Composite pesticide sensing electrode and preparation method and application thereof

Abstract

The invention discloses a composite pesticide sensing electrode and a preparation method and application thereof, and belongs to the technical field of pesticide residue detection.The preparation method comprises the steps that CF is annealed and modified through activated CNC to prepare a CNC / CF composite material, and the surface of the CNC / CF composite material is modified with a Cu / CeO2 nanometer material through a hydrothermal reaction to prepare the Cu / CeO2-coated CNC / CF composite pesticide sensing electrode. The invention also discloses the Cu / CeO2 (at) CNC / CF composite pesticide sensing electrode prepared by the method and application of the composite pesticide sensing electrode in pesticide residue detection. The method has the advantages that copper atoms are embedded into CeO2 crystal lattices to construct a bifunctional active center, a single electrode is endowed with the capacity of synchronously recognizing characteristic different pesticides, synergistic interaction is achieved in cooperation with a CNC / CF porous substrate, synergistic improvement of the sensitivity and selectivity of double-pesticide detection is achieved, and the detection sensitivity and selectivity of the single electrode are improved. The prepared composite pesticide sensing electrode is strong in anti-interference performance, good in stability and high in sensitivity, and is suitable for rapidly and accurately detecting the content of various pesticide residues on agricultural products such as fruits and vegetables in the agricultural production process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of agricultural environment and safety detection technology of agricultural products, and particularly to a composite pesticide sensing electrode and a preparation method and application thereof. BACKGROUND

[0002] Pesticide residues are the core factor threatening the quality and safety of agricultural products, mainly including persistent residues of organophosphorus, organochlorine, pyrethroid and carbamate in crops, soil and water. These compounds have significant neurotoxicity, endocrine disruption and carcinogenic and teratogenic risks. Although the qualified rate of pesticide residues in agricultural products in China has increased to more than 98% (China Agricultural Product Quality and Safety Development Report (2022)), the risk of composite pesticide residues exceeding the standard in fresh food agricultural products such as vegetables, fruits and tea is still prominent.

[0003] The core challenge of current pesticide residue detection technology is the difficulty in realizing the simultaneous, rapid and reliable screening of multiple categories of pesticides, especially for on-site or online monitoring of fresh food fruits and vegetables. As the gold standard in the laboratory, the chromatography-mass spectrometry method has high sensitivity (detection limit of 0.01 mg / kg level), but the analysis time is long (more than 30 minutes for a single run), and it is usually difficult to cover multiple pesticide categories with large differences in chemical properties in one run (such as simultaneous detection of organophosphorus, pyrethroid and specific fungicides). The biosensor is easily interfered by tea polyphenols, vegetable and fruit pigments and other matrixes, with a false positive rate as high as 35% in mixed pesticide detection. The immunoassay can realize on-site rapid detection in 10-15 minutes, but it is limited by the core of high specificity of antibodies (usually one antibody can only effectively recognize one or a few compounds with highly similar structure), and the detection is limited. This limitation is particularly prominent when facing different categories of pesticides with different chemical properties. For example, when carbendazim (small molecular weight, strong polarity, relatively good water solubility, benzimidazole fungicide) and chlorantraniliprole (large molecular weight, highly hydrophobic, halogen-rich diamide insecticide) are detected simultaneously, there are fundamental differences in the core molecular skeleton, spatial configuration, surface charge distribution and key recognition sites (such as the benzimidazole ring of carbendazim and the specific halogenated benzamide structure of chlorantraniliprole). In order to realize reliable detection of the two pesticides, a large amount of resources must be invested, and two independent detection systems must be developed, resulting in doubled cost and reduced efficiency. This technical limitation seriously restricts the real-time monitoring capability of composite pesticide residues in fresh food agricultural products, and becomes a key bottleneck restricting the improvement of quality and safety supervision efficiency.

