An electrochemical sensor for detecting lead ions and a preparation method and application thereof

Abstract

The application discloses an electrochemical sensor and a preparation method and application thereof. The electrochemical sensor comprises a three-electrode system composed of a working electrode, a reference electrode and a counter electrode, wherein the working electrode is composed of a base electrode, a molybdenum disulfide nanoparticle modification layer and a polyethylene dioxythiophene layer; the molybdenum disulfide nanoparticles are loaded on the surface of the base electrode through a drop coating method, and the polyethylene dioxythiophene is in-situ loaded on the surface of the molybdenum disulfide nanoparticle modification layer through an electro-polymerization reaction. The electrochemical sensor can be used for detecting lead ions in water bodies, has the advantages of simple preparation, stable performance, suitability for an acidic medium and the like, and is suitable for practical application and popularization.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical sensor technology, and relates to an electrochemical sensor, its preparation method and application, specifically an electrochemical sensor for detecting lead ions, its preparation method and application. Background Technology

[0002] Excessive levels of heavy metals in soil and water bodies pose a serious threat to ecological and food security within watersheds, becoming a key challenge in water environment management. Lead (Pb) and its compounds are particularly problematic. These heavy metal pollutants are not only highly biodegradable... Heavy metals are phytotoxic and non-biodegradable. In aquatic environments, the coexistence of multiple heavy metal ions, coupled with complex pollution from water matrix and organic matter-heavy metals, poses a significant challenge to the accuracy of traditional detection methods. Therefore, effective control and remediation of Pb in aquatic environments is crucial. 2+ Pollution must be addressed urgently, and accurate detection of its content is the foundation of pollution prevention and control.

[0003] Traditional heavy metal detection methods, such as spectrophotometry, inductively coupled plasma mass spectrometry, atomic absorption spectrometry, and atomic fluorescence spectrometry, suffer from problems such as large equipment size, high operating costs, and complex sample pretreatment. Moreover, most of them can only perform total quantity detection. However, current methods often lack the capability for individual analysis and real-time online detection of specific heavy metals. Therefore, utilizing highly sensitive and specific sensing technologies for heavy metal analysis has become a research hotspot. These technologies offer miniaturized equipment that is easy to operate and can detect trace elements in aquatic environments. Rapid, efficient, real-time, online detection of heavy metals.

[0004] Stripping voltammetry is a commonly used electrochemical detection technique suitable for lead ion detection. However, existing sensors suffer from drawbacks such as low specific surface area, few active sites, narrow detection range, and insufficient sensitivity and accuracy. For example, surfaces that have not been stripped... Modified carbon electrodes, when used as working electrodes, cannot detect trace / ultra-heavy heavy metals. While carbon electrodes are inexpensive, reusable, and interface-friendly, making them widely used in constructing various sensors, their direct application in square-wave anodic stripping voltammetry for the detection of trace heavy metals presents challenges. The sensitivity needs to be improved.

[0005] Therefore, developing a low-cost, fast-response, highly sensitive, highly accurate, low-detection-limit, wide-range, highly interference-resistant, and reusable electrochemical sensor is crucial for detecting Pb in water. 2+ Effective detection and removal are of great significance. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a low-cost, fast-responding, high-sensitivity and high-precision detection method for lead detection, with a low detection limit, wide detection range, strong anti-interference ability, and good reusability. The paper also provides an electrochemical sensor for detecting lead ions, which is simple to prepare, easy to operate, and inexpensive, and its application in the detection of lead ions.

