Dynamic Nuclear Polarization Solid-State NMR Spectroscopy for Materials Research

Abstract

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. Expected final online publication date for the Annual Review of Materials Research, Volume 52 is July 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Optimizing chemistry at the surface of prodrug-loaded cellulose nanofibrils with MAS-DNP

“…Following our recent work, we used Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP) to record sensitivity-enhanced solid-state NMR spectra of the functionalized CNF samples. MAS-DNP has recently become a key NMR approach to study with unprecedented sensitivity and thus atomistic details various types of systems from functional material to complex biomolecular systems [37][38][39][40][41] , including cellulosic materials 21,[42][43][44][45][46][47][48] . This approach complements standard ssNMR experiments which are routinely used to characterize nanocellulose but have also been shown to be limited in terms of sensitivity, especially to detect low weight percent chemical modifications on the surface of CNMs 20 .…”

Unravelling the molecular structure and confinement of an or-ganometallic catalyst heterogenized within amorphous porous polymers

“…33 Following the first proofs of concepts reported on model mesoporous silica matrices of high surface area, 34,35 recent applications have successfully covered a much wider range of materials. [36][37][38][39][40][41] In particular, we and others have recently shown the relevance of this methodology for the detailed investigation of the backbone structure of amorphous porous organic polymers. 22,[42][43][44][45][46] One-and two-dimensional DNP SENS spectra were recorded on the two materials to address the molecular composition of the Cp*Rh@IV(NO2) and Cp*Rh@V(NH2) functional polymers.…”

Solid-Effect Dynamic Nuclear Polarization in Viscous Liquids at 9.4 T Using Narrow-Line Polarizing Agents

“…One such method is dynamic nuclear polarization (DNP), in which electron spin polarization of paramagnetic molecules is transferred via resonant microwave excitation to the nuclear spins of the surrounding molecules. In the last decades, DNP has evolved, for both solid- and liquid-state NMR, to a powerful technique that has been used in numerous applications in biomolecular, − medical, surface, and materials sciences. − In the solid state, four DNP mechanisms can be operational, namely, the Overhauser effect (OE), − the solid effect (SE), , the cross effect (CE), , and thermal mixing (TM) . In general, these mechanisms work best at a sample temperature of ≤100 K and can give large signal enhancements of ≥100 in the presence of carefully selected polarizing agents. , In liquids, only the OE mechanism is active, which requires the time-dependent interaction between electrons and nuclei on a time scale comparable with the reciprocal of the electron Larmor frequency (1/ω e ).…”