Composite pesticide sensing electrode and preparation method and application thereof

Abstract

This invention discloses a composite pesticide sensing electrode, its preparation method, and its application, belonging to the field of pesticide residue detection technology. The preparation method involves annealing activated CNC to modify CF to obtain a CNC / CF composite material. A Cu / CeO2 nanomaterial is then modified onto the surface of the CNC / CF composite material via a hydrothermal reaction to obtain a Cu / CeO2@CNC / CF composite pesticide sensing electrode. This invention also discloses the Cu / CeO2@CNC / CF composite pesticide sensing electrode prepared by the above method and its application in pesticide residue detection. The beneficial effects of this invention are: by utilizing copper atoms embedded in the CeO2 lattice to construct bifunctional active centers, a single electrode is endowed with the ability to simultaneously identify pesticides with vastly different characteristics. Combined with the synergistic effect of the porous CNC / CF substrate, the sensitivity and selectivity of dual pesticide detection are synergistically improved. The resulting composite pesticide sensing electrode exhibits strong anti-interference properties, good stability, and high sensitivity, making it suitable for rapid and accurate detection of multiple pesticide residues in agricultural production processes and on fruits, vegetables, and other agricultural products.

Description

Technical Field

[0001] This invention relates to the field of agricultural environment and agricultural product safety testing technology, particularly to composite pesticide sensing electrodes, their preparation methods, and applications. Background Technology

[0002] Pesticide residues are a core factor threatening the quality and safety of agricultural products. These mainly include persistent residues of organophosphates, organochlorines, pyrethroids, and carbamates in crops, soil, and water. These compounds have significant neurotoxicity, endocrine disruption, and carcinogenic and teratogenic risks. Although the pass rate for pesticide residues in agricultural products in my country has increased to over 98% (China Agricultural Product Quality and Safety Development Report (2022)), the risk of excessive compound pesticide residues in fresh agricultural products such as vegetables, fruits, and tea remains prominent.

[0003] The core challenge facing current pesticide residue detection technologies lies in the difficulty of achieving simultaneous, rapid, and reliable screening of multiple pesticide categories, especially in on-site or online monitoring scenarios for fresh fruits and vegetables. Chromatography-mass spectrometry (GC-MS), as the gold standard in laboratories, offers high sensitivity (detection limits down to 0.01 mg / kg), but its analysis time is long (over 30 minutes per run) and it is typically difficult to cover multiple pesticide categories with vastly different chemical properties in a single run (e.g., simultaneously detecting organophosphates, pyrethroids, and specific fungicides). Biosensors are susceptible to interference from matrices such as tea polyphenols and fruit and vegetable pigments, resulting in false positive rates as high as 35% in mixed pesticide detection. While immunoassays can achieve rapid on-site detection in 10-15 minutes, their detection is limited by the core limitation of highly specific antibodies (typically, one antibody can only effectively recognize one or a few structurally similar compounds). This limitation is particularly pronounced when dealing with different categories of pesticides with vastly different chemical properties. For example, when simultaneously detecting carbendazim (a low-molecular-weight, highly polar, and relatively water-soluble benzimidazole fungicide) and chlorantraniliprole (a high-molecular-weight, highly hydrophobic, and halogen-rich diamide insecticide), fundamental differences exist between the two in their core molecular skeletons, spatial configurations, surface charge distributions, and key recognition sites (such as the benzimidazole ring of carbendazim and the specific halogenated benzamide structure of chlorantraniliprole). To achieve reliable detection of these two pesticides, substantial resources must be invested, requiring the development of two separate detection systems, leading to a significant increase in costs and reduced efficiency. This technological limitation severely restricts the real-time monitoring capability of compound pesticide residues in fresh agricultural products, becoming a key bottleneck hindering the improvement of quality and safety supervision efficiency.

