Preparation method and application of all-solid-state ion selective microelectrode

Abstract

The invention discloses a preparation method and application of an all-solid-state ion selective microelectrode, and belongs to the field of ion selective electrodes. A composite material with the mass ratio of super-hydrophobic carbon nanotubes to CoWSe2 being 3: 1 is used as an ion-electron transduction layer material for constructing the all-solid-state ion selective microelectrode, and a nitrate ion selective polymer film or a hydrogen ion selective polymer film is respectively dispensed on the surface of the transduction layer; and drying to obtain the all-solid-state nitrate ion selective microelectrode or all-solid-state hydrogen ion selective microelectrode. According to the method disclosed by the invention, the all-solid-state ion selective microelectrode can more effectively inhibit the formation of a water layer, so that the microelectrode has better potential stability and longer service life when being applied to the detection of ions in an environmental water body sample.

Description

Technical Field

[0001] The present invention belongs to the field of ion-selective electrodes and relates to a preparation method of an all-solid-state ion-selective microelectrode. The all-solid-state ion-selective microelectrode is mainly used for ion detection in the fields of plants, environment, life sciences, etc. Background Art

[0002] As a cutting-edge analysis technology in electrochemical sensors, the all-solid-state ion-selective microelectrode technology has been widely used in the fields of biology, brain science, plants, and environmental science due to its advantages such as high sensitivity, small size, and fast mass transfer rate. In the field of plant physiology, Professor Woo Hyoung Lee of the University of Florida in the United States proposed an all-solid-state zinc ion-selective microelectrode based on polythiophene (POT) in 2018, realizing the detection of zinc ion flux in the rhizosphere and leaf microzones of citrus plants ( MRS Communications , 2018, 8 , 404-410), which confirmed the possibility of using the all-solid-state ion-selective microelectrode to replace the traditional liquid membrane microelectrode for detecting ion flux in the plant rhizosphere.

[0003] As the existing all-solid-state ion-selective microelectrode, there are still some key scientific problems: when it is used for long-term monitoring of microzones in a humid environment, water molecules in the environment easily enter the interface between the ion-selective membrane and the ion-electron transduction layer through the ion-selective membrane, thus forming a water layer, which affects the potential stability, osmotic pressure, and mechanical properties of the electrode. The formation of the water layer will affect various properties of the electrode. If the generation of the water layer cannot be effectively inhibited, the electrode will eventually lose its detection performance.

[0004] The Chinese invention patent with the authorization announcement number CN117825472B discloses a "nitrate ion detection method for an all-solid-state nitrate ion-selective electrode based on cobalt-tungsten bimetallic selenide", which solves the improvement of the potential stability of the all-solid-state ion-selective electrode to a certain extent. However, it still has problems such as large electrode size and the existence of a water layer between the ion-selective membrane and the ion-electron transduction layer. These problems will bring a series of adverse effects. For example, it is difficult to be used for detecting ions in a microzone environment; for another example, when detecting in a humid environment for a long time, a water layer is easily formed, resulting in reduced stability and shortened service life of the electrode.

