Superhydrophobic/-philic SERS Platform Based on Femtosecond Laser-Induced Periodic Surface Structures and Ag Nanoparticles

The trace detection of molecules from highly diluted solutions is critical for biomedical diagnostics, environmental monitoring, food safety, and pharmaceutical quality control. We introduce a highly sensitive superhydrophobic/-philic surface-enhanced Raman scattering (SERS) platform with specific patterns for trace detection. A superhydrophobic structure was fabricated on stainless steel using femtosecond laser-induced periodic surface structures with chemical modification and annealing. The periodic wavy strips, measuring 654 nm in width, are uniformly distributed across a large area. Superhydrophilic patterns of various sizes and shapes were then created on the superhydrophobic surface through nanosecond laser processing. Studying the droplet evaporation process and deposition characteristics shows that target molecules concentrate at the vertex positions of the superhydrophilic pattern, significantly enhancing SERS performance. The triangular pattern with an 800 μm circumcircle diameter exhibited the highest enhancement among the patterns. We demonstrated trace detection of crystal violet mixed with Ag nanoparticles averaging 54 nm in diameter, achieving a Limit of Detection (LOD) of 1.22 × 10^–15 M and an enhancement factor of 3.69 × 10¹⁰. Furthermore, we integrated our platform with COF@Ag. The COFs display a nearly spherical morphology with an average diameter of 925 nm, and their surfaces are densely and uniformly covered with Ag nanoparticles. This significantly enhances the platform’s efficiency in trace detection, enabling the successful detection of the antibiotic amoxicillin with an LOD of 1.01 × 10^–11 M. This demonstrates the practical application of the superhydrophobic/-philic SERS platform in biosensing and quantitative analysis, positioning it as a powerful tool for trace detection across various fields.