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15 pages, 4234 KiB

Open AccessArticle

The Synthesis and Spectroscopic Characterization of Structural Changes in Hydrophobic Silica Aerogels upon Encapsulation of the LCC ICCG Enzyme

by Tatiana Alpízar-Rojas, Juan Diego Barboza-Carmona, Erik Butenschön, Guzel Musabirova, Erick Castellón, Jörg Matysik and Isaac F. Céspedes-Camacho

Gels 2025, 11(2), 92; https://doi.org/10.3390/gels11020092 - 25 Jan 2025

Cited by 1 | Viewed by 1891

Abstract

Silica aerogels are highly porous materials known for their low density and extensive surface area, making them ideal for applications in thermal insulation, catalysis, and environmental remediation. This study investigates the structural changes of functionalized hydrophobic silica aerogels used as carriers of the [...] Read more.

Silica aerogels are highly porous materials known for their low density and extensive surface area, making them ideal for applications in thermal insulation, catalysis, and environmental remediation. This study investigates the structural changes of functionalized hydrophobic silica aerogels used as carriers of the LCC ICCG enzyme. The aerogels were synthesized using the sol-gel method, with trimethylethoxysilane (TMES) as a functionalizing agent to enhance hydrophobicity. The enzyme-encapsulated aerogels were characterized using hyperpolarized ¹²⁹Xe NMR, ²⁹Si NMR, nitrogen sorption analysis, TEM, contact angle measurements, and FT-IR spectroscopy to evaluate their structural and chemical properties. The results confirmed successful encapsulation of the enzyme, as indicated by changes in the pore structure and network morphology. These findings demonstrate that functionalized silica aerogels can effectively support LCC ICCG immobilization, offering a promising approach for plastic degradation applications. Full article

(This article belongs to the Special Issue Synthesis and Application of Aerogel)

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13 pages, 4538 KiB

Open AccessArticle

Measuring Transverse Relaxation with a Single-Beam 894 nm VCSEL for Cs-Xe NMR Gyroscope Miniaturization

by Qingyang Zhao, Ruochen Zhang and Hua Liu

Sensors 2024, 24(17), 5692; https://doi.org/10.3390/s24175692 - 1 Sep 2024

Cited by 3 | Viewed by 1416

Abstract

The spin-exchange-pumped nuclear magnetic resonance gyroscope (NMRG) is a pivotal tool in quantum navigation. The transverse relaxation of atoms critically impacts the NMRG’s performance parameters and is essential for judging normal operation. Conventional methods for measuring transverse relaxation typically use dual beams, which [...] Read more.

The spin-exchange-pumped nuclear magnetic resonance gyroscope (NMRG) is a pivotal tool in quantum navigation. The transverse relaxation of atoms critically impacts the NMRG’s performance parameters and is essential for judging normal operation. Conventional methods for measuring transverse relaxation typically use dual beams, which involves complex optical path and frequency stabilization systems, thereby complicating miniaturization and integration. This paper proposes a method to construct a ¹³³Cs parametric resonance magnetometer using a single-beam vertical-cavity surface-emitting laser (VCSEL) to measure the transverse relaxation of ¹²⁹Xe and ¹³¹Xe. Based on this method, the volume of the gyroscope probe is significantly reduced to 50 cm³. Experimental results demonstrate that the constructed Cs-Xe NMRG can achieve a transverse relaxation time (T₂) of 8.1 s under static conditions. Within the cell temperature range of 70 °C to 110 °C, T₂ decreases with increasing temperature, while the signal amplitude inversely increases. The research lays the foundation for continuous measurement operations of miniaturized NMRGs. Full article

(This article belongs to the Special Issue Atomic Magnetic Sensors)

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13 pages, 911 KiB

Open AccessArticle

Estimation of Radiation Damping Rates Using ¹³³Cs, ⁷Li and ³¹P Solution NMR Spectroscopy and a Theoretical NMR RASER Model

by Eisuke Chikayama, Stephan J. Ginthör, Matthias Bechmann and Norbert Müller

Magnetochemistry 2023, 9(10), 221; https://doi.org/10.3390/magnetochemistry9100221 - 18 Oct 2023

Cited by 1 | Viewed by 1767

Abstract

Radio amplification using stimulated emission of radiation (RASER) effects in the NMR can increase NMR signals over time due to a feedback loop between the sample magnetization and the probe coil coupled with radiation damping (RD). Previously, RD rates had been directly observed [...] Read more.

