Fabrication and SERS Performance of SiO₂@Ag Core–Shell Structure Nanoparticle Array

Surface-enhanced Raman spectroscopy (SERS) is a versatile and powerful technique for the detection and identification of molecules, which has evolved into a valuable tool for both qualitative and quantitative analysis over the past few decades. In order to obtain excellent Raman signals enhanced performance, the substrates composed of different materials receive attention. In this work, we report a monolayer SiO₂@Ag core–shell nanoparticle array fabricated by a combined dip-coating and hydrothermal reduction method. The enhanced local electromagnetic field was induced on the SERS substrate due to the multimodal localized surface plasmon resonance (LSPR) effect around the spherical nanocomposites and the precisely controlled ultrasmall nanogaps within the plasmonic array, resulting in a strong “gap effect.” Rhodamine 6G (R6G) was employed as the probe molecule to evaluate the SERS performance of the substrate. The SERS intensity was observed to vary significantly with changes in nanoparticle distribution density. The optimized sample exhibited the strongest enhancement, with a Raman enhancement factor of 2.03 × 10⁹ and a limit of detection (LOD) as low as 2.43 × 10⁻¹⁶ mol/L. The relative standard deviation (RSD) was found to be less than 7%, indicating excellent reproducibility. These results highlight the potential advantages of the SiO₂@Ag nanoparticle array as a highly effective SERS substrate, demonstrating great promise for practical applications in sensitive molecular detection and analysis. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.