[0004] Currently, attempts to improve the simultaneous detection of multiple residues still have significant limitations. For example, a rapid detection technique based on hydrogel-enhanced Raman spectroscopy (Ag@PAM) [Ma, Hui, et al. Isotropic shrinkage-inspired strategy for plasmonic nanoparticle-loaded hydrogel SERS sensor toward robust and sensitive detection of pesticides.] can complete the highly sensitive detection of pesticide residues on apple surfaces within 12 minutes, but it still relies on algorithms to separate spectral peaks and does not yet have universal recognition capabilities for pesticide combinations with large structural differences. When determining 10 organochlorine pesticides in rice using the QuEChERS-triple quadrupole gas chromatography-mass spectrometry method [Qiao Haixia, Cao Ning, Cai Kewen, Liu Jianyang. Determination of 12 pesticide residues in rice using the QuEChERS-triple quadrupole gas chromatography-mass spectrometry method [J]], the purification process needs to be optimized to address matrix effects, resulting in significant fluctuations in recovery rates. Furthermore, tea is rich in polyphenols, pigments, caffeine, and other compounds, which can interfere with the accuracy of pesticide detection tools (such as immunosensors, biosensors, and enzyme sensors) [Akhtar, Aqsa, et al. Safety Assessment and Contaminants Detection in Different types of Tea and Tea products.].

[0005] This severe deficiency in the ability to detect "compound pesticide residues" and the simultaneous detection of multiple pesticide targets has become a key bottleneck restricting the improvement of real-time monitoring and regulatory efficiency for the quality and safety of fresh agricultural products. Therefore, the development of new sensing platforms that can overcome specificity limitations, effectively resist matrix interference, and achieve simultaneous and rapid detection of multiple types of pesticides, especially compound pesticide residue sensing electrodes suitable for fruit and vegetable scenarios, is urgently needed and has significant application value. Summary of the Invention

[0006] The purpose of this invention is to provide a composite pesticide sensing electrode, its preparation method, and its application, thereby solving the problem that existing methods for detecting pesticide residues require advanced equipment and detection technologies, making it difficult to detect multiple pesticide residues on fruits, vegetables, and other agricultural products in a timely and rapid manner.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a composite pesticide sensing electrode, wherein the preparation method involves activating CNC, annealing and modifying CF with activated CNC to obtain a CNC / CF composite material, and then modifying 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.

[0009] The CNC is a carbon nanotube coil;

[0010] The CF is carbon foam.

[0011] Furthermore, the activation of the CNC includes the following steps:

[0012] X1. Add CNC and concentrated nitric acid to the container in sequence, and immerse CNC in concentrated nitric acid to obtain CNC dispersion;

[0013] X2. Place in a sealed container away from light. After the CNC is activated, separate the activated CNC.

[0014] X3. Clean the separated CNC with deionized water and anhydrous ethanol in sequence, and then dry it for later use.

[0015] Furthermore, the activated CNC annealed modified CF includes the following steps:

[0016] Y1. Add the activated CNC to a container filled with anhydrous ethanol to obtain a dispersion.

[0017] Y2. Add melamine foam to a container and immerse it in the dispersion. Use ultrasound to make CNC adhere to the surface of the melamine foam and separate the melamine foam.

[0018] Y3. The separated melamine foam is dried, and then subjected to high-temperature annealing under the protection of inert gas to carbonize the melamine foam. After cooling, CNC / CF composite material is obtained.

[0019] Furthermore, the surface modification of CNC / CF composite materials with Cu / CeO2 nanomaterials includes the following steps:

[0020] Z1. Prepare a precursor solution containing Cu and Ce;

[0021] Z2. Immerse the CNC / CF composite material in the precursor solution and ultrasonically treat it to ensure that the precursor solution and CNC / CF are fully mixed and in contact.

[0022] Z3. Transfer the mixed system obtained in step Z2 to a hydrothermal reactor, and grow Cu / CeO2 nanomaterials on the surface of the CNC / CF composite material through hydrothermal reaction.

