Synthesis and optical properties of WS₂ nanotubes with relatively small diameters

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.