Hydrated basic copper vanadate microsphere modified electrode as well as preparation method and application thereof

Abstract

The invention discloses a hydrated basic copper vanadate microsphere modified electrode and a preparation method and application thereof, and belongs to the technical field of electrochemical sensor analysis and detection.The hydrated basic copper vanadate microsphere modified electrode is characterized in that a series of hydrated basic copper vanadate microspheres which are different in size, controllable in synthesis process, stable in structure and excellent in electro-catalytic performance are synthesized with benzoic acid as a particle size regulating agent; and modifying the surface of the electrode with the microspheres to obtain the hydrated basic cupric vanadate microsphere modified electrode which has the advantages of rapid current response to large-size ascorbic acid, reasonable linear range, high sensitivity and low detection limit. In addition, the hydrated basic copper vanadate microsphere modified electrode has good reproducibility and stability, and has potential application prospects in the development of ascorbic acid electrochemical sensors.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical sensor analysis and detection, and particularly relates to a hydrous alkali copper vanadate microsphere modified electrode as well as a preparation method and application thereof. BACKGROUND

[0002] The determination of ascorbic acid is of great significance in many fields, especially in the health, food processing, chemical and pharmaceutical industries. Ascorbic acid is a six-carbon compound closely related to human health. It is an important and special water-soluble vitamin, which acts as a co-factor for enzymes in the human metabolic process, promotes the chemical action of the brain and immune system, and indirectly participates in the synthesis of collagen, and plays an important role in maintaining the balance and normal function of related physiological processes of the human body. When the body lacks ascorbic acid, it will cause scurvy, bone deformation, and gum bleeding, while an excess of ascorbic acid will cause kidney stones, insomnia and diarrhea. Therefore, it is of great significance to establish a low-cost, high-sensitivity method for rapid determination of ascorbic acid.

[0003] At present, the commonly used detection methods of ascorbic acid include high performance liquid chromatography, fluorescence method, colorimetric method, capillary electrophoresis, chemiluminescence method and spectrophotometry. These methods have certain advantages in sensitivity and accuracy, but most of them have the disadvantages of complicated operation, long detection period, high reagent cost and strong dependence on instruments, which are difficult to meet the actual needs of daily rapid detection and on-site analysis.

[0004] As a new detection method, electrochemical sensing technology has broad application prospects in the field of small molecule analysis due to its simple preparation, rapid response, high sensitivity and low cost. However, due to the low electrochemical activity of ascorbic acid on the surface of traditional bare electrodes, the detection sensitivity and selectivity are limited, which seriously affects the stability and practicability of the sensor performance. In order to improve the electrocatalytic activity and detection performance of electrode materials, a large number of researches in recent years have focused on the development of functional materials and the modification of electrode surface. At present, a variety of composite materials have been used to construct high-performance electrochemical sensors, such as cobalt oxide, carbon nanotubes, graphene and its derivatives. These materials have made certain progress in improving the detection sensitivity and selectivity, but their synthesis process is complex, the cost is high and the stability is insufficient. SUMMARY

[0005] The application provides a hydrated copper hydroxide vanadate microsphere modified electrode and a preparation method and application thereof, effectively solves the technical problems of low detection sensitivity, small response current, lack of good electrode interface stability, narrow detection range and large influence of interfering substances of the existing modified electrode in ascorbic acid detection, the application adopts benzoic acid to regulate and control a solvent thermal reaction to synthesize a kind of hydrated copper hydroxide vanadate microsphere capable of controllable synthesis, structural stability and excellent electrocatalytic performance, and the glassy carbon electrode is modified by using the above-mentioned microsphere, so that the high sensitivity, wide linear range and good selectivity of the electrochemical detection of ascorbic acid are realized.