[0023] Z4. The solid material was separated, washed with deionized water, and then dried to obtain the Cu / CeO2@CNC / CF composite pesticide sensing electrode.

[0024] Further, step Z1 specifically includes: placing copper nitrate, cerium nitrate, and sodium hydroxide in a container, adding deionized water, and stirring until the solutes are 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.

[0025] The present invention also provides a composite pesticide sensing electrode, wherein the composite pesticide sensing electrode is prepared by the above-mentioned method for preparing the composite pesticide sensing electrode, and the Cu / CeO2@CNC / CF composite pesticide sensing electrode is obtained.

[0026] The present invention also provides the application of composite pesticide sensing electrodes, specifically the application of Cu / CeO2@CNC / CF composite pesticide sensing electrodes in the detection of pesticide residues in aqueous solutions.

[0027] Furthermore, pesticides include: chlorantraniliprole and carbendazim.

[0028] Furthermore, the steps for detecting pesticide residues in aqueous solution using the Cu / CeO2@CNC / CF composite pesticide sensing electrode are as follows:

[0029] 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 pesticides at different concentrations. The differential pulse voltammetry (DPV) method of the three-electrode system was used for testing. During the current-voltage scan, the current values ​​generated on the electrode surface corresponding to different pesticide concentrations as the voltage changed were recorded.

[0030] b. Based on the concentration of the pesticide standard solution and the corresponding current response peak, a standard curve is prepared and a linear equation is constructed;

[0031] c. Replace the standard solutions of different pesticide concentrations in step a with the aqueous solution to be tested, and perform the detection according to the method in step a to obtain the corresponding current response value. Substitute the current response value into the linear equation constructed in step b to calculate the pesticide residue content in the aqueous solution to be tested.

[0032] Furthermore, in step b, the constructed linear equation is: Ⅰ p =a+bX Pesticide , where X Pesticide The concentration of pesticide content, I p denoted as the peak value of the current response, a is the intercept of the linear regression equation, used to characterize the background current signal under zero concentration conditions; b is the slope of the linear regression equation, used to characterize the sensitivity of the current response to changes in pesticide concentration.

[0033] The present invention has the following advantages:

[0034] 1. A CNC / CF composite material was prepared by annealing activated CNC and modifying CF. Cu / CeO2 nanomaterials were then modified on the surface of the CNC / CF composite material by hydrothermal reaction. Copper atoms were embedded in the CeO2 lattice to construct bifunctional active centers, which endowed a single electrode with the ability to simultaneously recognize pesticides with different characteristics. Combined with the porous substrate of CNC / CF, the sensitivity and selectivity of dual pesticide detection were synergistically improved, providing an effective technical method and approach for pesticide residue detection electrodes.

[0035] 2. The prepared composite pesticide sensing electrode has strong anti-interference ability, good stability and high sensitivity. It can detect the residues of two pesticides with very different characteristics in a timely and rapid manner. It is suitable for the rapid and accurate detection of the content of multiple pesticide residues in agricultural production processes and on agricultural products such as fruits and vegetables. Attached Figure Description

[0036] Figure 1 SEM images of unmodified CNC / CF and Cu / CeO2@CNC / CF composite pesticide sensing electrode materials.

[0037] Figure 2 EDS spectrum of Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0038] Figure 3 The image shows the XRD pattern of the Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0039] Figure 4 XPS image of Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0040] Figure 5 The graph shows the performance test results of the Cu / CeO2@CNC / CF composite pesticide sensing electrode.

[0041] Figure 6 The standard curve of pesticide concentration versus current response peak value for Cu / CeO2@CNC / CF composite pesticide sensing electrode.

[0042] Figure 7 This image shows the stability and anti-interference performance of the Cu / CeO2@CNC / CF composite pesticide sensing electrode for rapid detection of pesticide residues in solution. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0044] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0046] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0047] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0048] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example 1

[0049] This embodiment provides a method for preparing a composite pesticide sensing electrode. The method involves activating a CNC (carbon nanocoil with a spatial helical structure), modifying the activated carbon nanocoil with CF (carbon foam) to obtain a CNC / CF composite material, and then modifying 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.

