Electrochemical sensor for simultaneously detecting dopamine and uric acid and preparation method thereof

Abstract

The invention discloses an electrochemical sensor for simultaneously detecting dopamine and uric acid and a preparation method thereof, and the method comprises the following steps: a, forming a basic working electrode, a counter electrode and a reference electrode on a substrate, and preparing a three-dimensional titanium nitride-reduced graphene oxide porous aerogel electrode on the basic working electrode; and b, synthesizing a titanium nitride-reduced graphene oxide-cobalt sulfide electrode on the basis of the porous aerogel electrode, and taking the titanium nitride-reduced graphene oxide-cobalt sulfide electrode as a working electrode to complete the preparation of the electrochemical sensor. According to the electrochemical sensor, a three-electrode system is adopted, a carbon electrode serves as a counter electrode, Ag / AgCl serves as a reference electrode, a titanium nitride-reduced graphene oxide composite nanostructure is adopted for modifying a working electrode, and cobalt sulfide is prepared through electro-deposition so as to enhance the detection performance. The method is high in sensitivity, low in cost, easy to operate and suitable for medical diagnosis, biomedical research and personal health monitoring.

Description

Technical Field

[0001] The invention relates to an electrochemical sensor based on a screen-printed electrode and a preparation method thereof, belonging to the technical field of biological detection equipment. Background Art

[0002] In recent years, breakthroughs in flexible bioelectronics have driven the rapid development of wearable sweat monitoring devices, providing innovative technical means for real-time tracking of human physiological and pathological information. As an important biological fluid sample, sweat contains key biomarkers such as uric acid (UA), dopamine (DA) and pH value, and their concentration changes are closely related to human metabolic regulation, nerve conduction and disease progression. Specifically: (1) Dopamine is a key neurotransmitter in the central nervous system, and its abnormal concentration is significantly correlated with neurodegenerative diseases such as Parkinson's disease and schizophrenia; (2) Uric acid is not only the end product of purine metabolism, but has also been found to have important physiological functions such as regulating oxidative stress and protecting dopaminergic neurons. Its metabolic imbalance can cause clinical symptoms such as gout and cardiovascular disease. It is worth noting that studies have confirmed that the neuroprotective effect of uric acid is in a dynamic equilibrium relationship with dopamine metabolism, so synchronous monitoring of the concentration changes of the two has important clinical value for the early diagnosis and disease course monitoring of neurodegenerative diseases.

[0003] Current biomarker detection technologies, such as chromatography, fluorescence spectroscopy, and surface-enhanced Raman scattering, offer high accuracy, but they often suffer from technical bottlenecks such as bulky instruments, complex pre-processing, and long detection cycles, making them difficult to meet the portability requirements of wearable point-of-care (POCT) testing. In contrast, electrochemical sensing technology, with its advantages of high sensitivity, rapid response, and miniaturization, demonstrates significant potential for application in the biosensing field.

[0004] However, existing electrochemical sensors still face technical difficulties in the simultaneous detection of multiple biomarkers: (1) There is a significant concentration difference of about three orders of magnitude between dopamine (0.25-1.25 μM) and uric acid (200-500 μM) in biological fluids, which can easily lead to signal masking effects; (2) The oxidation potentials of the two on conventional electrodes overlap significantly, with ΔE < 50 mV, causing serious electrochemical interference. Therefore, a highly selective and sensitive electrochemical sensor that can simultaneously detect these two biomarkers is crucial for early disease diagnosis and health monitoring. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: an electrochemical sensor is needed that can simultaneously detect dopamine and uric acid with high sensitivity, good reproducibility and simple operation.

[0006] The present invention further aims to solve the following technical problems: A method for preparing an electrochemical sensor is needed, wherein the prepared sensor can simultaneously detect dopamine and uric acid with high sensitivity, good reproducibility and simple operation.

[0007] In order to solve the above technical problems, the present invention provides an electrochemical sensor for simultaneously detecting dopamine and uric acid, comprising: a working electrode WE, a counter electrode CE and a reference electrode RE. The working electrode, the reference electrode and the counter electrode constitute an electrochemical sensor for simultaneously detecting dopamine and uric acid; the base electrode of the working electrode is a screen-printed electrode, and the surface of the working electrode of the screen-printed electrode is modified with a ternary titanium nitride-reduced graphene oxide-cobalt sulfide composite electrode; the reference electrode is an Ag / AgCl electrode, and the counter electrode is a carbon electrode.

