A fully flattened carbon nanotube (FNT), a graphene nanoribbon (GNR) analogue, provides a hollow space at edges for endohedral doping. Due to the unique shape of the hollow space of FNTs, novel types of low-dimensional arrangements of atoms and molecules can be obtained through endohedral doping into FNTs, which provides a new type of nanopeapods. FNT-based nanopeapods have been synthesized through endohedral doping of C₆₀, and their structural characterization with transmission electron microscopy (TEM) performed. The doping of C₆₀ into the inner hollow space of FNTs has been carried out via the gas-phase filling method, where open-ended FNTs are sealed in a glass ampoule and heated at 723–773 K for two days. TEM observations show that most of the encapsulated C₆₀ molecules align as single molecular chains along the edges of FNTs and that some of the C₆₀ forms two-dimensional close-packed structures inside FNTs.

Although the inter-layer coupling in layered materials has attracted considerable interest due to its importance in determining physical properties of two-dimensional systems, studies on the inter-layer coupling in one-dimensional systems have so far been limited. Double-wall carbon nanotubes (DWCNTs) are one of the most fundamental and ideal model systems to study the inter-layer coupling in one-dimensional systems. In this work, Rayleigh scattering spectroscopy and transmission electron microscopy are used to characterize the electronic transition between inner-and outer-nanotubes of the exactly same individual DWCNT. We find that the inter-layer coupling is strong, leading to downshifts in most of the optical transition energies (up to ~0.2 eV) compared to isolated CNTs. We also find that the presence of metallic tubes lead to stronger shifts. The inter-layer screening of Coulomb interactions is one of the key factors in explaining the observed results.

We have developed a process for chemical purification of carbon nanotubes for solution-processable thin-film transistors (TFTs) having high mobility. Films of the purified carbon nanotubes fabricated by simple drop coating showed carrier mobilities as high as 164 cm²V⁻¹s⁻¹, normalized transconductances of 0.78 Sm⁻¹, and on/off current ratios of 10⁶. Such high performance requires the preparation of a suspension of micrometer-long and highly purified semiconducting single-walled carbon nanotubes (SWCNTs). Our purification process includes length and electronic-type selective trapping of SWCNTs using recycling gel filtration with a mixture of surfactants. The results provide an important milestone toward printed high-speed and large-area electronics with roll-to-roll and ink-jet device fabrication.

Crystalline ErCl₃ nanowires have been fabricated in single-walled carbon nanotubes (SWCNTs) with high yield (~90%), and the structural and magnetic properties of the resulting ErCl₃ nanowires encapsulated in SWCNTs (ErCl₃@SWCNTs) characterized. Encapsulation under high temperature and vacuum using high quality SWCNTs results in a high filling-ratio of ErCl₃ nanowires in the SWCNTs. The high filling-ratio of ErCl₃ nanowires and the use of highly pure SWCNTs with only a small amount of residual Fe catalyst nanoparticles enabled us to observe the magnetic properties of ErCl₃@SWCNTs. Structure determination based on simulated annealing calculations and high-resolution transmission electron microscope (HRTEM) image simulations revealed that the structure of the ErCl₃ nanowires is unusual with respect to the coordination environment of the Eu³⁺ ions. This work opens up new possibilities to fabricate various metal complex nanowires with high yield and may also be of more general importance in understanding and exploring magnetic properties in low-dimensional magnetic systems.