision is ∼0.2‰ for δ17O and δ18O, and ∼1‰ for δD. For Δ17O, achieving external precision of

Interactions of γ‐alumina with water are important in controlling its structure and catalytic properties. We apply solid‐state multinuclear NMR spectroscopy to investigate these interactions by monitoring 1H and 17O spectra in real‐time. Surface‐selective detection is made possible by adsorbing 17O‐enriched water on γ‐alumina nanorods. Structural evolution on the surface was selectively probed by 1H/17O double resonance NMR and 27Al NMR at ultrahigh 35.2 T magnetic field. Formation of hydroxyl species on the surface of nanorods is rapid upon the exposure of water, which involves low coordinated aluminum ions with doubly bridging and isolated hydroxyl species being generated first. Fast exchange occurs between oxygen atoms in the water molecules and bare surface sites, indicating high reactivity of these oxygen species. These results provide new insights into the structure and dynamics on the surface of γ‐alumina and the methods applied here can be extended to study the interaction of other oxides with water. [ABSTRACT FROM AUTHOR]

The Zr-based Metal Organic Framework (MOF) UiO-66(Zr) is widely employed owing to its good thermal and chemical stabilities. Although the long-range structure of this MOF is preserved in the presence of water during several days, little is known about the formation of defects, which cannot be detected using diffraction techniques. We apply here 17 O solid-state NMR spectroscopy at 18.8 T to investigate the reactivity of UiO-66, through the exchange of oxygen atoms between the different sites of the MOF and water. For that purpose, we have selectively enriched in 17 O isotope the carboxylate groups of UiO-66(Zr) by using it with 17 O-labeled terephthalic acid prepared using mechanochemistry. In the presence of water at 50 °C and a following dehydration at 150 °C, we observe an overall exchange of O atoms between COO - and μ 3 -O 2- sites. Furthermore, we demonstrate that the three distinct oxygen sites, μ 3 -OH, μ 3 -O 2- and COO - , of UiO-66(Zr) MOF can be enriched in 17 O isotope by post-synthetic hydrothermal treatment in the presence of 17 O-enriched water. These results demonstrate the lability of Zr-O bonds and the reactivity of UiO-66(Zr) with water., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Abstract Deposition of atmospheric nitrate (NO 3 −) in precipitation can be an important source of reactive nitrogen (N) to ecosystems, particularly in regions with high nitrogen oxide (NO x = nitric oxide (NO)+nitrogen dioxide (NO 2)) emissions. However, high resolution deposition data are lacking for most systems. We conducted hourly precipitation sampling across six growing season storms in a forested area historically subjected to some of the highest levels of chronic N deposition in the United States. To characterize the influence of electricity generating unit (EGU), vehicle, and biogenic NO x emissions on NO 3 − deposition, we calculated the total NO x emitted from these sources within a 100 km radius of air mass back trajectories determined for Fernow Experimental Forest (West Virginia, USA). We combined these emissions estimates with established 15N isotope values for NO x sources in a three end-member mixing model to predict source-based δ15N values of deposition reaching the study site on an hourly basis. To evaluate the effect of NO x oxidation pathways on measured δ15N-NO 3 - values, we compared observed hourly isotope values to a coupled δ15N and Δ17O array representing N isotope exchange between atmospheric oxidized N molecules. Within individual events, δ15N, δ18O, and Δ17O values ranged by as much as 19.5‰, 28.9‰, and 13.8‰, respectively. This extreme short-term isotopic variability suggests a dynamic mix of NO x sources, oxidation pathways, and fractionation processes contributing to HNO 3 formation. During every storm, precipitation δ15N-NO 3 - values were lower than those expected to result from predominant HNO 3 formation pathways or oxidation of estimated NO x emissions along back trajectories, suggesting a systematic underestimation of NO x contributions to atmospheric HNO 3 formation from isotopically depleted soil emissions. Together, these analyses represent the most comprehensive assessment to date relating high temporal resolution δ15N-NO 3 - observations to NO x emission sources, oxidation chemistry, and isotopic fractionation effects. We present the first observations of extreme intra-storm δ15N, δ18O, and Δ17O variability, emphasizing the need for improved constraints on soil NO x emissions, forest canopy effects, and their role in atmospheric NO 3 − deposition and isotope dynamics in forests. Highlights • Triple NO 3 − isotopes in wet deposition demonstrate extreme intra-storm variability. • Anthropogenic and biogenic NO x sources contribute to precipitation NO 3 − formation. • Intra-system N recycling may be an important source of wet NO 3 − deposition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gd3+ incorporation in In(OH) 3 demonstrated by EPR and 1H PRE. • 1H DNP enhancement of 9 for Gd-doped In(OH) 3. • DNP-enhanced natural abundance 17O NMR spectrum using PRESTO-II. • Breaking of symmetry by proton disorder explored with quadrupolar 115In NMR. Dynamic nuclear polarisation (DNP) of solids doped with high-spin metal ions, such as Gd3+, is a useful strategy to enhance the nuclear magnetic resonance (NMR) sensitivity for these samples. Spin diffusion can relay polarisation throughout a sample, which is most effective for dense 1H networks, while the efficiency of DNP using Gd3+ depends on the symmetry of the metal site. Here, we investigate cubic In(OH) 3 as a high-symmetry, proton-containing material for endogenous Gd DNP. A 1H enhancement of up to 9 is demonstrated and harnessed to measure the 17O spectrum at natural abundance. The enhancement is interpreted in terms of clustering of the Gd3+ dopants and the local reduction in symmetry of the metal site induced by proton disorder, as demonstrated by quadrupolar 115In NMR. This is the first example of 1H DNP using Gd3+ dopants in an inorganic solid. [ABSTRACT FROM AUTHOR]