Radio amplification using stimulated emission of radiation (RASER) effects in the NMR can increase NMR signals over time due to a feedback loop between the sample magnetization and the probe coil coupled with radiation damping (RD). Previously, RD rates had been directly observed only for the ¹H, ³He, ¹⁷O and ¹²⁹Xe nuclei. We report that experimental direct measurements of an NMR RASER to determine RD time constants for the three heteronuclei (¹³³Cs (I = 7/2), ⁷Li (I = 3/2) and ³¹P (I = 1/2)) in a highly concentrated solution from the NMR RASER emissions using a conventional NMR probe. Under conditions where the RD rate exceeds the transverse relaxation rate (i.e., the NMR RASER condition is fulfilled), we recorded both the transverse NMR RASER response to imperfect inversion and the recovery of longitudinal magnetization. The data were directly evaluated based on the well-known Bloom model as estimated RD rate constants of 8.0, 1.8 and 25 Hz for ¹³³Cs, ⁷Li and ³¹P, respectively. The proposed method can be applied to observe RD rate constants for the other nuclei as well. Full article

(This article belongs to the Special Issue Future Prospects for NMR Spectroscopy: A Perspective)

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13 pages, 2612 KiB

Open AccessArticle

Revealing a Third Dissolved-Phase Xenon-129 Resonance in Blood Caused by Hemoglobin Glycation

by Lutosława Mikowska, Vira Grynko, Yurii Shepelytskyi, Iullian C. Ruset, Joseph Deschamps, Hannah Aalto, Marta Targosz-Korecka, Dilip Balamore, Hubert Harańczyk and Mitchell S. Albert

Int. J. Mol. Sci. 2023, 24(14), 11311; https://doi.org/10.3390/ijms241411311 - 11 Jul 2023

Cited by 2 | Viewed by 1742

Abstract

Hyperpolarized (HP) xenon-129 (¹²⁹Xe), when dissolved in blood, has two NMR resonances: one in red blood cells (RBC) and one in plasma. The impact of numerous blood components on these resonances, however, has not yet been investigated. This study evaluates the [...] Read more.

Hyperpolarized (HP) xenon-129 (¹²⁹Xe), when dissolved in blood, has two NMR resonances: one in red blood cells (RBC) and one in plasma. The impact of numerous blood components on these resonances, however, has not yet been investigated. This study evaluates the effects of elevated glucose levels on the chemical shift (CS) and

T_{2}^{*}

relaxation times of HP ¹²⁹Xe dissolved in sterile citrated sheep blood for the first time. HP ¹²⁹Xe was mixed with sheep blood samples premixed with a stock glucose solution using a liquid–gas exchange module. Magnetic resonance spectroscopy was performed on a 3T clinical MRI scanner using a custom-built quadrature dual-tuned ¹²⁹Xe/¹H coil. We observed an additional resonance for the RBCs (¹²⁹Xe-RBC1) for the increased glucose levels. The CS of ¹²⁹Xe-RBC1 and ¹²⁹Xe-plasma peaks did not change with glucose levels, while the CS of ¹²⁹Xe-RBC2 (original RBC resonance) increased linearly at a rate of 0.015 ± 0.002 ppm/mM with glucose level. ¹²⁹Xe-RBC1

T_{2}^{*}

values increased nonlinearly from 1.58 ± 0.24 ms to 2.67 ± 0.40 ms. As a result of the increased glucose levels in blood samples, the novel additional HP ¹²⁹Xe dissolved phase resonance was observed in blood and attributed to the ¹²⁹Xe bound to glycated hemoglobin (HbA_1c). Full article

(This article belongs to the Section Molecular Biophysics)

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16 pages, 2957 KiB

Open AccessArticle

Combined Polarization/Magnetic Modulation of a Transverse NMR Gyroscope

by Susan S. Sorensen and Thad G. Walker

Sensors 2023, 23(10), 4649; https://doi.org/10.3390/s23104649 - 11 May 2023

Cited by 5 | Viewed by 2131

Abstract

In this paper, we describe a new approach to the continuous operation of a transverse spin-exchange optically pumped NMR gyroscope that utilizes modulation of both the applied bias field and the optical pumping. We demonstrate the simultaneous, continuous excitation of

^{131}

Xe and [...] Read more.

