An examination of the calcium and strontium site distribution in bioactive glasses through isomorphic neutron diffraction, X-ray diffraction, EXAFS and multinuclear solid state NMR
An examination of the calcium and strontium site distribution in bioactive glasses through isomorphic neutron diffraction, X-ray diffraction, EXAFS and multinuclear solid state NMR
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DOI：
10.1039/c2jm33058j
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发表时间：
2012-10
影响因子：
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通讯作者：
Richard A. Martin;Helen L. Twyman;Gregory J Rees;E. Barney;R. Moss;Jodie M. Smith;R. Hill;G. Cibin;T. Charpentier;Mark E. Smith;J. Hanna;R. J. Newport
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文献类型：
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作者：
Richard A. Martin;Helen L. Twyman;Gregory J Rees;E. Barney;R. Moss;Jodie M. Smith;R. Hill;G. Cibin;T. Charpentier;Mark E. Smith;J. Hanna;R. J. Newport
在玻璃系列(SiO_2)49.46(Na2O)26.38(P_2O_5)1.07(CaO)23.08−x(SRO)x(其中x=0，11.54，23.08)中，锶已被取代，以阐明其潜在的原子级结构特征，作为理解与生物活性相关的特征的基础。用类质同象中子和X射线衍射、锶K边EXAFS和固态17O、23Na、29Si、31P和43Ca魔角旋转(MAS)核磁共振研究了这些生物活性玻璃。用一个有效的同构取代一阶差分函数对中子衍射数据进行了计算，证实了钙和锶在玻璃网络中的行为相似，残差完全归因于两种物质之间离子半径的变化。衍射数据首次提供了这些熔融猝灭生物活性玻璃中分裂的Ca-O近邻关联的直接实验证据，以及类似的Sr-O关联的分裂；这些关联归因于与桥或非桥氧原子相关的金属离子。三重量子(3Q)~(43)Ca MAS核磁共振证实了分裂的Ca-O关联。通过差分法成功地简化了2<；r(A)<；3区域，也揭示了两个截然不同的Na环境。这些环境归因于与桥联或非桥联氧原子相关的钠。互补多核MAS核磁共振、锶K边EXAFS和X射线衍射谱数据支持所提出的结构模型。存在的结构位置将与它们在血浆和唾液等生理液体中的释放特性密切相关，从而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。
Strontium has been substituted for calcium in the glass series (SiO2)49.46(Na2O)26.38(P2O5)1.07 (CaO)23.08−x(SrO)x (where x = 0, 11.54, 23.08) to elucidate their underlying atomic-scale structural characteristics as a basis for understanding features related to the bioactivity. These bioactive glasses have been investigated using isomorphic neutron and X-ray diffraction, Sr K-edge EXAFS and solid state 17O, 23Na, 29Si, 31P and 43Ca magic-angle-spinning (MAS) NMR. An effective isomorphic substitution first-order difference function has been applied to the neutron diffraction data, confirming that Ca and Sr behave in a similar manner within the glass network, with residual differences attributed to solely the variation in ionic radius between the two species. The diffraction data provides the first direct experimental evidence of split Ca–O nearest-neighbour correlations in these melt-quench bioactive glasses, together with an analogous splitting of the Sr–O correlations; the correlations are attributed to the metal ions correlated either to bridging or to non-bridging oxygen atoms. Triple quantum (3Q) 43Ca MAS NMR corroborates the split Ca–O correlations. Successful simplification of the 2 < r (A) < 3 region via the difference method has also revealed two distinct Na environments. These environments are attributed to sodium correlated either to bridging or to non-bridging oxygen atoms. Complementary multinuclear MAS NMR, Sr K-edge EXAFS and X-ray diffraction data supports the structural model presented. The structural sites present will be intimately related to their release properties in physiological fluids such as plasma and saliva, and hence the bioactivity of the material. Detailed structural knowledge is therefore a prerequisite for optimising material design.