We have obtained I70 nuclear magnetic resonance spectra of a variety of '70-labeled solids (Mg(OH)z, Ca(OH)*, boehmite (AlO(C talc (Mg3Si.,0,,(OH)2), (C6H,),SiOH, and amorphous Si02) using high-field static and "magioangle" sample spinning techniques, together with 'H cross polarization and dipolar decoupling. Our results show that large cross-polarization enhancements can be obtained and that reliable second-order quatipolar powder lineshapes can be observed under cross-polarization conditions. We have also investigated the dynamics of cross polarization for several samples, including measurements of cross-relaxation rates and 'H and I70 rotating-frame spin-lattice relaxation times. We show that rapid I70 rotating-frame spin-lattice relaxation reduces the cross-polarization enhancement in some cases and that differences in cross-relaxation rates can be used to "edit" spectra by selectively enhancing protonated oxygen resonances (in general, hydroxide versus oxide ions, in inorganic solids). When applied to high surface area metal oxides such as amorphous silica, this selectivity enables the observation of resonances from surface hydroxyl groups that are difficult to detect by conventional "0 NMR. Overall, the crosspolarization approach appears to have considerable utility for aiding in the interpretation of "0 NMR spectra of complex inorganic solids. 0 1988 Academic PBS, Inc
