Das Sushanta K, Sengupta Sanghamitra, Velarde Luis
Department of Chemistry, ‡Department of Materials Design and Innovation, University at Buffalo, The State University of New York , Buffalo, New York 14260-3000, United States.
J Phys Chem Lett. 2016 Jan 21;7(2):320-6. doi: 10.1021/acs.jpclett.5b02633. Epub 2016 Jan 7.
The molecular self-assembly of surfactants on the surface of single-walled carbon nanotubes (SWCNT) is currently a common strategy for the tuning of nanotube properties and the stabilization of carbon nanotube dispersions. Here, we report direct measurements of the degree of interfacial ordering for sodium dodecyl sulfate (SDS) surfactants adsorbed on colloidal, single-chirality enriched, SWCNTs within a solid film and investigate the dependence of surface alkyl chain order on the surfactant concentration in the precursor solution. The degree of order for the SWCNT-bound SDS molecules, is probed by vibrational sum frequency generation (VSFG) spectroscopy. We find concrete evidence for the presence of highly ordered surface structures at sufficiently high SDS concentrations, attributed here to cylindrical-like micelle assemblies with the SWCNT at the core. As the SDS concentration decreases, the interfacial order is found to decrease as well, generating a more disordered or random adsorption of surfactants on the nanotube surfaces.
表面活性剂在单壁碳纳米管（SWCNT）表面的分子自组装是目前调节纳米管性能和稳定碳纳米管分散体的常用策略。在此，我们报告了对吸附在固体薄膜中胶体状、单手性富集的SWCNT上的十二烷基硫酸钠（SDS）表面活性剂界面有序度的直接测量，并研究了表面烷基链有序度对前驱体溶液中表面活性剂浓度的依赖性。通过振动和频产生（VSFG）光谱探测与SWCNT结合的SDS分子的有序度。我们发现有确凿证据表明，在足够高的SDS浓度下存在高度有序的表面结构，这里归因于以SWCNT为核心的圆柱状胶束聚集体。随着SDS浓度降低，界面有序度也降低，导致表面活性剂在纳米管表面的吸附更加无序或随机。
