Assembling structures and dynamics properties of perfluorooctane sulfonate (PFOS) at water-titanium oxide interfaces.
Assembling structures and dynamics properties of perfluorooctane sulfonate (PFOS) at water-titanium oxide interfaces.
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DOI：
10.1016/j.jcis.2013.05.003
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发表时间：
2013-09
影响因子：
9.9
通讯作者：
G. He;G. Pan;Meiyi Zhang
中科院分区：
文献类型：
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作者：
G. He;G. Pan;Meiyi Zhang
通过分子动力学（MD）模拟确定了全氟辛烷磺酸（PFOS）在水-金红石tio2界面上的表面相关结构和生长模式。结果表明，在金红石表面形成了致密的全氟辛烷磺酸层，其组装结构和动态分布与晶面有关。全氟辛烷磺酸分子主要通过磺酸基团附着在（110）和（001）表面。在（110）表面形成了一个定义明确的单层，全氟烷基链几乎垂直于底物，而C-F链则倾斜成一个角度（30-75°），并在（001）表面形成半圆柱形结构。另一方面，全氟两亲体通过磺酸盐头基（相对强的静电吸引力）和C-F尾基（弱范德华力）与（100）平面相互作用，产生不规则的组装模式。水分子大多集中在离固体表面17.0Å以上的地方，形成了一个连续的溶剂层，这表明全氟烷基链具有超疏水性。在分子尺度上观察到表面活性剂吸附的反离子桥接机制，其中磺酸盐头基团通过表面的钾离子连接在一起并形成表面聚集体。
The surface-associated structures and growth modes of perfluorooctane sulfonate (PFOS) at water–rutile TiO2interfaces were defined by molecular dynamics (MD) simulations. The results showed that a compact PFOS layer was generated at the rutile surfaces, and the assembling structures and dynamic profiles were crystal-face-dependent. PFOS molecules were attached to the (110) and (001) surfaces mainly by the sulfonate headgroups. A well-defined monolayer was formed on the (110) surface with the perfluorinated alkyl chains nearly perpendicular to the substrate, whereas the C–F chains were inclined at an angle (30–75°) and formed a hemicylinder-like configuration on the (001) surface. On the other hand, the perfluorinated amphiphiles interacted with the (100) plane through both the sulfonate headgroups (relatively strong electrostatic attraction) and the C–F tailgroups (weak van der Waals forces) and yielded an irregular assembling pattern. Water molecules were mostly concentrated more than 17.0Å away from the solid surfaces and formed a continuous solvent layer, suggesting the super hydrophobicity of perfluorinated alkyl chains. A counterion-bridging mechanism suggested in surfactant adsorption was observed at the molecular scale, where the sulfonate headgroups were linked together by the potassium ions at the surfaces and caused the formation of surface aggregates.