ABSTRACT
Tungsten disulfide (WS2) nanotubes exhibit various unique properties depending on their structures, such as their diameter and wall number. The development of techniques to prepare WS2 nanotubes with the desired structure is crucial for understanding their basic properties. Notably, the synthesis and characterization of multi-walled WS2 nanotubes with small diameters are challenging. This study reports the synthesis and characterization of small-diameter WS2 nanotubes with an average inner diameter of 6 nm. The optical absorption and photoluminescence (PL) spectra of the as-prepared nanotubes indicate that a decrease in the nanotube diameter induces a red-shift in the PL, suggesting that the band gap narrowed due to a curvature effect, as suggested by theoretical calculations.
ABSTRACT
Transition metal dichalcogenide (TMDC) nanotubes exhibit unique physical properties due to their nanotube structures. The development of techniques for synthesizing TMDC nanotubes with controlled structures is very important for their science and applications. However, structural control efforts have been made only for the homostructures of TMDC nanotubes and not for their heterostructures that provide an important platform for their two-dimensional counterparts. In this study, we synthesized heterostructures of TMDC nanotubes, MoS2/WS2 heteronanotubes, and demonstrated a technique for controlling features of their structures, such as diameters, layer numbers, and crystallinity. The diameter of the heteronanotubes could be tuned with inner nanotube templates and was reduced by using small-diameter WS2 nanotubes. The layer number and crystallinity of the MoS2 outer wall could be controlled by controlling their precursors and synthesis temperatures, resulting in the formation of high-crystallinity TMDC heteronanotubes with specific chirality. This study can expand the research of van der Waals heterostructures.
