Terbium alginate encapsulated CsPbI3@Pb-MOF: a ratiometric fluorescent bead for detection and adsorption of Fe3+

Halide perovskite nanocrystals are innovative luminescent materials for fluorescent probes with high quantum yield and narrow emission bandwidth. However, the limited stability, single-signal response, and separation challenges obstruct their widespread use in water ion detection. Herein, a ratiometric fluorescence sensor based on terbium alginate gel beads (green fluorescent, namely Tb-AG) embedded with powdered CsPbI₃@Pb-MOF (red fluorescent) was prepared for fluorescent determination and adsorption of Fe³⁺. Pb-MOF's protection notably enhances the water stability of CsPbI₃, while the energy transfer between CsPbI₃@Pb-MOF and Tb³⁺ elevates the optical performance of CsPbI₃@Pb-MOF@Tb-AG. Significantly, Fe³⁺ markedly suppresses CsPbI₃@Pb-MOF red fluorescence at 647 nm, while not noticeably affecting Tb-AG green emission at 528 nm. The sensor exhibited a strong linear response to Fe³⁺ concentrations ranging from 0 to 90 μM, with a detection limit of 0.44 μM and high selectivity. The CsPbI₃@Pb-MOF@Tb-AG-based sensor has been effectively validated through its successful use in detecting Fe³⁺ in tap and river water samples. Furthermore, CsPbI₃@Pb-MOF@Tb-AG demonstrates a notable adsorption capacity of 325.4 mg g^-1 Fe³⁺. Finally, the mechanism of Fe³⁺ detection and adsorption was determined.