In situ synthesis of molecularly imprinted polymers by near-field photopolymerization for ultrasensitive PFOA plasmonic plastic fiber optic sensors

Per- and polyfluoroalkylated substances (PFAS), in particular perfluorooctanoic acid (PFOA), are persistent environmental pollutants that constitute major health risks due to their toxicity and bioaccumulation potential. Their detection is therefore a crucial and immediate challenge. This study presents an innovative nanofabrication approach for preparing highly sensitive sensors to detect PFOA. This approach is based on molecularly imprinted polymers (MIPs) obtained by near-field photopolymerization (NFPP). These MIPs are grafted onto a gold-coated plastic optical fiber (POF), thanks to near-field light enhancement by surface plasmon resonance (SPR). This approach enables nanoscale functionalization of POFs by MIPs, promoting accessibility to specific sites and optimizing coupling with surface plasmon. By adjusting the thickness of the MIPs through light irradiation, scalable limits of detection (LOD) from 53 aM to 6.3 pM were obtained, enabling coverage of concentrations ranging from attomolar to nanomolar scales, with a response time of only 10 min. POF@MIP sensors also show excellent selectivity, with no response in the presence of two analogues even at concentrations 100 times higher than that of PFOA. This PFAS sensor, exploiting SPR, is the first to achieve an LOD in the attomolar range, paving the way for advanced monitoring of these environmental contaminants.