Solid-Phase Coassembly of Polydiacetylene and Azo Dye Exhibiting Green-to-Orange Transition for VOC Sensing

The distinctive blue-to-red chromatic transition of polydiacetylenes has been greatly employed for the generation of colorimetric sensors for many chemically and biologically important analytes. However, very few efforts have been dedicated to the development of color-tunable polydiacetylenes. Herein, we report the design and development of a polydiacetylene-based solid-phase sensor with a unique green-to-orange chromatic transition. The sensor was developed by comixing 10,12-pentacosadiynoic acid (PCDA) with aniline yellow, a commercial aromatic azo dye, and coating it on strips of filter paper. The coassembly of azo dye and PCDA offers a green color upon UV irradiation (254 nm), and it displays the expected colorimetric transition under temperature and pH change, indicating that PCDA retains all its chromatic properties in the solid phase. These PCDA:azo strips were capable of detecting a series of different classes of VOCs, such as chlorinated solvents, hydrocarbons, and ethers, by green-to-orange chromatic changes, indicating their high potential as a VOC sensor. The normalized intensity plot from ImageJ showed that the strips detected common VOCs in under 1 min, indicating a quick response. The PCDA:azo strips also displayed better stability and sensitivity than the PCDA strips. The PCDA:azo strips were also able to detect VOCs released in real samples, such as primers and rotten meat, signifying their real-world applicability.