Highly sensitive fluorescent turn-on lateral flow strip for chlorothalonil based on an indicator displacement ratiometric fluorescent assay

Nanomaterial based indicator displacement assays (IDA) have demonstrated interesting applications in chemosensing, however, restricted to fluorescence quenching nanomaterials. Fluorescent metal nanocluster (NCs) serving as a receptor in IDA may provide new sensing applications. In this work, we utilized GSH/CD-AuNCs as receptor and kaempferol/Al3+ complex (KAE/Al3+) as indicator to fabricate a new nanomaterial based IDA. Due to inner filter effect (IFE) and photoinduced electron transfer (PET) effect, the fluorescence of GSH/CD-AuNCs was greatly quenched by KAE/Al3+ complex. In the presence of chlorothalonil (CHL), CHL was more likely to enter the cavity than KAE/Al3+ due to its higher affinity with beta-CD, thereby restoring the AuNCs fluorescence. Meanwhile, the fluorescence of KAE/Al3+ could be greatly enhanced after beta-CD inclusion. Based on the above principle, an indicator displacement ratiometric fluorescent assay (IDRFA) for CHL was successfully constructed. Moreover, we integrated this IDRFA with lateral folw assay (LFA) format to develop a novel fluorescent turn-on IDA-LFA for CHL, which facilitated the naked eye discrimination and sensitive quantitative detection through LFA. Due to the advantages of rapid (completed within 1 min), and highly sensitive (even higher than some immunochromatographic strips), this novel IDA-LFA strip have high potential in rapid screening CHL.