A self-cleaning photoelectrochemical sensor based on signal polarity inversion

Abstract

This invention belongs to the field of photoelectrochemical sensor technology, specifically relating to a self-cleaning photoelectrochemical sensor based on wavelength-controlled photocurrent signal polarity reversal. Traditional PEC sensors, after completing the qualitative and quantitative detection of TC in the sample, cannot remove the target analytes trapped at the working electrode interface, requiring replacement of the working electrode. To address this problem, this invention provides a self-cleaning photoelectrochemical sensor based on signal polarity reversal. A wide-bandgap semiconductor / CDs / MOFs ternary nanocomposite is prepared using TiO2, CDs, and PCN-224 as raw materials. This composite is coated onto the electrode surface as a photoactive material, and a molecularly imprinted thin film with specific recognition effects is then deposited on its surface, forming the working electrode of the PEC sensor. By changing the excitation wavelength range, the polarity reversal of the photocurrent of the working electrode obtained by this invention is controlled by wavelength. This achieves both sensitive detection of the target analytes and self-cleaning of the working electrode surface, allowing the working electrode to be reused, resulting in significant technical advantages.

Description

Technical Field

[0001] This invention belongs to the field of tetracycline antibiotic detection technology, specifically relating to a self-cleaning photoelectrochemical sensor based on signal polarity reversal. Background Technology

[0002] Tetracycline (TC) is a broad-spectrum antibacterial drug with bactericidal effects at high concentrations, and is therefore widely used in agriculture and livestock farming to prevent animal diseases and promote animal growth. However, nearly 80% of TC cannot be effectively absorbed by animals and subsequently diffuses into the surrounding environment through livestock wastewater, accumulating in the human body through the food chain and ultimately posing a threat to human health. Therefore, accurate and sensitive detection of livestock wastewater, a major source of TC pollution, is of great significance. Currently, methods for detecting TC mainly include high-performance liquid chromatography-mass spectrometry (HPLC-MS) and ultraviolet spectrophotometry, but these methods are costly and have low sensitivity, making them unsuitable for real-time on-site detection.

[0003] Photoelectrochemical (PEC) sensing is an emerging analytical detection method that has gained wider attention in practical applications due to its high sensitivity, ease of operation, and miniaturization. PEC sensors combine electrochemical detection with photoexcitation, relying on the photoelectric conversion properties of photoactive materials to quantitatively or qualitatively detect the content of analytes.

[0004] Studies have shown that molecularly imprinted photoelectrochemical sensors can achieve specific detection of TC in samples. For example, Chinese invention patent CN113406168A discloses a photoelectrochemical sensor whose working electrode is a Uio-66-CDs / GCE modified electrode. This Uio-66-CDs / GCE modified electrode comprises a glassy carbon electrode and a composite of a metal-organic framework Uio-66 and carbon quantum dots CDs coated on the surface of the glassy carbon electrode. A chloramphenicol molecularly imprinted polymer film is also modified on the interface of the Uio-66-CDs / GCE modified electrode. This photoelectrochemical sensor can achieve qualitative and quantitative detection of TC in the sample, exhibiting good selectivity, high sensitivity, fast detection speed, and ease of use. However, with traditional PEC sensors like the one described above, the working electrode cannot be reused after qualitative and quantitative detection of TC in the sample, requiring replacement with a new electrode, increasing the cost.

[0005] This invention prepares a ternary nanocomposite based on titanium dioxide (TiO2), carbon dots (CDs), and porphyrin-based metal-organic framework (PCN-224) via an in-situ solvothermal method. This composite is coated onto the electrode surface as a photoactive material, and then covered with a molecularly imprinted polymer (MIP) film with characteristic recognition capabilities, forming the working electrode of a PEC sensor. TiO2, a semiconductor material, exhibits good light absorption only in the ultraviolet region, while carbon dots and PCN-224 possess broad-spectrum absorption properties. Therefore, the ternary nanocomposite synthesized in this invention will express photocurrent signals of opposite polarity under selective wavelength light excitation. Under visible light irradiation, since TiO2 cannot be excited, the photogenerated electrons generated by the ternary nanocomposite will transfer towards the electrolyte, exhibiting a cathodic photocurrent signal. When TC molecules are trapped in the cavity of the MIP film, the electron transfer channel is blocked due to the cavity occupancy, thus exhibiting a weakened cathodic photocurrent signal. Utilizing the linear relationship between TC concentration and cathodic photocurrent signal, accurate quantitative analysis of TC in unknown samples can be achieved. Under full-spectrum irradiation, titanium dioxide (TiO2), carbon dots (CDs), and porphyrin-based metal-organic frameworks (PCN-224) are all excited. At this time, the photogenerated electrons generated by the nano-ternary composite will transfer to the external circuit. The TC molecules trapped in the cavity of the MIP film will consume the photogenerated holes, accelerating the separation of photogenerated electron-hole pairs, thus exhibiting an enhanced anodic photoelectric signal. Once the TC trapped in the template molecule cavity in the MIP film is completely oxidized, it can be reused as a new working electrode.

