Programmable, fluorescent and shape-changing composite fibers for Fe³⁺ detection and filtration

Simultaneous detection and removal of excess Fe³⁺ is essential for ecological balance, food safety, and pathology, yet despite the promising stability of specific fluorescent functional materials, their conventional direct dispersion in aqueous solution causes structural instability, secondary pollution, and a lack of integration between detection and removal. To overcome these limitations, we developed a programmable, fluorescent, and shape-changing composite fiber for Fe³⁺ recognition, detection, and removal in a single platform. Composite fibers are prepared by combining fluorescent particles with thermally responsive fibers via electrostatic forces. The fibers have stable fluorescent properties and can detect Fe³⁺ with high selectivity and sensitivity. Upon thermal stimulation, it undergoes reversible shape programming and recovery, enabling a structural transition from random to aligned at the microscale. This smart structural modulation enhances specific surface area and pore distribution, thereby improving Fe³⁺ detection and adsorption capacity. The programmable fiber exhibits selective fluorescence quenching within 5 s and achieves up to 98 % Fe³⁺ removal efficiency through shape-changing composite fiber. Our work provides a novel and sustainable strategy for large-scale management, addressing the dual need for Fe³⁺ detection and filtration in modern smart water treatment systems.