A preparation method and application of photoelectrochemical sensor

Abstract

The present invention discloses a preparation method and application of a photoelectrochemical sensor, and its preparation comprises the following steps: the first step: dissolving 4,6-dihydrazinopyrimidine and o-vanillin in a mixture to obtain a solute, subjecting the solute to ultrasonic, heating and filtering treatment to obtain a Dy6-SCN solution; the second step: pretreating the FTO slice; the third step: taking out the FTO, adding the Dy6-SCN solution, evaporating naturally, and obtaining a Dy6-SCN / FTO electrode; the fourth step: heating and cooling the prepared electrode, and finally obtaining a Dy-OSCN / FTO electrochemical sensor. The photoelectrochemical sensor is applied to the detection of human urine. Compared with the traditional potentiometric method, the photopotential method provided by the present invention can perform AA detection in the absence of current, greatly reducing the oxidation-reduction of the semiconductor and the target object during the detection process, so that the repeatability and stability of the electrode are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of AA detection, in particular to a method for preparing a photoelectrochemical sensor and an application in detecting human urine. Background Art

[0002] For people, repeatedly drawing blood to test the AA content in the blood is very unfriendly to the subjects, and it also brings the risk of trauma and infection to the subjects during the test process. AA exists not only in human blood, but also widely in extracellular fluid, blood and urine. Evaluating the AA content in the human body by detecting the AA concentration in human urine has pointed out a new direction for non-invasive testing of AA content in the human body. By collecting human urine and measuring the AA content in vitro, the AA level in human blood can be effectively fed back, so as to achieve the purpose of monitoring the health indicator of human AA content without repeated blood sampling.

[0003] Based on the above reasons, in order to achieve rapid, low-cost and accurate analysis of AA content in human urine, various AA detection technologies have been continuously developed, such as high-performance liquid chromatography, ultraviolet spectrophotometry, etc., but such methods often require the support of large instruments, the operation is complicated during the test process, the detection efficiency is low, and the test cost is high. Due to the inherent characteristics of electrochemical sensors, it provides a promising on-site detection mode for rapid online monitoring of AA concentration in blood, and also provides the possibility for product conversion. However, achieving high sensitivity and wide detection range is the main challenge for practical application. The electrochemical measurement of AA is based on the redox reaction of AA on the electrode surface. In general, the direct electrochemical oxidation of AA on conventional electrodes is an irreversible and slow reaction that requires a high overpotential, which will bring about disadvantages such as electrode contamination, instability, and catalysis of other oxidizable substances so that the product coexists and interferes with the test. In order to improve the selectivity of AA and reduce the overpotential of catalytic oxidation, the bare electrode surface is usually modified by one or more electron mediators, conductive or selective polymer membranes, and ascorbate oxidase. This electrode modification requires long and tedious preparation steps, and the introduction of the peripheral polymer membrane makes the electron transfer process extremely complicated.

[0004] Photoelectrochemical sensing is a new analytical method developed from electroanalysis based on the principle of light-to-electron conversion. Due to the complete separation of the input signal and the output signal, the photoelectrochemical sensor has the advantages of lower sensitivity and faster response speed than the traditional electrochemical sensor. Compared with traditional optical sensors, PEC sensors only require simple instruments and equipment, which can reduce the cost of detection. In recent years, the application of biosensors in the food and pharmaceutical industries has aroused great interest. Due to the biological component basis of biosensors, they can operate in complex matrices, have short response times and are miniaturized, making them ideal sensing systems for effectively screening and selectively detecting phenolic compounds, and are very useful tools for analyzing tetracycline. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the deficiencies of the prior art, the present invention provides a method for preparing a photoelectrochemical sensor, and applies the photoelectrochemical sensor to the detection of human urine to solve the above-mentioned problems.

[0007] (II) Technical solution

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a method for preparing a photoelectrochemical sensor, comprising the following steps:

[0009] The first step: dissolving 4,6-dihydrazinopyrimidine (0.1 mmol / L) and o-vanillin (0.2 mmol / L) in a mixture to obtain a solute, and subjecting the solute to ultrasonic, heating and filtering treatments to finally obtain a Dy6-SCN solution;

[0010] Step 2: Clean the FTO slices to obtain pre-treated FTO;

[0011] Step 3: Take out the pretreated FTO, add Dy6-SCN solution, evaporate naturally, and obtain Dy6-SCN / FTO electrode;

[0012] Step 4: Heat and cool the Dy6-SCN / FTO electrode to finally obtain a photoelectrochemical sensor.