[0006] As can be seen, by changing the excitation wavelength range, the present invention controls the polarity reversal of the photocurrent of the working electrode obtained by the present invention through wavelength regulation, thereby achieving self-cleaning of the working electrode surface, making the working electrode reusable, and achieving significant technical effects. Summary of the Invention

[0007] A problem with existing technologies is that the working electrode of traditional PEC sensors cannot be reused after qualitative and quantitative detection of TC in the sample, requiring replacement with a new electrode. To address this issue, this invention provides a self-cleaning photoelectrochemical sensor based on signal polarity reversal, comprising a working electrode formed by sequentially and uniformly modifying the electrode surface with a ternary nanocomposite material and MIPs. The ternary nanocomposite material is composed of a wide-bandgap semiconductor material, fluorescent carbon quantum dots (CDs), and MOFs through a solvothermal composite method.

[0008] Specifically, the wide bandgap semiconductor material can only be excited in the ultraviolet wavelength range of 200-400 nm.

[0009] Specifically, the method for preparing the working electrode includes the following steps:

[0010] (1) CDs were prepared by high-pressure solvothermal method;

[0011] (2) Using a solvothermal method, wide bandgap semiconductor materials and CDs are added to the raw materials for preparing MOFs materials, and heated and blended to form a wide bandgap semiconductor / CDs / MOFs nano ternary composite material;

[0012] (3) Wide bandgap semiconductor / CDs / MOFs nano-ternary composite material was modified onto a clean electrode interface to obtain wide bandgap semiconductor / CDs / MOFs modified electrode I;

[0013] (4) Then, a MIPs film is modified on the interface of the wide bandgap semiconductor / CDs / MOFs modified electrode I, and the template molecules in the MIPs film are removed to obtain the MIP / semiconductor / CDs / MOFs modified electrode II, which is the working electrode.

[0014] Specifically, the semiconductor material in the MIP / wide bandgap semiconductor / CDs / MOFs modified electrode II includes at least one of TiO2 and ZnO.

[0015] Specifically, the MOF material in the MIP / wide bandgap semiconductor / CDs / MOFs modified electrode II is PCN-224.

[0016] Specifically, the preparation method of MIP / TiO2 / CDs / PCN-224 modified electrode II includes the following steps:

[0017] (1) Preparation of TiO2 nanospheres

[0018] Triethylenediamine (TEDA) was dissolved in isopropanol (IPA), and the mixture was stirred under a nitrogen atmosphere to remove oxygen. Titanium isopropoxide (TIP) was then rapidly added to the solution and mixed thoroughly. The ratio of TEDA to IPA to TIP was 20 mg:35 mL:1.5 mL. The resulting solution was placed in a high-pressure reactor and sealed. A solvothermal reaction was then carried out in an oven at 200-240°C for 24 hours. After the solvothermal reaction was complete, the reaction product was centrifuged and washed, and the white solid precipitate was collected, dried, and calcined in a tube furnace at 400-600°C for 2-3 hours. The heating rate was 2-5°C / min, and the cooling rate was 5°C / min.

[0019] After calcination at a rate of 1000 m / min, a white solid powder, namely TiO2 nanospheres, was obtained.

[0020] (2) Preparation of TiO2 / CDs / PCN-224 nano-ternary composite material

[0021] a. Weigh out TiO2 nanospheres and ultrasonically disperse them in DMF to obtain a suspension. Add ZrOCl2·8H2O to the above suspension and stir evenly. Then add CDs and stir evenly. Transfer the mixture to a three-necked flask and label it as suspension A. The ratio of TiO2 nanospheres to DMF, ZrOCl2·8H2O and CDs is 500mg:20mL:150mg:2-10mg.

[0022] b. Dissolve 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (H2TCPP) and benzoic acid (BA) in DMF by ultrasonication to obtain solutions B and C. The ratio of H2TCPP to DMF is 50-100 mg:10 mL, and the ratio of BA to DMF is 1-3 g:20 mL.

[0023] c. While stirring, solutions B and C are added sequentially to suspension A to obtain a uniformly mixed suspension. The volume ratio of suspension A to solutions B and C is 2:1:1-2. Then, the suspension is transferred to an oil bath at 90-120°C and heated for 5 hours. After cooling to room temperature, the reaction product is centrifuged, washed, dried, and ground to obtain TiO2 / CDs / PCN-224 nano-ternary composite material.

[0024] (3) Preparation of MIP / TiO2 / CDs / PCN-224 modified electrode II

[0025] d. The TiO2 / CDs / PCN-224 nano-ternary composite material was dispersed in ultrapure water to obtain a TiO2 / CDs / PCN-224 dispersion. The mass concentration of the TiO2 / CDs / PCN-224 nano-ternary composite material in water was 1-4 mg / mL. An appropriate amount of TiO2 / CDs / PCN-224 dispersion was drop-coated onto a clean electrode surface and allowed to air dry naturally to obtain a TiO2 / CDs / PCN-224 modified electrode.

