A stimulus-responsive activatable fluorescent probe for detection of propyl gallate using PEI-modified...

Propyl gallate (PG) is a common phenolic antioxidant added in food, and its overconsumption brings potential health hazards. Herein, a stimulus-responsive activatable fluorescent probe Mn-TCPP@PEI was constructed via PEI modification of porphyrin-based MOF. PEI modification red-shifted the fluorescence emission and enhanced the fluorescence intensity of Mn-TCPP. As a stimulus, PG was oxidized to quinones and further reacted with PEI through Schiff base reaction. This process activated new blue fluorescence at 497 nm and quenched the red emission at 678 nm. A ratiometric fluorescence method was established for PG detection with a linear range of 0.1-100 μM and a detection limit of 30 nM. A smartphone RGB visual strategy also achieved reliable detection performance in the linear range of 1.0-100 μM with a detection limit of 79 nM. The probe possessed good stability, selectivity, and anti-interference. It was successfully applied to PG analysis in real food samples with satisfactory recoveries and low RSD, offering a promising platform for PG monitoring in food.