Hydrated copper vanadate basic microspheres modified electrode, and preparation method and application thereof

Abstract

The application discloses a kind of hydrated base formula copper vanadate microspheres modified electrode and its preparation method and application, belong to electrochemical sensor analysis detection technical field, the application is synthesized with benzoic acid as particle size control agent a series of different sizes, synthesis process controllable, structure stable, and the excellent electrocatalytic performance of hydrated base formula copper vanadate microspheres, and with the microspheres modified electrode surface, obtained a kind of to large size ascorbic acid has fast current response, linear range reasonable, high sensitivity, low detection limit of hydrated base formula copper vanadate microspheres modified electrode.In addition, hydrated base formula copper vanadate microspheres modified electrode has good reproducibility and stability, in ascorbic acid electrochemical sensor development has potential application prospect.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensor analysis and detection technology, specifically to a hydrated basic copper vanadate microsphere modified electrode, its preparation method, and its application. Background Technology

[0002] The determination of ascorbic acid is of great significance in many fields, especially in the health care, food processing, chemical, and pharmaceutical industries. Ascorbic acid is a six-carbon compound closely related to human health. It is an important and unique water-soluble vitamin that acts as a cofactor for enzymes during human metabolism, promotes the chemical processes of the brain and immune system, and indirectly participates in collagen synthesis, playing a vital role in maintaining the balance and normal function of related physiological processes in the human body. A deficiency of ascorbic acid can cause scurvy, bone deformities, and bleeding gums, while an excess can cause kidney stones, insomnia, and diarrhea. Therefore, establishing a low-cost, highly sensitive, and rapid method for the determination of ascorbic acid is of great importance.

[0003] Currently, common methods for detecting ascorbic acid include high-performance liquid chromatography (HPLC), fluorescence methods, colorimetric methods, capillary electrophoresis, chemiluminescence methods, and spectrophotometry. While these methods have certain advantages in terms of sensitivity and accuracy, most suffer from drawbacks such as cumbersome operation, long detection cycles, high reagent costs, and strong dependence on instruments, making it difficult to meet the practical needs of daily rapid detection and on-site analysis.

[0004] Electrochemical sensing technology, as an emerging detection method, has shown broad application prospects in the field of small molecule analysis due to its advantages such as simple preparation, rapid response, high sensitivity, and low cost. However, the low electrochemical activity of ascorbic acid on the surface of traditional bare electrodes limits its detection sensitivity and selectivity, seriously affecting the stability and practicality of sensor performance. To improve the electrocatalytic activity and detection performance of electrode materials, recent years have seen a large amount of research focused on the development of functional materials and the modification of electrode surfaces. Currently, various composite materials have been used to construct high-performance electrochemical sensors, such as cobalt oxide, carbon nanotubes, graphene, and their derivatives. These materials have made some progress in improving detection sensitivity and selectivity, but their synthesis processes are complex, costly, and lack stability. Summary of the Invention

[0005] This invention provides a hydrated basic copper vanadate microsphere modified electrode, its preparation method, and its application. It effectively solves the technical problems of existing modified electrodes in ascorbic acid detection, such as low detection sensitivity, small response current, lack of good electrode interface stability, narrow detection range, and large interference. This invention uses benzoic acid to regulate a solvothermal reaction to synthesize a hydrated basic copper vanadate microsphere that can be synthesized in a controllable manner, has a stable structure, and excellent electrocatalytic performance. Using the above microspheres to modify a glassy carbon electrode, high sensitivity, wide linear range, and good selectivity for ascorbic acid electrochemical detection are achieved.

[0006] The first objective of this invention is to provide a method for preparing a hydrated basic copper vanadate microsphere modified electrode, comprising the following steps:

[0007] With Cu 2+ Aqueous solutions of the source and VO3 with a pH of 4-7 - The aqueous solution of the source is used as raw material, mixed to obtain a suspension, and then thoroughly mixed with benzoic acid as particle size control agent and anhydrous ethanol and N,N-dimethylformamide as mixed solvents. The mixture is then subjected to a solvothermal reaction at 80℃~120℃ to obtain hydrated basic copper vanadate microspheres.

[0008] The hydrated basic copper vanadate microspheres were prepared into a microsphere suspension, and the microsphere suspension was coated on the surface of a bare electrode and evaporated at room temperature to obtain a hydrated basic copper vanadate microsphere modified electrode.