[0026] e. An appropriate amount of molecularly imprinted polymer precursor solution is modified onto the interface of TiO2 / CDs / PCN-224 modified electrode by UV-induced photopolymerization to obtain a MIPs film. The template molecules in the MIPs film are then removed using an eluent to obtain MIP / TiO2 / CDs / PCN-224 modified electrode II.

[0027] Specifically, the molecularly imprinted polymer precursor solution comprises, by mass parts, the following components:

[0028]

[0029] Specifically, the functional monomers include, but are not limited to, at least one of methacrylic acid (MAA) and acrylamide (ACR).

[0030] Specifically, the crosslinking agent is of the methacrylate type, including but not limited to at least one of ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA), and glycidyl methacrylate (GMA).

[0031] Specifically, the photoinitiator is a free radical type I photoinitiator, including but not limited to at least one of azobisisobutyronitrile (AIBN), phosphine oxide (TPO), and Irgacure 369.

[0032] Specifically, the template molecule includes, but is not limited to, at least one of tetracycline, oxytetracycline, and chlortetracycline, which can enable the identification of different target substances.

[0033] Specifically, the solvent includes, but is not limited to, at least one of methanol, acetonitrile, and N,N-dimethylformamide (DMF).

[0034] Specifically, the eluent in the elution process is a mixed solution of methanol and acetic acid in a volume ratio of 8-9:1-2.

[0035] Specifically, the method for preparing the CDs includes the following steps:

[0036] Anhydrous citric acid and urea are mixed and dissolved in a solvent in a certain proportion. After complete dissolution, the mixture is transferred to a high-pressure reactor for solvent heat treatment. After the reaction is completed, the mixture is cooled to room temperature, and the product is centrifuged, washed, and finally freeze-dried to obtain a black solid powder, which is CDs.

[0037] Specifically, the ratio of anhydrous citric acid to urea and DMSO is 2g:4-6g:30mL.

[0038] Specifically, the temperature of the solvothermal treatment process is 150-200℃, and the time is 4-5 hours.

[0039] Specifically, the solvent includes, but is not limited to, at least one of DMSO, DMF, ethanol, and glycerol.

[0040] The present invention has the following beneficial effects:

[0041] This invention uses TiO2, CDs, and PCN-224 as raw materials to prepare a wide-bandgap semiconductor / CDs / MOFs ternary nanocomposite. This composite is coated onto the electrode surface as a photoactive material, and then covered with a MIP film with characteristic recognition effect to form the working electrode of the PEC sensor. By changing the excitation wavelength range, the polarity reversal of the photocurrent of the working electrode obtained by this invention can be controlled by wavelength. This not only enables qualitative and quantitative analysis of TC in unknown samples, but also quickly achieves self-cleaning of the working electrode surface, allowing the working electrode to be reused. After being reused 5 times, the error of the detected photocurrent signal is less than 2.0%, which basically does not affect the accuracy of the working electrode's reusability, resulting in significant technical effects.

[0042] Instruction manual illustrations

[0043] Figure 1 The standard curve was plotted using the MIP / TiO2 / CDs / PCN-224 / ITO electrode incubated in Example 1 as the working electrode.

[0044] Figure 2 A, Scanning electron microscopy of TiO2 / CDs / PCN-224 nano-ternary composite material; B, High-resolution transmission electron microscopy of TiO2 / CDs / PCN-224 nano-ternary composite material. Detailed implementation method:

[0045] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0046] The CDs in the following embodiments of the present invention are prepared by the following methods:

[0047] Anhydrous citric acid and urea were mixed and dissolved in DMSO in a certain ratio of 2g:4g:30mL. After complete dissolution, the mixture was transferred to a high-pressure reactor for solvothermal treatment at 160℃ for 5 hours. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, washed three times with ethanol, and finally freeze-dried in a vacuum freeze-drying oven for 12 hours. The resulting black solid powder was CDs.

[0048] The molecularly imprinted polymer precursor solutions in the following embodiments of the present invention have the following composition, by mass parts:

[0049]

[0050] In the following embodiments of the present invention, the ultraviolet-induced photopolymerization uses a 365nm ultraviolet point light source (7W) and the polymerization time is 3min.

[0051] The working area of ​​the ITO electrode used in the following embodiments of the present invention is 0.2826 cm². 2 A circular area.

[0052] The pretreatment method for the ITO electrode in the following embodiments of the present invention is as follows:

[0053] The indium tin oxide (ITO) glass electrode was cut into 2×1cm sizes. After the electrode surface was activated by boiling in 1M NaOH for 20-30 minutes, it was then ultrasonically cleaned in ethanol and water in sequence, and dried for later use, thus obtaining the pretreated ITO electrode.

[0054] The error calculation formula in the following embodiments of the present invention is as follows:

[0055] Error = ((Test value of OTC concentration in the sample solution - True value of OTC concentration in the sample solution) / True value of OTC concentration in the sample solution) × 100%.

[0056] The high-pressure reactor in the following embodiments of the present invention is a high-pressure reactor with a Teflon liner.

