In situ construction of pine-needle-like AgNP/Cu(OH)₂/copper foam for ultrasensitive mixed-dyes analysis

The "hotspot effect," which is the primary enhancement mechanism of surface-enhanced Raman scattering (SERS), relies on ultrasmall nanogap structures that significantly amplify localized electromagnetic fields. Herein, a three-dimensional (3D) AgNP/Cu(OH)₂/copper foam (CF) composite SERS substrate with tunable "hotspots" was designed for the detection of organic dyes in environmental water samples. The proposed AgNP/Cu(OH)₂/CF platform exhibited excellent SERS activity, achieving a limit of detection (LOD) of 10^-8 M for rhodamine 6G (R6G) and an enhancement factor of 1.73 × 10⁶. Remarkably, this platform also displayed excellent uniformity, with a relative standard deviation (RSD) of less than 9%, and good long-term stability, retaining 73.7% of its initial signal intensity after 30 days of storage. Additionally, LODs of 10^-8 M were achieved for crystal violet (CV) and malachite green (MG). The substrate was also capable of the simultaneous and precise identification of dyes in binary mixed systems (R6G-CV, R6G-MG, and CV-MG) as well as in a ternary mixed system (R6G-CV-MG) in untreated natural river water, providing a feasible technical solution for the on-site rapid detection of multi-component organic pollutants in complex aquatic environments.