A platinum-porous silver composite electrode and its preparation method and application in neurotransmitter molecule detection

Abstract

The present invention provides a platinum-porous silver composite electrode and a preparation method thereof and an application thereof in the detection of neurotransmitter molecules. Specifically, a method of electrochemical in-situ modification is adopted to in-situ modify a metal platinum material on the surface of porous silver to obtain a Pt-porous Ag composite electrode. The performance of the electrode modification material is stable, the reliability of the electrode is improved, and at the same time, the two highly catalytically active materials are compounded, which greatly improves the sensitivity of the electrode to the detection of trace neurotransmitter molecules, while reducing the preparation cost, realizing the separate detection and simultaneous detection of biological molecules in a complex environment, and can realize the instant detection of trace neurotransmitter molecules tryptophan and methionine.

Description

Technical Field

[0001] The invention belongs to the field of biosensors, and in particular relates to a platinum-porous silver composite electrode and a preparation method thereof and application thereof in neurotransmitter molecule detection. Background Art

[0002] The nervous system is the most complex system in the body in terms of structure and function, and understanding it depends to a large extent on the detection of neuroelectrophysiological signals. Neurotransmitters play an important role in the activities of the nervous system. They are special chemicals released by nerve endings that can act on receptors on the membranes of neurons or effector cells to complete the function of information transmission. Tryptophan is a precursor of a very important neurotransmitter (5-hydroxytryptamine) in the human body. It can promote the secretion of 5-hydroxytryptamine, improve the quality of sleep, and stabilize emotions. Methionine is also a very important amino acid in the human body. It promotes the synthesis of important hormones such as melatonin and adrenaline in the human body, and has important uses in human metabolism and anti-depression.

[0003] Based on this, the present invention prepares an electrochemical electrode that can be used for the detection of neurotransmitter molecules, which can achieve accurate detection of specific neurotransmitter molecules through the principle of biological molecule detection. Summary of the invention

[0004] The purpose of the present invention is to provide a platinum-porous silver composite electrode and a preparation method thereof and application thereof in neurotransmitter molecule detection.

[0005] The present invention provides a method for preparing a platinum-porous silver composite electrode, which specifically comprises the following steps:

[0006] S1. Depositing a silver-tin alloy layer on the surface of the composite electrode substrate by an electrodeposition method, and obtaining a porous silver layer by a constant potential dealloying method;

[0007] S2. Using porous silver as a substrate, in-situ modifying metallic platinum on its surface to prepare a platinum-porous silver composite electrode.

[0008] Furthermore, in step S1, the electrodeposition method is specifically as follows: a three-electrode system is used, the counter electrode is a platinum sheet, the reference electrode is an Ag / AgCl electrode, the composite electrode is used as the working electrode, and the electrodeposition reaction is carried out by immersing the composite electrode in a silver-tin solution, and the current density is set to 10-20 mA cm -2 , stirring is required during the electrodeposition process, and the stirring speed is 500-600rpm.

[0009] The silver-tin solution specifically comprises: 20-30 g / L of silver methanesulfonate, 30-40 g / L of tin methanesulfonate, 30-50 g / L of pyrophosphoric acid, and 30-50 g / L of EDTA.

[0010] Further, in step S1, the dealloying method is specifically as follows: a three-electrode system is used, with a composite electrode modified with a silver-tin alloy layer as the working electrode, a counter electrode is a platinum sheet, a reference electrode is an Ag / AgCl electrode, the solution is a 0.8-1.0M sulfuric acid solution, a constant potential method is used, a voltage of 10-20mV is applied, and the dealloying time is 500-600s to obtain a porous silver modified layer.

[0011] Furthermore, in step S2, the preparation method of the platinum-porous silver composite electrode is specifically as follows: porous silver is used as the working electrode, the Pt electrode is used as the counter electrode, and the Ag / AgCl electrode is used as the reference electrode, immersed in a platinum solution, and continuously deposited at a constant potential of -0.5V for 20 to 30s. Continuous stirring is required during the deposition process, and the stirring speed is 300 to 500rpm. Subsequently, it is rinsed with deionized water and dried at 60°C to obtain a platinum-porous silver composite electrode.

