Molecular-interfacial-electronic triple design for enhanced cooperative adsorption and SERS detection of perfluorooctanoic acid

Perfluorooctanoic acid (PFOA), the most environmentally ubiquitous representative of per- and polyfluoroalkyl substances (PFAS), has posed global environmental and health risks due to its persistence. To address the challenges of insufficient adsorption, low intrinsic Raman activity and poor specific recognition of PFOA, this study designed a multifunctional surface-enhanced Raman scattering (SERS) platform based on hollow bowl-like fluorinated covalent organic framework with in-situ grown gold nanoparticles (F-BHCOF/AuNPs) at molecular, interfacial and electronic levels. This material was synthesized via an “amorphous-to-crystalline induced transformation” method. First, fluorinated monomers achieve fluorination at the molecular level. Moreover, the controllably synthesized hollow bowl-like structure, at the interfacial level, not only utilizes the “eddy effect” to enhance mass transfer at low concentrations, but also synergistically enhances the electromagnetic field via dual “confinement effects” throughout the structure. Combined with the “polarization induction” mechanism at the electronic level to mediate photoinduced charge transfer, this platform achieves nearly complete adsorption and specific, direct SERS detection of PFOA at environmentally relevant concentrations, with a detection limit of 1.6 ng/L. This platform can be further extended to the rapid screening and exposure risk assessment of PFOA in environmental water samples and daily consumer products including non-stick pan coatings and waterproof outdoor jackets. Furthermore, this work provides a paradigm for the tailored design of functional materials and for overcoming the technical bottleneck of simultaneous adsorption and detection of PFOA and other similar trace-level pollutants with weak response.