Carbon dots grafted polyvinylidene fluoride and sodium alginate composite membrane for fluorescent detection of Fe3+ ions

Ferric ion (Fe 3+ ) detection in biological and aqueous systems demands sensitive and rapid analytical tools. Although carbon dots (CDs) serve as effective fluorescent probes for Fe 3+ , CDs-based membrane sensors combining fast response with high sensitivity remain underdeveloped. We engineered a CDs-grafted polyvinylidene fluoride/sodium alginate composite membrane (CD- g -PVDF/SA) via phase inversion and surface grafting for Fe 3+ monitoring. The membrane demonstrated linear fluorescence quenching proportional to Fe 3+ concentration to 600 μM (R 2  = 0.995) with a detection limit of 0.10 μM. Significant quenching occurred within 1 min, facilitated by the porous architecture and carboxyl-rich surface that enhanced Fe 3+ accumulation through chelation. This enabled rapid electron transfer from CDs to bound Fe 3+ . The sensor showed Fe 3+ selectivity against interferents in complex matrices, including real water samples. EDTA-mediated Fe 3+ elution fully restored fluorescence, confirming reusability for over fifity cycles. CD- g -PVDF/SA membranes thus offer a robust platform for reliable Fe 3+ detection in environmental and biological applications.