[0008] A method for preparing an electrochemical sensor for simultaneously detecting dopamine and uric acid comprises the following steps: a. forming a basic working electrode, a counter electrode, and a reference electrode on a substrate, and preparing a three-dimensional titanium nitride-reduced graphene oxide porous aerogel electrode on the basic working electrode; b. Based on the porous aerogel electrode, a titanium nitride-reduced graphene oxide-cobalt sulfide electrode is synthesized and used as a working electrode to complete the preparation of an electrochemical sensor.

[0009] In the aforementioned method for preparing an electrochemical sensor for simultaneously detecting dopamine and uric acid, in step a, the steps of preparing the three-dimensional titanium nitride-reduced graphene oxide porous aerogel electrode include: (1) Graphene oxide (GO) solution and Ti3C2Tx suspension were mixed for a set time with the aid of a numerically controlled ultrasonic cleaner to form a uniform suspension; the concentration of the graphene oxide solution was 1.5-2 mg / mL, and the concentration of the Ti3C2Tx suspension was 1.5-2 mg / mL; the mass ratio of the graphene oxide solution to the Ti3C2Tx suspension was 7:3; (2) transferring the suspension into a stainless steel autoclave lined with polytetrafluoroethylene (Teflon), placing the autoclave in a constant temperature heating device, and heating at 90°C-100°C for 22-24 hours to form a hydrogel with a three-dimensional porous network structure; (3) Performing dialysis treatment on the generated three-dimensional hydrogel; (4) The three-dimensional hydrogel after dialysis is dehydrated by freeze drying technology, and the obtained dry product is a material having a three-dimensional titanium nitride-reduced graphene oxide composite nanostructure; (5) Using the three-dimensional titanium nitride-reduced graphene oxide composite nanomaterial obtained in step (4), a composite nanostructure suspension with a concentration of 1.8-2 mg / mL is prepared, and the surface of the working electrode is modified using the composite nanostructure suspension to prepare a base electrode for electrochemical sensing.

[0010] In the aforementioned method for preparing an electrochemical sensor for simultaneously detecting dopamine and uric acid, in step (3), ultrapure water is used as a medium and dialysis is performed continuously for about 2-3 days.

[0011] The aforementioned method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid, in step b, the step of synthesizing a titanium nitride-reduced graphene oxide-cobalt sulfide electrode comprises: (21) Prepare an electroplating electrolyte by weighing equal molar amounts of cobalt nitrate Co(NO3)2 and thiourea CH4N2S; dissolving them in a set volume of deionized water and mixing them evenly. The molar amount to set volume ratio is 5 mmol / 50 mL; and then using deionized water to make the volume 16-20 times of the original volume. (22) pouring the prepared electrolyte into the electrodeposition tank, and connecting the pre-prepared titanium nitride-reduced graphene oxide substrate electrode as the working electrode to the electrochemical workstation; performing electrodeposition by cyclic voltammetry; after the electrodeposition is completed, taking out the titanium nitride-reduced graphene oxide electrode on which cobalt sulfide has been deposited; (23) The titanium nitride-reduced graphene oxide-cobalt sulfide electrode prepared in step (22) is thoroughly cleaned and dried using deionized water.

[0012] In the aforementioned method for preparing an electrochemical sensor for simultaneously detecting dopamine and uric acid, in step (22), the potential scanning range is set to -2.0 V to -0.5 V, and the scanning rate is 80 mV s -1 , a total of 10 complete deposition cycles were performed.

[0013] In the aforementioned method for preparing an electrochemical sensor for simultaneously detecting dopamine and uric acid, in step (23), multiple immersion washing or ultrasonic-assisted cleaning is performed. After cleaning, the electrode is placed in a vacuum drying oven for drying.

[0014] The aforementioned method for preparing an electrochemical sensor for simultaneously detecting dopamine and uric acid further comprises: Step c: performing electrochemical testing on the electrochemical sensor using differential pulse voltammetry to generate a working curve of the electrochemical sensor.

[0015] In the aforementioned method for preparing an electrochemical sensor for simultaneously detecting dopamine and uric acid, in step c, the step of generating a working curve of the electrochemical sensor comprises: The working electrode was electrochemically tested using differential pulse voltammetry at room temperature. The test medium was a phosphate buffer solution with a concentration of 0.5-1 M and a pH value adjusted to 7.0-7.4.

[0016] The aforementioned method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid, in step (42), the test amplitude is 0.05 V, the pulse period is 0.5 s, the pulse width is 0.05 s, the scan rate is 50-100 mV / s, and the sensitivity is 10 -3 A / V; draw the electrochemical working curve based on the relationship between the obtained current response and the concentration of dopamine and uric acid standard solutions.

