Polythiazolidinones by MALI polymerization with red fluorescent emission and specific detection to Co2+ ions

The red fluorescent polymers are indispensable but rare materials in the bio-imaging, probe and optoelectronic device fields due to the large penetration depth in tissues, high resistance to photobleaching, low toxicity and high luminescence efficiency. In this study, we designed an O/N/S-containing five-membered thiazolidinone as a “potential chromophore” to embed in macromolecular chains according to cluster-triggered emission (CTE). A series of polythiazolidinones (PTDs) were synthesized by one-step MALI polymerization using dialdehyde, diamine, and thioglycolic acid in the experiment. As expected, PTDs showed the enhanced red fluorescence emission at 600–620 nm with excitation-dependent fluorescence (EDF) due to the overlap of intramolecular and intermolecular electron clouds leading to the narrowed energy gap between the excited and ground states. Notably, PTD-A selectively recognized and detected Co 2+ ions even in the presence of 12 other metal ions and 10 anions with the detection limits of as low as 0.24 μM. Furthermore, the quenching mechanism of Co 2+ to PTD-A is attributed to static quenching caused by the coordination of Co 2+ ions with a coordination ratio of 1:1. In addition, the rapid on-site determination of Co 2+ in the real samples was achieved by the combination between PTD-A and smartphones without professional equipment. In brief, the successful preparation of polythiazolidinones provides a constructive reference for the molecular design of red light-emitting materials and their potential applications.