A structural investigation of the alkali metal site distribution within bioactive glass using neutron diffraction and multinuclear solid state NMR.
A structural investigation of the alkali metal site distribution within bioactive glass using neutron diffraction and multinuclear solid state NMR.
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DOI：
10.1039/c2cp41725a
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发表时间：
2012-08
期刊：
影响因子：
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通讯作者：
Richard A. Martin;Helen L. Twyman;Gregory J Rees;Jodie M. Smith;E. Barney;Mark E. Smith;J. Hanna;R. J. Newport
中科院分区：
文献类型：
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作者：
Richard A. Martin;Helen L. Twyman;Gregory J Rees;Jodie M. Smith;E. Barney;Mark E. Smith;J. Hanna;R. J. Newport
利用中子衍射和固体魔角自旋（MAS）核磁共振研究了生物玻璃的原子尺度结构和锂取代钠在这些玻璃中的作用。应用一个有效的同构替代差函数的中子衍射数据，使Na-O和Li-O的最近邻关联从重叠的Ca-O，O-（P）-O和O-（Si）-O的关联中分离出来。这些结果表明，钠和锂的行为在玻璃基质内以类似的方式，不破坏网络前的短程有序。残余差异仅归因于两个物种之间的离子半径的变化。通过差分方法成功地简化了2 < r（λ）< 3区域，使得所有最近邻相关性都能够被去卷积。的衍射数据提供了第一个直接的实验证据分裂钠-O最近邻的相关性在这些熔体淬火生物活性玻璃，和类似的分裂的锂-O的相关性。所观察到的相关性归因于金属离子键合到桥接或非桥接氧原子。（23）Na三量子MAS（3QMAS）NMR数据证实了分裂的Na-O相关性。存在的结构位点将与玻璃系统在生理流体如血浆和唾液中的释放性质密切相关，因此与材料的生物活性密切相关。因此，详细的结构知识是优化材料设计的先决条件。
The atomic-scale structure of Bioglass and the effect of substituting lithium for sodium within these glasses have been investigated using neutron diffraction and solid state magic angle spinning (MAS) NMR. Applying an effective isomorphic substitution difference function to the neutron diffraction data has enabled the Na-O and Li-O nearest-neighbour correlations to be isolated from the overlapping Ca-O, O-(P)-O and O-(Si)-O correlations. These results reveal that Na and Li behave in a similar manner within the glassy matrix and do not disrupt the short range order of the network former. Residual differences are attributed solely to the variation in ionic radius between the two species. Successful simplification of the 2 < r (Å) < 3 region via the difference method has enabled all the nearest neighbour correlations to be deconvolved. The diffraction data provides the first direct experimental evidence of split Na-O nearest-neighbour correlations in these melt quench bioactive glasses, and an analogous splitting of the Li-O correlations. The observed correlations are attributed to the metal ions bonded either to bridging or to non-bridging oxygen atoms. (23)Na triple quantum MAS (3QMAS) NMR data corroborates the split Na-O correlations. The structural sites present will be intimately related to the release properties of the glass system in physiological fluids such as plasma and saliva, and hence to the bioactivity of the material. Detailed structural knowledge is therefore a prerequisite for optimizing material design.