[0012] The platinum electrodeposition solution specifically comprises: 1-2 mM chloroplatinic acid, 0.01-0.03 g / mL potassium nitrate and 0.01-0.02 g / mL polyvinyl pyrrolidone.

[0013] Another object of the present invention is to provide a platinum-porous silver composite electrode, wherein four electrodes are coplanarly arranged on the surface of an electrode substrate, namely a working electrode (1), a reference electrode (2), a counter electrode (3) and a counter electrode (4), wherein the upper ends of the working electrode (1) and the counter electrode (3) vertically extend out comb-shaped equidistant interdigitated strips to form an interdigitated structure, the reference electrode (2) is arranged below the middle of the interdigitated structure, and the counter electrode (4) is located outside the interdigitated structure, the platinum-porous silver composite electrode serves as the working electrode, the surface of the reference electrode (2) is modified with silver-silver chloride, and the surfaces of the counter electrode (3) and the counter electrode (4) are modified with platinum.

[0014] The platinum-porous silver composite electrode provided by the present invention takes a metal electrode as a substrate, comprises an electrode substrate and an electrode modification layer, wherein the electrode modification layer is located above the electrode substrate, and the electrode modification layer comprises a platinum-porous silver modification layer, specifically, a silver-tin alloy is deposited on the surface of the electrode substrate, a porous silver layer is obtained after dealloying, and then metal platinum particles are modified on the surface.

[0015] The thickness of the porous silver is 0.01-0.03 mm; the surface of the porous silver is modified with platinum metal particles, which are arranged evenly and densely, and the particle size is 0.5-1.5 μm.

[0016] The surface morphology of the platinum-porous silver composite electrode prepared by the present invention was observed by scanning electron microscope (SEM).

[0017] As attached Figure 1The figure shows the surface morphology of the platinum-porous silver composite electrode prepared by the present invention. As can be seen from the figure, the electrode surface is modified with platinum metal particles, the particles are arranged uniformly and orderly, the particle size is 0.5-1.5 μm, and the high surface area provides more catalytic active points, greatly improving the sensitivity of sensor detection.

[0018] As attached Figure 2 As shown, it is a schematic diagram of the structure of the platinum-porous silver composite electrode prepared by the present invention. As can be seen from the figure, the lower end of the four-electrode coplanar interdigitated electrode substrate is equidistantly provided with electrode pins, and the electrode pins are respectively connected to the electrode sheets, specifically including a working electrode (1), a reference electrode (2), a counter electrode (3) and a counter electrode (4), wherein the working electrode (1) and the counter electrode (3) constitute an interdigitated electrode structure, and a reference electrode (2) is arranged in the middle of the two electrodes and at the lower part of the interdigitated structure, and the counter electrode (4) is located on the right side of the counter electrode (3) and outside the interdigitated structure. The interdigitated structure part at the upper end of the substrate is the electrode detection area, and the working electrode (1), the reference electrode (2), and the counter electrode (3) can constitute a three-electrode detection system, and the working electrode (1), the reference electrode (2), and the counter electrode (3) can constitute another three-electrode detection system, which greatly improves the accuracy and sensitivity of the electrode.

[0019] Another object of the present invention is to provide an application of a platinum-porous silver composite electrode in the detection of neurotransmitter molecules, which can specifically realize the separate detection and simultaneous detection of tryptophan and methionine molecules.

[0020] The response performance of the platinum-porous silver composite electrode prepared by the present invention to tryptophan and methionine molecules was tested by differential pulse voltammetry, and the solution used in the test was 0.1 M PBS solution (pH 5.0).

