Application Of Solid-state Nuclear Magnetic Resonance Research Articles

Dynamic Nuclear Polarization Solid-State NMR Spectroscopy for Materials Research

Solid-state nuclear magnetic resonance (NMR) spectroscopy has increasingly been used for materials characterization as it enables selective detection of elements of interest, as well as their local structure and dynamic properties. Nevertheless, utilization of NMR is limited by its inherent low sensitivity. The development of dynamic nuclear polarization (DNP) approaches, which provide enormous sensitivity gain in NMR through the transfer of polarization from electron spins, has transformed the application of solid-state NMR in materials science. In this review, we outline the opportunities for materials characterization that DNP has opened up. We describe the main DNP mechanisms available, their implementation, and the kinds of insight they can provide across different materials classes, from surfaces and interfaces to defects in the bulk of solids. Finally, we discuss the current limitations of the approach and provide an outlook on future developments for DNP-enhanced NMR spectroscopy in materials science.

Structure of Carbon-Coated C12A7 Electride via Solid-State NMR and DFT Calculations

C12A7 calcium aluminate electride (C12A7:e–) is a novel inorganic functional material with mayenite crystal structure. Because of its physical and chemical properties, C12A7:e– can find application as a catalyst carrier in various reactions, including ammonia synthesis. However, the low specific area of this material imposes limitations on its use in catalysis. This limitation can be circumvented by synthesis within carbon nanoreactors as the carbon-coated particles resist sintering. We investigate by solid-state 27Al nuclear magnetic resonance (NMR) spectroscopy the structure of C12A7 electride prepared by the carbon nanoreactor process. An accurate determination of NMR parameters via simultaneous application of both DFT calculations and solid-state NMR proved the structure of carbon-coated C12A7 electride to be identical to the one of materials synthesized by more conventional routes. It was shown that the conducting electrons of C12A7:e– do not alter the cage structure, thus leading to similar NMR para...

Solid-state NMR studies of amyloid fibril structure.

Current interest in amyloid fibrils stems from their involvement in neurodegenerative and other diseases and from their role as an alternative structural state for many peptides and proteins. Solid-state nuclear magnetic resonance (NMR) methods have the unique capability of providing detailed structural constraints for amyloid fibrils, sufficient for the development of full molecular models. In this article, recent progress in the application of solid-state NMR to fibrils associated with Alzheimer's disease, prion fibrils, and related systems is reviewed, along with relevant developments in solid-state NMR techniques and technology.

Recent advances in solid-state NMR spectroscopy of quadrupolar nuclei

Nuclear magnetic resonance (NMR) spectroscopy of quadrupolar nuclei (i.e., those with a spin quantum number I > 1/2) has always been viewed as "difficult" owing to the presence of an anisotropic broadening arising from the interaction of the nuclear electric quadrupole moment with the electric field gradient. This quadrupolar interaction can be considerable, resulting in broadening of the spectral resonances often over many MHz. Furthermore, magic-angle spinning (MAS), a conventional approach for increasing the resolution in solid-state NMR, is often unable to remove the broadening completely and high-resolution spectra are generally not obtained. Despite the vast amount of information contained in the anisotropic linewidths and lineshapes, the resolution and sensitivity challenges have, until recently, somewhat limited the application of solid-state NMR for quadrupolar nuclei. In general, structural information, such as that obtained through recoupling techniques or from two-dimensional correlation spectroscopy, is much more difficult to extract easily and accurately. However, recent advances in magnet design, probe hardware and pulse sequence development have significantly improved the ease with which quadrupolar spins can be studied and high-resolution spectra can be obtained, and recent applications are beginning to exploit the wealth of information available. In this discussion, we highlight just a few of the recent developments in this area, including new state-of-the art correlation experiments, the expanding study of nuclei with low gyromagnetic ratio, gamma, the increasing application of first-principles calculations in the solid state, and methods which exploit the quadrupolar broadening to provide information on dynamics. Whilst not a complete review, it is hoped that this brief overview of some of the more exciting recent developments can provide insight into the challenges, and the rewards, involved in the NMR study of quadrupolar nuclei.

Cs 4P 2Se 10: A new compound discovered with the application of solid-state and high temperature NMR

The new compound Cs 4P 2Se 10 was serendipitously produced in high purity during a high-temperature synthesis done in a nuclear magnetic resonance (NMR) spectrometer. 31P magic angle spinning (MAS) NMR of the products of the synthesis revealed that the dominant phosphorus-containing product had a chemical shift of −52.8 ppm that could not be assigned to any known compound. Deep reddish brown well-formed plate-like crystals were isolated from the NMR reaction ampoule and the structure was solved with X-ray diffraction. Cs 4P 2Se 10 has the triclinic space group P-1 with a=7.3587(11) Å, b=7.4546(11) Å, c=10.1420(15) Å, α=85.938(2)°, β=88.055(2)°, and γ=85.609(2)° and contains the [P 2Se 10] 4− anion. To our knowledge, this is the first compound containing this anion that is composed of two tetrahedral (PSe 4) units connected by a diselenide linkage. It was also possible to form a glass by quenching the melt in ice water, and Cs 4P 2Se 10 was recovered upon annealing. The static 31P NMR spectrum at 350 °C contained a single peak with a −35 ppm chemical shift and a ∼7 ppm peak width. This study highlights the potential of solid-state and high-temperature NMR for aiding discovery of new compounds and for probing the species that exist at high temperature.

