Beyond SERS Hotspot Localization: Metal–Dielectric Hybrid Metasurfaces with Coupled LSPR Enable Highly Reproducible, Label-Free Prostate-Specific Antigen Detection

Abstract

Surface-enhanced Raman scattering (SERS) is a powerful sensing technique; however, its reliance on extremely localized hotspots causes severe spot-to-spot signal variations, limiting reproducibility and macromolecule detection. Here, we report nanotransfer printing lithography to fabricate large-area, highly reliable 76 nm periodic metal–dielectric hybrid metasurfaces that resolve these constraints. The nanograting incorporates air-filled trenches between adjacent ridges, creating a spatially extended E-field area via near-field coupling between plasmonic nanomaterials. Through this coupled LSPR mode, the E-field exhibits an evanescent extension, with a simulated decay length of 325.9 nm and an experimentally estimated extension length of 364.3 nm. Integrating a Au nanowire array yields highly reproducible SERS signals, achieving a relative standard deviation of 3.16% over a 100 × 100 μm2 area. Furthermore, a Ag–Au alloy nanoparticle array enhances sensitivity, enabling attomolar-level R6G detection down to 10–18 M and label-free prostate-specific antigen detection down to 10 ng/mL.