MXene catalytic amplification-fluorescence/absorption dimode aptamer sensor for the detection of trace Pb in milk.

Lead ion (Pb) is a toxic heavy metal, which is very harmful to organisms. Therefore, the establishment of a rapid, simple, and sensitive method is of great significance to food safety and human health. It was found that MXeneTiC nanosheet (NS) has a strong catalytic effect on the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) HO to form the oxidized product (TMB); it has a strong fluorescence peak at 415 nm and an absorption (Abs) peak at 295 nm. The aptamer of Pb (Apt) can be adsorbed on the surface of an NS to form MXene-Apt conjugates, which reduces its catalytic active sites and inhibits its catalytic activity. When the target Pb is added, it specifically binds with Apt to release MXene NSs to enhance the dimode signals. Therefore, a new MXene catalytic fluorescence/absorption dimode aptamer biosenering platform was fabricated for the determination of trace Pb in milk and water samples, with the fluorescence assay linear range (LR) of 5.0 × 10-2.0 nmol/L.