Preparation method and application of molecularly imprinted cathode photoelectrochemical sensor based on CNQDs (at) CTP nanocomposite

Abstract

The invention belongs to the technical field of nano materials, photoelectrochemical sensing and analysis and environmental monitoring, and relates to a preparation method and application of a molecularly imprinted cathode photoelectrochemical sensor based on a CNQDs (at) CTP nano composite material. The invention firstly provides a preparation method for in-situ synthesis of a nano composite material of a covalent organic framework and graphite carbon nitride quantum dots, and a molecularly imprinted cathode photoelectrochemical sensor is constructed on the basis of the material in combination with a molecular imprinting technology, and has good selectivity, ion interference resistance, reproducibility and long-term stability. The sensor can be used for detecting PFOA in a water body, the sensitivity is high, the stability is good, the linear range is wide and is 1 * 10 <-11 >-5 * 10 <-6 > mol.L <-1 >, and the detection limit is 5.50 * 10 <-12 > mol.L <-1 >; the design thought provided by the invention can be used for developing a sensing method for detecting other target objects, and has a very good application prospect.

Description

Technical Field

[0001] The invention belongs to the multi-technical fields of nanomaterials, photoelectrochemical sensing and analysis, and environmental monitoring, and specifically relates to the preparation of a photoelectrically active nanocomposite CNQDs@CTP, the construction of a molecular imprinting photoelectrochemical sensor, and its application in agricultural water environment monitoring. Background Art

[0002] Perfluorooctanoic acid (PFOA) is a member of a class of perfluorinated compounds known as permanent chemicals, which has attracted great attention due to its unique chemical properties, wide range of uses and persistence in the environment. PFOA is widely present in surface water, groundwater, soil and atmosphere around the world due to its extremely high chemical stability and persistence, and is difficult to degrade. This compound can be transmitted in the food chain through the bioaccumulation effect, posing a potential threat to wildlife and human health, including endocrine disruption, reproductive disorders, immune system suppression and possible carcinogenicity, causing huge environmental and health problems. Therefore, it is necessary to develop accurate and sensitive detection of PFOA.

[0003] Currently available PFOA detection methods include gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), liquid chromatography-tandem mass spectrometry (LC-MS / MS) and photoelectrochemical (PEC) detection methods; among them, the photoelectrochemical (PEC) detection method has the advantages of high sensitivity and good selectivity, and its low cost, simple operation and easy miniaturization make it more promising in practical applications. The key to the performance of photoelectrochemical sensing analysis is that, on the one hand, the detection signal electrical signal comes from the absorption and conversion of light energy by the photosensitive material. Therefore, photosensitive materials with high photoelectric activity and stable performance are the basis for detection; on the other hand, how to avoid interference caused by complex components in the environment and achieve selective and specific response to the target PFOA is the key to complete detection.

[0004] Based on this, the present invention aims at the deficiencies of the prior art. On the basis of preparing a nanocomposite material CNQDs@CTP with high photoelectric activity and stability, it further combines the molecular imprinting technology (MIP) known as "artificial antibody" to finally achieve sensitive detection of PFOA in actual samples. Summary of the invention

[0005] The present invention aims to provide a method for preparing a nanocomposite material (CNQDs@CTP) of in-situ synthesized covalent organic framework (CTP) and graphite carbon nitride quantum dots (CNQDs), and to construct a photoelectrochemical sensor based on the material in combination with molecular imprinting technology, and to apply the sensor to the detection of PFOA content in water.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] 1. A method for preparing a CNQDs@CTP nanocomposite material, using trisodium citrate dihydrate and urea as the synthesis raw materials of CNQDs, using a mixed solution of p-phenylenediamine (Pa) and tetraaldehyde phenylporphyrin (TFPP) as the synthesis precursor of CTP, adding the synthesized CNQDs to the precursor solution of CTP, and stirring at room temperature to prepare a CNQDs@CTP nanocomposite material. Specifically comprising the following steps:

[0008] (1) Preparation of CNQDs:

[0009] First, sodium citrate dihydrate (Na3C6H5O7·2H2O) and urea (CH4N2O) were added to water, mixed and dissolved, and then transferred to a high-pressure reactor for reaction. After the reaction, the solution was cooled to room temperature, and the reaction solution was dialyzed and freeze-dried to obtain a blue graphite carbon nitride quantum dot solid, which was dissolved in water to obtain a graphite carbon nitride quantum dot solution, recorded as CNQDs solution;

