Pyrene derivative based fluorometric smart tags for shrimp freshness monitoring via a smartphone

) was doped into a hydrogel matrix to produce a smart tag. Benefiting from the nanometer-scale pore of the hydrogel, PY-Py's strong photostability, and its hydrophobic conjugated architecture, the dye-doped tag retained stable fluorescence signals after one month of storage, demonstrating excellent practical applicability. The smart tag detects volatile amines through changes in fluorescence ratio, showing a linear response to ammonia in the 10-70 ppm range and a limit of detection (LOD) of 3.28 ppm. Based on the tag's response to volatile biogenic amines and the standard total volatile basic nitrogen (TVB-N) method, freshness evaluation of shrimp can be performed either by direct visual inspection or smartphone-based analysis. This work provides a simple and convenient assay for volatile amines and for assessing shrimp freshness.