[0005] The ion-electron transduction layer material is located between the ion-selective membrane and the conductive substrate, and its surface hydrophobicity determines the ease of formation of the water layer. This means that the key to constructing a highly moisture-resistant all-solid-state ion-selective electrode is to use a (super) highly hydrophobic ion-electron transduction layer material. According to the surface wettability theory, the superhydrophobicity of the material (contact angle greater than 150 oIt mainly depends on the magnitude of its surface energy and surface roughness. From the perspective of reducing the surface energy of materials, fluorinated organic compounds are usually used to modify the surface of ion-electron transduction layer materials (conductive polymers or Ti3C2Tx-MXene). The introduction of these hydrophobic branches effectively improves the hydrophobicity of the above two types of materials, thereby significantly suppressing the interference of the water layer and improving the performance of all-solid-state ion-selective electrodes. However, the long-term use of fluorine-containing substances will cause serious harm to human and environmental health, restricting the use of such substances from the perspective of ecological environmental protection. In addition, some scholars have prepared various micro-nano structured NiCo2S4 materials from the perspective of changing the surface roughness of materials. Among them, ordered nano-sheet NiCo2S4 shows high hydrophobicity when used as an ion-electron transduction layer material, effectively suppressing the formation of the water layer, improving the stability and service life of the electrode. Its main disadvantage is that this type of electrode is a conventional ion-selective electrode with a relatively large size (3000 μm), making it difficult to achieve micro-area detection. Different from the thickness of the polymer ion-selective membrane (about 150 μm - 200 μm) used in conventional all-solid-state ion-selective electrodes, the polymer ion-selective membrane used in microelectrodes is thinner (not exceeding 60 μm), making it easier to form a water layer between the polymer ion-selective membrane and the transduction layer material, affecting the performance of the microelectrode. Therefore, the development of superhydrophobic ion-electron transduction layer materials is more important for constructing highly moisture-resistant all-solid-state ion-selective microelectrodes. However, there are few reports on the use of superhydrophobic nanomaterials to construct highly moisture-resistant all-solid-state ion-selective microelectrodes. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method and application of an all-solid-state ion-selective microelectrode, so that the all-solid-state ion-selective microelectrode can more effectively suppress the formation of the water layer, thereby enabling the microelectrode to have better potential stability and longer service life when applied to the detection of ions in environmental water samples.

[0007] The present invention adopts the following technical solutions: A preparation method of an all-solid-state ion-selective microelectrode, comprising the following steps: using a composite material with a mass ratio of superhydrophobic carbon nanotubes to CoWSe2 of 3:1 as the ion-electron transduction layer material for constructing the all-solid-state ion-selective microelectrode, and respectively drop-coating a nitrate ion-selective polymer membrane or a hydrogen ion-selective polymer membrane on the surface of the transduction layer, and drying to obtain an all-solid-state nitrate ion-selective microelectrode or an all-solid-state hydrogen ion-selective microelectrode.

[0008] Preferably, the superhydrophobic carbon nanotubes are prepared by the following method: mixing hydroxylated carbon nanotubes with methyltrichlorosilane to obtain a mixed solution; centrifuging the mixed solution to obtain superhydrophobic carbon nanotubes.

[0009] Further preferably, the dosage ratio between the hydroxylated carbon nanotubes and methyltrichlorosilane is (5 mg to 15 mg):(1 to 3 mL); the reaction time of the two is 3 to 6 h.

[0010] Preferably, the CoWSe2 is prepared according to the following steps: (1) Weigh Na2WO4·2H2O, Co(NO3)2·6H2O and urea, and dissolve them together in a mixed solution of ultrapure water and ethanol, and ultrasonically dissolve until completely dissolved; (2) React the completely dissolved solution at 150 to 200 °C for 6 to 12 h; (3) Cool, centrifuge and wash to obtain a cobalt-tungsten bimetallic intermediate in the form of a precipitate; (4) Disperse the cobalt-tungsten bimetallic intermediate and selenium powder in a mixed solution of hydrazine hydrate and ethanol, and continue to react at 120 to 180 °C for 12 to 14 h; (5) Cool, centrifuge and wash, and dry to obtain the product CoWSe2; Wherein, the mass ratio of the Na2WO4·2H2O, Co(NO3)2·6H2O, urea and selenium powder is (0.01 to 0.1):(0.01 to 0.1):(0.1 to 1):(0.02 to 0.2).

[0011] Preferably, the nitrate ion selective polymer membrane is prepared according to the following method: Dissolve the proportionally weighed polyvinyl chloride, tetra(4-chlorophenyl)boric acid tetradodecylammonium, nitrate ion carrier and dioctyl sebacate in tetrahydrofuran, and stir evenly to obtain the nitrate ion selective polymer membrane.

[0012] Further preferably, the nitrate ion carrier is dodecylmethylammonium nitrate; the dosage ratio of the polyvinyl chloride, tetra(4-chlorophenyl)boric acid tetradodecylammonium, dodecylmethylammonium nitrate and dioctyl sebacate is: 32.7:1:1:65.3; the ratio of the total mass of the above substances to the volume of tetrahydrofuran is 100 mg:1 mL.

