Fast and Visual Detection of Biogenic Amines and Food Freshness Based on ICT-Induced Ratiometric Fluorescent Probes

Biogenic amines (BAs) are important indicators for the evaluation of food spoilage and disease diagnosis. Thus, the detection of BAs with high practical potential is of great importance. In this work, a new BAs fluorescent probe design strategy is proposed by the intramolecular charge transfer (ICT) enhancement of the fluorescent probes, which is induced by the hydrogen bond interaction between probes and analyte. The probes T1 and T2 with donor-acceptor structure not only present a 140 nm bathochromic-shifted emission, ultrafast responses (15 s for T1 and 25 s for T2), and high sensitivity (detection limit of 1.3 ppm for T1 and 2.6 ppm for T2) to cadaverine (the typical representative of BAs) but also discriminate a series of BAs and simply reused at least 30 times after air blowing. Further, a quantitative evaluation system is obtained based on T1 and T2 films. Through the Red/Green/Blue analysis with a smartphone, the total volatile basic nitrogen (an international standard to assess food spoilage) value can be output to quantitatively evaluate the freshness of food. The system is fast, visual, accurate, and non-destructive, enabling consumers and all stakeholders in the food supply chain to monitor food freshness.