Blue/red dual emission based ratiometric fluorescent intelligent labels for real-time food freshness monitoring

Fluorescent sensor technology is used in food safety to monitor seafood spoilage with the naked eye in real time due to its ease of operation, low cost and high degree of visualisation. Therefore, in this work, carbon quantum dots (CDs) as pH indicators and protoporphyrin IX (PpIX) as an internal reference were covalently grafted onto collagen fibres (CF) to design collagen fibre-based ratiometric fluorescent aerogels (CF-CP) with excellent amine response. As the alkaline environment causes a molecular conformational change in CDs and a decrease in fluorescence intensity, PpIX is unaffected, increasing its CF-CP colour response from blue to deep red with increasing ammonia concentration, with detection limits as low as 1.0 × 10−6 mg/L. CF-CP responds well to a wide range of biogenic amines (BAs), with the best selectivity for tyramine. In addition, the aerogel is biocompatible, degradable and colour responsive. The development of this smart fluorescent aerogel label provides a new platform for food quality monitoring and has wide application prospects in the field of food safety.