[0050] The activation of the CNC includes the following steps:

[0051] X1. Place 40mg of CNC in a transparent glass reagent bottle, add 30ml of concentrated nitric acid, and immerse the CNC in the concentrated nitric acid to obtain a CNC dispersion.

[0052] X2. Seal a transparent glass reagent bottle and place it in the dark for 3 days to allow the CNC to be activated. Then use a vacuum filtration device to separate the CNC from the concentrated nitric acid solution.

[0053] X3. Clean the separated CNC with deionized water and anhydrous ethanol 5-10 times in sequence, and then dry the cleaned CNC in an oven at 60℃ for later use.

[0054] Activated CNC annealed modified CF includes the following steps:

[0055] Y1. Add 40mg of activated CNC to a beaker containing 15ml of anhydrous ethanol to prepare a dispersion.

[0056] Y2. Add melamine foam to a beaker and immerse it in the dispersion. Sonicate for 30 minutes to allow CNC to adhere to the surface of the melamine foam. After sonication, separate (remove) the melamine foam.

[0057] Y3. The separated melamine foam was dried in an oven at 60°C for 3 hours. The completely dried melamine foam was placed in a tube furnace and annealed at 700°C for 3 hours under an inert atmosphere (Ar) to carbonize the foam. After cooling, carbon nanotube coil modified carbon foam (CNC / CF composite material) was obtained.

[0058] like Figure 1 (a) Figure 1 (b) shows the SEM image of the unmodified CNC / CF, which reveals that the CNC (spiral) granules are uniformly dispersed and connected to the surface and pores of the CF (porous framework), forming a three-dimensional interpenetrating structure. This close contact and connection effectively bridges the CF framework, constructing a continuous, low-resistance conductive network path, which can significantly improve the electron transport capability of the composite material.

[0059] CNC (carbon nanotubes) possess excellent electrical conductivity, superior mechanical properties, and physicochemical stability. Their high-curvature surface strongly traps pesticide molecules, and their nano-entangled structure forms an ultrafast electron transport chain. Meanwhile, the three-dimensional, interconnected macroporous framework of CF (carbon nanotubes) overcomes mass transfer limitations, enabling rapid bulk diffusion and interfacial enrichment of pesticide molecules. The combination of these two elements creates a synergistic effect on the porous substrate, forming a cascaded enhanced network of "molecular trapping-electron transport-ion diffusion." This structural coupling allows the electrode to overcome the traditional material trade-off between "conductivity and adsorption." With the assistance of copper doping to regulate the band structure, both sensitivity and selectivity for dual pesticide detection are ultimately achieved.

[0060] The surface modification of CNC / CF composite materials with Cu / CeO2 nanomaterials includes the following steps:

[0061] Z1. Prepare a precursor solution containing Cu and Ce. Place copper nitrate (Cu(NO3)2·3H2O), cerium nitrate (Ce(NO3)3·6H3O), and sodium hydroxide in a beaker, add 10 ml of deionized water, and stir for 2 min until the solutes are completely dissolved to obtain a precursor solution containing copper and cerium. The molar ratio of Ce to Cu in the precursor solution is 5:1.

[0062] Z2. Immerse the CNC / CF composite material in the precursor solution, and place the beaker containing the precursor solution and CNC / CF into an ultrasonic machine for ultrasonic treatment for 10 minutes to ensure that the precursor solution and CNC / CF are fully mixed and in contact.

[0063] Z3. Transfer the mixed system obtained in step Z2 to a hydrothermal reactor, place the reactor in an electric heating drying oven and hydrothermally react at 150~180℃ for 6~12h to grow Cu / CeO2 nanomaterials on the surface of CNC / CF composite material.

