Establishment Of Luminol Electrochemiluminescence Aptasensors And Its Application In Detection Of Diazinon Residues In Vegetables

Pesticides play an important role in ensuring the quality and yield of crops,but also bring potential threats to the ecological environment and human health.Organophosphorus pesticides are currently the most widely used and the largest amount of pesticides in China,the problem of excessive residues has become one of the major safety hazards of vegetables.Diazinon（DZN）is a kind of organophosphorus pesticide,commonly used in spinach,cabbage,lettuce and other vegetables.At present,there are mainly instrumental analysis methods such as liquid chromatography and mass spectrometry and liquid chromatography for the detection of DZN pesticide residues.These methods has high sensitivity,but requires specialized operators to operate and cannot meet the needs of rapid detection.Therefore,it is of great practical significance to develop an efficient and reliable rapid detection method for diazinon pesticide residues in vegetables.The electrochemiluminescence（ECL）method has the advantages of low background signal and fast detection speed,which provides technical support for rapid detection.Based on this,this study used highly specific aptamers as molecular recognition elements,combined with different nanomaterials and ECL to prepare low-cost and highly sensitive electrochemiluminescence aptasensors,and verified the feasibility of DZN residue detection in vegetables.The main study contents and results are as follows:（1）An electrochemiluminescent aptasensor based on three-dimensional flower-like zinc oxide materials（3D flower-like Zn ONPs）catalyzed luminol-hydrogen peroxide（luminol-H₂O₂）system was prepared for diazinon residue detection in vegetables.First,the conductivity and biocompatibility of gold nanoparticles（Au NPs）were utilized to carry luminol on the electrodes and enhance the conductivity of the electrodes.Secondly,3D flower-like Zn ONPs was synthesized by hydrothermal method as a co-reaction promoter for the luminescence system to accelerate the decomposition of H₂O₂ and enhance the ECL sensing signal.In addition,3D flower-like Zn ONPs with high porosity and large specific surface area were positively charged by polydiene dimethyl ammonium chloride（PDDA）to immobilize negatively charged aptamer.Under optimal conditions,the ECL sensor had a wide detection range（10 pg/m L～10μg/m L）and low detection limit（0.0109 n M（S/N=3））for detection DZN.The sensor was used for the actual sample detection of spinach and Chinese cabbage,and the recovery rate was 95.48%～120.22%.（2）In view of the defects of easy decomposition and instability of luminol’s co-reactant H₂O₂,an ECL aptasensor based on MWCNTs@MB and Cu₂O@Au NPs dual-catalyzed glucose in situ generation of H₂O₂ was prepared.MWCNTs@MB and Cu₂O@Au NPs have large specific surface areas,which increased the immobilization of luminol and aptamers on the electrodes,and also were used as double-effect catalysts for the production of H₂O₂ from glucose,which solved the problem that externally added H₂O₂was unstable and easily decomposed on the electrode surface,thereby improving the response signal of the sensor.Under the optimal experimental conditions,the linear range of the ECL aptasensor for detection DZN was 1 pg/m L～1μg/m L,and the limit of detection（LOD）was 1.28 p M（S/N=3）.The recoveries of samples spiked were 90.60%～114.82%.