[0013] Preferably, the solute is ultrasonically treated, heated and filtered in the first step as follows: the solute is placed in a 25 ml sample bottle, ultrasonically treated until the solid is completely dissolved, 0.3 mmol / L of triethylamine and 0.2 mmol / L of Dy(SCN)3·6H2O are added in sequence, and ultrasonically treated again until the solid is dissolved, the lid is tightened and sealed, and the solution is placed in an oven and heated to 80°C and maintained at the temperature for 4 hours, then cooled to room temperature, and the solution is filtered until it becomes clear to obtain a Dy6-SCN solution.

[0014] Preferably, the mixture in the first step is a mixture of 5 ml of methanol and 10 ml of acetonitrile.

[0015] Preferably, the FTO pretreatment in the second step includes the following:

[0016] S1: Immerse the FTO slice in detergent water for 0.5 h;

[0017] S2: sonication with 1 M NaOH for 0.5 h;

[0018] S3: sonicate with ethanol for about 0.5 h and blow dry with nitrogen;

[0019] S4: The geometric area exposed to light on the FTO surface is 0.81 cm 2 .

[0020] Preferably, the size of the FTO slice is 1.5*2.5 cm.

[0021] Preferably, the specific preparation steps of the Dy6-SCN / FTO electrode in the third step are as follows:

[0022] S1: Place 11 pre-treated FTO sheets facing upward in a φ=90mmol / L watch glass;

[0023] S2: add 10 ml Dy6-SCN solution;

[0024] S3: Cover the plate and place it on a stable horizontal laboratory table to evaporate the solvent. After the solvent evaporates, it is naturally air-dried. The Dy6-SCN / FTO electrode is prepared.

[0025] Preferably, the photoelectrochemical sensor preparation process in the fourth step is as follows:

[0026] S1: Place the Dy6-SCN / FTO electrode in a tube furnace;

[0027] S2: In a nitrogen atmosphere, heat to 200°C, 300°C, 400°C and 500°C at a heating rate of 2°C / min, and maintain the temperature for 2h;

[0028] S3: The room temperature is then cooled to normal temperature to obtain a photoelectrochemical sensor.

[0029] The photoelectric chemical sensor method for detecting human urine comprises the following steps:

[0030] Step 1: Take an actual sample of urine;

[0031] Step 2: Place the Dy6-SCN / FTO electrode sintered at 400°C into the photoelectric detection cell, add 2.5 ml of PBS solution, and use saturated calomel as the reference electrode to form a two-electrode detection system;

[0032] Step 3: Use 465nm light and 10W LED light source to continuously excite the light from the side at a fixed distance, and use the open circuit potential-time technology of the electrochemical workstation to record the experimental data;

[0033] Step 4: After the potential signal is stable, add 0.025ml 10mmol / L PBS sample solution twice, 0.05ml 10mmol / L twice, 0.075ml 10mmol / L urine actual sample solution twice, 0.1ml 10mmol / L, and 0.1ml 10mmol / L PBS sample solution twice, record the photopotential data, repeat the same operation three times, and use the obtained data to calculate the recovery rate and related data of PEC detection of AA.

[0034] (III) Beneficial effects

[0035] Compared with the prior art, the present invention provides a method for preparing a photoelectrochemical sensor and a method for detecting human urine, which have the following beneficial effects:

[0036] 1. In order to solve the problems and defects of the test methods in the prior art, the present invention proposes an enzyme-free AA photoelectric potential detection system based on Dy6-SCN single crystal semiconductor material. Because Dy6-SCN single crystal semiconductor material has a regular structure, it is helpful for carrier separation and transmission inside the semiconductor under light excitation. After Dy6-SCN single crystal semiconductor material is modified to the electrode surface and sintered, it has stable chemical properties and is not easy to be photocorroded, which greatly improves the stability and repeatability of the detection. When the photoelectric potential method is used for testing, almost no current flows through the electrode surface during the detection process, and no redox reaction occurs on the interface, thus avoiding the redox reaction of the target substance and other substances in the electrochemical test, and will not consume the target molecules and other molecules in the system, and will not introduce new substances, and the entire system will not be damaged. Because the photoelectric potential detection method has the above-mentioned advantages, the use of Dy6-SCN single crystal semiconductor material to realize low-cost, fast and accurate testing of AA provides a new idea for the detection of human life substance molecules. For this reason, the present invention proposes a method for preparing a photoelectrochemical sensor and a method for applying the sensor to human urine.