[0064] Z4. The solid material was separated by a vacuum filter and washed with deionized water 5-10 times. Then it was dried in an oven at 60°C for 6 hours to obtain the Cu / CeO2@CNC / CF composite pesticide sensing electrode.

[0065] like Figure 1 (c) Figure 1 (d) shows 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 preserved, proving that the hydrothermal process did not damage the substrate stability. Cu / CeO2 nanomaterials are uniformly coated on the CNC / CF surface at high density, forming a continuous capping layer. The nanoparticles are tightly attached to the carbon framework, ensuring electron transport across the interface; the CF pores are not blocked, maintaining high specific surface area active sites. This composite structure provides a synergistically optimized conductive network and reaction interface for pesticide molecule diffusion and electrochemical response.

[0066] This application constructs bifunctional active centers by embedding copper atoms into the CeO2 lattice: oxygen vacancy-cerium sites synergistically catalyze the oxidation reaction of the benzimidazole ring in carbendazim, generating a significantly enhanced oxidation peak current in the 0.8–1.1 V range (positively correlated with concentration); while copper-doped sites specifically bind to the nitro groups of chlorantraniliprole, resulting in selective suppression of the characteristic reduction peak current in the -0.2–0 V range (negatively correlated with concentration). These two mechanisms are naturally decoupled in terms of potential window and response mode (one increasing, one decreasing), endowing a single electrode with the ability to simultaneously recognize pesticides with vastly different properties. Through the synergistic effect of copper doping defects and the CNC / CF hierarchical structure, a synergistic leap in the detection sensitivity and selectivity of two chemically distinct pesticides is achieved. Example 2

[0067] This embodiment provides a Cu / CeO2@CNC / CF composite pesticide sensing electrode prepared by the method described in Example 1.

[0068] like Figure 2 As shown, by Figure 2 (a) It can be seen that the Cu / CeO2@CNC / CF composite pesticide sensing electrode material is formed by hydrothermal growth of Cu / CeO2 composite material on the CNC / CF surface, which proves the effective synthesis of the composite pesticide sensing electrode material. Figure 2 (b) It can be seen that the Cu / CeO2 nanolayer forms a continuous coverage on the surface of the CNC / CF framework, completely shielding the X-ray signal of the underlying carbon framework and blocking the exposure path of C elements, thus resulting in C element vacancies. This confirms that the hydrothermal synthesis successfully achieved the coating of Cu / CeO2 material on the CNC / CF framework. Figure 2 (c) Figure 2 (d) Figure 2 (e) It can be seen that O, Ce and Cu elements were successfully synthesized on the CNC / CF surface. Figure 2 The peak intensity of the element in (f) shows that the cerium content is about 10 times that of copper, which verifies the successful doping of copper and also verifies the successful synthesis of Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0069] The XRD pattern of the Cu / CeO2@CNC / CF composite pesticide sensing electrode is as follows: Figure 3 As shown, by Figure 3 It can be seen that, compared with the XRD peak of unmodified CNC / CF, the XRD peak of Cu / CeO2@CNC / CF composite pesticide sensing electrode material is basically consistent with the peak of CuO standard card (PDF#45-0937) and CeO2 standard card (PDF#43-1002), which further proves the successful doping of copper and the effective synthesis of Cu / CeO2@CNC / CF composite pesticide sensing electrode material.