[0006] The first object of the application is to provide a preparation method of a hydrated copper hydroxide vanadate microsphere modified electrode, comprising the following steps: The Cu 2+ source aqueous solution and the VO3 - source aqueous solution are mixed to obtain a suspension, benzoic acid is used as a particle size regulator, anhydrous ethanol and N,N-dimethylformamide are used as mixed solvents, the mixture is uniformly mixed, and then solvent thermal reaction is carried out at 80 DEG C to 120 DEG C to obtain the hydrated copper hydroxide vanadate microsphere.

[0007] The hydrated copper hydroxide vanadate microsphere is prepared into a microsphere suspension, the microsphere suspension is wrapped on the surface of a bare electrode, and room temperature evaporation is carried out to obtain the hydrated copper hydroxide vanadate microsphere modified electrode.

[0008] As a preferred embodiment, the concentration of the benzoic acid is 0.3 mM to 0.6 mM, the Cu 2+ , the VO3 - and the benzoic acid are used in a ratio of 0.1 mmol to 1.0 mmol:0.05 mmol to 0.3 mol:24 mL.

[0009] As a preferred embodiment, the particle size of the hydrated copper hydroxide vanadate microsphere is 0.1 mu m to 3.0 mu m, and more preferably 0.4 mu m to 2.5 mu m.

[0010] As a preferred embodiment, the mass percentage of the hydrated copper hydroxide vanadate microsphere is 0.001% to 0.02% based on the hydrated copper hydroxide vanadate microsphere modified electrode.

[0011] As a preferred embodiment, the bare electrode is a glassy carbon electrode, a gold electrode, a carbon paste electrode or FTO conductive glass.

[0012] As a preferred embodiment, the preparation method of the microsphere suspension is that the hydrated copper hydroxide vanadate microsphere and a Nafion solution are dispersed in anhydrous ethanol, and ultrasonic treatment is carried out to obtain the microsphere suspension.

[0013] 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.

[0014] 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.

[0015] In a preferred embodiment, the evaporation time at room temperature is 1 hour to 5 hours.

[0016] 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.

[0017] 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.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 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.

[0019] 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 of catechol, acetaminophen. The long-term cycle stability of the copper hydroxide vanadate microsphere modified electrode is good, and the relative standard deviations of the two oxidation and reduction peaks cvp1 and cvp2 in 20 cycles are 3.76% and 3.04% respectively, both less than 4%.

[0020] The preparation process of the copper hydroxide vanadate microsphere modified electrode provided by the application is simple, and is suitable for low-cost batch sensor production. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The XRD diagram of the copper hydroxide vanadate microsphere modified electrode prepared in Embodiment 1 to Embodiment 4 of the application.

[0022] Figure 2 The SEM diagram of the copper hydroxide vanadate microsphere prepared in Embodiment 1 to Embodiment 4 of the application, wherein, A diagram is Embodiment 4, B diagram is Embodiment 3, C diagram is Embodiment 2, and D diagram is Embodiment 1.

[0023] Figure 3 The CVs diagram of the copper hydroxide vanadate microsphere modified electrode prepared in Embodiment 1 of the application and the bare electrode of Comparative Example 1.

[0024] Figure 4 The CVs diagram of the copper hydroxide vanadate microsphere modified electrode prepared in Embodiment 1 to Embodiment 4 of the application. DETAILED DESCRIPTION

[0025] In order to enable the technical personnel in the art to better understand the technical solutions of the application and to implement the same, the application will be further described below with reference to the specific embodiments and the accompanying drawings, but the embodiments are not intended to limit the application. The following test methods and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.

[0026] In view of the background art mentioned in the application, first, the conventional detection method of ascorbic acid has the disadvantages of complicated operation, long detection period, high reagent cost and strong dependence on instruments, which cannot meet the actual needs of daily rapid detection and on-site analysis; second, for the electrochemical sensing technology, the electrochemical activity of ascorbic acid on the surface of the traditional bare electrode is low, which limits the detection sensitivity and selectivity, and seriously affects the stability and practicability of the sensor performance; third, composite materials are used to modify the bare electrode to construct high-performance electrochemical sensors, such as cobalt oxide, carbon nanotubes, graphene and its derivatives, but the synthesis process is complex, the cost is high and the stability is insufficient. Based on the above technical problems, the application provides a copper hydroxide vanadate microsphere modified electrode and a preparation method and application thereof.