[0004] Currently, there are still significant limitations in the improvement attempts for multi-residue synchronous detection. For example, a rapid detection technology based on hydrogel enhanced Raman spectrum (Ag@PAM)

Ma, Hui, et al. Isotropic shrinkage-inspired strategy for plasmonic nanoparticle-loaded hydrogel SERS sensor towards robust and sensitive detection of pesticides.

Qiao Hai-xia, Cao Ning, Cai Ke-wen, Liu Jian-yang. Determination of 12 pesticide residues in rice by QuEChERS-triple quadrupole gas chromatography-mass spectrometry method [J]

Akhtar, Aqsa, et al. Safety Assessment and Contaminants Detection in Different types of Tea and Tea products.

[0005] This serious shortage of detection ability for “complex pesticide residues” and multi-target pesticide synchronous detection has become a key bottleneck restricting the real-time monitoring and regulatory effectiveness of fresh food quality and safety. Therefore, there is an urgent need and great application value to develop a new type of sensing platform that can overcome the specificity limitation, effectively resist matrix interference, and achieve synchronous rapid detection of multiple types of pesticides, especially a complex pesticide sensing electrode suitable for fruit and vegetable scenes. SUMMARY

[0006] The purpose of the present application is to provide a complex pesticide sensing electrode and its preparation method and application, solve the problem that the existing method for detecting pesticide residues requires high equipment and detection technology, and is difficult to detect multiple pesticide residues on fruits and vegetables in a timely and rapid manner.

[0007] The purpose of the present application is achieved by the following technical solutions: The application discloses a preparation method of a composite pesticide sensing electrode, and the preparation method comprises the following steps: activating CNC, annealing the activated CNC to modify CF to obtain a CNC / CF composite material, and modifying Cu / CeO2 nano material on the surface of the CNC / CF composite material through a hydrothermal reaction to obtain a Cu / CeO2@CNC / CF composite pesticide sensing electrode. The CNC is carbon nanocoil. The CF is carbon foam.

[0008] Further, the activation of the CNC comprises the following steps: X1, the CNC and concentrated nitric acid are sequentially added into a container, and the concentrated nitric acid is used to immerse the CNC to obtain a CNC dispersion liquid; X2, the container is sealed and placed in the dark, and after the CNC is activated, the activated CNC is separated out; X3, the separated-out CNC is sequentially cleaned by using deionized water and anhydrous ethanol, and then dried for use.

[0009] Further, the annealing modification of the activated CNC to CF comprises the following steps: Y1, the activated CNC is added into a container containing anhydrous ethanol to obtain a dispersion liquid; Y2, CF is added into the container and immersed in the dispersion liquid, and ultrasonic treatment is performed to make the CNC adhere to the surface of the CF, and then the CF is separated out; Y3, the separated-out CF is dried, and then carbonized by high-temperature annealing treatment under the protection of inert gas, and then cooled to obtain a CNC / CF composite material.

[0010] Further, the carbon foam is melamine foam.

[0011] Further, the modification of the CNC / CF composite material with Cu / CeO2 nano material comprises the following steps: Z1, a precursor solution containing Cu and Ce is prepared; Z2, the CNC / CF composite material is immersed in the precursor solution, and ultrasonic treatment is performed to make the precursor solution fully mix and contact with the CNC / CF; Z3, the mixed system obtained in the step Z2 is transferred into a hydrothermal reaction kettle, and Cu / CeO2 nano material is grown on the surface of the CNC / CF composite material through a hydrothermal reaction; Z4, the solid material is separated out, cleaned by using deionized water, and then dried to obtain a Cu / CeO2@CNC / CF composite pesticide sensing electrode.

[0012] Further, the step of Z1 specifically comprises: placing copper nitrate, cerium nitrate and sodium hydroxide in a container, adding deionized water, and stirring until the solute is completely dissolved, to obtain a precursor solution containing copper and cerium, and the molar ratio of Ce to Cu in the precursor solution is 5:1.

[0013] The application further provides a composite pesticide sensing electrode, which is a Cu / CeO2@CNC / CF composite pesticide sensing electrode prepared by the preparation method of the composite pesticide sensing electrode.

