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

Abstract

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).