Z-type nano heterojunction photoelectrochemical sensor and preparation method and application thereof

Abstract

The invention relates to the technical field of photoelectrochemical sensors, in particular to a Z-type nanometer heterojunction photoelectrochemical sensor and a preparation method and application thereof.The method comprises the steps that rod-shaped ZnO is deposited on fluorine-doped tin oxide glass subjected to hydrophilic treatment, then ZnIn2S4 nanoflowers are synthesized on the surface of ZnO through a hydrothermal synthesis method to form a ZnO / ZnIn2S4 working electrode, and the ZnO / ZnIn2S4 working electrode is used for preparing the Z-type nanometer heterojunction photoelectrochemical sensor. And finally, forming a three-electrode system with a reference electrode and a counter electrode, and constructing the photoelectrochemical sensor by taking a dopamine phosphate buffer solution as an electrolyte. Due to the construction of the Z-type nano heterojunction, the light absorption efficiency of ZnO is improved, the photon-generated carrier separation efficiency of the heterojunction is remarkably improved, and effective separation of photo-generated electrons and holes is promoted. Under the illumination condition, a large amount of dopamine in the electrolyte is converted into polydopamine on the surface of the ZnO / ZnIn2S4 electrode, a large amount of benzoquinone groups exist in the polydopamine, benzoquinone serves as an effective electron acceptor, the light current intensity is effectively inhibited, and the ZnO / ZnIn2S4 electrode can be used for high-sensitivity detection of the dopamine. The method has the advantages of simple preparation process, high sensitivity, high detection speed, good reproducibility and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectrochemical sensors, and in particular to a photoelectrochemical sensor of a Z-type nanoheterojunction and a preparation method and application thereof. Background Art

[0002] Dopamine (DA) is an important neurotransmitter in living organisms. The normal level of dopamine in biological fluids ensures the normal function of the organism, while in the human body, abnormal dopamine concentrations may lead to pituitary tumors, drug addiction, Parkinson's disease and other malignant diseases. Therefore, real-time monitoring of dopamine in biological fluids is crucial for the early diagnosis of diseases. There are many existing methods for DA detection, including high-performance liquid chromatography-mass spectrometry, capillary electrophoresis and mass spectrometry. However, these methods have the disadvantages of cumbersome operation, slow detection speed and complex instruments. Photoelectrochemical (PEC) sensors are used in the detection of various environmental pollutants and disease markers due to their convenient detection, easy miniaturization, high sensitivity and strong selectivity. Among them, the design and synthesis of PEC sensing materials with excellent photoelectrochemical properties are crucial to improve detection sensitivity.

[0003] Zinc oxide (ZnO) is a common transition metal semiconductor material with the advantages of abundant raw materials, low cost, non-toxicity, and high electron mobility. It is an important photoelectric conversion electrode material. However, single ZnO semiconductors have defects such as wide bandgap, low light utilization, photocorrosion, and fast electron-hole recombination rate, which seriously restrict the application of ZnO in the photoelectric field. Semiconductor heterojunction is a semiconductor complex formed by close contact between two or more semiconductors. The energy band structure of the semiconductor at the interface will intertwine with each other, causing the energy band to bend and generate a built-in electric field, which in turn promotes the rapid transfer of photogenerated electrons and holes at the interface. The formation of a heterojunction can promote the effective separation of photogenerated electrons and holes, thereby effectively improving the photoelectrochemical performance of semiconductor materials. Among them, the Z-type heterojunction can achieve efficient separation of photogenerated electron-hole pairs in space while maximally retaining the reduction and oxidation properties of photogenerated electrons and holes, which can greatly improve the photoelectrocatalytic performance of semiconductor materials, thereby improving the detection sensitivity of photoelectrochemical sensors. Therefore, how to design a more reasonable nanoheterojunction structure to construct a photoelectrochemical sensor for highly sensitive detection of DA in human body fluids is a technical problem that urgently needs to be solved. Summary of the invention

[0004] In view of this, the purpose of the present invention is to propose a Z-type nanoheterojunction photoelectrochemical sensor and a preparation method and application thereof, so as to achieve high-sensitivity detection of DA in human body fluids.