[0007] The inventive concept of this invention is as follows: Taking a glassy carbon electrode (GCE) as an example, this invention first designs a three-electrode system using a glassy carbon electrode as the base electrode, and then modifies the glassy carbon electrode with a dispersion containing molybdenum disulfide nanoparticles to obtain a preliminary molybdenum disulfide nanoparticle-modified glassy carbon electrode (i.e., molybdenum disulfide / glassy carbon electrode); then, the molybdenum disulfide / glassy carbon electrode is placed in an electrolyte containing ethylenedioxythiophene and further reacted through scanning treatment to obtain a polyethylenedioxythiophene-modified molybdenum disulfide / glassy carbon electrode (i.e., polyethylenedioxythiophene / molybdenum disulfide / glassy carbon electrode); then, a three-electrode system (including a working electrode, a counter electrode, and a reference electrode) is constructed using the polyethylenedioxythiophene / molybdenum disulfide / glassy carbon electrode to construct a working curve for testing the content of lead ions, thereby obtaining an electrochemical sensor that can be used for quantitative analysis with low detection limits and high accuracy.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an electrochemical sensor comprising: a three-electrode system consisting of a working electrode, a reference electrode, and a counter electrode; wherein the working electrode comprises a substrate electrode, a molybdenum disulfide nanoparticle modification layer, and a polyethylene dioxythiophene layer arranged sequentially.

[0009] Preferably, the substrate electrode is selected from one of glassy carbon electrode, metal oxide electrode, and metal electrode.

[0010] More preferably, the substrate electrode is a glassy carbon electrode.

[0011] Preferably, the reference electrode is one of a calomel electrode, an Ag / AgCl electrode, a mercurous sulfate electrode, or a mercuric oxide electrode.

[0012] More preferably, the reference electrode is an Ag / AgCl electrode.

[0013] Preferably, the counter electrode is one of a platinum electrode and a titanium electrode.

[0014] More preferably, the counter electrode is a platinum electrode.

[0015] Preferably, the platinum electrode is a platinum wire electrode.

[0016] Preferably, the molybdenum disulfide nanoparticles in the molybdenum disulfide nanoparticle modification layer are prepared by high-temperature sintering.

[0017] More preferably, the molybdenum disulfide nanoparticles in the molybdenum disulfide nanoparticle modification layer are prepared by the following method: accurately weigh 3.04 g of thiourea and 1.4 g of ammonium molybdate hydrate into a beaker, add 40 ml of distilled water and stir to dissolve, transfer to a reaction vessel, react at 180 °C for 10 hours, centrifuge and wash three times, and dry in an oven to obtain molybdenum disulfide.

[0018] Preferably, the drying is carried out at 60 °C for 12 hours.

[0019] In a second aspect, the present invention provides a method for preparing the electrochemical sensor described in the first aspect, comprising the following steps: The substrate electrode is sequentially modified with a molybdenum disulfide nanoparticle layer and a polyethylene dioxythiophene layer to obtain a polyethylene dioxythiophene / molybdenum disulfide / working electrode.

[0020] Preferably, the method for preparing the electrochemical sensor includes the following steps: (1) A molybdenum disulfide nanoparticle dispersion was coated on the surface of the substrate electrode and dried to form a molybdenum disulfide nanoparticle modification layer on the surface of the substrate electrode. (2) The substrate electrode modified with molybdenum disulfide nanoparticles obtained in step (1) is immersed in an aqueous solution containing ethylene dioxythiophene for electropolymerization, and a ethylene dioxythiophene layer is formed on the surface of the molybdenum disulfide nanoparticle modified layer to obtain the working electrode. (3) The working electrode, reference electrode and counter electrode from step (2) are combined to form a three-electrode system, thus obtaining an electrochemical sensor.

[0021] Preferably, the substrate electrode in step (1) has undergone surface pretreatment and activation treatment.

[0022] Preferably, the specific process of the surface pretreatment is as follows: the surface of the substrate electrode is polished into a mirror surface by Al2O3 powder with diameters of 0.3 and 0.05 μm in sequence, then rinsed with water and ultrasonically cleaned in anhydrous ethanol and water in sequence, then taken out and washed with water and air-dried at room temperature.

[0023] Preferably, the specific process of the activation treatment is as follows: the substrate electrode is immersed in sulfuric acid solution until the curve is stable when scanned by cyclic voltammetry at a potential of -1.0V to 1.0V.

[0024] Preferably, the ethylenedioxythiophene content in the aqueous solution containing ethylenedioxythiophene in step (2) is 0.01 mol / L.

