TY - JOUR
T1 - Oxygen-17 cross-polarization nmr spectroscopy of inorganic solids
AU - Walter, Thomas H.
AU - Turner, Gary L.
AU - Oldfield, Eric
N1 - Funding Information:
* This work was supported by the U.S. National Science Foundation Solid-State Chemistry Program (Grant DMR 86-40075, T.H.W.), the National Institutes of Health (HI-19481), and in part by the Mobil Foundation. 1 To whom correspondence should be addressed.
PY - 1988/1
Y1 - 1988/1
N2 - We have obtained 17O nuclear magnetic resonance spectra of a variety of 17O-labeled solids (Mg(OH)2, Ca(OH)2, boehmite (AlO(OH)), talc (Mg3Si4O10(OH)2), (C6H5)3SiOH, and amorphous SiO2) using high-field static and "magic-angle" sample spinning techniques, together with 1H cross polarization and dipolar decoupling. Our results show that large cross-polarization enhancements can be obtained and that reliable second-order quadrupolar 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 1H and 17O rotating-frame spin-lattice relaxation times. We show that rapid 17O 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 17O NMR. Overall, the cross-polarization approach appears to have considerable utility for aiding in the interpretation of 17O NMR spectra of complex inorganic solids.
AB - We have obtained 17O nuclear magnetic resonance spectra of a variety of 17O-labeled solids (Mg(OH)2, Ca(OH)2, boehmite (AlO(OH)), talc (Mg3Si4O10(OH)2), (C6H5)3SiOH, and amorphous SiO2) using high-field static and "magic-angle" sample spinning techniques, together with 1H cross polarization and dipolar decoupling. Our results show that large cross-polarization enhancements can be obtained and that reliable second-order quadrupolar 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 1H and 17O rotating-frame spin-lattice relaxation times. We show that rapid 17O 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 17O NMR. Overall, the cross-polarization approach appears to have considerable utility for aiding in the interpretation of 17O NMR spectra of complex inorganic solids.
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U2 - 10.1016/0022-2364(88)90205-3
DO - 10.1016/0022-2364(88)90205-3
M3 - Article
AN - SCOPUS:45549116892
SN - 0022-2364
VL - 76
SP - 106
EP - 120
JO - Journal of Magnetic Resonance (1969)
JF - Journal of Magnetic Resonance (1969)
IS - 1
ER -