Deep learning-assisted smartphone-based portable and visual ratiometric fluorescence device integrated intelligent gel label for agro-food freshness detection.

Here, a smartphone-assisted dual-color ratiometric fluorescence smart gel label-based visual sensing platform was constructed for real-time evaluation of the freshness of agro-food based on the biogenic amines responses. Green-emission fluorescence carbon dots (CDs) coupled with blue-emission fluorescence bimetallic metal-organic framework (Fe/Zr-MOF) obtained dual-color CDs@Fe/Zr-MOF fluorescence nanoprobe acts as the response units. With the increase of SP and HIS content, the green fluorescence of CDs was enhanced, while the blue fluorescence of Fe/Zr-MOF was quenched. Therefore, this dual-color probe achieved a clear fluorescence color response to biogenic amines. The nanoprobe possessed sensitive and color-responsive with the LODs of 0.17 μM for SP and 2.95 μM for HIS in a wide range of 0-937.5 µM, respectively. Besides, these fluorescent nanoprobes were immobilized on the hydrogel carrier, and the intelligent fluorescent hydrogel tag can be obtained after freeze-drying, which realizes the real-time qualitative monitoring of SP and HIS in pork and shrimp samples.