Fabrication of ultrafine nanogroove array structures with “sharp” edges in 2D multilayer 2H-WS₂ for enhanced surface-enhanced Raman scattering

Edges of two-dimensional (2D) materials are generally more chemically reactive than their basal planes. Accordingly, engineering ultrafine edge architectures in 2D semiconductors is a compelling route to boost surface-enhanced Raman scattering (SERS). This work proposes an approach to enhance SERS sensing by fabricating ultrafine nanogroove array (NGA) structures on 2D multilayer 2H-WS₂ using femtosecond (fs) laser processing. Based on the fs laser-induced surface plasmon polariton-local near-field (SPP-LNF) effect, NGA structures with ultrafine groove widths are successfully fabricated. The processed regions remain a single-crystalline structure and exhibit “sharp” edges free of obvious amorphous or oxide layers, thereby achieving a breakthrough in non-ablation laser processing of 2D material edges. Compared with the unprocessed 2H-WS₂ regions, the NGA regions demonstrate significantly enhanced SERS sensing performance, achieving a detection limit down to 10⁻⁹ mol/L for crystal violet (CV) molecules, which is three orders of magnitude lower than that of pristine 2H-WS₂. Through combined theoretical and experimental analyses, the enhanced SERS performance of the NGA structures is attributed to the more active molecular adsorption at nanostructure edges and the intrinsic defects associated with sharp edges. This work offers a robust strategy for the controllable fabrication of edge structures and high-performance SERS sensing.