In this paper, we describe a new approach to the continuous operation of a transverse spin-exchange optically pumped NMR gyroscope that utilizes modulation of both the applied bias field and the optical pumping. We demonstrate the simultaneous, continuous excitation of

^{131}

Xe and

^{129}

Xe using this hybrid modulation approach and the real-time demodulation of the Xe precession using a custom least-squares fitting algorithm. We present rotation rate measurements with this device, with a common field suppression factor of ∼1400, an angle random walk of 21

μ Hz

/

\sqrt{Hz}

, and a bias instability of ∼480 nHz after ∼1000 s. Full article

(This article belongs to the Special Issue Sensing Technologies for Precision Measurements)

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20 pages, 4152 KiB

Open AccessArticle

Towards Probing Conformational States of Y2 Receptor Using Hyperpolarized ¹²⁹Xe NMR

by Peter Schmidt, Alexander Vogel, Benedikt Schwarze, Florian Seufert, Kai Licha, Virginia Wycisk, Wolfgang Kilian, Peter W. Hildebrand and Lorenz Mitschang

Molecules 2023, 28(3), 1424; https://doi.org/10.3390/molecules28031424 - 2 Feb 2023

Cited by 3 | Viewed by 2179

Abstract

G protein-coupled receptors can adopt many different conformational states, each of them exhibiting different restraints towards downstream signaling pathways. One promising strategy to identify and quantify this conformational landscape is to introduce a cysteine at a receptor site sensitive to different states and [...] Read more.

G protein-coupled receptors can adopt many different conformational states, each of them exhibiting different restraints towards downstream signaling pathways. One promising strategy to identify and quantify this conformational landscape is to introduce a cysteine at a receptor site sensitive to different states and label this cysteine with a probe for detection. Here, the application of NMR of hyperpolarized ¹²⁹Xe for the detection of the conformational states of human neuropeptide Y2 receptor is introduced. The xenon trapping cage molecule cryptophane-A attached to a cysteine in extracellular loop 2 of the receptor facilitates chemical exchange saturation transfer experiments without and in the presence of native ligand neuropeptide Y. High-quality spectra indicative of structural states of the receptor–cage conjugate were obtained. Specifically, five signals could be assigned to the conjugate in the apo form. After the addition of NPY, one additional signal and subtle modifications in the persisting signals could be detected. The correlation of the spectroscopic signals and structural states was achieved with molecular dynamics simulations, suggesting frequent contact between the xenon trapping cage and the receptor surface but a preferred interaction with the bound ligand. Full article

(This article belongs to the Special Issue Molecular Modeling, Synthesis, and Functional Characterization of GPCR (G-Protein Coupled Receptor) Ligands)

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15 pages, 1183 KiB

Open AccessReview

Probing Nuclear Dipole Moments and Magnetic Shielding Constants through 3-Helium NMR Spectroscopy

by Włodzimierz Makulski

Physchem 2022, 2(2), 116-130; https://doi.org/10.3390/physchem2020009 - 28 Apr 2022

Cited by 4 | Viewed by 2958

Abstract

Multinuclear NMR studies of the gaseous mixtures that involve volatile compounds and ³He atoms are featured in this review. The precise analyses of ³He and other nuclei resonance frequencies show linear dependencies on gas density. Extrapolation of the gas phase results [...] Read more.

