pH、表面电荷和反离子对十二烷基硫酸钠在蓝宝石/溶液界面吸附的影响
Effect of pH, surface charge and counter-ions on the adsorption of sodium dodecyl sulfate to the sapphire/solution interface
摘要：
十二烷基硫酸钠，SDS和蓝宝石表面之间的离子相互作用的作用进行了研究，使用镜面中子反射，以确定吸附的表面活性剂层的结构和组成。将溶液的pH从3增加到9通过逆转氧化铝的电荷来减少吸附。这发生在R-平面（1 - 1 0 2）的pH低于C-平面（0 0 0 1）的pH，对应于不同的零电荷点。最大的表面过量为约6.5 μ mol m-2，吸附层的厚度为约24埃，并且它包含大约20%的水。表面活性剂分子的烃尾明显地相互渗透，而不是形成有序的双层。当表面活性剂处于各自的临界胶束浓度时，该结构在纯水或0.1 M NaCl中是相似的。十二烷基硫酸锂和十二烷基硫酸铯的结构不同。CsDS形成致密层，几乎没有或没有水合作用，表面过量约为10.5 μ mol m-2。金属阳离子强烈影响吸附的表面活性剂的水合作用。观察到了吸附层结构的“扁平胶束”的全貌
英文摘要：
The role of ionic interactions between sodium dodecyl sulfate, SDS, and sapphire surfaces have been studied using specular neutron reflection to determine the structure and composition of adsorbed surfactant layers. Increasing the pH of the solution from 3 to 9 reduces the adsorption by reversing the charge of the alumina. This occurs at lower pH for the R-plane (1 -1 0 2) than the C-plane (0 0 0 1), corresponding to the different points of zero charge. The largest surface excess is about 6.5 micromol m-2, the thickness of the adsorbed layer is about 24 Angstrom and it contains roughly 20% water. The hydrocarbon tails of the surfactant molecules clearly interpenetrate rather than form an ordered bilayer. The structure is similar in either pure water or in 0.1 M NaCl when the surfactant is at the respective critical micelle concentration. Different structures were seen with lithium and cesium dodecyl sulfate. The CsDS forms dense layers with little or no hydration and a surface excess of about 10.5 micromol m-2. The metal cation strongly influences the hydration of the adsorbed surfactant. An overall picture of 'flattened micelles' for the structure of the adsorbed layer is observed
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