[0010] (2) Preparation of CNQDs@CTP:

[0011] p-phenylenediamine (Pa) is added to acetonitrile (ACN) to obtain a p-phenylenediamine solution; tetraaldehyde phenylporphyrin (TFPP) is added to dichloromethane (CH2Cl2) to obtain a tetraaldehyde phenylporphyrin solution; ferric chloride hexahydrate (FeCl3·6H2O) is mixed with acetonitrile (ACN) to obtain a FeCl3 solution;

[0012] First, a p-phenylenediamine solution and a tetraaldehyde phenylporphyrin solution are mixed, and then FeCl3 solution, CH3COOH and the CNQDs solution prepared in step (1) are added. After being fully mixed by ultrasonication, the mixture is stirred at room temperature for reaction. After the reaction, the mixture is centrifuged, washed, dried and ground to obtain a black-brown powder solid, which is recorded as CNQDs@CTP.

[0013] Preferably, in step (1), the dosage ratio of sodium citrate dihydrate, urea and water is 1.63g:2g:100mL; the reaction temperature is 180°C, and the reaction time is 3h; the dialysis uses a 1000D dialysis bag, and the dialysis time is 6h; the concentration of the graphite carbon nitride quantum dot solution is 100mg / mL.

[0014] Preferably, in step (2), the dosage ratio of p-phenylenediamine, acetonitrile, tetraaldehyde phenylporphyrin, dichloromethane, ferric chloride hexahydrate, acetonitrile to CH3COOH solution and CNQDs solution is 5 mg:10 mL:5 mg:10 mL:16.67 mg:0.2 mL:5 mL:15 μL;

[0015] The stirring reaction speed at room temperature is 350-370 rpm, and the reaction time is 6 hours; the centrifugal condition is set to 10000 rpm, 5 minutes; washing is performed with ethanol for 3 times; the drying temperature is 60°C, and the time is 6-8 hours.

[0016] 2. A method for constructing a molecularly imprinted cathode photoelectrochemical sensor based on CNQDs@CTP nanocomposite materials, the steps are as follows:

[0017] (1) Preparation of molecular imprinting polymer solution:

[0018] PFOA and acrylamide (MA) were added to methanol, and the obtained mixed solution was oscillated and mixed evenly at a certain temperature. After nitrogen (N2) was passed through the mixed solution for a period of time, ethylene glycol dimethacrylate (EGDMA) was added to the solution. After nitrogen was passed through the solution for a period of time, an initiator azobisisobutyronitrile (AIBN) was added, and after ultrasonic dissolution, a molecular imprinting polymer solution was obtained, which was stored in a dark place.

[0019] (2) First, pre-treat indium tin oxide (ITO) conductive glass to obtain pre-treated ITO conductive glass; then add CNQDs@CTP into water to dissolve it to obtain a CNQDs@CTP dispersion; and drop the CNQDs@CTP dispersion onto the surface of the pre-treated ITO conductive glass, and dry it at room temperature. The dried product is recorded as CNQDs@CTP / ITO;

[0020] (3) adding the molecular imprinting polymerization solution prepared in step (1) to the surface of the CNQDs@CTP / ITO obtained in step (2), and forming a molecular imprinting film after thermal polymerization, thereby obtaining CNQDs@CTP / ITO containing a molecular imprinting film; placing the CNQDs@CTP / ITO containing a molecular imprinting film into an elution solution for elution, and drying it in the dark at room temperature after elution, thereby obtaining a molecular imprinting cathode photoelectrochemical sensor, which is recorded as MIP / CNQDs@CTP / ITO.

[0021] Preferably, in step (1), the dosage ratio of PFOA, acrylamide (MA), methanol, ethylene glycol dimethacrylate (EGDMA) and azobisisobutyronitrile (AIBN) is 24.9 mg: 2.85 mg: 2 mL: 291 μL: 82.1 mg; and the nitrogen flow time is 10-15 min.

[0022] Preferably, in step (2), the pretreatment operation is: placing ITO in 1M NaOH and boiling it for 20 minutes, then taking out the ITO and ultrasonically cleaning it in ethanol and water in turn, and drying it after cleaning to complete the pretreatment step; wherein the size of the ITO conductive glass is 1cm×2cm; the concentration of the CNQDs@CTP dispersion is 2mg / mL, and the amount of the CNQDs@CTP dispersion added is 20μL.

