A cucurbit[6]uril-based supramolecular assembly as a sensitive fluorescent Sensor for detecting sunset yellow in...

Employing 1,3,5-benzenetricarboxylic acid (H₃BTC) as a structure-directing agent, a novel three-dimensional supramolecular framework, {[NH₂(CH₃)₂][Zn(BTC)(H₂O)]·(CB (Cai et al., 2019 [6]))_0.5·4H₂O}_n (CB[6]-BTC-Zn), was successfully constructed via a solvothermal reaction involving cucurbit[6]uril (CB (Cai et al., 2019 [6])), H₃BTC, and Zn(II) ion. CB[6]-BTC-Zn emits intense blue fluorescence and exhibits remarkable structure stability in aqueous media; and further it functions as an efficient turn-off fluorescent sensor, enabling highly sensitive and selective detection of a food colorant sunset yellow (SY) with a limit of detection as low as 8.48 × 10^-7 M. CB[6]-BTC-Zn can maintain excellent performance even in the presence of some food additives, showcasing its good anti-interference capability. The underlying mechanism for sensing SY involves a synergistic three-step process, an initial electrostatic enrichment of anionic SY molecules on the positively charged assembly surface, following an efficient fluorescence resonance energy transfer process facilitated by significant spectral overlap, and ultimately, a dual-channel photoinduced electron transfer (PET) pathway encompassing both donor and acceptor PET process, as confirmed by the density functional theory calculations. Furthermore, this material was processed into flexible sensing films and functionalized LED devices to achieve a visual SY identification, and it also was successfully applied to the spiked recovery detection of SY in actual beverage samples (recovery rates: 95.43-105.62%). This work offers a strategy for designing cucurbituril-based functional materials for rapid monitoring colorants in the field of food safety.