Composite sensing electrode and preparation method and application thereof
By forming a reduced graphene oxide support layer and an Al/Co-MOFs-loaded bifunctional monomer molecularly imprinted polymer film on the electrode surface, the problem of insufficient conductivity and stability of electrode materials in electrochemical molecular imprinting technology is solved, and efficient and low-cost detection of perfluorinated and polyfluoroalkyl substances is achieved.
Patent Information
- Application Number
- CN202411461747.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-18
- Publication Date
- 2026-04-21
AI Technical Summary
Existing electrochemical molecular imprinting technologies suffer from poor electrode material conductivity, unstable structure, and weak specific recognition capabilities, making it difficult to accurately detect perfluorinated and polyfluoroalkyl substances in water, and are also costly.
A composite sensing electrode is adopted, with a reduced graphene oxide support material layer covering the surface of the base electrode, Al/Co-MOFs loaded, and a bifunctional monomer molecularly imprinted polymer film formed through electropolymerization reaction, which improves the number and dispersion of binding sites and enhances conductivity and stability.
It achieves highly sensitive, rapid, and accurate detection of perfluorinated and polyfluoroalkyl substances in water, reduces false positive records, and is suitable for large-scale preparation and industrial applications.
Smart Images
Figure CN121899216A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical sensing and detection, and relates to a composite sensing electrode, its preparation method, and its application. Background Technology
[0002] Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals widely used due to their water and oil resistance, which has led to serious hazards and widespread environmental pollution. Perfluorooctane sulfonate (PFOS), for example, is highly persistent and often referred to as a "perpetual chemical." Once it enters water bodies, it accumulates in organisms through the food chain, posing significant health risks such as cancer, liver damage, thyroid disease, and developmental impacts. Therefore, accurate detection of PFAS in water bodies is essential for effectively eliminating the hazards they pose.
[0003] Electrochemical molecular imprinting (e-MIT) is typically described as a method of creating molecular locks to match molecular bonds. It detects low levels of analytes by monitoring changes in electrochemical signals (current, voltage, or impedance) when the target analyte is trapped at its binding site. In e-MIT, the electrodes used form molecularly imprinted polymers (MIPs) with specific binding sites through electrochemical polymerization. These binding sites match the shape, size, and functional groups of the target molecule, forming cavities with specific recognition sites. Simultaneously, these binding sites are complementary to the template molecule in both physical (size and shape) and chemical (functional and chemical structure) properties, ensuring high selectivity. This gives the electrodes advantages such as rapid analysis, direct signal acquisition, high sensitivity, and low cost, making e-MIT suitable for detecting PFAS in water. However, existing detection methods based on electrochemical molecular imprinting technology use nanomaterials such as gold nanoparticles, diamond electrodes (BDD), and metal oxides as functional support materials. These methods still suffer from problems such as poor conductivity, electrode desensitization, substrate material detachment, and weak imprint polymerization. Furthermore, for target analytes with complex molecular configurations, false positives often occur due to the instability of the MIP polymer configuration and the cavity deterioration caused by microrheological distortion of the functional group spatial positions during the detection process. As a result, the specific recognition ability and detection sensitivity of PFAS in water are still poor, and it is difficult to obtain more accurate detection results. In particular, the MIPs modified in existing electrodes only have single-functional monomers, which still have defects such as poor recognition ability and poor capture ability, making it difficult to achieve accurate detection of trace PFAS in water. This limits the widespread application of electrochemical molecular imprinting technology in the detection of PFAS in water. In addition, the aforementioned electrodes using gold nanoparticles as functional support materials also suffer from high cost, which hinders their widespread use. Therefore, obtaining an electrode material with multiple and uniformly dispersed binding sites, good conductivity, good structural stability, and strong specific recognition ability is of great significance for the rapid and accurate detection of PFAS in water. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a composite sensing electrode with multiple and uniformly dispersed binding sites, good conductivity, good structural stability, and strong specific recognition ability, as well as its preparation method and application.
[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0006] A composite sensing electrode includes a base electrode, the working end surface of which is covered with a support material layer, and a bifunctional monomer molecularly imprinted polymer film for recognizing and capturing target substances is loaded on the support material layer; the support material layer is based on reduced graphene oxide, and Al / Co-MOFs are loaded on the substrate.
[0007] In a further improvement of the aforementioned composite sensing electrode, the supporting material layer has a multi-layer mesh structure covering the working end surface of the base electrode; the bifunctional monomer molecularly imprinted polymer film is loaded onto the supporting material layer in an emulsion form.
