Electrochemical-reduction Graphene And Its Application In Organophosphorus Electrochemical Sensor

China is a large country of agriculture. Pesticides in our modern agriculture is importantmeans of production for preventing and controlling the plant diseases and insect pests,ensuring the agricultural harvests and food supply. However, the widespread use of pesticideshas caused serious environmental and food safety problems, which is a bottleneck ofrestraining our country’s agricultural exports. Hence, constructing electrochemical sensorsbased on new nanocomposites and exploring rapid, sensitive, portable, low-cost andeasy-operating new methods of detection of pesticides have the practical significance. Thepurpose of this study is to develop a new rapid detection method based onelectrochemical-reduction graphene for the determination of organophosphorus residues andto reduce the testing cost in order to catering for the need of rapid detection of pesticideresidues on the agricultural production and circulation links.(1) This paper adopted the modified-hummers method to synthesize the graphene oxidewith good dispersion, used the method of electrochemical reduction to transform the grapheneoxide into grapheme and further constructed the electrochemical sensor modified withelectrochemical-reduction grapheme. Besides,this study introduced the transmission electronmicroscopy (TEM) and scanning electron microscopy (SEM) technologies to characterize thesurface morphology of graphene oxide and electrochemical-reduction graphene. The result ofTEM showed that the graphene oxide is composed of several graphene oxide monolayers andcurlled to some extent, meanwhile, the result of SEM showed that the surface of theelectrochemical reduction graphene has an evident wrinkle, which accounted for aggregationin some degree among the graphene layers in the process of electrochemical reduction.Moreover, evaluated the conductivity, adsorption ability and electroactive area of graphenemodified glassy carbon electrode (GCE) by using the cyclic voltammetry (CV), square wavevoltammetry (SWV) and AC impedance methods. The results showed that these properties arehighly superior to that of bare GCE. (2) For making the sensor detect the organophosphorus pesticides more sensitively,optimized some conditions such as the volume of graphene oxide, accumulation time and pHwhen employing the sensor in the determination of methyl parathion. The results displayedthat when the volume is8μL, accumulation time is8min and pH is7, the sensor has strongestresponse to methyl parathion. In the meantime, with employing the SWV method with bestsensitivity to study the relationship between the concentration and the response current,confirmed that the linear detection range is from100ng/mL to4000ng/mL and the limit ofdetection is8.29ng/mL. This paper also assessed some properties of the sensor whendetecting the pecticides, showing that the stability, reproducibility and anti-interference of thesensor can meet the detection requirements.(3) At the same time, for purpose of evaluating the feasibility of the sensor detecting themethyl parathion in practical samples, this paper measured the concentration of methylparathion in tap water and kiwi fruits by adopting the standard recovery test and the recoveryrate calculated can cater for the detection need for actual samples.In this paper, synthesized graphene by using the electrochemical reduction method anddeveloped graphene-based electrochemical sensor for detection of methyl-parathion (MP).The sensor has sensitive response to methyl parathion while the detection range and the limitof detection both meet the need. Furthermore, the good stability, excellent reproducibility andacceptable anti-interference abilities can ensure the detection sensitivity and accuracy. What’smore, the sensor can be well used in the determination of methyl parathion in tap water andkiwi fruits. In brief, this study built a electrochemical reduction graphene-based sensor for thedetection of methyl parathion in tap water and kiwi fruits by using the rapid and facileelectrochemical method, which not only provided new route of establishing newgraphene-based nanocomposites modified sensor, but also broadened the road fornanomaterials-based electrochemical sensor detecting the pesticides residues in food.