[0009] In a preferred embodiment, the concentration of benzoic acid is 0.3 mM to 0.6 mM, and the Cu... 2+ VO3 - The ratio of benzoic acid to benzoic acid is 0.1 mmol to 1.0 mmol: 0.05 mmol to 0.3 mol: 24 mL.

[0010] In a preferred embodiment, the hydrated basic copper vanadate microspheres have a particle size of 0.1 μm to 3.0 μm, more preferably 0.4 μm to 2.5 μm.

[0011] In a preferred embodiment, the mass percentage of the hydrated basic copper vanadate microspheres modified with the electrode is 0.001% to 0.02%.

[0012] In a preferred embodiment, the bare electrode is a glassy carbon electrode, a gold electrode, a carbon paste electrode, or FTO conductive glass.

[0013] As a preferred embodiment, the microsphere suspension is prepared by dispersing the hydrated basic copper vanadate microspheres and Nafion solution in anhydrous ethanol and sonicating to obtain the microsphere suspension.

[0014] In a preferred embodiment, the Nafion solution has a mass concentration of 5%, and the ratio of the hydrated basic copper vanadate microspheres, Nafion solution, and anhydrous ethanol is 5 mg: 4 μL to 6 μL: 1 mL.

[0015] In a preferred embodiment, the solvothermal reaction time is 12h~24h. After the solvothermal reaction is completed, the mixture is filtered to obtain a precipitate, which is washed with ethanol and N,N-dimethylformamide and dried under vacuum at 60℃~80℃ to obtain hydrated basic copper vanadate microspheres.

[0016] In a preferred embodiment, the evaporation time at room temperature is 1 hour to 5 hours.

[0017] A second objective of this invention is to provide a hydrated basic copper vanadate microsphere modified electrode, prepared by any of the methods described above.

[0018] The third objective of this invention is to provide an application of the above-mentioned hydrated basic copper vanadate microsphere modified electrode in ascorbic acid detection.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention provides a method for preparing a hydrated basic copper vanadate microsphere modified electrode, using Cu... 2+ Aqueous solution of source and VO3 - Using an aqueous solution of the source as a raw material and benzoic acid as a particle size modifier, hydrated basic copper vanadate microspheres were obtained through a solvothermal reaction in a mixed solvent of ethanol and a polar aprotic solvent. The hydrated basic copper vanadate microspheres were then prepared into a microsphere suspension, which was coated onto the surface of a bare electrode and evaporated at room temperature to obtain a hydrated basic copper vanadate microsphere-modified electrode. This invention synthesizes a series of hydrated basic copper vanadate microspheres of different sizes using benzoic acid as a particle size modifier. These microspheres exhibit controllable synthesis processes, stable structures, and excellent electrocatalytic performance. Modifying the electrode surface with these microspheres yields a hydrated basic copper vanadate microsphere-modified electrode exhibiting rapid current response, a reasonable linear range, high sensitivity, and a low detection limit for large-sized ascorbic acid. Furthermore, the hydrated basic copper vanadate microsphere-modified electrode demonstrates good reproducibility and stability, showing potential application prospects in the development of ascorbic acid electrochemical sensors.

[0021] The synthesis process of this invention is mild and highly controllable. The electrode modified with hydrated basic copper vanadate microspheres exhibits a large electrode response current and a high signal-to-noise ratio; it has a wide detection range of 0.001 mM to 2.5 mM, with significantly improved sensitivity. The hydrated basic copper vanadate microsphere modified electrode also demonstrates good selectivity for ascorbic acid and is unaffected by Na+ during detection. + Mg 2+Interference from hydroquinone and acetaminophen. The electrode modified with hydrated basic copper vanadate microspheres exhibits good long-term cycling stability. The relative standard deviations of the two redox peaks, cvp1 and cvp2, in 20 cycles are 3.76% and 3.04%, respectively, both less than 4%.

[0022] The hydrated basic copper vanadate microsphere modified electrode provided by this invention has a simple preparation process and is suitable for low-cost mass production of sensors. Attached Figure Description

[0023] Figure 1 The images show the XRD patterns of the hydrated basic copper vanadate microsphere modified electrodes prepared in Examples 1 to 4 of this invention.

