01735nas a2200253 4500008004100000022001400041245009500055210006900150260009500219300001200314490000800326520082500334653002001159653002301179653001601202653002001218100002101238700001701259700002001276700001901296700002701315700001701342856012201359 2005 eng d a1090-780700aIncreasing the sensitivity of 2D high-resolution NMR methods applied to quadrupolar nuclei0 aIncreasing the sensitivity of 2D highresolution NMR methods appl a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcFEB a268-2780 v1723 a

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'(2) relaxation times. (C) 2004 Elsevier Inc. All rights reserved.

10ahigh-resolution10aquadrupolar nuclei10asensitivity10aSolid-state NMR1 aAmoureux, J., P.1 aDelevoye, L.1 aSteuernagel, S.1 aGan, Zhengting1 aGanapathy, Subramanian1 aMontagne, L. uhttps://library.ncl.res.in/content/increasing-sensitivity-2d-high-resolution-nmr-methods-applied-quadrupolar-nuclei-002690nas a2200313 4500008004100000022001400041245011600055210006900171260009500240300001200335490000800347520155000355653003601905653002801941653001101969653003001980653002002010653001802030653000802048100001902056700001702075700001702092700003502109700002702144700003002171700001902201700002602220856013002246 2006 eng d a0021-951700aEffect of spacer groups on the performance of MCM-41-supported platinum cluster-derived hydrogenation catalysts0 aEffect of spacer groups on the performance of MCM41supported pla a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcSEP a332-3390 v2423 a

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.

10afunctionalized inorganic oxides10ahydrogenation catalysts10aMCM-4110aplatinum carbonyl cluster10aSolid-state NMR10aspacer groups10aXPS1 aMaity, Niladri1 aBasu, Susmit1 aMapa, Maitri1 aRajamohanan, Pattuparambil, R.1 aGanapathy, Subramanian1 aGopinath, Chinnakonda, S.1 aBhaduri, Sumit1 aLahiri, Goutam, Kumar uhttps://library.ncl.res.in/content/effect-spacer-groups-performance-mcm-41-supported-platinum-cluster-derived-hydrogenation-102021nas a2200277 4500008004100000022001400041245012300055210006900178260009800247300001200345490000700357520099700364653002901361653002901390653002701419653001001446653002301456653002001479653001001499653000901509100002701518700001701545700002201562700002901584856013001613 2008 eng d a0749-158100aHeteronuclear dipolar decoupling effects on multiple-quantum and satellite-transition magic-angle spinning NMR spectra0 aHeteronuclear dipolar decoupling effects on multiplequantum and  aTHE ATRIUM, SOUTHERN GATE, CHICHESTER PO19 8SQ, W SUSSEX, ENGLANDbJOHN WILEY & SONS LTDcOCT a948-9540 v463 a

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.

10aheteronuclear broadening10aheteronuclear decoupling10ahomogeneous broadening10aMQMAS10aquadrupolar nuclei10aSolid-state NMR10aSTMAS10aTPPM1 aGanapathy, Subramanian1 aDelevoye, L.1 aArnoureux, J., P.1 aMadhu, Perunthiruthy, K. uhttps://library.ncl.res.in/content/heteronuclear-dipolar-decoupling-effects-multiple-quantum-and-satellite-transition-magic-001548nas a2200205 4500008004100000022001400041245009600055210006900151260007100220300001400291490000800305520074500313100001901058700003501077700002701112700003001139700001901169700002601188856012801214 2008 eng d a1932-744700aMCM-41-supported organometallic-derived nanopalladium as a selective hydrogenation catalyst0 aMCM41supported organometallicderived nanopalladium as a selectiv a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN a9428-94330 v1123 a

Palladium nanocatalysts have been prepared by anchoring (eta(3)-C(3)H(5))(2)Pd(2)Cl(2) onto dian-tine-functionalized MCM-41 supports followed by reaction with hydrogen under catalytic conditions. The catalyst precursor and used catalyst have been studied by solid-state NMR ((13)C, (29)Si), XPS, and TEM. The organometallic-derived catalyst exhibits the best performance (activity and selectivity) to date toward the selective hydrogenation of industrially relevant o- and m-chloronitrobenzene to the corresponding chloroaniline derivatives and is distinctly superior to 5% Pd/C. Grazing angle XPS studies reveal that conversion of the tethered molecular species to the nanoparticles of palladium produces a core-shell nanostructure.