[0025] Preferably, the electropolymerization method used in step (2) is cyclic voltammetry, with a potential range of -0.2 V to 1.2 V, a scanning speed of 100 mV / s, and 20 cyclic scans.

[0026] Thirdly, the present invention provides a method for detecting lead ions, comprising the following steps: Using the electrochemical sensor described in the first aspect, the sample to be tested is subjected to square wave anodic stripping voltammetry. After measuring the current value of the stripping peak, the concentration of lead ions in the sample to be tested is obtained by quantitative analysis based on the lead ion standard curve.

[0027] Preferably, the method for detecting lead ions includes the following steps: (1) Plotting the standard curve: The working electrode in the electrochemical sensor described in the first or second aspect is placed in lead ion solutions of different concentrations, and enrichment and dissolution are carried out by square wave anodic stripping voltammetry. The peak current change when lead ions dissolve in solutions of known concentrations is detected, and the standard curve is plotted by analysis. (2) Sample detection: The working electrode in step (1) is placed on the liquid sample to be tested and enriched and dissolved by square wave anodic stripping voltammetry. The peak current change when lead ions in the solution are dissolved is detected, and the content of lead ions in the liquid sample to be tested is calculated based on the standard curve in step (1).

[0028] Preferably, the square wave anodic stripping voltammetry is used to enrich and dissolve the test solution; during the enrichment process, the control potential is -0.7 V; the enrichment time is 240 s; during the dissolution process, the control potential is -0.8~0 V; the measurement parameters of the square wave stripping voltammetry are: potential increment of 4 mV, amplitude of 25 mV, and frequency of 15 Hz. Preferably, the lead ion solutions of different concentrations in step (1) are prepared by mixing lead nitrate and acetic acid solutions.

[0029] Preferably, the concentration of the lead ion solution in step (1) is 1 nmol / L ~ 2.5 μmol / L.

[0030] Preferably, the linear correlation coefficient of the standard curve in step (1) is R. 2 = 0.9974.

[0031] The principle of this invention is as follows: First, molybdenum disulfide nanoparticles are prepared, which have a large specific surface area. Modifying the substrate electrode with these nanoparticles is beneficial for the loading and bonding of subsequent materials. Then, a polyethylene dioxythiophene layer is electropolymerized on the surface of the molybdenum disulfide nanoparticle-modified layer. Polyethylene dioxythiophene has good conductivity. Finally, the working electrode, reference electrode, and counter electrode are combined to form a three-electrode system, ultimately obtaining a novel electrochemical sensor for detecting lead ions.

[0032] The beneficial effects of this invention are: the electrochemical sensor of this invention can be used for the detection of lead ions, has a wide detection range and a low detection limit, the reaction is carried out at room temperature, the performance is stable, and it has good application prospects.

[0033] Specifically: (1) The electrochemical sensor of the present invention has good electron transfer properties, can transfer electrons generated by the reaction well, and can realize the detection of lead ions with fast reaction speed; (2) The electrochemical sensor of the present invention has good reproducibility and stability, can accurately detect lead ions, and has strong anti-interference ability; (3) The electrochemical sensor of the present invention can be used for the detection of lead ions in aqueous solution. It has high specificity. In the concentration range of 1 nmol / L to 2.5 μmol / L, the response current is linearly related to the change in lead ion concentration. The linear relationships are as follows: Δ I Pb = 0.0039 C Pb +57.174, correlation coefficient R 2 = 0.9974; the detection limit is 1 nmol / L (S / N=3). The reaction is carried out at room temperature, the performance is stable, and it has good application prospects. Attached Figure Description

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0035] Figure 1 This is a schematic diagram of the preparation process of the polyethylene dioxythiophene / molybdenum disulfide nanoparticle / glassy carbon electrode in Example 1 of the present invention.

[0036] Figure 2 This is a voltammetric curve of the polyethylene dioxythiophene modified layer formed by electropolymerization in an aqueous solution containing ethylene dioxythiophene in Example 1 of the present invention.

