Thin WS2 nanotubes from W18O49 nanowires

Abstract

Single- and double-walled WS2 nanotubes of small diameter (<10 nm) and few layers (<4) have been synthesized by heating ultrathin W18O49 nanowires and S powders in an H2/Ar atmosphere at 840°C. In the process of formation and growth of a WS2 nanotube, the W18O49 phase transformed first into an amorphous WS3 structure via the absorption and diffusion of the sulfur atoms to substitute the oxygen atoms, and followed by a phase transition from amorphous WS3 to 2H-WS2 by losing sulfur atoms to form the shell of the WS2 nanotube.