[0037] 2. The preparation method of the photoelectrochemical sensor and the detection method of human urine use a photopotential method that can perform AA detection in the absence of current, compared with the traditional potentiometric method, which greatly reduces the oxidation-reduction of the semiconductor and the target during the detection process, thereby ensuring the repeatability and stability of the electrode.

[0038] 3. The preparation method of the photoelectrochemical sensor and the detection method of human urine. The photoelectrochemical sensor platform has a wider linear response range, stable signal, high repeatability, and is practical.

[0039] 4. The preparation method of the photoelectrochemical sensor and the detection method of human urine. Since the prepared Dy-OSCN single crystal has a regular microstructure, the separation and transmission of internal carriers are accelerated, and the chemical properties become more stable under light excitation.

[0040] 5. The preparation method of the photoelectrochemical sensor and the detection method applied to human urine. The PEC potential method used in the work makes no current flow through the semiconductor, no redox reaction occurs in the system, photoelectric corrosion is reduced, less interference is introduced in the detection process, and the repeatability and stability of the electrode are effectively guaranteed.

[0041] 6. The preparation method of the photoelectrochemical sensor and the detection method of human urine, Dy-OSCN single crystal was successfully applied to the PEC detection of AA. The linear range of the prepared PEC sensor is 7.94×10 -6 mol / L-1.113×10 -2 mol / L, with a sensitivity of 3.35μM. The actual human urine sample analysis further demonstrated the accuracy and feasibility of the Dy-OSCN-based PEC platform. It is expected that this Dy-OSCN / FTO photoelectrochemical sensor will provide a new approach for rapid and non-invasive AA level assessment in human physical fitness monitoring and lay the foundation for further development of practical products. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the preparation process of Dy-OSCN / FTO photoelectric detection electrode according to an embodiment of the present invention.

[0043] Figure 2 Comparison of the linearity (R2) (A) and low concentration signal intensity (B) of the AA test at 630nm, 535nm, 465nm and 420nm for the Dy-OSCN / FTO electrode of the embodiment of the present invention at calcination temperatures of 300°C, 400°C and 500°C;

[0044] Figure 3 The UV diffuse reflectance measurements (A) and the corresponding Kubelka-Munk curves (B) of the Dy-OSCN / FTO electrode of the embodiment of the present invention at calcination temperatures of 150°C, 200°C, 300°C, 400°C and 500°C;

[0045] Figure 4This is a scanning electron microscope (SEM) image of a Dy-OSCN / FTO photoelectric detection electrode calcined at 400° C. according to an embodiment of the present invention;

[0046] Figure 5 This is a high-resolution transmission electron microscope (HRTEM) image of a Dy-OSCN / FTO photoelectric detection electrode calcined at 400° C. in an embodiment of the present invention;

[0047] Figure 6 The X-ray photoelectron spectroscopy (XPS) general spectrum (A) of the Dy-OSCN / FTO photoelectric detection electrode calcined at 400°C in an embodiment of the present invention, and the X-ray photoelectron spectroscopy (XPS) fine spectrum (BF) of the Dy-OSCN / FTO photoelectric detection electrode calcined at 400°C;

[0048] Figure 7 X-ray diffraction (XRD) test diagram (A) of the crystals cultured from the Dy6-SCN solution in the embodiment of the present invention, XRD test diagram of the Dy-OSCN / FTO photoelectric detection electrode calcined at 400°C and the clean FTO (B), and XRD test fine diagram of the Dy-OSCN / FTO photoelectric detection electrode calcined at 400°C and the clean FTO (C);

[0049] Figure 8 The ultraviolet diffuse reflection test diagram (A) and the corresponding Kubelka-Munk curve (B) of the Dy-OSCN / FTO photoelectric detection electrode calcined at 400° C. in an embodiment of the present invention;