[0027] The technical solutions of the application will be described in detail below.

[0028] The application first provides a preparation method of a copper hydroxide vanadate microsphere modified electrode, comprising the following steps: A water-soluble solution of a Cu 2+ source and a water-soluble solution of a VO3 - source with a pH value of 4-7 are used as raw materials, mixed to obtain a suspension, and then subjected to a solvothermal reaction at 80-120 DEG C in a mixed solvent of benzoic acid as a particle size control agent and anhydrous ethanol and N,N-dimethylformamide, to obtain copper hydroxide vanadate microspheres.

[0029] The copper hydroxide vanadate microspheres are prepared into a microsphere suspension, and the microsphere suspension is wrapped on the surface of a bare electrode and evaporated at room temperature to obtain a copper hydroxide vanadate microsphere modified electrode.

[0030] In the above technical solution, a series of copper hydroxide vanadate microspheres with different sizes, controllable synthesis process, stable structure and excellent electrocatalytic performance are synthesized by using benzoic acid as a particle size control agent, and the surface of an electrode is modified with the microspheres to obtain a copper hydroxide vanadate microsphere modified electrode which has a rapid current response to large-size ascorbic acid, a reasonable linear range, high sensitivity and low detection limit. In addition, the copper hydroxide vanadate microsphere modified electrode has good reproducibility and stability.

[0031] It should be noted that the application can also use p-hydroxybenzoic acid or phthalic acid as a particle size control agent, which has a similar particle size control effect on the copper hydroxide vanadate microspheres.

[0032] For the above pH value, in the application, the pH value of the VO 3- source solution needs to be controlled between 4 and 7, which is a key condition for synthesizing copper hydroxide vanadate microspheres with stable structure and controllable particle size. If the pH value is lower than 4, the VO 3- is prone to protonation to form other vanadium species, which causes the reaction to fail to proceed normally or generates non-spherical impurities; if the pH value is higher than 7, Cu 2+ and VO 3- are prone to form hydroxide precipitates with OH⁻, which hinders the ordered growth of crystals, resulting in uneven particle size or structure damage. Therefore, it is difficult to obtain the expected spherical product and realize effective regulation of the microsphere structure and performance when the pH value exceeds the range.

[0033] In order to prepare copper hydroxide vanadate microspheres with controllable morphology and particle size, the concentration of the benzoic acid is 0.3-0.6 mM, and the amount ratio of Cu 2+ , VO3 - and benzoic acid is 0.1-1.0 mmol:0.05-0.3 mmol:24 mL.

[0034] In order to further improve the sensitivity and stability of the hydrated copper vanadate microsphere modified electrode, the particle size of the hydrated copper vanadate microsphere is 0.1-3.0 μm, and more preferably 0.4-2.5 μm. The particle size has an important influence on the electrochemical detection performance of the hydrated copper vanadate microsphere modified electrode. If the particle size of the microsphere is less than 0.1 μm, although the specific surface area is increased, which is beneficial to increase the number of reaction sites, at the same time, the microspheres will be seriously aggregated, the electrode surface is not uniform, and the electron and proton conduction efficiency is reduced, thereby causing the problems of unstable response current and poor reproducibility; if the particle size is greater than 3.0 μm, the size of the microsphere is too large, which will significantly reduce the specific surface area, reduce the active sites, and lengthen the charge transfer path, resulting in slow reaction kinetics, decreased electrocatalytic activity, and reduced sensitivity. Therefore, the particle size is controlled in the range of 0.1-3.0 μm, so as to achieve a good balance between the electrode surface activity, efficient electron transfer and stable detection performance.

