Surface structure of organoclays as examined by X-ray photoelectron spectroscopy and molecular dynamics simulations
Surface structure of organoclays as examined by X-ray photoelectron spectroscopy and molecular dynamics simulations
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DOI：
10.1180/claymin.2015.050.3.08
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发表时间：
2015-08
期刊：
影响因子：
1.5
通讯作者：
B. Schampera;R. Šolc;S. Woche;R. Mikutta;S. Dultz;G. Guggenberger;D. Tunega
中科院分区：
文献类型：
--
作者：
B. Schampera;R. Šolc;S. Woche;R. Mikutta;S. Dultz;G. Guggenberger;D. Tunega
有机粘土是以粘土为原料，通过无机阳离子与有机阳离子交换制备的吸附材料。它们的性质取决于有机阳离子的负载和构象结构，但关于有机粘土的表面结构的信息很少。在这项工作中，x射线光电子能谱（XPS）和经典分子动力学（MD）模拟相结合，表征了十六烷基吡啶（HDPy+）和膨润土制备的有机粘土的外部界面。XPS调查光谱显示，随着表面活性剂用量的增加，表面元素组成发生变化，随着有机覆盖度的增加，土源元素的贡献减小。高分辨率c1s XPS光谱灵敏地描绘了表面活性剂的表面排列。结合MD模拟，结果表明表面活性剂覆盖率低时为单层涂层，表面活性剂吸收率高时为无序双层涂层。分子动力学模拟表明，对于非常高的阳离子摄取，类石蜡结构也是可能的。实验和模拟相结合的方法获得了有机粘土表面有机阳离子的分子尺度排列及其控制机制的一致信息。
Abstract Organoclays are sorbent materials prepared from clays by exchanging inorganic with organic cations. Their properties depend on the loading and conformational structure of the organic cations, but little information is available about the surface structures of organoclays. In this work, X-ray photoelectron spectroscopy (XPS) and classical molecular dynamics (MD) simulations are combined to characterize the external interface of an organoclay prepared from hexadecylpyridinium (HDPy+) and bentonite. The XPS survey spectra show well the varying elemental composition of the surface with increasing amount of surfactant, showing a decreasing contribution of clay-derived elements with increasing organic coverage. The high-resolution C 1s XPS spectra depict sensitively the surface arrangement of the surfactant. In combination with MD simulations, the results implied a monolayer coating for low surfactant coverage and a disordered bilayer arrangement at high surfactant uptakes. Molecular dynamics simulations showed that for very high cation uptake a quasi-paraffin-like configuration is also possible. The combination of experimental and modelling methods yielded congruent information on the molecular-scale arrangement of organic cations at the organoclay surfaces and the controlling mechanisms.