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Characterization of sol-gel bioglasses with the use of simple model systems: a surface-chemistry approach

机译:使用简单模型系统表征溶胶-凝胶生物玻璃:表面化学方法

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The present work deals with the physico-chemical characterization of the surface features of two powdery sol gel-synthesized bioglass specimens (58S and 77S) employed in repair of human bones and soft tissues. In-situ transmission FTIR spectroscopy and adsorption microcalorimetry (with the use of water as a probe molecule) were adopted in parallel to study on one hand bioglasses (amorphous Si, Ca and P oxides) and on the other hand pure and doped silica specimens, as reference materials. It was observed that the presence of Ca and P moieties induces the formation of surface sites that possess higher strength and higher capability towards water coordination than do the hydroxy groups present on pure silica. In particular, the presence of some irreversibly coordinated water was observed both on these bioglasses and on doped silica. The Ca/P ratio seems to play a major role: (i) an excess of Ca induces the presence of coordinatively unsaturated surface (cus) Ca2+ ions, that generate Lewis acid sites that can strongly interact with water and can yield surface carbonates; (ii) the presence of P species increases the surface hydrophilic character and leads to the formation of Si-O-P labile bridges, which exhibit an enhanced propensity to dissociate water. [References: 26]
机译:本工作涉及两个粉末状溶胶凝胶合成的生物玻璃样品(58S和77S)的表面特征的物理化学表征,该样品用于修复人体骨骼和软组织。并行采用原位透射FTIR光谱和吸附微量量热法(以水作为探针分子)研究一方面是生物玻璃(非晶态的Si,Ca和P氧化物),另一方面是纯净和掺杂的二氧化硅样品,作为参考资料。观察到,Ca和P部分的存在诱导了表面部位的形成,该表面部位具有比纯二氧化硅上存在的羟基更高的强度和更高的水配位能力。特别地,在这些生物玻璃和掺杂的二氧化硅上均观察到一些不可逆配位的水的存在。 Ca / P比似乎起主要作用:(i)过量的Ca导致存在配位不饱和表面Ca 2+离子,该离子产生路易斯酸位点,该位点可与水强烈相互作用并产生表面碳酸盐; (ii)P物种的存在增加了表面亲水性,并导致形成Si-O-P不稳定桥,这些桥表现出更高的分解水的倾向。 [参考:26]

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