| In modern agriculture, the extensive use of pesticides has raised serious public concern regarding health, environment and food safety due to their high neurotoxicity. As a group of commonly used pesticides, organophosphates pesticides(OPs) can exert irreversibly inhibitory effect toward important enzymes in human body, such as acetylcholinesterase(ACh E), which causes long-term damage to livers even at very low dose. Therefore, the rapid determination and reliable quantification of OPs is paramountly important.In this paper, we designed and prepared the Zr O2 nanoparticle(Zr O2NPs) based electrochemical sensor for the detection of organophosphorus pesticides. A typical organophosphorus pesticide, Omethoate, was detected using Zr O2 NPs electrochemical sensor with optimized the experimental conditions. The calibration curve was obtained. The reproducibility, stability and selectivity of the sensor were studied. The experimental results are listed below.(1) Preparation of Zr O2 nanoparticle based electrochemical sensor(a) In order to ensure the binding between zirconia nanoparticles and the ITO electrodes, ITO electrodes were first modified with(3-aminopropyl)triethoxysilane(APTES), which is a strong linker for the Zr O2 NPs. It is important to clean the bare ITO electrode properly. Using cyclic voltammetry the conductivity of APTES modified electrode showed good conductivity, which is favorable to the deposition of Zr O2 NPs. A contact angle measuring instrument was used for optimizing time of the self-assembly.(b) Zr O2 NPs decorated APTES modified electrode(Zr O2NPs-APTES/ITO) was prepared by immersing APTES modified ITO electrode into an aqueous electrolyte solution containing 5.0 m M Zr OCl2 and 0.1 M KCl, and then scanning the potential between-0.9 and 0.5 V(vs. SCE) at a scan rate of 20 m V/s for 7 cycles at room temperature. The consequent electrodes were analyzed by SEM, EDS and Malvern laser particle size analyzer. The conductivity of electrode is measured in potassium ferricyanide solution by square wave voltammetry. Electrodeposition conditions are optimized by balancing the good conductivity and efficient solid-phase pesicide extraction.(2) Detection of Omethoate using Zr O2NPs-APTES/ITO electrode The Zr O2NPs-APTES/ITO electrode was immersed in different concentration OP solutions. OPs adsorbed onto the electrode surface via the strong affinity of Zr O2 NPs to phosphoric moieties, which caused the current decrease in square wave voltammetry measurements. The calibration curve was obtained by plotting the current decrease percentage against OP concentration using ORIGIN software. To build up the calibration equation for real sample detection, a linear fit was done. The corresponding fitting equation was I/I(%)= 97.8- 8.82 log C with R2 to be 0.99. A detection limit of as low as 11.2 ng/L Omethoate was obtained based on a signal-to-noise ratio of 3. The reproducibility of sensor is quite good, since the standard deviation is 8.1% among different Zr O2NPs-APTES/ITO electrodes. The peak current decreased 17% after 4 week monitoring. The nice selectivity of the sensor was confirmed by comparing the signal from Omethoate with other pesticides, such as methyl viologen, machete, thiamethoxam, and Chris and pyrazosulfuron. |
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