Mechanisms of carbon nanotube aggregation and the reversion of carbon nanotube aggregates in aqueous medium.
Mechanisms of carbon nanotube aggregation and the reversion of carbon nanotube aggregates in aqueous medium.
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DOI：
10.1021/la5014279
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发表时间：
2014-09-16
期刊：
影响因子：
--
通讯作者：
Cheng W
中科院分区：
文献类型：
--
作者：
Koh B;Cheng W
分散在水介质中的单壁碳纳米管（SWCNT）在化学、生物学和医学领域具有许多潜在的应用。分散在水中的单壁碳纳米管的可逆聚集已被频繁报道，但其背后的机制尚不清楚。在这里，我们表明，在各种带电分子的辅助下分散到水介质中的单壁碳纳米管可以通过具有两种不同机制的各种电解质可逆地聚集。当表面电荷从 74% 中和到 86% 时，抗衡离子与 SWCNT 的直接结合会导致聚集。这种聚集是由静电而不是范德华相互作用驱动的，因此与多价阳离子诱导的 DNA 凝聚相似。螯合剂对抗衡离子的螯合导致单壁碳纳米管聚集体的再分散。与各种金属离子相比，聚电解质具有通过在各个单壁碳纳米管之间桥接来诱导单壁碳纳米管聚集的独特能力。通过利用各种断链机制，包括聚合物链中二硫键的还原以及蛋白水解酶的裂解作用，可以将通过后一种机制的聚集设计为可逆的。这些发现阐明了单壁碳纳米管聚集的机制，并对单壁碳纳米管在水中的各种应用具有广泛的影响。
Single-walled carbon nanotubes (SWCNTs) dispersed in aqueous medium have many potential applications in chemistry, biology, and medicine. Reversible aggregation of SWCNTs dispersed in water has been frequently reported, but the mechanisms behind are not well understood. Here we show that SWCNTs dispersed into aqueous medium assisted by various charged molecules can be reversibly aggregated by a variety of electrolytes with two distinct mechanisms. Direct binding of counterions to SWCNTs leads to aggregation when the surface charge is neutralized from 74 to 86%. This aggregation is driven by electrostatic instead of van der Waals interactions, thus showing similarity to that of DNA condensation induced by multivalent cations. Sequestration of counterions by chelating reagents leads to the redispersion of SWCNT aggregates. In contrast to various metal ions, polyelectrolytes have the unique ability to induce SWCNT aggregation by bridging between individual SWCNTs. Aggregation through the latter mechanism can be engineered to be reversible by exploiting various mechanisms of chain breaking, including reduction of disulfide bond in the polymer chain, and the cleavage action of proteolytic enzymes. These findings clarify the mechanisms of SWCNT aggregation, and have broad implications in various applications of SWCNTs in water.
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