Synthesis of polydiacetylene/Zn^2 + /ZnO nanocomposites in alcohols for colorimetric detection of temperature and fatty acids

Colorimetric sensors fabricated from polydiacetylene (PDA) materials have been applied in many technologies. The syntheses of PDAs have often performed in an aqueous medium that presents an obstacle for some applications. This contribution demonstrates that PDA/Zn²⁺/ZnO nanocomposites with reversible thermochromism can be synthesized in a series of linear alcohols. The obtained nanocomposites exhibit a ribbon-like structure with a submicron width while the length grows longer than 30 μm. Compared with the nanocomposites synthesized in a water, this morphology is rather different, indicating the significant role of solvent media on the self-assembly. The use of alcohol as a solvent enables simple mixing of the nanocomposites with various polymers i.e., polystyrene, polymethyl methacrylate, polyethylene succinate, and polypropylene carbonate, expanding their applications as smart coatings and reversible colorimetric thermal sensors. Various reversible thermochromic colors for producing temperature-responsive paintings can be prepared by mixing with commercial acrylic paints. Furthermore, the nanocomposites synthesized in alcohols can be used for direct colorimetric sensing of cis-fatty acids (oleic acid, linoleic acid) and saturated fatty acids (stearic acid, palmitic acid). With the addition of cationic surfactants, fine tuning of the sensitivity to fatty acids can be achieved. Interestingly, the changes in structure and concentration of the cationic surfactants cause systematic variation of the sensitivity. The synthetic approach in this study is versatile and low-cost, showing potential for industrial-scale applications.