[0005] Based on the above purpose, the present invention provides a method for preparing a Z-type nanoheterojunction photoelectrochemical sensor, wherein the method first deposits rod-shaped ZnO on fluorine-doped tin oxide glass after hydrophilic treatment, and then synthesizes ZnIn on the surface of ZnO by hydrothermal synthesis. 2 S 4 Nanoflowers to form ZnO / ZnIn 2 S 4 The working electrode, the reference electrode and the counter electrode finally form a three-electrode system, and dopamine phosphate buffer is used as the electrolyte to construct a photoelectrochemical sensor.

[0006] Preferably, the preparation method comprises the following steps:

[0007] S1. After cleaning and drying, the fluorine-doped tin oxide glass is placed in an ultraviolet ozone cleaning machine for hydrophilic treatment;

[0008] S2, depositing rod-shaped ZnO on the fluorine-doped tin oxide glass after hydrophilic treatment;

[0009] S3, stirring and dissolving an indium source, a zinc source and a sulfur source in a solvent to prepare a reaction precursor solution, immersing the fluorine-doped tin oxide glass with a rod-shaped ZnO deposited therein and performing a hydrothermal reaction to prepare ZnO / ZnIn 2 S 4 Working electrode;

[0010] S4, ZnO / ZnIn 2 S 4 The working electrode, the reference electrode Ag / AgCl electrode, and the counter electrode Pt wire electrode form a three-electrode system; a xenon lamp is used as the light source, and an AM1.5G+ total reflection filter is used to simulate natural sunlight; dopamine phosphate buffer is used as the electrolyte to construct a photoelectrochemical sensor.

[0011] The fluorine-doped tin oxide (FTO) glass is cut into 0.9-1.1×2.9-3.1 cm 2 .

[0012] The cleaning in S1 is ultrasonic cleaning with acetone, ethanol and deionized water in sequence, the ultrasonic cleaning time is 9 to 11 minutes, and the hydrophilic treatment time is 3 to 5 minutes.

[0013] The rod-shaped ZnO is deposited by a constant current deposition method, and the electrodeposition solution is prepared by dissolving a zinc source and hexamethylenetetramine in a solvent, and the amount ratio of the zinc source, hexamethylenetetramine and the solvent is: (0.3715-0.372) g: (0.175-0.176) g: (249-251) mL. Preferably, the zinc source is zinc nitrate hexahydrate. The solvent is deionized water.

[0014] Immerse the FTO glass in a constant temperature heated electrodeposition solution and control the conductive area to 0.9-1.1×0.9-1.1cm 2 , deposition is completed, cooling, washing and drying are performed.

[0015] In the electrodeposition method, FTO glass is used as the working electrode, Hg / HgCl 2 The reference electrode was Pt wire, the counter electrode was Pt wire, the deposition temperature was 85-90 °C, the current density was 0.00025 A, and the deposition time was 1800 s.

[0016] The dosage ratio of the indium source, zinc source, sulfur source and solvent in S3 is: (25-150) mM: (12.5-75) mM: (50-300) mM: (9-11) mL, the hydrothermal synthesis time is 15-30 min, and the reaction temperature is 149-151° C. Preferably, the stirring time of the reaction precursor solution is 20 min. The indium source is indium chloride tetrahydrate. The zinc source is zinc chloride. The sulfur source is thioacetamide.

[0017] The method for preparing the dopamine phosphate buffer in S4 is as follows: prepare 10 -2 M dopamine phosphate buffer solution was diluted step by step to obtain different concentration gradients (0, 1, 2 to 10×10 -5 Prepare 10 M dopamine PBS solution. -4 M NaCl, KCl, ZnCl 2 , FeCl 3 PBS solution and dissolved in 10 -5 M dopamine PBS solution to obtain + 、Na + 、Zn 2+ , Fe 3+ of 10 - 5 M dopamine solution in PBS.

[0018] The power of the xenon lamp in S4 is 280-320W, and the light intensity is 90-110mW / cm 2 .

[0019] The initial PBS solution used had a concentration of 0.1 M and a pH of 7.4.

[0020] The invention also provides a photoelectrochemical sensor of a Z-shaped nano heterojunction, which is prepared by adopting the preparation method.

[0021] The present invention also provides application of the photoelectrochemical sensor of the Z-shaped nanoheterojunction in dopamine detection.