[0023] Preferably, in step (3), the volume of the molecular imprinting solution added is 6-8 μL, the temperature of thermal polymerization is 60° C., and the time is 5-10 min; the eluent is a mixed solution of methanol and acetic acid in a volume ratio of 9:1, and the elution is accompanied by stirring at 150 rpm for 30-40 min.

[0024] 3. Use of the molecularly imprinted cathode photoelectrochemical sensor based on CNQDs@CTP for detecting perfluorooctanoic acid, the specific steps include:

[0025] S1. First, prepare a PFOA standard solution, then immerse the MIP / CNQDs@CTP / ITO in the PFOA standard solution for incubation. After incubation, take out the MIP / CNQDs@CTP / ITO electrode and dry it naturally to obtain the incubated MIP / CNQDs@CTP / ITO electrode.

[0026] The incubated MIP / CNQDs@CTP / ITO electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode to perform electrochemical testing and detect the PEC signal. A standard curve was constructed based on the linear relationship between the response value (I) of the PEC signal and the logarithmic value (lgC) of the concentration of the PFOA standard solution.

[0027] S2: Follow the same method as S1, except that the test solution is replaced with the PFOA standard solution; finally, the response value of the PEC signal is detected, and the response value of the PEC signal is substituted into the standard curve in S1 to realize the concentration detection of PFOA in the test solution.

[0028] Preferably, in step S1, the concentration of the PFOA standard solution is 5.0×10 -12 ~1.0×10 -5 mol·L -1 ; The incubation time is 20-30min; The electrochemical test is performed using CHI 660E to record and detect PEC signals, wherein the detection of PEC signals is at 0.1mol·L -1 The assay was performed in PBS (pH=7.0).

[0029] The beneficial effects of the present invention are:

[0030] (1) The present invention prepares a CNQDs@CTP nanocomposite material by an in situ synthesis method. The photoelectric properties of the obtained composite material are improved compared with those of CNQDs and CTP, and the cathode photocurrent signal generated has good anti-interference ability.

[0031] (2) The present invention combines molecular imprinting technology with photoelectrochemical analysis methods, which, on the one hand, improves the selectivity of the sensor; on the other hand, the formation of the film protects the electrode interface, making the generated photoelectric signal more stable.

[0032] (3) The present invention adopts a thermal polymerization method to prepare the molecular imprinting film; the sensor is simple to construct and has a fast signal response.

[0033] (4) In the detection process of the present invention, no external bias voltage is applied, and no redox substances are added to the PBS solution, thereby avoiding the interference of multiple factors on the photoelectric signal.

[0034] (5) The photoelectrochemical sensor constructed in the present invention is used for the detection of PFOA, and has high sensitivity, good stability, and a wide linear range of 1×10 -11 -5×10 -6 mol·L -1 , the detection limit is 5.50×10 -12 mol·L -1 .

[0035] (6) The photoelectrochemical sensor constructed by the present invention has good selectivity, ion interference resistance, reproducibility and long-term stability.

[0036] (7) The sensor constructed by the present invention can be used for actual sample detection, and the design concept proposed in the invention can be used to develop sensing methods for detecting other targets, which has a good application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the construction and detection process of the sensor in the present invention, wherein A is the preparation process of CNQDs, B is the preparation process of CNQDs@CTP, and C is the construction process of the sensor;

[0038] Figure 2 This is a mechanism diagram of the present invention for PFOA detection, wherein the left figure is the electron transfer path, and the right figure is a schematic diagram of the photocurrent response;

[0039] Figure 3(a) is a transmission electron microscope image (TEM) of CNQDs; (b) is a scanning electron microscope image (SEM) of CTP; (c) is a scanning electron microscope image (SEM) of CNQDs@CTP; (d) is a high-resolution transmission electron microscope image (HRTEM) of CNQDs; (e) is a transmission electron microscope image (TEM) of CTP; (f) is a transmission electron microscope image (TEM) of CNQDs@CTP;

[0040] Figure 4 is the stability of the working electrode (MIP / CNQDs@CTP / ITO electrode after incubation) under continuous light scanning in the present invention, where the concentration of PFOA is 1 nM;

[0041] Figure 5 (a) shows the PEC response corresponding to different PFOA concentrations; (b) shows the linear relationship between the logarithm of different PFOA concentrations and the change value of its PEC response.

