Microwave-free nuclear spin hyperpolarization through photo-CIDNP in static and rotating solids.

This study advances the theoretical foundation of photo-chemically induced dynamic nuclear polarization (photo-CIDNP)-a powerful mechanism for enhancing nuclear spin sensitivity without microwave irradiation. Using an operator-based effective Hamiltonian approach, we derive precise resonance matching conditions and identify key dipolar scaling factors governing the photo-CIDNP Hamiltonian under both static and magic-angle spinning conditions. Our analytical formulation of coherent evolution of photoexcited singlet state exhibits strong agreement with numerical simulations, reinforcing the validity of our theoretical framework.

Investigation of the structure and dynamics of amorphous calcium carbonate by NMR: stabilization by poly-aspartate and comparison to monohydrocalcite.

Dense amorphous phases are key intermediates in biomineralization pathways. Structural information is required to understand these pathways, but is, as per the amorphous nature, difficult to obtain. We report an investigation of amorphous calcium carbonate (ACC) with magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy.

Optimal control-based nuclear spin cross-polarization in the presence of complicating anisotropic interactions.

Cross-polarization is an indispensable part of solid state nuclear magnetic resonance spectroscopy to enhance sensitivity and extract structural information. However, the presence of certain anisotropic interactions, including chemical shift anisotropy and quadrupolar coupling, makes the inter-nuclear spin correlation experiments challenging. This impedes characterization of numerous materials and pharmaceutical compounds containing isotopes, such as F with large chemical shift anisotropy and Li, Na, Al, , with quadrupolar coupling.

Magic-NOVEL: Suppressing electron-electron coupling effects in pulsed DNP.

Pulsed dynamic nuclear polarization (DNP) enhances the nuclear magnetic resonance sensitivity by coherently transferring electron spin polarization to dipolar coupled nuclear spins. Recently, many new pulsed DNP techniques such as NOVEL, TOP, XiX, TPPM, and BEAM have been introduced. Despite significant progress, numerous challenges remain unsolved.

Colloidal pathways of amorphous calcium carbonate formation lead to distinct water environments and conductivity.

CaCO is the most abundant biomineral and a major constituent of incrustations arising from water hardness. Polycarboxylates play key roles in controlling mineralization. Herein, we present an analytical and spectroscopic study of polycarboxylate-stabilized amorphous CaCO (ACC) and its formation via a dense liquid precursor phase (DLP).

Dynamic nuclear polarization by two-pulse phase modulation.

The coherent transfer of electron spin polarization to nuclei by means of a microwave pulse sequence is a promising new approach to enhancing the sensitivity of solid-state nuclear magnetic resonance (NMR). The development of pulse sequences for dynamic nuclear polarization (DNP) of bulk nuclei is far from complete, as is the understanding of what makes a good DNP sequence. In this context, we introduce a new sequence, termed Two-Pulse Phase Modulation (TPPM) DNP.

Efficient Pulsed Dynamic Nuclear Polarization with the X-Inverse-X Sequence.

Pulsed dynamic nuclear polarization (DNP) is a promising new approach to enhancing the sensitivity of high-resolution magic-angle spinning (MAS) NMR. In pulsed DNP, the transfer of polarization from unpaired electrons to nuclei (usually H) is induced by a sequence of microwave pulses. Enhancement factors of the thermal H polarization are expected to be independent of the magnetic field, and sample heating by absorption of microwave irradiation will be strongly reduced.