[0017] The aforementioned method for preparing an electrochemical sensor for simultaneously detecting dopamine and uric acid changes the concentrations of the two solutions of dopamine and uric acid to be detected, and performs separate detections on the two solutions.

[0018] Beneficial results achieved by the present invention: The electrochemical sensor, based on a three-dimensional porous titanium nitride-reduced graphene oxide-cobalt sulfide electrode design, leverages the excellent conductivity and porous structure of titanium nitride and reduced graphene oxide to improve electron transfer efficiency and enhance signal recognition capabilities. Furthermore, electrodeposition of cobalt sulfide increases the specific surface area and conductivity of the electrode, optimizing the electron transfer pathway and enabling the sensor to effectively distinguish between dopamine and uric acid, improving detection accuracy and enhancing performance. Compared to existing electrochemical sensors, this sensor offers higher sensitivity, lower cost, and easier operation, making it suitable for medical diagnosis, biomedical research, and personal health monitoring.

[0019] The electrochemical sensor prepared by the method of the present invention not only avoids overlap of dopamine and uric acid peak potentials but also improves the sensitivity, reproducibility, and stability of existing methods. Compared with existing electrochemical sensor methods, it has the advantages of a wide linear range, low detection limit, simple operation, and fast detection speed, enabling simultaneous determination of dopamine and uric acid in a short period of time. It not only enables the determination of a single substance in the presence of high concentrations of coexisting substances, but also allows for the simultaneous detection of dopamine and uric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the electrochemical sensor electrodes for simultaneously detecting dopamine and uric acid in Example 1 of the present invention; Figure 2 is a cyclic voltammogram of cobalt sulfide electrodeposition in Example 1 of the present invention; Figure 3 is a SEM image at 500 nm of the titanium nitride-reduced graphene oxide-cobalt sulfide composite material in Example 2 of the present invention; Figure 4is a differential pulse curve diagram of different dopamine concentrations in Example 3 of the present invention; Figure 5 is a linear fitting graph of dopamine concentration and current in Example 3 of the present invention; Figure 6 is a differential pulse curve diagram of different concentrations of uric acid in Example 3 of the present invention; Figure 7 3 is a linear fitting diagram of uric acid concentration and current in Example 3 of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below with reference to the accompanying drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Example 1

[0022] like Figure 1 An electrochemical sensor for the simultaneous detection of dopamine and uric acid is shown, comprising a working electrode (WE), a counter electrode (CE), and a reference electrode (RE). The working electrode's base electrode is a screen-printed electrode, and the surface of the screen-printed working electrode is modified with a ternary titanium nitride-reduced graphene oxide-cobalt sulfide composite electrode. The working electrode, the reference electrode, and the counter electrode form an electrochemical sensor for the simultaneous detection of dopamine and uric acid. The reference electrode is an Ag / AgCl electrode, and the counter electrode is a carbon electrode.

[0023] A method for preparing an electrochemical sensor for simultaneously detecting dopamine and uric acid comprises the following steps: a. forming a basic working electrode, a counter electrode, and a reference electrode on a substrate, and preparing a three-dimensional titanium nitride-reduced graphene oxide porous aerogel electrode on the basic working electrode; b. Based on the porous aerogel electrode, a titanium nitride-reduced graphene oxide-cobalt sulfide electrode is synthesized as a working electrode to complete the preparation of the electrochemical sensor.

[0024] In step a, the steps of preparing the three-dimensional titanium nitride-reduced graphene oxide porous aerogel electrode include: Take graphene oxide (GO) solution and Ti3C2T x The (MXene) suspension is mixed with the aid of a numerically controlled ultrasonic cleaner for a set time, such as 2 hours, to form a uniform suspension; the concentration of the graphene oxide solution is 1.5-2 mg / mL, and the concentration of the Ti3C2Tx suspension is 1.5-2 mg / mL; the mass ratio of the graphene oxide solution to the Ti3C2Tx suspension is 7:3.