[0042] Figure 6 (a) shows the selectivity of the molecular imprinting photoelectrochemical sensor for target-like substances (octanoic acid (S1), sodium fluoride (S2), sodium trifluoroacetate (S3), pentafluoropropionic acid (S4), perfluoroheptanoic acid (S 5) , perfluorononanoic acid (S6), perfluorooctane sulfonic acid (S7), MIX+perfluorooctanoic acid (S8), perfluorooctanoic acid (S9)); (b) is the ion interference resistance of the molecular imprinting photoelectrochemical sensor; (c) is the reproducibility among the 6 molecular imprinting photoelectrochemical sensors; (d) is the 14-day stability of the molecular imprinting photoelectrochemical sensor. DETAILED DESCRIPTION

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art of the present invention generally understand. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and / or materials related to the documents. In the event of conflict with any incorporated document, the content of this specification shall prevail.

[0045] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0046] like Figure 1 As shown in C, it is a schematic diagram of the construction and detection process of the sensor in the present invention. The specific process is as follows: 20 μL of the uniformly dispersed liquid of CNQDs@CTP is dropped onto the treated ITO glass with an area of ​​0.2826 cm 2 On the circular working electrode interface, the concentration of the dispersion is 2 mg / mL. After the electrode interface is dried, 8 μL of molecular imprinting polymerization solution containing PFOA template molecules, functional monomer acrylamide (MA), crosslinker ethylene glycol dimethacrylate (EGDMA) and initiator azobisisobutyronitrile (AIBN) is further added to the electrode surface, and a molecular imprinting film is obtained after thermal polymerization. The prepared electrode is then eluted in a mixed solution of methanol: acetic acid = 9:1 (V:V) for 30 minutes to remove the template molecules on the molecular imprinting film and obtain a recognition site that can specifically bind to PFOA. At this time, due to the presence of a large number of holes on the film, photogenerated electrons can be transferred to the electrolyte solution, so the photocurrent response is large. After the eluted electrode is dried, it is soaked in a solution containing template molecules for 20 minutes. After rinsing, the photocurrent response at this time is measured and recorded as I. At this time, the target blocks the holes on the molecular imprinting film, resulting in the obstruction of electron transfer, so the photocurrent signal is reduced. The concentration of PFOA in unknown samples can be determined through the relationship between the response value of the photocurrent and the concentration of the target substance.

[0047] Embodiment 1:

[0048] 1. Preparation steps of nanocomposite CNQDs@CTP:

[0049] (a) Preparation of graphite carbon nitride quantum dots (CNQDs):

[0050] Using the hydrothermal synthesis method, 1.63 g of citric acid dihydrate and 2 g of urea were dissolved in 100 mL of water, and then transferred to a 200 mL high-pressure reactor and heated to 180 ° C for 3 h. After cooling to room temperature, the reaction solution was dialyzed with a 1000D dialysis bag and then freeze-dried to obtain a blue solid, which was dissolved in water to obtain a graphite carbon nitride quantum dot solution, recorded as CNQDs solution, with a concentration of 100 mg / mL.

[0051] (b) Preparation of covalent organic framework (CTP):

[0052] 5 mg of TFPP and 5 mg of Pa were dissolved in 10 mL of CH2Cl2 and 10 mL of ACN, respectively, to obtain a Pa solution and a TFPP solution; 16.67 mg of ferric chloride hexahydrate (FeCl3·6H2O) was mixed with 0.2 mL of acetonitrile (ACN) to obtain a FeCl3 solution;

[0053] First, the Pa solution was mixed with the TFPP solution, and FeCl3 solution was added, and then 5 mL CH3COOH and 15 μL CNQDs solution were added. After stirring the reaction at room temperature for 6 hours, the reaction was centrifuged at 10,000 rpm for 5 minutes, and the precipitate obtained by centrifugation was collected and washed with ethanol three times; the washed product was dried at 60 ° C for 8 hours to obtain a black-brown powder solid obtained by grinding the dried product, which was recorded as CNQDs@CTP.