[0013] Preferably, the hydrogen ion selective polymer membrane is prepared according to the following method: Dissolve the proportionally weighed H + Carrier I, sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate, polyvinyl chloride and o-nitrophenyloctyl ether in tetrahydrofuran, and stir evenly to obtain the hydrogen ion selective polymer membrane.

[0014] Further preferably, the H +The carrier I is tri-n-dodecylamine; the dosage ratio of the tri-n-dodecylamine, sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate, polyvinyl chloride, and o-nitrophenyloctyl ether is: 1.4:0.6:33.5:64.5; the ratio of the total mass of the substances in the above ratio to the volume of tetrahydrofuran is 100 mg:1 mL.

[0015] Application of the all-solid-state ion-selective microelectrode prepared by the method for preparing an all-solid-state ion-selective microelectrode in ion detection in water samples.

[0016] Preferably, an Ag / AgCl electrode is used as the reference electrode, and the activated all-solid-state ion-selective microelectrode is used as the indicator electrode to test the content of H + or NO3 - in environmental samples, biological samples or the plant field.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses three silanization reagents (methyltrichlorosilane, dimethyldichlorosilane, and trimethylchlorosilane) to hydrophobically treat hydroxylated carbon nanotubes. By testing the contact angles of carbon nanotubes treated with different silanization reagents, the results show that the carbon nanotubes treated with methyltrichlorosilane exhibit the largest contact angle and have the characteristics of superhydrophobicity. Then, the carbon nanotubes treated with methyltrichlorosilane are combined with a high redox capacitance material (CoWSe2) to prepare a material with strong hydrophobicity and high capacitance value, which is used as the ion-electron transduction material of the all-solid-state ion-selective microelectrode to solve the problem of forming a water layer between the polymer ion-selective membrane and the transduction layer material. Thus, an all-solid-state ion-selective microelectrode with high stability, strong hydrophobicity, high selectivity, and strong anti-interference ability is further constructed. The invention can provide a new detection technology for the plant field, environmental field, and life science field.

[0018] The present invention takes the superhydrophobic carbon material as one kind of composite material, which can provide a large specific surface area and superhydrophobicity, and can effectively inhibit the formation of a water layer. Taking a high redox capacitance material (CoWSe2) as another kind of composite material, it has a large theoretical specific capacitance and can effectively improve the stability of the microelectrode. The all-solid-state ion-selective microelectrode constructed by the present invention can be used for rapid and sensitive detection of ions in the fields of plants, environment, and life science. Description of the Drawings

[0019] Figure 1 It is a comparative diagram of the hydrophobicity characterization of nanotube materials modified with different solvents in the first step of Example 1 of the present invention. Among them, A corresponds to trimethylchlorosilane, B corresponds to dimethyldichlorosilane, and C corresponds to methyltrichlorosilane.

[0020] Figure 2Cyclic voltammetry curves for performance test and comparison of different modified solvent transduction layers in Example 2 of the present invention.

[0021] Figure 3 Chronopotentiometry curves (A) and capacitance values (B) of different composite material ratios provided in Example 3 of the present invention.

[0022] Figure 4 Contact angle test diagram when the mass ratio of superhydrophobic carbon nanotube / CoWSe2 composite material is 3:1 provided in Example 4 of the present invention.

[0023] Figure 5 Real-time potential change response diagrams (A) and calibration curves (B) of all-solid-state nitrate (solid line) / hydrogen ion selective (dashed line) microelectrodes provided in Example 8 and Example 9 of the present invention.

[0024] Figure 6 Water layer test comparison diagram of an all-solid-state nitrate ion selective microelectrode taking Example 10 of the present invention as an example and a blank electrode. The dashed line in the figure corresponds to the all-solid-state nitrate ion selective microelectrode added with the composite material of the present invention, and the solid line corresponds to the blank electrode. Detailed implementation manners

[0025] The present invention will be further described below in conjunction with examples and experimental data. It should be noted that the specific implementation manners described herein are only for explaining and interpreting the present invention, and are not used to limit the protection scope of the present invention.