[0021] As attached Figure 3 As shown, the DPV curves of the platinum-porous silver composite electrode prepared by the present invention for detecting different concentrations of (a, b) tryptophan and (c, d) methionine molecules, as well as the relationship curve between the corresponding current density and concentration, specifically the DPV response curves for testing 0-240μM tryptophan and 0-3.2mM methionine molecules, and the relationship between the corresponding oxidation peak current density and concentration. It can be seen from the figure that as the concentrations of tryptophan and methionine increase, the response current shows a trend of gradually increasing, indicating that the platinum-porous silver composite electrode prepared by the present invention has excellent response characteristics to the two molecules.

[0022] At the same time, it can be seen from the figure that its peak current density has a good linear relationship with the concentration, and its fitting values ​​are 0.9943, 0.9957 and 0.9906, 0.9966 respectively. Its linear range is divided into two different stages. This is because when the concentration of neurotransmitter molecules is low, there are more active sites on the electrode surface, so the electrode responds faster; and as the molecular concentration increases, it needs to diffuse to more active sites to complete the catalytic reaction. This diffusion process takes more time, and also makes it impossible for the analytes at some active sites to be replenished in time, thereby reducing the response sensitivity.

[0023] As attached Figure 4 As shown, the DPV curves of the platinum-porous silver composite electrode prepared in the present invention for simultaneous detection of (a, b) tryptophan and (a, c) methionine and the relationship between the corresponding oxidation peak current density and concentration. It can be seen from the figure that the response current density of the two analytes, tryptophan and methionine, increases with the increase of their concentrations, and their peak current density and concentration have a good linear relationship.

[0024] At the same time, it can be seen from the figure that the current peaks at 0.77V and 1.26V correspond to the oxidation peaks of tryptophan and methionine, respectively, indicating that the platinum-porous silver composite electrode can realize the simultaneous detection of tryptophan and methionine. It can be calculated that the detection limits of the simultaneous detection of tryptophan and methionine by the platinum-porous silver composite electrode prepared by the present invention are 0.067μμM and 6.5μμM (S / N=3), respectively.

[0025] As attached Figure 5 As shown, the stability test of the platinum-porous silver composite electrode prepared by the present invention for continuous detection of (a) tryptophan and (b) methionine molecules, specifically using 5 platinum-porous silver composite electrodes prepared in different batches, and testing their response performance every day, and the detection time lasts for one week. It can be seen from the figure that in the continuous test lasting one week, the response current of the composite electrode to tryptophan and methionine decreased by 1.4% and 1.1% respectively compared with the first day. This result shows that the platinum-porous silver composite electrode prepared by the present invention has good stability.

[0026] The present invention adopts an electrochemical in-situ modification method to in-situ modify metal platinum materials on the porous silver surface, thereby ensuring the stable performance of the electrode modification material and improving the reliability of the electrode. At the same time, two high catalytic activity materials are compounded to greatly improve the electrode's sensitivity to detecting trace neurotransmitter molecules, while reducing the preparation cost and realizing the separate detection and simultaneous detection of biological molecules in complex environments.

[0027] The beneficial effects of the present invention are:

[0028] (1) The present invention combines highly catalytically active porous silver with platinum, which greatly improves the sensitivity of electrode detection and can achieve simultaneous detection of tryptophan and methionine in a complex environment.

[0029] (2) The present invention adopts an electrochemical-in-situ modification method, which avoids the performance degradation of the modified material during the transfer process and improves the stability and reliability of the sensing electrode.

[0030] (3) The electrodes prepared by the present invention can realize accurate detection of neurotransmitter molecules. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention is further described using the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the invention. A person skilled in the art can obtain other drawings based on the following drawings without creative work.

[0032] Figure 1 is a surface morphology of the platinum-porous silver composite electrode prepared by the present invention;

[0033] Figure 2 Schematic diagram of the structure of the platinum-porous silver composite electrode prepared by the present invention;

[0034] Figure 3 The DPV curves of the platinum-porous silver composite electrode prepared by the present invention for detecting (a, b) tryptophan and (c, d) methionine molecules of different concentrations, and the relationship curve between the corresponding current density and concentration;

[0035] Figure 4 The DPV curves of the platinum-porous silver composite electrode prepared by the present invention for simultaneous detection of (a, b) tryptophan and (a, c) methionine and the relationship between the corresponding oxidation peak current density and concentration;

[0036] Figure 5 The present invention is a stability test of the platinum-porous silver composite electrode prepared by the present invention for continuously detecting (a) tryptophan and (b) methionine molecules.

