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通过非共价功能化实现碳纳米管的溶解。从海藻酸钠可逆包裹单壁碳纳米管中获得的启示。

Solubilizing carbon nanotubes through noncovalent functionalization. Insight from the reversible wrapping of alginic acid around a single-walled carbon nanotube.

机构信息

College of Chemistry, Nankai University, Tianjin, 300071, P.R. China.

出版信息

J Phys Chem B. 2010 May 6;114(17):5783-9. doi: 10.1021/jp9110772.

Abstract

Carbon nanotubes coated with alginic acid (AA) through noncovalent functionalization have been shown to be soluble and dispersed in water. In the present contribution, all-atom molecular dynamics simulations have been performed to probe the self-assembly mechanism that underlies the formation of complexes by AA and a single-walled carbon nanotube (SWCNT), both in the gas phase and in an aqueous solution. Results of these simulations reveal that AA can wrap around SWCNT by virtue of van der Waals attractions and organize into a compact helical structure, a process induced in the gas phase by hydrogen-bonding interactions. In contrast, in an alginate aqueous solution, a loose helical wrapping mode is found to be favored by virtue of electrostatic repulsions in conjunction with the weakening of hydrogen-bonding interactions. Documented experimentally (Liu, Y.; et al. Small 2006, 2, 874-878) and coined "Great Wall of China" motif, the typical arrangement of AA residues around the tubular structure, conducive to dissolve nanotubes, is observed in the present simulations. Investigation of metal cations binding to AA suggests that calcium ions can mediate aggregation of AA chains by interacting strongly with the carboxylate groups, thereby leading to reverse unwrapping. The results reported in this work shed meaningful light on the potential of noncovalent functionalization for solubilizing carbon nanotubes, and open exciting perspectives for the design of new wrapping agents that are envisioned to form the basis of innovative nanomaterials targeted at chemical and biomedical applications.

摘要

通过非共价功能化在碳纳米管表面包覆海藻酸钠(AA),可以使其在水中溶解和分散。在本研究中,通过全原子分子动力学模拟,研究了 AA 与单壁碳纳米管(SWCNT)在气相和水溶液中形成复合物的自组装机制。模拟结果表明,AA 可以通过范德华吸引力缠绕在 SWCNT 周围,并通过氢键相互作用在气相中形成紧凑的螺旋结构。相比之下,在藻酸盐水溶液中,由于静电排斥和氢键相互作用的减弱,松散的螺旋缠绕模式更占优势。实验中观察到(Liu,Y.;等人。Small 2006,2,874-878)并命名为“中国长城”模式,即 AA 残基在管状结构周围的典型排列,有利于溶解纳米管,这在本模拟中得到了证实。对金属阳离子与 AA 结合的研究表明,钙离子可以通过与羧酸盐基团的强烈相互作用来介导 AA 链的聚集,从而导致反向解缠绕。本工作的研究结果为非共价功能化溶解碳纳米管的潜力提供了有意义的启示,并为设计新的缠绕剂开辟了令人兴奋的前景,这些缠绕剂有望成为针对化学和生物医学应用的新型纳米材料的基础。

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