δ 17 O and Δ' 17 O are emerging tracers increasingly used in isotope hydrology, climatology, and biochemistry. Differentiating small relative abundance changes in the rare 17 O isotope from the strong covariance with 18 O imposes ultra-high precision requirements for this isotope analysis. Measurements of δ 17 O by Cavity Ringdown Spectroscopy (CRDS) are attractive due to the ease of sample preparation, automated throughput, and avoidance of chemical conversions needed for isotope-ratio mass spectrometry. However, the CRDS approach requires trade-offs in measurement precision and uncertainty. In this protocol document, we present the following:•New analytical procedures and a software tool for conducting δ 17 O and Δ' 17 O measurements by CRDS.•Outline a robust uncertainty framework for Δ' 17 O determinations.•Description of a CRDS performance framework for optimizing throughput, instrumental stability, and Δ' 17 O measurement precision and accuracy., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 International Atomic Energy Agency. Published by Elsevier B.V.)

The hydration structure of nitroxide radicals in aqueous solutions is elucidated by advanced 17 O hyperfine (hf) spectroscopy with support of quantum chemical calculations and MD simulations. A piperidine and a pyrrolidine-based nitroxide radical are compared and show clear differences in the preferred directionality of H-bond formation. We demonstrate that these scenarios are best represented in 17 O hf spectra, where in-plane coordination over σ ${\sigma }$ -type H-bonding leads to little spin density transfer on the water oxygen and small hf couplings, whereas π ${{\rm \pi }}$ -type perpendicular coordination generates much larger hf couplings. Quantitative analysis of the spectra based on MD simulations and DFT predicted hf parameters is consistent with a distribution of close solvating water molecules, in which directionality is influenced by subtle steric effects of the ring and the methyl group substituents., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The resonance-assisted hydrogen bond (HB) phenomenon has been studied theoretically by a localized molecular orbital (LMO) decomposition of the spin-spin coupling constants between atoms either involved or close to the O-H · · · O system of some β-diketones and their saturated counterparts. The analysis, carried out at the level of the second-order polarization propagator approximation, shows that the contributions in terms of LMO to the paramagnetic spin orbital and the spin dipolar Ramsey terms proof the importance of the delocalized π-electron structure supporting the idea of the existence of the resonance-assisted HB phenomenon phenomenon. The LMO contributions to the Fermi contact term indicate mainly the presence of the HB that may or not be linked to the π-electrons. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To resolve discrepant results between O1s XPS and 29Si and 17O NMR techniques, O1s XPS spectra were collected and fitted for 15 potassium silicate glasses containing 10−37 mol% K2O. The effects of melting on the compositions of the glasses are documented and quantified, as are uncertainties associated with fitting the O1s spectra. These spectra are well resolved into two symmetric peaks: a narrow peak due to NBO (Si− O−K) plus 'free oxide' (O2- or K− O−K) and a broader peak due to BO (Si− O−Si). Values of mol% BO (uncertainties of ±1%) are obtained from the computed peak areas and indicate 2.2 (±0.8) mol% O2- for glasses containing 32 (±1) mol% K2O. Reassignment of Q species for previously published 29Si NMR spectra leads to BO and O2- values in good agreement with these O1s XPS spectra. A recent 17O NMR study on potassium silicate glasses concluded that there is <1 mol% O2- in these glasses based mainly on the assumption that the 17O chemical shift for O2- should be similar in the glasses and the oxide in crystalline K2O. This assumption is questionable. Free oxide in these glasses should be highly reactive toward gases such as CO2 (via CO2 + O2- → CO32-) and it seems likely that the reactive species in silicate glasses is O2- rather than NBO as often assumed. The small amounts of CO2 found in reacted glasses are qualitatively consistent with the abundance of O2- obtained from these O1s XPS spectra of silicate glass. [ABSTRACT FROM AUTHOR]

