WS ₂ -Coupled Nanoconical Hyperbolic Metamaterials for Low-Noise and Uniform SERS Detection

This work presents a high-performance composite SERS substrate, which is formed by a vertically aligned gold nanocone array hyperbolic metamaterial (HMM) integrated with a two-dimensional tungsten disulfide (WS2) dielectric interlayer. This structure aims to create prominent hotspots at the tips of the nanocones through its unique conical geometry and periodic arrangement. At the same time, strong electromagnetic enhancement also occurs in the gaps between the cones, resulting in a high-density and uniform distribution of electromagnetic hotspots. The WS2 layer plays a critical dual role: it effectively suppresses fluorescence background, ensuring spectral clarity, and facilitates interfacial charge transfer, contributing to additional chemical enhancement. Finite-element simulations and experimental measurements reveal strong bulk plasmon polariton (BPP) excitation and vertically confined field distributions. Compared to conventional localized surface plasmon resonance (LSPR), the BPP in the HMM enables volume-localized and anisotropically enhanced fields, offering deeper field confinement and stronger light-matter interaction. The resulting platform achieves successful detection of Rhodamine 6G (R6G) and Malachite Green (MG) at concentrations as low as 10–10 and 10–8 M, with excellent signal uniformity and reproducibility. This substrate design offers a promising strategy for reproducible, low-noise, and ultrasensitive SERS detection.