Institute of Advanced Materials and Processes (ZMP), University of Erlangen-Nuremberg, Dr. Mack Straße 81, 90762 Fuerth, Germany.
Chemistry. 2010 Nov 22;16(44):13185-92. doi: 10.1002/chem.201000232.
We present evidence from multiple characterization methods, such as emission spectroscopy, zeta potential, and analytical ultracentrifugation, to shed light on the adsorption behavior of synthesized perylene surfactants on single-walled carbon nanotubes (SWCNTs). On comparing dispersions of smaller-diameter SWCNTs prepared by using cobalt-molybdenum catalysis (CoMoCAT) with the larger-diameter SWCNTs prepared by high-pressure carbon monoxide decomposition (HiPco), we find that the CoMoCAT-perylene surfactant dispersions are characterized by more negative zeta potentials, and higher anhydrous specific volumes (the latter determined from the sedimentation coefficients by analytical ultracentrifugation), which indicates an increased packing density of the perylene surfactants on nanotubes of smaller diameter. This conclusion is further supported by the subsequent replacement of the perylene derivatives from the nanotube sidewall by sodium dodecyl benzene sulfonate (SDBS), which first occurs on the larger-diameter nanotubes. The enhanced adsorption affinity of the perylene surfactants towards smaller-diameter SWCNTs can be understood in terms of a change in the supramolecular arrangement of the perylene derivatives on the scaffold of the SWCNTs. These findings represent a significant step forward in understanding the noncovalent interaction of π-surfactants with carbon nanotubes, which will enable the design of novel surfactants with enhanced selectivity for certain nanotube species.
我们采用多种表征方法,如发射光谱、动电电位和分析超速离心等,提供证据说明合成的苝表面活性剂在单壁碳纳米管(SWCNTs)上的吸附行为。在比较使用钴-钼催化(CoMoCAT)制备的较小直径 SWCNTs 与高压一氧化碳分解(HiPco)制备的较大直径 SWCNTs 的分散体时,我们发现 CoMoCAT-苝表面活性剂分散体具有更负的动电电位和更高的无水比容(后者通过分析超速离心从沉降系数确定),这表明苝表面活性剂在较小直径的纳米管上的堆积密度增加。随后用十二烷基苯磺酸钠(SDBS)从纳米管侧壁取代苝衍生物,这首先发生在较大直径的纳米管上,这进一步证实了这一结论。苝表面活性剂对较小直径 SWCNTs 的吸附亲和力增强,可以用苝衍生物在 SWCNTs 支架上的超分子排列变化来解释。这些发现代表了在理解π-表面活性剂与碳纳米管的非共价相互作用方面向前迈出的重要一步,这将使设计对某些纳米管具有增强选择性的新型表面活性剂成为可能。