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NMR Characterization of Amorphous and Disordered Materials

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A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Materials Science".

Deadline for manuscript submissions: closed (30 June 2020) | Viewed by 27682

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Prof. Dr. Todd M. Alam

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Sandia National Laboratories, New Mexico, Department of Organic Material Sciences, NMR Spectroscopy Laboratory, Albuquerque, NW, USA
Interests: NMR spectroscopy characterization of materials; NMR diffusometry; polymer chemistry; aging and dynamics; energy related materials; Ab initio chemical shift calculations
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Special Issue Information

Dear Colleagues,

Nuclear magnetic resonance (NMR) spectroscopy continues to be a powerful technology for the characterization of materials at the molecular level. The application of new and advanced NMR techniques for probing amorphous or highly disordered materials continues to see major advances including the application of sophisticated heteronuclear, multiple dimensional, multiple quantum solid-state and solution NMR, dynamic nuclear polarization (DNP), fast magic angle spinning (MAS) NMR, and improved pulse field gradient (PFG) NMR diffusometry methods. The ability to probe nucleus-specific questions, combined with recent improvements in sensitivity, resolution, spin coherence manipulation, quantum chemical calculations, and multivariate/chemometric analysis, render NMR a rich field. These improvements are coupled with NMR’s ability to address an almost endless range of material properties including dynamics, binding events, surface interactions, phase transitions, morphology, reaction kinetics, hydrogen bond strengths, local and medium range structure, and ion/molecular diffusion and transport.

The focus of this Special Issue is to explore these recent NMR advances for the characterization of real-life materials being used in sensing, energy, quantum computing, advanced manufacturing, biomedical, and environmental remediation applications, including self-assembled materials, super-molecular and stimuli-responsive polymers, polymer membranes, composites, MOFS, liquid crystalline polymers, ceramics, glasses, biomaterials, catalyst, and surface-modified nanoparticles. This Issue will offer an overview of some of the exciting opportunities NMR can provide in material characterization.

Prof. Dr. Todd M. Alam
Guest Editor

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Keywords

solid-state NMR
MAS NMR
PFG NMR
materials
amorphous
structure
quantum chemical
morphology
structure

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Published Papers (6 papers)

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Research

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20 pages, 7645 KiB

Open AccessArticle

Heterogeneous Polymer Dynamics Explored Using Static ¹H NMR Spectra

by Todd M. Alam, Joshua P. Allers and Brad H. Jones

Int. J. Mol. Sci. 2020, 21(15), 5176; https://doi.org/10.3390/ijms21155176 - 22 Jul 2020

Cited by 6 | Viewed by 3538

Abstract

NMR spectroscopy continues to provide important molecular level details of dynamics in different polymer materials, ranging from rubbers to highly crosslinked composites. It has been argued that thermoset polymers containing dynamic and chemical heterogeneities can be fully cured at temperatures well below the final glass transition temperature (T_g). In this paper, we described the use of static solid-state ¹H NMR spectroscopy to measure the activation of different chain dynamics as a function of temperature. Near T_g, increasing polymer segmental chain fluctuations lead to dynamic averaging of the local homonuclear proton-proton (¹H-¹H) dipolar couplings, as reflected in the reduction of the NMR line shape second moment (M₂) when motions are faster than the magnitude of the dipolar coupling. In general, for polymer systems, distributions in the dynamic correlation times are commonly expected. To help identify the limitations and pitfalls of M₂ analyses, the impact of activation energy or, equivalently, correlation time distributions, on the analysis of ¹H NMR M₂ temperature variations is explored. It is shown by using normalized reference curves that the distributions in dynamic activation energies can be measured from the M₂ temperature behavior. An example of the M₂ analysis for a series of thermosetting polymers with systematically varied dynamic heterogeneity is presented and discussed. Full article

(This article belongs to the Special Issue NMR Characterization of Amorphous and Disordered Materials)

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16 pages, 3596 KiB

Open AccessArticle

Quantification of Uncoupled Spin Domains in Spin-Abundant Disordered Solids

by Brennan J. Walder and Todd M. Alam

Int. J. Mol. Sci. 2020, 21(11), 3938; https://doi.org/10.3390/ijms21113938 - 30 May 2020

Cited by 5 | Viewed by 2379

Abstract

Materials often contain minor heterogeneous phases that are difficult to characterize yet nonetheless significantly influence important properties. Here we describe a solid-state NMR strategy for quantifying minor heterogenous sample regions containing dilute, essentially uncoupled nuclei in materials where the remaining nuclei experience heteronuclear dipolar couplings. NMR signals from the coupled nuclei are dephased while NMR signals from the uncoupled nuclei can be amplified by one or two orders of magnitude using Carr-Meiboom-Purcell-Gill (CPMG) acquisition. The signal amplification by CPMG can be estimated allowing the concentration of the uncoupled spin regions to be determined even when direct observation of the uncoupled spin NMR signal in a single pulse experiment would require an impractically long duration of signal averaging. We use this method to quantify residual graphitic carbon using

^{13}

C CPMG NMR in poly(carbon monofluoride) samples synthesized by direct fluorination of carbon from various sources. Our detection limit for graphitic carbon in these materials is better than 0.05 mol%. The accuracy of the method is discussed and comparisons to other methods are drawn. Full article

(This article belongs to the Special Issue NMR Characterization of Amorphous and Disordered Materials)

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18 pages, 1254 KiB

Open AccessArticle

The Monetite Structure Probed by Advanced Solid-State NMR Experimentation at Fast Magic-Angle Spinning

by Yang Yu, Baltzar Stevensson, Michael Pujari-Palmer, Hua Guo, Håkan Engqvist and Mattias Edén

Int. J. Mol. Sci. 2019, 20(24), 6356; https://doi.org/10.3390/ijms20246356 - 17 Dec 2019

Cited by 19 | Viewed by 4161

Abstract

We present a solid-state nuclear magnetic resonance (NMR) spectroscopy study of the local

^{31}

P and

^{1}

H environments in monetite [CaHPO

_{4}

; dicalcium phosphate anhydrous (DCPA)], as well as their relative spatial proximities. Each of the three

^{1}

H NMR peaks [...] Read more.