[0050] Fig. 9 AA photo potential curve (A) of the photoelectric detection of the Dy-OSCN / FTO photoelectric detection electrode according to an embodiment of the present invention, and the corresponding linear equation curve (B);

[0051] Fig.10 This is a test diagram of AA parallel lines of photoelectric detection of the same Dy-OSCN / FTO photoelectric detection electrode in an embodiment of the present invention;

[0052] Fig.11 The Dy-OSCN / FTO photoelectric detection electrode of the present invention is for glucose, urea, fructose, uric acid, lactic acid, citric acid, proline, threonine, histidine, lysine and glutathione and H + , K + , Ca 2+ 、Na + Mg 2+ , Cl - 、NO3 - 、SO4 2- Interference test diagram;

[0053] Fig.12 This is a possible detection mechanism diagram of AA on the enzyme-free Dy-OSCN / FTOPEC electrode according to an embodiment of the present invention;

[0054] Fig.13 This is the infrared spectra of the Dy-OSCN / FTO photoelectric detection electrode according to the embodiment of the present invention and the Dy-OSCN / FTO photoelectric detection electrode after AA testing (without washing). DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The embodiments of the present invention and all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Example:

[0057] See also Figure 1-13 The preparation method of the photoelectrochemical sensor provided in this embodiment comprises the following steps:

[0058] (1) Preparation of [Dy6L2(μ3-OH)4(μ2-OH)2(SCN)8(H2O)4]·6CH3CN·2CH3OH·H2O(Dy6-SCN) solution: Dissolve 4,6-dihydrazinopyrimidine (0.1 mmol / L) and o-vanillin (0.2 mmol / L) in a 25 ml sample bottle containing a mixture of 5 ml methanol and 10 ml acetonitrile. Ultrasonicate until the solid is completely dissolved. Add 0.3 mmol / L triethylamine and 0.2 mmol / L Dy(SCN)3·6H2O in sequence, and ultrasonicate again until the solid is dissolved. Tighten and seal the lid, place in an oven and heat to 80°C for 4 h, then cool to room temperature, filter the solution, and wait until the clear [Dy6L2(μ3-OH)4(μ2-OH)2(SCN)8(H2O)4]·6CH3CN·2CH3OH·H2O is obtained.

[0059] (Dy6-SCN) solution.

[0060] (2) FTO pretreatment: Before preparing the electrode, the FTO slices were immersed in detergent water for 0.5 h and ultrasonically treated with 1 M NaOH for 0.5 h. They were then ultrasonically treated with ethanol for about 0.5 h and dried with nitrogen. The geometric area exposed to light on the FTO surface was 0.81 cm 2 .

[0061] (3) See Figure 1, Preparation of Dy-OSCN / FTO photoelectric detection electrode: Place 11 cleaned FTO (1.5*2.5cm) sheets face up in a φ=90mmol / L surface dish, and then add 10ml Dy6-SCN solution. Cover with a cover plate and place it on a stable horizontal laboratory table. Slowly evaporate the solvent. After the solvent evaporates, let it dry naturally. The Dy6-SCN / FTO electrode is prepared. Place Dy6-SCN / FTO in a tube furnace and heat it to 200℃, 300℃, 400℃ and 500℃ at a heating rate of 2℃ / min in a nitrogen atmosphere. Keep the temperature for 2h, and then cool it to room temperature. Dy-OSCN / FTO photoelectric detection electrode was prepared in this way.

[0062] (4) Photocurrent signal detection method: Based on the screening results of the sintering temperature and test wavelength of Dy-OSCN / FTO, the optimal detection conditions were determined. The parallelism of the same Dy-OSCN / FTO photoelectric detection electrode was measured using the optimal conditions: the Dy-OSCN / FTO photoelectric detection electrode with a sintering temperature of 400°C was placed in a self-made photoelectric detection cell, 2.5 ml of PBS solution was added, and a two-electrode detection system was formed with saturated calomel as the reference electrode. A 465 nm light source with a power of 10 W was used to continuously excite the light from the side at a fixed distance, and the open circuit potential-time (OCPT) technology of the electrochemical workstation was used to record the experimental data. After the potential signal is stable, add 1mmol / L 0.02ml twice, 1mmol / L 0.03ml twice, 1mmol / L 0.05ml twice, 1mmol / L 0.1ml, 10mmol / L 0.02ml, 10mmol / L 0.03ml, 10mmol / L0.05ml, 10mmol / L 0.1ml, 100mmol / L 0.02ml twice, 100mmol / L 0.03ml twice, 100mmol / L0.02ml, 100mmol / L 0.03ml, 100mmol / L 0.05ml three times, 100mmol / L 0.1ml of AA standard solution in turn, record the data, and repeat the experiment three times. Draw the standard curve and calculate the linear equation and relative correction factor with error analysis.