[0035] In order to improve the detection sensitivity in ascorbic acid detection, the mass percentage of the hydrated copper vanadate microsphere is 0.001%-0.02% based on the hydrated copper vanadate microsphere modified electrode. When the mass percentage of the hydrated copper vanadate microsphere is less than 0.001%, the effective catalytic material in the modified layer is insufficient, the number of active sites on the electrode surface is significantly reduced, the electrocatalytic effect on ascorbic acid is weak, the current response signal is low, and the detection sensitivity is significantly reduced; when the mass percentage of the hydrated copper vanadate microsphere is greater than 0.02%, the microspheres are too much, which is easy to form a dense thick film on the electrode surface, hinder the effective transmission of electrons and protons, increase the diffusion resistance, and inhibit the electrochemical reaction, which will also cause the decrease of current response and sensitivity. Therefore, the mass percentage of the microsphere is controlled in the reasonable range of 0.001%-0.02%, which is helpful to provide sufficient active sites while maintaining a good electron transmission channel, so as to achieve the best detection performance.

[0036] In order to effectively regulate the morphology and size of the hydrated copper vanadate microsphere, the N,N-dimethylformamide in the technical scheme of the application can also be replaced by other kinds of polar aprotic solvents, such as N-methyl pyrrolidone, dimethyl sulfoxide or N,N-dimethylacetamide. In the system for synthesizing the hydrated copper vanadate microsphere, the polar aprotic solvent not only plays a role as a solvent, but also is a key chemical regulator for realizing a specific spherical morphology and controllable size. It is mainly realized by the weak coordination ability of the polar aprotic solvent, the regulation of solvent polarity and the maintenance of suitable high temperature and high pressure reaction environment. The polar aprotic solvents N-methyl pyrrolidone, dimethyl sulfoxide or N,N-dimethylacetamide listed above are closer choices, which have similar effects.

[0037] It should be noted that the bare electrode used in the present application is a glassy carbon electrode, a gold electrode, a carbon paste electrode or FTO conductive glass.

[0038] In order to ensure that the hydrated basic copper vanadate microspheres are modified on the surface of the electrode, the preparation method of the microsphere suspension is that the hydrated basic copper vanadate microspheres and a Nafion solution are dispersed in anhydrous ethanol, and ultrasonic treatment is performed to obtain the microsphere suspension.

[0039] In order to prevent the hydrated basic copper vanadate microspheres prepared in the present application from falling off from the glassy carbon electrode and improve the stability of the electrode, the mass concentration of the Nafion solution used in the present application is 5%, and the amount ratio of the hydrated basic copper vanadate microspheres, the Nafion solution and the anhydrous ethanol is 5 mg: 4-6 μL: 1 mL.

[0040] It should be noted that the time of the solvothermal reaction is 12-24 h, after the solvothermal reaction is completed, the precipitate is obtained by filtration, washed with ethanol and N,N-dimethylformamide, and vacuum dried at 60-80 °C to obtain the hydrated basic copper vanadate microspheres.

[0041] In order to improve the bonding strength of the electrode and the modified layer and thus improve the detection sensitivity, the microsphere suspension is wrapped on the surface of the bare electrode at room temperature for 1-5 h.

[0042] The technical effects of the present application will be described below in combination with specific examples and comparative examples.

[0043] Example 1 A preparation method of a hydrated basic copper vanadate microsphere modified electrode comprises the following steps: S1, 0.1 mol, i.e. 13 g of NaVO3 is dissolved in 120 mL of deionized water, the pH is adjusted to 6, and is recorded as a first solution for standby. 0.6 mmol, i.e. 0.104 g of CuCl2·2H2O is dissolved in 24 mL of deionized water, 0.8 mL of the first solution is added to obtain a light yellow suspension solution. Benzoic acid is dissolved in 24 mL of ethanol to obtain a benzoic acid solution with a concentration of 0.6 mM, which is recorded as a second solution. The light yellow suspension solution and the second solution are mixed in a 100 mL beaker, 24 mL of N,N-dimethylformamide is added, and stirring is performed at 50 °C for 30 min, and then transferred to a stainless steel autoclave with a Teflon liner, the autoclave is heated to 100 °C for reaction for 16 h, filtered, washed with ethanol and N,N-dimethylformamide, and vacuum dried at 80 °C for 12 h to obtain light yellow hydrated basic copper vanadate microspheres, which are recorded as CuVOH-1.

