The Transformation Pathways of Mo₆S₂I₈ Nanowires into Morphology-Selective MoS₂ Nanostructures

Nanomaterials prepared by the sulfurization of Mo₆S₂I₈ nanowires and the time and temperature dependence of the transformation process are investigated by high-resolution transmission electron microscopy, X-ray powder diffraction, and wavelength-dependent Raman spectroscopy. Depending on the temperature, coaxial MoS₂ nanotubes or MoS₂ “mama”-tubes are formed after 2 h of sulfurization. Using a few minutes of sulfurization time, core-shell nanowires composed of well-ordered MoS₂ layers covering a Mo₆S₂I₈ core are formed, proving an outside-to-inside transformation process. The crystallinity of the three MoS₂ nanostructures increases with increasing transformation temperature, i.e., in the sequence from MoS₂/Mo₆S₂I₈ core-shell structures via coaxial MoS₂ tubes to the MoS₂ “mama”-tubes. The analysis indicates a different nature of the defects in the MoS₂-based nanomaterials, originating from the sulfurization of the Mo₆S₂I₈ than in the conventional MoS₂ platelike crystals. A correlation between the Raman spectroscopic parameters and the defect density in MoS₂ is identified.