Alessandro F, Scarcello A, Basantes Valverde M D, Coello Fiallos D C, Osman S M, Cupolillo A, Arias M, Arias de Fuentes O, De Luca G, Aloise A, Curcio E, Nicotra G, Spinella C, Caputi L S
Surface Nanoscience Group, Department of Physics, University of Calabria, Via P. Bucci Cubo 31C, I-87036 Rende, Cosenza, Italy.
Nanotechnology. 2018 Aug 10;29(32):325601. doi: 10.1088/1361-6528/aac4ca. Epub 2018 May 15.
Carbon nano-onions (CNOs), in their spherical or polyhedral forms, represent an important class of nanomaterials, due to their peculiar physical and electrochemical properties. Among the different methods of production, arc discharge between graphite electrodes sustained by deionized water is one of the most promising to obtain good quality CNOs in gram quantities. We applied the method with the aim to optimize the production of CNOs, using an innovative experimental arrangement. The discharges generate dispersed nanomaterials and a black hard cathodic deposit, which were studied by transmission electron microscopy-high-resolution TEM, scanning electron microscopy, Raman, thermogravimetric analysis and energy-dispersive x-ray spectroscopy. A simple mechanical grinding of the deposits permitted us to obtain turbostratic polyhedral CNOs that exhibited higher stability towards burning in air, compared to CNOs found in water. We propose a mechanism for the formation of the CNOs present in the deposit, in which the crystallization is driven by a strong temperature gradient existing close to the cathode surface at the beginning of the process, and subsequently close to the deposit surface whenever it is growing.
碳纳米洋葱（CNOs）呈球形或多面体形态，因其独特的物理和电化学性质，是一类重要的纳米材料。在不同的生产方法中，由去离子水维持的石墨电极间的电弧放电是最有希望以克量级获得高质量CNOs的方法之一。我们采用该方法，旨在通过创新的实验装置优化CNOs的生产。放电产生了分散的纳米材料和黑色硬阴极沉积物，通过透射电子显微镜-高分辨率TEM、扫描电子显微镜、拉曼光谱、热重分析和能量色散X射线光谱对其进行了研究。对沉积物进行简单的机械研磨，使我们获得了与水中发现的CNOs相比，在空气中燃烧稳定性更高的乱层多面体CNOs。我们提出了一种沉积物中存在的CNOs的形成机制，其中结晶过程在开始时由阴极表面附近存在的强温度梯度驱动，随后在沉积物生长时由沉积物表面附近的强温度梯度驱动。
