Polydiacetylene-based sensor for highly sensitive and selective Pb²⁺ detection

Polydiacetylenes (PDAs), as smart materials with very unique properties, are widely used for sensing various analytes. Derived from the monomers 1-(1,4,7,10,13-pentaoxa-16-aza-cyclooctadec-16-yl)-pentacosa-10,12-diynamide (PCDA-L) and 10,12-pentacosadiynoic acid (PCDA), we report a conjugated polymer (poly-PDA-L) for lead ions detection. The PDA sensing system showed rapid fluorescent and colorimetric response and high sensitivity to Pb²⁺ in 100% aqueous solution, as well as the color change was obvious to the naked eye. Excellent fluorescence response change and a good linear relationship between fluorescent PDA intensity and Pb²⁺ amount were observed based on fluorescence microscope images, with a detection limit of 1 μM. The fluorescent and colorimetric responses were attributed to the binding between the moiety 1-aza-18-crown-6-ether of poly-PDA-L and Pb²⁺. This interaction further disturbs the backbone of the PDA polymer, allowing the release of the strain energy imposed on the alkyl side chains generated during polymerization, leading to the observed change in optical properties.