NanoMIP-embedded metal-phenolic networks as an advanced electrochemical platform for the ultrasensitive detection of PFOA and PFOS in water

Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic fluorinated contaminants that require rapid, sensitive, and field-deployable analytical technologies beyond conventional laboratory-based mass spectrometry. Here, we report a nanoMIP--metal--phenolic network (MPN) electrochemical sensing platform for highly sensitive detection of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) in water samples. PFOA- and PFOS-specific molecularly imprinted polymer nanoparticles (nanoMIPs) were synthesized by scalable suspension polymerization, yielding high-affinity synthetic receptors with equilibrium dissociation constants of K_D = 3.80 nM for PFOA and K_D = 2.76 nM for PFOS. The nanoMIPs were immobilized onto flexible screen-printed electrodes through a redox-active MPN containing an embedded electrochemical mediator, creating an integrated recognition-and-transduction interface. PFAS rebinding within the nanoMIP layer partially restricted ion transport and mediator accessibility, suppressing interfacial charge transfer and producing a concentration-dependent differential pulse voltammetry response without externally added redox probes. The platform detected PFOA and PFOS over 1--100~pg /mL, with limits of detection of 1.11 pg /mL and 1.63 pg /mL, respectively. Strong molecular specificity was demonstrated against structurally related PFAS analogues and chemically distinct non-target compounds. Accurate quantification was achieved in drinking water and freshwater samples, with recoveries exceeding 90%. By combining scalable nanoMIP synthesis, redox-active interfacial engineering, and flexible electrode fabrication, this work establishes a practical platform for portable PFAS monitoring and broader environmental sensing applications.