[0025] The suspension was transferred into a stainless steel autoclave lined with polytetrafluoroethylene (Teflon), and the autoclave was placed in a constant temperature heating device and heated at 90°C-100°C for 22-24 hours to form a hydrogel with a three-dimensional porous network structure; (3) To further improve the purity and stability of the material, the generated three-dimensional hydrogel is dialyzed. Ultrapure water is used as the medium and the dialysis is continued for about 2-3 days. This process can effectively remove the unreacted ions and other small molecular impurities remaining in the hydrogel, ensuring that the electrochemical and physical properties of the material in subsequent applications are not interfered with by impurities; (4) The three-dimensional hydrogel after dialysis was dehydrated using freeze-drying technology, and the resulting dry product was a material with a three-dimensional titanium nitride-reduced graphene oxide composite nanostructure. Freeze-drying can prevent the aggregation of nanosheets and retain the original porous network structure to the greatest extent.

[0026] (5) Using the three-dimensional titanium nitride-reduced graphene oxide composite nanomaterial obtained in step (4), a composite nanostructure suspension with a concentration of 1.8-2 mg / mL is prepared, and the surface of the working electrode is modified using the composite nanostructure suspension to prepare a base electrode for electrochemical sensing.

[0027] Using screen printing technology, 5.0-10.0 µL of the suspension is precisely dripped onto the working electrode area. After the droplets evaporate and dry naturally at room temperature, a uniform modified layer is formed, thereby preparing a base electrode for electrochemical sensing with stable performance and rapid mass transfer.

[0028] In step b, the step of synthesizing a titanium nitride-reduced graphene oxide-cobalt sulfide electrode comprises: (21) Prepare the electroplating electrolyte by accurately weighing 5 mmol of cobalt nitrate (Co(NO3)2) and 5 mmol of thiourea (CH4N2S). Dissolve each of the two reagents in 50 mL of deionized water and mix thoroughly. Use deionized water to adjust the volume to 800-1000 mL. The entire process should be carried out at room temperature, ensuring that the reagents are completely dissolved and mixed thoroughly. The composition and concentration of the above electrolyte are designed to achieve efficient subsequent electroplating of cobalt sulfide while ensuring the repeatability and stability of the electroplating process.

[0029] (22) The prepared electrolyte was poured into the electrodeposition tank, and the pre-prepared titanium nitride-reduced graphene oxide substrate electrode was connected to the electrochemical workstation as the working electrode; then, cyclic voltammetry (CV) was used for electrodeposition.

[0030] The specific parameters were set as follows: the potential scanning range was set to -2.0 V to -0.5 V, and the scanning rate was set to 80 mV s-1 , a total of 10 complete deposition cycles were performed to achieve efficient cobalt sulfide deposition. During this process, thiourea partially decomposed under negative potential conditions, releasing sulfur ions ( ), and the cobalt ions in the solution ( ) reacts to form cobalt sulfide, which is deposited on the electrode surface. Through multiple cyclic scanning, a dense and uniform cobalt sulfide deposition layer can be formed on the electrode surface, significantly improving the electrode's catalytic activity and conductivity.

[0031] After the electrodeposition is completed, the titanium nitride-reduced graphene oxide electrode on which cobalt sulfide has been deposited is taken out.

[0032] (23) To ensure that there is no residual electrolyte and unreacted substances on the electrode surface, the titanium nitride-reduced graphene oxide-cobalt sulfide electrode prepared in step (22) is thoroughly cleaned with deionized water. The cleaning process uses multiple immersion washings or ultrasonic-assisted cleaning to completely remove impurities. After cleaning, the electrode is placed in a vacuum drying oven for drying.

[0033] The cyclic voltammetry curve of electrodeposited cobalt sulfide is as follows Figure 2 As shown, the current decreases overall as the potential is swept from -2.0 V to -0.5 V. Initially, the current is high near -2.0 V, but gradually decreases as the scan moves in the positive direction. This indicates a strong reduction reaction initially, which gradually weakens as the potential increases. Over the subsequent cycles, the deposition rate slows, the current peak decreases, and the curve gradually flattens. This phenomenon is the result of the growing deposit layer gradually hindering electron transfer.

[0034] The SEM image of the prepared titanium nitride-reduced graphene oxide-cobalt sulfide composite material is as follows: Figure 3 As shown in the figure, a large number of nanoparticles with a particle size of tens of nanometers can be seen, which are densely and relatively evenly distributed, indicating that the material The particle loading is good; the surface of the entire composite structure is rough, and there is a certain nanoscale pore structure, which is conducive to increasing the specific surface area and improving the density of electrochemical active sites of the material; the image shows a "nanoparticle-two-dimensional sheet" composite structure, which shows that TiN provides a conductive skeleton and rGO enhances electronic conduction and structural support. This provides a synergistic advantage of electrochemically active sites. Example 2

[0035] On the basis of Example 1, the following further aspects are included: Step c: performing electrochemical testing on the electrochemical sensor using differential pulse voltammetry to generate a working curve of the electrochemical sensor.