[0037] Figure 3Cyclic voltammetry diagrams of glassy carbon electrode, molybdenum disulfide nanoparticle / glassy carbon electrode described in Example 1, and polyethylene dioxythiophene / molybdenum disulfide nanoparticle / glassy carbon electrode in K3Fe(CN)6 standard solution.

[0038] Figure 4 This is the voltammetric curve corresponding to the detection of lead ion solution using an electrochemical sensor in Example 2 of the present invention.

[0039] Figure 5 This is a graph showing the variation of lead ion dissolution peak current under different enrichment potentials and enrichment times in Example 2 of the present invention.

[0040] Figure 6 This is a graph showing the change in the lead ion dissolution peak current in the reaction substrate at different pH values ​​in Example 2 of the present invention. Detailed Implementation

[0041] The present invention will be further explained and described below with reference to specific embodiments.

[0042] In the following examples, unless otherwise specified, the raw materials and instruments used are commercially available, the processes used are conventional processes, the equipment used is conventional equipment, and the data obtained are the average values ​​of more than three repeated experiments.

[0043] Unless otherwise specified, the electrochemical workstation used in this invention is manufactured by Shanghai Chenhua Instrument Co., Ltd., model CHI660E; the platinum electrode used in this invention is a platinum wire electrode manufactured by Wuhan Gaoshi Ruilian Technology Co., Ltd.; the glassy carbon electrode, platinum wire electrode, and Ag / AgCl electrode used in this invention are all commercially available products.

[0044] In the accompanying drawings of this invention, the signs of current and potential only indicate direction, and the absolute values ​​of current and potential represent the current value or magnitude and the potential value or magnitude, respectively. Unless otherwise specified, current and potential in this article refer to the magnitude of current and the magnitude of potential, respectively.

[0045] The preparation of the potassium ferricyanide standard solution used in this invention includes the following steps: under the condition of 20-25℃ (room temperature), accurately weigh 0.1645 g of potassium ferricyanide and 7.4500 g of potassium chloride, then dissolve them in ultrapure water and make up to 100 mL to obtain potassium ferricyanide standard solution (5 mM K3Fe(CN)6 + 1 M KCl). Example

[0046] This embodiment provides a method for preparing a polyethylene dioxythiophene / molybdenum disulfide nanoparticle / glassy carbon electrode, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps: (1) At room temperature (20-25℃), the glassy carbon electrode (3 mm in diameter) was polished into a mirror surface by Al2O3 powder with diameters of 0.3 μm and 0.05 μm, then rinsed with distilled water and ultrasonically cleaned in anhydrous ethanol and distilled water for 2 min each. The glassy carbon electrode was then placed in a sulfuric acid solution with a concentration of 0.5 mol / L and activated by cyclic voltammetry at -1.0 V to 1.0 V until stable. The electrode surface was then washed with distilled water and placed in a 15 mL potassium ferricyanide solution and detected by cyclic voltammetry at 0 V to 0.8 V for 1 cycle. The electrode was then removed, rinsed with distilled water, and air-dried at room temperature to obtain the pretreated glassy carbon electrode. (2) At room temperature (20-25℃), the molybdenum disulfide nanoparticle dispersion is coated on the surface of the glassy carbon electrode treated in step (1), dried, and a molybdenum disulfide nanoparticle modification layer is formed on the surface of the glassy carbon electrode to obtain a glassy carbon electrode modified with molybdenum disulfide nanoparticles. The molybdenum disulfide nanoparticles in step (2) were prepared by the following method: 3.04 g of thiourea and 1.4 g of ammonium molybdate hydrate were accurately weighed into a beaker, 40 ml of distilled water was added and stirred to dissolve, the mixture was transferred to a reaction vessel, and reacted at 180 °C for 10 hours. After centrifugation and washing three times, the mixture was placed in an oven and dried at 60 °C for 12 hours to obtain molybdenum disulfide. The molybdenum disulfide nanoparticle dispersion in step (2) is prepared by the following method: under the condition of 20-25 ℃ (room temperature), accurately weigh 1 mg of molybdenum disulfide nanoparticles into a clean and dry glass bottle, add 1 mL of distilled water and mix it evenly under the assistance of ultrasound to obtain the molybdenum disulfide nanoparticle dispersion. (3) The glassy carbon electrode modified with molybdenum disulfide nanoparticles obtained in step (2) is immersed in an aqueous solution of ethylene dioxythiophene and electropolymerized by cyclic voltammetry to form a ethylene dioxythiophene layer on the surface of the molybdenum disulfide nanoparticle modified layer, thus completing the preparation of the electrochemical sensor. The volume of the ethylenedioxythiophene aqueous solution used in step (3) is 15 ml, and the ethylenedioxythiophene content is 0.01 mol / L. The parameters of the cyclic voltammetry are: potential range of -0.2 V to 1.2 V, scan rate of 100 mV / s, and 40 scan segments.