[0008] In a further improvement of the aforementioned composite sensing electrode, the base electrode is at least one of a glassy carbon electrode, a screen-printed electrode, and a BDD electrode; and dopamine and o-phenylenediamine are used as bifunctional monomers in the bifunctional monomer molecularly imprinted polymer film.
[0009] As a general technical concept, the present invention also provides a method for preparing the above-mentioned composite sensing electrode, comprising the following steps:
[0010] (1) Preparation of Al / Co-MOFs;
[0011] (2) The Al / Co-MOFs obtained in step (1) are mixed with reduced graphene oxide to form a suspension;
[0012] (3) Drop the suspension obtained in step (2) onto the working end surface of the base electrode and dry it to obtain a base electrode with a support material layer on the surface.
[0013] (4) The base electrode with a support material layer on its surface obtained in step (3) is placed in a solution containing o-phenylenediamine, dopamine and template molecules to carry out an electropolymerization reaction.
[0014] (5) The product obtained after electropolymerization in step (4) is washed, eluted, and template molecules are removed to obtain a composite sensing electrode.
[0015] In a further improvement to the above preparation method, in step (4), the solution containing o-phenylenediamine, dopamine, perfluorinated molecules, and template molecules is prepared by dissolving o-phenylenediamine, dopamine, and template molecules in a phosphate buffer solution.
[0016] In a further improvement to the above preparation method, the molar ratio of o-phenylenediamine to dopamine is 3 to 4:1.
[0017] In a further improvement to the above preparation method, the molar ratio of o-phenylenediamine to the template molecule is 7-9:1.
[0018] In a further improvement to the above preparation method, the ratio of PBS solution to MeOH in the phosphate buffer solution is 2:1.
[0019] In a further improvement to the above preparation method, the template molecule is a perfluorinated or polyfluoroalkyl substance; the perfluorinated or polyfluoroalkyl substance is perfluorooctanoic acid or perfluorooctane sulfonic acid.
[0020] In a further improvement to the above preparation method, the electropolymerization reaction is carried out in a potential cycling range of 0–0.8 V, with 15–20 electrocycles and a scan rate of 50 mV / s. -1 .
[0021] In a further improvement to the above preparation method, in step (2), the suspension is prepared by the following method: Al / Co-MOFs, reduced graphene oxide, and an organic solvent are mixed and ultrasonically dispersed to obtain a suspension; the mass ratio of Al / Co-MOFs to reduced graphene oxide is 1:1; the organic solvent is ethanol; and the concentration of the suspension is 1.0 mg / mL. -1 .
[0022] The above preparation method is further improved in step (3), in which the base electrode is further treated before use: the base electrode is polished and then ultrasonically cleaned in ultrapure water and ethanol in sequence.
[0023] In a further improvement to the above preparation method, in step (5), deionized water is used to rinse the product obtained after electropolymerization in step (4); the eluent used in the elution process is a methanol solution; the methanol solution is obtained by mixing ultrapure water and methanol; the volume ratio of ultrapure water to methanol is 1:1; and the elution time is 20 min.
[0024] The above preparation method is further improved in that, in step (1), the preparation method of Al / Co-MOFs includes the following steps:
[0025] (1.1) Dissolve aluminum salt, cobalt salt, and terephthalic acid in a mixed solution of deionized water and N,N-dimethylformamide, and stir to obtain a precursor solution; the molar ratio of aluminum salt, cobalt salt, and terephthalic acid is 3:1:10; the aluminum salt is AlCl3·6H2O; the cobalt salt is CoCl2·6H2O; the stirring time is 10 min to 40 min;
[0026] (1.2) The precursor solution obtained in step (1.1) is subjected to a hydrothermal reaction and washed to obtain Al / Co-MOFs; the temperature of the hydrothermal reaction is 110℃~140℃; the time of the hydrothermal reaction is 12h.
[0027] As a general technical concept, the present invention also discloses the application of the above-described composite sensing electrode or the composite sensing electrode prepared by the above-described preparation method in the detection of perfluorinated and polyfluoroalkyl substances.
[0028] The above application, further improved by using a composite sensing electrode to detect perfluorinated and polyfluoroalkyl substances in water, includes the following steps:
[0029] S1. Construct an electrochemical sensor using a composite sensing electrode as the working electrode;
[0030] S2. Add the solution to be tested to the electrochemical sensor for scanning and collect the current of the solution to be tested;
[0031] S3. Based on the current of the solution to be tested, and combined with the standard linear regression equation of the concentration of perfluorinated and polyfluoroalkyl substances with the current, the concentration of perfluorinated and polyfluoroalkyl substances in the solution to be tested is calculated.