[0026] Example 1. Hydrophobic treatment of hydroxylated carbon nanotubes and hydrophobicity test.

[0027] First step: Preparation of superhydrophobic carbon nanotubes: Weigh three portions of hydroxylated carbon nanotubes, each 15 mg, measure 3 mL of trimethylchlorosilane, dichlorodimethylsilane, and methyltrichlorosilane respectively. Mix the three portions of hydroxylated carbon nanotubes with these three solvents respectively and stir for 4 h to obtain three mixed solutions; Centrifuge the three mixed solutions, all set the parameters to 6000 r / min and 3 min to obtain three kinds of superhydrophobic carbon nanotubes.

[0028] Observe the three kinds of superhydrophobic carbon nanotube materials prepared in this step under a contact angle meter to obtain Figure 1 the contact angle test pictures shown. As Figure 1 can be seen, the contact angle of the carbon nanotube material treated with methyltrichlorosilane synthesized is greater than 150° ( Figure 1 C in), showing superhydrophobicity. The carbon nanotube materials synthesized under the other two solvent conditions only show hydrophobicity (see Figure 1 A and B in).

[0029] Example 2. Performance test and comparison of different modification solvents.

[0030] Take 5 mg of each of the three superhydrophobic carbon nanotubes obtained in Example 1, and disperse them in 1 mL of methyltrichlorosilane solvent respectively to form three ion-electron transduction layer dispersions. Then, further drop-coat and modify the three ion-electron transduction layer dispersions on the electrode substrates of the microelectrodes respectively, and dry them under an infrared lamp to obtain three uniform and dense transduction layers, and test their performance by cyclic voltammetry. Specifically: Place the electrode in 10 -1 M KCl electrolyte solution, and perform cyclic voltammetry tests using a three-electrode system. The parameters are as follows: the potential window is -0.8 - 0.65 V, and the scanning rate is 100 mV s -1 , and obtain the cyclic voltammogram shown in Figure 2.

[0031] From Figure 2 it can be seen that the carbon nanotubes modified with methyltrichlorosilane have a greater current response and are more conducive to improving the electrode stability, indicating that the best modification solvent is methyltrichlorosilane.

[0032] Example 3: Preparation of a composite material of an ion-electron transduction layer material for an all-solid-state ion-selective electrode and optimization of the mass ratio of superhydrophobic carbon nanotubes to CoWSe2.

[0033] The first step: Preparation of CoWSe2: First, weigh 3.2985 g of Na2WO4·2H2O, 2.9107 g of Co(NO3)2·6H2O, and 6.006 g of urea, and dissolve them in 80 mL of a mixed solution of ultrapure water and ethanol with a volume ratio of 1:1 by ultrasonic until completely dissolved. Then, transfer the above solution to a polytetrafluoroethylene reaction kettle, and react at 150 °C for 12 h; after the reaction, let the reaction kettle cool naturally to room temperature, and centrifuge and wash it three times with water and twice with ethanol respectively to obtain a cobalt-tungsten bimetallic intermediate in the form of a precipitate. Finally, disperse all the obtained cobalt-tungsten bimetallic intermediate and 1.5792 g of selenium powder in 50 mL of a mixed solution of hydrazine hydrate and ethanol with a volume ratio of 1:1, and continue to react at 150 °C for 12 h; after the reaction, let the reaction kettle cool naturally to room temperature, and centrifuge and wash it three times with water and twice with ethanol respectively, and dry it in a vacuum drying oven at 60 °C for 12 h to obtain the product CoWSe2.

[0034] The second step: Preparation of the composite material: According to the mass ratios of superhydrophobic carbon nanotubes to CoWSe2 being 4:1, 3:1, 2:1, 1:1, and 1:2 respectively, weigh the superhydrophobic carbon nanotubes prepared by treating with methyltrichlorosilane in the first step of Example 1 and CoWSe2 prepared in the first step of this example, and grind them in a mortar respectively to obtain five different mass ratios and use them as composite materials for the ion-electron transduction layer materials of the all-solid-state ion-selective electrode.

