Preparation method of photoelectrochemical biosensor based on monatomic bismuth and detection method of fumonisins B1

Abstract

The invention particularly relates to a photoelectrochemical biosensor based on monatomic bismuth and a detection method of fumonisins B1. At present, the detection of the fumonisin B1 has the defects of complex pretreatment and expensive detection equipment. The photoelectrochemical detection sensor is composed of an electrode, a catalytic activity substrate material, an aptamer recognition element and a signal amplification unit, a monatomic bismuth nano-material generates a remarkable photoelectric response signal, and by means of the specific molecular recognition effect of an aptamer and a target object, the photoelectrochemical detection sensor of the fumonisins B1 can be used for detecting the fumonisins B1. The high-selectivity recognition of the fumonisin B1 is realized; meanwhile, MXenes quantum dots are introduced to serve as a signal amplification medium, and light current response is enhanced. Researches show that the integrated sensing platform has excellent performance in the aspects of detection sensitivity, analysis speed and result accuracy, and a novel analysis strategy is provided for mycotoxin detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectrochemical detection, and specifically relates to a photoelectrochemical biosensor based on single-atom bismuth, a method for preparing the sensor, and a method for detecting fumonisin B1 based on the sensor. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Fumonisin B1 (FB1) is a toxic metabolite produced by the fungus Fusarium. It is widely found in cereals such as corn and wheat, as well as in traditional Chinese medicines such as coix seed and their products. Its toxic mechanism involves interference with sphingolipid metabolism and inhibition of ceramide synthase activity. It has been classified as a Class 2B carcinogen by the International Agency for Research on Cancer (IARC), causing acute poisoning in animals, immune system damage, and esophageal cancer in humans. With the increasing global food safety concerns, the development of efficient and sensitive FB1 detection technologies has become a key issue in food science and healthcare. Traditional FB1 detection methods primarily include high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), and enzyme-linked immunosorbent assay (ELISA). While these methods are effective, they require complex pretreatment steps and expensive instrumentation, limiting their application in rapid on-site testing. In this context, photoelectrochemical (PEC) sensors combine the advantages of optical excitation and electrochemical detection, amplifying signals through the transfer of photogenerated charge carriers. They offer high sensitivity, strong anti-interference capabilities, and simple instrumentation. Its innovative separation of photoexcitation and electrical detection effectively eliminates background interference in traditional electrochemical detection, significantly improving sensitivity. Compared to traditional chromatography techniques, PEC sensors combine miniaturization, ease of operation, low equipment cost (no need for large instruments), and on-site detection, providing a breakthrough solution for the precise detection of fumonisin B1. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention provides a photoelectrochemical sensor for detecting fumonisin B1, which achieves high-efficiency and low-cost detection of fumonisin B1 based on optical excitation and electrochemical detection. To achieve the above objectives, the present invention first prepared carbon nitride-based single-atom bismuth nanomaterials through a controllable synthesis strategy, and based on this, constructed a multi-component synergistic photoelectrochemical biosensor. Specifically, the present invention provides the following technical solutions: In the first aspect, a photoelectrochemical biosensor based on single-atom bismuth is provided. The sensor uses an electrode as a matrix, and the surface-modified single-atom bismuth nanomaterial adsorbs an aptamer, and the MXenes quantum dot material is connected through the aptamer.

[0005] The photoelectrochemical biosensor of the present invention modifies the surface of a substrate electrode with a single-atom bismuth nanomaterial. The single-atom bismuth nanomaterial achieves efficient photogenerated carrier separation through its unique d-orbital electronic structure, generating a significant photoelectric response signal. Furthermore, a π-π adsorption interaction occurs between the single-atom bismuth nanomaterial and the aptamer DNA single strand, trapping the aptamer on the electrode surface. MXene quantum dots, acting as a signal amplification medium, enhance the photocurrent signal of the single-atom bismuth substrate through energy resonance transfer and electron transfer.