[0032] In a further improvement to the above application, in step S2, differential pulse voltammetry is used to scan the solution to be tested; the potential during the scanning process is -0.1V to 0.5V.
[0033] In a further improvement to the above application, in step S3, the perfluorinated and polyfluoroalkyl substances are perfluorooctanoic acid or perfluorooctane sulfonic acid;
[0034] In the above application, a further improvement is made when the perfluorinated and polyfluoroalkyl substances are perfluorooctanoic acid, and the standard linear regression equations of the concentration of perfluorooctanoic acid and the current are shown in equations (1) and (2).
[0035] When the concentration of perfluorooctanoic acid is 0.01 nM to 1 nM, the standard linear regression equation between the concentration of perfluorooctanoic acid and the current is as follows:
[0036] y = -18.31 × ln(x) + 60.4 (1);
[0037] When the concentration of perfluorooctanoic acid (PFOA) is between 1 nM and 100 nM, the standard linear regression equation between the PFOA concentration and the current is as follows:
[0038] y = -5.71 ln(x) + 54.9 (2);
[0039] In equations (1) and (2), y is the current value of the solution in μA; x is the concentration of perfluorooctanoic acid in the solution in nM; the detection linear range is 0.01nM to 100nM; and the detection limit is 0.005nM.
[0040] Compared with the prior art, the advantages of the present invention are as follows:
[0041] (1) In view of the shortcomings of existing electrochemical sensors, such as poor conductivity, electrode desensitization, substrate material detachment, and weak imprinted polymerization, and the resulting defects such as poor specific recognition ability, poor detection sensitivity, poor detection accuracy, and short service life, this invention creatively provides a composite sensing electrode, including a base electrode, a support material layer covering the working end surface of the base electrode, and a bifunctional monomer molecularly imprinted polymer film loaded on the support material layer, wherein the support material layer is based on reduced graphene oxide, and Al / Co-MOFs are loaded on the substrate. Compared to conventional functional support materials, Al / Co-MOFs / rGO used in this invention has a higher specific surface area, better conductivity, and better adhesion. Therefore, covering the working end surface of the base electrode with Al / Co-MOFs / rGO not only protects the base electrode but also significantly improves the conductivity of the electrode material and the adhesion to the imprinted polymer. Furthermore, loading a bifunctional monomer molecularly imprinted polymer film onto the support material layer facilitates the formation of a thin, emulsion-like rough molecular recognition layer. This not only increases the number and dispersion of binding sites on the electrode material surface, improving its adsorption and recognition capabilities, but also firmly fixes the imprinted polymer film to the working end surface of the base electrode, thus enhancing the stability of the electrode material. By incorporating Al / Co-MOFs / rGO and a bifunctional monomer-imprinted polymer film onto the surface of the base electrode, the combined effect of these two components enables cross-linking of the polymer imprinted polymer, adsorption of template molecules, and contact with the electrode surface. This improves the electrode's specific recognition capability and stability. More importantly, compared to conventional monomer-imprinted polymer films, the bifunctional monomer-imprinted polymer film used in this invention exhibits higher response performance (e.g., higher sensitivity and accuracy) and sensing stability (e.g., current stability and structural stability of the functional material). Therefore, loading the bifunctional monomer-imprinted polymer film onto the support material layer results in a higher response speed, stronger specific recognition capability, and better stability, which is more conducive to reducing the interference of electrode deactivation on the detection results. The composite sensing electrode of this invention has advantages such as multiple and uniformly dispersed binding sites, good conductivity, good structural stability, and strong specific recognition capability. When used as the working electrode of an electrochemical sensor, it can quickly and accurately detect perfluorinated and polyfluoroalkyl substances in water, while effectively reducing false positive records during the detection process. It has high practical value and promising application prospects.
[0042] (2) This invention also provides a method for preparing a composite sensing electrode. First, Al / Co-MOFs are prepared using a solvothermal method. Then, they are mixed with reduced graphene oxide (rGO) to load the Al / Co-MOFs onto the reduced graphene oxide, resulting in an Al / Co-MOFs / rGO suspension. This suspension is then dropwise added to the surface of a base electrode, forming a mesh-like modified coating on the surface of the base electrode. This mesh-like coating is the supporting material layer (Al / Co-MOFs / rGO) of this invention. Finally, the base electrode is placed in a solution containing o-phenylenediamine, dopamine, and template molecules for electropolymerization. Using dopamine and o-phenylenediamine as bifunctional monomers (DM), and perfluorinated and polyfluoroalkyl substances (such as perfluorooctanoic acid PFOA) as templates, a thin, emulsion-like rough molecular recognition layer is prepared in situ on Al / Co-MOFs / rGO on the working end surface of the basic electrode via electropolymerization. This layer is the bifunctional monomer molecularly imprinted polymer film (DMMIP) of this invention. Finally, washing the template molecules forms cavities inside or on the surface of the DMMIP, exposing binding sites. This process yields a composite sensing electrode with numerous and uniformly dispersed binding sites, good conductivity, good structural stability, and strong specific recognition ability. Furthermore, the preparation method of this invention has the advantages of simple process, convenient operation, and low cost, making it suitable for large-scale preparation and facilitating industrial application.