[0024] Figure 2 The images shown are SEM images of hydrated basic copper vanadate microspheres prepared in Examples 1 to 4 of this invention, where A is Example 4, B is Example 3, C is Example 2, and D is Example 1.

[0025] Figure 3 The CVs diagrams are of the hydrated basic copper vanadate microsphere modified electrode prepared in Example 1 of the present invention and the bare electrode of Comparative Example 1.

[0026] Figure 4 The image shows the CVs diagrams of the hydrated basic copper vanadate microsphere modified electrodes prepared in Examples 1 to 4 of this invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0028] In response to the shortcomings mentioned in the background of this invention: First, commonly used methods for detecting ascorbic acid suffer from drawbacks such as cumbersome operation, long detection cycle, high reagent cost, and strong dependence on instruments, making it difficult to meet the practical needs of daily rapid detection and on-site analysis; Second, for electrochemical sensing technology, the low electrochemical activity of ascorbic acid on the surface of traditional bare electrodes limits its detection sensitivity and selectivity, severely affecting the stability and practicality of sensor performance; Third, while high-performance electrochemical sensors can be constructed by modifying bare electrodes with composite materials such as cobalt oxide, carbon nanotubes, graphene, and their derivatives, the synthesis process is complex, costly, and lacks stability. Based on the above technical problems, this invention provides a hydrated basic copper vanadate microsphere modified electrode, its preparation method, and its application.

[0029] The technical solution of the present invention will be analyzed and described in detail below.

[0030] This invention first provides a method for preparing a hydrated basic copper vanadate microsphere modified electrode, comprising the following steps:

[0031] With Cu 2+ Aqueous solutions of the source and VO3 with a pH of 4-7 - The aqueous solution of the source is used as raw material, mixed to obtain a suspension, and then thoroughly mixed with benzoic acid as particle size control agent and anhydrous ethanol and N,N-dimethylformamide as mixed solvents. The mixture is then subjected to a solvothermal reaction at 80℃~120℃ to obtain hydrated basic copper vanadate microspheres.

[0032] The hydrated basic copper vanadate microspheres were prepared into a microsphere suspension, and the microsphere suspension was coated on the surface of a bare electrode and evaporated at room temperature to obtain a hydrated basic copper vanadate microsphere modified electrode.

[0033] In the above technical solution, a series of hydrated basic copper vanadate microspheres of different sizes were synthesized using benzoic acid as a particle size control agent. These microspheres exhibited controllable synthesis processes, stable structures, and excellent electrocatalytic performance. The electrode surface was then modified with these microspheres to obtain a hydrated basic copper vanadate microsphere-modified electrode exhibiting rapid current response to large-sized ascorbic acid, a reasonable linear range, high sensitivity, and a low detection limit. Furthermore, the hydrated basic copper vanadate microsphere-modified electrode demonstrates good reproducibility and stability.

[0034] It should be noted that the present invention can also use p-hydroxybenzoic acid or phthalic acid as particle size control agents, which have similar particle size control effects on hydrated basic copper vanadate microspheres.

[0035] Regarding the pH value mentioned above, in this invention, VO 3- The pH of the source solution needs to be controlled between 4 and 7, which is a key condition for synthesizing hydrated basic copper vanadate microspheres with stable structure and controllable particle size. If the pH is below 4, VOCs will... 3- Protonation easily occurs, forming other vanadium species, leading to abnormal reaction or the formation of non-spherical impurities; if the pH is higher than 7, Cu... 2+ and VO 3- It readily forms hydroxide precipitates with OH⁻, hindering orderly crystal growth and leading to uneven particle size or structural damage. Therefore, outside this pH range, it will be difficult to obtain the desired spherical products, and effective control of microsphere structure and properties cannot be achieved.

[0036] To prepare hydrated basic copper vanadate microspheres with controllable morphology and particle size, the concentration of benzoic acid was 0.3 mM to 0.6 mM, and the Cu... 2+ VO3 - The ratio of benzoic acid to benzoic acid is 0.1 mmol to 1.0 mmol: 0.05 mmol to 0.3 mol: 24 mL.

