Self-assembly fluorescent copper nanoclusters in alginate-based hydrogel sensor for histamine detection and visual monitoring of food spoilage.

Histamine is one of typical biogenic amines related with foodborne illness induced by eating spoiled food. Thus, it is vital to establish a reliable and efficient approach for histamine detection and food safety monitoring. In this work, a ratiometric fluorescent sensor based on CuNCs/SiQDs and CuNCs/SiQDs-alginate hydrogel test strip were established for histamine detection and fluorescent visual monitoring of food spoilage. Due to fluorescent spectrum of SiQDs overlaps obviously with the UV-vis absorption spectrum of CuNCs, which indicates sensing mechanism of this sensor may be fluorescent inner filter effect (IFE). The fluorescence of CuNCs would be quenched by histamine. With histamine level arising, the fluorescence peak of CuNCs decreases and SiQDs increases gradually, which realize the fluorescent ratiometric detection of histamine. The proposed sensor shows a good linear correlation between fluorescence ratio (F615/F437) and histamine concentration in the range of 0.4-7 mM with a detection limit of 16.6 μM. Moreover, a novel CuNCs/SiQDs-alginate hydrogel test strip by integrating with smartphone is designed for fluorescent visual monitoring of spoiled process of aquatic products. The as-prepared sensor and test strip are successfully exploited for histamine detection in food samples and visual monitoring spoiled process of foods.