[0006] The aptamer is a single-stranded DNA with a high affinity for the target to be detected. In one embodiment verified by the present invention, the target to be detected is fumonisin B1, and the base sequence of the aptamer is as follows: 5'-ATA CCA GCT TAT TCA ATT AAT CGC ATT ACC TTA TAC CAG CTT ATT CAATTA CGT CTG CAC ATA CCA GCT TAT TCA ATT AGA TAG TAA GTG CAA TCT- 3' (as shown in SEQ ID NO: 1). When fumonisin B1 appears in the detection environment, it specifically binds to the aptamer, causing the aptamer and MXene quantum dots to desorb from the electrode surface, resulting in a decrease in photocurrent and forming a detection signal. According to the present invention, the change in photocurrent of the sensor is linearly correlated with the fumonisin B1 in the test environment and has good reproducibility and stability.

[0007] Furthermore, the first aspect mentioned above also has the following preferred technical solutions: The electrode is an ITO electrode.

[0008] The type of MXenes in the MXenes quantum dots is Ti3C2, which has the advantage that the metal Ti in the MXenes quantum dots and the phosphate groups in the aptamer can stably connect the MXenes quantum dots to the electrode surface through covalent reaction.

[0009] In a second aspect, a method for preparing the photoelectrochemical biosensor according to the first aspect is provided, comprising the following steps: (1) The dispersion of single-atom bismuth nanomaterials is dropped onto the pretreated electrode surface and dried to obtain Bi SACs / electrode; (2) The aptamer solution was added dropwise to the Bi SACs / electrode surface, reacted under moist conditions, and washed to obtain an aptamer-connected electrode, which was denoted as Apt / Bi SACs / electrode. (3) The MXenes quantum dot dispersion is added dropwise to the surface of the Apt / Bi SACs / electrode, reacted under humid conditions, and washed to obtain an electrode with fixed MXenes quantum dots, which is the above-mentioned sensor.

[0010] The above step (1) has the following preferred implementation methods: The dispersion of the above-mentioned single-atom bismuth nanomaterial has a solid-liquid ratio of 6 mg: 2-10 mL and is ultrasonicated for 0.5-3 hours to make it uniformly dispersed; the applied dosage of the dispersion of the single-atom bismuth nanomaterial is measured according to the area of ​​the electrode surface and is 70-300 μL / cm 2 .

[0011] The drying may be performed by heat radiation drying, a specific example of which is drying by irradiation with an infrared lamp.

[0012] The pretreatment method of the above-mentioned electrode is as follows: the ITO electrode is placed in acetone, 1-4 M NaOH alcohol aqueous solution (V anhydrous ethanol: V secondary water = 1:1-1:6), ultrasonicated in secondary water for 15-60 minutes, then rinsed with secondary water, dried naturally, and set aside.

[0013] With respect to the above-mentioned single-atom bismuth nanomaterial, a feasible embodiment of the present invention further provides a method for preparing the single-atom bismuth nanomaterial, comprising the following steps: adding urea and a bismuth source to an organic solution at a dosage ratio of 400:1-800:1, stirring and mixing uniformly, and then evaporating the organic reagent to obtain a solid, and calcining the dried solid at 500-700°C in an inert atmosphere for 1-3 hours to obtain the single-atom bismuth nanomaterial.

[0014] The above step (2) has the following preferred implementation methods: The concentration of the aptamer solution is 300-1000 nM, and the applied dosage is 70-300 μL / cm according to the area of ​​the electrode surface. 2 .

[0015] The reaction under the above-mentioned humid conditions means that the humidity in the reaction environment is greater than 90%, and further, the humidity is 95-99%; the reaction time is 0.5-3 hours, and the reaction temperature is 36-38°C.

