Macromolecular Fluorimetric Probe With Naphthalimide Pendants for Selective Formaldehyde Detection

Formaldehyde (FA), a toxic and carcinogenic compound used extensively in industrial and preservation processes, requires reliable and selective detection methods, particularly in environmental, food, and biomedical samples. Herein, we report the development of a water-soluble, naphthalimide-based fluorescent polymeric probe, DCP-1, for the selective and rapid sensing of FA in aqueous solutions at physiological pH. The polymer has aromatic amine functional groups in its side chains, which specifically react with FA to form a stable imine. This transformation inhibits the native photoinduced electron transfer (PET), resulting in a distinct "turn-on" fluorescence response in an aqueous medium. The generation of the imine adduct was confirmed by mass spectrometry (MS) and ¹H NMR spectroscopy for the representative reaction between a small molecule analogue and FA. DCP-1 exhibits excellent sensitivity, detecting FA at concentrations as low as 1.28 nM and displaying a strong fluorescence response within minutes at 100 nM FA. The probe exhibited reversible behavior upon bisulfite addition, demonstrating its ability to be reused efficiently for multiple FA detection cycles with consistent performance. Density functional theory (DFT) calculations further validated the proposed PET-based sensing mechanism.