[0022] The beneficial effects of the present invention are as follows: Compared with the prior art, the ZnO prepared by the electrodeposition method is neatly arranged and has a uniform morphology, and the nano-flower-like ZnIn is hydrothermally synthesized on the surface of ZnO. 2 S 4 The Z-type heterojunction prepared by the present invention improves the light absorption efficiency and photoelectric coupling performance of ZnO, promotes the effective separation of photogenerated electrons and holes, and significantly enhances the photocurrent intensity. 2 S 4 The photocurrent intensities are ZnO and ZnIn 2 S 4 The sensor constructed by the present invention has a simple preparation process, low cost and universality. As the concentration of DA detected increases, the results show that DA increases in ZnO / ZnIn 2 S 4 The electrode surface is converted into polydopamine. There are a large number of benzoquinone groups in polydopamine. The benzoquinone groups act as effective electron acceptors, effectively suppressing the photocurrent intensity. They can be used for highly sensitive detection of dopamine and show a good linear relationship. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 is the scanning electron microscope image of ZnO;

[0025] Figure 2 ZnO / ZnIn with different reaction times 2 S 4 SEM images of

[0026] Figure 3 Different reaction ratios of ZnO / ZnIn 2 S 4 SEM images of

[0027] Figure 4 Different reaction times and reaction ratios of ZnO / ZnIn 2 S 4 Comparison of photocurrent intensity;

[0028] Figure 5 ZnO, ZnIn 2 S 4 and ZnO / ZnIn2 S 4 Comparison of photocurrent intensity;

[0029] Figure 6 It is the linear relationship diagram of the corresponding photocurrent of different concentrations of dopamine;

[0030] Figure 7 To detect the interference resistance of dopamine to different substances by photoelectrochemical method;

[0031] Figure 8 ZnO, ZnIn 2 S 4 and ZnO / ZnIn 2 S 4 XRD pattern of . DETAILED DESCRIPTION

[0032] 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 below in conjunction with specific embodiments.

[0033] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should have the common meanings understood by people with ordinary skills in the field to which the present invention belongs. "Include" or "comprising" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but do not exclude other elements or objects.

[0034] Example 1

[0035] Hydrophilic treatment of fluorine-doped tin oxide (FTO) glass:

[0036] Prepare the cut 1×3cm 2 The FTO glass was ultrasonically cleaned with acetone, ethanol and deionized water for 10 minutes in sequence. The specific method of ultrasonic cleaning was as follows: first, the FTO glass was immersed in acetone and then ultrasonically cleaned for 10 minutes, then the FTO glass was immersed in ethanol and then ultrasonically cleaned for 10 minutes, and finally, the FTO glass was immersed in deionized water and ultrasonically cleaned for 10 minutes, and then dried in a 60°C blast drying oven, and then put into a UV ozone cleaning machine for 5 minutes of hydrophilic treatment.

[0037] Preparation of rod-shaped ZnO:

[0038] 0.3719 g of zinc nitrate hexahydrate and 0.1752 g of hexamethylenetetramine were dissolved in 250 mL of deionized water to prepare an electrodeposition solution. 30 mL of the electrodeposition solution was added to an electrodeposition cell, and the electrodeposition cell was placed in a 90 °C oil bath for preheating for 10 min. FTO glass was used as the working electrode, and the deposition area was controlled to be 1 × 1 cm 2 , Hg / HgCl 2The reference electrode was Pt wire, the counter electrode was Pt wire, the deposition temperature was 85-90 °C, the current density was 0.00025 A, and the deposition time was 1800 s.

[0039] Preparation of ZnO / ZnIn 2 S 4 Working electrode:

[0040] 50 mM indium chloride tetrahydrate, 25 mM zinc chloride, and 100 mM thioacetamide were dissolved in 10 mL of deionized water and stirred for 20 min to prepare a reaction precursor solution;

[0041] The above reaction precursor solution was transferred to the inner lining of a high-pressure reactor, and the FTO glass on which ZnO was deposited was placed therein, and the reaction time was controlled to be 15 min and the reaction temperature was 150°C;

[0042] After the reaction was completed, the mixture was naturally cooled to room temperature, rinsed with deionized water for three times, and dried in a blast drying oven at 55°C to obtain ZnO / ZnIn 2 S 4 Working electrode, ZnO / ZnIn 2 S 4 It is a Z-type nanoheterojunction structure.