[0057] Example 1

[0058] A self-cleaning photoelectrochemical sensor based on signal polarity reversal is disclosed, and its working electrode is prepared as follows:

[0059] (1) Preparation of TiO2 nanospheres

[0060] TEDA was dissolved in IPA, and oxygen was removed by stirring under a nitrogen atmosphere. Then, TIP was quickly added to the solution and mixed evenly. The ratio of TEDA to IPA and TIP was 20 mg: 35 mL: 1.5 mL. The resulting solution was placed in a 50 mL high-pressure reactor and sealed. Then, it was placed in an oven for solvothermal reaction at 200 °C for 24 h. After the solvothermal reaction was completed, the reaction product was centrifuged and washed three times with ethanol. The white solid precipitate was collected, dried, and calcined in a tube furnace at 400 °C for 2 h. The heating rate was 2 °C / min and the cooling rate was 5 °C / min. After calcination, a white solid powder, namely TiO2 nanospheres, was obtained.

[0061] (2) Preparation of TiO2 / CDs / PCN-224 nano-ternary composite material (Scanning electron microscope and high-resolution transmission electron microscope of the obtained material are shown in the attached instructions) Figure 2 (As shown)

[0062] a. Weigh out TiO2 nanospheres and ultrasonically disperse them in DMF to obtain a suspension. Add ZrOCl2·8H2O to the above suspension and stir evenly. Then add CDs and stir evenly. Transfer the mixture to a three-necked flask and label it as suspension A. The ratio of TiO2 nanospheres to DMF, ZrOCl2·8H2O and CDs is 500mg:20mL:150mg:2mg.

[0063] b. Dissolve H2TCPP and BA in DMF by ultrasonication to obtain solution B and solution C. The ratio of H2TCPP to DMF is 50mg:10mL, and the ratio of BA to DMF is 1g:20mL.

[0064] c. While stirring, solutions B and C are added sequentially to suspension A to obtain a uniformly mixed suspension. The volume ratio of suspension A to solutions B and C is 2:1:1. Then, the mixture is transferred to an oil bath at 90°C and heated for 5 hours. After cooling to room temperature, the reaction product is centrifuged, washed three times with DMF, and washed twice with acetone. After drying at 60°C, TiO2 / CDs / PCN-224 nano-ternary composite material is obtained.

[0065] (3) Preparation of MIP / TiO2 / CDs / PCN-224 modified electrode II

[0066] d. The TiO2 / CDs / PCN-224 nano-ternary composite material was dispersed in ultrapure water to obtain a TiO2 / CDs / PCN-224 dispersion. The mass concentration of the TiO2 / CDs / PCN-224 nano-ternary composite material in water was 3 mg / mL. 20 μL of the TiO2 / CDs / PCN-224 dispersion was uniformly drop-coated onto the surface of the pretreated ITO electrode. After air drying, a TiO2 / CDs / PCN-224 modified electrode was obtained.

[0067] e. A 3 μL molecularly imprinted polymer precursor solution was modified onto the interface of a TiO2 / CDs / PCN-224 modified ITO electrode by UV-induced photopolymerization to obtain a MIPs film. The template molecules in the MIPs film were then removed using an eluent to obtain the MIP / TiO2 / CDs / PCN-224 modified electrode II. The eluent was a mixed solution of methanol and acetic acid in a volume ratio of 9:1, and the elution time was 30 min.

[0068] Example 2

[0069] A self-cleaning photoelectrochemical sensor based on signal polarity reversal is disclosed, and its working electrode is prepared as follows:

[0070] (1) Preparation of TiO2 nanospheres

[0071] TEDA was dissolved in IPA, and oxygen was removed by stirring under a nitrogen atmosphere. Then, TIP was quickly added to the solution and mixed evenly. The ratio of TEDA to IPA and TIP was 20 mg: 35 mL: 1.5 mL. The resulting solution was placed in a high-pressure reactor and sealed. Then, it was placed in an oven for solvothermal reaction at 220°C for 24 h. After the solvothermal reaction was completed, the reaction product was centrifuged and washed three times with ethanol. The white solid precipitate was collected, dried, and then calcined in a tube furnace at 500°C for 3 h. The heating rate was 3°C / min and the cooling rate was 5°C / min. After calcination, a white solid powder, namely TiO2 nanospheres, was obtained.

[0072] (2) Preparation of TiO2 / CDs / PCN-224 nano-ternary composite material

[0073] a. Weigh out TiO2 nanospheres and ultrasonically disperse them in DMF to obtain a suspension. Add ZrOCl2·8H2O to the above suspension and stir evenly. Then add CDs and stir evenly. Transfer the mixture to a three-necked flask and label it as suspension A. The ratio of TiO2 nanospheres to DMF, ZrOCl2·8H2O and CDs is 500mg:20mL:150mg:5mg.

[0074] b. Dissolve H2TCPP and BA in DMF by ultrasonication to obtain solution B and solution C. The ratio of H2TCPP to DMF is 70mg:10mL, and the ratio of BA to DMF is 2g:20mL.

[0075] c. While stirring, solutions B and C are added sequentially to suspension A to obtain a uniformly mixed suspension. The volume ratio of suspension A to solutions B and C is 2:1:1.5. Then, the mixture is transferred to an oil bath at 100°C and heated for 5 hours. After cooling to room temperature, the reaction product is centrifuged, washed three times with DMF, and washed twice with acetone. After drying at 60°C, TiO2 / CDs / PCN-224 nano-ternary composite material is obtained.