Recent developments in solid-state nuclear magnetic resonance of quadrupolar nuclei and applications to biological systems

Recent advances in nuclear magnetic resonance (NMR) methodology and improvements in high-field NMR instrumentation have generated a new wave of research interests in the application of solid-state NMR to the study of quadrupolar nuclei. These developments now permit increasingly complex biological systems to be probed by quadrupolar NMR. In this review I describe a few recent developments in NMR studies of quadrupolar nuclei and demonstrate the potential of solid-state quadrupolar NMR in the study of biological systems. In particular, I discuss the application of solid-state NMR of 17O, 67Zn, 59Co, 23Na, and 39K nuclei with a prognosis for future work.Key words: nuclear magnetic resonance, quadrupole, solid state, biological system.

Application of solid-state NMR (13C and29Si CP/MAS NMR) spectroscopy to the characterization of alkenyltrialkoxysilane and trialkoxysilyl-terminated polyisoprene grafting onto silica microparticles

The solid-state Nuclear Magnetic Resonance (NMR) was used to characterize surfaces of silica gels chemically modified by alkenyltrialkoxysilanes and trialkoxysilyl terminated 1,4-polyisoprenes. The formation of covalent bonds created between alkoxy functional groups from alkenyltrialkoxysilane or trialkoxysilyl-terminated 1,4-polyisoprene and silanol groups on silica was clearly demonstrated by means of 13C and 29Si CP/MAS NMR spectroscopy. Quantitative data, including calculation of the grafting yields in relation with the initial silanol concentrations, were also obtained by using solid-state 29Si-NMR leading to a final well-defined characterization of the silica surfaces. A relatively good agreement was noticed between the grafting yields calculated from 29Si-NMR spectra and those determined from other analytical techniques such as Wijs titration or elementary analysis. The reactivity of the various silica silanols towards each coupling agent was clearly characterized and estimated, as were the proportions of the various grafted structures formed at the silica surface. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 437–453, 1998

Recent developments in solid-state nuclear magnetic resonance of quadrupolar nuclei and applications to biological systems.

Recent advances in nuclear magnetic resonance (NMR) methodology and improvements in high-field NMR instrumentation have generated a new wave of research interests in the application of solid-state NMR to the study of quadrupolar nuclei. These developments now permit increasingly complex biological systems to be probed by quadrupolar NMR. In this review I describe a few recent developments in NMR studies of quadrupolar nuclei and demonstrate the potential of solid-state quadrupolar NMR in the study of biological systems. In particular, I discuss the application of solid-state NMR of (17)O, 67Zn, 59Co, 23Na, and 39K nuclei with a prognosis for future work.

A solid-state 15N NMR spectroscopic investigation of the origin of nitrogen structures in coal

Solid-state 15N nuclear magnetic resonance (NMR) spectroscopy is a technique that has been available for the study of nitrigen compounds for many years but only recently has been applied to the study of nitrogen in coal due to the extremely low sensitivity of the 15N-isotope. Reported here is the application of 15N NMR to a maturation series of undegraded plant material, plant composts, sediments, and coal samples for the purpose of investigating the alterations of nitrogen functional groups during peat and coal formation. Spectroscopic parameters such as relaxation times and cross polarization dynamics were determined for 15N-enriched plant composts to establish the optimal NMR conditions to be used for natural abundance 15N measurements on samples not enriched in 15N. The results show that up to the peat stage most of the nitrogen occurs as amide nitrogen, which derives from biogenic precursors (presumably proteins). Upon increasing coalification, pyrrolic-N becomes the dominant form in the macromolecular coal network. Pyrrolic-N in coals may be derived from selective preservation of biogenic pyrroles or by rearrangement of amide chains during maturation. Pyridinic-N does not appear to be a major constituent of coal nitrogen of the coals studied here. Our successful application of solid-state 15N NMR to coal samples has provided new insights and understanding of coal-nitrogen chemistry.

Solid-state nuclear magnetic resonance spectroscopy: theory and pharmaceutical applications.

The theory of solid-state nuclear magnetic resonance (NMR) spectroscopy is reviewed, with specific discussions of magnetic interactions in the solid state. Each magnetic interaction (Zeeman, dipole-dipole, chemical-shift, spin-spin, and quadrupolar) is addressed and manifestations of these interactions in the solid state NMR spectrum are explained. The techniques of high-power decoupling, magic-angle spinning, and cross-polarization, used to acquire highly resolved solid-state NMR spectra, are also illustrated. Application of solid-state NMR to pharmaceutical problem solving and methods development is then briefly reviewed.