[0036] In step c, the step of generating a working curve of the electrochemical sensor includes: (41) The titanium nitride, reduced graphene oxide, and cobalt sulfide composite material not only has high electrical conductivity but also has good catalytic activity and can significantly enhance the electrochemical response of dopamine (DA) and uric acid (UA).

[0037] Modified titanium nitride, reduced graphene oxide and cobalt sulfide working electrodes are used as detection electrodes, carbon electrodes are used as counter electrodes, and Ag / AgCl electrodes are used as reference electrodes to ensure the stability and accuracy of the entire electrochemical system.

[0038] (42) The working electrode was electrochemically tested using differential pulse voltammetry (DPV) at room temperature. The test medium was phosphate buffer solution (PBS) with a concentration of 0.5-1 M and a pH value adjusted to 7.0-7.4 to simulate physiological conditions and ensure system stability. The DPV method is widely used in bioanalysis due to its high sensitivity and low background noise. The test parameters were set as follows: amplitude of 0.05 V, pulse period of 0.5 s, pulse width of 0.05 s, scan rate of 50-100 mV / s, and sensitivity of 10 -3 A / V; draw the electrochemical working curve based on the relationship between the obtained current response and the concentration of dopamine and uric acid standard solutions. Example 3

[0039] In step c, dopamine (DA) and uric acid (UA) are measured separately.

[0040] (41) The modified working electrode was a composite material of titanium nitride, reduced graphene oxide, and cobalt sulfide. The counter electrode was a carbon electrode, and the reference electrode was an Ag / AgCl electrode. The electrodes were prepared using screen printing technology to ensure the stability and accuracy of the entire electrochemical system.

[0041] (42) Electrochemical tests of the working electrode were performed using differential pulse voltammetry (DPV) at room temperature. The test medium was phosphate buffer solution (PBS) with a concentration of 1 M and a pH value adjusted to 7.0-7.4 to simulate physiological conditions and ensure system stability. The test parameters were set as follows: amplitude of 0.05 V, pulse period of 0.5 s, pulse width of 0.05 s, scan rate of 50-100 mV / s, and sensitivity of 10 -3 A / V (ampere / volt).

[0042] The concentrations of the two solutions of dopamine and uric acid to be tested were changed, and the two solutions of dopamine and uric acid were tested separately. The results were as follows: Figure 4-7 shown by Figure 4 and Figure 6As shown, when the two molecules are detected separately, their peak current positions appear at 0.04V and 0.14V respectively, and when the molecular concentration is changed, the current signals of the two molecules increase in a positive correlation trend.

[0043] Further study of the relationship between the concentration of the two molecules and the current signal shows that there is a good linear relationship between the concentration and the current signal, such as Figure 5 and Figure 7 As shown. Figure 5 and Figure 7 As can be seen from the slopes of the linear fit plots of molecular concentration and current for both dopamine (DA) and uric acid (UA), the electrochemical sensor of the present invention has good linear range and sensitivity, with a detection range of 0-600 μmol / L. The detection sensitivity for dopamine is 0.04 μA / μmol / L; the detection sensitivity for uric acid is 0.3 μA / μmol / L within the concentration range of 0-100 μmol / L and 0.05 μA / μmol / L within the concentration range of 100-600 μmol / L.

[0044] Unit description: M (mole per liter): indicates the concentration of the solution, 1 M = 1 mol / L, that is, there is 1 mole of solute per liter of solution; mM (millimolar per liter): 1 mM = 10⁻³mol / L, that is, there is 1 millimole of solute per liter of solution; mL: milliliter; mg / mL: milligrams per milliliter, indicating the concentration of the solution; mmol: millimole; µL: microliter; wt%: weight percent; PBS: Phosphate Buffered Saline.

[0045] The above specific implementation methods are only for illustrating the technical concept and structural features of the present invention, and the purpose is to enable relevant persons familiar with this technology to implement them accordingly. However, the above content does not limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. An electrochemical sensor for simultaneous detection of dopamine and uric acid, characterized in that: A working electrode WE, a counter electrode CE and a reference electrode RE are formed on a base electrode, and the working electrode WE, the counter electrode CE and the reference electrode RE are used to simultaneously detect dopamine and uric acid; the base electrode is a screen-printed electrode, and the working electrode surface of the screen-printed electrode is modified into a ternary titanium nitride-reduced graphene oxide-cobalt sulfide composite electrode; the reference electrode is an Ag / AgCl electrode, and the counter electrode is a carbon electrode.