[0047] Figure 2 This is a voltammetric curve of the polyethylene dioxythiophene modified layer formed by electropolymerization in an aqueous solution containing ethylene dioxythiophene in Example 1 of the present invention. Figure 2It can be seen that with each scan, the current intensity at the -0.2 V potential increases and the current intensity at the 1.2 V potential decreases. The values ​​of increase and decrease are uniform and fixed in the first ten scans, while the overall current intensity of the curve in the last ten scans tends to be stable. This indicates that a polyethylene dioxythiophene layer is formed on the surface of the molybdenum disulfide nanoparticle modification layer, thus enabling the successful preparation of a polyethylene dioxythiophene-molybdenum disulfide nanoparticle-glassy carbon electrode.

[0048] Figure 3 Cyclic voltammetry plots of the glassy carbon electrode (GCE), the molybdenum disulfide nanoparticle / glassy carbon electrode (MoS2 / GCE) described in Example 1, and the poly(ethylene dioxythiophene) / molybdenum disulfide nanoparticle / glassy carbon electrode (pEDOT / MoS2 / GCE) in K3Fe(CN)6 standard solution at a scan rate of 50 mV / s are shown in the figure. The curve measured by the bare glassy carbon electrode shows a pair of redox peaks. When a layer of molybdenum disulfide nanoparticles is modified on the surface of the glassy carbon electrode, the current values ​​of both the oxidation and reduction peaks are significantly reduced. When a layer of poly(ethylene dioxythiophene) film is electropolymerized and modified on the surface of the molybdenum disulfide nanoparticle / glassy carbon electrode, the current intensity of both redox peaks reaches its maximum, and the peak shape is more prominent, indicating that the composite modified electrode has the best electron transfer capability.

[0049] Example 2 An application of an electrochemical sensor in the detection of lead ions in an aquatic environment includes the following steps: (1) Construction of an electrochemical sensor: Using the glassy carbon electrode with surface-modified polyethylene dioxythiophene / molybdenum disulfide nanoparticles prepared in Example 1 as the working electrode, Ag / AgCl as the reference electrode, and platinum wire electrode as the counter electrode, a three-electrode system was established and connected to an electrochemical workstation to form an electrochemical sensor. (2) At room temperature, the test solution is placed in the electrochemical sensor constructed in step (1), and the test solution is enriched and dissolved using the square wave anodic stripping voltammetry method. Specifically, the Pb in the test solution is removed. 2 + Pre-enrichment was performed on the working electrode at a pre-enrichment potential of -0.7 V for 240 s. After pre-enrichment, Pb was further enriched at -0.45 V. 2 + Pb was obtained by dissolution from the working electrode. 2+ Peak current value during dissolution, such as Figure 4 As shown. In this step, the test solution is a mixture of lead ions and an acetate buffer solution, wherein the pH value of the acetate buffer solution is 3; (3) Based on the peak current results of lead ion dissolution obtained in step (2), the concentration of lead ions in the test solution is calculated using the linear regression equation constructed by lead ion concentration and peak current.