1 aMaity, Niladri1 aRajamohanan, Pattuparambil, R.1 aGanapathy, Subramanian1 aGopinath, Chinnakonda, S.1 aBhaduri, Sumit1 aLahiri, Goutam, Kumar uhttps://library.ncl.res.in/content/mcm-41-supported-organometallic-derived-nanopalladium-selective-hydrogenation-catalyst-001846nas a2200229 4500008004100000022001400041245006000055210005900115260009500174300001200269490000600281520108900287653001501376653000901391653001201400653002501412100002101437700002001458700001701478700002701495856009401522 2008 eng d a1533-488000aSn-119 magic angle spinning NMR of nanocrystalline SnO20 aSn119 magic angle spinning NMR of nanocrystalline SnO2 a25650 NORTH LEWIS WAY, STEVENSON RANCH, CA 91381-1439 USAbAMER SCIENTIFIC PUBLISHERScJAN a321-3280 v83 a

Nanocrystalline SnO2 samples of different grain sizes, prepared by inert gas condensation technique (IGCT) and chemical precipitation method and conforming to the tetragonal phase, have been studied by variable speed (3-10 kHz) Sn-119 MAS NMR at 11.74 Tesla field. Sn-119 solid-state NMR results show that the IGCT prepared samples have good crystallinity and phase purity compared to the samples prepared by the chemical method. The determination of Sn-119 chemical shielding parameters (delta(iso), Delta delta and eta) from slow MAS spectra shows that the Sn-119 isotropic chemical shift (delta(iso)) is strongly influenced at smaller grain sizes, attributable to the change in the O2- local symmetry for the surface Sn-119 ions at smaller grain sizes. The observed line widths in MAS spectra are significantly larger than the life-time broadening due to spin-lattice (T-1) and spin-spin (T,) relaxation. The Sn-119 MAS NMR spectra are thus inhomogeneously broadened by a distribution of isotropic chemical shifts, the line broadening increasing with decrease in grain size.

10aHydrolysis10aIGCT10aMAS NMR10ananocrystalline SnO21 aSabarinathan, V.1 aChandran, Vinod1 aRamasamy, S.1 aGanapathy, Subramanian uhttps://library.ncl.res.in/content/sn-119-magic-angle-spinning-nmr-nanocrystalline-sno2-001530nas a2200193 4500008004100000022001400041245013200055210006900187260007300256300001200329490000800341520074800349100001601097700002901113700001601142700002001158700002701178856013101205 2009 eng d a0009-261400aSensitivity enhancement of Si-29 double-quantum dipolar recoupling spectroscopy by Carr-Purcell-Meiboom-Gill acquisition method0 aSensitivity enhancement of Si29 doublequantum dipolar recoupling aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAUG a287-2910 v4783 a

An enhancement in the detection sensitivity of dipolar recoupled Si-29 double-quantum magic-angle spinning experiment is shown with a Carr-Purcell-Meiboom-Gill (CPMG) train of pi pulses during the acquisition period. Symmetry-adapted pulse schemes, such as POST-C7 and SR26(4)(11), are used for the double-quantum excitation. Application of POST-C7-CPMG method for framework characterisation is demonstrated in the disordered and catalytically important ZSM-5 molecular sieve. Based on the observed double-quantum dipole-dipole correlations and the known T-site Si connectivities, the assignment of all the signals is made for the orthorhombic phase of the as-synthesised (CN form) material. (C) 2009 Elsevier B. V. All rights reserved.

1 aGoswami, M.1 aMadhu, Perunthiruthy, K.1 aDittmer, J.1 aNielsen, N., C.1 aGanapathy, Subramanian uhttps://library.ncl.res.in/content/sensitivity-enhancement-si-29-double-quantum-dipolar-recoupling-spectroscopy-carr-purcell-002013nas a2200169 4500008004100000022001400041245012600055210006900181260007100250300001400321490000800335520130800343100002101651700001701672700002701689856012701716 2010 eng d a1520-610600aPerturbations to Al-27 electric field gradients in nanocrystalline alpha-Al2O3 studied by high-resolution solid-state NMR0 aPerturbations to Al27 electric field gradients in nanocrystallin a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB a1775-17810 v1143 a

Al-27 solid-state NMR has been employed to study the perturbations to Al-27 electric field gradients for the aluminum environments in nanocrystalline alpha-alumina. Triple quantum magic angle spinning experiments show that the octahedral aluminum coordination remains unchanged down to 12 nm, although severe perturbations to Al-27 electric field gradients are noticed at 28 nm and below. 3Q-MAS and SATRAS experimental data of nano alpha-alumina have been analyzed through extensive spectral simulations to probe Al-27 electric field gradients of aluminum in the grains and grain boundaries. While the aluminum in the grains has a unique field gradient tensor, the same octahedrally coordinated aluminum environments in the grain boundaries suffer a distribution of electric field gradients. This is evidenced by data analysis of both 3Q-MAS and SATRAS spectra. By invoking the Gaussian isotropic model, in which the (C-Q, eta(Q)) parameter space is discretely sampled by the Czjzek distribution, we have been able to analyze the Al-27 SATRAS spectra of nanocrystalline alpha-alumina samples having grain sizes of 52, 28, 20, and 12 nm. Good agreement between experimental and simulated spectra has led to the quantitative determination of grain and grain boundary components in these materials.