[0037] To further improve the sensitivity and stability of the hydrated basic copper vanadate microsphere-modified electrode, the particle size of the hydrated basic copper vanadate microspheres is 0.1 μm to 3.0 μm, more preferably 0.4 μm to 2.5 μm. Particle size has a significant impact on the electrochemical detection performance of the hydrated basic copper vanadate microsphere-modified electrode. If the microsphere particle size is less than 0.1 μm, although the specific surface area increases, which is beneficial for increasing the number of reaction sites, it also leads to severe microsphere aggregation, uneven distribution on the electrode surface, and reduced electron and proton conduction efficiency, resulting in unstable response current and poor reproducibility. If the particle size is greater than 3.0 μm, the excessively large microsphere size will significantly reduce the specific surface area, decrease the number of active sites, and lengthen the charge transport path, leading to slower reaction kinetics, decreased electrocatalytic activity, and reduced sensitivity. Therefore, this invention controls the particle size within the range of 0.1 μm to 3.0 μm to achieve a good balance between electrode surface activity, efficient electron transfer, and stable detection performance.

[0038] To improve the detection sensitivity of ascorbic acid, the electrode was modified with hydrated basic copper vanadate microspheres at a mass percentage of 0.001% to 0.02%. When the mass percentage of hydrated basic copper vanadate microspheres is less than 0.001%, the effective catalytic material in the modification layer is insufficient, the number of active sites on the electrode surface is significantly reduced, resulting in weak electrocatalytic activity against ascorbic acid, low current response signal, and a significant decrease in detection sensitivity. When the mass percentage of hydrated basic copper vanadate microspheres is greater than 0.02%, excessive microsphere accumulation easily forms a dense thick film on the electrode surface, hindering the effective transport of electrons and protons, increasing diffusion resistance, and inhibiting the electrochemical reaction, which also leads to a decrease in current response and sensitivity. Therefore, controlling the mass percentage of microspheres within a reasonable range of 0.001% to 0.02% helps to provide sufficient active sites while maintaining good electron transport channels, thereby achieving optimal detection performance.

[0039] To effectively control the morphology and size of hydrated basic copper vanadate microspheres, N,N-dimethylformamide in the technical solution of this invention can be replaced with other types of polar aprotic solvents, such as N-methylpyrrolidone, dimethyl sulfoxide, or N,N-dimethylacetamide. In the system for synthesizing hydrated basic copper vanadate microspheres, the polar aprotic solvent not only acts as a solvent but is also a key chemical regulator for achieving specific spherical morphology and controllable size. This is mainly achieved through the weak coordination ability of the polar aprotic solvent, the regulation of solvent polarity, and the maintenance of a suitable high-temperature and high-pressure reaction environment. The polar aprotic solvents listed above, such as N-methylpyrrolidone, dimethyl sulfoxide, or N,N-dimethylacetamide, are relatively close choices and have similar effects.

[0040] It should be noted that the bare electrode used in this invention is a glassy carbon electrode, a gold electrode, a carbon paste electrode, or FTO conductive glass.

[0041] To ensure that the hydrated basic copper vanadate microspheres are modified on the electrode surface, the microsphere suspension is prepared by dispersing the hydrated basic copper vanadate microspheres and Nafion solution in anhydrous ethanol and sonicating to obtain the microsphere suspension.

[0042] To prevent the hydrated basic copper vanadate microspheres prepared in this invention from detaching from the glassy carbon electrode and to improve the stability of the electrode, the Nafion solution used in this invention has a mass concentration of 5%, and the ratio of the hydrated basic copper vanadate microspheres, Nafion solution, and anhydrous ethanol is 5 mg: 4 μL to 6 μL: 1 mL.

[0043] It should be noted that the solvothermal reaction time is 12h~24h. After the solvothermal reaction is completed, the mixture is filtered to obtain the precipitate, which is washed with ethanol and N,N-dimethylformamide and dried under vacuum at 60℃~80℃ to obtain hydrated basic copper vanadate microspheres.

[0044] In order to improve the bonding strength between the electrode and the modification layer, thereby improving the detection sensitivity, the present invention encapsulates the microsphere suspension on the surface of the bare electrode and then evaporates it at room temperature for 1 to 5 hours.

[0045] The technical effects of the present invention will be described below with reference to specific embodiments and comparative examples.

