A dual-responsive polyacrylamide sensor for colorimetric and fluorescent detection of Cu²

Polyacrylamide, a classic polymer material, has been extensively applied in both industrial production and daily life, owing to its outstanding physical and chemical properties. However, the absence of a conjugated π-electron system in its molecular structure severely restricts its application in the field of fluorescence. In this study, a novel fluorescent polyacrylamide sensor (P) was synthesized via free-radical precipitation polymerization using acrylamide and 3-[(Allylaminothiocarbonyl)hydrazinecarbonyl]-7-(diethylamino)-2H-chromen-2-one as monomers. Compared with conventional polyacrylamide, P exhibited great optical signals in pure water. Experimental results demonstrated that upon the presence of copper (Cu²⁺), P could rapidly respond through significant changes in its colorimetric or fluorescence signals. The detection process was characterized by a fast combination time (∼1.5 s), low detection limit (8.8 nM), and minimal interference from other cations. Moreover, P showed good response performance when exposed to exogenous Cu²⁺ in both tap water samples and HeLa cells, offering a potential application value in real-world environmental monitoring and biomedicine. Furthermore, by integrating with smartphone-based color recognition programs, this dual-mode polymeric sensor not only expands the application boundaries of polyacrylamide in the field of fluorescence detection but also offers a feasible solution for the portable detection of Cu²⁺.