An N-oxide-BODIPY-based ratiometric NIR fluorescent probe for the selective and sensitive detection of ferrous ions in real samples†

Iron plays a crucial role in biological processes such as oxygen transport and maintaining cellular redox balance. However, an imbalance in its labile ferrous form (Fe²⁺) can cause oxidative stress and lead to various diseases. Detecting Fe²⁺ in complex environments requires advanced probes with high sensitivity, selectivity, and real-time monitoring capabilities. To address these challenges, we developed BDNO, a BODIPY-based N-oxide fluorescent probe that utilizes an N-oxide reduction mechanism for Fe²⁺ detection. BDNO exhibits dual fluorescence behavior in the presence of Fe²⁺ ions: a turn-on near-infrared (NIR) emission at 715 nm (λ_ex = 610 nm) with a large Stokes shift of 105 nm and a turn-off emission at 570 nm (λ_ex = 540 nm). The probe demonstrated excellent selectivity and sensitivity toward Fe²⁺, with a detection limit of 41 nM and a rapid response time of less than 5 seconds. Additionally, BDNO allowed for simple, visual detection of Fe²⁺ using paper strips and cotton buds and successfully detected Fe²⁺ in various real samples, including apple juice, orange juice, wine, tap water, river water, and seawater. The probe's fast response, high selectivity, and reliable sensing capabilities make it a promising tool for applications in food safety, environmental monitoring, and biomedical research.