Development of fluorescent sensing platform with degradable hydrogel for rapid and ultratrace detection of Cr(VI) in vegetables

Degradable fluorescent film sensors are highly ideal for real-time outdoor detection of heavy metal ions and offer the advantage of preventing secondary contamination, aligning with the principle of sustainable development. In this work, we constructed a degradable fluorescent hydrogel for the specific detection of Cr(VI) ions, utilizing poly(1-pyrene butyric acid) (PPBA) as the sensing moiety and sodium alginate (SA) as the cross-linking substrate. The porous network structure of the PPBA-SA film provided enhanced ion transport channels and active sites, thereby reducing fluorescence response time and augmenting detection sensitivity. The PPBA-SA film exhibited rapid and selective recognition of Cr(VI) ions among a panel of 16 anions and 22 cations, achieving an impressive limit of detection of 1.99 nM. Moreover, we successfully applied this platform to detect Cr(VI) ions in four different vegetable samples. Notably, the PPBA bound with Cr(VI) ions could be effortlessly removed from the film, and the substrate underwent rapid degradation within 24 h, attaining a degradation rate of 72.4 %. This work provides an innovative and effective strategy for fabricating green and sustainable fluorescent sensors.