Ultrasensitive detection of perfluorooctanoic acid using a surface-enhanced Raman scattering-microfluidic sensor based on the p-phenylenediamine self-assembly strategy.

Per- and polyfluoroalkyl substances (PFAS) are widely employed in diverse industrial applications owing to their exceptional stain resistance, thermal stability, mechanical durability, and intrinsic non-biodegradable nature. Among this class of compounds, perfluorooctanoic acid (PFOA) stands as a representative and extensively investigated PFAS congener. However, given the high toxicity of PFOA and its severe adverse effects such as carcinogenicity, hepatic injury and immune dysfunction, the highly sensitive detection of PFOA is of vital importance. In this study, a microfluidic device for the highly sensitive detection of PFOA was fabricated using self-assembled p-phenylenediamine nanoparticles (SAp-PD) and an Au/TiO2 substrate. The device consists of two key parts: an Au/TiO2-based signal amplification system (spherical hollow mesoporous TiO2 modified with Au NPs, immobilized on a silicon wafer to enhance surface-enhanced Raman scattering (SERS) signals) and a SAp-PD-based detection mechanism (PFOA disrupts SAp-PD's self-assembled structure, reducing its Raman intensity). The method achieved a low limit of detection (LOD) of 2.57 × 10-8 M. Real sample detection successfully identified PFOA in fire-retardant fabrics, demonstrating the device's potential for quantitative PFOA detection in real environments and providing a practical approach.