[0063] The method for applying the photoelectrochemical sensor to human urine detection comprises the following steps:

[0064] (5) Actual sample detection. Take actual urine samples of volunteers for recovery test. Place the Dy-OSCN / FTO photoelectric detection electrode with a sintering temperature of 400℃ into a self-made photoelectric detection cell, add 2.5ml PBS solution, and use saturated calomel as the reference electrode to form a two-electrode detection system. Use a 465nm light source with a power of 10W LED light source to continuously excite the light from the side at a fixed distance, and use the open circuit potential-time (OCPT) technology of the electrochemical workstation to record the experimental data. After the potential signal is stable, add AA (solvent: PBS) sample solution 0.025ml 10mmol / L twice, 0.05ml 10mmol / L twice, AA (solvent: actual urine sample) sample solution 0.075ml 10mmol / L twice, 0.1ml 10mmol / L, AA (solvent: PBS) sample solution 0.1ml 10mmol / L twice, record the photopotential data, and repeat the same operation three times. Use the obtained data to calculate the recovery rate and related data of PEC detection of AA.

[0065] Explanation of terms in the embodiments of the present invention: Composition of the photoelectrochemical sensing system: a sensor detection system consisting of an excitation light source (xenon lamp), a three-electrode system (Ag / AgCl, Pt wire and electrodes modified with photoelectric active materials serve as reference electrode, counter electrode and working electrode respectively), an electrolyte solution, and a signal receiver.

[0066] The advantages of the photopotential testing technology used in the present invention are: during the test process, almost no current flows through the electrode surface, no redox reaction occurs on the interface, no substances are consumed in the detection system and no new substances are generated, and the detection system is not damaged.

[0067] Ascorbic acid (vitamin C, AA for short) is an important water-soluble vitamin. For a long time, AA has been considered an important antioxidant that can effectively protect organisms from damage related to oxidative stress and plays a role in maintaining normal physiological functions in the human body. AA is widely involved in the human metabolic process. As an essential nutrient, it effectively promotes the synthesis of collagen and mucopolysaccharides and enhances the strength of blood vessels. In the absence of AA, scurvy can lead to hematopoietic dysfunction, resulting in muscle and visceral bleeding and even death. Among the many important molecules in clinical medicine, ascorbic acid (AA) has great biomedical value. Diseases such as scurvy, schizophrenia, and Parkinson's disease may be related to abnormal AA levels. Simple and early detection of AA molecules is of great significance in physiology, drug research, and disease diagnosis.

[0068] The above embodiment of the present invention provides an enzyme-free AA photoelectric potential detection system based on Dy6-SCN single crystal semiconductor material. Because Dy6-SCN single crystal semiconductor material has a regular structure, it is helpful for carrier separation and transmission inside the semiconductor under light excitation. After Dy6-SCN single crystal semiconductor material is modified to the electrode surface and sintered, the chemical properties are stable and not easy to photocorrode, which greatly improves the stability and repeatability of the detection. Using the photoelectric potential method for testing, almost no current flows through the electrode surface during the detection process, and no redox reaction occurs on the interface, thus avoiding the target substance and other substances in the electrochemical test from undergoing redox reactions, and will not consume the target molecules and other molecules in the system, and will not introduce new substances, and the entire system will not be damaged. Because the photoelectric potential detection method has the above-mentioned many advantages, the use of Dy6-SCN single crystal semiconductor material to achieve low-cost, fast and accurate testing of AA provides a new idea for the detection of human life substance molecules. For this reason, the present invention proposes a method for preparing the photoelectric chemical sensor and a method for using the sensor to detect human urine.

[0069] The following is an explanation of the drawings of the embodiments of the present invention:

[0070] Figure 2 and Figure 3 The preparation conditions and test parameters of Dy-OSCN / FTO electrode were screened, and finally it was found that the linearity of Dy-OSCN / FTO calcined at 400°C under 465nm light response to AA was the best.

