Atomic-scale surface roughness of rutile and implications for organic molecule adsorption.
Atomic-scale surface roughness of rutile and implications for organic molecule adsorption.
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DOI：
10.1021/la4005328
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发表时间：
2013-05
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影响因子：
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通讯作者：
K. Livi;B. Schaffer;D. Azzolini;C. Seabourne;T. Hardcastle;A. Scott;R. Hazen;J. Erlebacher;R. Brydson;D. Sverjensky
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作者：
K. Livi;B. Schaffer;D. Azzolini;C. Seabourne;T. Hardcastle;A. Scott;R. Hazen;J. Erlebacher;R. Brydson;D. Sverjensky
水晶表面提供了地质圈和生物圈之间的物理界面。因此，原子在晶体表面的排列在许多层面上深刻地影响着生物成分，从细胞到生物聚合物再到单个有机分子。许多研究都集中在利用大而平坦的单晶研究水中的晶体-分子界面。然而，人们对纳米到微米级简单金属氧化物晶体的原子尺度表面结构知之甚少，这些晶体通常用于与生物地球化学和生命起源相关的条件下的批量吸附实验。在这里，我们展示了原子分辨率显微镜数据，以及以前用于研究质子、阳离子和氨基酸吸附的纳米金红石(α-Ti02)晶体的周长的前所未有的详细信息。数据表明，单个晶体上最大的{110}面中，有三分之一是由原子尺度的台阶组成的。这些步骤的取向是为氨基酸的吸附提供类型和丰度较低的配位不足的钛原子，这是从先前的批量吸附数据的表面络合模型推断的。出现了非常均匀的阶梯比例模式：阶梯比例与表面粗糙度无关，并反映了它们的相对表面能量。因此，在扫描电子显微镜图像的粗略尺度上成像的金红石纳米到微米尺寸的晶体的外部形态并不能准确地指示原子的平整度或存在的步骤的比例。总体而言，我们的数据强烈表明，氨基酸在这些步骤上附着在金红石的{110}表面。
Crystal surfaces provide physical interfaces between the geosphere and biosphere. It follows that the arrangement of atoms at the surfaces of crystals profoundly influences biological components at many levels, from cells through biopolymers to single organic molecules. Many studies have focused on the crystal-molecule interface in water using large, flat single crystals. However, little is known about atomic-scale surface structures of the nanometer- to micrometer-sized crystals of simple metal oxides typically used in batch adsorption experiments under conditions relevant to biogeochemistry and the origins of life. Here, we present atomic-resolution microscopy data with unprecedented detail of the circumferences of nanosized rutile (α-TiO2) crystals previously used in studies of the adsorption of protons, cations, and amino acids. The data suggest that one-third of the {110} faces, the largest faces on individual crystals, consist of steps at the atomic scale. The steps have the orientation to provide undercoordinated Ti atoms of the type and abundance for adsorption of amino acids as inferred from previous surface complexation modeling of batch adsorption data. A remarkably uniform pattern of step proportions emerges: the step proportions are independent of surface roughness and reflect their relative surface energies. Consequently, the external morphology of rutile nanometer- to micrometer-sized crystals imaged at the coarse scale of scanning electron microscope images is not an accurate indicator of the atomic smoothness or of the proportions of the steps present. Overall, our data strongly suggest that amino acids attach at these steps on the {110} surfaces of rutile.