[0044] S2, 5 mg of CuVOH-1 and 5 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent, and ultrasonic treatment was performed for 30 min to obtain a uniform CuVOH-1 microsphere suspension, which was recorded as CuVOH-1 suspension. A glassy carbon electrode with a diameter of 3 mm was polished into a mirror surface using a polishing cloth and 0.3 μm alumina paste. The CuVOH-1 suspension was drop-coated on the surface of the glassy carbon electrode, and then evaporated at room temperature, naturally dried, and then sequentially cleaned with ethanol and deionized water. 10 μL of CuVOH-1 suspension was coated on the surface of the glassy carbon electrode to obtain a CuVOH-1 microsphere modified electrode, which was recorded as CuVOH-1 / GCE.

[0045] Example 2 A preparation method of a CuVOH-2 microsphere modified electrode, comprising the following steps: S1, 0.1 mol, i.e. 13 g of NaVO3 was dissolved in 120 mL of deionized water, and the pH was adjusted to 6, which was recorded as a first solution for standby. 0.6 mmol, i.e. 0.104 g of CuCl2·2H2O was dissolved in 24 mL of deionized water, and 0.8 mL of the first solution was added to obtain a light yellow suspension solution. Benzoic acid was dissolved in 24 mL of ethanol to obtain a benzoic acid solution with a concentration of 0.5 mM, which was recorded as a second solution. The light yellow suspension solution and the second solution were mixed in a 100 mL beaker, 24 mL of N,N-dimethylformamide was added, and stirring was performed at 50°C for 30 min. Then, the mixture was transferred to a stainless steel autoclave with a teflon liner, and the autoclave was heated to 100°C for 16 h. Filtration was performed, and the product was washed with ethanol and N,N-dimethylformamide, and then vacuum dried at 80°C for 12 h to obtain light yellow CuVOH-2 microspheres.

[0046] S2, 5 mg of CuVOH-2 and 5 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent, and ultrasonic treatment was performed for 30 min to obtain a uniform CuVOH-2 microsphere suspension, which was recorded as CuVOH-2 suspension. A glassy carbon electrode with a diameter of 3 mm was polished into a mirror surface using a polishing cloth and 0.3 μm alumina paste. The CuVOH-2 suspension was drop-coated on the surface of the glassy carbon electrode, and then evaporated at room temperature, naturally dried, and then sequentially cleaned with ethanol and deionized water. 10 μL of CuVOH-2 suspension was coated on the surface of the glassy carbon electrode to obtain a CuVOH-2 microsphere modified electrode, which was recorded as CuVOH-2 / GCE.

[0047] Example 3 A preparation method of a CuVOH-2 microsphere modified electrode, comprising the following steps: S1, 0.1 mol, i.e. 13 g of NaVO3 was dissolved in 120 mL of deionized water, the pH was adjusted to 6, and was recorded as a first solution for standby. 0.6 mmol, i.e. 0.104 g of CuCl2·2H2O was dissolved in 24 mL of deionized water, 0.8 mL of the first solution A was added, and a light yellow suspension solution was obtained. Benzoic acid was dissolved in 24 mL of ethanol to obtain a benzoic acid solution with a concentration of 0.4 mM, which was recorded as a second solution. The light yellow suspension solution and the second solution were mixed in a 100 mL beaker, 24 mL of N,N-dimethylformamide was added, stirred at 50°C for 30 min, then transferred to a teflon-lined stainless steel autoclave, the autoclave was heated to 100°C for 16 h, filtered, washed with ethanol and N,N-dimethylformamide, and vacuum dried at 80°C for 12 h to obtain light yellow copper hydroxide vanadate microspheres, which were recorded as CuVOH-3.

