Encapsulation and electronic modulation of Mo1-xWxS2 nanoribbons in single-walled carbon nanotubes

Abstract

<p>One-dimensional (1D) transition metal dichalcogenides (TMDCs) hold promising applications in nanoelectronics and optoelectronics. However, synthesizing sub-10 nm wide TMDC nanoribbons with precise doping control remains challenging. Here, we introduce a solution-based two-step approach to synthesize atomically thin Mo1-xWxS2 (0< 1) nanoribbons within single-walled carbon nanotubes (SWCNTs). Atomic resolution scanning transmission electron microscopy (STEM) imaging reveals W doping sites in the 1–3 nm wide and 1–3 layers thick nanoribbons, with ribbon dimensions limited by the SWCNT diameter. Across all W doping levels, bond lengths (Mo–Mo, W–W, and Mo–W) remain almost unchanged (0.31–0.32 nm), ensuring structural integrity. Raman spectroscopy and ultraviolet–visible–near-infrared (UV–Vis–NIR) absorption spectroscopy analyses reveal that W doping significantly modifies the characteristic vibrational modes of MoS2 and consequently modulates the electronic structure of the host SWCNTs. Scanning tunneling microscopy/spectroscopy (STM/S) measurements further reveal the coexistence of localized n-type and p-type doping regions within SWCNT, highlighting its potential for constructing intra-nanotube p–n heterojunctions. Density functional theory (DFT) calculations show that the charge transfer between MoS2 nanoribbons and SWCNTs depends on the number of nanoribbon layers and strongly on the SWCNT diameter and structural deformation at the interface, and further highlight the role of edge Mo–C interactions in driving the charge transfer. This study establishes a scalable doping strategy for TMDC nanoribbons in SWCNTs, elucidating their tunability for future 1D nanoelectronic and optoelectronic devices.</p>