BACKGROUND: Development of molecular MR imaging (MRI) similar to PET imaging using contrast agents such as gadolinium as probe have been inherently hampered by incompatibility between potential probe (charged molecules) and membrane permeability. Nevertheless, considering the inherent spatial resolution limit for PET of 700µ, the superior microscopic resolution of MRI of 4 µ presents a strong incentive for research into ligand-based molecular MRI. METHODS: 17O exhibits JJ vicinal coupling with a covalently bound proton in a hydroxyl group. This 17O coupled proton can be ionized in water solution and interexchange with other water protons. This property can be utilized as "probe" in T2-weighted imaging and developed into ligand-based molecular MRI. We examined β-amyloid distribution in human APP overexpressed transgenic mice in vivo following injection of 17O labeled Pittsburg compound B (17O-PiB). RESULTS: JJVCPE imaging successfully imaged 17O-PiB, unequivocally establishing that 17O JJVCPE imaging can be developed into PET-like molecular MRI in clinical medicine. CONCLUSIONS: The study represents the first successful ligand-based molecular MRI in vivo. This is also the first in vivo amyloid imaging using MRI. High-resolution molecular MRI with high specificity under clinical settings, such as in vivo microscopic imaging of senile plaque, is a foreseeable aim. [ABSTRACT FROM AUTHOR]

This review is a critical survey of the literature that aims to highlight the most significant developments on synthetic strategies involving stable oxygen isotopes ([17O] and [18O]). The labeling methodologies are categorized in groups, according to the oxygen-containing functional group. [ABSTRACT FROM AUTHOR]

Abstract: The growing number of recent high precision triple oxygen isotope data of water and atmospheric gases requires the reinvestigation of the major isotope fractionation processes between the hydro-, bio- and atmosphere. Here we present the experimental triple oxygen isotope fractionation factor between CO2 gas and water in the temperature range between 2 and 37°C. We have determined the triple oxygen isotope fractionation factor, θ=ln17α/ln18α, for CO2–water equilibrium and found that θCO2–water =0.522±0.002 (t0.95 ×SEM). No temperature dependence was resolved. Knowledge on the triple oxygen isotope equilibrium fractionation between CO2 and water is crucial for estimating the triple oxygen isotope composition of tropospheric CO2. Model predictions combined with high-precision Δ17O analysis of tropospheric CO2 might reveal new information on biosphere–atmosphere interactions or the influx of anomalous stratospheric CO2. [Copyright &y& Elsevier]

A combination of solid-state nuclear magnetic resonance (NMR) and first principles calculations was applied to obtain 17O, 25Mg, and 33S NMR parameters for two polymorphs of anhydrous magnesium sulfate. Working at the very high magnetic field of 21.14 T results in a dramatic improvement of resolution through a reduction of the effects of quadrupolar interactions and significant improvement in sensitivity. Experimental 25Mg and 33S spectra are dominated by quadrupolar interactions with quadrupolar parameters unique for each polymorph. In the case of 17O, there is a substantial contribution of the chemical shift anisotropy. The use of multiple-quantum magic-angle spinning (MQMAS) experiments allows the resolution of distinct oxygen species and assignment of signals in the experimental 17O spectrum. Chemical shielding constants and quadrupolar parameters for all three nuclei were calculated using plane wave pseudopotential density functional theory as implemented in the CASTEP computational package. The calculated NMR parameters are in very good agreement with the experimental results and help in signal assignment of the 17O spectrum. The results suggest applicability of such a combined computational and experimental solid-state NMR approach for the refinement of crystallographic data. [ABSTRACT FROM AUTHOR]

