A Colorimetric Sensor for Cyanide Ion Detection Using a Poly(TCDA)-Based Material Sensor

This study presents a colorimetric sensor for the rapid visual detection of highly toxic cyanide ions (CN^-) utilizing poly-(TCDA) assemblies and poly-(TCDA)/Zn²⁺/ZnO nanocomposites. The pristine polydiacetylene (PDA) and nanocomposites exhibit a distinct naked-eye observable color transition from a non-fluorescent blue phase to a highly fluorescent red phase upon exposure to CN^-. The incorporation of 0.5 wt % ZnO into the nanocomposites yielded optimal sensing performance, demonstrating a more rapid colorimetric response than pure PDA or nanocomposites with higher ZnO concentrations. The color change was visible to the naked eye when the RSC exceeded 50%, with a limit of detection for cyanide of 0.6 mM. The spectroscopic and structural characterizations reveal that CN^- intercalates into the PDA crystal, interacting with the carboxylate headgroups and inducing conformational changes in both the conjugated polymer backbone and the alkyl side chains. Furthermore, the fabrication of poly-(TCDA)-based hydrogel beads, particularly those with 0% and 0.5% ZnO, was successfully demonstrated as a practical platform for effective naked-eye CN^- detection.