[0054] Figure 3 (a) Transmission electron microscopy image (TEM) of CNQDs, (b) Scanning electron microscopy image (SEM) of CTP, (c) Scanning electron microscopy image (SEM) of CNQDs@CTP, (d) High-resolution transmission electron microscopy image (HRTEM) of CNQDs, (e) Transmission electron microscopy image (TEM) of CTP, (f) Transmission electron microscopy image (TEM) of CNQDs@CTP;

[0055] pass Figure 3 (b) and (c) show that the morphology of CNQDs@CTP changes from a solid sphere to a unique hollow sphere.

[0056] 2. Method for constructing molecularly imprinted photoelectrochemical sensors based on CDs@PCN-224 nanocomposites

[0057] (a) Preparation of molecular imprinting polymer solution:

[0058] Using methanol as an organic solvent, 24.9 mg of the detection target PFOA was dissolved in 2 mL of methanol, and 2.85 mg of the functional monomer acrylamide (MA) was added. The resulting mixed solution was fully oscillated and mixed at a certain temperature, and then nitrogen (N2) was passed through for 10 minutes. 291 μL of the cross-linking agent ethylene glycol dimethacrylate (EGDMA) was added to the mixed solution. After nitrogen was passed through for another 10 minutes, 82.1 mg of the initiator azobisisobutyronitrile (AIBN) was added. After ultrasonic dissolution, a molecular imprinting polymer solution was obtained and stored in a dark place.

[0059] (b) Electrode modification of composite materials:

[0060] The ITO conductive glass was boiled in 1M NaOH for 20 min, then ultrasonically cleaned in ethanol and water, and dried to obtain the pretreated ITO conductive glass, which was used as the working electrode. Then CNQDs@CTP was dissolved in water to obtain a CNQDs@CTP dispersion; 20 μL of the CNQDs@CTP dispersion with a concentration of 2 mg / mL was added dropwise to the pretreated ITO conductive glass, with a specific dropwise area of ​​0.2826 cm 2 The circular working electrode interface is formed; the electrode interface is dried and used for later use. At this time, the working electrode is marked as CNQDs@CTP / ITO.

[0061] (c) Preparation process of thermal polymerized molecular imprinting:

[0062] 8 μL of molecular imprinting polymerization solution was further added to the surface of CNQDs@CTP / ITO, and after thermal polymerization at 60°C, CNQDs@CTP / ITO containing a molecular imprinting film was obtained; the CNQDs@CTP / ITO containing a molecular imprinting film was placed in an eluent for elution for 30 minutes, and after elution, it was dried in the dark at room temperature to obtain a molecular imprinting cathode photoelectrochemical sensor, recorded as MIP / CNQDs@CTP / ITO; the eluent was a mixed solution of methanol: acetic acid = 9:1 (V:V).

[0063] 3. Application of the prepared molecular imprinting photoelectrochemical sensor in the detection of perfluorooctanoic acid:

[0064] Preparation of PFOA solutions of different concentrations: Prepare PFOA standard solutions with concentrations of 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 ;

[0065] The MIP / CNQDs@CTP / ITO was immersed in a PFOA standard solution and incubated for 20 minutes. After incubation, the MIP / CNQDs@CTP / ITO electrode was taken out and dried naturally to obtain the incubated MIP / CNQDs@CTP / ITO electrode.

[0066] The incubated MIP / CNQDs@CTP / ITO electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The PEC signal was recorded and detected by CHI 660E. -1 The test was carried out in PBS (pH=7.0). Figure 4 It can be seen that the photoelectric signal has a stable signal response during the 10 consecutive cycles of on-off light scanning; and there is a linear relationship between the response value (I) of the PEC signal and the logarithmic value (lgC) of the PFOA concentration. A standard curve between the two is drawn as follows: Figure 5 As shown, at 1.0×10 -11 -5.0×10 -6 mol·L -1 The linear relationship was I = 97.94lg C (nM) -844.59 within the concentration range, and the detection limit was as low as 5.50×10 -12 mol·L -1 .

[0067] In detecting actual samples of unknown PFOA concentration, the molecular imprinting photoelectrochemical sensor constructed by this invention can, on the one hand, avoid the interference of complex components in the actual samples and realize the selective detection of PFOA; on the other hand, it can realize sensitive detection of PFOA within the linear range of the sensor.