[0070] XPS spectra of Cu / CeO2@CNC / CF composite pesticide sensing electrode material are as follows: Figure 4 As shown, Figure 4 As shown in (a), the characteristic peaks of C–C and C=O in the C1s spectrum indicate that the carbon-based framework 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 presence of Cu–O and O–H peaks in the O1s spectrum indicates the presence of copper oxide and hydroxyl groups on the surface of the composite material. This characteristic proves that copper has combined with the oxygen environment, forming potential doping sites that facilitate interaction with specific functional groups of pesticide molecules; for example... Figure 4 As shown in (c), the Ce3d spectrum simultaneously contains Ce 4+ With Ce 3+ The characteristic peaks indicate the presence of numerous oxygen vacancies in the CeO2 lattice. This means that the present invention induces the generation of oxygen vacancies by embedding copper atoms into the CeO2 lattice, thereby constructing a bifunctional active center of "oxygen vacancy-cerium site," which can synergistically catalyze the oxidation reaction of the benzimidazole ring in carbendazim. Figure 4 As shown in (d), Cu2p appears in the Cu2p spectrum at 933 eV and 953 eV. 3 / 2 With Cu2p 1 / 2 Characteristic peaks, accompanied by distinct satellite peaks, indicate that copper is mainly in the form of Cu. 2+ The CuO component exists in the form of copper doping. Combined with the O1s analysis results, it can be confirmed that copper has been successfully doped into the CeO2 lattice and becomes a specific binding site. This site can specifically bind to the nitro group of the chlorantraniliprole molecule.

[0071] pass Figure 4 XPS analysis not only verified the existence of carbon-based structure, CeO2 oxygen vacancies, and Cu doping state in the composite material of this invention, but also proved that the copper doping-induced bifunctional active centers form a naturally decoupled response mode (one increasing and one decreasing) within the redox potential window. Combined with the hierarchical conductive structure of CNC / CF, simultaneous identification of pesticides with vastly different chemical properties was achieved, significantly improving the sensitivity and selectivity of the detection. Example 3

[0072] This embodiment provides the application of the Cu / CeO2@CNC / CF composite pesticide sensing electrode from Example 2, specifically its application in the detection of pesticide residues in aqueous solutions.

[0073] The pesticides in question are chlorantraniliprole and carbendazim.

[0074] The steps for detecting pesticide residues in aqueous solutions using the Cu / CeO2@CNC / CF composite pesticide sensing electrode are as follows:

[0075] a. Add 1 μl, 3 μl, 5 μl, 10 μl, 20 μl, 35 μl, 70 μl, 90 μl, 120 μl, 150 μl, 200 μl up to 3000 μl of pesticide standard solution to 100 mL of electrolyte (prepared with PBS phosphate buffer: 0.1 mol / L sodium chloride, 0.01 mol / L Na2HPO4, 0.01 mol / L KH2PO4, and adjust the pH of the electrolyte to 6), respectively, so that the pesticide concentration range in the detection system is 0~300 μM. A three-electrode system was constructed by fixing the Cu / CeO2@CNC / CF composite pesticide sensing electrode firmly with a polytetrafluoroethylene platinum sheet electrode clamp to obtain the electrochemical sensing working electrode, using a silver chloride electrode as the reference electrode, and a platinum sheet electrode as the auxiliary electrode. The DPV test method of the three-electrode system was used for testing. The Cu / CeO2@CNC / CF composite pesticide sensing electrode was placed in the electrolyte containing PBS buffer and standard solutions of pesticides with different concentrations for current-voltage scanning. The voltage window was -1 to 1.5V. During the scanning, the current value generated on the electrode surface with voltage change corresponding to different pesticide concentrations was recorded.

[0076] like Figure 5 As shown, Figure 5 (a) DPV curves for simultaneous detection of pesticides chlorantraniliprole and carbendazim. Figure 5 (b) DPV curves for chlorantraniliprole alone using gradient detection. Figure 5 (c) shows the DPV curves for carbendazim alone using gradient detection. From Figure 5 (a) It can be seen that the Cu / CeO2@CNC / CF composite pesticide sensing electrode can simultaneously detect the pesticides chlorantraniliprole and carbendazim, with a linear range of 100nM~40μM and no mutual interference. Figure 5 (b) Figure 5 (c) This demonstrates that the Cu / CeO2@CNC / CF composite pesticide sensing electrode can detect chlorantraniliprole and carbendazim separately, and the response value of the separate detection changes with the increase of pesticide concentration. Chlorantraniliprole's reduction reaction is hindered by the binding of the nitro group to the copper active site (forming an electron transfer barrier), resulting in a monotonically decreasing reduction peak current value in the -0.2~0V potential range with increasing concentration; while carbendazim's reduction reaction in the 0.8~1.1V range is hindered by the catalytic oxidation of the benzimidazole ring (oxygen vacancy -CeO2). 3+ / Ce 4+ (Mediated by) the oxidation peak current value in the potential range of 0.8~1.1V increases linearly with increasing concentration. The linear range for chlorantraniliprole detection is 100nM~50μM, and the linear range for carbendazim detection is 100nM~300μM.