[0048] S2, 5 mg of CuVOH-3 and 5 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent, and ultrasonic treatment was performed for 30 min to obtain a uniform copper hydroxide vanadate microsphere suspension, which was recorded as CuVOH-3 suspension. A glassy carbon electrode with a diameter of 3 mm was polished into a mirror surface using a polishing cloth and 0.3 μm alumina paste, the CuVOH-3 suspension was drop-coated on the surface of the glassy carbon electrode, and was evaporated and naturally dried at room temperature. The glassy carbon electrode was then sequentially washed with ethanol and deionized water, and 10 μL of CuVOH-3 suspension was coated on the surface of the glassy carbon electrode to obtain a copper hydroxide vanadate microsphere modified electrode, which was recorded as CuVOH-3 / GCE.

[0049] Example 4 A method for preparing a copper hydroxide vanadate microsphere modified electrode, comprising the following steps: S1, 0.1 mol, i.e. 13 g of NaVO3 was dissolved in 120 mL of deionized water, the pH was adjusted to 6, and was recorded as a first solution for standby. 0.6 mmol, i.e. 0.104 g of CuCl2·2H2O was dissolved in 24 mL of deionized water, 0.8 mL of the first solution A was added, and a light yellow suspension solution was obtained. Benzoic acid was dissolved in 24 mL of ethanol to obtain a benzoic acid solution with a concentration of 0.4 mM, which was recorded as a second solution. The light yellow suspension solution and the second solution were mixed in a 100 mL beaker, 24 mL of N,N-dimethylformamide was added, stirred at 50°C for 30 min, then transferred to a teflon-lined stainless steel autoclave, the autoclave was heated to 100°C for 16 h, filtered, washed with ethanol and N,N-dimethylformamide, and vacuum dried at 80°C for 12 h to obtain light yellow copper hydroxide vanadate microspheres, which were recorded as CuVOH-3.

[0050] S2, 5 mg of CuVOH-4 and 5 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent, and ultrasonic treatment was performed for 30 min to obtain a uniform CuVOH-4 microsphere suspension, which was recorded as CuVOH-4 suspension. A glassy carbon electrode with a diameter of 3 mm was polished into a mirror surface using a polishing cloth and 0.3 μm alumina paste. The CuVOH-4 suspension was drop-coated on the surface of the glassy carbon electrode, and then evaporated at room temperature, naturally dried, and then sequentially cleaned with ethanol and deionized water. 10 μL of CuVOH-4 suspension was coated on the surface of the glassy carbon electrode to obtain a CuVOH-4 microsphere modified electrode, which was recorded as CuVOH-4 / GCE.

[0051] Example 5 A preparation method of a CuVOH-5 microsphere modified electrode, comprising the following steps: S1, 0.05 mmol of NaVO3 was dissolved in 120 mL of deionized water, and the pH was adjusted to 4, which was recorded as a first solution for standby. 0.1 mmol of CuCl2·2H2O was dissolved in 24 mL of deionized water, 0.8 mL of the first solution was added, and a light yellow suspension solution was obtained. Benzoic acid was dissolved in 24 mL of ethanol to obtain a benzoic acid solution with a concentration of 0.6 mM, which was recorded as a second solution. The light yellow suspension solution and the second solution were mixed in a 100 mL beaker, 24 mL of N,N-dimethylformamide was added, and stirring was performed at 50°C for 30 min. Then, it was transferred to a stainless steel autoclave with a Teflon liner, and the autoclave was heated to 80°C for reaction for 24 h. Filtration was performed, and washing was performed with ethanol and N,N-dimethylformamide. Vacuum drying was performed at 80°C for 12 h to obtain light yellow CuVOH-5 microspheres, which were recorded as CuVOH-5.

