Recently, a new strategy for synthesis and characterization of curved large π-conjugated capped zigzag carbon nanotube (CNT) segment was reported by Professor Pingwu Du’s research group at University of Science and Technology of China (USTC). This is the first time to use a conjugated nanographene part as the "cap" template to construct a curved conjugated CNT fragment. By rationally design, the three-dimensional CNT segment was realized by collecting two nanographene parts through the curved cyclohexane molecule, followed by the aromatization reaction. This work has been recently published at Angewandte Chemie International Edition (DOI: 10.1002/anie.201804031) and the title is "“A Three-Dimensional Capsule-like Carbon Nanocage as a Segment Model of Capped Zigzag [12,0] Carbon Nanotubes: Synthesis, Characterization, and Complexation with C70”.

CNTs are conjugated one-dimensional nanomaterials, with a very light density and perfect hexagonal structure, demonstrating many excellent mechanical, electrical and chemical properties. CNT-based materials with a fixed size and chirality have great application potentials in the field of nanotechnology, energy science, and nanoelectronics. Currently, the practical applications of CNTs are significantly hampered by several major problems. Among them are the lack of reliable methods to control the alignment and position of nanotubes, and perhaps the most problematically, the growth of nanotubes with specific sizes and chiralities, yielding random mixtures of metallic and semiconducting nanotubes. So far, the chemical synthesis of length- and diameter-specified finite model of carbon nanotube (CNT segments), as possible seeds for CNT formation, is still a great challenge in chemistry and material science. Until now, in the literature, no large π-extended nanographenes (for example, Hexa-peri-hexabenzocoronene (HBC) unit) have been used as the capping unit to build the segment of a capped zigzag carbon nanotube. The rational design and construction of carbon nanotube fragments can be used as the ideal precursor or template for the preparation of pure carbon nanotubes with a fixed chirality.

Based on a series of previous work on the new structure syntheses of carbon nanotube segments, Professor Du’s research group has successfully designed and synthesized this present capped [12,0] CNT segment with two nanographene units as the “cap” part through palladium and nickel-based coupling reactions (Figure 1). The strategy for vertically cutting zigzag carbon nanotubes is firstly proposed. By collaboration with Professor Shangfeng Yang at University of Science and Technology of China and Professor Guilin Zhuang at Zhejiang University of Technology, the selective supramolecular interaction of the capped CNT segment with fullerene C70 was revealed and the selective binding of 1:1 to C70 was found. This present synthesis method to connect two capped nanographene parts with curved linkers, which provides a new strategy for the construction of capped carbon nanotubes/segments. The first author of this work is Mr. Shengsheng Cui, a PhD candidate at University of Science and Technology of China.

Figure 1. The design of tripodal-[2]HBC carbon nanocage as a novel finite model of capped [12,0] carbon nanotube.

The above research work is supported by the Ministry of Science and Technology of the People´s Republic of China, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), the National Natural Science Foundation of China, and University of Science and Technology of China (USTC).

Publication link：https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201804031