[0037] Legend:

[0038] 1. Working electrode; 2. Reference electrode; 3. Counter electrode; 4. Counter electrode DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail in conjunction with the following specific embodiments and with reference to the accompanying drawings.

[0040] Example 1

[0041] Preparation of platinum-porous silver composite electrode:

[0042] S1. Prepare porous silver modified layer. First, prepare the electrodeposition silver tin solution, the specific composition is: 20g / L silver methanesulfonate, 30g / L tin methanesulfonate, 30g / L pyrophosphate, 30g / L EDTA. Use a three-electrode system, the counter electrode is a platinum sheet, the reference electrode is an Ag / AgCl electrode, the composite electrode is the working electrode, and the current density is selected as 10mA·cm -2 , stirring speed was 500rpm, silver-tin alloy layer was prepared. Then, constant potential dealloying method was adopted, with composite electrode modified with Ag-Sn alloy as working electrode, platinum sheet as counter electrode, Ag / AgCl electrode as reference electrode, 0.8M sulfuric acid solution, constant potential method, 10mV voltage was applied, dealloying time was 500s, and porous silver modified layer was obtained.

[0043] S2. Prepare a platinum-porous silver composite electrode. First, prepare a platinum electrodeposition solution, the specific composition is: 1mM chloroplatinic acid, 0.01g / mL potassium nitrate and 0.01g / mL polyvinyl pyrrolidone. Then, use porous silver as the working electrode, Pt electrode as the counter electrode, and Ag / AgCl electrode as the reference electrode, immerse in the platinum electrodeposition solution, and continuously deposit for 30s at a constant potential of -0.5V, with a stirring speed of 300rpm, then rinse with deionized water and dry at 60°C to obtain a platinum-porous silver composite electrode.

[0044] The platinum-porous silver composite electrode prepared as above is used as the working electrode 1, silver-silver chloride is modified on the surface of the coplanar reference electrode 2, and platinum is modified on the surfaces of the counter electrode 3 and the counter electrode 4, so as to obtain a standard electrode with four coplanar electrodes, wherein the upper ends of the working electrode 1 and the counter electrode 3 extend with mutually interlaced comb-shaped equidistant interdigitated strips to form an interdigitated electrode structure, the upper end of the reference electrode 2 is located below the interdigitated structure, and can form a three-electrode system with the interdigitated electrode structure; the upper end of the counter electrode 4 is located outside the interdigitated electrode structure, and can form another three-electrode system with it.

[0045] Example 2

[0046] Preparation of platinum-porous silver composite electrode:

[0047] S1. Prepare porous silver modified layer. First, prepare the electrodeposition silver tin solution, the specific composition is: 30g / L silver methanesulfonate, 40g / L tin methanesulfonate, 50g / L pyrophosphate, 50g / L EDTA. Use a three-electrode system, the counter electrode is a platinum sheet, the reference electrode is an Ag / AgCl electrode, the composite electrode is the working electrode, and the current density is selected as 20mA·cm -2, stirring speed is 600rpm, silver-tin alloy layer is prepared. Then, constant potential dealloying method is adopted, with composite electrode modified with Ag-Sn alloy as working electrode, counter electrode is platinum sheet, reference electrode is Ag / AgCl electrode, solution is 1.0M sulfuric acid solution, constant potential method is adopted, voltage of 20mV is applied, dealloying time is 600s, and porous silver modified layer is obtained.

[0048] S2. Prepare a platinum-porous silver composite electrode. First, prepare a platinum electrodeposition solution, the specific composition of which is: 2mM chloroplatinic acid, 0.03g / mL potassium nitrate and 0.02g / mL polyvinyl pyrrolidone. Then, use porous silver as the working electrode, Pt electrode as the counter electrode, and Ag / AgCl electrode as the reference electrode, immerse in the platinum electrodeposition solution, and continuously deposit for 20s at a constant potential of -0.5V with a stirring speed of 500rpm. Then rinse with deionized water and dry at 60°C to obtain a platinum-porous silver composite electrode.