[0016] The above step (3) has the following preferred implementation methods: The concentration of the MXenes quantum dot dispersion is 0.2-1 mg / mL. 2-10 mg of MXenes quantum dots are added to 2-10 mL of deionized water and ultrasonicated for 0.5-3 hours to achieve uniform dispersion. In one embodiment verified by the present invention, a method for preparing the aforementioned MXenes quantum dots is also provided, comprising the following steps: dispersing MXenes powder in 5 M nitric acid, isothermally reacting in an oil bath at 95-105°C for 22-26 hours, cooling to room temperature, pouring the reaction system into 25-35 mL of ice water, and adjusting the solution pH to 7; centrifuging the retained precipitate and redispersing it in 35-45 mL of ultrapure water to obtain a solution; transferring the solution to a stainless steel autoclave and heating it at 155-165°C for 10-14 hours. The cooled solution is dialyzed to obtain a yellow MXenes quantum dot solution. Finally, the MXenes quantum dots are obtained by freeze-drying.

[0017] The “reaction under moist conditions” in step (3) has the same meaning as step (2).

[0018] In a third aspect, a method for detecting fumonisin B1 is provided, comprising the following steps: The photoelectrochemical biosensor described in the first aspect is added to a test solution for incubation, the incubated sensor is used as a working electrode, and the photocurrent signal on the surface of the working electrode is detected by a photoelectrochemical signal detection system.

[0019] During the incubation stage, fumonisin B1 in the test solution will specifically bind to the aptamer on the sensor surface, thereby causing the MXenes quantum dots to desorb from the electrode surface, resulting in a decrease in photocurrent. In one embodiment provided by the present invention, a three-electrode system is used for photoelectrochemical signal detection, with the incubated sensor as the working electrode, a saturated calomel electrode as the reference electrode, a Pt wire as the auxiliary electrode, visible light as the light source, and an applied potential of -0.5-0.5 V. The photocurrent is recorded in the electrode detection solution.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The photoelectrochemical biosensor provided by this invention utilizes the energy resonance transfer and accelerated electron transfer of MXene quantum dots to single-atom bismuth nanomaterials to amplify the photoelectric signal, effectively improving the detection sensitivity of fumonisin B1. Based on validation studies, the photoelectrochemical biosensor has a detection range of 5 pg / mL to 1000 ng / mL for fumonisin B1, with a detection limit of 2.40 pg / mL.

[0021] 2. In addition, the above-mentioned photoelectrochemical biosensor uses an aptamer as a recognition probe and has good recognition specificity for fumonisin B1; based on the same principle, the above-mentioned sensor can replace the aptamer to achieve high-specificity and high-sensitivity detection of other targets to be measured.

[0022] 3. Compared to existing fumonisin B1 detection methods, the detection method provided by this invention achieves miniaturization and lower costs. Requiring only simple surface treatment of the ITO electrode, it enables efficient and sensitive detection of fumonisin B1. Furthermore, the sensor is highly suitable for field sampling, effectively reducing both equipment and storage costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 Schematic diagram of the construction of the photoelectrochemical biosensor of the present invention and the detection principle of fumonisin B1.

[0025] Figure 2 This is a spherical aberration electron microscope image of the single-atom bismuth nanomaterial in Example 1; Figure 3 This is a high-resolution transmission electron microscopy image of MXenes quantum dots in Example 1; Figure 4 is a linear curve of the photocurrent intensity and the logarithmic value of the fumonisin B1 concentration in Example 2; Figure 5 : is a histogram of the detection signal under different interference conditions in Example 2; In the figure, FB1 represents fumonisin B1, OTA represents ochratoxin, TOB represents tobramycin, and OFLX represents levofloxacin; Figure 6 This is the test result of the corn sample in Example 2; Figure 7 This is the test result of the coix seed sample in Example 2. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] In the context of this specification, the word "comprising" is understood to mean "including especially". It should not be interpreted as "consisting only of. . . . "

[0029] Explanation of terms: Room temperature: The range of "room temperature" in the present invention is 20-30°C; Humid conditions: humidity greater than 90%; preferably 95-99%.

[0030] Cleaning solution: A mixed solution consisting of 3-15mM Tris-HCl and 20-60mM KCl, pH 7.4.

