Multi-cycle colorimetric and fluorescent bimodal detection of low concentration ammonia by spiropyran-modified cotton fabric.

Real-time detection of ammonia is a critical concern in food safety and industrial production. However, traditional ammonia detection methods exhibit several inherent limitations, including slow response, high costs, and low sensitivity. In this study, a novel spiropyran-modified cotton fabric (LBNH-fabric) based on a cellulose matrix was developed for NH3 sensing with a low detection limit of 1.66 ppm, high sensitivity (rapid response in 6 s), and exceptional cycle stability (stable performance for over 70 cycles and 60-day storage). This is achieved through a three-dimensional network structure composed of multi-layered stacked hydroxyl groups and uniformly distributed spiropyran molecules. Density functional theory (DFT) computations elucidate the NH3 sensing pathway, revealing proton transfer as the key mechanistic step. The innovative spiropyran-modified cotton fabric is not only utilized in detection of seafood products freshness but also shows promising potential in food production, industrial safety, and environmental monitoring, thereby offering new avenues for research into NH3 sensing materials.