Preparation method and application of CdS / TiO2 / graphene electrode based on laser direct writing technology

Abstract

The application discloses a CdS / TiO2 / Graphene electrode preparation method based on a laser direct writing technology and application thereof. First, acetylacetone cadmium powder, acetylacetone titanium oxide and polyether sulfone compound are synthesized, laser direct writing is carried out by a nanometer laser action instrument, a CdS / TiO2 / Graphene / ITO electrode is formed, finally, aptamer loaded with aflatoxin B1 is added to the CdS / TiO2 / Graphene / ITO electrode incubated with aflatoxin B1 to assemble a two-electrode system, and then the aflatoxin B1 is tested. The raw material of the application is easy to obtain, the preparation process is simple, and no external voltage is needed in the chemical sensing process. The ratio type sensor has a sensitive response to trace aflatoxin B1, greatly reduces the influence of environmental factors on the sensing process, and has high stability. The application provides a new method for detecting aflatoxin B1, which is high in sensitivity and stable in performance.

Description

Technical Field

[0001] This invention relates to a CdS / TiO2 / Graphene electrode based on laser direct writing technology for ratiometric detection of aflatoxin B1, belonging to the fields of semiconductor nanomaterials and bioanalysis technology. Background Technology

[0002] Aflatoxin B1 (AFB1) is a fungal toxin widely found in plants and various nuts, characterized by its high toxicity and significant harm. Among all known chemical substances, aflatoxin B1 has the highest carcinogenic potential, exhibiting extremely strong hepatotoxicity and carcinogenicity. It was classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) as early as 1993. Therefore, accurate, rapid, and efficient detection of aflatoxin B1 is of great significance for protecting national food safety.

[0003] Currently, the main methods for detecting aflatoxin B1 include instrumental analysis, chemical analysis, and immunological analysis. Instrumental analysis (such as thin-layer chromatography and high-performance liquid chromatography) is a commonly used method for toxin detection. However, while it can provide accurate results, the equipment is expensive, time-consuming, and requires professional operators. Immunological analysis (ELISA) is also widely used in the detection of aflatoxin B1, but its stability, accuracy, and sensitivity are still insufficient due to the susceptibility of enzyme activity to reaction conditions.

[0004] Laser direct writing technology utilizes a laser beam as a heat source to induce localized pyrolysis / carbonization of substrate materials to prepare carbon functional materials. It can prepare graphene-based materials on a large scale at room temperature without any templates, avoiding cumbersome physicochemical processes and simplifying the production method and process of graphene. Laser direct writing technology is characterized by high efficiency and ease of patterning. Furthermore, the electrodes it produces possess advantages such as high electron transfer rates, making it highly promising in the field of electrode construction. For the fabrication of controllable micro / nano structures, laser direct writing technology offers advantages such as portable equipment, simple operation, high stability, and high accuracy, overcoming the shortcomings of existing detection methods and providing a new approach for the rapid, sensitive, and efficient detection of aflatoxin B1. Summary of the Invention

[0005] Based on the above background, the purpose of this invention is to provide a laser-written CdS / TiO2 / Graphene / ITO material with sensitive response for detecting aflatoxin B1 and its preparation method, and to construct a ratiometric dual-electrode system to realize the detection of aflatoxin B1.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a CdS / TiO2 / Graphene electrode based on laser direct writing technology, characterized in that the preparation of the CdS / TiO2 / Graphene electrode by laser direct writing of the composite material is characterized by comprising the following steps:

[0007] Step 1: Preparation of precursor electrode: Immerse cadmium acetylacetone powder, titanium dioxide acetylacetone, and polyethersulfone in DMF solvent, sonicate at room temperature for 30-60 minutes to dissolve the powder, and stir for a certain time to fully mix to obtain precursor solution; Sonicate ITO conductive glass with deionized water, acetone, and anhydrous ethanol for 20 minutes in sequence, and use after drying; Apply tape with two 0.8 cm × 2 cm notches to the conductive surface of ITO electrode, then drop a certain volume of precursor solution onto the conductive surface of ITO electrode, coat it in a spin coater at 1000-3000 rpm for 30-180 seconds, and dry at 80℃ for 1-12 hours to obtain precursor electrode, with the notches marked as region 1 and region 2;

