A multicolor fluorescent sensor array based on curcumin and its analogs as a shrimp freshness indicator

The colorimetric sensing label is a simple, cost-effective, and user-friendly tool for monitoring ammonia vapor (NH3) concentrations in food packaging. Numerous natural dyes present excellent NH3-sensitivity, but their low solubility in water limits their food-related applications. Herein, a special cellulose-based ink system with an EtOH/water mixture as solvent was proposed to improve the dispersion of non-aqueous dyes (curcumin and its analogs (indexed as Bur and Bur-BF2)). Subsequently, three sensing labels containing different dyes were prepared by simple screen-printing after optimizing the inks' rheological properties. Benefiting from the different intramolecular charge-transfer (ICT) behaviors of dyes, each sensing label exhibited various characteristics in terms of the optical property, NH3-sensitivity, and fluorescent color-changing routes upon exposure to 0–50 ppm NH3. Importantly, all sensing labels showed excellent stability in environments with various relative humidity and temperature. Therefore, three sensing labels were used to construct a multicolor fluorescent sensor array, which aimed to visually monitor the freshness of shrimp for consumers.