We present a solid-state nuclear magnetic resonance (NMR) spectroscopy study of the local

^{31}

P and

^{1}

H environments in monetite [CaHPO

_{4}

; dicalcium phosphate anhydrous (DCPA)], as well as their relative spatial proximities. Each of the three

^{1}

H NMR peaks was unambiguously assigned to its respective crystallographically unique H site of monetite, while their pairwise spatial proximities were probed by homonuclear

^{1}

H–

^{1}

H double quantum–single quantum NMR experimentation under fast magic-angle spinning (MAS) of 66 kHz. We also examined the relative

^{1}

H–

^{31}

P proximities among the inequivalent {P1, P2} and {H1, H2, H3} sites in monetite; the corresponding shortest internuclear

^{1}

H–

^{31}

P distances accorded well with those of a previous neutron diffraction study. The NMR results from the monetite phase were also contrasted with those observed from the monetite component present in a pyrophosphate-bearing calcium phosphate cement, demonstrating that while the latter represents a disordered form of monetite, it shares all essential local features of the monetite structure. Full article

(This article belongs to the Special Issue NMR Characterization of Amorphous and Disordered Materials)

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10 pages, 1981 KiB

Open AccessArticle

Static Solid Relaxation Ordered Spectroscopy: SS-ROSY

by Gregory S. Boutis and Ravinath Kausik

Int. J. Mol. Sci. 2019, 20(23), 5888; https://doi.org/10.3390/ijms20235888 - 24 Nov 2019

Cited by 2 | Viewed by 2645

Abstract

A two-dimensional pulse sequence is introduced for correlating nuclear magnetic resonance anisotropic chemical shifts to a relaxation time (e.g., T₁) in solids under static conditions. The sequence begins with a preparatory stage for measuring relaxation times, and is followed by a multiple pulse sequence for homonuclear dipolar decoupling. Data analysis involves the use of Fourier transform, followed by a one-dimensional inverse Laplace transform for each frequency index. Experimental results acquired on solid samples demonstrate the general approach, and additional variations involving heteronuclear decoupling and magic angle spinning are discussed. Full article

(This article belongs to the Special Issue NMR Characterization of Amorphous and Disordered Materials)

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22 pages, 3066 KiB

Open AccessReview

A Practical Review of NMR Lineshapes for Spin-1/2 and Quadrupolar Nuclei in Disordered Materials

by Kuizhi Chen

Int. J. Mol. Sci. 2020, 21(16), 5666; https://doi.org/10.3390/ijms21165666 - 7 Aug 2020

Cited by 24 | Viewed by 7392

Abstract

NMR is a powerful spectroscopic method that can provide information on the structural disorder in solids, complementing scattering and diffraction techniques. The structural disorder in solids can generate a dispersion of local magnetic and electric fields, resulting in a distribution of isotropic chemical shift δ_iso and quadrupolar coupling C_Q. For spin-1/2 nuclei, the NMR linewidth and shape under high-resolution magic-angle spinning (MAS) reflects the distributions of isotropic chemical shift, providing a rich source of disorder information. For quadrupolar nuclei, the second-order quadrupolar broadening remains present even under MAS. In addition to isotropic chemical shift, structural disorder can impact the electric field gradient (EFG) and consequently the quadrupolar NMR parameters. The distributions of quadrupolar coupling and isotropic chemical shift are superimposed with the second-order quadrupolar broadening, but can be potentially characterized by MQMAS (multiple-quantum magic-angle spinning) spectroscopy. We review analyses of NMR lineshapes in 2D DQ–SQ (double-quantum single-quantum) and MQMAS spectroscopies, to provide a guide for more general lineshape analysis. In addition, methods to enhance the spectral resolution and sensitivity for quadrupolar nuclei are discussed, including NMR pulse techniques and the application of high magnetic fields. The role of magnetic field strength and its impact on the strategy of determining optimum NMR methods for disorder characterization are also discussed. Full article

(This article belongs to the Special Issue NMR Characterization of Amorphous and Disordered Materials)

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24 pages, 11436 KiB

Open AccessReview

NMR Investigations of Crystalline and Glassy Solid Electrolytes for Lithium Batteries: A Brief Review

by Daniel J Morales and Steven Greenbaum

Int. J. Mol. Sci. 2020, 21(9), 3402; https://doi.org/10.3390/ijms21093402 - 11 May 2020

Cited by 22 | Viewed by 6620

Abstract

The widespread use of energy storage for commercial products and services have led to great advancements in the field of lithium-based battery research. In particular, solid state lithium batteries show great promise for future commercial use, as solid electrolytes safely allow for the use of lithium-metal anodes, which can significantly increase the total energy density. Of the solid electrolytes, inorganic glass-ceramics and Li-based garnet electrolytes have received much attention in the past few years due to the high ionic conductivity achieved compared to polymer-based electrolytes. This review covers recent work on novel glassy and crystalline electrolyte materials, with a particular focus on the use of solid-state nuclear magnetic resonance spectroscopy for structural characterization and transport measurements. Full article

(This article belongs to the Special Issue NMR Characterization of Amorphous and Disordered Materials)

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