[0043] (3) This invention also provides an application of a composite sensing electrode in perfluorinated and polyfluoroalkyl substances. Specifically, the composite sensing electrode is used as the working electrode to construct an electrochemical sensor. The electrochemical sensor is used to detect the solution to be tested, collect the current, and combine the standard linear regression equation of the concentration of perfluorinated and polyfluoroalkyl substances with the current to calculate the concentration of perfluorinated and polyfluoroalkyl substances in the solution to be tested. It has the advantages of short detection cycle, high detection sensitivity, and high accuracy. It can realize the rapid and accurate detection of perfluorinated and polyfluoroalkyl substances. It has good application value and market prospects in the fields of environmental monitoring, food safety and water quality diagnosis. Attached Figure Description
[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.
[0045] Figure 1 This is a bar chart showing the current response of composite sensing electrodes prepared under different ratios of functional monomers and template molecules in Example 1 of the present invention.
[0046] Figure 2The images are scanning electron microscope (SEM) images of the Al / Co-MOFs (a), Al / Co-MOFs / rGO / GCE electrode (b), and Al / Co-MOFs / rGO@DMMIP / GCE (c) prepared in Example 1 of this invention.
[0047] Figures 3a-3b The energy dispersive spectroscopy (EDS) spectra of Al / Co-MOFs / rGO@DMMIP / GCE prepared in Example 1 of this invention before and after demolding.
[0048] Figure 4 Electrochemical impedance spectroscopy (EIS) results of the Al / Co-MOFs / rGO / GCE electrode and Al / Co-MOFs / rGO@DMMIP / GCE prepared in Example 1 of this invention before and after demolding.
[0049] Figure 5 This is a cyclic voltammetric scan of the electropolymerization process in Example 1 of the present invention.
[0050] Figure 6 This is a DPV test curve of standard perfluorooctanoic acid (PFOA) solutions of different concentrations in Example 2 of the present invention.
[0051] Figure 7 This is a linear regression curve of the electrochemical sensor detecting perfluorooctanoic acid in Example 2 of the present invention. Detailed Implementation
[0052] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.
[0053] Example 1
[0054] A composite sensing electrode includes a base electrode, a support material layer covering the working end surface of the base electrode, and a bifunctional monomer molecularly imprinted polymer film for recognizing and capturing target substances loaded on the support material layer, wherein the support material layer is based on reduced graphene oxide, and Al / Co-MOFs are loaded on the substrate.
[0055] In this embodiment, the supporting material layer forms a multi-layered mesh structure covering the working end surface of the base electrode.
[0056] In this embodiment, a bifunctional monomer molecularly imprinted polymer film is loaded onto a support material layer in an emulsion form, using dopamine and o-phenylenediamine as bifunctional monomers to recognize and capture perfluorooctanoic acid (PFOA).
[0057] In this embodiment, the base electrode is a glassy carbon electrode.
[0058] A method for preparing the composite sensing electrode described in this embodiment includes the following steps:
[0059] (1) Preparation of Al / Co-MOFs, specifically:
[0060] (1.1) Dissolve 3 mmol aluminum chloride (AlCl3·6H2O), 1 mmol cobalt chloride (CoCl2·6H2O) and 10 mmol terephthalic acid (H2BDC) in a mixed solution of deionized water and N,N-dimethylformamide (DMF) (the mixed solution was obtained by mixing 22.5 mL of deionized water and 67.5 mL of DMF), and stir at room temperature for 0.5 h to obtain the precursor solution.
[0061] (1.2) The precursor solution obtained in step (1.1) was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene, sealed, and subjected to hydrothermal reaction at a temperature of 140 °C for 12 h. Solid-liquid separation was performed, and the precipitate obtained by solid-liquid separation was washed with methanol and ultrapure water and dried to obtain Al / Co-MOFs.