[0046] Example 1

[0047] A method for preparing a hydrated basic copper vanadate microsphere modified electrode includes the following steps:

[0048] S1. Dissolve 0.1 mol (13 g) of NaVO3 in 120 mL of deionized water and adjust the pH to 6. This solution is designated as the first solution. Dissolve 0.6 mmol (0.104 g) of CuCl2·2H2O in 24 mL of deionized water and add 0.8 mL of the first solution to obtain a pale yellow suspension. Dissolve benzoic acid in 24 mL of ethanol to obtain a 0.6 mM benzoic acid solution, designated as the second solution. Mix the pale yellow suspension and the second solution in a 100 mL beaker, add 24 mL of N,N-dimethylformamide, and stir at 50 °C for 30 min. Then transfer the mixture to a Teflon-lined stainless steel autoclave and autoclave at 100 °C for 16 h. Filter the mixture, wash with ethanol and N,N-dimethylformamide, and vacuum dry at 80 °C for 12 h to obtain pale yellow hydrated basic copper vanadate microspheres, designated as CuVOH-1.

[0049] S2, 5 mg of CuVOH-1 and 5 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent and sonicated for 30 min to obtain a uniform suspension of hydrated basic copper vanadate microspheres, denoted as CuVOH-1 suspension. A glassy carbon electrode with a diameter of 3 mm was polished to a mirror finish using a polishing cloth and 0.3 μm alumina paste. The CuVOH-1 suspension was drop-coated onto the surface of the glassy carbon electrode, evaporated at room temperature, and allowed to dry naturally. The electrode was then washed sequentially with ethanol and deionized water to coat the surface of the glassy carbon electrode with 10 μL of CuVOH-1 suspension, resulting in a hydrated basic copper vanadate microsphere modified electrode, denoted as CuVOH-1 / GCE.

[0050] Example 2

[0051] A method for preparing a hydrated basic copper vanadate microsphere modified electrode includes the following steps:

[0052] S1. Dissolve 0.1 mol (13 g) of NaVO3 in 120 mL of deionized water and adjust the pH to 6. This solution is designated as the first solution. Dissolve 0.6 mmol (0.104 g) of CuCl2·2H2O in 24 mL of deionized water and add 0.8 mL of the first solution to obtain a pale yellow suspension. Dissolve benzoic acid in 24 mL of ethanol to obtain a 0.5 mM benzoic acid solution, designated as the second solution. Mix the pale yellow suspension and the second solution in a 100 mL beaker, add 24 mL of N,N-dimethylformamide, and stir at 50 °C for 30 min. Then transfer the mixture to a Teflon-lined stainless steel autoclave and autoclave at 100 °C for 16 h. Filter the mixture, wash with ethanol and N,N-dimethylformamide, and vacuum dry at 80 °C for 12 h to obtain pale yellow hydrated basic copper vanadate microspheres, designated as CuVOH-2.

[0053] S2, 5 mg of CuVOH-2 and 5 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent and sonicated for 30 min to obtain a uniform suspension of hydrated basic copper vanadate microspheres, denoted as CuVOH-2 suspension. A glassy carbon electrode with a diameter of 3 mm was polished to a mirror surface using a polishing cloth and 0.3 μm alumina paste. The CuVOH-2 suspension was drop-coated onto the surface of the glassy carbon electrode, evaporated at room temperature, and allowed to dry naturally. Then, it was washed sequentially with ethanol and deionized water to coat the surface of the glassy carbon electrode with 10 μL of CuVOH-2 suspension, resulting in a hydrated basic copper vanadate microsphere modified electrode, denoted as CuVOH-2 / GCE.

[0054] Example 3

[0055] A method for preparing a hydrated basic copper vanadate microsphere modified electrode includes the following steps:

[0056] S1. Dissolve 0.1 mol (13 g) of NaVO3 in 120 mL of deionized water and adjust the pH to 6. This solution is designated as the first solution. Dissolve 0.6 mmol (0.104 g) of CuCl2·2H2O in 24 mL of deionized water and add 0.8 mL of the first solution (A) to obtain a pale yellow suspension. Dissolve benzoic acid in 24 mL of ethanol to obtain a 0.4 mM benzoic acid solution, designated as the second solution. Mix the pale yellow suspension and the second solution in a 100 mL beaker, add 24 mL of N,N-dimethylformamide, and stir at 50 °C for 30 min. Then transfer the mixture to a Teflon-lined stainless steel autoclave and autoclave at 100 °C for 16 h. Filter the mixture, wash with ethanol and N,N-dimethylformamide, and vacuum dry at 80 °C for 12 h to obtain pale yellow hydrated basic copper vanadate microspheres, designated as CuVOH-3.