[0014] The application further provides an application of the composite pesticide sensing electrode, in particular, an application of the Cu / CeO2@CNC / CF composite pesticide sensing electrode in detection of pesticide residues in an aqueous solution.

[0015] Further, the pesticides include chlorantraniliprole and carbendazim.

[0016] Further, the step of detecting the pesticide residues in the aqueous solution by the Cu / CeO2@CNC / CF composite pesticide sensing electrode comprises the following steps: a. using the Cu / CeO2@CNC / CF composite pesticide sensing electrode as a working electrode, a silver chloride electrode as a reference electrode, and a platinum sheet electrode as an auxiliary electrode to form a three-electrode system in an electrolyte containing a PBS buffer and different concentration pesticide content standard solutions, and using a differential pulse voltammetry (DPV) test method of the three-electrode system to test, and recording current values generated by different concentrations of pesticides on the electrode surface with voltage changes in the current-voltage scanning process; b. according to the concentration of the pesticide standard solution and the corresponding current response peak value, a standard curve is prepared, and a linear equation is constructed; c. the different concentration pesticide content standard solutions in step a are replaced by the to-be-tested aqueous solution, and the method in step a is used for detection to obtain a corresponding current response value, which is substituted into the linear equation constructed in step b to calculate the content of the pesticide residues in the to-be-tested aqueous solution.

[0017] Further, in step b, the constructed linear equation is: p =a+bX Pesticide , wherein X Pesticide is the concentration of the pesticide content, I p is the current response peak value, a is the intercept of the linear regression equation, and is used to represent the background current signal under the condition of zero concentration; b is the slope of the linear regression equation, and is used to represent the sensitivity of the current response to the change of the pesticide concentration.

[0018] The application has the following advantages: 1. The CNC / CF composite material is prepared by modifying CF through activated CNC annealing, Cu / CeO2 nanomaterials are modified on the surface of the CNC / CF composite material through hydrothermal reaction, the dual functional active center is constructed by embedding copper atoms into the CeO2 lattice, the ability of a single electrode to simultaneously identify pesticides with different characteristics is endowed, the synergistic effect of the porous substrate of CNC / CF is utilized, the synergistic improvement of the sensitivity and selectivity of double pesticides is realized, and an effective technical method and way is provided for the pesticide residue detection electrode.

[0019] 2. The prepared composite pesticide sensing electrode has strong anti-interference, good stability and high sensitivity, can timely and quickly detect the residues of two pesticides with different characteristics, and is suitable for rapid and accurate detection of the content of various pesticide residues on agricultural products such as fruits and vegetables in the agricultural production process. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Figure 1 is a SEM image of the unmodified CNC / CF and Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0021] Figure 2 Figure 3 is an EDS spectrum of the Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0022] Figure 3 Figure 4 is an XRD graph of the Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0023] Figure 4 Figure 5 is an XPS graph of the Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0024] Figure 5 Figure 6 is a performance detection graph of the Cu / CeO2@CNC / CF composite pesticide sensing electrode.

[0025] Figure 6 Figure 7 is a standard curve of the pesticide concentration and current response peak value of the Cu / CeO2@CNC / CF composite pesticide sensing electrode.

[0026] Figure 7 Figure 8 is a stability and anti-interference verification graph of the Cu / CeO2@CNC / CF composite pesticide sensing electrode for rapid detection of pesticide residue content in a solution. DETAILED DESCRIPTION

[0027] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. The components of the embodiments of the present application generally described and shown in the drawings can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0030] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0031] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly placed when the product of the present application is used, or the orientation or positional relationship commonly understood by those skilled in the art, and are only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used to distinguish description, and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. Example 1

[0033] The embodiment provides a preparation method of a composite pesticide sensing electrode. The preparation method comprises the following steps: activating CNC (carbon nanocoil with a space spiral structure), modifying CF (carbon foam) by using the activated carbon nanocoil to obtain a CNC / CF composite material, and modifying Cu / CeO2 nanomaterial on the surface of the CNC / CF composite material through a hydrothermal reaction to obtain a Cu / CeO2@CNC / CF composite pesticide sensing electrode.

