Reliable and nondestructive monitoring of food quality is of great importance in sustaining life and promoting good health. Herein, we developed sensitive, fast, reversible, and nanometer-thick fluorescent films for the nondestructive evaluation of fish freshness. The nanofilms were prepared via the dynamic condensation of tetraphenylethylene derivative (TPEBA) with Calix[4]pyrrole derivative (CPTH) at the humid air/DMSO interface. The amorphous nanofilm is uniform with the thickness in the range of 12∼58 nm. Owing to the aggregation-induced emission (AIE) property of TPEBA, the nanofilm is highly emissive with a Stokes shift of ∼175 nm. The typically designed chemical composition and nanostructure endow the film-preferable affinity to amine vapors, and the networked structure allows fast mass transfer, which lays foundation for high-performance sensing. With an optimized nanofilm-based sensor, biogenetic amines were sensitively, selectively, and reversibly detected. The detection limit (DL) for trimethylamine (TMA) is 0.89 ppm. Typically, interference from water can be neglected; thus, the nondestructive evaluation of fish freshness was realized. Moreover, a portable seafood freshness detector was conceptually built.

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Film-based fluorescent sensors have been adapted into portable devices for the vapor phase detection. The satisfactory sensing performance (e.g., sensitivity, selectivity, reusability) largely benefits from fluorophores. Here we report a new nonplanar perylene monoimide derivative (PMI-CB) and demonstrate its application in a miniaturized film-based fluorescent sensor for BTX (i.e., benzene, toluene, xylene) detection. The fluorophore of PMI-CB is obtained through incorporating a three-dimensional o-carborane with the perylene monoimide (PMI). Compared to a planar PMI derivative (PMIA), the nonplanar PMI-CB with reduced intermolecular aggregation exhibits enhanced fluorescence intensities in both solvents and film state. The PMI-CB film exhibited fluorescence enhancements for BTX, while fluorescence quenching for commonly interfering compounds like ethanol, triethylamine, and acetone. Such opposite response behavior endows the PMI-CB-based sensor with the ability for selective detection of BTX. Importantly, our PMI-CB film is not sensitive to water. The sensitivity test shows that the PMI-CB film can detect benzene vapor at a concentration of as low as 3.3 mg/m 3 without any preconcentration procedures, and exhibits a good linear relationship from 3.3 to 425.9 mg/m 3 . On the basis of this work, a portable detector with high selectivity, sensitivity, reusability, and low power consumption can be adapted for the on-site BTX detection.