Center of Excellence for Nanostructured Materials and INSTM, unit of Trieste, Dipartimento di Scienze Chimiche e Farmaceutiche, University of Trieste, Piazzale Europa 1, I-34127 Trieste, Italy.
J Am Chem Soc. 2012 Aug 15;134(32):13310-5. doi: 10.1021/ja303131j. Epub 2012 May 18.
We report the direct formation of multiwalled carbon nanotubes (MWNT) by ultrasonication of graphite in dimethylformamide (DMF) upon addition of ferrocene aldehyde (Fc-CHO). The tubular structures appear exclusively at the edges of graphene layers and contain Fe clusters. Fc in conjunction with benzyl aldehyde, or other Fc derivatives, does not induce formation of NT. Higher amounts of Fc-CHO added to the dispersion do not increase significantly MWNT formation. Increasing the temperature reduces the amount of formation of MWNTs and shows the key role of ultrasound-induced cavitation energy. It is concluded that Fc-CHO first reduces the concentration of radical reactive species that slice graphene into small moieties, localizes itself at the edges of graphene, templates the rolling up of a sheet to form a nanoscroll, where it remains trapped, and finally accepts and donates unpaired electron to the graphene edges and converts the less stable scroll into a MWNT. This new methodology matches the long held notion that CNTs are rolled up graphene layers. The proposed mechanism is general and will lead to control the production of carbon nanostructures by simple ultrasonication treatments.
我们报告了在加入二甲基甲酰胺（DMF）中的二茂铁甲醛（Fc-CHO）后，通过超声石墨直接形成多壁碳纳米管（MWNT）。管状结构仅出现在石墨烯层的边缘，并包含 Fe 簇。Fc 与苯甲醛或其他 Fc 衍生物结合不会诱导 NT 的形成。向分散体中添加更多量的 Fc-CHO 不会显著增加 MWNT 的形成。升高温度会减少 MWNTs 的形成量，并显示出超声诱导空化能的关键作用。可以得出结论，Fc-CHO 首先降低了将石墨烯切成小片段的自由基反应性物质的浓度，将自身定位在石墨烯的边缘，模板化薄片的卷起以形成纳米卷，其中它被捕获，最后接受并将不成对的电子捐赠给石墨烯边缘，并将不太稳定的卷转化为 MWNT。这种新方法符合 CNT 是卷曲的石墨烯层的长期观念。所提出的机制是通用的，将通过简单的超声处理来控制碳纳米结构的生产。