[0071] Figure 4-8 The successful synthesis of Dy-OSCN single crystals was demonstrated.

[0072] Fig. 9 It is a performance test of Dy-OSCN / FTO electrode. In the range of 7.94μM-13.71mmol / L, the photopotential signal decreases with the increase of the target concentration in the system, and the detection potential and the target concentration show a good three-segment linear relationship (R 2 =0.9907, R 2 =0.9953, R 2 =0.9988). The calculated limit of detection (LOD) was 3.35 μM. The results showed that the constructed enzyme-free Dy-OSCN / FTO photoelectric semiconductor electrode exhibited good PEC performance for AA in a good concentration range and had high sensitivity.

[0073] Fig.10The purpose is to investigate the stability of the Dy-OSCN / FTO photoelectric detection electrode after sintering at 400°C. When the same Dy-OSCN / FTO photoelectric detection electrode is used to detect the same concentration of AA samples, the signal difference is not significant, and the RSD is -0.034%. After the same electrode is repeated three times, the potential signal difference changes little, indicating that the electrode has good stability.

[0074] Fig.11 In order to measure the specificity and selectivity of Dy-OSCN / FTO photoelectric detection electrode sintered at 400℃ for AA detection, the most common coexisting biomolecules and inorganic ions in human urine were used as interference factors. Glucose 200 times the concentration of AA, fructose 200 times, urea 20 times, uric acid 20 times, lactic acid 20 times, citric acid 20 times, proline 20 times, threonine 20 times, histidine 20 times, lysine 20 times, glutathione 200 times, K + , 200 times the Ca 2+ , 200 times of Na + , 20 times the Mg 2+ , 200 times Na2SO4, record the potential change after adding AA standard solution and the potential change before and after adding interference, and repeat each experiment three times. Calculate the error caused by interference on the detection based on the recorded data. The change in detection potential is less than 15% of the AA standard solution signal, which means that they have little effect on AA recognition and analysis on the Dy-OSCN / FTO photoelectric detection electrode after sintering at 400℃, indicating that the PEC sensor has good specificity.

[0075] The embodiment of the present invention uses Dy6-SCN to modify the FTO electrode, and successfully establishes a new photoelectrochemical potential measurement system based on the Dy-OSCN / FTO electrode after sintering. And the Dy-OSCN / FTO photoelectric test electrode is successfully applied to the determination of enzyme-free AA in human urine, and a label-free AA sensor is successfully developed using a dysprosium single crystal photoelectric potential measurement device. The Dy-OSCN / FTO photoelectric test electrode was characterized by TEM, SEM, XPS, XRD, Ultraviolet diffuse reflection and IR test methods, and the results also verified that the electrode was successfully prepared. The Dy-OSCN / FTO photoelectric test electrode showed good performance in the AAPEC test, with a linear range of 7.94μM-13.71mmol / L, a detection limit as low as 3.35μM, and good stability and repeatability of multiple measurements of a single electrode. The open circuit potential technique is used to record the photopotential of the system under illumination. The Dy-OSCN / FTO electrode photoelectrochemical sensor also has good selectivity and anti-interference performance for AA, and the effectiveness of the sensor has also been verified. According to the Fermi level theory, charge balance theory, and previous calculations and experimental verifications, the mechanism formula is derived, which lays a theoretical foundation for the rationality of this strategy. Starting from the structure of the electrode material and the target molecule, it is speculated that the possible detection mechanism is that the AA molecule is specifically adsorbed and bonded to the single crystal photoelectric semiconductor material. In this process, the change in the amount of charge on the interface causes the change in the internal energy band bending of the semiconductor, causing the change in the photopotential measurement value. From the infrared spectrum test results, it was found that some peaks of the single crystal semiconductor material after the AA test were significantly moved. In this way, the rationality of the guessed mechanism is proved theoretically and in actual measurement. Good results were also obtained in the test of the AAPEC recovery rate of actual human urine samples, verifying the use value of the Dy-OSCN / FTO photoelectric test electrode sensor. The Dy-OSCN / FTOPEC sensor is expected to be further used for rapid and non-invasive AA level assessment in human physical fitness monitoring. The present invention believes that the proposed Dy-OSCN / FTO sensor will open up a new way for rapid and non-invasive AA level assessment in human physical fitness monitoring. More importantly, the test method used in this work does not interfere with the detection system, which is conducive to the development of other sensors of the same type. For some optoelectronic semiconductors with poor photostability, they often undergo redox reactions during the detection process. If photoelectric detection can be performed without current, the degree of semiconductor redox during the detection process will be greatly reduced, so that the repeatability and stability of the electrode are guaranteed. The development of this detection method also brings hope for the application of these optoelectronic semiconductors with poor photostability in photoelectric detection.