Abstract: The oxygen vacancies distribution in the rigid lattice and the thermally activated motion of oxygen atoms are studied in La1−x Sr x Ga1−x Mg x O3−x (x=0.00; 0.05; 0.10; 0.15 and 0.20) compounds. For that 71Ga, 25Mg and 17O NMR was performed from 100K up to 670K, and ion conductivity measurements were carried out up to 1273K. The comparison of the electric field gradients at the Ga- and Mg-sites evidences that oxygen vacancies appear exclusively near gallium cations as a species trapped below room temperature in local clusters, GaO5/2-□-GaO5/2. These clusters decay at higher temperature into mobile constituents of the structural octahedra Ga(O5/6□1/6)6/2. At the same time, the nearest octahedral oxygen environment of magnesium cations persists at different doping levels. The case of two adjacent vacant anion sites is found highly unlikely within the studied doping range. The thermally activated oxygen motion starts to develop above room temperature as is observed from both the motional narrowing of 17O NMR spectra and the 17O nuclear spin-lattice relaxation rate. The obtained results show that two types of motion exist, a slow motion and a fast one. The former is a long-range diffusion whereas the latter is a local back and forth oxygen jumps between two adjacent anion sites. These sites are strongly differentiated by the probability of the vacancy formation, like the vacant apical site and the occupied equatorial site in the orthorhombic compositions x <0.15. [ABSTRACT FROM AUTHOR]

Abstract: The orange-colored and hydrolytically stable compound {[Ti2O(bhmpc)(Hbhmpc)(H2bhmpc)].C4H8O2.HX}2 (with H3bhmpc = 2,6-bis(hydroxymethyl)-p-cresol and X = OEt or CCl3) has been studied by a combination of single crystal X-ray diffraction data, U.V.-vis. spectroscopy, IR and Raman spectroscopies, 1H, 13C and 17O solution NMR spectroscopies, electron density and statistical thermodynamics modeling. We observed that the molecular structure found in the solid state is conserved in solution. Based on X-ray diffraction data, we also propose a complete and non-ambiguous assignment for the fully resolved 1H and 13C solution NMR spectra through the use of 2D-techniques (COSY, ROESY, HSQC, HMBC) and 1H relaxation time measurements. The ability of the partial charge model introduced more than 20 years ago by J. Livage''s group to reproduce observed 13C NMR chemical shifts in solution is demonstrated. Statistical thermodynamic modeling between Ti(OR)4 (monomers, trimers or tetramers) has shown that complexation was in all cases under entropy control. Possible applications of this soluble and stable precursor to the sol–gel processing of hybrid organic–inorganic are addressed. [Copyright &y& Elsevier]

We present mobile, low-field 17O NMR as a means for monitoring oxygen in liquids. Whereas oxygen is one of the most important elements, oxygen NMR is limited by a poor sensitivity related to low natural abundance and gyro-magnetic ratio of the NMR active 17O isotope. Here, we demonstrate 17O NMR detection at a Larmor frequency of 8.74 MHz in a 1.5-T Halbach neodymium magnet with a home-built digital NMR instrument suitable for large-scale production and in-line monitoring applications. The proposed 17O NMR sensor may be applied for direct, noninvasive measurements of water content in, for example, oil, manure, or food in automated quality or process control. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: High-resolution 17O multiple-quantum MAS (MQMAS) NMR spectra have been obtained for zeolite HY in order to study its local structure and Brønsted acidity. The 17O NMR signals due to all the different oxygen environments have been observed in one single experiment, including the readily-resolved signals arising from the two types of oxygen atoms of the zeolite framework (Si–O–Al and Si–O–Si), and oxygen atoms directly bound to Brønsted acid sites (Si–O(H)–Al). The 17O NMR parameters such as the isotropic chemical shift (δ CS) and quadrupolar coupling parameters (quadrupolar coupling constant, QCC and asymmetry parameter, η) for these oxygen species have been extracted and found to be consistent with the results from previous NMR measurements. The NMR parameters of the framework sites reveal a greater distribution of T–O–T′ bond angles over those typically observed in hydrated zeolites. [Copyright &y& Elsevier]

