@article { ISI:000226728000011, title = {Increasing the sensitivity of 2D high-resolution NMR methods applied to quadrupolar nuclei}, journal = {Journal of Magnetic Resonance}, volume = {172}, number = {2}, year = {2005}, month = {FEB}, pages = {268-278}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

Gan and Kwak recently proposed a soft-pulse added mixing (SPAM) idea in the classical two-pulse multiple-quantum magic-angle spinning scheme. In the SPAM method, a soft pi/2 pulse is added after the second hard-pulse (conversion pulse) and all coherence orders in between them are constructively used to obtain the signal. We, here, further extend this idea to distributed samples where the signal mainly results from echo pathways and that from anti-echo pathways dies Out after a few t(1) increments. We show that, with a combination of SPAM and collection of fewer anti-echoes, an enhancement of the signal to noise ratio by a factor of ca. 3 may be obtained over the z-filtered version. This may prove to be useful even for samples with long T{\textquoteright}(2) relaxation times. (C) 2004 Elsevier Inc. All rights reserved.

}, keywords = {high-resolution, quadrupolar nuclei, sensitivity, Solid-state NMR}, issn = {1090-7807}, doi = {10.1016/j.jmr.2004.11.001}, author = {Amoureux, J. P. and Delevoye, L. and Steuernagel, S. and Gan, Zhengting and Ganapathy, Subramanian and Montagne, L.} } @article { ISI:000240781100009, title = {Effect of spacer groups on the performance of MCM-41-supported platinum cluster-derived hydrogenation catalysts}, journal = {Journal of Catalysis}, volume = {242}, number = {2}, year = {2006}, month = {SEP}, pages = {332-339}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

MCM-41 was functionalized with (EtO)(3)SiCH2Cl, (MeO)(3)SiCH2CH2CH2Cl, and (CH3)Cl2SiCH2Cl. The functionalized materials were characterized by solid-state NMR (CPMAS, Si-29 and C-13) and XPS. The NMR data indicate that three new silicon environments were created by(EtO)(3)SiCH2Cl and (MeO)(3)SiCH2CH2CH2Cl, whereas with (CH3)Cl2SiCH2Cl, two new silicon environments were obtained. XPS results from Si 2p core level and the valence band from the material functionalized by (MeO)(3)Si(CH2)(3)Cl was found to be the same as that of the corresponding fresh catalyst (1a), in contrast to that of the materials functionalized by the other two silane reagents. After further functionalization with triethylamine, these materials were used as inorganic anion exchangers to support the cluster anion [Pt-12(CO)(24)](2-). Solid-state NMR (29Si, C-13, N-15) was used to establish the presence of the quaternary ammonium group in the cluster-supported species. Analogous materials were also created using fumed silica as the support, and all of the cluster-supported materials were tested as catalysts for the hydrogenation of methyl pyruvate, acetophenone, nitrobenzene, benzonitrile, ethylacetoacetate, 4-nitrotoluene, cyclohexanone, allyl alcohol, and styrene. The best activity was obtained for the catalyst that had MCM-41 as the support and chloropropyl as the spacer group. TEM showed that the supports and the spacer groups had observable effects on the platinum crystallite size of the catalysts. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {functionalized inorganic oxides, hydrogenation catalysts, MCM-41, platinum carbonyl cluster, Solid-state NMR, spacer groups, XPS}, issn = {0021-9517}, doi = {10.1016/j.jcat.2006.06.016}, author = {Maity, Niladri and Basu, Susmit and Mapa, Maitri and Rajamohanan, Pattuparambil R. and Ganapathy, Subramanian and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000259337100008, title = {Heteronuclear dipolar decoupling effects on multiple-quantum and satellite-transition magic-angle spinning NMR spectra}, journal = {Magnetic Resonance in Chemistry}, volume = {46}, number = {10}, year = {2008}, month = {OCT}, pages = {948-954}, publisher = {JOHN WILEY \& SONS LTD}, type = {Article}, address = {THE ATRIUM, SOUTHERN GATE, CHICHESTER PO19 8SQ, W SUSSEX, ENGLAND}, abstract = {

We here report on the influence of heteronuclear dipolar decoupling on the Al-27 3QMAS, 5QMAS, and the double-quantum filter-satellite-transition magic-angle spinning (DQF-STMAS) spectra of a strongly dipolar-coupled system, gibbsite. The requirements for heteronuclear dipolar decoupling increase with the order of coherence evolving in the indirect dimension of a two-dimensional (2D) experiment. The isotropic line width of the high-resolution 2D spectra, in samples like gibbsite, is composed of four parts: the distribution of isotropic shifts (delta(ISO), delta(QIS)), the homogeneous broadening related to the proton-proton flip-flop terms, the Al-27-Al-27 homonulcear dipolar couplings, and the H-1-Al-27 heteronuclear dipolar couplings. It is shown that, even in the case of gibbsite, where a strong proton-proton bath exists, the main resolution limiting factor in these experiments resides in the H-1-Al-27 dipolar interaction. Copyright (C) 2008 John Wiley \& Sons, Ltd.

}, keywords = {heteronuclear broadening, heteronuclear decoupling, homogeneous broadening, MQMAS, quadrupolar nuclei, Solid-state NMR, STMAS, TPPM}, issn = {0749-1581}, doi = {10.1002/mrc.2286}, author = {Ganapathy, Subramanian and Delevoye, L. and Arnoureux, J. P. and Madhu, Perunthiruthy K.} }