Lustig Steven Raymond, Jagota Anand, Khripin Constantine, Zheng Ming
DuPont, Central Research and Development, Experimental Station, Route 141, Wilmington, Delaware 19880-0356, USA.
J Phys Chem B. 2005 Feb 24;109(7):2559-66. doi: 10.1021/jp0452913.
Single-stranded DNA wrap helically around individual single-walled carbon nanotubes to form DNA/CNT hybrids, which are both stable and dispersible in aqueous solution. Subjected to ion-exchange chromatography, a hybrid elutes at an ionic strength that depends on the electronic character and diameter of the core nanotube, thus providing a mechanism for separating nanotubes by chirality. We present a theoretical model for this separation process that explains all the salient features observed experimentally to date, and provides accurate predictions for critical elution salt concentration. The competition between adsorption on the stationary phase and counterion condensation in the mobile phase is characterized by estimating the difference in free energy between the two states of the hybrid. Parametric study of the DNA wrapping geometry, SWNT dielectric properties, hybrid length, and diameter indicate that the elution is most sensitive to the hybrid's effective charge density, primarily governed by the DNA helical pitch. The model correctly predicts hybrids with metallic nanotubes are weaker binding than hybrids with semiconducting nanotubes and larger diameter nanotubes are eluted at later times.
单链DNA螺旋缠绕在单个单壁碳纳米管周围，形成DNA/碳纳米管杂化物，该杂化物在水溶液中既稳定又可分散。经过离子交换色谱法，杂化物在取决于核心纳米管电子特性和直径的离子强度下洗脱，从而提供了一种按手性分离纳米管的机制。我们提出了一个用于此分离过程的理论模型，该模型解释了迄今为止实验观察到的所有显著特征，并对临界洗脱盐浓度提供了准确预测。通过估计杂化物两种状态之间的自由能差异来表征固定相上的吸附与流动相中抗衡离子凝聚之间的竞争。对DNA缠绕几何结构、单壁碳纳米管介电特性、杂化物长度和直径的参数研究表明，洗脱对杂化物的有效电荷密度最为敏感，主要由DNA螺旋螺距决定。该模型正确预测了与金属纳米管形成的杂化物比与半导体纳米管形成的杂化物结合力弱，且直径较大的纳米管在较晚时间洗脱。