Abstract: Controlled-pore glasses (CPGs) are silica-based materials which provide an adequate model system for a better understanding of the radiation chemistry of glasses, especially under nanoscopic confinement. This paper presents a characterization of a nanoporous CPG before and after electron irradiation using multinuclear solid-state magnetic resonance (NMR). 1H MAS NMR has been used for studying the surface proton sites and it is observed that the irradiation leads to a dehydration of the material. Accordingly, concerning the silicon sites near the surface, the observed variation of the Q4, Q3 and Q2 species from 1H–29Si CPMAS spectra shows an increase of the surface polymerization under irradiation, implying in majority a Q2 to Q3/Q4 conversion mechanism. Similarly, 1H–17O CPMAS measurements exhibit an increase of Si–O–Si groups at the expenses of Si–OH groups. In addition, modifications of the environment of the residual boron atoms are also put in evidence from 11B MAS and MQMAS NMR These data show that MAS NMR methods provide sensitive tools for the characterization of these porous glasses and of the tiny modifications occurring under electron irradiation. [Copyright &y& Elsevier]

Abstract: A density functional theory study has been carried out to calculate the 17O, 15N, 13C, and 1H chemical shielding as well as 17O, 14N, and 2H electric field gradient tensors of chitosan/HI type I salt. These calculations were performed using the B3LYP functional and 6-311++G (d,p) and 6-31++G (d,p) basis sets. Calculated EFG and chemical shielding tensors were used to evaluate the 17O, 14N, and 2H nuclear quadruple resonance, NQR, and 17O, 15N, 13C, and 1H nuclear magnetic resonance, NMR, parameters in the cluster model, which are in good agreement with the available experimental data. The difference in the isotropic shielding (σ iso) and quadrupole coupling constant (C Q) between monomer and target molecule in the cluster was analyzed in detail. It was shown that both EFG and CS tensors are sensitive to hydrogen-bonding interactions, and calculating both tensors is an advantage. A different influence of various hydrogen bond types, N–H⋯I, O–H⋯I, and N–H⋯O was observed on the calculated CS and EFG tensors. On the basis of this study, nitrogen and O-6 are the most important nuclei to confirm crystalline structure of chitosan/HI. These nuclei have large change in their CS and EFG tensors because of forming intermolecular hydrogen bonds. Moreover, the quantum chemical calculations indicated that the intermolecular hydrogen-bonding interactions play an essential role in determining the relative orientation of CS and EFG tensors of O-6 and nitrogen atoms in the molecular frame axes. [Copyright &y& Elsevier]

Abstract: Compounds enriched in the rare isotopes of light elements, such as 18O, 17O, 13C or 15N, are used in a very large variety of isotopic tracing studies including investigating the microscopic mechanisms of the movements of atoms in solids. Owing to their very high cost or limited availability these products must be handled in gram amounts or less. Handling such compounds in small quantities in the liquid or gaseous state, purifying and recovering them for further use require special techniques that are described in detail in this paper. Dedicated vacuum lines are used for labelled water, special high vacuum furnace installations are required for thermal treatments with labelled gases that must be used under static conditions while remaining pure. Ion beam analysis is systematically used to investigate the wide spectrum of applications of isotopic tracing in electrochemistry and in applied physics. A number of typical experiments are outlined briefly providing examples for future experimental development in this field. [Copyright &y& Elsevier]

