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Materials
Structure and Function 
Chris
Ratcliffe (Program Leader)
Opportunities for studying polymorphs and cement-based materials via Ca-43 solid-state NMR
June 11, 2010, University of Ottawa
Calcium is an important component in diverse materials and biochemicals. However, NMR spectroscopy of the only spin-active calcium isotope, Ca-43, is notoriously challenging due to its low natural abundance (0.14 %), low resonance frequency, and quadrupolar nature. Recently, researchers from the University of Ottawa, the NRC Steacie Institute for Molecular Sciences (SIMS-NRC), and Dalhousie University have independently reported advances in studies of inorganic polymorphs and cement-based materials using Ca-43 solid-state NMR spectroscopy.
"In spite of the great complexity of the calcium silicate chemistry involved in the hydration of Portland cement, we have shown that Ca-43 solid-state NMR provides useful new insights into cement chemistry", says Igor Moudrakovski (SIMS-NRC) of his collaboration with the Institute for Research in Construction (SIMS-IRC). Josef Zwanziger (Dalhousie) and his academic and industrial partners have similarly applied Ca-43 NMR in their project on the development, optimization and commercialization of high performance cement based composite materials.
Zwanziger explains, "we are trying to understand the nature of the composite-cement interface, and the mechanisms of toughening and strengthening in concrete composites. Calcium NMR is one of the many tools which is shedding light on the nature of the interface." At the University of Ottawa, David Bryce and his research group have demonstrated the utility of calcium NMR in understanding polymorphism in solids. This work has implications for understanding biomaterials as well as inorganic materials.
Because Ca-43 NMR in solid state requires a very strong magnetic field for sensitivity reasons, all these experiments were carried out at the National Ultrahigh-Field NMR Facility for Solids, a national user facility managed by the University of Ottawa and housed on NRC's Ottawa campus, which houses Canada's only 21.1 T (900 MHz) NMR spectrometer.
The latest calcium NMR research has been published in PCCP and J. Am. Chem. Soc., and a perspective on the state of the field is now available in Dalton Transactions (Bryce, 2010).
David L. Bryce "Calcium Binding Environments Probed by 43Ca NMR Spectroscopy," Dalton Transactions (2010) online. http://dx.doi.org/10.1039/c0dt00416b
Igor
Moudrakovski, Rouhollah Alizadeh, James J. Beaudoin, "Natural abundance
high field 43Ca solid state NMR in cement science," Physical Chemistry
Chemical Physics 12 (2010) 6961-6969. http://dx.doi.org/10.1039/c000353k
David L. Bryce, Elijah B. Bultz, and Dominic Aebi, "Calcium-43 Chemical Shift Tensors as Probes of Calcium Binding Environments. Insight into the Structure of the Vaterite CaCO3 Polymorph by 43Ca Solid-State NMR Spectroscopy," Journal of the American Chemical Society 130 (2008) 9282–9292. http://dx.doi.org/10.1021/ja8017253
 |
A
research team from the University of Calgary and the NRC
Steacie Institute for Molecular Sciences (Ottawa) has published
a cover article in Nature Chemistry |
"Materials
built from metal centres and organic ligands have traditionally attracted
attention for their channels' host–guest properties. Now, controlling
the occupancy of the channels by guest molecules has resulted in a framework
that conducts protons under anhydrous conditions and acts as a gas-tight membrane,
offering a promising approach to fuel-cell electrolytes."
Solid-state NMR spectroscopy was instrumental in this research.
The paper is also accompanied by the Nature's commentary:
Hiroshi Kitagawa, "Metal–organic frameworks: Transported into fuel cells," Nature Chemistry 1 (2009) 689-690. http://dx.doi.org/10.1038/nchem.454
 |
Unique instrumentation available at the 900 NMR Facility allows our users to deal with systems and nuclei inaccessible before with NMR at lower fields. One example is 73Ge NMR in solids which was previously limited only to highly symmetric environments. In this cover article just published by Chemical Communications a research team from the University of Manitoba and NRC-SIMS is reporting natural abundance 73Ge NMR spectra in much more challenging amorphous and crystalline germanium oxides. Work continues on even more complex glasses and crystalline phases to address long-standing fundamental questions in glass science, such as the ‘‘germanate anomaly’’. |
Vladimir K. Michaelis, Pedro M. Aguiar, Victor V. Terskikh and Scott Kroeker, "Germanium-73 NMR of Amorphous and Crystalline GeO2," Chemical Communications (2009) 4660-4662. (Cover Article) http://dx.doi.org/10.1039/b906642j
A special issue of Physical Chemistry Chemical Physics on modern aspects of Electron Paramagnetic Resonance (EPR) has been finalized and is now available online (external link). This PCCP issue brings together a broad range of manuscripts dealing with novel EPR applications, new methodologies and advances in data analysis. It will be displayed at the upcoming 7th European Federation of EPR Groups conference in Antwerp, Belgium in early September 2009. http://www.efepr2009.ua.ac.be/
Canadian contribution in this issue is by our colleagues from the NRC Steacie Institute for Molecular Sciences collaborating with fellow EPR spectoscopists from Russia, Germany, and France.
E.G. Bagryanskaya, D.N. Polovyanenko, M.V. Fedin, L.Kulik, A. Schnegg, A. Savitsky, K. Möbius, A.W. Coleman, G.S. Ananchenko and J.A. Ripmeester, "Multifrequency EPR study of the mobility of nitroxides in solid-state calixarene nanocapsules," Physical Chemistry Chemical Physics 11 (2009) 6700–6707. http://dx.doi.org/10.1039/b906827a
A
research team from the Steacie Institute for Molecular Sciences (NRC
Canada) and their colleagues from Oak Ridge, Stony-Brook, and Argonne, are
reporting synthesis and characterization of a new structure of gas hydrate,
previously known only hypothetically. Static and magic angle spinning 129Xe
NMR was instrumental in this research, and had provided strong confirmation
of the structural analysis.
L. Yang, C.A. Tulk, D.D. Klug, I.L. Moudrakovski, C.I. Ratcliffe, J.A. Ripmeester, B.C. Chakoumakos, L. Ehm, C.D. Martin, and J.B. Parise, "Synthesis and characterization of a new structure of gas hydrate," Proc. Natl. Acad. Sci. USA 106 (2009) online. http://dx.doi.org/10.1073/pnas.0809342106
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