Formation mechanism of fullerenes

富勒烯的形成机理是富勒烯科学中最困难的问题之一，也是开发工业上有利的C60合成所迫切需要的问题，这实际上是阻碍富勒烯碳应用出现的关键障碍。在本次资助期间，我们明确了其机理，并提出了两种全新的、有前途的C60制备方法。我们的工作是由来自中国云南省的一种新型煤炭样品所激发的，该样品含有令人惊讶的高浓度C60/C70（挖掘后的初始浓度估计为0.3%）。我们发现了三件证据表明这种特殊的煤受到了冲击波的影响。最有力的证据是具有极小直径（直径约10纳米）的煤烟初级颗粒丰度高。注意到最纯净和最容易获得的煤烟是商业炭黑，因此我们在我们的实验中使用了炭黑。虽然炭黑不含有可测量的C60，但我们观察到炭黑的初级颗粒在聚焦电子束（冲击波的替代品）照射下干净地转化为洋葱状的多壳富勒烯。在TEM中仔细检查了这一转变，发现螺旋粒子作为中间物的干预。此外，我们还发现洋葱变成了螺旋形。我们假设螺旋状的TEM图像代表三维螺旋状粒子，形状与洋葱接近。化学模型和数值模型被构思和生成。这些工作最终使我们构建了一个一致的富勒烯形成机制，包括螺旋状体的螺旋生长和螺旋状颗粒通过可逆的多键裂解/壳间价异构化反应/多键闭合稳定成洋葱。这一机制的成功阐明了洋葱独特形态的起源，鼓励我们设想一种利用炭黑生产线生产C60的新方法。另一种生产C60的新方法是简单地将碳暴露在冲击加热中。如果炸药爆轰产生冲击波，而煤是碳材料，则C60的生产可以在煤矿现场进行。该方法具有成本效益，通过燃烧煤作为燃料减少二氧化碳排放，有助于解决环境问题，并且还促进了爆炸物的和平使用。先前文献中已经报道了一些例子，表明在某些条件下，一些冲击波会产生富勒烯而不是金刚石。例如，在激波管实验中，当苯受到爆震时，形成300 ppm的C60。要验证目前的建议，还需要进行一些仔细的初步实验。少

Mechanism of fullerene formation is one of the most difficult problems in fullerene science but has been urgently needed in order to develop industrially favorable synthesis of C60, which is actually a critical obstacle to the emergence of applications of fullerene carbons. During the tenure of this grant, we clarified the mechanism and proposed two entirely new and promising methods of the preparation of C60.Our work is motivated by a novel coal sample arrived from Yunnan Province, China, that contains surprisingly high concentration of C60/C70 (an initial concentration immediately after excavation estimated to be 0.3%). We found three pieces of evidence that indicate that this particular coal has been exposed to shock wave. The strongest evidence is high abundance of the primary particles of soot with extremely small diameter (ca 10 nm in diameters). Noting the fact that the purest and the most readily available soot is commercial carbon black, we thereupon used carbon black in our s … More ubsequent study. Whereas carbon black did not contain measurable amounts of C60, we observed that the primary particles of carbon blacks are cleanly converted to onion-like multi-shell fullerenes upon irradiation with focused electron beam (a substitute of shock wave). Careful examination of this transformation in TEM revealed intervention of spiral particles as the intermediate. Furthermore, we also found that onion changes into spirals. We assumed that the spiral TEM images represent 3D spiroidal particles close in shape with onions. Chemical as well as numerical models were conceived and generated. These works eventually led us to construct a consistent mechanism of fullerene formation consisting of spiral growth of spiroids and the stabilization of spiroid particles into onions by reversible multiple bond cleavage/intershell valence isomerization reactions/multiple bond closure. Success of this mechanism to elucidate the origin of unique configuration of onions encouraged us to conceive a new method of C60 production that uses the production line of carbon black.Another new method of C60 production is simply to expose carbon to shock heating. If shock wave is generated by detonation of explosives and coal is carbon materials, the production of C60 may be carried out on the coal mine site. The method is cost effective, contributes to environmental problem by reducing the CO2 emission by burning coal as the fuel, and also promotes the use of explosives for peaceful purposes. There are already some examples previously reported in the literature that indicates that somewhat shock wave will generate fullerenes in stead of diamond under some conditions. For example, in a shock tube experiment, 300 ppm of C60 was formed when benzene was subjected to detonative shock. A few careful preliminary experiments will be needed to verify the present proposal. Less