1 aSabarinathan, V.1 aRamasamy, S.1 aGanapathy, Subramanian uhttps://library.ncl.res.in/content/perturbations-al-27-electric-field-gradients-nanocrystalline-alpha-al2o3-studied-high-002238nas a2200181 4500008004100000022001400041245012200055210006900177260007100246300001400317490000800331520151200339100002001851700001701871700001501888700002701903856012601930 2011 eng d a1520-610600aIdentification of sublattice damages in swift heavy ion irradiated N-doped 6H-SiC polytype studied by solid state NMR0 aIdentification of sublattice damages in swift heavy ion irradiat a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN a7766-77720 v1153 a

We have studied N-doped 6H-SiC in its pristine and Swift Heavy Ion (SHI) irradiated (150 MeV Ag12+ ions) forms by solid state Nuclear Magnetic Resonance (NMR) at 7.01 T using C-13 and Si-29 as probe nuclei under magic angle spinning. We show that increased levels of nitrogen doping, than used before, lead to the observation of Knight shifts emanating from an increase in electron density in the conduction band, which in C-13 far exceed those in Si-29 MAS spectra. We have rationalized the differential effects in the MAS spectra and site-dependent paramagnetic shifts in terms of the nitrogen doping at the A, B, and C lattice sites. N-doping has a profound effect on Si-29 spin-lattice relaxation, and the site-dependent relaxation behavior is attributed to a difference in conduction electron properties at the different lattice sites. Si-29 T-1 measurements serve to identify the sublattice damages in SHI irradiated 6H-SiC. By determining the spin-lattice relaxation rates as a function of the SHI irradiation ion fluences, the change in relaxation behavior is correlated to the damage production mechanism. The sublattice damage leads to discernable changes in the interaction between the mobile unpaired electrons in the conduction band and the nuclear site, which profoundly influence the NMR relaxation properties. Our relaxation studies also provide evidence for site-dependent localized effects and a decrease in carrier spin density in the conduction band for the SHI irradiated 6H-SiC.

1 aViswanathan, E.1 aKanjilal, D.1 aSivaji, K.1 aGanapathy, Subramanian uhttps://library.ncl.res.in/content/identification-sublattice-damages-swift-heavy-ion-irradiated-n-doped-6h-sic-polytype-002657nas a2200217 4500008004100000022001400041245015700055210006900212260000800281300001400289490000800303520182900311100001702140700002102157700002602178700002802204700002702232700002802259700002502287856012702312 2019 eng d a1932-744700aLithium speciation in the LiPF6/PC electrolyte studied by two dimensional heteronuclear overhauser enhancement and pulse field gradient diffusometry NMR0 aLithium speciation in the LiPF6PC electrolyte studied by two dim cAPR a9661-96720 v1233 a

Electrolytic dissociation of lithium hexafluorophosphate (LiPF6) in the nonaqueous cyclic propylene carbonate (PC) has been investigated in the wide range of concentration (0.05-3.5 M) by Li-7 solution-state nuclear magnetic resonance (NMR) spectroscopy. Two-dimensional heteronuclear Overhauser enhancement spectroscopy NMR experiments have not only enabled the cation solvation and ion-pairing to be directly monitored but additionally evidence anion solvent interaction at higher concentrations (>1.2 M) of the PC electrolyte. Preliminary analysis of kinetic nOe data has been made to determine site-dependent cross-relaxation rates for the spatial interaction of the solvent with the Li+ cation and the PF6- anion. The concentration dependence of the Li-7 NMR self-diffusion coefficient (D-self), determined using very strong pulsed magnetic field gradients (similar to 1700 Gauss/cm), depicts two breaks to mark the solvation and ion-pairing events in a distinct manner. This in turn has aided the determination of solvent coordination number and average sizes of solvated and ion-paired clusters. Our results indicate that in the contact ion pair (CIP)-dominated electrolyte (>2 M), lithium-ion mobility across the solvated and ion-paired environments appears to be inhibited which makes the spectral distinction of solvated and ion-paired environments possible. The concentration dependence of the Li-7 NMR spectral and diffusometry data is in striking correspondence with that of bulk conductivity measurements and point to the detrimental effect of CIP aggregates in impeding the ionic conductivity at high salt concentrations. These results have significance in understanding the structure and dynamics of lithium-ion solvates that are ubiquitous in the working environment of a lithium-ion battery.

1 aKumar, Vikas1 aReddy, Ravikanth1 aKumar, B., V. N. Phan1 aAvadhani, Chilukuri, V.1 aGanapathy, Subramanian1 aChandrakumar, Narayanan1 aSivaram, Swaminathan uhttps://library.ncl.res.in/content/lithium-speciation-lipf6pc-electrolyte-studied-two-dimensional-heteronuclear-overhauser