[0057] S2, 5 mg of CuVOH-3 and 5 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent and sonicated for 30 min to obtain a uniform suspension of hydrated basic copper vanadate microspheres, denoted as CuVOH-3 suspension. A glassy carbon electrode with a diameter of 3 mm was polished to a mirror finish using a polishing cloth and 0.3 μm alumina paste. The CuVOH-3 suspension was drop-coated onto the surface of the glassy carbon electrode, evaporated at room temperature, and allowed to dry naturally. The electrode was then washed sequentially with ethanol and deionized water to coat the surface of the glassy carbon electrode with 10 μL of CuVOH-3 suspension, resulting in a hydrated basic copper vanadate microsphere modified electrode, denoted as CuVOH-3 / GCE.

[0058] Example 4

[0059] A method for preparing a hydrated basic copper vanadate microsphere modified electrode includes the following steps:

[0060] S1. Dissolve 0.1 mol (13 g) of NaVO3 in 120 mL of deionized water and adjust the pH to 6. This solution is designated as the first solution. Dissolve 0.6 mmol (0.104 g) of CuCl2·2H2O in 24 mL of deionized water and add 0.8 mL of the first solution to obtain a pale yellow suspension. Dissolve benzoic acid in 24 mL of ethanol to obtain a 0.3 mM benzoic acid solution, designated as the second solution. Mix the pale yellow suspension and the second solution in a 100 mL beaker, add 24 mL of N,N-dimethylformamide, and stir at 50 °C for 30 min. Then transfer the mixture to a Teflon-lined stainless steel autoclave and autoclave at 100 °C for 16 h. Filter the mixture, wash with ethanol and N,N-dimethylformamide, and vacuum dry at 80 °C for 12 h to obtain pale yellow hydrated basic copper vanadate microspheres, designated as CuVOH-4.

[0061] S2, 5 mg of CuVOH-4 and 5 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent and sonicated for 30 min to obtain a uniform suspension of hydrated basic copper vanadate microspheres, denoted as CuVOH-4 suspension. A glassy carbon electrode with a diameter of 3 mm was polished to a mirror surface using a polishing cloth and 0.3 μm alumina paste. The CuVOH-4 suspension was drop-coated onto the surface of the glassy carbon electrode, evaporated at room temperature, and allowed to dry naturally. Then, it was washed sequentially with ethanol and deionized water to coat the surface of the glassy carbon electrode with 10 μL of CuVOH-4 suspension, obtaining a hydrated basic copper vanadate microsphere modified electrode, denoted as CuVOH-4 / GCE.

[0062] Example 5

[0063] A method for preparing a hydrated basic copper vanadate microsphere modified electrode includes the following steps:

[0064] S1. Dissolve 0.05 mmol of NaVO3 in 120 mL of deionized water and adjust the pH to 4, designating this as the first solution. Dissolve 0.1 mmol of CuCl2·2H2O in 24 mL of deionized water and add 0.8 mL of the first solution to obtain a pale yellow suspension. Dissolve benzoic acid in 24 mL of ethanol to obtain a 0.6 mM benzoic acid solution, designated as the second solution. Mix the pale yellow suspension and the second solution in a 100 mL beaker, add 24 mL of N,N-dimethylformamide, and stir at 50 °C for 30 min. Then transfer the mixture to a Teflon-lined stainless steel autoclave and autoclave at 80 °C for 24 h. Filter the mixture, wash with ethanol and N,N-dimethylformamide, and vacuum dry at 80 °C for 12 h to obtain pale yellow hydrated basic copper vanadate microspheres, designated CuVOH-5.

[0065] S2, 5 mg of CuVOH-5 and 4 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent and sonicated for 30 min to obtain a uniform suspension of hydrated basic copper vanadate microspheres, denoted as CuVOH-5 suspension. A glassy carbon electrode with a diameter of 3 mm was polished to a mirror finish using a polishing cloth and 0.3 μm of alumina paste. The CuVOH-5 suspension was drop-coated onto the surface of the glassy carbon electrode, evaporated at room temperature, and allowed to dry naturally. Then, it was washed sequentially with ethanol and deionized water to coat the surface of the glassy carbon electrode with 10 μL of CuVOH-5 suspension, resulting in a hydrated basic copper vanadate microsphere modified electrode, denoted as CuVOH-5 / GCE.

