Carbon nanotubes (CNTs) are promising one-dimensional nanomaterials for electronics, sensors, energy storage, and high-performance composites. Their practical performance depends strongly on structural quality at the single-tube level. High-crystallinity CNTs with parallel straight walls are free of defects and exhibit physicochemical properties that are close to theoretical predictions. However, the controllable synthesis of high-crystallinity CNTs under practical conditions remains challenging because the structure and dynamic evolution at CNT-catalyst interface during growth are not fully understood.
A research team led by Chang Liu and Lili Zhang from the Institute of Metal Research, Chinese Academy of Sciences, and Feng Ding from Suzhou Laboratory achieved the in situ growth of single- and few-wall high-crystallinity CNTs using atmospheric environmental transmission electron microscopy (ETEM), while tracking the dynamic growth behavior of CNTs by focusing the CNT-catalyst interface.
Two rotational growth modes were identified: free rotation and restricted rotation. In the free-rotation mode, the growing CNT is attached only to the catalyst nanoparticle without additional external constraints. Under this condition, the CNT can rotate freely around the catalyst particle and grow into a straight, high-crystallinity tubular structure. This free-rotation behavior is enabled by weak CNT-catalyst interfacial interactions, which provide unrestricted pathways for carbon incorporation and facilitates the formation of high-crystallinity CNTs.
When the growing CNT contacts the substrate, neighboring CNTs, or nearby particles, its rotational freedom becomes restricted. These additional contacts impose local interfacial constraints, causing the growth mode to change from free rotation to restricted rotation. Under restricted rotation, structural distortions and defects are more likely to form, and the growth rate decreases. In some cases, strong restriction can even lead to growth termination. By combining real-time ETEM observations with atomistic simulations, the researchers further revealed that restricted rotation constrains carbon incorporation pathways at the CNT-catalyst interface.
This work establishes rotational freedom as the key link between catalyst-CNT interfacial interactions and CNT quality, and proposes interface regulation as a strategy for controlled synthesis of high-crystallinity CNTs.
The paper, titled “Revealing the rotational growth of carbon nanotubes by atmospheric environmental transmission electron microscopy,” was published in Science Bulletin .
Science Bulletin
Experimental study