[0076] (3) Preparation of MIP / TiO2 / CDs / PCN-224 modified electrode II

[0077] d. The TiO2 / CDs / PCN-224 nano-ternary composite material was dispersed in ultrapure water to obtain a TiO2 / CDs / PCN-224 dispersion. The mass concentration of the TiO2 / CDs / PCN-224 nano-ternary composite material in water was 3 mg / mL. 20 μL of the TiO2 / CDs / PCN-224 dispersion was uniformly drop-coated onto the surface of the pretreated ITO electrode. After air drying, a TiO2 / CDs / PCN-224 modified electrode was obtained.

[0078] e. A 3 μL molecularly imprinted polymer precursor solution was modified onto the interface of a TiO2 / CDs / PCN-224 modified ITO electrode by UV-induced photopolymerization to obtain a MIPs film. The template molecules in the MIPs film were then removed using an eluent to obtain the MIP / TiO2 / CDs / PCN-224 modified electrode II. The eluent was a mixed solution of methanol and acetic acid in a volume ratio of 8:2, and the elution time was 30 min.

[0079] Example 3

[0080] A self-cleaning photoelectrochemical sensor based on signal polarity reversal is disclosed, and its working electrode is prepared as follows:

[0081] (1) Preparation of TiO2 nanospheres

[0082] TEDA was dissolved in IPA, and oxygen was removed by stirring under a nitrogen atmosphere. Then, TIP was quickly added to the solution and mixed evenly. The ratio of TEDA to IPA and TIP was 20 mg: 35 mL: 1.5 mL. The resulting solution was placed in a high-pressure reactor and sealed. Then, it was placed in an oven for solvothermal reaction at 240°C for 24 h. After the solvothermal reaction was completed, the reaction product was centrifuged and washed three times with ethanol. The white solid precipitate was collected, dried, and then calcined in a tube furnace at 600°C for 3 h. The heating rate was 5°C / min, and the cooling rate was 5°C / min. After calcination, a white solid powder, namely TiO2 nanospheres, was obtained.

[0083] (2) Preparation of TiO2 / CDs / PCN-224 nano-ternary composite material

[0084] a. Weigh out TiO2 nanospheres and ultrasonically disperse them in DMF to obtain a suspension. Add ZrOCl2·8H2O to the above suspension and stir evenly. Then add CDs and stir evenly. Transfer the mixture to a three-necked flask and label it as suspension A. The ratio of TiO2 nanospheres to DMF, ZrOCl2·8H2O and CDs is 500mg:20mL:150mg:10mg.

[0085] b. Dissolve H2TCPP and BA in DMF by ultrasonication to obtain solution B and solution C. The ratio of H2TCPP to DMF is 100mg:10mL, and the ratio of BA to DMF is 3g:20mL.

[0086] c. While stirring, solutions B and C are added sequentially to suspension A to obtain a uniformly mixed suspension. The volume ratio of suspension A to solutions B and C is 2:1:2. Then, the mixture is transferred to an oil bath at 120°C and heated for 5 hours. After cooling to room temperature, the reaction product is centrifuged, washed three times with DMF, and washed twice with acetone. After drying at 60°C, TiO2 / CDs / PCN-224 nano-ternary composite material is obtained.

[0087] (3) Preparation of MIP / TiO2 / CDs / PCN-224 modified electrode II

[0088] d. The TiO2 / CDs / PCN-224 nano-ternary composite material was dispersed in ultrapure water to obtain a TiO2 / CDs / PCN-224 dispersion. The mass concentration of the TiO2 / CDs / PCN-224 nano-ternary composite material in water was 3 mg / mL. 20 μL of the TiO2 / CDs / PCN-224 dispersion was uniformly drop-coated onto the surface of the pretreated ITO electrode. After air drying, a TiO2 / CDs / PCN-224 modified electrode was obtained.

[0089] e. A 3 μL molecularly imprinted polymer precursor solution was modified onto the interface of a TiO2 / CDs / PCN-224 modified ITO electrode by UV-induced photopolymerization to obtain a MIPs film. The template molecules in the MIPs film were then removed using an eluent to obtain the MIP / TiO2 / CDs / PCN-224 modified electrode II. The eluent was a mixed solution of methanol and acetic acid in a volume ratio of 9:1, and the elution time was 30 min.

[0090] Comparative Example 1 is the same as Example 1, except that the CDs preparation method in Comparative Example 1 is as follows:

[0091] Citric acid and ethylenediamine were added to water, mixed and dissolved, and then transferred to a high-pressure reactor. The mixture was reacted at a certain temperature for a period of time. After the reactor cooled to room temperature, the resulting yellow liquid was filtered to obtain a carbon dot solution. The ratio of citric acid, ethylenediamine, and water was 0.42 g:0.536 mL:10 mL; the specified temperature was 200 °C, and the reaction time was 5 h; filtration was performed using a 0.22 μm aqueous membrane.

