Ultrasensitive fluorescence sensor for Hg in food based on three-dimensional upconversion nanoclusters and aptamer-modulated thymine-Hg-thymine strategy.

Mercury (Hg) is a potentially toxic heavy metal ion found to be drastically deleterious to humans. Herein, an ultrasensitive fluorescence sensor was developed using three-dimensional upconversion nanoclusters (EBSUCNPs) and aptamer-modulated thymine-Hg-thymine strategy. The EBSUCNPs were used as the energy donors, the PDANPs served as the acceptors, and the aptamer was applied as an identification tag for Hg. Due to the energy transfer effect, the fluorescence of EBSUCNPs can be effectively quenched by Polydopamine nanoparticles (PDANPs). In the existence of Hg, T (thymine)-rich aptamers between EBSUCNPs and PDANPs were hybridized with Hg to yield thymine-Hg-thymine and folded back to hairpin structure, causing PDANPs to detach from the EBSUCNPS and the recovery of fluorescence. Under optimum conditions, the linear sensing range of Hg was 0.5-20 µg/L, and the detection limit was 0.28 µg/L. Furthermore, it exhibited excellent selectivity and anti-interference, which made it an ideal method for identifying Hg in spiked samples.