Conjugated Polymer-Based Hydrogel Film for a Fast and Sensitive Detection of Fe(Ⅲ) in Vegetables

Fluorescent film sensors are ideal for the real-time outdoor detection of heavy metal ions of Fe³⁺, but they are limited because of their low sensitivity and long response time due to their special structure. In this work, we constructed a fluorescent hydrogel for the specific detection of Fe³⁺, utilizing poly(9-fluorenecarboxylic acid) (PFCA) as the sensing moiety and sodium alginate (SA) as the cross-linking substrate, which exhibited a rapid and selective recognition of Fe³⁺ among a panel of 16 anions and 21 cations. It can sense Fe³⁺ at 0.1 nM immediately owing to the porous network structure of the PFCA-SA film that provided enhanced ion transport channels and active sites, and the "molecular line effect" of polymer PFCA. Moreover, we successfully applied this platform to detect Fe³⁺ in four different vegetable samples. This work provides an innovative and effective strategy for fabricating green and sustainable fluorescent sensors.