[0066] Example 6

[0067] A method for preparing a hydrated basic copper vanadate microsphere modified electrode includes the following steps:

[0068] S1. Dissolve 0.3 mol of NaVO3 in 120 mL of deionized water and adjust the pH to 7, designating this as the first solution. Dissolve 1.0 mmol of CuCl2·2H2O in 24 mL of deionized water and add 0.8 mL of the first solution to obtain a pale yellow suspension. Dissolve benzoic acid in 24 mL of ethanol to obtain a 0.6 mM benzoic acid solution, designated as the second solution. Mix the pale yellow suspension and the second solution in a 100 mL beaker, add 24 mL of N,N-dimethylformamide, and stir at 50 °C for 30 min. Then transfer the mixture to a Teflon-lined stainless steel autoclave and autoclave at 120 °C for 12 h. Filter the mixture, wash with ethanol and N,N-dimethylformamide, and vacuum dry at 80 °C for 12 h to obtain pale yellow hydrated basic copper vanadate microspheres, designated CuVOH-6.

[0069] S2, 5 mg of CuVOH-6 and 6 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent and sonicated for 30 min to obtain a uniform suspension of hydrated basic copper vanadate microspheres, denoted as CuVOH-6 suspension. A glassy carbon electrode with a diameter of 3 mm was polished to a mirror surface using a polishing cloth and 0.3 μm alumina paste. The CuVOH-6 suspension was drop-coated onto the surface of the glassy carbon electrode, evaporated at room temperature, and allowed to dry naturally. Then, it was washed sequentially with ethanol and deionized water to coat the surface of the glassy carbon electrode with 10 μL of CuVOH-6 suspension, obtaining a hydrated basic copper vanadate microsphere modified electrode, denoted as CuVOH-6 / GCE.

[0070] To further illustrate the technical effects of the present invention, comparative examples are also provided, as follows:

[0071] Comparative Example 1

[0072] The difference from Example 1 is that only a bare glassy carbon electrode is used, without any modification.

[0073] Morphological characterization was performed on the hydrated basic copper vanadate microspheres and the modified electrode of the hydrated basic copper vanadate microspheres of the present invention and the bare electrode of Comparative Example 1. Ascorbic acid was detected using the above electrodes to compare and characterize the performance. Since the performance of Examples 1 to 6 is similar, the effects of Examples 1 to 4 are described as examples. The characterization results are as follows.

[0074] X-ray diffraction was used to analyze the crystal phase of the products prepared under different conditions. Figure 1 The XRD patterns of CuVOH-1 to CuVOH-4 prepared by adding benzoic acid at concentrations of 0.3 mM to 0.6 mM as a particle size modifier, i.e., the XRD patterns of the hydrated basic copper vanadate microsphere modified electrodes prepared in Examples 1 to 4 of this invention. Figure 1It can be seen that all diffraction peaks conform to the monoclinic Cu3V2O7(OH)2·2H2O phase with space group C2 / m, JCPDs number 80-1170, a=10.61 Å, b=5.86 Å, c=7.21 Å, α=90.0°, β=94.9°, γ=90.0°. The diffraction peaks at 12.304°, 16.764°, 17.280°, 21.683°, 24.752°, 29.556°, and 30.462° belong to the (001), (200), (110), (111), (002), (310), and (020) planes, respectively. The crystal structure diffraction peaks confirm that the product is Cu3V2O7(OH)2·2H2O and has good crystallinity.

[0075] Figure 2 These are SEM images of hydrated basic copper vanadate microspheres prepared in Examples 1-4 of this invention, where Image A is from Example 4, Image B is from Example 3, Image C is from Example 2, and Image D is from Example 1. Figure 2 It can be seen that the morphology of all samples is irregular spherical. By adding different concentrations of benzoic acid, samples with different particle sizes can be obtained. As the concentration of benzoic acid increases, the sample size gradually increases. When 0.3 mM benzoic acid is added, the size of CuVOH-4 in Example 4 is approximately 400 nm, and when 0.6 mM benzoic acid is added, the size of CuVOH-1 in Example 1 is approximately 2.5 μm.

