In this investigation, a nonconjugated fluorescent polyamide with piperazine and valerolactam moieties (PAM-PV) has been synthesized by the modified Ugi polymerization using 1,4-bis(3-aminopropyl)piperazine, levulinic acid, and 1,4-bis(3-isocyanopropyl)piperazine as monomers. In the polymerization, the special construction of levulinic acid leads to the formation of valerolactam on PAM-PV chains via the Mumm rearrangement. PAM-PV shows a strong fluorescence emission at 428 nm due to the intramolecular aggregation of piperazine and valerolactam moieties along the backbone. Impressively, PAM-PV can specifically detect NO2- ions via static quenching with a linear range of 10(-6)-10(-5) M and a detection limit of 0.6 mu M (0.0276 mg/L), which was far less than the minimum allowable concentration of 3 mg/L for NO2- in drinking water specified by WHO. Furthermore, the several common anions and cations have no interference effects on the specific detection of PAM-PV to NO2- ions. The quenching mechanism of NO2- and PAM-PV by FTIR, UV, and H-1 NMR measurements indicates that the strong electrostatic interaction between NO2- and PAM-PV makes the macromolecular chains more relaxed and outstretched, leading to a formation of a nonfluorescent complex. Moreover, the practical detection of NO2- in the three water bodies, sauerkraut, and ham sausage and the fabrication of a portable detecting paper to NO2- ions were conducted in this experiment. (c) 2024 American Chemical Society