[0034] The activation of the CNC comprises the following steps: X1, 40 mg of CNC is placed in a transparent glass reagent bottle, 30 ml of concentrated nitric acid is added, and the concentrated nitric acid is immersed in the CNC to obtain a CNC dispersion liquid; X2, the transparent glass reagent bottle is sealed and placed in the dark for 3 days, and after the CNC is activated, a vacuum filtration device is used to separate the CNC and the concentrated nitric acid solution; X3, the separated CNC is washed with deionized water and anhydrous ethanol for 5-10 times in sequence, and then the washed CNC is placed in an oven at 60°C for drying.

[0035] The annealing modification of the activated CNC to CF comprises the following steps: Y1, 40 mg of the activated CNC is added to a beaker containing 15 ml of anhydrous ethanol to obtain a dispersion liquid; Y2, melamine foam is added to the beaker and immersed in the dispersion liquid, and ultrasonic treatment is performed for 30 min, so that the CNC is attached to the surface of the melamine foam, and the melamine foam is separated (fished out) after the ultrasonic treatment is completed; Y3, the separated melamine foam is placed in an oven at 60°C for drying for 3 h, and the completely dried melamine foam is placed in a tube furnace and carbonized at 700°C for 3 h under the protection of an inert atmosphere (Ar) to obtain carbon nanocoil modified carbon foam (CNC / CF composite material).

[0036] As shown in the SEM images of the unmodified CNC / CF shown in Figure 1 (a), Figure 1 (b), it can be seen that the CNC (spiral) is uniformly dispersed and connected to the surface and pores of the CF (porous skeleton) to form a three-dimensional interpenetrating structure. This close contact and connection effectively bridges the CF skeleton and constructs a continuous and low-resistance conductive network path, which can significantly improve the electronic transmission capacity of the composite material.

[0037] CNC is a helical carbon nanotube with good electrical conductivity, excellent mechanical properties and physical and chemical stability. It can capture pesticide molecules by virtue of its high-curvature surface, and its nanowinding structure forms an electron superfast transmission chain. The three-dimensional through-hole framework of CF breaks through the mass transfer limit, realizes the rapid bulk-phase diffusion and interface enrichment of pesticide molecules, and the combination of the two forms a synergistic effect of the porous substrate, forming a cascade enhancement network of "molecular capture-electron transmission-ion diffusion". This structure coupling makes the electrode break through the trade-off limit of traditional materials "conductivity-adsorbability". With the assistance of copper-doped band structure regulation, the sensitivity and selectivity of double pesticide detection are finally realized.

[0038] The surface modification of the CNC / CF composite material with Cu / CeO2 nanomaterial includes the following steps: Z1, preparing a Cu and Ce-containing precursor solution, placing copper nitrate (Cu(NO3)2·3H2O), cerium nitrate (Ce(NO3)3·6H2O) and sodium hydroxide in a beaker, adding 10 ml of deionized water, stirring for 2 min until the solute is completely dissolved, thereby obtaining a Cu and Ce-containing precursor solution, and the molar ratio of Ce to Cu in the precursor solution is 5:1; Z2, immersing the CNC / CF composite material in the precursor solution, placing the beaker containing the precursor solution and the CNC / CF in an ultrasonic machine for ultrasonic treatment for 10 min, so that the precursor solution and the CNC / CF are fully mixed and contacted; Z3, transferring the mixed system obtained in step Z2 to a hydrothermal reaction kettle, placing the reaction kettle in an electric heating air drying oven for hydrothermal reaction at 150-180°C for 6-12 h, and growing Cu / CeO2 nanomaterial on the surface of the CNC / CF composite material; Z4, separating the solid material by a vacuum filter, washing it 5-10 times with deionized water, and then drying it in a 60°C oven for 6 h to obtain a Cu / CeO2@CNC / CF composite pesticide sensing electrode.

