Observation of proximities between spin-1/2 and quadrupolar nuclei in solids: Improved robustness to chemical shielding using adiabatic symmetry-based recoupling.

We introduce a novel heteronuclear dipolar recoupling based on the R2 symmetry, which uses the tanh/tan (tt) shaped pulse as a basic inversion element and is denoted R2(tt). Using first-order average Hamiltonian theory, we show that this sequence is non-γ-encoded and that it reintroduces the |m| = 1 spatial component of the Chemical Shift Anisotropy (CSA) of the irradiated isotope and its heteronuclear dipolar interactions. Using numerical simulations and one-dimensional (1D) Al-{P} through-space D-HMQC (Dipolar Heteronuclear Multiple-Quantum Correlation) experiments on VPI-5, we compare the performances of this recoupling to those of other non-γ-encoded |m| = 1 heteronuclear recoupling schemes: REDOR (Rotational-Echo DOuble Resonance), SFAM (Simultaneous Frequency and Amplitude Modulation) and R4(tt).

Dynamic nuclear polarization for sensitivity enhancement in modern solid-state NMR.

The field of dynamic nuclear polarization has undergone tremendous developments and diversification since its inception more than 6 decades ago. In this review we provide an in-depth overview of the relevant topics involved in DNP-enhanced MAS NMR spectroscopy. This includes the theoretical description of DNP mechanisms as well as of the polarization transfer pathways that can lead to a uniform or selective spreading of polarization between nuclear spins.

γ-Independent through-space hetero-nuclear correlation between spin-1/2 and quadrupolar nuclei in solids.

We introduce novel sequences using indirect detection to correlate quadrupolar nuclei and spin-1/2 isotopes, other than H and F. These sequences use γ-encoded symmetry-based RN schemes that reintroduce the space component |m| = 1 of the heteronuclear dipolar coupling. These schemes can be applied to the indirectly detected spin in Dipolar-mediated Heteronuclear Multiple-Quantum Correlation (D-HMQC) sequence or to the detected isotope in a novel sequence, named Dipolar-mediated Heteronuclear Universal-Quantum Correlation (D-HUQC).

Insights into the catalytic activity of nitridated fibrous silica (KCC-1) nanocatalysts from (15) N and (29) Si NMR spectroscopy enhanced by dynamic nuclear polarization.

Fibrous nanosilica (KCC-1) oxynitrides are promising solid-base catalysts. Paradoxically, when their nitrogen content increases, their catalytic activity decreases. This counterintuitive observation is explained here for the first time using (15) N-solid-state NMR spectroscopy enhanced by dynamic nuclear polarization.

Probing 27Al-13C proximities in metal-organic frameworks using dynamic nuclear polarization enhanced NMR spectroscopy.

We show how (27)Al-(13)C proximities in the microporous metal-organic framework MIL-100(Al) can be probed using advanced (27)Al-(13)C NMR methods boosted by Dynamic Nuclear Polarization.

Indirect and direct 29Si dynamic nuclear polarization of dispersed nanoparticles.

We show how the (29)Si NMR signals of dispersed inorganic nanoparticles of laponite® can be enhanced by Dynamic Nuclear Polarization (DNP). The direct DNP enhances the signals of (29)Si nuclei near unpaired electrons, whereas the indirect DNP via (1)H enhances the signals of more remote sites.

Detailed analysis of the TIMES and TIMES0 high-resolution MAS methods for high-resolution proton NMR.

We analyze and compare the specifications of TIMES and TIMES(0) proton high-resolution NMR methods for solid-state samples. This comparison is performed in terms of resolution versus magic-angle spinning (MAS) spinning speed, ν(R), rf-field amplitude, ν(1), and tilt-angle for the effective rf-field, θ(p). The chemical-shift and homo-nuclear dipolar scaling factors are calculated for both methods.