[0008] Step 2: Fabrication of the laser-written composite electrode: The precursor electrode is placed under a nanolaser, and the processing pattern is drawn in the corresponding control software. The scanning speed is set, the laser output power is adjusted, and laser writing is performed. After cooling to room temperature, a CdS / TiO2 / Graphene electrode is obtained. The photoinduced CdS / TiO2 / Graphene electrode is a composite material formed by laser writing of cadmium acetylacetonate, titanium acetylacetonate, and polyethersulfone onto an ITO conductive glass substrate. The specific component ratio is: Cd... 2+ With Ti 4+ The molar ratio is 0.25-1.5, and the mass ratio of cadmium acetylacetonate to polyethersulfone is 0.1-0.6.

[0009] Furthermore, the CdS / TiO2 / Graphene is a composite material formed by cadmium acetylacetonate, titanium acetylacetonate, and polyethersulfone, generated by laser direct writing, with the specific component ratio being: Cd 2+ With Ti 4+ The molar ratio is 0.75-1.25, and the mass ratio of cadmium acetylacetonate to polyethersulfone is 0.3-0.5.

[0010] Furthermore, the volume of the DMF solvent is 10-30 mL.

[0011] Furthermore, in step 1, the cadmium acetylacetone powder, titanium acetylacetone oxide, and polyethersulfone are immersed in the DMF solution and stirred for 1-12 hours.

[0012] Furthermore, the volume of the precursor solution dropped onto the ITO electrode in step 1 is 100-500 μL.

[0013] Furthermore, step 2, which involves setting the pattern to be processed and the corresponding scanning speed and laser output power in the supporting control software of the nanolaser facilitator, includes the following steps:

[0014] Step 2.1: Complete the setting of the processing pattern: Draw a 0.8 cm × 2 cm rectangle corresponding to region 1 and region 2 in the supporting control software of the nano laser processing instrument as the processing pattern;

[0015] Step 2.2: Set the scanning speed: Set the scanning speed to 100-500 mm / s in the control software of the nanolaser instrument;

[0016] Step 2.3: Set the laser output power: Set the maximum laser output power to 20%-40% in the control software of the nano-laser activator.

[0017] This invention also provides a method for preparing a CdS / TiO2 / Graphene electrode based on laser direct writing technology, and a method for detecting aflatoxin B1 using the electrode, characterized in that:

[0018] Step 1: Incubate aflatoxin B1 on the surface of a CdS / TiO2 / Graphene / ITO electrode loaded with aflatoxin B1 nucleic acid aptamers;

[0019] Step 2: Construct a dual-electrode system by loading aflatoxin B1 nucleic acid aptamer and incubating aflatoxin B1 with a CdS / TiO2 / Graphene / ITO electrode and a platinum-modified photocathode, and test the relationship between the power density and potential of the battery anode under illumination in the detection solution.

[0020] Furthermore, step 1 specifically includes:

[0021] Step 1.1: A 2% wt PDDA solution is added dropwise to the working interface of the CdS / TiO2 / Graphene / ITO electrode for incubation, followed by washing with water and drying to obtain a PDDA-loaded CdS / TiO2 / Graphene / ITO electrode;

[0022] Step 1.2: Add 0.5-2 μL of 100 μmol·L⁻¹ -1The aflatoxin B1 nucleic acid aptamer solution was added dropwise to the PDDA-loaded CdS / TiO2 / Graphene / ITO electrode prepared in step 1.1 above, incubated at 37°C for a period of time, washed with water, and dried to obtain the aflatoxin B1 nucleic acid aptamer-loaded CdS / TiO2 / Graphene / ITO electrode, which was stored at 4°C for later use; the aflatoxin B1 nucleic acid aptamer is: 5'-GTT GGG CAC GTG TTG TCT CTC TGT GTCTCG TGC CCT S-3 TCG CTA GGC CCA CA-3';

