Preparation of photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal

Abstract

The invention belongs to the technical field of immunoassay and biosensing, and provides a preparation method of a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal. The invention provides a preparation method of the photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal. Specifically, hollow polyhedral flower-shaped CuO with a unique inner cavity structure is adopted as a polarity induction factor, so that multiple light refraction and scattering effects are remarkably enhanced, and the light capture efficiency is improved. Besides, when CuO is introduced to the surface of the In2O3 / ZnCdS electrode as a photocurrent polarity reversal factor, due to the energy band structure difference between CuO and In2O3 / ZnCdS, the migration path of a photon-generated carrier is changed, and the photocurrent polarity is reversed from an anode to a cathode photocurrent, so that the detection specificity of the gastrin-releasing peptide is improved. The photocurrent polarity reversal strategy effectively eliminates potential false positive signal interference, and the accuracy and sensitivity of detection are remarkably improved. According to different photoelectrochemical signal intensities of to-be-detected substances with different concentrations, the gastrin-releasing peptide is detected.

Description

Technical Field

[0001] This invention relates to a method for preparing a photoelectrochemical sensor made of a hollow polyhedral flower-shaped CuO material. Specifically, the hollow polyhedral flower-shaped CuO is introduced as a photocurrent polarity reversal factor onto the surface of an In2O3 / ZnCdS electrode, causing the photocurrent polarity to switch from anodic to cathodic. A photoelectrochemical sensor for detecting gastrin-releasing peptide was prepared, belonging to the field of novel functional materials and biosensor detection technology. Background Art

[0002] Gastrin-releasing peptide is a clinically significant tumor biomarker that is closely related to neuroendocrine tumors, and plays a key role in the diagnosis and monitoring of small cell lung cancer. As a precursor molecule of gastrin-releasing peptide, gastrin-releasing peptide shows a significantly high expression level in small cell lung cancer cells. Compared with other tumor markers, gastrin-releasing peptide has higher diagnostic sensitivity and specificity for small cell lung cancer, and can accurately reflect tumor progression and treatment response in the early stages of the disease. Therefore, the development of efficient, accurate and sensitive gastrin-releasing peptide detection methods is crucial for early diagnosis and prognosis assessment. Photoelectrochemical (PEC) sensors convert light signals into electrical signals by photoexciting photoactive materials. They have rapidly developed due to their rapid response, high sensitivity, and complete separation of the excitation source and output signal. In recent years, PEC sensors based on semiconductor-coupled heterostructures have become a research focus, aiming to improve the efficiency of photoelectric conversion. Photoelectrochemical sensors are a novel analytical method that combines electrochemical and optical technologies. Due to the phase separation between the excitation light source and the output signal, they offer advantages such as fast response, low background signal, and high sensitivity. Compared to traditional analytical methods, the photoelectrochemical biosensor employed in the present invention offers advantages such as high sensitivity, good selectivity, fast response, simple operation, and ease of miniaturization. Therefore, a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal was prepared to achieve sensitive detection of gastrin-releasing peptide (Pro-GRP).

[0003] By precisely controlling the heating rate, this study successfully synthesized hollow, polyhedral, flower-shaped copper oxide with a unique cavity structure. This design utilizes CuO as a polarity-inducing factor. This incorporation reconfigures the energy band alignment and modulates the carrier transport pathway in the Z-type heterojunction substrate, resulting in a reversal of the photocurrent polarity from the anode to the cathode. Because the polarity of the background signal is opposite to that of the detection signal, this polarity reversal not only eliminates background interference but also reduces the risk of false positives, significantly improving the accuracy and reliability of PEC sensor detection. Furthermore, the energy band alignment of the In2O3 / ZnCdS heterojunction facilitates the separation and transport of photogenerated carriers and significantly enhances the photoelectric response. This study fabricated a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal, enabling the quantitative detection of gastrin-releasing peptide (Pro-GRP). The sensor exhibits high sensitivity, fast response, a wide detection range, a low detection limit, and excellent stability, selectivity, and reproducibility. The construction of this photoelectrochemical sensor provides a new approach for the sensitive detection of Pro-GRP. Summary of the Invention

[0004] One of the purposes of the present invention is to use CuO as a polarity reversal factor to achieve the reversal of the photocurrent polarity from the anode to the cathode, thereby eliminating background interference, reducing the risk of false positives, and improving the accuracy and reliability of PEC sensor detection.

[0005] A second objective of the present invention is to synthesize hollow, polyhedral, flower-like CuO from a CuMOF precursor by precisely controlling the heating rate, thereby enabling it to function as a highly efficient polarity-reversing component. Its unique cavity structure not only enhances light capture efficiency through multiple photorefractive effects but also facilitates charge carrier transfer, amplifying the cathode photocurrent signal.

[0006] The third objective of the present invention is to create a Z-type heterojunction between In2O3 and ZnCdS, shortening the electron transfer path. Furthermore, the separation of oxidation and reduction active centers significantly improves charge separation efficiency, inhibiting electron-hole pair recombination and doubling the photocurrent response rate.

[0007] The technical solutions of the present invention are as follows: A method for preparing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal is characterized by comprising the following steps: (1) Cut the ITO glass into 2 × 0.8 cm 2 Long strips were ultrasonically cleaned with detergent powder, acetone, ethanol, and deionized water for 30 min and dried at 60 °C for 24 h; (2) Add 6.0 μL of 2.0-10.0 mg / mL In2O3 dispersion onto the electrode surface and allow to dry at room temperature. (3) Take 6.0 μL of 2.0 ~ 10.0 mg / mL ZnCdS dispersion and drop it onto the electrode surface, then let it dry at room temperature; (4) Add 6.0 μL of 1.0 to 5.0 mmol / L thioglycolic acid solution to the electrode surface to introduce carboxyl groups, and let it dry at room temperature. Rinse the electrode surface with deionized water and let it dry at room temperature. (5) Take 6.0 μL of 2:1 to 8:1 carbodiimide solution and drop it onto the electrode surface to activate the carboxyl groups. Let it dry at room temperature. Rinse the electrode surface with deionized water and let it dry at room temperature. (6) Continue to take 6.0 μL of 0.5 ~ 15.0 μg / mL gastrin-releasing peptide-1 and add it to the electrode surface, rinse the electrode surface with phosphate buffer pH = 7.38, and dry it in a refrigerator at 4℃; (7) Add 3.0 μL of 0.5-2.0 wt% bovine serum albumin solution dropwise to the electrode surface to block the nonspecific active sites on the electrode surface. Rinse the electrode surface with phosphate buffer (pH = 7.38) and dry in a refrigerator at 4°C. (8) Add 6.0 μL of gastrin-releasing peptide-antigen at different concentrations of 10 fg / mL to 100 ng / mL to the electrode surface, incubate at room temperature for 1 hour, rinse the electrode surface with phosphate buffer (pH = 7.38), and dry in a refrigerator at 4°C; (9) Finally, 6.0 μL of CuO-Ab2-BSA solution was added to complete the platform construction, thereby constructing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal and storing it in a refrigerator at 4 °C for future use.

[0008] 2. The hollow polyhedral flower-shaped CuO and In2O3 / ZnCdS dispersions are prepared as follows: (1) Preparation of In2O3 First, In(NO₃)⋅4H₂O (0.47 g) and terephthalic acid (0.18 g) were dissolved in 54 mL of N,N-dimethylformamide (DMF) and reacted for 10 minutes under continuous magnetic stirring. The resulting solution was then transferred to a flask and subjected to solvothermal treatment in an oil bath at 100°C for 1 to 3 hours. After cooling naturally to room temperature, the white precipitate was collected and washed three times with ethanol and deionized water, followed by vacuum drying at 60°C for 12 hours to obtain the MIL-68 precursor. Finally, the synthesized MIL-68 powder was placed in a ceramic boat and calcined at 500°C in a muffle furnace for 2 to 4 hours to obtain the desired In₂O₃ nanoclusters. (2) Preparation of ZnCdS Zn(NO3)2⋅6H2O (0.379 g), Cd(NO3)3⋅4H2O (0.617 g), and thiourea (0.984 g) were dissolved in 20 mL of deionized water and stirred under ultrasonic assisted stirring until completely dissolved. Subsequently, the homogeneous mixture was transferred to a polytetrafluoroethylene-lined autoclave and hydrothermally treated at 160°C for 2 to 6 hours. After cooling naturally to room temperature, the resulting orange precipitate was collected and centrifuged and washed with ethanol and deionized water three times each, and then dried at 120°C for 12 hours to obtain the ZnCdS product. (3) Preparation of CuO First, Cu(NO₃)⋅3H₂O (0.041 g), triformic acid (0.024 g), and lauric acid (2.55 g) were dissolved in 15 mL of n-butanol and reacted under magnetic stirring for 30 minutes to form a homogeneous blue solution. The mixture was then transferred to a Teflon-lined autoclave and hydrothermally heated at 140°C for 5 hours. After cooling to room temperature, the product was centrifuged, repeatedly washed with ethanol, and dried at 60°C for 12 hours to obtain a blue CuMOF precursor. For subsequent thermal conversion, the as-prepared CuMOF was placed in a ceramic boat and calcined at 350°C for 2 hours in a muffle furnace at a controlled heating rate of 0.5–3°C / min, ultimately yielding a hollow polyhedral flower-like copper oxide structure.

[0009] 3. A method for detecting gastrin-releasing peptide, comprising the following steps: (1) The photoelectrochemical workstation was used for testing with a three-electrode system. The Ag / AgCl electrode was used as the reference electrode, the Pt electrode was used as the counter electrode, and the prepared CuO-induced In2O3 / ZnCdS composite photoelectrochemical sensor was used as the working electrode. A 100 W LED light was used as the irradiation source. The light was turned on and off every 20 seconds, and the bias voltage was set to 0 V. (2) Detect the photoelectric signal generated by the antigen at different concentrations in 10 mL of phosphate buffer solution containing 0 to 0.2 mol / L ascorbic acid at pH = 6.81 to 8.04, and draw a working curve; (3) The gastrin-releasing peptide antigen solution is replaced by the test sample solution for testing.

[0010] Beneficial results of the present invention The present invention successfully synthesized hollow polyhedral flower-shaped copper oxide, which can be used as an efficient polarity reversal component. The preparation method of this material is simple, and the incident light undergoes multiple refraction / scattering effects inside the material, significantly improving the photoelectric conversion efficiency and amplifying the cathode photocurrent signal.

[0011] (2) In the present invention, the photocurrent signal is transformed from the anode to the cathode through the action of the CuO inversion factor, achieving polarity switching, which can significantly improve the performance of the sensor, eliminate background noise and reduce false positive signals, thereby improving the reliability and accuracy of detection.

[0012] The band gaps of In2O3 and ZnCdS in this invention are matched, and their energy levels are staggered to form an in-situ Z-type heterojunction. The uniform distribution and close contact at the interface shorten the electron transfer path while providing a stable electron driving force for the intrinsic electric field, accelerating the transfer of photogenerated carriers. This significantly increases the photocurrent response and enhances detection sensitivity.

[0013] (3) The photoelectrochemical sensor prepared by the present invention is used for quantitative detection of gastrin-releasing peptide, has a fast response speed, a wide linear range, a low detection limit, good stability, selectivity and reproducibility, and can achieve simple, fast, highly sensitive and specific detection. DETAILED DESCRIPTION

[0014] (The present invention will now be further described through specific embodiments, but is not limited thereto) Example 1. A method for preparing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal, comprising the following steps: (1) Cut the ITO glass into 2.0 × 0.8 cm 2 The strips were ultrasonically cleaned with detergent powder, acetone, ethanol, and deionized water for 30 min and dried at 60 °C for 24 h; (2) Add 6.0 μL of 6.0 mg / mL In2O3 dispersion onto the electrode surface and allow to dry at room temperature. (3) Take 6.0 μL of 3.0 mg / mL ZnCdS dispersion and drop them onto the electrode surface, then let them dry at room temperature. (4) Add 6.0 μL of 3.0 mmol / L thioglycolic acid solution dropwise to the electrode surface to introduce carboxyl groups. Allow to dry at room temperature. Rinse the electrode surface with deionized water and allow to dry at room temperature. (5) Take 6.0 μL of 6:1 carbodiimide solution and drop it onto the electrode surface to activate the carboxyl groups. Let it dry at room temperature. Rinse the electrode surface with deionized water and let it dry at room temperature. (6) Continue to take 6.0 μL of 5.0 μg / mL gastrin-releasing peptide-1 and add it to the electrode surface, rinse the electrode surface with phosphate buffer solution pH = 7.38, and dry it in a refrigerator at 4°C; (7) 3.0 μL of 1.0 wt% bovine serum albumin solution was added dropwise to the electrode surface to block the nonspecific active sites on the electrode surface. The electrode surface was rinsed with phosphate buffer (pH = 7.38) and dried in a refrigerator at 4 °C. (8) Add 6.0 μL and 10 fg / mL gastrin-releasing peptide-antigen at different concentrations to the electrode surface, incubate at room temperature for 1 hour, rinse the electrode surface with phosphate buffer solution (pH = 7.38), and dry in a refrigerator at 4°C; (9) Finally, 6.0 μL of CuO-Ab2-BSA solution was added to complete the platform construction, thereby constructing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal and storing it in a refrigerator at 4 °C for future use.

[0015] Example 2. A method for preparing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal, comprising the following steps: (1) Cut the ITO glass into 2.0 × 0.8 cm 2 The strips were ultrasonically cleaned with detergent powder, acetone, ethanol, and deionized water for 30 min and dried at 60 °C for 24 h; (2) Add 6.0 μL of 8.0 mg / mL In2O3 dispersion to the electrode surface and let it dry at room temperature; (3) Take 6.0 μL of 4.0 mg / mL ZnCdS dispersion and drop them onto the electrode surface, then let them dry at room temperature. (4) Add 6.0 μL of 4.0 mmol / L thioglycolic acid solution dropwise to the electrode surface to introduce carboxyl groups, and let it dry at room temperature. Rinse the electrode surface with deionized water and let it dry at room temperature. (5) Take 6.0 μL of 7:1 carbodiimide solution and drop it onto the electrode surface to activate the carboxyl groups. Let it dry at room temperature. Rinse the electrode surface with deionized water and let it dry at room temperature. (6) Continue to take 6.0 μL of 10.0 μg / mL gastrin-releasing peptide-1 and add it to the electrode surface, rinse the electrode surface with phosphate buffer solution pH = 7.38, and dry it in a refrigerator at 4°C; (7) 3.0 μL of 1.5 wt% bovine serum albumin solution was added dropwise to the electrode surface to block the nonspecific active sites on the electrode surface. The electrode surface was rinsed with phosphate buffer (pH = 7.38) and dried in a refrigerator at 4 °C. (8) Add 6.0 μL and 100 fg / mL gastrin-releasing peptide-antigen at different concentrations to the electrode surface, incubate at room temperature for 1 hour, rinse the electrode surface with phosphate buffer (pH = 7.38), and dry in a refrigerator at 4°C; (9) Finally, 6.0 μL of CuO-Ab2-BSA solution was added to complete the platform construction, thereby constructing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal and storing it in a refrigerator at 4 °C for future use.

[0016] Example 3. A method for preparing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal, comprising the following steps: (1) Cut the ITO glass into 2.0 × 0.8 cm 2 The strips were ultrasonically cleaned with detergent powder, acetone, ethanol, and deionized water for 30 min and dried at 60 °C for 24 h; (2) Add 6.0 μL of 10.0 mg / mL In2O3 dispersion onto the electrode surface and allow to dry at room temperature. (3) Take 6.0 μL of 5.0 mg / mL ZnCdS dispersion and drop them onto the electrode surface, and let them dry at room temperature; (4) Add 6.0 μL of 5.0 mmol / L thioglycolic acid solution dropwise to the electrode surface to introduce carboxyl groups, and let it dry at room temperature. Rinse the electrode surface with deionized water and let it dry at room temperature. (5) Take 6.0 μL of 8:1 carbodiimide solution and drop it onto the electrode surface to activate the carboxyl groups. Let it dry at room temperature. Rinse the electrode surface with deionized water and let it dry at room temperature. (6) Continue to take 6.0 μL of 15.0 μg / mL gastrin-releasing peptide-1 and add it to the electrode surface, rinse the electrode surface with phosphate buffer solution pH = 7.38, and dry it in a refrigerator at 4°C; (7) 3.0 μL of 2.0 wt% bovine serum albumin solution was added dropwise to the electrode surface to block the nonspecific active sites on the electrode surface. The electrode surface was rinsed with phosphate buffer (pH = 7.38) and dried in a refrigerator at 4 °C. (8) Add 6.0 μL and 10 ng / mL gastrin-releasing peptide-antigen at different concentrations to the electrode surface, incubate at room temperature for 1 hour, rinse the electrode surface with phosphate buffer (pH = 7.38), and dry in a refrigerator at 4°C; (9) Finally, 6.0 μL of CuO-Ab2-BSA solution was added to complete the platform construction, thereby constructing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal and storing it in a refrigerator at 4 °C for future use.

[0017] Example 4. The hollow polyhedral flower-shaped CuO and In2O3 / ZnCdS dispersion were prepared as follows: (1) Preparation of In2O3 First, In(NO3)3⋅4H2O (0.47 g) and terephthalic acid (0.18 g) were dissolved in 54 mL of N,N-dimethylformamide (DMF) and reacted for 10 minutes under continuous magnetic stirring. Subsequently, the resulting solution was transferred to a flask and subjected to solvothermal treatment in an oil bath at 100°C for 1 hour. After cooling naturally to room temperature, the white precipitate was collected and washed with ethanol and deionized water (three times each), followed by vacuum drying at 60°C for 12 hours to obtain the MIL-68 precursor. Finally, the synthesized MIL-68 powder was placed in a ceramic boat and calcined at 500°C in a muffle furnace for 3 hours to obtain the desired In2O3 nanoclusters. (2) Preparation of ZnCdS Zn(NO3)2⋅6H2O (0.379 g), Cd(NO3)3⋅4H2O (0.617 g), and thiourea (0.984 g) were dissolved in 20 mL of deionized water and stirred under ultrasonication until completely dissolved. The homogeneous mixture was then transferred to a polytetrafluoroethylene-lined autoclave and hydrothermally treated at 160°C for 3.5 hours. After cooling naturally to room temperature, the resulting orange precipitate was collected and washed by centrifugation with ethanol and deionized water three times each, followed by drying at 120°C for 12 hours to obtain the ZnCdS product. (3) Preparation of CuO First, Cu(NO₃)⋅3H₂O (0.041 g), triformic acid (0.024 g), and lauric acid (2.55 g) were dissolved in 15 mL of n-butanol and reacted under magnetic stirring for 30 minutes to form a homogeneous blue solution. The mixture was then transferred to a Teflon-lined autoclave and hydrothermally heated at 140°C for 5 hours. After cooling to room temperature, the product was centrifuged, repeatedly washed with ethanol, and dried at 60°C for 12 hours to obtain a blue CuMOF precursor. For subsequent thermal conversion, the as-prepared CuMOF was placed in a ceramic boat and calcined at 350°C for 2 hours in a muffle furnace at a controlled heating rate of 0.5°C / min, ultimately yielding a hollow polyhedral flower-like copper oxide structure.

[0018] Example 5. The hollow polyhedral flower-shaped CuO and In2O3 / ZnCdS dispersion were prepared as follows: (1) Preparation of In2O3 First, In(NO₃)⋅4H₂O (0.47 g) and terephthalic acid (0.18 g) were dissolved in 54 mL of N,N-dimethylformamide (DMF) and reacted for 10 minutes under continuous magnetic stirring. Subsequently, the resulting solution was transferred to a flask and subjected to solvothermal treatment in an oil bath at 100°C for 1.5 hours. After cooling naturally to room temperature, the white precipitate was collected and washed with ethanol and deionized water (three times each), followed by vacuum drying at 60°C for 12 hours to obtain the MIL-68 precursor. Finally, the synthesized MIL-68 powder was placed in a ceramic boat and calcined at 500°C in a muffle furnace for 3.5 hours to obtain the desired In₂O₃ nanoclusters. (2) Preparation of ZnCdS Zn(NO3)2⋅6H2O (0.379 g), Cd(NO3)3⋅4H2O (0.617 g), and thiourea (0.984 g) were dissolved in 20 mL of deionized water and stirred under ultrasonic assisted stirring until completely dissolved. Subsequently, the homogeneous mixture was transferred to a polytetrafluoroethylene-lined autoclave and hydrothermally treated at 160°C for 4 hours. After cooling naturally to room temperature, the resulting orange precipitate was collected and washed by centrifugation with ethanol and deionized water (three times each), followed by drying at 120°C for 12 hours to obtain the ZnCdS product. (3) Preparation of CuO First, Cu(NO₃)⋅3H₂O (0.041 g), triformic acid (0.024 g), and lauric acid (2.55 g) were dissolved in 15 mL of n-butanol and reacted under magnetic stirring for 30 minutes to form a homogeneous blue solution. The mixture was then transferred to a Teflon-lined autoclave and hydrothermally heated at 140°C for 5 hours. After cooling to room temperature, the product was centrifuged, repeatedly washed with ethanol, and dried at 60°C for 12 hours to obtain a blue CuMOF precursor. For subsequent thermal conversion, the as-prepared CuMOF was placed in a ceramic boat and calcined at 350°C for 2 hours in a muffle furnace at a controlled heating rate of 1°C / min, ultimately yielding a hollow polyhedral flower-like copper oxide structure.

[0019] Example 6. The hollow polyhedral flower-shaped CuO and In2O3 / ZnCdS dispersion were prepared as follows: (1) Preparation of In2O3 First, In(NO3)3⋅4H2O (0.47 g) and terephthalic acid (0.18 g) were dissolved in 54 mL of N,N-dimethylformamide (DMF) and reacted for 10 minutes under continuous magnetic stirring. Subsequently, the resulting solution was transferred to a flask and subjected to solvothermal treatment at 100°C in an oil bath for 2 hours. After cooling naturally to room temperature, the white precipitate was collected and washed with ethanol and deionized water (three times each), followed by vacuum drying at 60°C for 12 hours to obtain the MIL-68 precursor. Finally, the synthesized MIL-68 powder was placed in a ceramic boat and calcined at 500°C in a muffle furnace for 4 hours to obtain the desired In2O3 nanoclusters. (2) Preparation of ZnCdS Zn(NO3)2⋅6H2O (0.379 g), Cd(NO3)3⋅4H2O (0.617 g), and thiourea (0.984 g) were dissolved in 20 mL of deionized water and stirred under ultrasonication until completely dissolved. The homogeneous mixture was then transferred to a polytetrafluoroethylene-lined autoclave and hydrothermally treated at 160°C for 5 hours. After cooling naturally to room temperature, the resulting orange precipitate was collected and washed by centrifugation with ethanol and deionized water three times each, followed by drying at 120°C for 12 hours to obtain the ZnCdS product. (3) Preparation of CuO First, Cu(NO₃)⋅3H₂O (0.041 g), triformic acid (0.024 g), and lauric acid (2.55 g) were dissolved in 15 mL of n-butanol and reacted under magnetic stirring for 30 minutes to form a homogeneous blue solution. The mixture was then transferred to a Teflon-lined autoclave and hydrothermally heated at 140°C for 5 hours. After cooling to room temperature, the product was centrifuged, repeatedly washed with ethanol, and dried at 60°C for 12 hours to obtain a blue CuMOF precursor. For subsequent thermal conversion, the as-prepared CuMOF was placed in a ceramic boat and calcined at 350°C for 2 hours in a muffle furnace at a controlled heating rate of 1.5°C / min, ultimately yielding a hollow polyhedral flower-like copper oxide structure.

[0020] Example 7 The method for detecting gastrin-releasing peptide comprises the following steps: (1) The photoelectrochemical workstation was used for testing with a three-electrode system. The Ag / AgCl electrode was used as the reference electrode, the Pt electrode was used as the counter electrode, and the prepared CuO-induced In2O3 / ZnCdS composite photoelectrochemical sensor was used as the working electrode. A 100 W LED light was used as the irradiation source. The light was turned on and off every 20 seconds, and the bias voltage was set to 0 V. (2) Detect the photoelectric signal generated by the antigen at different concentrations in 10 mL of phosphate buffer solution containing 0.1 mol / L ascorbic acid at pH = 7.38, and draw a working curve; (3) The gastrin-releasing peptide antigen solution is replaced by the test sample solution for testing.

Claims

1. A method for preparing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal, characterized in that: The following steps are involved: (1) Cut the ITO glass into 2 × 0.8 cm 2 Long strips were ultrasonically cleaned with detergent powder, acetone, ethanol, and deionized water for 30 min and dried at 60 °C for 24 h; (2) Add 6.0 μL of 2.0-10.0 mg / mL In2O3 dispersion onto the electrode surface and allow to dry at room temperature. (3) Take 6.0 μL of 2.0 ~ 10.0 mg / mL ZnCdS dispersion and drop it onto the electrode surface, then let it dry at room temperature; (4) Add 6.0 μL of 1.0 to 5.0 mmol / L thioglycolic acid solution to the electrode surface to introduce carboxyl groups, and let it dry at room temperature. Rinse the electrode surface with deionized water and let it dry at room temperature. (5) Take 6.0 μL of 2:1 to 8:1 carbodiimide solution and drop it onto the electrode surface to activate the carboxyl groups. Let it dry at room temperature. Rinse the electrode surface with deionized water and let it dry at room temperature. (6) Continue to take 6.0 μL of 0.5 ~ 15.0 μg / mL gastrin-releasing peptide-1 and add it to the electrode surface, rinse the electrode surface with phosphate buffer pH = 7.38, and dry it in a refrigerator at 4℃; (7) Add 3.0 μL of 0.5-2.0 wt% bovine serum albumin solution dropwise to the electrode surface to block the nonspecific active sites on the electrode surface. Rinse the electrode surface with phosphate buffer (pH = 7.38) and dry in a refrigerator at 4°C. (8) Add 6.0 μL of gastrin-releasing peptide-antigen at different concentrations of 10 fg / mL to 100 ng / mL to the electrode surface, incubate at room temperature for 1 hour, rinse the electrode surface with phosphate buffer (pH = 7.38), and dry in a refrigerator at 4°C; (9) Finally, 6.0 μL of CuO-Ab2-BSA solution was added to complete the platform construction, thereby constructing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal and storing it in a refrigerator at 4 °C for future use.

2. The method for preparing a photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal according to claim 1, wherein the preparation of the hollow polyhedral flower-shaped CuO and the In2O3 / ZnCdS dispersion is characterized by the following steps: (1) Preparation of In2O3 First, In(NO₃)⋅4H₂O (0.47 g) and terephthalic acid (0.18 g) were dissolved in 54 mL of N,N-dimethylformamide (DMF) and reacted for 10 minutes under continuous magnetic stirring. The resulting solution was then transferred to a flask and subjected to solvothermal treatment in an oil bath at 100°C for 1 to 3 hours. After cooling naturally to room temperature, the white precipitate was collected and washed three times with ethanol and deionized water, followed by vacuum drying at 60°C for 12 hours to obtain the MIL-68 precursor. Finally, the synthesized MIL-68 powder was placed in a ceramic boat and calcined at 500°C in a muffle furnace for 2 to 4 hours to obtain the desired In₂O₃ nanoclusters. (2) Preparation of ZnCdS Zn(NO3)2⋅6H2O (0.379 g), Cd(NO3)3⋅4H2O (0.617 g), and thiourea (0.984 g) were dissolved in 20 mL of deionized water and stirred under ultrasonic assisted stirring until completely dissolved. Subsequently, the homogeneous mixture was transferred to a polytetrafluoroethylene-lined autoclave and hydrothermally treated at 160°C for 2 to 6 hours. After cooling naturally to room temperature, the resulting orange precipitate was collected and washed by centrifugation with ethanol and deionized water (three times each), followed by drying at 120°C for 12 hours to obtain the ZnCdS product. (3) Preparation of CuO First, Cu(NO₃)⋅3H₂O (0.041 g), triformic acid (0.024 g), and lauric acid (2.55 g) were dissolved in 15 mL of n-butanol and reacted under magnetic stirring for 30 minutes to form a homogeneous blue solution. The mixture was then transferred to a Teflon-lined autoclave and hydrothermally heated at 140°C for 5 hours. After cooling to room temperature, the product was centrifuged, repeatedly washed with ethanol, and dried at 60°C for 12 hours to obtain a blue CuMOF precursor. For subsequent thermal conversion, the as-prepared CuMOF was placed in a ceramic boat and calcined at 350°C for 2 hours in a muffle furnace at a controlled heating rate of 0.5–3°C / min, ultimately yielding a hollow polyhedral flower-like copper oxide structure.

3. The photoelectrochemical sensor based on CuO-induced photocurrent polarity reversal prepared by the preparation method according to claim 1, which is used for the detection of gastrin-releasing peptide, characterized in that: Here are the steps: (1) The photoelectrochemical workstation was used for testing with a three-electrode system. The Ag / AgCl electrode was used as the reference electrode, the Pt electrode was used as the counter electrode, and the prepared CuO-induced In2O3 / ZnCdS composite photoelectrochemical sensor was used as the working electrode. A 100W LED light was used as the irradiation source. The light was turned on and off every 20 seconds, and the bias voltage was set to 0 V. (2) Detect the photoelectric signal generated by the antigen at different concentrations in 10 mL of phosphate buffer solution containing 0 to 0.2 mol / L ascorbic acid at pH = 6.81 to 8.04, and draw a working curve; (3) The gastrin-releasing peptide antigen solution is replaced by the test sample solution for testing.