[0077] During the detection process, the current response value can be detected in just 5 minutes. It has a low detection limit and high sensitivity, enabling rapid on-site detection of two pesticide residues with very different characteristics.

[0078] b. Using the concentration of the pesticide standard solution as the abscissa and the corresponding peak current response as the ordinate, a standard curve was created by fitting a linear equation using Origin software. The constructed linear equation is: Ⅰ p =a+bX Pesticide , where X Pesticide The concentration of pesticide content, I p denoted as the peak value of the current response, a is the intercept of the linear regression equation, used to characterize the background current signal under zero concentration conditions; b is the slope of the linear regression equation, used to characterize the sensitivity of the current response to changes in pesticide concentration.

[0079] like Figure 6 As shown, Figure 6 (a) shows the linear relationship between the concentration of chlorantraniliprole in a single gradient detection method and the peak current. Figure 6 (b) shows the linear relationship between the concentration of carbendazim in a single gradient detection and the peak current. The regression equation for the change in current response for chlorantraniliprole detection is I = 4.54 - 0.041X. Chlorfenobenzene The correlation coefficient was 0.998, X Chlorfenobenzene The concentration of chlorantraniliprole; the regression equation for the change in current response value for detecting carbendazim is I = 2.145 + 0.00128X. Carbendazim The correlation coefficient was 0.992, X Carbendazim The concentration of carbendazim is given. Based on the regression equation above, it can be concluded that the Cu / CeO2@CNC / CF composite pesticide sensing electrode exhibits good detection performance for the pesticides chlorantraniliprole and carbendazim.

[0080] c. For the detection of pesticide residues in the sample, the standard solutions of different pesticide concentrations in step a are replaced with the test aqueous solution, and the detection is performed according to the method in step a. The corresponding current response value is obtained and substituted into the linear equation constructed in step b to calculate the pesticide residue content in the test aqueous solution.

[0081] Stability testing of Cu / CeO2@CNC / CF composite pesticide sensing electrode:

[0082] Add 40 μl of a standard solution of pesticides chlorantraniliprole and carbendazim to 100 mL of electrolyte, and repeat the DPV test 10 times. See [link to DPV test]. Figure 7 (a) It can be seen that the composite pesticide sensing electrode prepared by this method has good stability.

[0083] Anti-interference test of Cu / CeO2@CNC / CF composite pesticide sensing electrode:

[0084] A Cu / CeO2@CNC / CF composite pesticide sensing electrode was placed in 100 mL of electrolyte, which was pre-filled with 50 μl of standard solutions of the pesticides chlorantraniliprole and carbendazim. Interfering agents, including glufosinate, glyphosate, dichlorvos, deltamethrin, thiophanate-methyl, glucose, Cd(II), and Pb(II), were then added sequentially to the electrolyte. Two DPV tests were performed for each interfering agent added to obtain the detection curve under interference conditions. (See [link to relevant documentation]). Figure 7 (b) The vertical axis represents the ratio of the current value after adding the interfering substance to the current value without adding the interfering substance. It can be seen from the figure that this composite pesticide sensing electrode has a good anti-interference ability.

