Indirect covariance NMR spectroscopy of through-bond homo-nuclear correlations for quadrupolar nuclei in solids under high-resolution - doi:10.1016/j.ssnmr.2007.03.002
Bingwen Hu, Jean-Paul Amoureux and Julien Trebosc
UCCS, CNRS-8181, Lille University, FR-59652 Villeneuve d'Ascq, France
Received 20 November 2006; revised 26 February 2007. Available online 1 April 2007.
Indirect covariance NMR spectroscopy is demonstrated in solids, and we show that it can be used to obtain through-bond 2D homo-nuclear correlation spectra for quadrupolar nuclei under high-resolution. These spectra, generated with indirect covariance from a hetero-nuclear correlation spectrum, are equivalent to those recorded with the through-bond homo-nuclear hetero-nuclear single-quantum correlation (H-HSQC) method very recently proposed. However, the indirect covariance method can save a lot of experiment time, compared to the H-HSQC experiments, which allows introducing a high-resolution quadrupolar filter, thus providing a much better resolution, even on medium-field spectrometers. The covariance concept can be used to generate many different ‘indirectly-detected' high-resolution homo-nuclear correlation spectra with through-space or through-bond correlations for spin Click to view the MathML source or quadrupolar nuclei. We also propose a simple method that decreases the noise in all (direct or indirect) covariance methods.
Keywords: Indirect-covariance; GEN2D; H-HSQC experiment; J-coupling; MQ-HETCOR; ST-HETCOR; MQ-HOMCOR; ST-HOMCOR
A 27Al MAS NMR study of a sol–gel produced alumina: Identification of the NMR parameters of the theta-Al2O3 transition alumina phase - doi:10.1016/j.ssnmr.2007.05.002
L.A. O'Dell, S.L.P. Savin, A.V. Chadwick and M.E. Smith
Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
School of Physical Sciences, University of Kent, Canterbury, Kent, CT2 7NH, UK
Received 29 December 2006; revised 6 April 2007. Available online 13 May 2007.
27Al MAS NMR has been used to study a sol–gel prepared alumina annealed at various temperatures. Two-field simulation of the sample heated to 1200 °C confirmed the presence of corundum, as suggested by XRD, and also the presence of nanocrystalline ?-Al2O3. 27Al MAS NMR chemical shifts, quadrupolar coupling constants and asymmetry parameters are reported for the tetrahedral and octahedral aluminium sites within ?-Al2O3.
Keywords: 27Al MAS NMR; theta-alumina; NMR interaction parameters
Phosphorus-31 spin–lattice NMR relaxation in bone apatite and its mineral standards - doi:10.1016/j.ssnmr.2007.04.005
Agnieszka Kaflak and Waclaw
Medical University of Warsaw, Faculty of Pharmacy, Department of Inorganic and Analytical Chemistry, ul. Banacha 1, 02-097 Warszawa, Poland
Received 9 February 2007; revised 25 April 2007. Available online 16 May 2007.
Phosphorus-31 spin–lattice relaxation, both in the laboratory (B0=4.7 T) and rotating frame (B1=2.2 mT), was studied in the following samples: mineral of whole human bone (samples B1–B6), apatite prepared from bone (BHA), natural brushite (BRU), synthetic hydroxyapatite hydrated (HAh) and calcined (HAc), and synthetic carbonatoapatite of type B (CHA-B) with 9 wt% of CO32-. The T1P relaxation time was determined directly using the saturation recovery technique, while the Click to view the MathML source relaxation time was measured via 1H?31P CP by incrementing the 31P spin-lock. In order to avoid an effect of magic-angle spinning (MAS) on CP and relaxation, the experiments were carried out on static samples. The 31P spin–lattice relaxation was discussed for trabecular and cortical bone tissue from adult subjects in comparison to the synthetic mineral standards. None of the reference materials has matched accurately the relaxation behaviour of the bone mineral.
The most striking differences between the examined substances were observed for T1P, which for human bone was sample dependent and appeared in the range 55–100 s, while for HAh, HAc, and CHA-B was 7.2, 10.0, and 25.8 s, respectively. Possible reasons of so large relaxation diversity were discussed. It has been suggested that T1P of apatites is to some extent dependent on the concentration of the structural hydroxyl groups, and this in turn is controlled by the material crystallinity. It was also found that T1P decreased on hydration by ca. 30%.
Keywords: Bone; Mineral; Apatite; 31P NMR; Cross-polarization; Relaxation
Letter to the Editor: Two-dimensional 11B–11B exchange NMR study in mesoporous boron carbon nitride at 21.8 T - doi:10.1016/j.ssnmr.2007.04.003
Miwa Murakami, Tadashi Shimizu, Masataka Tansho, Ajayan Vinu, Katsuhiko Ariga, Toshiyuki Mori and K. Takegoshi
National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003, Japan
National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan