Polyphenylamine nanosheets-based dual-mode fluorescence probe for ultrasensitive detection of perfluoroalkyls in water environment

Background Per- and polyfluoroalkyl substances (PFASs) have significant applications in industrial, military and other sectors, particularly perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), which are classified as “suspected human carcinogens”. However, their release into aquatic environments via both point and non-point sources during production and use poses serious hazards to human health, potentially leading to hepatotoxicity, immunotoxicity, reproductive and developmental toxicity, and carcinogenic effects. PFOS/PFOA levels in tap water from Hong Kong (China) are significantly exceeding the enforceable maximum contaminant level in drinking water of 4 ng/L. Therefore, rapid screening of their concentrations is essential for monitoring water safety. Results In response, dual-color fluorescence probes based on polyphenylamine nanosheets (Y-CNNS/R-CNNS) have been successfully prepared through simple oxidation polymerization and acid polymerization. The fluorescence intensity and absorbance of Y-CNNS increase with rising concentrations of PFOS or PFOA due to radiation transition enhancement and non-radiation transition inhibition. The limits of detection are calculated to be 0.738, 15.4, 0.246 and 3.90 pM, respectively. In contrast, the fluorescence intensity of R-CNNS is quenched after adding PFOS/PFOA, owing to complex formation, with limits of detection calculated at 5.44 and 10.2 pM respectively. These results indicate the capability to detect concentrations well below the health advisory level recommended by the United States Environmental Protection Agency and the Food and Drug Administration (10 ng/L) for PFOA/PFOS. This proposed method exhibits a high sensitivity, broader detection range and lower limits of detection compared to other reported methods. Significance A new “enhanced-quenching” dual-mode and dual-color sensor based on Y-CNNS/R-CNNS has been constructed for the high-sensitively detection of PFOS/PFOA. This proposed method also exhibits good performance in analyzing PFOS/PFOA in environmental water samples included bottled water, tap water, lake water, river water and seawater, providing a new idea for the highly sensitive analysis of other PFASs in water environment.