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Paraquat is a widely used herbicide for controlling weeds and grasses in agriculture, and its contaminated residues in agricultural areas are of increasing concern. This work reports the development of the sensitive and easy‐to‐use colorimetric aptasensor for screening paraquat residues in agricultural soil. The short DNA fragments derived from the original aptamer were analyzed for their capability to interact with paraquat by molecular dynamic simulation. The paraquat‐aptasensor was developed using the selected DNA fragment and gold nanoparticles. Its limit of detection (LOD) for paraquat is 2.76 nM, which is more sensitive than the aptasensor with long‐length aptamer (LOD = 12.98 nM). The developed aptasensor shows the selectivity to paraquat, but not to other tested herbicides; ametryn, atrazine, difenzoquat, 2,4‐D‐dimethyl ammonium, and glufosinate. The recovery rates of paraquat detection in the spiked soil samples were in a range of 99.5%–105.1%, with relative standard deviation values of <4%. The developed aptasensor was used to screen for paraquat residues in agricultural soils, and three out of 23 soil samples were tested positive for paraquat, which was confirmed by a high‐performance liquid chromatography analysis. These results suggested the potential application of the developed aptasensor to detect paraquat residues in agricultural sites. [ABSTRACT FROM AUTHOR]

The contamination of paraquat in vegetables is widely connected with human health risks, leading to the research interest in developing a paraquat sensing system. This work reports a simple detection method of paraquat based on the electrostatic interaction of paraquat and the negatively charged gold nanoparticles (AuNPs), resulting in the changes of colors from red to blue and the shifting of localized surface plasmon resonance (LSPR) peaks of AuNPs. The limit of detection concentration (CLOD) of this system was 100 μM paraquat. Moreover, among eight cationic salts tested, NaCl was selective to enhance the detection sensitivity of the system, resulting in the reduction of CLOD to 0.10 μM. This system selectively detected paraquat, but not other tested herbicides (ametryn, atrazine, glyphosate, and 2,4‐D‐dimethyl ammonium). The paraquat‐spiking experiment in kale demonstrated the significant recovery rate of paraquat at 96.0–103.0%, and the relative standard deviations were less than 4%. The developed system was efficient for screening contaminated paraquat in vegetables under unwashed and washed conditions. Three out of five unwashed vegetables had a significant level of paraquat as determined by LSPR values. These results suggested the potential application of this system for a simple screening of contaminated paraquat in vegetables. Simple paraquat‐screening system was developed based on the negatively charged gold nanoparticles.The limit of paraquat detection of this system was 0.10 μM.This system was potentially used for a simple screening of contaminated paraquat in vegetables. [ABSTRACT FROM AUTHOR]