[0049] The platinum-porous silver composite electrode prepared as above is used as the working electrode 1, silver-silver chloride is modified on the surface of the coplanar reference electrode 2, and platinum is modified on the surfaces of the counter electrode 3 and the counter electrode 4, so as to obtain a standard electrode with four coplanar electrodes, wherein the upper ends of the working electrode 1 and the counter electrode 3 extend with mutually interlaced comb-shaped equidistant interdigitated strips to form an interdigitated electrode structure, the upper end of the reference electrode 2 is located below the interdigitated structure, and can form a three-electrode system with the interdigitated electrode structure; the upper end of the counter electrode 4 is located outside the interdigitated electrode structure, and can form another three-electrode system with it.

[0050] Example 3

[0051] Preparation of platinum-porous silver composite electrode:

[0052] S1. Prepare porous silver modified layer. First, prepare the electrodeposition silver tin solution, the specific composition is: 25g / L silver methanesulfonate, 35g / L tin methanesulfonate, 40g / L pyrophosphate, 40g / L EDTA. Use a three-electrode system, the counter electrode is a platinum sheet, the reference electrode is an Ag / AgCl electrode, the composite electrode is the working electrode, and the current density is selected to be 15mA·cm -2 , stirring speed was 500rpm, silver-tin alloy layer was prepared. Then, constant potential dealloying method was adopted, with composite electrode modified with Ag-Sn alloy as working electrode, platinum sheet as counter electrode, Ag / AgCl electrode as reference electrode, 0.9M sulfuric acid solution, constant potential method, 15mV voltage was applied, dealloying time was 600s, and porous silver modified layer was obtained.

[0053] S2. Prepare a platinum-porous silver composite electrode. First, prepare a platinum electrodeposition solution, the specific composition of which is: 2mM hydroplatinic acid, 0.02g / mL potassium nitrate and 0.02g / mL polyvinyl pyrrolidone. Then, use porous silver as the working electrode, Pt electrode as the counter electrode, and Ag / AgCl electrode as the reference electrode, immerse in the platinum electrodeposition solution, and continuously deposit for 20s at a constant potential of -0.5V with a stirring speed of 400rpm. Then rinse with deionized water and dry at 60°C to obtain a platinum-porous silver composite electrode.

[0054] The platinum-porous silver composite electrode prepared as above is used as the working electrode 1, silver-silver chloride is modified on the surface of the coplanar reference electrode 2, and platinum is modified on the surfaces of the counter electrode 3 and the counter electrode 4, so as to obtain a standard electrode with four coplanar electrodes, wherein the upper ends of the working electrode 1 and the counter electrode 3 extend with mutually interlaced comb-shaped equidistant interdigitated strips to form an interdigitated electrode structure, the upper end of the reference electrode 2 is located below the interdigitated structure, and can form a three-electrode system with the interdigitated electrode structure; the upper end of the counter electrode 4 is located outside the interdigitated electrode structure, and can form another three-electrode system with it.

[0055] Example 4

[0056] Preparation of platinum-porous silver composite electrode:

[0057] S1. Prepare porous silver modified layer. First, prepare the electrodeposition silver tin solution, the specific composition is: 27g / L silver methanesulfonate, 36g / L tin methanesulfonate, 45g / L pyrophosphate, 45g / L EDTA. Use a three-electrode system, the counter electrode is a platinum sheet, the reference electrode is an Ag / AgCl electrode, the composite electrode is the working electrode, and the current density is selected to be 15mA·cm -2 , stirring speed was 600rpm, silver-tin alloy layer was prepared. Then, constant potential dealloying method was adopted, with composite electrode modified with Ag-Sn alloy as working electrode, platinum sheet as counter electrode, Ag / AgCl electrode as reference electrode, 1.0M sulfuric acid solution as solution, constant potential method was adopted, 15mV voltage was applied, dealloying time was 500s, and porous silver modified layer was obtained.