[0085] In the stability and anti-interference tests, the electrolyte was 100 mL of PBS phosphate buffer containing 0.1 mol / L sodium chloride, 0.01 mol / L K2HPO4, 0.01 mol / L KH2PO4, and pH 6; the pesticide concentration was 40 μM.

[0086] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite pesticide sensing electrode, characterized in that: The preparation method involves activating CNC, annealing and modifying CF with activated CNC to obtain CNC / CF composite material, and then modifying Cu / CeO2 nanomaterials on the surface of CNC / CF composite material through hydrothermal reaction to obtain Cu / CeO2@CNC / CF composite pesticide sensing electrode. The CNC is a carbon nanotube coil; The CF is carbon foam; The activated CNC annealed modified CF includes the following steps: Y1. Add the activated CNC to a container filled with anhydrous ethanol to obtain a dispersion. Y2. Add melamine foam to a container and immerse it in the dispersion. Use ultrasound to make CNC adhere to the surface of the melamine foam and separate the melamine foam. Y3. The separated melamine foam is dried, and then subjected to high-temperature annealing under the protection of inert gas to carbonize the melamine foam. After cooling, CNC / CF composite material is obtained.

2. The method for preparing the composite pesticide sensing electrode according to claim 1, characterized in that: The activation of the CNC includes the following steps: X1. Add CNC and concentrated nitric acid to the container in sequence, and immerse CNC in concentrated nitric acid to obtain CNC dispersion; X2. Place in a sealed container away from light. After the CNC is activated, separate the activated CNC. X3. Clean the separated CNC with deionized water and anhydrous ethanol in sequence, and then dry it for later use.

3. The method for preparing the composite pesticide sensing electrode according to claim 1, characterized in that: The surface modification of the CNC / CF composite material with Cu / CeO2 nanomaterials includes the following steps: Z1. Prepare a precursor solution containing Cu and Ce; Z2. Immerse the CNC / CF composite material in the precursor solution and ultrasonically treat it to ensure that the precursor solution and CNC / CF are fully mixed and in contact. Z3. Transfer the mixed system obtained in step Z2 to a hydrothermal reactor, and grow Cu / CeO2 nanomaterials on the surface of the CNC / CF composite material through hydrothermal reaction. Z4. The solid material was separated, washed with deionized water, and then dried to obtain the Cu / CeO2@CNC / CF composite pesticide sensing electrode.

4. The method for preparing the composite pesticide sensing electrode according to claim 3, 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 solutes are completely dissolved to obtain a precursor solution containing copper and cerium. The molar ratio of Ce to Cu in the precursor solution is 5:

1.

5. A composite pesticide sensing electrode, characterized in that: The Cu / CeO2@CNC / CF composite pesticide sensing electrode was prepared by the method described in any one of claims 1-4.

6. The application of composite pesticide sensing electrodes, characterized in that: Application of the Cu / CeO2@CNC / CF composite pesticide sensing electrode as described in claim 5 in the detection of pesticide residues in aqueous solution.

7. The application of the composite pesticide sensing electrode according to claim 6, characterized in that: The pesticides mentioned include: chlorantraniliprole and carbendazim.

8. The application of the composite pesticide sensing electrode according to claim 6, characterized in that: The steps for 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, the silver chloride electrode as the reference electrode, and the platinum sheet electrode as the auxiliary electrode, was placed in an electrolyte containing PBS buffer and standard solutions of pesticides at different concentrations. The DPV test method of the three-electrode system was used for testing, and the current values ​​generated on the electrode surface with voltage changes corresponding to different pesticide concentrations were recorded during the current-voltage scan. b. Based on the concentration of the pesticide standard solution and the corresponding current response peak, a standard curve is prepared and a linear equation is constructed; c. Replace the standard solutions of different pesticide concentrations in step a with the aqueous solution to be tested, and perform the detection according to the method in step a to obtain the corresponding current response value. Substitute the current response value into the linear equation constructed in step b to calculate the pesticide residue content in the aqueous solution to be tested.

Images