[0076] The photoelectric chemical sensor preparation method and human urine detection method provided in the above embodiments of the present invention use a photopotential method that can perform AA detection in the absence of current, compared with the traditional potentiometric method, greatly reducing the oxidation-reduction of the semiconductor and the target during the detection process, thereby ensuring the repeatability and stability of the electrode.

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a photoelectrochemical sensor, characterized in that: The following steps are involved: Step 1: Dissolve 4,6-dihydrazinopyrimidine and o-vanillin in a mixture to obtain a solute, place the solute in a sample bottle, perform ultrasonic treatment until the solid is completely dissolved, add triethylamine and Dy(SCN)3·6H2O in sequence, perform ultrasonic treatment again until the solid is dissolved, tighten and seal the lid, place in an oven and heat to 80°C for 4 hours, then cool to room temperature, filter the solution, and wait until it becomes clear to obtain a Dy6-SCN solution; Step 2: Clean the FTO slices to obtain pre-treated FTO; Step 3: Take out the pretreated FTO, add Dy6-SCN solution, evaporate naturally, and obtain Dy6-SCN / FTO electrode; Step 4: Heat and cool the Dy6-SCN / FTO electrode to obtain a photoelectrochemical sensor. The preparation process of the photoelectrochemical sensor in the fourth step is as follows: S1: Place the Dy6-SCN / FTO electrode in a tube furnace; S2: In a nitrogen atmosphere, heat to 200°C, 300°C, 400°C and 500°C at a heating rate of 2°C / min, and maintain the temperature for 2h; S3: The room temperature is then cooled to normal temperature to obtain a photoelectrochemical sensor.

2. The method for preparing a photoelectrochemical sensor according to claim 1, characterized in that: The mixture in the first step is a mixture of methanol and acetonitrile.

3. The method for preparing a photoelectrochemical sensor according to claim 1, characterized in that: The FTO pretreatment in the second step includes the following: S1: Immerse the FTO slice in detergent water for 0.5 h; S2: sonication with 1 M NaOH for 0.5 h; S3: sonicate with ethanol for about 0.5 h and blow dry with nitrogen; S4: The geometric area exposed to light on the FTO surface is 0.81 cm 2 .

4. The method for preparing a photoelectrochemical sensor according to claim 1, characterized in that: The size of FTO slice is 1.5*2.5cm.

5. The method for preparing a photoelectrochemical sensor according to claim 1, characterized in that: The specific preparation steps of the Dy6-SCN / FTO electrode in the third step are as follows: S1: Place the pretreated FTO facing upward in a watch glass; S2: Add Dy6-SCN solution; S3: Cover the plate and place it on a stable horizontal laboratory table to evaporate the solvent. After the solvent evaporates, it is naturally air-dried. The Dy6-SCN / FTO electrode is prepared.

6. An application of the photoelectrochemical sensor according to any one of claims 1 to 5, characterized in that: Applying it to the detection of human urine includes the following steps: Step 1: Take an actual urine sample; Step 2: Place the Dy6-SCN / FTO electrode sintered at 400°C into the photoelectric detection cell, add 2.5 ml of PBS solution, and use saturated calomel as the reference electrode to form a two-electrode detection system; Step 3: Use 465nm light and 10W LED light source to continuously excite the light from the side at a fixed distance, and use the open circuit potential-time technology of the electrochemical workstation to record the experimental data; Step 4: After the potential signal is stable, add 0.025ml 10mmol / L PBS sample solution twice, 0.05ml 10mmol / L twice, 0.075ml 10mmol / L urine actual sample solution twice, 0.1ml 10mmol / L, and 0.1ml 10mmol / L PBS sample solution twice, record the photopotential data, repeat the same operation three times, and use the obtained data to calculate the recovery rate and related data of PEC detection of AA.

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