[0076] Electrochemical detection: In a 0.1 M KCl background electrolyte, the response of the hydrated basic copper vanadate microsphere-modified electrode to detect different concentrations of ascorbic acid was tested using a colorimetric method (CV). The scan rate was 50 mV / s, and the test potential range was -1.0 V to +1.0 V. Two redox peaks, cvp1 and cvp2, were used to analyze the ascorbic acid concentration, demonstrating strong selectivity, sensitivity, and stability.

[0077] Figure 3 The images show the CVs of the hydrated basic copper vanadate microsphere-modified electrode prepared in Example 1 of this invention and the bare electrode in Comparative Example 1. Figure 3 It can be seen that the CuVOH-1 modified glassy carbon electrode, namely CuVOH-1 / GCE, differs significantly from the bare electrode in electrochemical response. CuVOH-1 / GCE exhibits two distinct pairs of redox peaks on the cyclic voltammetry curve, while the bare electrode shows no obvious current response peak, indicating that the latter has no electrocatalytic activity against ascorbic acid.

[0078] Figure 4 The images show the CVs of the hydrated basic copper vanadate microsphere-modified electrodes prepared in Examples 1-4 of this invention. Figure 4It can be seen that CuVOH microspheres of different particle sizes exhibit significant differences in their electrode current response. Among them, the CuVOH-1 modified electrode shows the strongest redox peak current, indicating that it has higher electrocatalytic activity and current response against ascorbic acid. Its anodic peak potentials are located at 0.062V and 0.218V, respectively, and its cathode peak potentials are located at -0.067V and -0.315V, respectively, demonstrating good electrochemical reversibility and interfacial activity, indicating that CuVOH-1 has superior electron transport capability. The two anodic peak potentials in Examples 2-4 are located between 0.048V and 0.062V and 0.178V and 0.218V, respectively, and the two cathode peak potentials in Examples 2-4 are located between -0.372V and -0.286V and -0.102V and -0.011V, respectively.

[0079] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. The application of a hydrated basic copper vanadate microsphere-modified electrode in ascorbic acid detection, characterized in that, The preparation method of the hydrated basic copper vanadate microsphere modified electrode includes the following steps: With Cu 2+ Aqueous solutions of the source and VO3 with a pH of 4-7 - The aqueous solution of the source was used as raw material, mixed to obtain a suspension, and benzoic acid was used as a particle size control agent. Ethanol and N,N-dimethylformamide were used as a mixed solvent, mixed thoroughly, and then subjected to a solvothermal reaction at 80℃~120℃ to obtain hydrated basic copper vanadate microspheres; the concentration of benzoic acid was 0.3mM~0.6mM, and the Cu... 2+ VO3 - The ratio of copper vanadate to benzoic acid is 0.1 mmol to 1.0 mmol: 0.05 mmol to 0.3 mol: 24 mL; the particle size of the hydrated basic copper vanadate microspheres is 0.4 μm to 2.5 μm. The hydrated basic copper vanadate microspheres were prepared into a microsphere suspension, and the microsphere suspension was coated onto the surface of a bare electrode and evaporated at room temperature to obtain a hydrated basic copper vanadate microsphere-modified electrode; the mass percentage of the hydrated basic copper vanadate microspheres was 0.001%~0.02% based on the hydrated basic copper vanadate microsphere-modified electrode. The microsphere suspension is prepared by dispersing the hydrated basic copper vanadate microspheres and Nafion solution in an ethanol solvent and sonicating to obtain the microsphere suspension; the mass concentration of the Nafion solution is 5%, and the ratio of the hydrated basic copper vanadate microspheres, Nafion solution and anhydrous ethanol is 5 mg: 4 μL~6 μL: 1 mL.

2. The application of the hydrated basic copper vanadate microsphere modified electrode according to claim 1 in ascorbic acid detection, characterized in that, The solvothermal reaction time is 12h~24h. After the solvothermal reaction is completed, the mixture is filtered to obtain the precipitate, which is washed with ethanol and N,N-dimethylformamide and dried under vacuum at 60℃~80℃ to obtain hydrated basic copper vanadate microspheres.

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