[0043] Constructing a photoelectrochemical sensor (based on the application of Z-type nanoheterojunction for the field of photoelectrochemical sensors), specifically:

[0044] Construction of a photoelectrochemical sensor for detecting dopamine (DA):

[0045] Preparation of DA solutions of different concentrations and types: -2 M dopamine phosphate buffer (PBS) solution was diluted step by step to obtain different concentration gradients (0, 1, 2 to 10×10 -5 Prepare 10 M dopamine PBS solution. -4 M NaCl, KCl, ZnCl 2 , FeCl 3 PBS solution and dissolved in 10 -5 M dopamine PBS solution to obtain + 、Na + 、Zn 2+ , Fe 3+ of 10 - 5 The purpose of preparing dopamine PBS solutions with different concentrations is to test the response photocurrent of the sensor at different dopamine concentrations and draw a linear relationship curve. Figure 6 Formulated with 10 -4 M different ions and containing 10 -5M dopamine PBS solution is used for the anti-interference test of the sensor, that is, in the presence of different types of impurity ions, the sensor's detection response to dopamine is still very stable, such as Figure 7 .

[0046] The method for constructing a photoelectrochemical sensor for detecting DA is as follows: 2 S 4 The heterojunction was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the Pt wire electrode was used as the counter electrode, forming a three-electrode system. The xenon lamp light source was 300W and the light intensity was 100mW / cm 2 , with AM1.5G+ total reflection filter to simulate natural sunlight; the electrolyte is selected from DA phosphate buffer solution with a concentration of 0-10μM, and a DA photoelectrochemical sensor is obtained.

[0047] Comparative Example 1

[0048] ZnO / ZnIn 2 S 4 The preparation method of the working electrode is to control the reaction time of the high-pressure reactor to 20 minutes, cool it naturally, rinse it with deionized water, and dry it for use.

[0049] Comparative Example 2

[0050] According to the preparation method of ZnO / ZnIn 2 S 4 The preparation method of the working electrode is to control the reaction time of the high-pressure reactor to 25 minutes, cool it naturally, rinse it with deionized water, and dry it for use.

[0051] Comparative Example 3

[0052] According to the preparation method of ZnO / ZnIn 2 S 4 The preparation method of the working electrode is to control the reaction time of the high-pressure reactor to 30 minutes, cool it naturally, rinse it with deionized water, and dry it for use.

[0053] Comparative Example 4

[0054] According to the preparation method of ZnO / ZnIn 2 S 4 The preparation method of the working electrode is to control the concentrations of the reaction precursors, indium chloride tetrahydrate, zinc chloride and thioacetamide, to be 25 mM, 12.5 mM and 50 mM respectively, and the reaction time to be 25 min. The electrode is cooled naturally, rinsed with deionized water, and dried for later use.

[0055] Comparative Example 5

[0056] ZnO / ZnIn 2 S 4The preparation method of the working electrode is to control the concentrations of the reaction precursors, indium chloride tetrahydrate, zinc chloride and thioacetamide, to be 50 mM, 25 mM and 100 mM respectively, and the reaction time to be 25 min. The electrode is cooled naturally, rinsed with deionized water, and dried for later use.

[0057] Comparative Example 6

[0058] According to the preparation method of ZnO / ZnIn 2 S 4 The preparation method of the working electrode is to control the concentrations of the reaction precursors, indium chloride tetrahydrate, zinc chloride and thioacetamide, to be 100 mM, 50 mM and 200 mM respectively, and the reaction time to be 25 min. The electrode is cooled naturally, rinsed with deionized water, and dried for later use.

[0059] Comparative Example 7

[0060] According to the preparation method of ZnO / ZnIn 2 S 4 The preparation method of the working electrode is to control the concentrations of the reaction precursors, indium chloride tetrahydrate, zinc chloride and thioacetamide, to be 150 mM, 75 mM and 300 mM respectively, and the reaction time to be 25 min. The electrode is cooled naturally, rinsed with deionized water, and dried for later use.

[0061] The final products prepared in Example 1 and Comparative Examples 1 to 7 were subjected to scanning electron microscopy (SEM) testing, and the results were as follows:

[0062] The SEM image of the ZnO rod prepared by electrodeposition for 1800s in Example 1 is as follows Figure 1 As shown by Figure 1 The analysis shows that the rod-shaped ZnO prepared by electrodeposition for 1800s has a relatively uniform morphology. From the SEM image, it can be directly observed that the rod-shaped ZnO particle size is about 1 to 2 μm long and has a uniform size, which is beneficial to ZnIn 2 S 4 Subsequent loads.

