Department of Chemistry, Yonsei University, Seoul 120-749, South Korea.
Langmuir. 2013 Sep 3;29(35):11154-62. doi: 10.1021/la4022933. Epub 2013 Aug 19.
Binding affinity and thermodynamic understanding between a surfactant and carbon nanotube is essential to develop various carbon nanotube applications. Flavin mononucleotide-wrapped carbon nanotubes showing a large redshift in optical signature were utilized to determine the binding affinity and related thermodynamic parameters of 12 different nanotube chiralities upon exchange with other surfactants. Determined from the midpoint of sigmoidal transition, the equilibrium constant (K), which is inversely proportional to the binding affinity of the initial surfactant-carbon nanotube, provided quantitative binding strengths of surfactants as SDBS > SC ≈ FMN > SDS, irrespective of electronic types of SWNTs. Binding affinity of metallic tubes is weaker than that of semiconducting tubes. The complex K patterns from semiconducting tubes show preference to certain SWNT chiralities and surfactant-specific cooperativity according to nanotube chirality. Controlling temperature was effective to modulate K values by 30% and enables us to probe thermodynamic parameters. Equally signed enthalpy and entropy changes produce Gibbs energy changes with a magnitude of a few kJ/mol. A greater negative Gibbs energy upon exchange of surfactant produces an enhanced nanotube photoluminescence, implying the importance of understanding thermodynamics for designing nanotube separation and supramolecular assembly of surfactant.
表面活性剂与碳纳米管之间的结合亲和力和热力学理解对于开发各种碳纳米管应用至关重要。利用黄素单核苷酸包裹的碳纳米管在光学特征上表现出较大的红移，来确定在与其他表面活性剂交换时 12 种不同手性的碳纳米管的结合亲和力和相关热力学参数。根据 S 形跃迁的中点确定平衡常数（K），它与初始表面活性剂-碳纳米管的结合亲和力成反比，提供了表面活性剂的定量结合强度，SDBS>SC≈FMN>SDS，与 SWNTs 的电子类型无关。金属管的结合亲和力比半导体管弱。根据碳纳米管的手性，来自半导体管的复杂 K 模式显示出对某些 SWNT 手性和表面活性剂特定协同作用的偏好。控制温度可有效调节 K 值 30%，使我们能够探测热力学参数。等号的焓和熵变化产生吉布斯能量变化，幅度为几 kJ/mol。表面活性剂交换产生更大的负吉布斯能量会增强碳纳米管的光致发光，这意味着理解热力学对于设计碳纳米管分离和表面活性剂的超分子组装非常重要。
