Directly probing surfactant adsorption on nanoscopic trenches and pillars.
Directly probing surfactant adsorption on nanoscopic trenches and pillars.
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DOI：
10.1016/j.jcis.2020.06.020
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发表时间：
2020-06
影响因子：
9.9
通讯作者：
J. J. Hamon-J.;R. Tabor;A. Striolo;B. Grady
中科院分区：
文献类型：
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作者：
J. J. Hamon-J.;R. Tabor;A. Striolo;B. Grady
实验将十四烷基三甲基溴化铵(TTAB)和氯化十六烷基吡啶(CPC)两种阳离子表面活性剂吸附在硅胶-水界面上。在50 nm和80 nm宽的沟槽上测量了原子力显微镜(AFM)的力曲线。还测量了硅胶柱上的力曲线，并根据距离边缘的距离对结果进行了量化。发现沟槽：50 nm和80 nm沟槽中吸附的表面活性物质膜具有相同的穿透值。然而，与非限制值相比，TTAB在沟槽中的穿透和粘附力降低，而CPC在沟槽中的穿透和粘附力增加，这表明表面活性剂的同一性改变了限制效果。柱子：靠近边缘的表面活性剂吸附很少，那些沿垂直于表面的方向延伸的表面活性剂。虽然实验数据与以前的粗粒度分子动力学模拟定性一致，但检测到这些现象的长度尺度相差约半个数量级。具体地说，实验数据显示，在考虑到~8纳米的探针尺寸后，在与表面活性剂分子长度10-20倍的边缘的距离处，对吸附的表面活性剂形态的影响是可测量的。
HypothesisConfinement causes a change in the amount of surfactant adsorbed and in the adsorption morphology.ExperimentsTwo cationic surfactants, tetradecyltrimethylammonium bromide (TTAB) and cetylpyridinium chloride (CPC) were adsorbed at the silica-water interface. Atomic force microscopy (AFM) force curves were measured on 50 nm and 80 nm wide trenches. Force curves were also measured on silica pillars, and the results were quantified based on distance from the edge.FindingsTrenches: Adsorbed surfactants films in 50 nm and 80 nm trenches showed the same break-through values. However, compared to unconfined values, TTAB in trenches had decreased break-through and adhesion forces while CPC in trenches had increased break-through and adhesion forces, indicating that surfactant identity varies the confinement effect.Pillars: Near the edge, few surfactants adsorb, and those that do extend in the direction normal to the surface. While the experimental data agree qualitatively with previous coarse-grained molecular dynamic simulations, the length scales at which the phenomena are detected differ by ~ half-order of magnitude. Specifically, experimental data show measurable effects on adsorbed surfactant morphology at a distance from the edge 10–20 times the length of a surfactant molecule after accounting for the ~8 nm size of the probe.