| With the high-speed development of social economy and the rapid improvement of living standards,the demand of Chinese people for the quality of agricultural products has risen from avoid starving to health level.Meanwhile,threatened by the excessive abuse of pesticides,the detection technology of pesticide residues in the agricultural products is an effective guarantee of the quality and safety of agricultural products.The frequently-used methods for pesticide residues detection,such as high-performance liquid and gas-phase chromatography,are confined itself to expensive equipment,long analysis cycle,high technical content and special testing requirement.Therefore,a simple,high-efficient,accurate and reliable real-time detection method for pesticide residues has more important realistic application and promotion value.Electrochemical analytical method,as a rapid-detection technology for decades,has its characteristics of high sensitivity,convenient analysis,low limit of detection(LOD)and the detection apparatus easy to miniaturize,and has blossomed into one of the most dynamic research area.The electrochemical sensors have mainly been differentiated into non-enzyme electrochemical sensors composed of nano materials and biosensors constructed by nucleic acid aptamer and antibody.In contrast,the non-enzyme chemical sensor shows stronger practical application feasibility due to its high environmental stability.As for a high-selective and high-catalytic performance of nano functional materials,the non-enzyme chemical sensor with high detection performance was constructed.The detection platform of non-enzyme electrochemical sensor was applied to the detection field of quality and safety detection of agricultural products,and the rapid and accurate detection methods of a typical herbicide isoproturon(ISO),typical fungicide carbendazim(CBZ)and toxic pesticide intermediate 2,6-dichlorophenol(2,6-DCP)were respectively realized.Meanwhile,this kind of sensor has high-sensing performance for caffeic acid(CA)in agricultural products,which shows its practicability in the detection process of active substances.(1)Under the condition of strong acid solution,Nafion is easy to become a solid superacid,and based on the fact that it has specific catalytic ability and high anti-pollution performance for agricultural residue ISO.Nafion modified glassy carbon electrode(GCE)was constructed by drop-coating method.All the analysis results demonstrate that this sensor is dependent of the Nafion modified electrode can be successfully applied to the high sensitive,selective and repeated detection of ISO.Under the most suitable conditions of electrochemical detection,the sensor exhibits its detection advantages of a wider linear range from 0.09?M to 20?M and a very low limit of detection(LOD)of 0.03?M.In the process of the detection of real samples,such as tomatoes,lettuce and other agricultural products,the recovery rate of ISO used by standard addition method is 92.60%-107.4%.All these results authenticate the good application value of the sensor.(2)Molybdenum disulfide quantum dots(Mo S2QDs)were loaded on carboxyl functionalized multi-walled carbon nanotubes(MWCNTs)by ultrasonic assisted self-assembly,and a new type of Mo S2QDs@MWCNTs nanomaterial was constructed.For the aim of the accurate detection of carbendazim(CBZ),the non-enzyme electrochemical sensor built on GCE modified with nano materials by drop-coating method was successfully applied to detect the content of CBZ in agricultural products such as lycium barbarum,platycodon grandiflorum and pear.It shows that Mo S2QDs@MWCNTs composite has a excellent electrocatalytic activity for CBZ.Under the most suitable conditions of electrochemical detection,the non-enzyme sensor has a wider detection linear area range from 0.04 to 1.00?M and a low LOD 0.026?M.In addition,the sensor has its performance of good repeatability,stability and anti-interference.This method can be used to detect CBZ in the three kinds of agricultural products as mentioned above with a recovery rate of 95.03%-102.52%,which is comparable to that of high performance liquid chromatography(HPLC)method.(3)The electrode material of GO/?-CD/CNTs compound material with synergistic effect has been prepared by ultrasonic dispersion method.The GO/?-CD/CNTs/GCE electrochemical sensor for the quantitative detection of 2,6-dichlorophenol,a potential carcinogen,was constructed and applied to the detection of 2,6-DCP of fruits and vegetables such as cucumber,tomato and citrus.The results show that GO/?-CD/CNTs nano electrode material has excellent electrochemical detection performance for 2,6-DCP,and also show that this method has practical value of the accurate detection with high sensitivity.Under the most suitable conditions of electrochemical detection,the current of oxidation peak has a good linear relationship with the concentration of 2,6-DCP range from 0.05?M to 30?M,and the LOD is as low as 10 n M.In addition,the reproducibility and stability of the sensor are fully reflected in the course of 2,6-DCP detection.Based on the synergistic effect of these three materials,a new type of GO/?-CD/CNTs/GCE non-enzyme sensor was successfully designed and constructed,which could be used for the accurate detection of 2,6-DCP in real samples.(4)The Ce-TiO2composite material was successfully prepared by rare earth doping mothod.It was used to construct Ce-Ti O2/CNTs/GCE electrochemical sensor together with CNTs which has a specific large surface area.It was proven that Ce-Ti O2/CNTs composite material has super-high surface area,good conductivity and electrocatalytic activity.The rapid,specific,sensitive and accurate detection for caffeic acid(CA)was executed by the Ce-Ti O2/CNTs/GCE electrochemical sensor.The results show that there is a good linear relationship between the concentration in the range of 10?M-1 n M and the peak current.The LOD value was calculated as low as 0.3 n M which is obviously better than that of the same type of composite sensors.In addition,it is confirmed that the Ce-Ti O2/CNTs/GCE sensor has good detection reproducibility and high-stability.The results of influence effect of dozens of inorganic/organic interference substances with different concentrations was investigated in the course of CA detection,and its specific selectivity of this type of non-enzyme sensor has been evaluated. |
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