[0039] As shown in Figure 1 (c), Figure 1 (d), the SEM image of the Cu / CeO2@CNC / CF composite pesticide sensing electrode material, it can be seen that the three-dimensional porous framework structure of CNC / CF is completely retained, proving that the hydrothermal process does not damage the stability of the substrate. Cu / CeO2 nanomaterial uniformly coats the surface of CNC / CF with high density, forming a continuous covering layer. The nanoparticles adhere tightly to the carbon skeleton, ensuring electron transmission across the interface; the CF pores are not blocked, maintaining a high specific surface area of active sites, and the composite structure provides a synergistically optimized conductive network and reaction interface for pesticide molecule diffusion and electrochemical response.

[0040] The application constructs a bifunctional active center by embedding copper atoms into the CeO2 lattice: oxygen vacancy-cerium site synergistically catalyzes the oxidation reaction of carbendazim benzimidazole ring, and a significantly enhanced oxidation peak current (concentration positive correlation) is generated in the 0.8-1.1 V interval; and the copper-doped site specifically binds to the nitro group of chlorantraniliprole, resulting in selective inhibition of the characteristic reduction peak current in the -0.2-0 V interval (concentration negative correlation). The two mechanisms are naturally decoupled in the potential window and response mode (one rise and one fall), giving the single electrode the ability to simultaneously identify pesticides with different characteristics. Through the synergistic effect of copper-doped defects and CNC / CF hierarchical structure, the detection sensitivity and selectivity of two pesticides with different chemical properties are synergistically improved. Example 2

[0041] This example provides a Cu / CeO2@CNC / CF composite pesticide sensing electrode prepared by the method described in Example 1.

[0042] As shown in Figure 2 , it can be seen from Figure 2 (a) that the Cu / CeO2@CNC / CF composite pesticide sensing electrode material is formed by hydrothermal growth of Cu / CeO2 composite material on the surface of CNC / CF, which can prove the effective synthesis of the composite pesticide sensing electrode material. As shown in Figure 2 (b), the Cu / CeO2 nanolayer forms a continuous covering on the surface of the CNC / CF skeleton, completely shielding the X-ray signal of the underlying carbon skeleton and blocking the exposure path of the C element, thereby causing a C element vacancy phenomenon, confirming that the hydrothermal synthesis realizes the coating of Cu / CeO2 material on the CNC / CF skeleton. As shown in Figure 2 (c), (d), and Figure 2 (e), it can be seen that O element, Ce element and Cu element are successfully synthesized on the surface of CNC / CF. Figure 2 Figure 2 (f) shows the element peak intensity, and the cerium content is about 10 times that of copper, verifying the successful doping of copper, and also verifying the successful synthesis of the Cu / CeO2@CNC / CF composite pesticide sensing electrode material again.

[0043] The XRD pattern of the Cu / CeO2@CNC / CF composite pesticide sensing electrode is shown in Figure 3 , and it can be seen from Figure 3 that: compared with the XRD peak value of unmodified CNC / CF, the XRD peak value of the Cu / CeO2@CNC / CF composite pesticide sensing electrode material is basically consistent with the CuO standard card (PDF # 45-0937) and the CeO2 standard card (PDF # 43-1002), further proving the successful doping of copper element and the effective synthesis of the Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0044] ​XPS spectrum of Cu / CeO2@CNC / CF composite pesticide sensing electrode material Figure 4 As shown. Figure 4 As shown in (a), the C–C and C=O characteristic peaks appearing in the C1s spectrum indicate that the carbon-based skeleton structure in the composite material is intact, providing a stable channel for electron transport and supporting the dispersion of active centers; Figure 4 As shown in (b), the Cu–O and O–H peaks appear in the O1s spectrum, indicating the presence of copper oxides and hydroxyl groups on the surface of the composite material. This feature proves that copper has been combined with the oxygen environment, forming a potential doping site that helps to interact with specific functional groups of the pesticide molecules; Figure 4 As shown in (c), the Ce3d spectrum also contains Ce 4+ With Ce 3+ The characteristic peaks indicate that there are many oxygen vacancies in the CeO2 lattice. That is, the present invention embeds copper atoms into the CeO2 lattice to induce the generation of oxygen vacancies, thereby constructing an "oxygen vacancy-cerium site" bifunctional active center, which can synergistically catalyze the oxidation reaction of the benzimidazole ring of carbendazim; Figure 4 As shown in (d), Cu2p appears at 933eV and 953eV in the Cu2p spectrum. 3 / 2 With Cu2p 1 / 2 characteristic peaks, accompanied by obvious satellite peaks, indicating that copper is mainly in the form of Cu 2+ The CuO component exists in the morphology and is formed. Combined with the O1s analysis results, it can be confirmed that copper is successfully doped into the CeO2 lattice and becomes a specific action site, which can specifically bind to the nitro group of the chlorantraniliprole molecule.

