From laboratory to outdoor: Construction of an integrated Fe3+ smart sensing platform and its agricultural applications

In the realm of food quality and safety monitoring, traditional on-site detection methods have faced challenges. Conventional sensors often lack the ability to provide rapid and accurate results, with limited sensitivity and selectivity. They are also bulky, making them inconvenient for portable applications. To address these limitations, we developed a smart sensing platform using 3D printing. By incorporating a fluorescent hydrogel of poly(9-aminofluorene) (P9AF) and sodium alginate (SA) as the cross-linking substrate, the platform’s P9AF-SA film has a porous network. This structure offers enhanced ion transport channels and active sites, enabling rapid and selective detection of Fe³⁺ ions among numerous anions and cations. A 3D printed smartphone-based readout device further enables portable detection. Our platform achieved a limit of detection (LOD) of 67.47 μg/L, far below the WHO safety threshold, and was successfully applied to agricultural products. This study not only provides a novel on-site detection device but also paves the way for developing highly efficient portable sensors, significantly advancing the field.