Solid-State NMR - up to February 2008

Solid-State NMR - up to February 2008

Includes work on glasses by Brunet and Charpentier, 31P-Tl interactions in inorganic solids by Weliky, a multinuclear SSNMR study of sol-gels by O'Dell and Smith, and an evaluation of 17O EFG tensor parameters in L-alanine by Yamada.

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Solid State Nuclear Magnetic Resonance
Volume 33, Issues 1-2, January-February 2008, Pages 1-11
doi:10.1016/j.ssnmr.2007.12.001

Solid-state NMR characterization of a controlled-pore glass and of the effects of electron irradiation
F. Brunet, T. Charpentier, S. Le Caër and J.-P. Renault
a Laboratoire de Structure et de Dynamique par Résonance Magnétique CEA/Saclay, DSM/DRECAM/SCM URA 331 CNRS, F-91191 Gif-sur-Yvette, France
b Laboratoire de Radiolyse CEA/Saclay, DSM/DRECAM/SCM URA 331 CNRS, F-91191 Gif-sur-Yvette, France

Abstract
Controlled-pore glasses (CPGs) are silica-based materials which provide an adequate model system for a better understanding of the radiation chemistry of glasses, especially under nanoscopic confinement. This paper presents a characterization of a nanoporous CPG before and after electron irradiation using multinuclear solid-state magnetic resonance (NMR). 1H MAS NMR has been used for studying the surface proton sites and it is observed that the irradiation leads to a dehydration of the material. Accordingly, concerning the silicon sites near the surface, the observed variation of the Q4, Q3 and Q2 species from 1H–29Si CPMAS spectra shows an increase of the surface polymerization under irradiation, implying in majority a Q2 to Q3/Q4 conversion mechanism. Similarly, 1H–17O CPMAS measurements exhibit an increase of Si–O–Si groups at the expenses of Si–OH groups. In addition, modifications of the environment of the residual boron atoms are also put in evidence from 11B MAS and MQMAS NMR These data show that MAS NMR methods provide sensitive tools for the characterization of these porous glasses and of the tiny modifications occurring under electron irradiation.

Keywords: Solid-state NMR; Nanoporous controlled-pore glass; 1H; 29Si; 17O; 11B; Radiolysis

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Solid State Nuclear Magnetic Resonance
Volume 33, Issues 1-2, January-February 2008, Pages 12-15
doi:10.1016/j.ssnmr.2007.11.002
Improved resolution and detection of 31P–Tl J-couplings at 21 T in 31P magic angle spinning NMR spectra of inorganic compounds containing Tl/Bi/P/S
Matthew A. Gave, Kermit M. Johnson, Mercouri G. Kanatzidis and David P. Weliky
a Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
b Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
Received 8 August 2007; revised 31 October 2007. Available online 13 November 2007.

Abstract
For crystalline compounds containing Tl, Bi, P, and S, greatly improved chemical shift resolution was observed in 31P magic angle spinning spectra obtained at 21 T relative to spectra obtained at 9.4 T. In Hz units, the spectral linewidths were not strongly dependent on the applied field, which may be a result of a significant contribution to the linewidths from transverse relaxation. Comparison of the spectra at the two different fields confirmed that spectral splittings were due to two-bond phosphorus–thallium J-coupling. These results suggest that ultra-high field may be a useful tool to improve spectral resolution of spin Click to view the MathML source nuclei in crystalline inorganic compounds.

Keywords: 31P; Solid state NMR; High field NMR; Ultra-high field NMR; 900 MHz; J-coupling; Inorganic; Resolution; Chalcophosphate; Thiophosphate

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Solid State Nuclear Magnetic Resonance
Volume 33, Issues 1-2, January-February 2008, Pages 16-24
doi:10.1016/j.ssnmr.2007.11.001

Characterisation of sol–gel prepared (HfO2)x(SiO2)1-x (x=0.1, 0.2 and 0.4) by 1H, 13C, 17O and 29Si MAS NMR, FTIR and TGA
Luke A. O'Dell, Philips N. Gunawidjaja, Mark A. Holland, Gavin Mountjoy, Dave M. Pickup, Robert J. Newport and Mark E. Smith, Corresponding Author Contact Information, E-mail The Corresponding Author
a Department of Physics, University of Warwick, Coventry CV4 7AL, UK
b School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK

Abstract
The HfO2–SiO2 system is attracting interest as a possible new dielectric material in semiconductor devices. Knowledge of the location of hafnium within the silica network and the effect hafnium has on the structure will be central to the successful use of this material system in this application. Here, sol–gel techniques have been used to manufacture (HfO2)x(SiO2)1-x samples (x=0.1, 0.2 and 0.4, each heat treated at 250, 500 and 750 °C) and these have been characterised by magic angle spinning (MAS) NMR (1H, 13C, 17O, 29Si), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. 29Si MAS NMR showed that increasing the hafnia content decreases the connectivity of the silicate network, i.e. increases the range of differently connected SiO4 (Qn) units with more having increased numbers of non-bridging oxygens (i.e. lower n). FTIR and 17O MAS NMR showed unequivocally that the x=0.4 sample phase-separated at higher temperatures, while in the x=0.1 sample the hafnium was homogeneously mixed into the SiO2 phase without any phase separation.

Keywords: 17O NMR; Sol–gel; Nanoscale phase separation; Inorganic materials

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Solid State Nuclear Magnetic Resonance
Volume 33, Issues 1-2, January-February 2008, Pages 25-30
doi:10.1016/j.ssnmr.2007.10.006

Experimental determination of orientations for the 17O electric-field-gradient and chemical shielding tensors in l-alanine
Kazuhiko Yamada, Tadashi Shimizu, Miwako Asanuma, Toshio Yamazaki and Shigeyuki Yokoyama
a Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan
b Protein Research Group, Genomic Sciences Center, Yokohama Institute, RIKEN, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan
c Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan

Abstract
We have presented a solid-state 17O NMR study of [13C, 17O]-l-alanine. Using the experimental results for the 13C–17O dipolar vector and Euler angles, the absolute orientations of 17O chemical shielding (CS) and electric-field-gradient (EFG) tensors with respect to the molecular frame can be determined for l-alanine. The present results suggest that the intermediate EFG tensor components, VYY, lie in the carboxylate plane and parallel to the C–O bond directions, while the least shielded components, ?11, and the intermediate CS tensor components, ?22, roughly lie in the molecular plane and the direction of ?22 components are approximately 38° and 25° off the C–O bonds for O1 and O2, respectively. These results are in reasonable agreement with those of our quantum chemical calculations reported previously.

Keywords: Solid-state 17O NMR; Electric-field-gradient tensor; Chemical shielding tensor; 13C–17O dipolar vector