[0023] Step 1.3: Drop 20-100 μL of aflatoxin B1 at different concentrations onto region 1 of the CdS / TiO2 / Graphene / ITO electrode loaded with aflatoxin B1 nucleic acid aptamers. Add 20-100 μL of 30 μg·L⁻¹ solution. -1 Aflatoxin B1 was dropped onto region 2 of a CdS / TiO2 / Graphene / ITO electrode loaded with aflatoxin B1 nucleic acid aptamer and incubated for 20-60 minutes.

[0024] Furthermore, in step 1.2, after adding aflatoxin B1, the PDDA-loaded CdS / TiO2 / Graphene / ITO electrode is incubated for 30-80 minutes.

[0025] Furthermore, step 2 specifically includes the following steps:

[0026] Step 2.1: Take a concentration of 0.1 mol·L⁻¹ -1 Using sodium sulfate solution as the detection solution, a nucleic acid aptamer loaded with aflatoxin B1 was prepared and added to a CdS / TiO2 / Graphene / ITO electrode incubated with aflatoxin B1. A platinum electrode was used to form a dual electrode system. Under visible light irradiation, the relationship between power density and potential in test area 1 was measured.

[0027] Step 2.2: Take a concentration of 0.1 mol·L⁻¹ -1

[0028] Using sodium sulfate solution as the detection solution, a nucleic acid aptamer loaded with aflatoxin B1 was prepared and added to a CdS / TiO2 / Graphene / ITO electrode incubated with aflatoxin B1. A platinum electrode was used to form a two-electrode system. Under visible light irradiation, the relationship between power density and potential in region 2 was tested.

[0029] The advantages of this invention are as follows:

[0030] 1. The raw materials for the laser direct writing composite material provided by this invention are readily available, easy to prepare, and inexpensive.

[0031] 2. The laser-direct-writing composite material in this invention is used in specific Cd... 2+ With Ti 4+ At the molar ratio and mass ratio of polyethersulfone to cadmium acetylacetonate, when applied to a ratiometric aflatoxin B1 sensor, it can detect low concentrations of aflatoxin B1 (0.079-150 ppb), exhibiting high sensitivity, strong response and anti-interference ability, high stability and good selectivity.

[0032] 3. This invention utilizes the principle that after the aptamer is loaded onto the photoanode, it combines with the target substance in the detection liquid, generating steric hindrance and thus affecting the output power. The preparation process is simple, has strong universality, and is conducive to establishing an integrated photoelectrochemical sensing device.

[0033] 4. This provides a new approach for the development of a convenient method for detecting aflatoxin B1. Attached Figure Description

[0034] Figure 1 Scanning electron microscope (SEM) images of laser-written CdS / TiO2 / Graphene / ITO.

[0035] Figure 2 Transmission electron microscopy (TEM) images of laser-written CdS / TiO2 / Graphene / ITO.

[0036] Figure 3 X-ray photoelectron spectra of laser-written CdS / TiO2 / Graphene materials;

[0037] Figure 4 A schematic diagram of aflatoxin B1 detection based on laser direct writing CdS / TiO2 / Graphene / ITO electrode ratio method.

[0038] Figure 5 The relationship between battery power density and potential for ratiometric detection of aflatoxin B1 based on laser-written CdS / TiO2 / Graphene / ITO electrodes.

[0039] Figure 6 Standard working curve for the ratiometric detection of aflatoxin B1 based on laser-written CdS / TiO2 / Graphene / ITO electrodes. Detailed Implementation

[0040] The technical solution of the present invention will be further described below through specific implementation examples, but these examples should not be used to limit the scope of the present invention.

[0041] In this embodiment, the technical principle is to first prepare CdS / TiO2 using laser direct writing technology.