[0052] S2, 5 mg of CuVOH-5 and 4 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent, and ultrasonic treatment was performed for 30 min to obtain a uniform CuVOH-5 microsphere suspension, which was recorded as CuVOH-5 suspension. A glassy carbon electrode with a diameter of 3 mm was polished into a mirror surface using a polishing cloth and 0.3 μm alumina paste. The CuVOH-5 suspension was drop-coated on the surface of the glassy carbon electrode, and then evaporated at room temperature, naturally dried, and then sequentially cleaned with ethanol and deionized water. 10 μL of CuVOH-5 suspension was coated on the surface of the glassy carbon electrode to obtain a CuVOH-5 microsphere modified electrode, which was recorded as CuVOH-5 / GCE.

[0053] Example 6 A preparation method of a CuVOH-5 microsphere modified electrode, comprising the following steps: S1, 0.3 mol of NaVO3 was dissolved in 120 mL of deionized water, the pH was adjusted to 7, and was recorded as a first solution for standby. 1.0 mmol of CuCl2·2H2O was dissolved in 24 mL of deionized water, 0.8 mL of the first solution was added, and a light yellow suspension solution was obtained. Benzoic acid was dissolved in 24 mL of ethanol to obtain a benzoic acid solution with a concentration of 0.6 mM, which was recorded as a second solution. The light yellow suspension solution and the second solution were mixed in a 100 mL beaker, 24 mL of N,N-dimethylformamide was added, stirred at 50℃ for 30 min, then transferred to a stainless steel autoclave with a teflon liner, the autoclave was heated to 120℃ for 12 h, filtered, washed with ethanol and N,N-dimethylformamide, and vacuum dried at 80℃ for 12 h to obtain light yellow copper hydroxide vanadate microspheres, which were recorded as CuVOH-6.

[0054] S2, 5 mg of CuVOH-6 and 6 μL of 5% Nafion solution were dispersed in 1 mL of ethanol solvent and ultrasonicated for 30 min to obtain a uniform copper hydroxide vanadate microsphere suspension, which was recorded as CuVOH-6 suspension. A glassy carbon electrode with a diameter of 3 mm was polished into a mirror surface with a polishing cloth and 0.3 μm alumina paste, the CuVOH-6 suspension was drop-coated on the surface of the glassy carbon electrode, evaporated at room temperature, naturally dried, and then sequentially washed with ethanol and deionized water to coat 10 μL of CuVOH-6 suspension on the surface of the glassy carbon electrode to obtain a copper hydroxide vanadate microsphere modified electrode, which was recorded as CuVOH-6 / GCE.

[0055] In order to further illustrate the technical effects of the present application, the present application also provides a comparative example, as follows: Comparative Example 1 Compared with Example 1, the difference lies in that only the bare electrode of the glassy carbon electrode is used without any modification.

[0056] The morphology of the copper hydroxide vanadate microspheres of the present application, the copper hydroxide vanadate microsphere modified electrode and the bare electrode of Comparative Example 1 were characterized, and the above electrodes were used for the detection of ascorbic acid to compare and characterize the performance. Since the performance of Examples 1-6 is similar, the effects of Examples 1-4 are taken as examples for effect description, and the characterization results are as follows.

[0057] 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-CuVOH-4 prepared by adding benzoic acid with a concentration of 0.3 mM-0.6 mM as a particle size modulator, i.e. the XRD patterns of the copper hydroxide vanadate microsphere modified electrodes prepared in Examples 1-4 of the present application, are as follows. Figure 1It can be seen that all diffraction peaks are consistent with the monoclinic Cu3V2O7(OH)2·2H2O phase with a space group of C2 / m, JCPDs No. 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 (001) plane, (200) plane, (110) plane, (111) plane, (002) plane, (310) plane and (020) plane respectively. The crystal structure diffraction peaks prove that the product is Cu3V2O7(OH)2·2H2O, and the crystallinity is good.

