van der Waals one-dimensional atomic crystal heterostructure derived from carbon nanotubes

One-dimensional (1D) van der Waals (vdWs) heterojunctions, due to the dimensional reduction leading to 1D quantum confinement effects and interface effects of the heterojunctions, typically exhibit discrete energy levels and strong electron interactions, resulting in unique conductive and optical behaviors. Carbon nanotube (CNT)-derived 1D atomic crystal vdWs heterojunctions represent a new class of 1D vdWs heterojunctions. They leverage the excellent chemical stability, nanoscale cavities, and adjustable diameters provided by CNTs as templates, ensuring controlled synthesis and precise structural tuning. The 1D radial pathways can alter the photonic-electronic propagation characteristics. At the same time, their unique metal-semiconductor-like electronic structure creates conditions for constructing various types of heterojunctions. The CNTs and their encapsulated 1D materials can lead to synergistic enhancement in the fields of electronics, magnetism, and optics. Currently, research is concentrated on understanding the synthesis mechanisms, integration characteristics, and host-guest interactions, and the exploration of novel 1D atomic crystal vdWs heterojunctions derived from CNTs. This review is focused on the latest progress made in 1D vdWs heterojunctions using CNTs as growth templates, emphasizing the construction methods, selection criteria, and the unique properties and applications arising from these complex interfacial electronic or phonon interactions. We also propose several future directions for the development of CNT-derived 1D atomic crystal vdWs heterojunctions. This review aims to enhance the understanding of their synthesis mechanisms and fundamental properties, broaden the range of available materials, and explore new and broader applications.