[0042] The graphene / ITO electrode offers advantages such as simple preparation process, high stability, and high electron transfer rate. Then, the aflatoxin B1 aptamer is adsorbed onto the electrode surface via the electrostatic adsorption of PDDA. Next, aflatoxin B1 standard is dropped onto the electrode loaded with its aptamer and incubated. 0.1 mol·L⁻¹

[0043] -1 Using a sodium sulfate solution as the detection solution, when light irradiates the photoanode, steric hindrance arises due to the binding of aflatoxin B1 to its corresponding aptamer. This causes changes in the number of electrons transferred to the cathode in region 1, which is loaded with different concentrations of aflatoxin B1, while the number of electrons transferred to the cathode in region 2, which is loaded with a fixed concentration of aflatoxin B1, remains essentially unchanged. The relationship between the battery's power density and potential is detected by comparing the power density of region 1 (loaded with different concentrations of aflatoxin B1) with that of region 2 (loaded with a fixed concentration of aflatoxin B1), thus achieving ratiometric detection of aflatoxin B1.

[0044] Example 1

[0045] 1. Fabrication of laser-written precursor electrodes

[0046] Weigh 0.5 g of cadmium acetylacetonate, 0.4 g of titanium dioxide acetylacetonate, and 1 g of polyethersulfone and add them to 20 mL of DMF solvent. Dissolve the powder by sonication for 60 minutes at room temperature, and stir for a certain time to ensure thorough mixing, obtaining the precursor solution. Clean the ITO conductive glass sequentially with deionized water, acetone, and anhydrous ethanol using ultrasonic cleaning for 20 minutes each, and then dry before use. Apply adhesive tape with two 0.8 cm × 2 cm notches to the conductive surface of the ITO electrode, then drop 200 μL of the precursor solution onto the conductive surface of the ITO electrode. Spin coat the material at 3000 rpm for 60 seconds using a spin coater, and dry at 80°C for 8 hours. Mark the notches as region 1 and region 2.

[0047] 2. Fabrication of CdS / TiO2 / Graphene / ITO electrodes by laser direct writing

[0048] The precursor electrode was placed under a nanolaser, and the processing pattern was drawn in the corresponding control software as a 0.8 cm × 2 cm rectangle corresponding to region 1 and region 2. The scanning speed was set to 300 mm / s, and the laser output power was adjusted to 30% of the maximum output power. Laser direct writing was performed, and after cooling to room temperature, CdS / TiO2 / Graphene / ITO electrode was obtained.

[0049] 3. CdS / TiO2 / Graphene / ITO electrode aptamer modification and binding with target analytes

[0050] (1) 2%wt PDDA solution was added dropwise to the working interface of the prepared CdS / TiO2 / Graphene / ITO electrode, incubated for 60 minutes, washed with water, and dried to obtain the PDDA-loaded CdS / TiO2 / Graphene / ITO electrode;

[0051] (2) Take 1 μL of 100 μmol·L -1 The aflatoxin B1 nucleic acid aptamer solution was added dropwise to the prepared PDDA-loaded CdS / TiO2 / Graphene / ITO electrode, incubated at 37°C for 60 minutes, washed with water, and dried to obtain the aflatoxin B1 nucleic acid aptamer-loaded CdS / TiO2 / Graphene / ITO electrode, which was stored at 4°C for later use.

[0052] (3) Drop 20-100 μL of aflatoxin B1 at different concentrations onto region 1 of the CdS / TiO2 / Graphene / ITO electrode loaded with aflatoxin B1 nucleic acid aptamers, and then drop 20-100 μL of 30 μg·L⁻¹ solution onto region 1 of the electrode. -1 Aflatoxin B1 was dropped onto region 2 of a CdS / TiO2 / Graphene / ITO electrode loaded with aflatoxin B1 aptamer and incubated for 60 minutes.