Multinuclear NMR studies of the gaseous mixtures that involve volatile compounds and ³He atoms are featured in this review. The precise analyses of ³He and other nuclei resonance frequencies show linear dependencies on gas density. Extrapolation of the gas phase results to the zero-pressure limit gives the ν₀(³He) and ν₀(ⁿX) resonance frequencies of nuclei in a single 3-helium atom and nuclei in molecules at a given temperature. The NMR frequency comparison method provides an approach for determining different nuclear magnetic moments. The application of quantum chemical shielding calculations, which include a more complete and careful theoretical treatment, allows the shielding of isolated molecules to be achieved with great accuracy and precision. They are used for the evaluation of nuclear moments, without shielding impacts on the bare nuclei, for: ^10/11B, ¹³C, ¹⁴N, ¹⁷O, ¹⁹F, ²¹Ne, ²⁹Si, ³¹P, ³³S, ^35/37Cl, ³³S, ⁸³Kr, ^129/131Xe, and ¹⁸³W. On the other hand, new results of nuclear moments were used for the reevaluation of absolute nuclear magnetic shielding in the molecules under study. Additionally, ³He gas in water solutions of lithium and sodium salts was used for measuring ^6/7Li and ²³Na magnetic moments and reevaluating the shielding parameters of Li⁺ and Na⁺ water-solvated cations. In this paper, guest ³He atoms that play a role in probing the electron density in many host macromolecules are also presented. Full article

(This article belongs to the Section Experimental and Computational Spectroscopy)

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34 pages, 4640 KiB

Open AccessFeature PaperReview

¹²⁹Xe: A Wide-Ranging NMR Probe for Multiscale Structures

by Matteo Boventi, Michele Mauri and Roberto Simonutti

Appl. Sci. 2022, 12(6), 3152; https://doi.org/10.3390/app12063152 - 19 Mar 2022

Cited by 11 | Viewed by 3591

Abstract

Porous materials are ubiquitous systems with a large variety of applications from catalysis to polymer science, from soil to life science, from separation to building materials. Many relevant systems of biological or synthetic origin exhibit a hierarchy, defined as spatial organization over several [...] Read more.

Porous materials are ubiquitous systems with a large variety of applications from catalysis to polymer science, from soil to life science, from separation to building materials. Many relevant systems of biological or synthetic origin exhibit a hierarchy, defined as spatial organization over several length scales. Their characterization is often elusive, since many techniques can only be employed to probe a single length scale, like the nanometric or the micrometric levels. Moreover, some multiscale systems lack tridimensional order, further reducing the possibilities of investigation. ¹²⁹Xe nuclear magnetic resonance (NMR) provides a unique and comprehensive description of multiscale porous materials by exploiting the adsorption and diffusion of xenon atoms. NMR parameters like chemical shift, relaxation times, and diffusion coefficient allow the probing of structures from a few angstroms to microns at the same time. Xenon can evaluate the size and shape of a variety of accessible volumes such as pores, layers, and tunnels, and the chemical nature of their surface. The dynamic nature of the probe provides a simultaneous exploration of different scales, informing on complex features such as the relative accessibility of different populations of pores. In this review, the basic principles of this technique will be presented along with some selected applications, focusing on its ability to characterize multiscale materials. Full article

(This article belongs to the Special Issue Room above the Bottom: Materials between the Nano and Micro Scale)

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20 pages, 2378 KiB

Open AccessReview

Explorations of Magnetic Properties of Noble Gases: The Past, Present, and Future

by Włodzimierz Makulski

Magnetochemistry 2020, 6(4), 65; https://doi.org/10.3390/magnetochemistry6040065 - 23 Nov 2020

Cited by 5 | Viewed by 4961

Abstract

In recent years, we have seen spectacular growth in the experimental and theoretical investigations of magnetic properties of small subatomic particles: electrons, positrons, muons, and neutrinos. However, conventional methods for establishing these properties for atomic nuclei are also in progress, due to new, [...] Read more.

In recent years, we have seen spectacular growth in the experimental and theoretical investigations of magnetic properties of small subatomic particles: electrons, positrons, muons, and neutrinos. However, conventional methods for establishing these properties for atomic nuclei are also in progress, due to new, more sophisticated theoretical achievements and experimental results performed using modern spectroscopic devices. In this review, a brief outline of the history of experiments with nuclear magnetic moments in magnetic fields of noble gases is provided. In particular, nuclear magnetic resonance (NMR) and atomic beam magnetic resonance (ABMR) measurements are included in this text. Various aspects of NMR methodology performed in the gas phase are discussed in detail. The basic achievements of this research are reviewed, and the main features of the methods for the noble gas isotopes: ³He, ²¹Ne, ⁸³Kr, ¹²⁹Xe, and ¹³¹Xe are clarified. A comprehensive description of short lived isotopes of argon (Ar) and radon (Rn) measurements is included. Remarks on the theoretical calculations and future experimental intentions of nuclear magnetic moments of noble gases are also provided. Full article