[0050] Different concentrations of Pb were detected using the electrochemical sensor described in Example 3 above. 2 + Standard solution (Pb) 2+ Standard solutions were used in gradients of 1 nmol / L, 10 nmol / L, 20 nmol / L, 50 nmol / L, 0.1 μmol / L, 0.5 μmol / L, 1 μmol / L, 1.5 μmol / L, 2 μmol / L, and 2.5 μmol / L to obtain different concentrations of Pb. 2 + The peak current value at dissolution of the standard solution was obtained, and a linear regression equation for lead ion concentration was constructed based on the relationship between concentration and peak current, as shown below.

[0051] The linear regression equation constructed from the changes in lead ion concentration and peak current is as follows: I Pb = 0.0039 C Pb + 57.174 (1) In equation (1), I Pb For Pb 2+ Peak current value during dissolution, in μA; C Pb Pb in buffer solution 2+ The concentration of Pb in the same sample is expressed in nmol / L. 2+ The relative standard deviation of three parallel determinations was 3.1%, and the limit of detection was 1 nmol / L.

[0052] In this embodiment, the effects of enrichment potential and enrichment time on the detection effect were investigated. Specifically, an aqueous solution containing 1 μmol / L lead ions was detected at different enrichment potentials and enrichment times according to the method in Example 2. A 3D bar graph was plotted based on the changes in peak current, as shown below. Figure 5 As shown.

[0053] Figure 5 This refers to Pb under different enrichment potentials and enrichment times in Example 2 of the present invention. 2 + A graph showing the variation of dissolution peak current. (See figure.) Figure 5 As shown, Pb can be clearly observed. 2+ The dissolution peak current first increases and then decreases with the increase of enrichment potential and enrichment time, and the peak current value reaches the maximum when the enrichment potential is -0.7 V and the enrichment time is 240 s.

[0054] In this embodiment, the effect of different pH conditions on the detection effect was also investigated. Specifically, aqueous solutions containing 1 μmol / L lead ions at different pH values ​​were detected according to the method in Example 2, and the results are as follows. Figure 6As shown.

[0055] Figure 6 Pb in the reaction substrate at different pH values ​​in Example 2 of this invention 2 + Dissolution peak current variation graph. As shown in Figure 6, Pb 2+ The response current increases with increasing pH, reaching a maximum at pH 3, after which it decreases with further increases in pH. This may be because at lower pH values, H+... + At high concentrations, it undergoes a reduction reaction on the working electrode surface, reacting with Pb. 2+ Competition arises; and as the pH increases, OH groups near the electrode surface... - It may be easy to work with Pb 2+ Complexation reaction occurs, affecting Pb 2 + Deposition on the electrode surface leads to a decrease in the lead leaching peak current. Therefore, the optimal pH for leaching detection is 3.

[0056] Example 3 The interference immunity of the electrochemical sensor was investigated, including the following steps: Adding ten times the concentration of Cu to an electrolyte solution with a lead ion concentration of 1 μmol / L. 2+ NO3 - Zn 2+ Fe 3+ Cl - K + Na + Cd 2+ The concentrations of various heavy metal ions in the above samples (test solutions) were detected according to the application method in Example 3. The results showed that the aforementioned interfering ions significantly affected Pb. 2+ The dissolution peak potential and current are basically unaffected.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electrochemical sensor for detecting lead ions, the electrochemical sensor comprising a working electrode in a three-electrode system, characterized in that: The surface of the working electrode is modified with molybdenum disulfide and polyethylene dioxythiophene.

2. The electrochemical sensor according to claim 1, characterized in that: The polyethylene dioxythiophene in the modified layer is made by electropolymerization of ethylene dioxythiophene.

3. The method for preparing the electrochemical sensor according to claim 2, characterized in that, Before use, the working electrode also undergoes the following treatment: (1) Grind, polish and clean the reaction end surface of the working electrode; (2) Place the cleaned substrate electrode from step (1) in an acidic solution for electrochemical treatment until the current during the electrochemical treatment process reaches a stable level, thereby obtaining an activated substrate electrode.