[0053] 4. Construction of the two-electrode system and determination of aflatoxin B1 concentration

[0054] A two-electrode system was constructed by using a CdS / TiO2 / Graphene / ITO electrode loaded with aflatoxin B1 aptamer and a platinum-modified photocathode, with a concentration of 0.1 mol·L⁻¹. -1 A sodium sulfate solution was used as the detection solution. Under visible light irradiation, the relationship between power density and potential in region 1 and region 2 was tested respectively.

[0055] Figure 1 The image shows a scanning electron microscope (SEM) image of a laser-written CdS / TiO2 / Graphene / ITO electrode prepared in Example 1. The material is layered graphene loaded with a large number of CdS and TiO2 particles. Figure 2 This is a transmission electron microscope (TEM) image of the laser-written CdS / TiO2 / Graphene / ITO electrode from Example 1. The particle size distribution of CdS and TiO2 is 20-40 nm. X-ray photoelectron spectroscopy indicates that this material is mainly composed of Cd, Ti, S, O, and C elements. Figure 3 ). Figure 4 This is a schematic diagram of the sensing principle for detecting aflatoxin B1 constructed using laser-written CdS / TiO2 / Graphene / ITO electrodes, as described in this invention. Figure 5The image shows the response curve of aflatoxin B1 to a two-electrode system constructed using laser-written CdS / TiO2 / Graphene / ITO electrodes. The ratio of the two-electrode output power decreases with increasing aflatoxin B1 concentration. Figure 6 To construct a standard working curve for ratiometric aflatoxin B1, at 1 μg·L⁻¹ -1 -150 μg·L -1 The linear relationship is good within the range, and the linear regression equation is y = -0.51381 + 1.76564 lgC. [AFB1] (R) 2 = 0.9995, n = 7 The detection limit is 0.079 μg·L⁻¹. -1 .

[0056] Example 2

[0057] 1. Fabrication of laser-written precursor electrodes

[0058] Weigh 0.4 g of cadmium acetylacetonate, 0.4 g of titanium dioxide acetylacetonate, and 1 g of polyethersulfone and add them to 30 mL of DMF solvent. Dissolve the powder by sonication for 60 minutes at room temperature, and stir for a certain time to ensure thorough mixing, obtaining the precursor solution. Clean the ITO conductive glass sequentially with deionized water, acetone, and anhydrous ethanol using sonication for 20 minutes each, and then dry before use. Apply adhesive tape with two 0.8 cm × 2 cm notches to the conductive surface of the ITO electrode, then drop 400 μL of the precursor solution onto the conductive surface of the ITO electrode. Spin coat the material at 2000 rpm for 120 seconds using a spin coater, and then dry at 80°C for 10 hours. Mark the notches as region 1 and region 2.

[0059] 2. Fabrication of laser-guided CdS / TiO2 / Graphene / ITO electrodes

[0060] The precursor electrode was placed under a nanolaser, and the processing pattern was drawn in the corresponding control software as a 0.8 cm × 2 cm rectangle corresponding to region 1 and region 2. The scanning speed was set to 500 mm / s, and the laser output power was adjusted to 40% of the maximum output power. Laser direct writing was performed, and after cooling to room temperature, CdS / TiO2 / Graphene / ITO electrode was obtained.

[0061] 3. CdS / TiO2 / Graphene / ITO electrode aptamer modification and binding with target analytes

[0062] (1) 2%wt PDDA solution was added dropwise to the working interface of the prepared CdS / TiO2 / Graphene / ITO electrode, incubated for 40 minutes, washed with water, and dried to obtain the PDDA-loaded CdS / TiO2 / Graphene / ITO electrode;

[0063] (2) Take 2 μL of 100 μmol·L -1 The aflatoxin B1 nucleic acid aptamer solution was added dropwise to the prepared PDDA-loaded CdS / TiO2 / Graphene / ITO electrode, incubated at 37°C for 80 minutes, washed with water, and dried to obtain the aflatoxin B1 nucleic acid aptamer-loaded CdS / TiO2 / Graphene / ITO electrode, which was stored at 4°C for later use.

