Sims Christopher M, Fagan Jeffrey A
Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD USA 20899.
J Phys Chem C Nanomater Interfaces. 2024;128(31). doi: 10.1021/acs.jpcc.4c02568.
A combination of analytical ultracentrifugation (AUC) and fluorescence spectroscopy are utilized to orthogonally probe compositions of adsorbed surfactant layers on the surface of (7,5) species single-wall carbon nanotubes (SWCNTs) under conditions known to achieve differential partitioning in aqueous two-phase extraction (ATPE) separations. Fluorescence emission intensity and AUC anhydrous particle density measurements independently probe and can discriminate between adsorbed surfactant layers on a (7,5) nanotube comprised of either of two common nanotube dispersants, the anionic surfactants sodium deoxycholate and sodium dodecyl sulfate. Measurements on dispersions containing mixtures of both surfactants indicate near total direct exchange of the dominant surfactant species adsorbed to the carbon nanotube at a critical concentration ratio consistent with the ratio leading to partitioning change in the ATPE separation. By conducting these orthogonal measurements in a complex environment reflective of an ATPE separation, including multiple surfactant and polymer solution components, the results provide direct evidence for the hypothesis that it is the nature of the adsorbed surfactant layer that primarily controls partitioning behavior in selective ATPE separations of SWCNTs.
在已知可实现水相双相萃取（ATPE）分离中差异分配的条件下，采用分析超速离心法（AUC）和荧光光谱法相结合的方式，正交探测（7,5）型单壁碳纳米管（SWCNT）表面吸附的表面活性剂层的组成。荧光发射强度和AUC无水颗粒密度测量可独立探测，并能区分由两种常见纳米管分散剂（阴离子表面活性剂脱氧胆酸钠和十二烷基硫酸钠）之一组成的（7,5）纳米管上吸附的表面活性剂层。对含有两种表面活性剂混合物的分散体的测量表明，在与导致ATPE分离中分配变化的比例一致的临界浓度比下，吸附在碳纳米管上的主要表面活性剂物种几乎完全直接交换。通过在反映ATPE分离的复杂环境中进行这些正交测量，包括多种表面活性剂和聚合物溶液成分，结果为以下假设提供了直接证据：在SWCNT的选择性ATPE分离中，主要控制分配行为的是吸附的表面活性剂层的性质。