4. The method for preparing the electrochemical sensor according to claim 3, characterized in that, In step (1), the base electrode is a glassy carbon electrode; the polishing is to polish the reaction end surface of the working electrode with alumina powder; during the polishing process, when polishing with alumina powder, Al2O3 powder with diameters of 0.3 and 0.05 μm is polished into a mirror surface, then rinsed with water and ultrasonically cleaned in anhydrous ethanol and water in sequence, then taken out and washed with water and air-dried at room temperature; In step (2), the working electrode after cleaning in step (1) is electrochemically treated using cyclic voltammetry. During the electrochemical treatment, the scanning potential range of the cyclic voltammetry is -1.0 V to 1.0 V, and the scanning rate is 100 mV / s. The acidic solution is a dilute sulfuric acid solution with a concentration of 0.5 mol / L.

5. A method for preparing the electrochemical sensor according to any one of claims 1 to 2, characterized in that, Includes the following steps: (1) The molybdenum disulfide nanoparticle dispersion was coated on the surface of the activated substrate electrode and dried to form a molybdenum disulfide particle modification layer on the surface of the activated substrate electrode. (2) The electrode from step (1) is immersed in an ethylene dioxythiophene solution for electropolymerization to form a polyethylene dioxythiophene layer on the surface of the molybdenum disulfide nanoparticle modified layer, thus obtaining the working electrode.

6. The method for preparing the electrochemical sensor according to claim 5, characterized in that: The preparation method of the molybdenum disulfide nanoparticle dispersion in step (1) is as follows: 1 mg of molybdenum disulfide nanoparticles are placed in a clean and dry glass bottle, 1 mL of distilled water is added, and the mixture is made uniform under ultrasonic assistance; the electropolymerization method in step (2) is cyclic voltammetry, with a potential range of -0.2 V ~ 1.2 V, a scanning speed of 100 mV / s, and 20 cyclic scans.

7. The application of an electrochemical sensor as described in claim 1 or 2, or an electrochemical sensor prepared by any one of the preparation methods in claim 5, in the detection of lead ions in an aquatic environment.

8. The application according to claim 7, characterized in that, Includes the following steps: (1) An electrochemical sensor was constructed using a working electrode with a molybdenum disulfide modified layer and a polyethylene dioxythiophene layer on its surface; (2) The electrochemical sensor constructed in step (1) is placed in the test solution for enrichment and dissolution, and the peak current change when lead ions in the test solution are dissolved is detected. (3) Based on the peak current change results obtained in step (2) when lead ions dissolve, the concentration of lead ions in the test solution is calculated by using the linear regression equation constructed by the lead ion concentration and the peak current change.

9. The application according to claim 8, characterized in that, In step (3), the linear regression equation constructed by the lead ion concentration and peak current is as follows: I Pb = 0.0039 C Pb + 57.174 (1) In equation (1), I Pb For Pb 2+ Peak current value during dissolution, in μA; C Pb Pb in buffer solution 2+ The concentration of Pb in the same sample is expressed in nmol / L. 2+ The relative standard deviation of three parallel determinations was 3.1%, and the limit of detection was 1 nmol / L.

10. The application according to claim 8 or 9, characterized in that, In step (1), a three-electrode system is established by using a working electrode, a reference electrode, and a counter electrode with a surface modified with a molybdenum disulfide layer and a polyethylene dioxythiophene layer. This system is then connected to an electrochemical workstation to form an electrochemical sensor. The reference electrode is an Ag / AgCl electrode. The counter electrode is a platinum electrode; in step (2), the square wave anodic stripping voltammetry is used to enrich and dissolve the test solution; during the enrichment process, the control potential is -0.7 V; the enrichment time is 240 s; during the dissolution process, the control potential is -0.8 V to 0 V; the measurement parameters of the square wave stripping voltammetry are: potential increment of 4 mV, amplitude of 25 mV, and frequency of 15 Hz; the Pb in the test solution 2+ The concentration ranges from 1 nmol / L to 2.5 μmol / L.

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