[0058] S2. Prepare a platinum-porous silver composite electrode. First, prepare a platinum electrodeposition solution, the specific composition of which is: 1mM chloroplatinic acid, 0.01g / mL potassium nitrate and 0.02g / mL polyvinyl pyrrolidone. Then, use porous silver as the working electrode, Pt electrode as the counter electrode, and Ag / AgCl electrode as the reference electrode, immerse in the platinum electrodeposition solution, and continuously deposit for 25s at a constant potential of -0.5V with a stirring speed of 300rpm. Then rinse with deionized water and dry at 60°C to obtain a platinum-porous silver composite electrode.

[0059] The platinum-porous silver composite electrode prepared as above is used as the working electrode 1, silver-silver chloride is modified on the surface of the coplanar reference electrode 2, and platinum is modified on the surfaces of the counter electrode 3 and the counter electrode 4, so as to obtain a standard electrode with four coplanar electrodes, wherein the upper ends of the working electrode 1 and the counter electrode 3 extend with mutually interlaced comb-shaped equidistant interdigitated strips to form an interdigitated electrode structure, the upper end of the reference electrode 2 is located below the interdigitated structure, and can form a three-electrode system with the interdigitated electrode structure; the upper end of the counter electrode 4 is located outside the interdigitated electrode structure, and can form another three-electrode system with it.

[0060] Example 5

[0061] Electrochemical test of tryptophan and methionine using platinum-porous silver composite electrode:

[0062] The platinum-porous silver composite electrode prepared in Example 1 was used as the working electrode, platinum as the counter electrode, and silver-silver chloride as the reference electrode. It was placed in a 0.1 M PBS solution (pH 5.0), and tryptophan and methionine at different concentrations were gradually added. The differential pulse voltammetry curve was measured, and the relationship between the concentration and the oxidation peak current density was calculated to obtain the attached Figure 3 and attached Figure 4 .

[0063] The electrolyte used in the test is a 0.1 M phosphate buffer solution. Phosphate buffer solutions of different pH values ​​are prepared from 0.1 M disodium hydrogen phosphate and 0.1 M sodium dihydrogen phosphate as required.

[0064] Attached Figure 3 It shows that when the concentration range of tryptophan is 0.1-240 μM and the concentration range of methionine is 10-3200 μM, the peak current density increases with the increase of the concentration of the detection object. Therefore, the platinum-porous silver composite electrode prepared in Example 1 has excellent response characteristics to methionine and tryptophan, and can be used for the accurate detection of the above two neurotransmitter molecules.

[0065] Example 6

[0066] Electrochemical stability test of platinum-porous silver composite electrode:

[0067] According to the method described in Example 4, 5 composite electrodes prepared from different batches were placed in a 0.1M PBS (pH=5.0) solution containing methionine and tryptophan to test the differential pulse curve. The test was conducted once a day for 7 consecutive days to monitor the changes in the DPV response current signal to study the long-term stability of the electrochemical detection device. After each test, the composite electrode was cleaned with alcohol and deionized water, dried and stored at room temperature to obtain the attached Figure 5 .

[0068] Attached Figure 5It shows that the electrochemical signals of the two analytes changed very little during the continuous monitoring for one week. It was calculated that for tryptophan and methionine, the response current signals after 7 days decreased by 1.45% and 1.21% respectively compared with the first day. This result shows that the platinum-porous silver composite electrode prepared in Example 4 has good stability.

[0069] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0070] In addition, it should be understood that although this specification is described in accordance with the implementation methods, not every implementation method contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should take the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art. The technical details not described in detail in the present invention can be implemented by any prior art in the art. In particular, all technical features not described in detail in the present invention can be implemented by any prior art.