2. A method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid, characterized in that: The following steps are involved: a. forming a basic working electrode, a counter electrode, and a reference electrode on a substrate, and preparing a three-dimensional titanium nitride-reduced graphene oxide porous aerogel electrode on the basic working electrode; b. Based on the porous aerogel electrode, a titanium nitride-reduced graphene oxide-cobalt sulfide electrode is synthesized and used as a working electrode to complete the preparation of an electrochemical sensor.

3. The method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid according to claim 2, characterized in that: In step a, the steps of preparing the three-dimensional titanium nitride-reduced graphene oxide porous aerogel electrode include: (1) Graphene oxide (GO) solution and Ti3C2Tx suspension were mixed for a set time with the aid of a numerically controlled ultrasonic cleaner to form a uniform suspension; the concentration of the graphene oxide solution was 1.5-2 mg / mL, and the concentration of the Ti3C2Tx suspension was 1.5-2 mg / mL; the mass ratio of the graphene oxide solution to the Ti3C2Tx suspension was 7:3; (2) transferring the suspension into a stainless steel autoclave lined with polytetrafluoroethylene (Teflon), placing the autoclave in a constant temperature heating device, and heating at 90°C-100°C for 22-24 hours to form a hydrogel with a three-dimensional porous network structure; (3) Performing dialysis treatment on the generated three-dimensional hydrogel; (4) The three-dimensional hydrogel after dialysis is dehydrated by freeze drying technology, and the obtained dry product is a material having a three-dimensional titanium nitride-reduced graphene oxide composite nanostructure; (5) Using the three-dimensional titanium nitride-reduced graphene oxide composite nanomaterial obtained in step (4), a composite nanostructure suspension with a concentration of 1.8-2 mg / mL is prepared, and the surface of the working electrode is modified using the composite nanostructure suspension to prepare a base electrode for electrochemical sensing.

4. The method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid according to claim 2, wherein: In step b, the step of synthesizing a titanium nitride-reduced graphene oxide-cobalt sulfide electrode comprises: (21) Prepare an electroplating electrolyte by weighing the same molar number of cobalt nitrate Co(NO3)2 and thiourea CH4N2S; dissolve them in a set volume of deionized water and mix them evenly. The ratio of the molar number to the set volume is 5 mmol / 50 mL; then use deionized water to make the volume 16-20 times of the original volume; (22) Pour the prepared electrolyte into the electrodeposition tank, and connect the pre-prepared titanium nitride-reduced graphene oxide substrate electrode as the working electrode to the electrochemical workstation; perform electrodeposition by cyclic voltammetry; after the electrodeposition is completed, remove the titanium nitride-reduced graphene oxide electrode on which cobalt sulfide has been deposited; (23) The titanium nitride-reduced graphene oxide-cobalt sulfide electrode prepared in step (22) is cleaned and dried using deionized water.

5. The method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid according to claim 2, characterized in that: In step (22), the potential scan range was set from −2.0 V to −0.5 V, and the scan rate was 80 mV s -1 , a total of 10 complete deposition cycles were performed.

6. The method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid according to claim 2, characterized in that: In step (23), multiple immersion washing or ultrasonic-assisted cleaning is performed, and after cleaning, the electrode is placed in a vacuum drying oven for drying.

7. The method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid according to claim 2, further comprising: Step c: performing electrochemical testing on the electrochemical sensor using differential pulse voltammetry to generate a working curve of the electrochemical sensor.

8. The method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid according to claim 7, characterized in that: In step c, the step of generating a working curve of the electrochemical sensor includes: The working electrode was electrochemically tested using differential pulse voltammetry at room temperature. The test medium was a phosphate buffer solution with a concentration of 0.5-1 M and a pH value adjusted to 7.0-7.

4.

9. The method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid according to claim 8, characterized in that: The test amplitude is 0.05 V, the pulse period is 0.5 s, the pulse width is 0.05 s, the scanning rate is 50-100 mV / s, and the sensitivity is 10 -3 A / V; draw the electrochemical working curve based on the relationship between the obtained current response and the concentration of dopamine and uric acid standard solutions.

10. The method for preparing an electrochemical sensor for simultaneous detection of dopamine and uric acid according to claim 9, characterized in that: The concentrations of the two solutions to be tested, dopamine and uric acid, were changed, and the two solutions were tested separately.

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