[0031] Secondary water: Also known as double-distilled water, distilled water is produced by heating water to boiling, vaporizing it, and then condensing it into a liquid. The water obtained through the first distillation is called primary water, while the water obtained through the second distillation is called secondary water.

[0032] As described in the background technology section, although the existing technology can detect fumonisin B1, it also has some shortcomings, such as the need for sophisticated instruments, cumbersome sample pre-treatment, the need for professional operators, and the disadvantages of low detection sensitivity and weak specificity. Based on this, the present invention constructs a photoelectrochemical biosensor for detecting fumonisin B1. The schematic diagram of the construction and detection of the photoelectrochemical biosensor is shown in FIG. Figure 1 The linear relationship between fumonisin B1 concentration and photocurrent intensity can be used to detect fumonisin B1.

[0033] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0034] Example 1 In this embodiment, a photoelectrochemical biosensor based on single-atom bismuth is provided. The sensor uses an ITO electrode as a substrate, adsorbs an aptamer through a surface-modified single-atom bismuth nanomaterial, and connects MXenes quantum dots through the aptamer.

[0035] The construction method of the above sensor is as follows: (1) Bi SACs / electrode construction: Urea and bismuth source were added to methanol solution at a dosage ratio of 400:1-800:1, stirred and mixed evenly, and then the methanol was evaporated at 70°C and the solid was collected. The dried solid was placed in a tube furnace and calcined at 500-700°C under nitrogen atmosphere for 2 hours to obtain single-atom bismuth nanomaterials ( Figure 2 6 mg of the obtained single-atom bismuth nanomaterial was weighed and added to 5 mL of deionized water, and ultrasonically dispersed for 0.5 h to obtain a single-atom bismuth dispersion.

[0036] Cut the ITO conductive glass into 5×1cm 2 The ITO electrode was ultrasonically treated for 20 minutes with acetone, a 1M NaOH solution in alcohol (V anhydrous ethanol:V secondary water = 1:1), and secondary water, followed by rinsing with secondary water and air-drying. 40 μL of the monoatomic bismuth dispersion was dropwise added to the pretreated ITO electrode surface and dried under infrared light. The prepared electrode was labeled BiSACs / electrode.

[0037] (2) Construction of Apt / Bi SACs / electrode: 40 μL of a solution containing the fumonisin B1 aptamer (sequence shown in SEQ ID NO: 1) was added dropwise to the surface of the Bi SACs / electrode prepared in step (1) above. The mixture was reacted at 37°C under humid conditions for 1 h, and then washed three times to obtain an electrode connected to the aptamer, which was labeled as Apt / Bi SACs / electrode.

[0038] (3) Fixation of MXenes quantum dots: MXenes powder was dispersed in 5 M nitric acid, placed in an oil bath, and reacted at a constant temperature of 100 °C for 24 h. After cooling to room temperature, the solution was poured into 30 mL of ice water and the pH of the solution was adjusted to 7 with NaOH. After centrifugation, the resulting precipitate was redispersed in 40 mL of ultrapure water to obtain a solution. The solution was transferred to a stainless steel autoclave and heated at 160 °C for 12 h. The cooled solution was dialyzed to obtain a yellow MXenes quantum dot solution. Finally, MXenes quantum dots ( Figure 3 3 mg of MXenes quantum dots were weighed and added to 5 mL of deionized water. Ultrasonic dispersion was performed for 0.5 h to obtain a dispersion. 20 μL of the MXenes quantum dot dispersion was dropwise added to the Apt / Bi SACs / electrode surface. The mixture was reacted at 37°C under humid conditions for 1 h. The electrode was then washed three times to obtain an immobilized MXenes quantum dot electrode, labeled as MXenes QDs / Apt / Bi SACs / electrode, which is the aforementioned sensor.

[0039] Example 2 In this embodiment, a method for detecting fumonisin B1 is provided. The method is implemented based on the sensor in Example 1, and the specific steps are as follows: (1) Prepare the electrode detection solution: Prepare a Tris buffer solution with a pH of 5.5-8.5 and a concentration of 5-500 mM using sterile water. Then add 5-500 mM ascorbic acid (AA) to the solution. The resulting solution is the electrode detection solution.