[0035] Weigh 5 mg of each of the above six composite materials and disperse them separately in 1 mL of methyltrichlorosilane solvent. Sonicate them to form five uniform dispersions. Then, further drop-coat and modify the five dispersions on the electrode substrate of the microelectrode and dry them under an infrared lamp to obtain five uniform and dense transduction layers. Optimize the composite ratio by chronopotentiometry. Specifically: apply a current of + 1 nA for a time of + 60 s. The results are shown in Figure 3 .

[0036] As can be seen from Figure 3 A and B, the microelectrode substrate of the superhydrophobic carbon nanotube / high redox type composite material with a dropping ratio of 3:1 has a smaller potential drift. According to the formula ΔE / Δt = I / C (where ΔE / Δt is the potential drift, I is the applied current, and C is the capacitance), the composite material with a dropping ratio of 3:1 exhibits the largest capacitance value, indicating that the optimal dropping ratio of the composite material is 3:1.

[0037] Example 4. Hydrophobicity verification example.

[0038] Based on the composite material obtained in Example 3 with a superhydrophobic carbon nanotube / CoWSe2 composite ratio of 3:1, further test its contact angle to characterize its hydrophobicity. The results are shown in Figure 4 .

[0039] As can be seen from Figure 4 , when the ratio of the superhydrophobic carbon nanotube / CoWSe2 composite material is 3:1, its contact angle is 153°, still having superhydrophobicity.

[0040] Example 5. Preparation example of nitrate ion selective polymer membrane.

[0041] Weigh 32.70 wt% PVC (polyvinyl chloride), 1.00 wt% ETH500 [tetrakis(4-chlorophenyl)borate tetradodecylammonium], 1.00 wt% nitrate ion carrier (dodecylmethylammonium nitrate), and 65.30 wt% DOS (dioctyl sebacate). Dissolve 150 mg of the substances in the above ratio in 1.5 mL of tetrahydrofuran and stir evenly to obtain a nitrate ion selective polymer membrane.

[0042] Example 6. Preparation example of hydrogen ion selective polymer membrane.

[0043] Weigh 1.4 wt% H +Carrier I {tri-n-dodecylamine, [CH3(CH2)11]3N}, 0.6 wt% NaTFPB [sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate], 33.5 wt% PVC (polyvinyl chloride), and 64.5 wt% O-NPOE (o-nitrophenyloctyl ether). 360 mg of substances in the above proportions were dissolved in 3.6 mL of tetrahydrofuran and stirred evenly to obtain a hydrogen ion-selective polymer membrane.

[0044] Example 7. Preparation example of a microelectrode.

[0045] The composite material obtained in Example 3 with a mass ratio of superhydrophobic carbon nanotubes to CoWSe2 of 3:1 was used as the ion-electron transduction layer material for constructing a all-solid-state ion-selective microelectrode. The nitrate ion-selective polymer membrane and the hydrogen ion-selective polymer membrane prepared in Example 5 and Example 6 were respectively drop-coated on the surface of the transduction layer and dried in a constant temperature and humidity chamber for 12 h to obtain an all-solid-state nitrate ion-selective microelectrode and an all-solid-state hydrogen ion-selective microelectrode.

[0046] Example 8. Example of applying an all-solid-state nitrate ion-selective microelectrode based on a superhydrophobic carbon nanotubes / CoWSe2 composite material to nitrate ions.

[0047] The all-solid-state nitrate ion-selective microelectrode obtained in Example 7 was activated in a 10 -3 M potassium nitrate aqueous solution for 2 h. The activated microelectrode was used to detect nitrate ions in the solution. Specifically, an electrochemical workstation was used to measure the potential response of the microelectrode, with an Ag / AgCl electrode as the reference electrode and the activated microelectrode as the indicator electrode. The open-circuit potential of the electrode was tested in nitrate ion solutions with different concentrations under a water background, and the corresponding potential-time curve and calibration (logarithm of activity vs. potential) curve were plotted to obtain Figure 5 A.