The results of structural investigations of vanadium, molybdenum, and tungsten polyoxoanions (PA) by 17O, 51V, 95Mo, 183W, and heteroatom NMR are generalized in this review. NMR spectroscopy possibilities to determine the structure of PA are discussed. NMR data on PA of different structures compositions nuclei are demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: For the first time, 17O NMR studies were performed on 17O-enriched crystalline pyrophosphates (magnesium-, sodium- and barium-pyrophosphate) by means of triple-quantum magic-angle spinning (3QMAS) and double-rotation (DOR) in the high external field of 17.6T. Oxygen atoms in bridging positions (P–OB–P) exhibit a significant higher quadrupole coupling constant compared to oxygen atoms in terminal positions (P–OT). With increasing cationic radius a higher value of the chemical shift of the terminal oxygen atoms is observed. [Copyright &y& Elsevier]

We report the 17O, 207Pb NMR and 17O–207Pb SEDOR study of superconducting BaPb1- x Bi x O3 ( x 0.35) oxides. Inhomogeneous The results points to the formation of microscopically inhomogeneous distribution of the carrier density in metallic phase. The local spin susceptibility is increased around Bi cation within an area, which is delimited by its two first cation shells. [ABSTRACT FROM AUTHOR]

Abstract: In a series of sodium aluminoborate glasses, we have applied triple-quantum magic-angle spinning (3QMAS) 17O NMR to obtain high-resolution information about the connections among various network structural units, to explore the mixing of aluminum and boron species. Oxygen-17 3QMAS spectra reveal changes in connectivites between AlO4 ([4]Al), AlO5 and AlO6 ([5,6]Al), BO3 ([3]B) and BO4 ([4]B) units, by quantifying populations of bridging oxygens such as Al–O–Al, Al–O–B and B–O–B and of non-bridging oxygens. Several linkages such as [4]Al–O–[4]Al and three-coordinated oxygen associated with [5,6]Al in Al–O–Al, [4]Al–O–[4]B, [4]Al–O–[3]B and [5,6]Al–O–[3]B in Al–O–B as well as [4]B–O–[3]B and [3]B–O–[3]B in B–O–B can be distinguished for the first time. The fractions of these linkages were calculated from models of random mixing and of mixing with maximum avoidance of tetrahedral–tetrahedral linkages. The results suggest that the structure of all of glasses in this study is well approximated by the latter model. However, the energetic “penalty” for formation of [4]Al–O–[4]B may be somewhat less than for [4]Al–O–[4]Al and [4]B–O–[4]B. In general, the new results presented here are similar to those obtained on glasses in this system by 27Al{11B} REDOR NMR (J. Phys. Chem. B 104 (2000) 6541), but provide considerably more detail on network connectivity and ordering schemes. [Copyright &y& Elsevier]

Ab initio molecular orbital calculations (Hartree–Fock, HF and density functional theory, DFT) of the 17O NMR electrical field gradient (EFG) parameters for the bridging oxygen (OB) in the model cluster H4P2O7 are presented. The variation of the quadrupolar coupling constant (CQ) and asymmetry parameter (ηQ) for the EFG of the bridging oxygen was shown to be a function of both the bridging P–OB–P bond angle and the O?P–OB–P?O conformation. These ab initio calculations allowed empirical relationships between the 17O NMR EFG parameters and the P–OB–P bond angle to be tabulated for a wide range of O?P–OB–P?O conformations. For experimentally realistic ranges of the P–OB–P bond angle, the 17O NMR EFG parameters are dominated by variations in the P–OB–P bond angle, with minor changes due to the O?P–OB–P?O conformation. These calculations also demonstrated systematic differences in the predicted 17O EFG parameters obtained using HF and DFT level of theory. [Copyright &y& Elsevier]

The effects of different heat treatment schemes (i.e. successively or directly heated to particular temperatures) and atmospheres (air or nitrogen) on the solid-state NMR spectra obtained from (TiO2)0.15(ZrO2)0.05(SiO2)0.80 sol–gel materials are investigated. A combination of 1H, 13C, 17O and 29Si NMR is used. 29Si MAS NMR indicates that the extent of condensation of the silica-based network strongly depends on the maximum temperature the sample has experienced, but the condensation is largely independent of the details of the heat treatment scheme and atmosphere used. For sol–gel produced silicate-based materials the results show that the equilibrium structure at each temperature is reached rapidly compared to the time (2 h) spent at that temperature. The 17O NMR results confirm that a nitrogen atmosphere does significantly reduce loss of 17O from the structure but care must be taken since there could be differential loss of 17O from the regions having different local structural characteristics. [Copyright &y& Elsevier]