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Multinuclear Solid-State NMR Studies of Ordered Mesoporous Bioactive Glasses
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
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2008 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, Vol. 112, no 14, 5552-5562 p.Article in journal (Refereed) Published
Abstract [en]

The local structures of highly ordered mesoporous bioactive CaO-SiO2-P2O5 glasses were investigated for variable Ca contents. 1H NMR revealed a diversity of hydrogen-bonded and "isolated" surface silanols as well as adsorbed water molecules. The structural roles of Si and P were explored using a combination of 29Si and 31P magic-angle spinning (MAS) nuclear magnetic resonance (NMR) techniques; the proximities of Si and P to protons were studied through cross-polarization-based experiments, including 1H-29Si and 1H-31P hetero-nuclear two-dimensional correlation spectroscopy. The results are consistent with SiO2 being the main pore-wall component, whereas P is present as a separate amorphous calcium orthophosphate phase, which is dispersed over the pore wall as nanometer-sized clusters. The excess Ca that is not consumed in the phosphate phase modifies the silica glass network where it associates at/near the mesoporous surface. This biphasic structural model of the pore wall leads to the high accessibility of both Ca and P to body fluids, and its relation to the experimentally demonstrated high in vitro bioactivities of these materials is discussed.

Place, publisher, year, edition, pages
2008. Vol. 112, no 14, 5552-5562 p.
Keyword [en]
Nuclear-Magnetic-Resonance, H-1 MAS NMR, IN-Vitro, Calcium-Phosphate, Gel Glasses, Silica Nanoparticles, Cross-Polarization, Apatite Formation, Spinning NMR, System
URN: urn:nbn:se:su:diva-15705DOI: 10.1021/jp7107973ISI: 000254710800045OAI: diva2:182225
Available from: 2008-12-08 Created: 2008-12-08 Last updated: 2010-01-26Bibliographically approved
In thesis
1. Structural Investigations of Complex Glasses by Solid-state NMR
Open this publication in new window or tab >>Structural Investigations of Complex Glasses by Solid-state NMR
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This PhD thesis presents structural investigations of amorphous inorganic materials: oxide and oxynitride glasses and mesoporous bioactive glasses (MBGs), by solid-state Nuclear Magnetic Resonance (NMR).

Lanthanum oxide and oxynitride [La-Si-(Al)-O-(N)] glasses have a large number of potential applications due to their physical properties. In our work we have studied, compared to previous investigations, significantly expanded ranges of glass compositions (for oxynitride glasses, including samples of very high nitrogen content, up to 53 % out of the anions). We have estimated local environments of 29Si and 27Al structural units (their coordination, polymerization degree and number of N incorporated into tetrahedral units) in the materials. We have suggested a random Al/Si distribution along with almost uniform non-bridging oxygen atoms distribution in aluminosilicate glasses.

Silicon nitride was used as precursor in the oxynitride glass synthesis. We studied both α- and β-modifications of silicon nitride, 15N-enriched, as well as fully (29Si, 15N)-enriched samples. We have shown that the linewidths of 15N NMR spectra are dominated by J(29Si-15N) coupling in 29Si315N4 sample.

Mesoporous bioactive glasses in the CaO-SiO2-P2O5 system show superior bioactivity (the ability to form a hydroxycarbonate apatite layer on the glass surface when exposed to body fluids) compared to conventional bioactive glasses due to their large surface area and uniform pore-size distribution. Previous studies suggested a homogeneous cation distribution over the MBG samples on a 10−20 nm length-scale. From our results, on the other hand, we may conclude that Si and P is not intimately mixed. We propose a structural model, in which the pore walls of MBGs are composed of a silica network, and a phosphate phase is present as nanometer-sized clusters that are dispersed on the pore wall.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2009. 62 p.
glass, glass structure and properties, NMR, magic angle spinning, chemical shift
National Category
Physical Chemistry
Research subject
Physical Chemistry
urn:nbn:se:su:diva-8565 (URN)978-91-7155-816-9 (ISBN)
Public defence
2009-03-19, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 10:00 (English)
Available from: 2009-02-26 Created: 2009-02-18 Last updated: 2010-01-26Bibliographically approved

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Edén, MattiasHedin, Niklas
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