[0092] Comparative Example 2 is the same as Example 1, except that the CDs preparation method in Comparative Example 2 is as follows:

[0093] Add 1.00 g of citric acid and 1.00 g of urea to 10.0 mL of water and stir until the materials are completely dissolved. Then, react the above solution in an 800 W microwave oven for about 3 minutes. The clear solution gradually turns yellow, then brown. When the water finally evaporates, a black solid is formed. Dissolve the resulting CDs in water and centrifuge at 12000 rpm for 30 minutes to remove suspended impurities, thus obtaining the CDs solution.

[0094] Specific applications

[0095] (1) The MIP / TiO2 / CDs / PCN-224 modified electrode II obtained in Examples 1-3 and Comparative Examples 1-2 were used as working electrodes for incubation. A saturated Ag / AgCl electrode was used as the reference electrode, a platinum wire as the counter electrode, and 0.01M PBS buffer solution as the electrolyte to construct different three-electrode PEC sensors. Under visible light irradiation (using a filter to remove the ultraviolet wavelength of the xenon lamp) and a bias voltage of -0.3V, the PEC signal was recorded and detected using a CHI660E workstation. Standard curves were plotted based on the linear relationship between the cathode photocurrent signal and the logarithm of the TC concentration. The detection range of the cathode TC concentration of the PEC sensor obtained in Examples 1-3 was 5.00 × 10⁻⁶. -13 -1.00×10 -8 M, with a detection limit as low as 3.75 × 10⁻⁶. -13 M. The MIP / TiO2 / CDs / PCN-224 / ITO electrode incubated in Example 1 was used as the working electrode, and the standard curve plotted is shown in the appendix to the instruction manual. Figure 1 As shown, the linear regression equation is I = 76.972lgC - 286.157, R0 2 =0.997.

[0096] The incubation method is as follows:

[0097] The MIP / TiO2 / CDs / PCN-224 modified electrode II was immersed in TC solutions of different concentrations and incubated for 20 min, then air-dried to obtain the incubated MIP / TiO2 / CDs / PCN-224 / ITO. The different concentrations of TC solutions (using ultrapure water as the solvent) are as follows:

[0098] 5.0×10 -13 1.0×10 -12 5.0×10 -12 1.0×10 -11 5.0×10 -11 1.0×10 -10 5.0×10 -10 1.0×10-9 5.0×10 -9 1.0×10 -8 5.0×10 -8 1.0×10 -7 5.0×10 -7 1.0×10 -6 5.0×10 -6 1.0×10 -5 mol·L -1 .

[0099] (2) Self-cleaning of the working electrode surface

[0100] Using the MIP / TiO2 / CDs / PCN-224 modified electrode II obtained in Example 1 as the working electrode, at a concentration of 1.0 × 10⁻⁶... -9 After incubation in a TC solution of M, a three-electrode PEC sensor was constructed using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte. The PEC signal was recorded and detected by a CHI660E workstation under full-spectrum xenon lamp irradiation and a 0V bias voltage. After 600 seconds of reaction, the working electrode was removed, and the reaction was repeated in a 1.0×10⁻⁶ solution. -9 PEC sensors were incubated in a TC solution of M, using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte, forming different three-electrode systems. Irradiation with visible light (using a filter to remove the ultraviolet wavelength of the xenon lamp) and a bias voltage of -0.3V was performed, and the PEC photocurrent signal was recorded and detected using a CHI660E workstation. The detected photocurrent value was then input into the standard curve obtained in Example 1 to calculate the TC concentration, with an error of 0.9%. This process was repeated 5 times, with the detected photocurrent value input into the standard curve obtained in Example 1 to calculate the TC concentration, with an error of 1.5%.

[0101] Using the MIP / TiO2 / CDs / PCN-224 modified electrode II obtained in Example 2 as the working electrode, at a concentration of 1.0 × 10⁻⁶... -9 After incubation in a TC solution of M, a three-electrode PEC sensor was constructed using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte. The PEC signal was recorded and detected by a CHI660E workstation under full-spectrum xenon lamp irradiation and a 0V bias voltage. After 600 seconds of reaction, the working electrode was removed, and the reaction was repeated in a 1.0×10⁻⁶ solution. -9PEC sensors were incubated in a TC solution of M, using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte, forming different three-electrode systems. Under visible light irradiation (with a filter to remove the ultraviolet wavelength of the xenon lamp), and a bias voltage of -0.3V, the PEC photocurrent signal was recorded and detected using a CHI660E workstation. The detected photocurrent value was substituted into the standard curve obtained in Example 2 to calculate the TC concentration, with an error of 1.3%. This process was repeated 5 times, and the detected photocurrent value was substituted into the standard curve obtained in Example 1 to calculate the TC concentration, with an error of 1.7%.