[0048] As can be seen from the solid line of A in Figure 5 the all-solid-state ion-selective microelectrode based on the superhydrophobic carbon nanotubes / CoWSe2 composite material exhibits a rapid and stable potential response.

[0049] First, the all-solid-state nitrate ion-selective microelectrode was tested in 10 -1 M, 10 -2 M, 10 -3 M, 10 -4 M, 10 -5 M, 10 -6 M, 10 -7 M, and 10 -8The open-circuit potential of the nitrate concentration was measured, and its potential-time curve was recorded. Then, the concentrations of different aqueous potassium nitrate solutions were corrected to activities, and a calibration curve was plotted. Finally, the nitrate ion concentration was calculated according to the Nernst equation. As can be seen from Figure 5 It can be seen that the electrode shows a linear Nernst response in an aqueous solution with a potassium nitrate concentration of 10 -1 - 10 -8 mol L-1, with a response slope of -57.72 ± 0.6 mV / dec (R 2 = 0.995, n = 5), and a detection limit of 1×10 -6 M.

[0050] The results show that the detection limit of the microelectrode prepared in this invention can meet the detection of nitrate ions in actual samples.

[0051] Example 9: Application example of a all-solid-state hydrogen ion selective microelectrode based on a superhydrophobic carbon nanotube / CoWSe2 composite material for hydrogen ion detection.

[0052] The all-solid-state hydrogen ion selective microelectrode obtained in Example 7 was activated in a 10 -2 M sulfuric acid aqueous solution for 2 h, and the pH of the solution was detected. Specifically, the potential response of the electrode was measured using an electrochemical workstation, with an Ag / AgCl electrode as the reference electrode and the activated microelectrode as the indicator electrode. The open-circuit potential of the electrode was measured under different pH conditions, and the corresponding potential-time curve and calibration (logarithm of activity vs. potential) curve were plotted.

[0053] As can be seen from Figure 5 B in, the microelectrode shows a stable and rapid potential response in a B-R buffer aqueous solution with pH = 2.87 - 9.91. After calibration, the Nernst response slope of the electrode is -61.4 ± 0.5 mV / dec (R 2 = 0.999, n = 8).

[0054] Example 10: Example of the water layer test of a all-solid-state nitrate ion selective microelectrode based on a superhydrophobic carbon nanotube / CoWSe2 composite material.

[0055] The open-circuit potential method was used to test the water layer of the electrode. The all-solid-state ion selective microelectrode was first placed in a 0.1 M KNO3 solution for 1 h of activation, and then placed in a 0.1 M KNO3 solution and a 0.1 M K2SO4 solution respectively, and tested for 2 h, 2 h and 8 h in sequence. The test results are as shown in Figure 6 shown.

[0056] As can be seen from Figure 6It can be seen that the electrode potential response of the material with the composite ratio of 3:1 of methyltrichlorosilane-modified carbon nanotubes and CoWSe2 is stable. After changing the solution to 0.1 M K2SO4, there is no obvious potential drift in the electrode, indicating that there is no obvious water layer (solid line) generated between the ion-selective membrane and the conductive substrate; the potential response of the microelectrode without adding the composite material of the present invention is unstable, showing an obvious potential shift, indicating that a water layer is generated between the ion-selective membrane and the conductive substrate (dashed line). From the above, it can be concluded that the material with the composite ratio of 3:1 of methyltrichlorosilane-modified carbon nanotubes and CoWSe2 is difficult to generate a water layer and has good stability.

Claims

1. A preparation method of an all-solid-state ion-selective microelectrode, characterized in that It includes the following steps: Using a composite material with a mass ratio of superhydrophobic carbon nanotubes to CoWSe2 of 3:1 as the ion-electron transduction layer material for constructing an all-solid-state ion-selective microelectrode, drop-coating a nitrate ion-selective polymer membrane or a hydrogen ion-selective polymer membrane on the surface of the transduction layer respectively, and drying to obtain an all-solid-state nitrate ion-selective microelectrode or an all-solid-state hydrogen ion-selective microelectrode.

