| Pesticides are heavily used in agricultural production,it has effectively reduced the food loss caused by pests and diseases.Besides,it increased food production.However,this causes pesticide residues in the environment and diet posing a great threat to human health.There are risks of cancer,malformation,endocrine disorder,resistance to drugs.In order to protect the ecological environment and food safety,many countries make relevant laws and regulations to strictly limit pesticide residues in the environment,especially in food.Detection of pesticide residue is a key step for monitoring pesticide residues.It becomes research hotspot both in home and abroad.Gas chromatography?GC?,liquid chromatogram?LC?,gas chromatography-mass spectrography?GC-MS?,liquid chromatography-mass spectrometry?LC-MS?and immunoassay are routine methods for detecting pesticides.But these methods have inherent limitations,such as expensive equipment,inconvenience to carry,a longer testing cycle,and so on.To overcome these shortcomings,photochemical and electrochemical methods arouse the attention of researchers.Photochemical and electrochemical methods have advantages such as high sensitivity,good stability,small equipment,easy to carry.The preparation procedure is simple and easy to operate.These methods can be used for real-time testing.Because many pesticides do not have electrochemical activity,the detections of them need to introduce electroactive material to produce electrochemical signals.Pesticide aptamers are often used in photochemical and electrochemical sensors due to their good specificity and stability.This can improve the recognition of photochemical and electrochemical sensors towards corresponding pesticide,and greatly improve the selectivity of sensors.The purpose of this paper is to use the excellent properties of electroactive substances,the specificity and stability of the adaptor for researching highly sensitive photochemical and electrochemical sensors to detect pesticide residues of PMG and acetamiprid.Here are the main research contents and results:1.The study of PMG electrochemical sensor with nitrite as signal molecule.Nitrite has electrochemical activity,it could react with PMG by substituted active hydrogen on the-NH-of PMG under acidic condition.Nitrite is consumed in the reaction,and its oxidation peak current decreases.Based on the above,electrochemical sensors used to quickly detect PMG can be designed.Multiwalled carbon nanotube?MWCNTs?and reduced graphene oxide?rGO?were used to synthesis composite MWCNTs/rGO.MWCNTs/rGO was used to modify glassy carbon electrode?GCE?.Both MWCNTs and rGO have good electron transfer capability,this can enhance the catalysis of the modified electrode toward the oxidation of nitrite.The mixture containing 1.0×10-4mol/L NO2-,1.0×10-3mol/L KCl and 1.0×10-3mol/L HCl was used as base solution,MWCNTs/rGO/GCE was used as working electrode,Pt electrode was used as counter electrode,and Ag/AgCl electrode was used as reference electrode to detect Glyphosate.Under optimum detection conditions,the linearity range of this sensor for Glyphosate was 1.0×10-131.0×10-4mol/L,and the detection limit was 3.3×10-15mol/L.This sensor has advantages such simple preparation steps,high sensitivity and wide linearity range.This sensor shows broad prospects in the field of determination of pesticide residues by using nitrite as signal molecule.2.Study on the colorimetric detection technology of PMGphosate.O-phenylenediamine?OPD?does not itself have color,could be oxidized into 2,3-diaminophenazine by Cu2+and turn yellow.This is because that carboxyl in the PMG would form chelate with Cu2+.It will inhibit oxidation of Cu2+to OPD,and inhibit the color change of OPD.The achieved solution was measured by fluorescence spectrometer and ultraviolet spectrophotometer respectively,the spectral intensity was used as evidence for the detection of PMG concentration.Under optimum detection conditions,the linearity range of this sensor for PMG was 1.0×10-81.0×10-6mol/L,and the detection limit was 3.3×10-9mol/L.This experiment also explored the interference effects.It turned out that,the detection method established in this experiment has good selectivity for PMG.In addition,this experiment is low-cost and easy to operate.3.An electrochemical sensor for PMG was constructed based on the aminochemical mesoporous silicon.SBA15 was synthesized and modified by amination to obtain NH2-SBA15.NH2-SBA15 has large surface area,good adsorption capacity and good electrocatalytic performance.These advantages were utilized to prepare carbon paste electrode?CPE?.Because of the introduction of Cu2+,the sensitivity of this sensor was notably improved.High sensitive detection of Glyphosate was realized by this sensor.Under optimum detection conditions,the linearity range of this sensor for PMG was 1.0×10-121.0×10-5mol/L,and the detection limit was 5.0×10-13mol/L.This electrochemistry sensor has good stability,high sensitivity,wide linearity range and good selectivity.4.Electrochemical aptasensor based on MSFs modified electrode was designed for determining acetaniprid residues.Indium tin oxide?ITO?was dealt with alcohol and NaOH in sequence.Vertically ordered mesoporous silica films?MSFs?directly grow on the ITO,and the MSFs were modified by amination,NH2-MSFs/ITO was obtained.NH2-MSFs/ITO was immersed in methylene blue solution,and methylene blue molecules were loaded in the holes of MSFs.Because of electropositivity of NH2 and electronegativity of acetamiprid aptamer,the acetamiprid aptamer was attracted to NH2-MSFs/ITO.Acetamiprid aptamer covered the top of the holes of MSFs.Incubation with different concentrations of the acetamiprid,when the concentration of the acetamiprid increased,aptamers removed for the pairing between acetamiprid and aptamer would increase too.Methylene blue molecule released from the holes of NH2-MSFs increased.The residual methylene blue molecule in the holes of NH2-MSFs reduced,the electrochemical signal reduced.Thus,acetamiprid electrochemical aptasensor was fabricated.Under optimal conditions,linearity range of acetamiprid detection was 1.0×10-131.0×10-8mol/L,and the detection limit was 3.33×10-14mol/L.This aptasensor significantly improved the selectivity due to the introduction of acetamiprid aptamer.Furthermore,this aptasensor showed excellent stability and high sensitivity.This sensor obtained satisfactory results,when it was used to detect practical samples.5.Ultrasensitive signal-on electrochemical aptamer sensor for assay of acetamiprid residues based on copper-centered metal-organic frameworks.Gold nanoparticles?AuNPs?and reduced graphene oxide?rGO?were synthesized.And Au-rGO was prepared.Au-rGO was used as base material to modify the GCE.Hence,the specific surface area and electrical conductivity of this electrode was increased.And this could increase the capacity of capture DNA?cDNA?.Copper-centered metal-organic frameworks?CuMOF?were synthesized and formed Au-CuMOF with AuNPs.Au-CuMOF possessed good electrochemical activity and could produce sensitive electrochemical signals.It was utilized to label the probe DNA?pDNA?.When acetamiprid appeared,acetamiprid aptamer would be turned down,and the cDNA came to exposure.The interaction between Au-CuMOF/pDNA and cDNA would push the Au-CuMOF approaching the surface of electrode,producing sensitive redox peak currents.And when the concentration of acetamiprid increased,the peak current increased.Under optimal conditions,the linearity range of acetamiprid determination was 1.0×10-121.0×10-8mol/L,and the detection limit was 2.9×10-15mol/L.This aptasensor possessed a wider linear range and higher sensitivity compared with those previously reported.The results were satisfactory when this aptasensor was applied in practical samples,such as tea.Thus,this aptasensor provided a new way for acetamiprid detection and showed enormous potential in the field of other pesticide residues detection. |
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