[0045] pass Figure 4 XPS analysis not only confirmed the presence of the carbon-based structure, CeO2 oxygen vacancies, and Cu doping in the composite material, but also demonstrated that the copper-doped bifunctional active centers exhibit a naturally decoupled response pattern (one rise, one fall) within the redox potential window. Combined with the hierarchical conductive structure of CNC / CF, this enables simultaneous recognition of chemically diverse pesticides, significantly improving detection sensitivity and selectivity. Example 3

[0046] This embodiment provides an application of the Cu / CeO2@CNC / CF composite pesticide sensing electrode of Example 2, specifically an application of the Cu / CeO2@CNC / CF composite pesticide sensing electrode in the detection of pesticide residues in aqueous solution.

[0047] Among them, the pesticides are chlorfenapyr and carbendazim.

[0048] The steps for using the Cu / CeO2@CNC / CF composite pesticide sensing electrode to detect pesticide residues in aqueous solution are as follows: a. To 100 mL of electrolyte (PBS phosphate buffer solution prepared: 0.1 mol / L sodium chloride, 0.01 mol / L Na2HPO4, 0.01 mol / L KH2PO4, adjust the pH of the electrolyte to 6), add 1 μl, 3 μl, 5 μl, 10 μl, 20 μl, 35 μl, 70 μl, 90 μl, 120 μl, 150 μl, 200 μl, and 3000 μl of different volumes of pesticide standard solution, so that the concentration range of the pesticide in the detection system is 0~300 μM. The Cu / CeO2@CNC / CF composite pesticide sensing electrode is fixed firmly with a polytetrafluoroethylene platinum electrode clamp to obtain an electrochemical sensing working electrode, a silver chloride electrode as a reference electrode, and a platinum electrode as an auxiliary electrode to form a three-electrode system. The three-electrode system is tested by DPV test method. The Cu / CeO2@CNC / CF composite pesticide sensing electrode is placed in the above electrolyte containing PBS buffer and different concentrations of pesticide standard solution for current-voltage scanning. The voltage window is -1~1.5 V. The current value generated on the electrode surface corresponding to different pesticide concentrations is recorded during the scanning process.

[0049] As shown in Figure 5 , Figure 5 (a) is the DPV curve for simultaneous detection of pesticides chlorantraniliprole and carbendazim, Figure 5 (b) is the DPV curve for gradient detection of chlorantraniliprole alone, Figure 5 (c) is the DPV curve for gradient detection of carbendazim alone. From Figure 5 (a), it can be seen that the Cu / CeO2@CNC / CF composite pesticide sensing electrode can simultaneously detect pesticides chlorantraniliprole and carbendazim, and the linear range for simultaneous detection is 100 nM~40 μM, and there is no mutual interference. Figure 5 (b), Figure 5 (c) shows that the Cu / CeO2@CNC / CF composite pesticide sensing electrode can detect pesticides chlorantraniliprole and carbendazim alone, and the response value of the single detection changes with the increase of the concentration of the pesticide. Chlorantraniliprole is combined with copper active sites due to the nitro group (forming an electron transfer barrier), which hinders its reduction reaction, which is manifested as a monotonic decrease in the reduction peak current value in the potential interval of -0.2~0 V with the increase of its concentration; while carbendazim is catalytically oxidized (oxygen vacancy-Ce 3+ / Ce 4+ mediation) in the 0.8~1.1 V interval, which is manifested as a linear increase in the oxidation peak current value in the 0.8~1.1 V potential interval with the increase of its concentration. The linear range of chlorantraniliprole detection is 100 nM~50 μM, and the linear range of carbendazim detection is 100 nM~300 μM.

