Raspberry-shaped H-COF-based dual-mode fluorescent sensing probe for tetracycline antibiotics: standalone and electrospun mat-based point-of-care applications.

Two-dimensional fluorescent materials have emerged as promising candidates for applications in food safety, environmental monitoring, and disease diagnostics, particularly for point-of-care sensors. We report solvothermal development of an imine-linked 2D hydrogen-covalent hybridized organic framework (H-COF), DaTa-1, with novel raspberry-like morphology for the sensitive chemosensing of tetracyclines (TCs) in tap water and milk samples. The developed H-COF exhibited good thermal stability and strong fluorescence in aqueous suspension and in the solid state. DaTa-1 demonstrated excellent sensing performance for TCs (especially for 0.2-10 ppm and 12-60 ppm ranges), achieving low detection limits of 43.80, 46.42, 55.81, and 104.20 ppb for tetracycline, chlortetracycline, oxytetracycline, and doxycycline, respectively. Notably, the inner filter effect is primarily responsible for generating sensing signals. Furthermore, density functional theory (DFT) calculations suggested photoinduced electron transfer (PET) as an additional pathway contributing to dynamic quenching. To make the developed system more accessible, DaTa-1 was incorporated into polyacrylonitrile (PAN) nanofibers via electrospinning and used for the on-site and smartphone-assisted visual detection of TCs.