[0058] Figure 2 The SEM images of the copper hydroxide vanadate microspheres prepared in Example 1 to Example 4 of the present application are shown in the figure, wherein A is Example 4, B is Example 3, C is Example 2, and D is 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. With the increase of the concentration of benzoic acid, the sample size gradually increases. When 0.3mM benzoic acid is added, the size of CuVOH-4 in Example 4 is about 400nm, and when 0.6mM benzoic acid is added, the size of CuVOH-1 in Example 1 is about 2.5μm.

[0059] Electrochemical detection: In 0.1M KCl background electrolyte, the response of copper hydroxide vanadate microsphere modified electrode in detecting different concentrations of ascorbic acid was tested by CV method, the scanning rate was 50mV / s, and the test potential range was-1.0V~+1.0V. Two oxidation-reduction peaks cvp1 and cvp2 were used to analyze the concentration of ascorbic acid, which had strong selectivity, sensitivity and stability.

[0060] Figure 3 The CVs graphs of the copper hydroxide vanadate microsphere modified electrode prepared in Example 1 of the present application and the bare electrode of Comparative Example 1 are shown in the figure. Figure 3 It can be seen that there is a significant difference in electrochemical response between CuVOH-1 modified glassy carbon electrode, i.e. CuVOH-1 / GCE and bare electrode. CuVOH-1 / GCE shows two pairs of obvious oxidation-reduction peaks in the cyclic voltammetry curve, while the bare electrode has no obvious current response peak, indicating that the latter has no electrocatalytic activity for ascorbic acid.

[0061] Figure 4 The CVs graphs of the copper hydroxide vanadate microsphere modified electrode prepared in Example 1 to Example 4 of the present application are shown in the figure. Figure 4It can be seen that the CuVOH microspheres with different particle sizes have obvious differences in the current response of the electrode, and the CuVOH-1 modified electrode shows the strongest redox peak current, indicating that it has higher electrocatalytic activity and current response to ascorbic acid. The anodic peak potentials are 0.062 V and 0.218 V, respectively, and the cathodic peak potentials are-0.067 V and-0.315 V, respectively, showing good electrochemical reversibility and interface activity, indicating that CuVOH-1 has better electron transmission capacity. The two anodic peak potentials of examples 2-4 are between 0.048 V and 0.062 V and between 0.178 V and 0.218 V, respectively, and the two cathodic peak potentials of examples 2-4 are between-0.372 V and-0.286 V and between-0.102 V and-0.011 V, respectively.

[0062] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A method for preparing a hydrated basic copper vanadate microsphere-modified electrode, characterized in that, 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 is used as raw material, mixed to obtain a suspension, benzoic acid is used as particle size control agent, and ethanol and N,N-dimethylformamide are used as mixed solvents, mixed evenly, and then subjected to a solvothermal reaction at 80℃~120℃ to obtain hydrated basic copper vanadate microspheres. 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.

2. The method for preparing the hydrated basic copper vanadate microsphere modified electrode according to claim 1, characterized in that, 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.

3. The method for preparing the hydrated basic copper vanadate microsphere modified electrode according to claim 2, characterized in that, The hydrated basic copper vanadate microspheres have a particle size of 0.1 μm to 3.0 μm.

4. The method for preparing the hydrated basic copper vanadate microsphere modified electrode according to claim 1, characterized in that, The mass percentage of the hydrated basic copper vanadate microspheres modified with the electrode is 0.001%~0.02%.

5. The method for preparing the hydrated basic copper vanadate microsphere modified electrode according to claim 1, characterized in that, The bare electrode is a glassy carbon electrode, a gold electrode, a carbon paste electrode, or FTO conductive glass.

6. The method for preparing the hydrated basic copper vanadate microsphere modified electrode according to claim 1, characterized in that, 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.

7. The method for preparing the hydrated basic copper vanadate microsphere modified electrode according to claim 1, 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.

8. A hydrated basic copper vanadate microsphere-modified electrode, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the hydrated basic copper vanadate microsphere modified electrode according to claim 8 in ascorbic acid detection.

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