[0050] In the detection process, the current response value can be detected in only 5 min, and the detection limit is low and the sensitivity is high, so that on-site rapid detection of two kinds of pesticides with different characteristics can be realized.

[0051] b. With the concentration of pesticide standard solution as the abscissa and the corresponding current response peak value as the ordinate, a standard curve is prepared by linear equation fitting using Origin software, a linear equation is constructed, and the constructed linear equation is: p =a+bX Pesticide , wherein X Pesticide is the concentration of pesticide content, I p is the current response peak value, a is the intercept of the linear regression equation, which is used to represent the background current signal under zero concentration conditions; b is the slope of the linear regression equation, which is used to represent the sensitivity of the current response to the change in pesticide concentration.

[0052] As shown in Figure 6 , Figure 6 (a) is the linear relationship between the concentration and the current peak value of chlorantraniliprole detected alone by gradient, Figure 6 (b) is the linear relationship between the concentration and the current peak value of carbendazim detected alone by gradient. The current response change value regression equation for detecting chlorantraniliprole is I = 4.54-0.041X Chlorfenobenzene , the correlation coefficient is 0.998, and X Chlorfenobenzene is the concentration of chlorantraniliprole; the current response change value regression equation for detecting carbendazim is I = 2.145+0.00128X Carbendazim , the correlation coefficient is 0.992, and X Carbendazim is the concentration of carbendazim. According to the above regression equation, it can be shown that the Cu / CeO2@CNC / CF composite pesticide sensing electrode has good detection performance for pesticides chlorantraniliprole and carbendazim.

[0053] c. For pesticide residue detection in a sample, replace the different concentrations of pesticide content standard solution in step a with the water solution to be tested, and detect according to the method of step a to obtain the corresponding current response value, and substitute it into the linear equation constructed in step b to calculate the content of pesticide residues in the water solution to be tested.

[0054] Stability test of Cu / CeO2@CNC / CF composite pesticide sensing electrode: 40 μl of pesticide chlorantraniliprole and carbendazim standard solution was added to 100 mL of electrolyte, and DPV detection was repeated for 10 times. Referring to Figure 7 (a), it can be seen that the composite pesticide sensing electrode prepared by this method has good stability.

[0055] Anti-interference test of Cu / CeO2@CNC / CF composite pesticide sensing electrode: The Cu / CeO2@CNC / CF composite pesticide sensing electrode is placed in 100 mL of electrolyte, 50 μl of pesticide chlorantraniliprole and carbendazim standard solution is added in advance in the electrolyte. Interfering substances such as grass ammonium, glyphosate, dichlorvos, deltamethrin, thiophanate-methyl, glucose, Cd(II), Pb(II) are added in the electrolyte in turn, and two DPV tests are carried out for each interfering substance, so as to obtain the detection curve in the interference state. See Figure 7 (b), the ordinate is the ratio of the current value after adding the interfering substance to the current value without adding the interfering substance, and it can be seen from the figure that the composite pesticide sensing electrode has good anti-interference ability.

[0056] In the stability and anti-interference test, the electrolyte is 100 mL of PBS phosphate buffer solution containing 0.1 mol / L sodium chloride, 0.01 mol / L Na2HPO4, 0.01 mol / L KH2PO4 and pH 6; the pesticide concentration is 40 μM.

[0057] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a composite pesticide sensing electrode, characterized in that: The preparation method activates CNC, anneals the activated CNC to modify CF to obtain a CNC / CF composite material, and then modifies the surface of the CNC / CF composite material with Cu / CeO2 nanomaterials through a hydrothermal reaction to obtain a Cu / CeO2@CNC / CF composite pesticide sensing electrode. The CNC is a carbon nanocoil; The CF is carbon foam.