[0063] Example 1 and Comparative Examples 1 to 3 correspond to ZnIn loaded with different reaction times on the ZnO substrate. 2 S 4 , SEM pictures are as follows Figure 2 As shown in the photocurrent comparison diagram Figure 4 As shown in a. Figure 2 Figures a to d correspond to ZnO / ZnIn prepared with reaction times of 15 min, 20 min, 25 min, and 30 min, respectively. 2 S 4 SEM images, combined Figure 2 and Figure 4 From the analysis, we can know that: Figure 2 a, ZnIn 2 S4 The morphology is closer to two-dimensional nanosheets or microspheres based on nanosheets, showing irregular morphology. The irregular morphology may be unfavorable for the transfer and transmission of electrons. Figure 2 b~ Figure 2 d, ZnIn 2 S 4 The morphology is closer to the three-dimensional nanoflower. Compared with the two-dimensional structure, the three-dimensional ZnIn 2 S 4 It has a larger specific surface area and more active sites. Figure 2 c, the hydrothermal synthesis time of ZnIn was 25 min. 2 S 4 The specifications and morphology are uniform, nano-flower-shaped, and have clear layers, which is beneficial to the transfer and transmission of electrons. Figure 4 a shows that ZnO / ZnIn prepared by hydrothermal reaction on ZnO surface for 25 min 2 S 4 The corresponding photocurrent value is the largest, and the hydrothermal reaction time is further extended to prepare ZnO / ZnIn 2 S 4 The electrode photocurrent decreases instead. It is speculated that when the hydrothermal reaction time exceeds 25 min, the ZnIn 2 S 4 Too many nanoflowers reduce the conductivity of the electrode and block the ZnO electrode material from absorbing light, reducing the number of photogenerated electrons and holes.

[0064] Comparative Examples 4 to 7 correspond to ZnIn with different reaction precursor concentrations loaded on the ZnO substrate. 2 S 4 , SEM pictures are as follows Figure 3 As shown in the photocurrent comparison diagram Figure 4 As shown in b. Figure 2 Figures a to d correspond to the ZnO / ZnIn prepared by the reaction precursor solution concentrations described in Examples 4 to 7, respectively. 2 S 4 SEM images, combined Figure 3 and Figure 4 b Analysis shows that when the hydrothermal synthesis time is 25 min, the ZnIn prepared by different reaction precursor solution concentrations 2 S 4 The morphology of ZnIn in Figures a to d is close to that of three-dimensional nanoflowers. 2 S 4 The nanoflowers gradually become layered, making ZnIn 2 S 4 It has a larger specific surface area and more active sites, which increases the Z-type heterojunction ZnO / ZnIn 2 S 4The photocatalytic performance of the photocurrent gradually increases. Figure 4 b shows the ZnO / ZnIn described in Comparative Example 6 2 S 4 The photocurrent value of the electrode is the largest, and the concentration of the reaction precursor solution is further increased to prepare ZnO / ZnIn 2 S 4 The electrode is reduced instead. It is speculated that when the concentration of the reaction precursor solution exceeds the concentration described in Comparative Example 6, the ZnIn loaded on the ZnO surface 2 S 4 Too many nanoflowers reduce the conductivity of the electrode and block the ZnO electrode material from absorbing light, reducing the number of photogenerated electrons and holes.

[0065] Figure 5 This is the photocurrent intensity diagram corresponding to different electrode materials, Z-type heterojunction ZnO / ZnIn 2 S 4 The working electrode produced has the highest photocurrent, with intensities of ZnO and ZnIn respectively. 2 S 4 This makes it possible to detect DA with high sensitivity.

[0066] Figure 6 It is the linear relationship between the photocurrent intensity and different concentrations of DA. The detection photocurrent of the constructed DA photoelectrochemical sensor shows a good linear relationship with different concentrations of DA. With the continuous increase of DA concentration, the polydopamine generated under light conditions gradually increases. There are a large number of benzoquinone groups in polydopamine. Benzoquinone acts as an electron acceptor, which makes the photocurrent gradually decrease.

[0067] Figure 7 The influence of metal ions with different valence states on DA photoelectrochemical sensors in the environment of DA detection is Figure 7 It can be seen from the current corresponding to the bar graph in that the constructed DA photoelectrochemical sensor has good anti-interference ability.

