Bimetallic Ag2CrO4 nanoparticles with dual-enzyme-mimic activities in colorimetric sensor for sensitive and highly selective detection of dimethoate in vegetables

Colorimetric methods have the benefits of rapid detection and easy operation in dimethoate (DMT) analysis. However, the existing colorimetric sensor for DMT detection still face challenges in terms of performance stability and result reliability of sensing materials. Bimetallic Ag 2 CrO 4 nanoparticles (NPs) have been found to have both oxidase-mimic and laccase-mimic catalytic activities. DMT has opposite effect on the above dual-enzyme-mimic activities, which can enhance oxidase-mimic activity while inhibiting laccase-mimic activity of Ag 2 CrO 4 NPs. Therefore, a novel colorimetric sensor was constructed using the dual-enzyme-mimic activities as a sensing signal for rapidly detecting DMT in vegetables. The concentration of DMT is directly correlated with the absorbance change of the sensing solution, and the color change is further integrated with the smartphone to enable quantitative measurement of DMT. The limits of detection were as low as 8.7 μg L −1 in the oxidase-mimic channel and 10.9 μg L −1 in laccase-mimic channels. Besides, the colorimetric sensor has shown marked preference in selectivity over other competing pesticides, and obtained relatively preferable recovery rates in some vegetables, indicating that the established sensor has a wide range of potential applications in the area of vegetable pesticide detection.