A flexible all-in-one carbon-based electrode based on COF for sensitive detection of thiabendazole on fruit surfaces

The rapid, in-situ detection of fungicide residues on fruits is critical for food safety. However, conventional methods often involve complex operations and poor portability. Here, a covalent organic framework (COF) synthesized from 4,4',4″-(1,3,5-triazine-2,4,6-triyl) tris[benzaldehyde] (TTB) and 3,3'-dihydroxybenzidine (DHB) was grown on carbon paper (CP) to prepare COF_TTB-DHB@CP. Subsequently, COF_TTB-DHB@CP was assembled with Ag/AgCl and carbon black to fabricate the COF_TTB-DHB@flexible all-in-one electrode (FAE). Benefiting from electron-rich property of TTB, and excellent electrical conductivity of CP, the COF_TTB-DHB@FAE sensor enables rapid, sensitive, and efficient in-situ detection of thiabendazole (TBZ), with a sensitivity of 0.0216 mA cm^-2 μM^-1 and a limit of detection (LOD) as low as 0.15 μM. Integrated with a portable analyzer and smartphone via Bluetooth, it enables in-situ detection of TBZ and real-time remote monitoring. This work provides a novel strategy for developing flexible electrode sensors for fungicide in-situ detection.