[0068] Figure 8 This is the XRD pattern of the synthesized electrode material, which verifies the Z-type heterojunction ZnO / ZnIn 2 S 4 successful synthesis.

[0069] Those skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a Z-type nanoheterojunction photoelectrochemical sensor, characterized in that: The method comprises the following steps: firstly, rod-shaped ZnO is deposited on fluorine-doped tin oxide glass after hydrophilic treatment; then, ZnIn2S4 nanoflowers are synthesized on the ZnO surface by a hydrothermal synthesis method to form a ZnO / ZnIn2S4 working electrode; finally, a three-electrode system is formed with a reference electrode and a counter electrode, and a dopamine phosphate buffer is used as an electrolyte to construct a photoelectrochemical sensor.

2. The method for preparing the Z-type nanoheterojunction photoelectrochemical sensor according to claim 1, characterized in that: The steps include: S1. After cleaning and drying, the fluorine-doped tin oxide glass is placed in an ultraviolet ozone cleaning machine for hydrophilic treatment; S2, depositing rod-shaped ZnO on the fluorine-doped tin oxide glass after hydrophilic treatment; S3, stirring and dissolving an indium source, a zinc source and a sulfur source in a solvent to prepare a reaction precursor solution, immersing the fluorine-doped tin oxide glass with deposited rod-shaped ZnO therein and performing a hydrothermal reaction to prepare a ZnO / ZnIn2S4 working electrode; S4. The ZnO / ZnIn2S4 working electrode, the reference electrode Ag / AgCl electrode, and the counter electrode Pt wire electrode are used to form a three-electrode system; a xenon lamp is used as the light source, and an AM1.5G+ total reflection filter is used to simulate natural sunlight; dopamine phosphate buffer is used as the electrolyte to construct a photoelectrochemical sensor.

3. The method for preparing the Z-type nanoheterojunction photoelectrochemical sensor according to claim 2, characterized in that: The cleaning in S1 is ultrasonic cleaning with acetone, ethanol and deionized water in sequence, the ultrasonic cleaning time is 9 to 11 minutes, and the hydrophilic treatment time is 3 to 5 minutes.

4. The method for preparing the photoelectrochemical sensor of Z-type nanoheterojunction according to claim 1 or 2, characterized in that: The rod-shaped ZnO is deposited by a constant current deposition method. The electroplating solution is prepared by dissolving a zinc source and hexamethylenetetramine in a solvent. The dosage ratio of the zinc source, hexamethylenetetramine and the solvent is (0.3715-0.372) g: (0.175-0.176) g: (249-251) mL.

5. The method for preparing the Z-type nanoheterojunction photoelectrochemical sensor according to claim 4, characterized in that: In the electrodeposition method, FTO glass is used as the working electrode, Hg / HgCl2 is used as the reference electrode, Pt wire is used as the counter electrode, the deposition temperature is 85-90° C., the current density is 0.00025 A, and the deposition time is 1800 s.

6. The method for preparing the Z-type nanoheterojunction photoelectrochemical sensor according to claim 2, characterized in that: The dosage ratio of the indium source, zinc source, sulfur source and solvent in S3 is: (25-150) mM: (12.5-75) mM: (50-300) mM: (9-11) mL, the hydrothermal synthesis time is 15-30 min, and the reaction temperature is 149-151° C.

7. The method for preparing the Z-type nanoheterojunction photoelectrochemical sensor according to claim 2, characterized in that: The method for preparing the dopamine phosphate buffer in S4 is as follows: prepare 10 -2 M dopamine phosphate buffer solution was diluted step by step to obtain dopamine PBS solutions with different concentration gradients. -4 M NaCl, KCl, ZnCl2, FeCl3 in PBS and dissolved in 10 -5 M dopamine PBS solution to obtain + 、Na + 、Zn 2+ , Fe 3+ of 10 -5 M dopamine solution in PBS.

8. The method for preparing the Z-type nanoheterojunction photoelectrochemical sensor according to claim 2, characterized in that: The power of the xenon lamp in S4 is 280-320W, and the light intensity is 90-110mW / cm 2 .

9. A Z-type nanoheterojunction photoelectrochemical sensor, characterized in that: The method is prepared by any one of claims 1 to 8.

10. Use of the photoelectrochemical sensor of the Z-type nanoheterojunction according to claim 9 in dopamine detection.

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