A fluorescence probe based on blue luminescent carbon dots for sensing Fe³⁺ in plants

Iron is an essential nutrient for plants and plays a crucial role in many physiological processes. Achieving sensitive, rapid, and real-time sensing of Fe3+ within plant organisms using carbon dots remains an intriguing research challenge. In this study, blue-emitting carbon dots (B-CDs) with an average size of 2.22 nm were synthesized through a hydrothermal reaction of sodium citrate and glutathione. The B-CDs exhibited low cytotoxicity and demonstrated high sensitivity and selectivity in fluorescence response toward Fe3+. Experimental evidence indicated that the phenolic hydroxyl groups on the surface of B-CDs formed ground-state complexes with Fe3+, and static quenching was the main quenching mechanism. Furthermore, as a biophotonic probe, B-CDs entered plant organisms during the process of water absorption and accumulated in the vascular bundles, enabling the visualization of Fe3+ sensing. This work successfully achieved Fe3+ sensing within plant organisms using carbon dots, laying a foundation for future applications of carbon dots in visual sensing within plants.