2. The method for preparing the composite pesticide sensing electrode according to claim 1, wherein: The CNC activation comprises the following steps: X1. Add CNC and concentrated nitric acid into a container in sequence, and immerse the CNC in the concentrated nitric acid to prepare a CNC dispersion; X2. Seal the container and keep it away from light. After the CNC is activated, separate the activated CNC. X3. Use deionized water and anhydrous ethanol to clean the separated CNC, and then dry it for use.

3. The method for preparing the composite pesticide sensing electrode according to claim 1, wherein: The activated CNC annealing modified CF comprises the following steps: Y1. Add the activated CNC into a container containing anhydrous ethanol to prepare a dispersion; Y2, CF was added to the container and immersed in the dispersion, and ultrasonic treatment was performed to make CNC adhere to the surface of CF and separate CF; Y3. The separated CF is dried, and then annealed at high temperature under the protection of inert gas to carbonize the CF, and then cooled to obtain a CNC / CF composite material.

4. The method for preparing the composite pesticide sensing electrode according to claim 3, wherein: The carbon foam is melamine foam.

5. The method for preparing the composite pesticide sensing electrode according to claim 1, wherein: The surface modification of the CNC / CF composite material with Cu / CeO2 nanomaterials comprises the following steps: Z1. Prepare a precursor solution containing Cu and Ce; Z2, immersing the CNC / CF composite material in the precursor solution and ultrasonically treating the precursor solution to fully mix and contact the CNC / CF; Z3, transferring the mixed system obtained in step Z2 to a hydrothermal reactor, and growing Cu / CeO2 nanomaterials on the surface of the CNC / CF composite material through a hydrothermal reaction; Z4. Separate the solid material, wash it with deionized water, and then dry it to obtain the Cu / CeO2@CNC / CF composite pesticide sensing electrode.

6. The method for preparing the composite pesticide sensing electrode according to claim 5, characterized in that: The Z1 step specifically includes: placing copper nitrate, cerium nitrate, and sodium hydroxide in a container, adding deionized water, and stirring until the solute is completely dissolved to obtain a precursor solution containing copper and cerium, wherein the molar ratio of Ce to Cu in the precursor solution is 5:

1.

7. Composite pesticide sensing electrode, characterized by: The Cu / CeO2@CNC / CF composite pesticide sensing electrode is prepared by the preparation method of the composite pesticide sensing electrode according to any one of claims 1 to 6.

8. Application of composite pesticide sensing electrode, characterized by: Use of the Cu / CeO2@CNC / CF composite pesticide sensing electrode as claimed in claim 7 in the detection of pesticide residues in aqueous solution.

9. The use of the composite pesticide sensing electrode according to claim 8, characterized in that: The pesticides include chlorantraniliprole and carbendazim.

10. The use of the composite pesticide sensing electrode according to claim 8, characterized in that: The steps of detecting pesticide residues in aqueous solution using the Cu / CeO2@CNC / CF composite pesticide sensing electrode are as follows: a. A three-electrode system consisting of the Cu / CeO2@CNC / CF composite pesticide sensing electrode as the working electrode, a silver chloride electrode as the reference electrode, and a platinum sheet electrode as the auxiliary electrode was placed in an electrolyte containing PBS buffer and standard solutions of pesticide content at different concentrations. The three-electrode system was tested using the DPV test method, and the current values ​​generated by the voltage changes at the electrode surface corresponding to different pesticide concentrations were recorded during the current-voltage scan process; b. Create a standard curve and construct a linear equation based on the concentration of the pesticide standard solution and the corresponding current response peak; c. Replace the pesticide content standard solutions of different concentrations in step a with the aqueous solution to be tested, perform detection according to the method in step a, obtain the corresponding current response value, and substitute it into the linear equation constructed in step b to calculate the content of pesticide residues in the aqueous solution to be tested.

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