[0064] (3) Drop 20-100 μL of aflatoxin B1 at different concentrations onto region 1 of the CdS / TiO2 / Graphene / ITO electrode loaded with aflatoxin B1 nucleic acid aptamers, and then drop 20-100 μL of 30 μg·L⁻¹ solution onto region 1 of the electrode. -1 Aflatoxin B1 was dropped onto region 2 of a CdS / TiO2 / Graphene / ITO electrode loaded with aflatoxin B1 aptamer and incubated for 60 minutes.

[0065] 4. Construction of the two-electrode system and determination of aflatoxin B1 concentration

[0066] A two-electrode system was constructed by using a CdS / TiO2 / Graphene / ITO electrode loaded with aflatoxin B1 aptamer and a platinum-modified photocathode, with a concentration of 0.1 mol·L⁻¹. -1 A sodium sulfate solution was used as the detection solution. Under visible light irradiation, the relationship between power density and potential in region 1 and region 2 was tested respectively.

[0067] The above provides a detailed description of a high-efficiency calculation method for piezoelectric composite materials provided by this invention. However, it should be understood that these descriptions are merely illustrative of the principles and implementation methods using specific examples and are not intended to limit the application of this invention. The scope of protection of this invention may include various modifications and equivalent solutions made to the invention without departing from the scope and spirit of the patent protection.

Claims

1. A method for preparing a CdS / TiO2 / graphene electrode based on laser direct writing technology, characterized in that, Includes the following steps: Step 1: Preparation of precursor electrode: Immerse cadmium acetylacetone powder, titanium dioxide acetylacetone, and polyethersulfone in DMF solvent, sonicate at room temperature for 30-60 minutes to dissolve the powder, and stir for a certain time to fully mix to obtain precursor solution; Sonicate ITO conductive glass with deionized water, acetone, and anhydrous ethanol for 20 minutes in sequence, and use after drying; Apply tape with two 0.8 cm × 2 cm notches to the conductive surface of ITO electrode, then drop a certain volume of precursor solution onto the conductive surface of ITO electrode, coat it in a spin coater at 1000-3000 rpm for 30-180 seconds, and dry at 80℃ for 1-12 hours to obtain precursor electrode, with the notches marked as region 1 and region 2; Step 2: Fabrication of the laser-written composite electrode: The precursor electrode is placed under a nanolaser, and the processing pattern is drawn in the corresponding control software. The scanning speed is set, the laser output power is adjusted, and laser writing is performed. After cooling to room temperature, a CdS / TiO2 / graphene electrode is obtained. The photoinduced CdS / TiO2 / graphene electrode is a composite material formed by laser writing of cadmium acetylacetonate, titanium acetylacetonate, and polyethersulfone onto an ITO conductive glass substrate. The specific component ratio is: Cd... 2+ With Ti 4+ The molar ratio is 0.25-1.5, and the mass ratio of cadmium acetylacetonate to polyethersulfone is 0.1-0.

6.

2. The method for preparing a CdS / TiO2 / graphene electrode based on laser direct writing technology according to claim 1, characterized in that, The CdS / TiO2 / graphene is a composite material formed by cadmium acetylacetonate, titanium acetylacetonate, and polyethersulfone, generated by laser direct writing. The specific component ratio is: Cd 2+ With Ti 4+ The molar ratio is 0.75-1.25, and the mass ratio of cadmium acetylacetonate to polyethersulfone is 0.3-0.

5.

3. The method for preparing a CdS / TiO2 / graphene electrode based on laser direct writing technology according to claim 1, characterized in that, The volume of the DMF solvent is 10-30 mL.

4. The method for preparing a CdS / TiO2 / graphene electrode based on laser direct writing technology according to claim 1, characterized in that, In step 1, cadmium acetylacetone powder, titanium dioxide acetylacetone, and polyethersulfone are immersed in DMF solution and stirred for 1-12 hours.

5. The method for preparing a CdS / TiO2 / graphene electrode based on laser direct writing technology according to claim 1, characterized in that, The volume of the precursor solution dropped onto the ITO electrode in step 1 is 100-500 μL.

