synteses and Characterization of biominerals formed on monolayer organic molecular films

本研究的目的是阐明可能不同于无机过程的生物矿化机制。以聚合的10，12-戊二酸(p-PDA)LB膜为有机模板，碳酸钙为生物矿物，在实验室模拟了生物矿化过程。电子衍射研究发现，羧基在p-PDA膜上呈规则的(伪六方)排列。用CaCO3过饱和溶液浸泡包覆p-PDA膜的二氧化硅基片时，在基片上析出方解石晶体。在场发射型高分辨率扫描电子显微镜中，用电子背散射衍射(EBSD)技术分析了方解石的晶体取向。这一新技术准确地揭示了PDA的聚合方向与方解石晶体取向之间的取向关系。方解石的a轴之一严格地平行于聚合的d…。PDA的更直接，这是通过薄膜的表面裂纹来鉴定的。方解石的c轴必然垂直于聚合方向，但它们的方向(与衬底的站立角度)是不同的。此外，还研究了溶液中稀土元素对碳酸钙晶体形貌的影响。极少量的La^-lt；3-gt；离子对方解石的形态有很大的影响，但对球泡石的形态几乎没有影响。La^-lt；3-gt；还起到了抑制方解石从过饱和溶液中析出的作用。在方解石沉淀和晶体生长过程中，这两种作用必然是密切相关的。此外，EBSD技术还被应用于自然界中的几种生物矿物。特别是成功地确定了球石(球藻鳞片)中方解石晶体的结构与晶体取向的关系。较少

The purpose of the present study is to elucidate the biomineralization mechanisms that are presumably different from those in inorganic processes. Biomineralization was simulated in the laboratory, by selecting polymerized 10,12-Pentacosadiynoic acid(p-PDA)LB films as organic template and calcium carbonate as biominerals. It was found by electron diffraction study that carboxyl groups are regularly (pseudo-hexagonally) arranged on the p-PDA film. When the silica substrates covered with the p-PDA film were soaked in a solution supersaturated with CaCO_3, calcite crystals were precipitated on the substrates. the crystal orientation of the calcite was analyzed by using electron back-scattering diffraction (EBSD) technique in a field-emission type high-resolution SEM. This new technique revealed the orientation relationship between the polymerized direction of PDA and crystal orientation of calcite accurately. One of the a-axes of calcite was strictly oriented parallel to the polymerized d … More irection, which was identified by the surface cracking of the film, of PDA. the c-axis of calcite was necessarily perpendicular to the polymerized direction but their direction (standing angle from the substrate) was varied. Other CaCO_3 polymorphs, aragonite and vaterite, are rarely formed on the film but no epitaxial relations were observed.Besides these experiments, the effects of rare-earth elements in solution on the morphology of calcium carbonate crystals were also investigated. Very small amount of La^<3+> ion changed the shape of calcite drastically, but did not change that of vaterite at all. La^<3+> also acted as an inhibitor against the precipitation of calcite from supersaturated solution. These two effects must be related intimately during calcite precipitation and crystal growth. Furthermore, the EBSD technique was applied to several biominerals in nature. Especially the relationship between the structure and crystal orientations of constituting calcite crystals in coccolith (scale of coccolith algae) was successfully determined. Less