2. The preparation method of the all-solid-state ion-selective microelectrode according to claim 1, wherein: The superhydrophobic carbon nanotubes are prepared by the following method: Mixing hydroxylated carbon nanotubes with methyltrichlorosilane to obtain a mixed solution; centrifuging the mixed solution to obtain superhydrophobic carbon nanotubes.

3. The preparation method of the all-solid-state ion-selective microelectrode according to claim 2, characterized in that: The dosage ratio between hydroxylated carbon nanotubes and methyltrichlorosilane is (5 mg~15 mg):(1~3 mL); the reaction time between the two is 3~6 h.

4. The preparation method of the all-solid-state ion-selective microelectrode according to claim 1, characterized in that: The CoWSe2 is prepared by the following steps: (1) Weigh Na2WO4·2H2O, Co(NO3)2·6H2O and urea, and dissolve them together in a mixed solution of ultrapure water and ethanol, and ultrasonicate until completely dissolved; (2) React the completely dissolved solution at 150~200 °C for 6~12 h; (3) Cool, centrifuge and wash to obtain a cobalt-tungsten bimetallic intermediate in the form of a precipitate; (4) Disperse the cobalt-tungsten bimetallic intermediate and selenium powder in a mixed solution of hydrazine hydrate and ethanol, and continue to react at 120~180 °C for 12~14 h; (5) Cool, centrifuge and wash, and dry to obtain the product CoWSe2; Among them, the mass ratio of Na2WO4·2H2O, Co(NO3)2·6H2O, urea and selenium powder is (0.01~0.1):(0.01~0.1):(0.1~1):(0.02~0.2).

5. The preparation method of the all-solid-state ion-selective microelectrode according to claim 1, characterized in that: The nitrate ion-selective polymer membrane is prepared by the following method: Dissolving proportionally weighed polyvinyl chloride, tetrakis(4-chlorophenyl)boric acid 42-alkylammonium, nitrate ion carrier and dioctyl sebacate in tetrahydrofuran, and stirring evenly to obtain a nitrate ion-selective polymer membrane.

6. The preparation method of the all-solid-state ion-selective microelectrode according to claim 5, characterized in that: The nitrate ion carrier is 32-alkylmethylammonium nitrate; the dosage ratio of polyvinyl chloride, tetrakis(4-chlorophenyl)boric acid 42-alkylammonium, 32-alkylmethylammonium nitrate and dioctyl sebacate is: 32.7:1:1:65.3; The ratio of the total mass of the above substances to the volume of tetrahydrofuran is 100 mg:1 mL.

7. The preparation method of the all-solid-state ion-selective microelectrode according to claim 1, wherein: The hydrogen ion selective polymer membrane is prepared by the following method: Weigh H + carrier I, sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate, polyvinyl chloride and o-nitrophenyloctyl ether are dissolved in tetrahydrofuran, and stirred evenly to obtain the hydrogen ion selective polymer membrane.

8. The preparation method of the all-solid-state ion-selective microelectrode according to claim 7, characterized in that: The said H + The carrier I is tri-n-dodecylamine; the dosage ratio of the tri-n-dodecylamine, sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate, polyvinyl chloride and o-nitrophenyloctyl ether is: 1.4:0.6:33.5:64.5; the ratio of the total mass of the substances in the above ratio to the volume of tetrahydrofuran is 100 mg:1 mL.

9. Application of the all-solid-state ion-selective microelectrode prepared by the preparation method of the all-solid-state ion-selective microelectrode according to any one of claims 1 to 8 in ion detection of water samples.

10. The application according to claim 9, wherein: Using an Ag / AgCl electrode as the reference electrode and an activated all-solid-state ion-selective microelectrode as the indicator electrode, the content of H + or NO3 - in environmental samples, biological samples or the plant field is measured.

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