Construction of a hybrid SERS chip composed of a microstructured Si metasurface and MoSxOy for sensitive molecular detection

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a powerful fingerprint spectroscopic technique capable of detecting trace molecules and has extensive application potential in diverse fields. SERS substrates with excellent Raman signal enhancement, scalability in large-scale fabrication, and long-term stability are of significant scientific interest and practical value. Herein, we report a hybrid SERS substrate, namely, tip-Si@MoS_xO_y, which integrates a periodic tip-patterned Si metasurface with MoS_xO_y semiconductor nanostructures, to develop a novel noble-metal-free SERS substrate with sensitive molecular detection performance. The engineered periodic Si metasurface enables broadband matrix resonance by coupling with incident light, significantly amplifying the localized near-field intensity at the inter-element nanogap regions. Theoretical calculations show that the maximum E-field enhancement can reach 511 times. Meanwhile, the MoS_xO_y semiconductor leads to modification of the polarization of probe molecules due to the charge-transfer between MoS_xO_y and probe molecules, enabling chemical mechanism based Raman enhancement. These combined effects enable the detection of rhodamine 6G (R6G) at concentrations as low as 10⁻⁹ M and an enhancement factor as high as 10⁷. Moreover, the hybrid substrate exhibits superior antioxidation properties, eliminating the requirement for inert storage environments necessary for traditional noble-metal-based SERS substrates. Moreover, the MoS_xO_y semiconductor nanostructures are covalently bonded to the metasurface, ensuring structural stability without the need for post-transfer processes. Therefore, our work provides a novel approach to develop hybrid substrates with improved SERS performance, which is readily achievable and is expected to attract more research enthusiasm in the future.