Metallic NbS₂ One-Dimensional van der Waals Heterostructures

This study presents the experimental demonstration of metallic NbS2-based one-dimensional van der Waals heterostructures using a modified NaCl-assisted chemical vapor deposition strategy. By employing a ″remote salt″ strategy, we realized precise control of the NaCl supply, enabling the growth of high-quality coaxial NbS2 nanotubes on single-walled carbon nanotube-boron nitride nanotube (SWCNT-BNNT) templates. Using this remote salt strategy, the morphologies of as-synthesized NbS2 could be tuned from 1D nanotubes to suspended 2D flakes. Structural characterization via high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) confirmed the formation of crystalline NbS2 nanotubes, with a double-walled preference compared to single-walled dominated behavior of semiconducting transition metal dichalcogenide analogs. Optical analyses using UV-vis-NIR and FTIR spectroscopy were consistent with the metallic nature of NbS2. Raman-based oxidation studies demonstrated a relatively higher degradation rate of 1D NbS2 under ambient conditions. Density functional theory (DFT) calculations further provided insight into the stabilization mechanism of double-walled NbS2 nanotubes, suggesting that interlayer charge transfer and Coulomb interactions contribute to the double-walled stabilization. These results provide a framework for synthesizing metallic 1D vdW heterostructures and elucidating their stabilization mechanisms.