[0102] Using the MIP / TiO2 / CDs / PCN-224 modified electrode II obtained in Example 3 as the working electrode, at a concentration of 1.0 × 10⁻⁶... -9 After incubation in a TC solution of M, a three-electrode PEC sensor was constructed using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte. The PEC signal was recorded and detected by a CHI660E workstation under full-spectrum xenon lamp irradiation and a 0V bias voltage. After 600 seconds of reaction, the working electrode was removed, and the reaction was repeated in a 1.0×10⁻⁶ solution. -9 PEC sensors were incubated in a TC solution of M, using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte, forming different three-electrode systems. Under visible light irradiation (with a filter to remove the ultraviolet wavelength of the xenon lamp) and a bias voltage of -0.3V, the PEC photocurrent signal was recorded and detected using a CHI660E workstation. The detected photocurrent value was substituted into the standard curve obtained in Example 3 to calculate the TC concentration, with an error of 1.4%. This process was repeated 5 times, and the detected photocurrent value was substituted into the standard curve obtained in Example 1 to calculate the TC concentration, with an error of 1.9%.

[0103] Using the MIP / TiO2 / CDs / PCN-224 modified electrode II obtained in Example 3 as the working electrode, at a concentration of 1.0 × 10⁻⁶... -9 After incubation in a TC solution of M, a three-electrode PEC sensor was constructed using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte. The PEC signal was recorded and detected by a CHI660E workstation under full-spectrum xenon lamp irradiation and a 0V bias voltage. After 600 seconds of reaction, the working electrode was removed, and the reaction was repeated in a 1.0×10⁻⁶ solution. -9PEC sensors were incubated in a TC solution of M, using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte, forming different three-electrode systems. Under visible light irradiation (with a filter to remove the ultraviolet wavelength of the xenon lamp) and a bias voltage of -0.3V, the PEC photocurrent signal was recorded and detected using a CHI660E workstation. The detected photocurrent value was substituted into the standard curve obtained in Example 3 to calculate the TC concentration, with an error of 1.1%. This process was repeated 5 times, and the detected photocurrent value was substituted into the standard curve obtained in Example 1 to calculate the TC concentration, with an error of 1.9%.

[0104] Using the MIP / TiO2 / CDs / PCN-224 modified electrode II obtained in Comparative Example 1 as the working electrode, at a concentration of 1.0 × 10⁻⁶... -9 After incubation in a TC solution of M, a three-electrode PEC sensor was constructed using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte. The PEC signal was recorded and detected by a CHI660E workstation under full-spectrum xenon lamp irradiation and a 0V bias voltage. After 600 seconds of reaction, the working electrode was removed, and the reaction was repeated in a 1.0×10⁻⁶ solution. -9 PEC sensors were incubated in a TC solution of M, using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte, forming different three-electrode systems. Irradiation with visible light (using a filter to remove the ultraviolet wavelength of the xenon lamp) and a bias voltage of -0.3V was performed, and the PEC photocurrent signal was recorded and detected using a CHI660E workstation. The detected photocurrent value was substituted into the standard curve obtained in Comparative Example 1 to calculate the TC concentration, with an error of 2.5%. The above steps were repeated 5 times, and the detected photocurrent value was substituted into the standard curve obtained in Example 1 to calculate the TC concentration, with an error of 2.9%.

[0105] Using the MIP / TiO2 / CDs / PCN-224 modified electrode II obtained in Comparative Example 2 as the working electrode, at a concentration of 1.0 × 10⁻⁶... -9 After incubation in a TC solution of M, a three-electrode PEC sensor was constructed using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte. The PEC signal was recorded and detected by a CHI660E workstation under full-spectrum xenon lamp irradiation and a 0V bias voltage. After 600 seconds of reaction, the working electrode was removed, and the reaction was repeated in a 1.0×10⁻⁶ solution. -9PEC sensors were incubated in a TC solution of M, using a saturated Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a 0.01M PBS buffer solution as the electrolyte, forming different three-electrode systems. Under visible light irradiation (with a filter to remove the ultraviolet wavelength of the xenon lamp) and a bias voltage of -0.3V, the PEC photocurrent signal was recorded and detected using a CHI660E workstation. The detected photocurrent value was substituted into the standard curve obtained in Comparative Example 2 to calculate the TC concentration, with an error of 2.4%. The above steps were repeated 5 times, and the detected photocurrent value was substituted into the standard curve obtained in Example 1 to calculate the TC concentration, with an error of 3.0%.

