Formation of functional phosphosilicate gels from phytic acid and tetraethyl orthosilicate

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• 作者：Dong Qiu ; Paul Guerry ; Jonathan C. Knowles ; Mark E. Smith and Robert J. Newport
• 关键词：Phosphosilicate ; Sol&#8211 ; gel ; 29Si and 31P NMR ; Calcium absorbing
• 刊名：Journal of Sol-Gel Science and Technology
• 出版年：2008
• 出版时间：December, 2008
• 年：2008
• 卷：48
• 期：3
• 页码：378-383
• 全文大小：507.9 KB

文摘

Phosphosilicate gels with high phosphorus content (P mol % > Si mol % ) have been prepared using phytic acid as the phosphorus precursor, with tetraethyl orthosilicate (TEOS). It is shown that the structure of phytic acid is maintained in both the sols and those gels dried at a low temperature (i.e. ≤120 ¡ãC). Solid state 29Si and 31P NMR suggest that the gel network is primarily based on tetrahedral silicon and that phosphorus is not chemically incorporated into the silicate network at this point. X-ray diffraction shows the gel to be amorphous at low temperatures. After heat treatment at higher temperatures (i.e. up to 450 ¡ãC), P–O–Si linkages are formed and the silicon coordination changes from tetrahedral to octahedral. At the same time, the gel crystallizes. Even after this partial calcination, 31P NMR shows that a large fraction of phytic acid remains in the network. The function of phytic acid as chelating agent is also maintained in the gels dried at 120 ¡ãC such that its ability to absorb Ca2+ from aqueous solution is preserved.