6. The method for preparing a CdS / TiO2 / graphene electrode based on laser direct writing technology according to claim 1, characterized in that, Step 2, which involves setting the pattern to be processed and the corresponding scanning speed and laser output power in the control software of the nanolaser, includes the following steps: Step 2.1: Complete the setting of the processing pattern: Draw a 0.8 cm × 2 cm rectangle corresponding to region 1 and region 2 in the supporting control software of the nano laser instrument as the processing pattern; Step 2.2: Set the scanning speed: In the control software of the nanolaser, set the scanning speed to 100-500 mm / s; Step 2.3: Set the laser output power: Adjust the laser output power to 20%-40% of the maximum output power in the control software of the nano laser instrument.

7. A method for detecting aflatoxin B1 using an electrode prepared by the CdS / TiO2 / graphene electrode based on laser direct writing technology as described in claim 1, characterized in that: Step 1: Incubate aflatoxin B1 on the surface of a CdS / TiO2 / graphene / ITO electrode loaded with aflatoxin B1 nucleic acid aptamers; Step 2: Construct a dual-electrode system by loading aflatoxin B1 nucleic acid aptamers and incubating aflatoxin B1 onto a CdS / TiO2 / graphene / ITO electrode and a platinum-modified photocathode. Test the relationship between the power density and potential of the battery anode under illumination in the detection solution. Compare the power density of region 1 loaded with different concentrations of aflatoxin B1 with the power density of region 2 loaded with a fixed concentration of aflatoxin B1 to achieve ratiometric detection of aflatoxin B1.

8. The method according to claim 7, characterized in that, Step 1 specifically includes: Step 1.1: A 2% wt PDDA solution is added dropwise to the working interface of the CdS / TiO2 / graphene / ITO electrode for incubation, followed by washing with water and drying to obtain a PDDA-loaded CdS / TiO2 / graphene / ITO electrode. Step 1.2: Add 0.5-2 μL of 100 μmol·L⁻¹ -1 The aflatoxin B1 nucleic acid aptamer solution was added dropwise to the PDDA-loaded CdS / TiO2 / graphene / ITO electrode prepared in step 1.1 above, incubated at 37°C for a period of time, washed with water, and dried to obtain the aflatoxin B1 nucleic acid aptamer-loaded CdS / TiO2 / graphene / ITO electrode, which was stored at 4°C for later use. Step 1.3: Drop 20-100 μL of aflatoxin B1 at different concentrations onto region 1 of the CdS / TiO2 / graphene / ITO electrode loaded with aflatoxin B1 aptamers. -1 Aflatoxin B1 was dropped onto region 2 of a CdS / TiO2 / graphene / ITO electrode loaded with aflatoxin B1 nucleic acid aptamer and incubated for 20-60 minutes.

9. The method according to claim 8, characterized in that, In step 1.2, after adding aflatoxin B1, the PDDA-loaded CdS / TiO2 / graphene / ITO electrode is incubated for 30-80 minutes.

10. The method according to claim 8, characterized in that, Step 2 specifically includes the following steps: Step 2.1: Take a concentration of 0.1 mol·L⁻¹ -1 Using sodium sulfate solution as the detection solution, a nucleic acid aptamer loaded with aflatoxin B1 was prepared and added to a CdS / TiO2 / graphene / ITO electrode incubated with aflatoxin B1 to form a two-electrode system with a platinum electrode. Under visible light irradiation, the relationship between power density and potential in test area 1 was measured. Step 2.2: Take a concentration of 0.1 mol·L⁻¹ -1 Using sodium sulfate solution as the detection solution, a nucleic acid aptamer loaded with aflatoxin B1 was prepared and added to a CdS / TiO2 / graphene / ITO electrode incubated with aflatoxin B1, forming a two-electrode system with a platinum electrode. Under visible light irradiation, the relationship between power density and potential in region 2 was tested.

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