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 synthesised by scalable suspension polymerisation, yielding high-affinity synthetic receptors with equilibrium dissociation constants of KD = 3.80 nM for PFOA and KD = 2.76 nM for PFOS. The nanoMIPs were immobilised 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 restricted interfacial charge transfer, producing a concentration-dependent differential pulse voltammetry response without externally added redox probes. The platform detected PFOA and PFOS over 1-100 pg mL-1, with limits of detection of 1.11 pg mL-1 and 1.63 pg mL-1, respectively. Strong molecular discrimination was demonstrated against structurally related PFAS homologues, including perfluorohexanoic acid (PFHxA) and perfluorodecanoic acid (PFDA), as well as chemically distinct non-target compounds. Quantification in drinking water and freshwater samples yielded recoveries of 88-96%. 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.