[0062] (2) The Al / Co-MOFs obtained in step (1) are mixed with reduced graphene oxide to prepare a suspension, specifically:
[0063] Al / Co-MOFs, reduced graphene oxide (rGO), and ethanol were mixed and ultrasonically dispersed to obtain a concentration of 1.0 mg / mL. -1 The suspension is an Al / Co-MOFs / rGO suspension, in which the mass ratio of Al / Co-MOFs to reduced graphene oxide is 1:1.
[0064] (3) Drop the suspension obtained in step (2) onto the working end surface of the base electrode and dry it to obtain a base electrode with a support material layer on its surface, specifically:
[0065] The glassy carbon electrode (GCE) was polished sequentially with alumina powders of 0.30 mm and 0.05 mm, and then ultrasonically cleaned sequentially with ultrapure water and ethanol. 5 μL of Al / Co-MOFs / rGO suspension was then dropped onto the working end surface of the ultrasonically cleaned glassy carbon electrode (GCE) and dried at room temperature, so that Al / Co-MOFs / rGO covered the working end surface of the glassy carbon electrode (GCE) and formed a layered mesh modification coating on the electrode surface, resulting in a base electrode with a support material layer on the surface, which is the Al / Co-MOFs / rGO / GCE electrode.
[0066] (4) The base electrode (Al / Co-MOFs / rGO / GCE electrode) with a support material layer on its surface obtained in step (3) is placed in a solution containing o-phenylenediamine, dopamine and template molecules for electropolymerization reaction, specifically:
[0067] The Al / Co-MOFs / rGO / GCE electrode was placed in a phosphate buffer solution (PBS:MeOH = 2:1) containing o-phenylenediamine (o-PD), dopamine hydrochloride (DA), and perfluorooctanoic acid (PFOA) and scanned several times using cyclic voltammetry. The potential cycling range for the electropolymerization reaction was 0–0.8 V vs (Ag / AgCl), with 15–20 cycles and a scan rate of 50 mV / s. -1 MIP electropolymerization was performed to deposit a bifunctional monomer molecularly imprinted polymer film on Al / Co-MOFs / rGO, forming a thin, emulsion-like rough molecular recognition layer on the electrode surface. In this step, the solution containing o-phenylenediamine, dopamine, perfluorinated molecules, and template molecules was prepared by dissolving o-phenylenediamine, dopamine, and template molecules in a phosphate buffer solution. The molar ratio of o-phenylenediamine to dopamine hydrochloride was 3.5:1, the molar ratio of o-phenylenediamine to perfluorooctanoic acid (PFOA) was 8:1, and the volume ratio of PBS solution to MeOH in the phosphate buffer solution was 2:1. The perfluorinated and polyfluoroalkyl substances used were perfluorooctanoic acid (PFOA), i.e., in this embodiment, PFOA was used as the template molecule.
[0068] (5) After electropolymerization is completed, the product obtained after electropolymerization in step (4) is rinsed with deionized water (DI), and then eluted with methanol solution (the methanol solution is obtained by mixing ultrapure water and methanol, with the volume ratio of ultrapure water and methanol being 1:1) for 20 min to remove template molecules and obtain composite sensing electrode, namely Al / Co-MOFs / rGO@DMMIP / GCE.
[0069] In this embodiment, the effects of different functional monomers and template molecules on the current response were also investigated, and the results are as follows: Figure 1 As shown.
[0070] Figure 1 This is a bar chart showing the current response of composite sensing electrodes prepared under different ratios of functional monomers and template molecules in Example 1 of this invention. Figure 1 It is known that both o-PD and DA significantly affect the current response of the sensor. In particular, by optimizing the ratio of o-phenylenediamine to dopamine hydrochloride and o-phenylenediamine to template molecules, the electrode exhibits excellent sensing sensitivity.
[0071] Figure 2 These are scanning electron microscope (SEM) images of the Al / Co-MOFs (a), Al / Co-MOFs / rGO / GCE electrode (b), and Al / Co-MOFs / rGO@DMMIP / GCE (c) electrodes prepared in Example 1 of this invention. Figure 2It is known that the Al / Co-MOFs / rGO prepared in this invention exhibits a highly polymerized block structure. After incorporating reduced graphene oxide (rGO), the whole exhibits a multi-layer network structure. Subsequently, it is electrochemically polymerized by DMMIP onto the composite electrode, and the surface becomes rough and exhibits an emulsion morphology. After cleaning, molecular channels are formed.
[0072] Figures 3a-3b The energy dispersive spectroscopy (EDS) spectra of Al / Co-MOFs / rGO@DMMIP / GCE prepared in Example 1 of this invention before and after demolding. