A dual-emission ratiometric fluorescence strategy with enzyme-based inhibition for organophosphorus pesticides determination

A fast, eco-friendly and accurate ratiometric fluorescent strategy is presented for the determination of organophosphorus pesticides (OPs) using intrinsic dual-emission silica nanoparticles modified with Rhodamine 6G (SiNPs-Rho6G). SiNPs-Rho6G had intrinsic dual-emission at 410 and 550 nm. The substrate acetylcholine was catalyzed by acetylcholinesterase (AChE) to produce thiocholine (TCh). TCh triggered the specific reaction of Ellman's reagent 5, 5-dithiobis (2-nitrobenzoic acid) to obtain 5-thio-2-nitrobenzoic acid, which caused the decrease in fluorescence intensity of SiNPs-Rho6G at 410 nm by the inner filter effect, while the fluorescence intensity of SiNPs-Rho6G at 550 nm was not significantly changed. OPs caused the recovery of the fluorescence at 410 nm by inhibiting the activity of AChE. Thus, the quantitative detection of OPs could be achieved through utilizing the catalytic characteristic of AChE. The linear curve from 0.010 to 0.250 μg mL^-1 with a detection limit of 7 ng mL^-1 was obtained for the determination of chlorpyrifos (Cpf). The ratiometric probe was used to detect the spiked Cpf in environmental and food samples with good recoveries. Therefore, combined with the dual emission characteristics of SiNPs-Rho6G and the specificity of the enzyme, the ratio fluorescence sensing platform has potential application prospects in OPs determinations. Graphical