Claims

1. Application of a platinum-porous silver composite electrode in the detection of neurotransmitter molecules, characterized in that: The preparation method of the platinum-porous silver composite electrode comprises the following steps: S1. Depositing a silver-tin alloy layer on the surface of the composite electrode substrate by an electrodeposition method, and obtaining a porous silver layer by a constant potential dealloying method; S2, using porous silver as a substrate to in-situ modify metal platinum on its surface to prepare a platinum-porous silver composite electrode; The electrodeposition method is specifically as follows: a three-electrode system is used, the counter electrode is a platinum sheet, the reference electrode is an Ag / AgCl electrode, the composite electrode is used as the working electrode, and the electrodeposition reaction is carried out by immersing the composite electrode in a silver-tin solution, and the current density is set to 10-20 mA·cm -2 , stirring is required during the electrodeposition process, and the stirring speed is 500~600rpm; In step S1, the silver-tin solution is composed of: 20-30 g / L silver methanesulfonate, 30-40 g / L tin methanesulfonate, 30-50 g / L pyrophosphate, and 30-50 g / L EDTA; The platinum-porous silver composite electrode can realize the simultaneous detection of trace tryptophan and methionine.

2. The use of a platinum-porous silver composite electrode in the detection of neurotransmitter molecules according to claim 1, characterized in that: In the step S1, the dealloying method is specifically as follows: a three-electrode system is used, with a composite electrode modified with a silver-tin alloy layer as the working electrode, a counter electrode is a platinum sheet, a reference electrode is an Ag / AgCl electrode, the solution is a 0.8~1.0M sulfuric acid solution, a constant potential method is used, a voltage of 10~20 mV is applied, and the dealloying time is 500~600 s to obtain a porous silver modified layer.

3. The use of a platinum-porous silver composite electrode in the detection of neurotransmitter molecules according to claim 1, characterized in that: In the step S2, the preparation method of the platinum-porous silver composite electrode is specifically as follows: porous silver is used as a working electrode, a Pt electrode is used as a counter electrode, and an Ag / AgCl electrode is used as a reference electrode, and they are immersed in a platinum solution, wherein the composition of the platinum solution is specifically as follows: 1~2mM chloroplatinic acid, 0.01~0.03 g / mL potassium nitrate, and 0.01~0.02 g / mL polyvinyl pyrrolidone; continuous deposition is performed at a constant potential of -0.5 V for 20~30 s, and continuous stirring is required during the deposition process, and the stirring speed is 300~500 rpm, followed by rinsing with deionized water and drying at 60°C to obtain a platinum-porous silver composite electrode.

4. An application of a platinum-porous silver composite electrode as claimed in any one of claims 1 to 3 in the detection of neurotransmitter molecules, wherein four electrodes are arranged on the same plane on the surface of an electrode substrate, namely a working electrode (1), a reference electrode (2), a first pair of electrodes (3) and a second pair of electrodes (4), wherein the upper ends of the working electrode (1) and the first pair of electrodes (3) vertically extend out comb-like equidistant interdigitated strips to form an interdigitated structure, the reference electrode (2) is arranged below the middle of the interdigitated structure, and the second pair of electrodes (4) is located outside the interdigitated structure, the platinum-porous silver composite electrode serves as a working electrode, the surface of the reference electrode (2) is modified with silver-silver chloride, and the surfaces of the first pair of electrodes (3) and the second pair of electrodes (4) are modified with platinum.

5. The use of a platinum-porous silver composite electrode in the detection of neurotransmitter molecules according to claim 4, characterized in that: The composite electrode is based on a metal electrode, including an electrode base and an electrode modification layer. The electrode modification layer is located above the electrode base. The electrode modification layer includes a platinum-porous silver modification layer. Specifically, a silver-tin alloy is deposited on the surface of the electrode base, and a porous silver layer is obtained after dealloying, and then metal platinum particles are modified on the surface.

6. The use of a platinum-porous silver composite electrode in the detection of neurotransmitter molecules according to claim 5, characterized in that: The porous silver has a thickness of 0.01-0.03 mm; the surface of the porous silver is modified with platinum metal particles, which are arranged evenly and densely, and the particle size is 0.5-1.5 μm.

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