[0040] (2) The sensors prepared in Example 1 were placed in different concentrations of fumonisin B1 solutions and incubated at 37 °C for 2 h to obtain several FB1-incubated MXenes QDs / Apt / Bi SACs / electrodes as working electrodes, saturated calomel electrode as reference electrode, and Pt wire as auxiliary electrode to form a three-electrode system for photoelectrochemical signal detection. An electrochemical workstation was used as the signal acquisition instrument, a 500W xenon lamp was used as the visible light source (with a lens to filter out ultraviolet light), the applied potential was -0.5-0.5 V, the photocurrent was recorded in the electrode detection solution, and the detection study of the analyte was carried out using IT technology.

[0041] (3) Establish a relationship between photocurrent intensity and fumonisin B1 concentration, and use this relationship to detect the fumonisin B1 content in the sample. As the fumonisin B1 content increases, the number of MXenes quantum dots on the electrode surface decreases, thereby reducing the photocurrent. Based on the linear relationship between fumonisin B1 concentration and photocurrent intensity, fumonisin B1 can be detected.

[0042] The detection range of fumonisin B1 detected by the sensor in Example 1 was 5 pg / mL-1000 ng / mL, and the detection limit was 2.40 pg / mL.

[0043] Performance Verification 1. Detection specificity Specificity is an important indicator of photoelectrochemical sensor performance. To investigate the specificity of the constructed sensor, fumonisin B1 (FB1), ochratoxin (OTA), tobramycin (TOB), and levofloxacin (OFLX) were selected as interfering agents to study the specificity of the sensor. The photocurrent changes (ΔI = I2-I1, where I1 is the photocurrent value of the MXenes QDs / Apt / Bi SACs / electrode after incubation with solutions containing different substances, and I2 is the photocurrent value of the MXenes QDs / Apt / Bi SACs / electrode) constructed with different interfering agents were compared. Figure 5 The results showed that the change in the current value of the sensor constructed with the interference was significantly lower than that of fumonisin B1, indicating that the constructed sensor has good specificity.

[0044] 2. Stability and reproducibility Nine FB1-incubated MXenes QDs / Apt / Bi SACs / electrodes were prepared using the method of Example 2, and the photocurrent was measured in a test solution. The relative standard deviation of the photocurrent was 3.12%, demonstrating the good reproducibility of the method. The nine FB1-incubated MXenes QDs / Apt / Bi SACs / electrode sensors were measured continuously for seven cycles, and the photoelectrochemical signal was detected in the test solution. The standard deviation of the photocurrent was 1.86%, demonstrating the good stability of the method.

[0045] 3. Accuracy (1) Corn samples An FB1-incubated MXenes QDs / Apt / Bi SACs / electrode was prepared using the method of Example 2. The test solution was a corn sample treatment solution, and the photocurrent was measured in the test solution. The fumonisin B1 content in the corn samples was calculated using a standard curve and compared with the results from liquid chromatography-mass spectrometry (LC-MS). The specific test results for the corn samples are as follows: Photoelectrochemical detection yielded 230µg / kg for Sample 1, 325µg / kg for Sample 2, 365µg / kg for Sample 3, and 485µg / kg for Sample 4; LC-MS detection yielded 236µg / kg for Sample 1, 325µg / kg for Sample 2, 355µg / kg for Sample 3, and 455µg / kg for Sample 4. The results obtained using this photoelectrochemical biosensor were not significantly different from those obtained using the LC-MS method, demonstrating that this method can rapidly and accurately detect fumonisin B1 in actual corn samples.

