Dual-signal optical detection of Lead(II) ions (Pb²⁺) using galloyl group-functionalized polydiacetylene

In this study, we developed a novel galloyl group-functionalized polydiacetylene (Galloyl-PDA) sensor for colorimetric and fluorescent detection of Pb²⁺. Among three types of Galloyl-PDA vesicles prepared by changing the ratio of newly synthesized galloyl group-conjugated 10,12-pentacosadiynoic acid (Galloyl-PCDA) and matrix 10,12-tricosadinoic acid (TCDA), the blue Galloyl-PDA vesicles with 1:9 molar ratio of Galloyl-PCDA:TCDA showed the most dramatic color transitions to red with colorimetric response (CR) value of 46.66 ± 1.373% within 5 min upon addition of 50 μM Pb²⁺. However, they didn't exhibit any color change upon interaction with other heavy metals. Since the terminal galloyl moieties of the Galloyl-PDA vesicles could form coordination bonds with Pb²⁺, the Galloyl-PDA vesicles were stressed and showed obvious blue-to-red chromatic transitions. Besides, because the Galloyl-PDA vesicles exhibited nonfluorescent-to-fluorescent transitions, a linear response in colorimetric and fluorescent signals was observed in the range of 0-10 μM and 0.025-1 μM, respectively. From the colorimetric and fluorescent results, the limit of detection (LOD) was determined to be 1.329 μM and 0.068 μM, which is 8-fold and 12-fold better sensitivity than those of previously reported methods, respectively. Furthermore, the capability of our PDA sensor for detection of Pb²⁺ in tap water, river water, and human serum was validated with excellent precision and recovery rates of 97.14-100.0%, 99.05-103.3%, and 100.7-106.7%, respectively. As our PDA dual-signal sensor for Pb²⁺ is rapid, sensitive, specific, and detectable by the naked eye, this approach holds great promise for application in point-of-care testing (POCT).