Superhydrophobicity-driven interfacial enrichment and SERS detection of PFOA on nano-Cu modified Ag foam

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) present a serious risk to ecosystems and human health, underscoring the need for highly sensitive detection methods. Existing analytical approaches often lack the portability and rapid response required for on-site screening, and conventional surface-enhanced Raman spectroscopy (SERS) substrates exhibit limited affinity toward hydrophobic PFAS molecules. To overcome these limitations, we designed a superhydrophobic nano-Cu modified Ag foam that integrates hydrophobic enrichment with specific metal-carboxylate coordination for effective perfluorooctanoic acid (PFOA) capture and detection. The critical role of Cu²⁺ as a bridging site for selective PFOA adsorption was elucidated. This design achieves a remarkably low detection limit of 0.1 μg L^-1 for PFOA and enables discrimination between different PFAS categories. Moreover, it maintains excellent SERS activity after two months of storage, effectively addressing the issue of facile oxidation of Cu. The substrate was successfully applied to detect PFOA in various real water samples, demonstrating its potential as a practical and powerful platform for environmental PFAS monitoring.