(This article belongs to the Special Issue Review Papers on Magnetic Resonances)

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96 pages, 9298 KiB

Open AccessReview

Molecular Sensing with Host Systems for Hyperpolarized ¹²⁹Xe

by Jabadurai Jayapaul and Leif Schröder

Molecules 2020, 25(20), 4627; https://doi.org/10.3390/molecules25204627 - 11 Oct 2020

Cited by 27 | Viewed by 5690

Abstract

Hyperpolarized noble gases have been used early on in applications for sensitivity enhanced NMR. ¹²⁹Xe has been explored for various applications because it can be used beyond the gas-driven examination of void spaces. Its solubility in aqueous solutions and its affinity for [...] Read more.

Hyperpolarized noble gases have been used early on in applications for sensitivity enhanced NMR. ¹²⁹Xe has been explored for various applications because it can be used beyond the gas-driven examination of void spaces. Its solubility in aqueous solutions and its affinity for hydrophobic binding pockets allows “functionalization” through combination with host structures that bind one or multiple gas atoms. Moreover, the transient nature of gas binding in such hosts allows the combination with another signal enhancement technique, namely chemical exchange saturation transfer (CEST). Different systems have been investigated for implementing various types of so-called Xe biosensors where the gas binds to a targeted host to address molecular markers or to sense biophysical parameters. This review summarizes developments in biosensor design and synthesis for achieving molecular sensing with NMR at unprecedented sensitivity. Aspects regarding Xe exchange kinetics and chemical engineering of various classes of hosts for an efficient build-up of the CEST effect will also be discussed as well as the cavity design of host molecules to identify a pool of bound Xe. The concept is presented in the broader context of reporter design with insights from other modalities that are helpful for advancing the field of Xe biosensors. Full article

(This article belongs to the Special Issue Hyperpolarized Molecules for Applications in Chemistry and Biomedicine)

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38 pages, 4321 KiB

Open AccessReview

Probing Reversible Guest Binding with Hyperpolarized ¹²⁹Xe-NMR: Characteristics and Applications for Cucurbit[n]urils

by Jabadurai Jayapaul and Leif Schröder

Molecules 2020, 25(4), 957; https://doi.org/10.3390/molecules25040957 - 20 Feb 2020

Cited by 15 | Viewed by 4979

Abstract

Cucurbit[n]urils (CB[n]s) are a family of macrocyclic host molecules that find various applications in drug delivery, molecular switching, and dye displacement assays. The CB[n]s with n = 5–7 have also been studied with ¹²⁹Xe-NMR. They bind [...] Read more.

Cucurbit[n]urils (CB[n]s) are a family of macrocyclic host molecules that find various applications in drug delivery, molecular switching, and dye displacement assays. The CB[n]s with n = 5–7 have also been studied with ¹²⁹Xe-NMR. They bind the noble gas with a large range of exchange rates. Starting with insights from conventional direct detection of bound Xe, this review summarizes recent achievements with chemical exchange saturation transfer (CEST) detection of efficiently exchanging Xe in various CB[n]-based supramolecular systems. Unprecedented sensitivity has been reached by combining the CEST method with hyperpolarized Xe, the production of which is also briefly described. Applications such as displacement assays for enzyme activity detection and rotaxanes as emerging types of Xe biosensors are likewise discussed in the context of biomedical applications and pinpoint future directions for translating this field to preclinical studies. Full article

(This article belongs to the Special Issue Characterization Techniques in Supramolecular Chemistry)

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16 pages, 2918 KiB

Open AccessFeature PaperArticle

Dual Stimuli-Responsive P(NIPAAm-co-SPA) Copolymers: Synthesis and Response in Solution and in Films

by Oliver Grimm and Felix H. Schacher

Polymers 2018, 10(6), 645; https://doi.org/10.3390/polym10060645 - 9 Jun 2018

Cited by 20 | Viewed by 6687

Abstract

We present the synthesis and solution properties of dual stimuli-responsive poly(N-isopropylacrylamide-co-spiropyran acrylate) (P(NIPAAm-co-SPA)) copolymers of varying composition prepared via nitroxide-mediated copolymerization. The resulting copolymers feature molar masses from 40,000 to 100,000 g/mol according to static light scattering [...] Read more.

