Moriai Tatsuya, Tsukamoto Takamasa, Fukuhara Kaori, Imaoka Takane, Kambe Tetsuya, Yamamoto Kimihisa
Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology Yokohama-shi Kanagawa 226-8503 Japan
ERATO, JST Kawaguchi-shi Saitama 332-0012 Japan.
Nanoscale Adv. 2024 Dec 2;7(1):346-353. doi: 10.1039/d4na00740a. eCollection 2024 Dec 17.
Carbon nanotubes (CNTs) are useful nanomaterials owing to their distinct functions that depend on their structure and diameter; therefore, CNTs have recently attracted much attention. Catalytic chemical vapor deposition using metal nanoparticles as catalysts is one of the most useful methods for synthesizing CNTs. However, fine control of the CNT diameter has been technically difficult at the 1 nanometer level owing to the size distribution of metal nanoparticles and the difficulty in suppressing their aggregation during the CNT growth reaction. In this study, we developed a method for simultaneously conducting nanoparticle formation and CNT growth through the preparation of nanoparticles using highly dispersed metal clusters on a support substrate as seeds. In this method, the migration and aggregation behavior of seed metal clusters on a substrate upon heating uniformly induces nanoparticle formation until nanoparticles are enlarged to suitable size for CNT growth, and then CNTs grow with a diameter corresponding to that of the nanoparticles. The nanoparticle size does not change afterward by spatial separation of the nanoparticles from the substrate due to the tip-growth mechanism of CNTs. Detailed analysis focusing on cobalt as a catalyst demonstrated that the diameters of the multi-walled CNTs could be simply tuned solely by modifying the reaction temperature and time. This result reveals that the synthetic concept using the seed clusters enables the control of the CNT size to a certain extent using only temperature control (thermal energy), without conventional separation processes for synthesizing nanoparticles and determining conditions to retain nanoparticle size.
碳纳米管（CNTs）因其取决于结构和直径的独特功能而成为有用的纳米材料；因此，碳纳米管最近备受关注。使用金属纳米颗粒作为催化剂的催化化学气相沉积是合成碳纳米管最有用的方法之一。然而，由于金属纳米颗粒的尺寸分布以及在碳纳米管生长反应过程中难以抑制其聚集，在1纳米级别对碳纳米管直径进行精确控制在技术上一直很困难。在本研究中，我们开发了一种方法，通过使用负载在基底上的高度分散的金属簇作为种子来制备纳米颗粒，从而同时进行纳米颗粒的形成和碳纳米管的生长。在这种方法中，加热时基底上种子金属簇的迁移和聚集行为会均匀地诱导纳米颗粒的形成，直到纳米颗粒长大到适合碳纳米管生长的尺寸，然后碳纳米管以与纳米颗粒直径相对应的直径生长。由于碳纳米管的尖端生长机制，纳米颗粒随后通过与基底的空间分离而尺寸不再变化。以钴作为催化剂进行的详细分析表明，仅通过改变反应温度和时间就可以简单地调节多壁碳纳米管的直径。这一结果表明，使用种子簇的合成概念能够仅通过温度控制（热能）在一定程度上控制碳纳米管的尺寸，而无需用于合成纳米颗粒和确定保持纳米颗粒尺寸条件的传统分离过程。