[0046] (2) Job's tears samples The above test was repeated using the treated solution of coix seed samples. The content of fumonisin B1 in coix seed samples was calculated using a standard curve and compared with the results of the LC-MS method. The specific test results for the coix seed samples are as follows: the photoelectrochemical detection method determined the content of fumonisin B1 in sample 1 to be 53µg / kg, sample 2 to be 61µg / kg, sample 3 to be 69µg / kg, sample 4 to be 88µg / kg, and sample 5 to be 134µg / kg; the LC-MS method determined the content of fumonisin B1 in sample 1 to be 52µg / kg, sample 2 to be 62µg / kg, sample 3 to be 67µg / kg, sample 4 to be 85µg / kg, and sample 5 to be 135µg / kg. The study found no significant difference between the results obtained using the photoelectrochemical biosensor and the LC-MS method, demonstrating that this method can quickly and accurately detect fumonisin B1 in coix seed samples.

[0047] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A photoelectrochemical biosensor based on single-atom bismuth, characterized in that: The sensor uses an electrode as a matrix, and the surface-modified single-atom bismuth nanomaterial adsorbs the aptamer of fumonisin B1 and connects the MXenes quantum dot material through the aptamer.

2. The photoelectrochemical biosensor according to claim 1, wherein The electrode is an ITO electrode.

3. The photoelectrochemical biosensor according to claim 1, wherein The base sequence of the aptamer is shown in SEQ ID NO:

1.

4. The photoelectrochemical biosensor according to claim 1, wherein The type of MXenes in the MXenes quantum dots is Ti3C2.

5. The method for preparing the photoelectrochemical biosensor according to any one of claims 1 to 4, characterized in that: The steps include: (1) Dropping the dispersion of single-atom bismuth nanomaterials onto the pretreated electrode surface and drying to obtain Bi SACs / electrode; (2) The aptamer solution was added dropwise to the Bi SACs / electrode surface, reacted under moist conditions, and washed to obtain an aptamer-connected electrode, which was denoted as Apt / Bi SACs / electrode. (3) The MXenes quantum dot dispersion is added dropwise to the surface of the Apt / Bi SACs / electrode, reacted under humid conditions, and washed to obtain an electrode with fixed MXenes quantum dots, which is the sensor.

6. The method for preparing the photoelectrochemical biosensor according to claim 5, wherein: In step (1), the dispersion of the single-atom bismuth nanomaterial has a solid-liquid ratio of 6 mg: 2-10 mL and is ultrasonicated for 0.5-3 hours to achieve uniform dispersion; The applied dosage of the dispersion of the single atomic bismuth nanomaterial is measured according to the area of ​​the electrode surface and is 70-300 μL / cm 2 The drying method adopts thermal radiation drying, and further, infrared lamp irradiation drying is adopted.

7. The method for preparing the photoelectrochemical biosensor according to claim 5, wherein: In step (1), the electrode is pretreated as follows: the ITO electrode is sequentially placed in acetone, 1-4M NaOH alcohol aqueous solution, and secondary water for ultrasonic treatment for 15-60 minutes, then rinsed with secondary water, dried naturally, and set aside.

8. The method for preparing the photoelectrochemical biosensor according to claim 5, wherein: In step (2), the concentration of the aptamer solution is 300-1000 nM, and the applied dosage is measured according to the area of ​​the electrode surface, which is 70-300 μL / cm 2 ; The reaction under humid conditions means that the humidity in the reaction environment is greater than 90%, and further, the humidity is 95-99%; the reaction time is 0.5-3 hours, and the reaction temperature is 36-38°C.

9. The method for preparing the photoelectrochemical biosensor according to claim 5, wherein: In step (3), the concentration of the MXenes quantum dot dispersion is 0.2~1 mg / mL.

10. A method for detecting fumonisin B1, characterized in that: The detection method comprises the following steps: The photoelectrochemical biosensor according to any one of claims 1 to 4 is added to the solution to be tested and incubated. The incubated sensor is used as the working electrode, the saturated calomel electrode is used as the reference electrode, the Pt wire is used as the auxiliary electrode, the detection liquid is a Tris buffer solution containing 5-500 mM ascorbic acid, the pH of the Tris buffer solution is 5.5-8.5, the light source is visible light, the applied potential is -0.5-0.5 V, and a three-electrode system is formed to perform photoelectrochemical signal detection.

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