We present the synthesis and solution properties of dual stimuli-responsive poly(N-isopropylacrylamide-co-spiropyran acrylate) (P(NIPAAm-co-SPA)) copolymers of varying composition prepared via nitroxide-mediated copolymerization. The resulting copolymers feature molar masses from 40,000 to 100,000 g/mol according to static light scattering and an SPA content of up to 5.3%. The latter was determined by ¹H NMR spectroscopy and UV–Vis spectroscopy. These materials exhibit reversible response upon irradiation in polymeric films for a minimum of three cycles; their response in solution to both light and temperature was also investigated in an aqueous TRIS buffer (pH 8). Irradiation was carried out using LED setups with wavelengths of 365 and 590 nm. In aqueous solution, a custom-made setup using a fiber-coupled 200 W Hg(Xe) lamp with 340 and 540 nm filters was used and additional heating of the copolymer solutions during irradiation allowed to study influence of the presence of either the spiropyran or merocyanine form on the cloud point temperature. Hereby, it was found that increasing the SPA content leads to a more pronounced difference between both states and decreasing cloud points in general. Full article

(This article belongs to the Special Issue Hydrophilic Polymers)

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36 pages, 2414 KiB

Open AccessReview

Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs)

by Herbert C. Hoffmann, Marta Debowski, Philipp Müller, Silvia Paasch, Irena Senkovska, Stefan Kaskel and Eike Brunner

Materials 2012, 5(12), 2537-2572; https://doi.org/10.3390/ma5122537 - 28 Nov 2012

Cited by 135 | Viewed by 18574

Abstract

Nuclear Magnetic Resonance (NMR) spectroscopy is a well-established method for the investigation of various types of porous materials. During the past decade, metal–organic frameworks have attracted increasing research interest. Solid-state NMR spectroscopy has rapidly evolved into an important tool for the study of [...] Read more.

Nuclear Magnetic Resonance (NMR) spectroscopy is a well-established method for the investigation of various types of porous materials. During the past decade, metal–organic frameworks have attracted increasing research interest. Solid-state NMR spectroscopy has rapidly evolved into an important tool for the study of the structure, dynamics and flexibility of these materials, as well as for the characterization of host–guest interactions with adsorbed species such as xenon, carbon dioxide, water, and many others. The present review introduces and highlights recent developments in this rapidly growing field. Full article

(This article belongs to the Special Issue NMR in Materials Science)

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18 pages, 1039 KiB

Open AccessArticle

Hyperpolarized Xenon Nuclear Magnetic Resonance (NMR) of Building Stone Materials

by Michele Mauri and Roberto Simonutti

Materials 2012, 5(9), 1722-1739; https://doi.org/10.3390/ma5091722 - 24 Sep 2012

Cited by 10 | Viewed by 7183

Abstract

We have investigated several building stone materials, including minerals and rocks, using continuous flow hyperpolarized xenon (CF-HP) NMR spectroscopy to probe the surface composition and porosity. Chemical shift and line width values are consistent with petrographic information. Rare upfield shifts were measured and [...] Read more.

We have investigated several building stone materials, including minerals and rocks, using continuous flow hyperpolarized xenon (CF-HP) NMR spectroscopy to probe the surface composition and porosity. Chemical shift and line width values are consistent with petrographic information. Rare upfield shifts were measured and attributed to the presence of transition metal cations on the surface. The evolution of freshly cleaved rocks exposed to the atmosphere was also characterized. The CF-HP ¹²⁹Xe NMR technique is non-destructive and it could complement currently used techniques, like porosimetry and microscopy, providing additional information on the chemical nature of the rock surface and its evolution. Full article

(This article belongs to the Special Issue NMR in Materials Science)

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