1H Homonuclear dipolar decoupling using symmetry-based pulse sequences at ultra fast magic-angle spinning frequencies.

We demonstrate here the application of symmetry-based pulse sequences for homonuclear dipolar decoupling in solid-state NMR at magic-angle spinning (MAS) frequencies up to 65 kHz using moderate radiofrequency (RF) amplitudes. Theoretical arguments favouring the requirement of low RF amplitudes at high MAS frequencies are given for these sequences. A comparison with wPMLGmmxx¯ is given at 65 kHz of MAS frequency to emphasise that the symmetry-based pulse sequences have a lower RF amplitude requirement at high MAS frequencies.

A method for improved quantification of 1H NMR signals under low-resolution conditions for solids.

Accurate determination of (1)H NMR signal intensities is useful for quantitative analysis of the hydrogen content and also to determine the relative peak intensity ratios in different application scenarios. To this end we have investigated the reliability and sources of intensity errors in (1)H solid-state MAS NMR. If sufficient resolution can be achieved by very high spinning speeds and high magnetic fields, quantification is straight forward.

High-resolution 1H homonuclear dipolar recoupling NMR spectra of biological solids at MAS rates up to 67 kHz.

Two-dimensional (1)H homonuclear correlation NMR spectra of solids of biological interest have been recorded at high magnetic fields (14.1 and 18.8 T) and MAS rates up to 67 kHz, using RN(n)(nu) symmetry-based homonuclear recoupling and CRAMPS decoupling; this method affords exceptional spectral resolution and is well suited to probe (1)H-(1)H proximities in powdered solids.

(17)O DOR and other solid-state NMR studies concerning the basic properties of zeolites LSX.

We demonstrate complementary (1)H, (17)O, (27)Al and (29)Si measurements for basic low-silica-X zeolites, which were unloaded and pyrrole and formic acid-loaded. It was found that the acid-base-system is not stabile, if the loading exceeds one pyrrole molecule or two formic acid molecules per supercage.(17)O DOR NMR spectra exhibit at least four lines, which are broadened by a distribution of chemical shifts in a similar extend as the (29)Si MAS NMR spectra are broadened by distribution of Si-O-Al angles.