[0106] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A self-cleaning photoelectrochemical sensor based on signal polarity inversion, comprising a working electrode, characterized in that, The working electrode is formed by sequentially and uniformly modifying the electrode surface with a nano-ternary composite material and MIPs. The nano-ternary composite material is composed of a wide bandgap semiconductor material, fluorescent carbon quantum dots (CDs), and MOFs. The wide bandgap semiconductor material is TiO2; the MOF material is PCN-224; and the preparation steps of the nano-ternary composite material TiO2 / CDs / PCN-224 are as follows: (1) Preparation of TiO2 nanospheres TEDA was dissolved in IPA, and oxygen was removed by stirring under a nitrogen atmosphere. Then, TIP was quickly added to the solution and mixed evenly. The ratio of TEDA to IPA and TIP was 20 mg: 35 mL: 1-3 mL. The obtained solution was placed in a high-pressure reactor and sealed. Then, it was placed in an oven for solvothermal reaction at 200-240℃ for 24 h. After the solvothermal reaction was completed, the reaction product was centrifuged and washed, and the white solid precipitate was collected. After drying, it was placed in a tube furnace for calcination at 400-600℃ for 2-3 h. The heating rate was 2-5℃ / min, and the cooling rate was 5℃ / min. After calcination, a white solid powder, namely TiO2 nanospheres, was obtained. (2) Preparation of TiO2 / CDs / PCN-224 nano-ternary composite material a. Weigh out TiO2 nanospheres and ultrasonically disperse them in DMF to obtain a suspension. Add ZrOCl2·8H2O to the above suspension and stir evenly. Then add CDs and stir evenly. Transfer the mixture to a three-necked flask and label it as suspension A. The ratio of TiO2 nanospheres to DMF, ZrOCl2·8H2O and CDs is 500mg:20mL:150mg:2-10mg. b. Dissolve H2TCPP and BA in DMF by ultrasonication to obtain solution B and solution C. The ratio of H2TCPP to DMF is 50-100 mg: 10 mL, and the ratio of BA to DMF is 1-3 g: 20 mL. c. While stirring, solutions B and C are added sequentially to suspension A to obtain a uniformly mixed suspension. The volume ratio of suspension A to solutions B and C is 2:1:1-2. Then, the suspension is transferred to an oil bath at 90-120°C and heated for 5 hours. After cooling to room temperature, the reaction product is centrifuged, washed, dried, and ground to obtain the TiO2 / CDs / PCN-224 nano-ternary composite material. The wide bandgap semiconductor material TiO2 can only be excited in the ultraviolet wavelength range of 200-400 nm; By changing the excitation wavelength range, the photocurrent of the working electrode is polarized and reversed. Under visible light irradiation, a cathodic photocurrent is expressed for the detection of the target. Under full-spectrum irradiation, an enhanced anodic photocurrent is expressed to oxidize and remove the target captured in the molecularly imprinted film, thereby achieving self-cleaning and reuse of the working electrode surface.

2. The self-cleaning photoelectrochemical sensor based on signal polarity inversion according to claim 1, characterized in that, The method for preparing the working electrode includes the following steps: (1) CDs were prepared by high-pressure solvothermal method; (2) Using a solvothermal method, TiO2 and CDs are added to the raw materials for preparing PCN-224 and heated to form a TiO2 / CDs / PCN-224 nano-ternary composite material. (3) TiO2 / CDs / PCN-224 was applied to a clean electrode interface to obtain TiO2 / CDs / PCN-224 modified electrode I; (4) Then, a MIPs film is modified on the interface of TiO2 / CDs / PCN-224 modified electrode I, and the template molecules in the MIPs film are removed to obtain MIP / TiO2 / CDs / PCN-224 modified electrode II, which is the working electrode.

3. The self-cleaning photoelectrochemical sensor based on signal polarity inversion according to claim 2, characterized in that, The preparation method of MIP / TiO2 / CDs / PCN-224 modified electrode II includes the following steps: d. The TiO2 / CDs / PCN-224 nano-ternary composite material was dispersed in ultrapure water to obtain a TiO2 / CDs / PCN-224 dispersion. The mass concentration of the TiO2 / CDs / PCN-224 nano-ternary composite material in water was 1-4 mg / mL. An appropriate amount of TiO2 / CDs / PCN-224 dispersion was drop-coated onto a clean electrode surface and allowed to air dry naturally to obtain a TiO2 / CDs / PCN-224 modified electrode. e. An appropriate amount of molecularly imprinted polymer precursor solution is modified onto the interface of TiO2 / CDs / PCN-224 modified electrode by UV-induced photopolymerization to obtain a MIPs film. The template molecules in the MIPs film are then removed using an eluent to obtain MIP / TiO2 / CDs / PCN-224 modified electrode II.

4. The self-cleaning photoelectrochemical sensor based on signal polarity inversion according to claim 3, characterized in that, The molecularly imprinted polymer precursor solution comprises, by mass parts, the following components: 340-350 parts of functional monomer; 290-300 parts of crosslinking agent; 82-85 parts of photoinitiator; 27-30 parts of template molecule; 2000 parts of solvent.

5. The self-cleaning photoelectrochemical sensor based on signal polarity inversion according to claim 4, characterized in that, The template molecule includes at least one of tetracycline, oxytetracycline, and chlortetracycline.

6. The self-cleaning photoelectrochemical sensor based on signal polarity inversion according to claim 1, characterized in that, The method for preparing the CDs includes the following steps: Anhydrous citric acid and urea are mixed and dissolved in a solvent in a certain proportion. After complete dissolution, the mixture is transferred to a high-pressure reactor for solvent heat treatment. After the reaction is completed, the mixture is cooled to room temperature, and the product is centrifuged, washed, and finally freeze-dried to obtain a black solid powder, which is CDs.

7. The self-cleaning photoelectrochemical sensor based on signal polarity inversion according to claim 6, characterized in that, The ratio of anhydrous citric acid to urea and DMSO is 2g:4-6g:30mL.

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