Engineering hierarchical Ag nanoparticles-coated periodic nanoripples for enhanced SERS performance

Surface-enhanced Raman scattering (SERS) is renowned for its ultra-sensitivity, rapidity, and non-destructive nature, making it invaluable in environmental monitoring, food safety testing, and biomedical diagnostics. Efficient fabrication of low-cost, contamination-free, reusable, and functional SERS substrates is highly desirable. This work introduces a simple and cost-effective method for fabricating SERS substrates by combining femtosecond (fs) laser-induced periodic surface structuring (LIPSS) with electrochemical deposition of silver nanoparticles (Ag NPs) on stainless steel mesh (SSM). The highly uniform and periodic nanostructures can be induced by fs laser on the surface of SSM, acting as substrate and enabling the electrochemically deposited Ag NPs to grow into three dimensional (3D) nanostructures. This significantly increases the number of "hot spots" and enhances SERS signal intensity due to the innovative hierarchical micro/nanostructures and concentration enriched effect. The performance of the substrates was evaluated using Rhodamine 6 G (R6G) and malachite green (MG) as probe molecules, achieving detection limits (LOD) of 1.35 × 10⁻¹ ² M and 1.28 × 10⁻¹ ⁰ M, with enhancement factors (EF) of 3.58 × 10⁹ and 1.88 × 10⁷, respectively. The substrates exhibit high reproducibility and uniformity, with a relative standard deviation (RSD) of 2.742 %. Moreover, stability tests demonstrated excellent mechanical and chemical robustness, as the substrate maintained stable SERS performance after ultrasonic treatment (40 kHz, 30 s) and exposure to acidic and alkaline environments (pH 3–11). Numerical simulation results demonstrate the effectiveness of the nanostructures in enhancing SERS signal. This combined method simplifies fabrication and enables scalable production, proving promising for advanced molecular detection applications.