[0068] Embodiment 2:

[0069] The molecular imprinting photoelectrochemical sensor prepared in Example 1 was used to investigate its selectivity for PFOA. When the solution contained different analogs (octanoic acid (S1), sodium fluoride (S2), sodium trifluoroacetate (S3), pentafluoropropionic acid (S4), perfluoroheptanoic acid (S5), perfluorononanoic acid (S6), perfluorooctane sulfonic acid (S7), MIX+perfluorooctanoic acid (S8), perfluorooctanoic acid (S9)), MIX was a mixed solution containing all the interferents, the concentration of perfluorooctanoic acid was 1 nM, and the concentration of the interferents was set to 10 nM. Figure 6 (a) It can be seen that the sensor will show a large photocurrent response difference (ΔI) when and only when the target perfluorooctanoic acid is present in the solution, proving that the constructed sensor has good selectivity.

[0070] The molecular imprinting photoelectrochemical sensor prepared in Example 1 was used to investigate its ion interference resistance to PFOA. + , K + , Ca 2+ Mg 2+ , Hg + , Pt2+ 、Zn 2+ , Cu 2+ 、SO4 2- 、NO3 - , Cl - , MIX+PFOA), where MIX is a mixed solution containing all interfering ions and PFOA, the concentration of PFOA detected is 1nM, and the concentration of interfering ions is set to 10nM. Figure 6 (b) It can be seen that the sensor will show a large photocurrent response difference (ΔI) when and only when the target PFOA is present in the solution, proving that the constructed sensor has good ion interference resistance.

[0071] The reproducibility of the molecularly imprinted photoelectrochemical sensor was evaluated by measuring PFOA in parallel for 6 times. Figure 6 As shown in (c), the RSD of the measurement result is 2.16%, indicating that the molecular imprinting photoelectrochemical sensor has good reproducibility. Figure 6 As shown in (d), the RSD of the molecular imprinting photoelectrochemical sensor measuring PFOA for 14 days was 4.91%, indicating that it has good long-term stability.

[0072] In summary, the molecular imprinting photoelectrochemical sensor constructed in this embodiment has better detection performance than the prior art and can detect PFOA simply and quickly. In addition, the idea provided by the present invention can be used to develop sensing methods for detecting other targets, which has a good application prospect.

[0073] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a CNQDs@CTP nanocomposite material, characterized in that: Here are the steps: (1) Preparation of CNQDs: First, sodium citrate dihydrate and urea are added to water, mixed and dissolved, and then transferred to a high-pressure reactor for reaction. After the reaction, the reaction solution is cooled to room temperature, and the reaction solution is dialyzed and freeze-dried to obtain a blue graphite carbon nitride quantum dot solid, which is then dissolved in water to obtain a graphite carbon nitride quantum dot solution, which is recorded as a CNQDs solution; (2) Preparation of CNQDs@CTP: Add p-phenylenediamine to acetonitrile to obtain a p-phenylenediamine solution; add tetraaldehyde phenylporphyrin to dichloromethane to obtain a tetraaldehyde phenylporphyrin solution; mix ferric chloride hexahydrate with acetonitrile to obtain a FeCl3 solution; first mix the p-phenylenediamine solution with the tetraaldehyde phenylporphyrin solution, then add the FeCl3 solution, CH3COOH and the CNQDs solution prepared in step (1), after fully mixing by ultrasonication, stir to react at room temperature, centrifuge, wash, dry and grind after the reaction to obtain a black-brown powder solid, recorded as CNQDs@CTP.

2. The method for preparing the CNQDs@CTP nanocomposite material according to claim 1, characterized in that: In step (1), the dosage ratio of sodium citrate dihydrate, urea and water is 1.63g:2g:100mL; the reaction temperature is 180°C, and the reaction time is 3h; the dialysis uses a 1000D dialysis bag, and the dialysis time is 6h; the concentration of the graphite carbon nitride quantum dot solution is 100mg / mL.

3. The method for preparing the CNQDs@CTP nanocomposite material according to claim 1, characterized in that: In step (2), the dosage ratio of p-phenylenediamine, acetonitrile, tetraaldehyde phenylporphyrin, dichloromethane, ferric chloride hexahydrate, acetonitrile to CH3COOH solution and CNQDs solution is 5 mg:10 mL:5 mg:10 mL:16.67 mg:0.2 mL:5 mL:15 μL.

