Rapid detection of organophosphorus in tea using NaY/GdF4:Yb, Er-based fluorescence sensor

In this study, a novel fluorescence approach for the rapid and selective detection of organophosphorus pesticides is presented. The strategy is based on inhibition of acetylcholinesterase (AChE) activity and NaY/GdF 4 :Yb, Er up-conversion nanoparticles (UCNPs) fabricated with manganese dioxide (MnO 2 ) nanosheets. Water-soluble UCNPs were first synthesized, and MnO 2 nanosheets were fabricated on their surface to get an efficient quencher for up-conversion fluorescence. Subsequently, AChE was used to restore the fluorescence by dissociation of MnO 2 nanosheets from the surface of UCNPs. When diazinon was added into the system, AChE activity was irreversibly impeded and resulted in the quenching of fluorescence. The inhibitory effect was linearly dependent on the concentration of the pesticide. Under the optimized conditions, the proposed sensor showed excellent performance for the detection of diazinon with a wide detection range of 0.1 to 30 ng/mL and a low detection limit (LOD) of 0.1 ng/mL. Besides, the system showed a good selectivity and was applied for diazinon detection in adulterated tea samples with a recovery rate of 98% to 111%. The unique advantages of the strategy such as simple, cost-effective, highly selective and sensitive make it an attractive approach for the detection of OPs in tea commodities.