4. The method for preparing the CNQDs@CTP nanocomposite material according to claim 1, characterized in that: In step (2), the stirring reaction speed at room temperature is 350-370 rpm, and the reaction time is 6 hours; the centrifugation condition is set to 10000 rpm, 5 minutes; washing is performed with ethanol three times; the drying temperature is 60°C, and the time is 6-8 hours.

5. A method for constructing a molecularly imprinted cathode photoelectrochemical sensor based on the CNQDs@CTP nanocomposite prepared by the method according to any one of claims 1 to 4, characterized in that: Here are the steps: (1) Preparation of molecular imprinting polymer solution: PFOA and acrylamide were added to methanol, and the obtained mixed solution was oscillated and mixed evenly at a certain temperature. After nitrogen was passed through the mixed solution for a period of time, ethylene glycol dimethacrylate was added to the solution. After nitrogen was passed through the solution for a period of time, an initiator azobisisobutyronitrile was added, and the solution was dissolved by ultrasonication to obtain a molecular imprinting polymer solution, which was stored in a dark place. (2) firstly taking the ITO conductive glass and pre-treating it to obtain the pre-treated ITO conductive glass; Then CNQDs@CTP was added into water and dissolved to obtain CNQDs@CTP dispersion; The CNQDs@CTP dispersion was added dropwise onto the pretreated ITO conductive glass surface and dried at room temperature. The dried product was recorded as CNQDs@CTP / ITO. (3) adding the molecular imprinting polymerization solution prepared in step (1) to the surface of the CNQDs@CTP / ITO obtained in step (2), and forming a molecular imprinting film after thermal polymerization, thereby obtaining CNQDs@CTP / ITO containing a molecular imprinting film; placing the CNQDs@CTP / ITO containing a molecular imprinting film into an elution solution for elution, and drying it in the dark at room temperature after elution, thereby obtaining a molecular imprinting cathode photoelectrochemical sensor, which is recorded as MIP / CNQDs@CTP / ITO.

6. The method according to claim 5, characterized in that In step (1), the usage ratio of PFOA, acrylamide, methanol, ethylene glycol dimethacrylate and azobisisobutyronitrile is 24.9 mg: 2.85 mg: 2 mL: 291 μL: 82.1 mg; and the nitrogen flow time is 10-15 min.

7. The method according to claim 5, characterized in that In step (2), the pretreatment operation is: placing the ITO in 1M NaOH and boiling it for 20 minutes, then taking out the ITO and ultrasonically cleaning it in ethanol and water in turn, and drying it after cleaning, thus completing the pretreatment step; The size of the ITO conductive glass is 1 cm×2 cm; the concentration of the CNQDs@CTP dispersion is 2 mg / mL, and the amount of the CNQDs@CTP dispersion added is 20 μL.

8. The method according to claim 5, characterized in that In step (3), the volume of the molecular imprinting solution added is 6-8 μL, the temperature of thermal polymerization is 60° C., and the time is 5-10 min; the eluent is a mixed solution of methanol and acetic acid in a volume ratio of 9:1, and the elution is accompanied by stirring at 150 rpm for 30-40 min.

9. Use of the molecular imprinted cathode photoelectrochemical sensor prepared by the method according to claim 5 for detecting perfluorooctanoic acid, characterized in that: Here are the steps: S1. First, prepare a PFOA standard solution, then immerse the MIP / CNQDs@CTP / ITO in the PFOA standard solution for incubation, take out the MIP / CNQDs@CTP / ITO electrode after incubation, dry it naturally, and obtain the incubated MIP / CNQDs@CTP / ITO electrode; The incubated MIP / CNQDs@CTP / ITO electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode to perform electrochemical testing and detect the PEC signal. A standard curve was constructed based on the linear relationship between the response value of the PEC signal and the logarithmic value of the concentration of the PFOA standard solution. S2: Follow the same method as S1, except that the test solution is replaced with the PFOA standard solution; finally, the response value of the PEC signal is detected, and the response value of the PEC signal is substituted into the standard curve in S1 to realize the concentration detection of PFOA in the test solution.

10. The use according to claim 9, characterized in that In step S1, the concentration of the PFOA standard solution is 5.0×10 -12 ~1.0×10 -5 mol·L -1 ; The incubation time is 20-30min; The electrochemical test is performed using CHI 660E to record and detect PEC signals, wherein the detection of PEC signals is at 0.1mol·L -1 The assay was performed in PBS with a pH of 7.0.

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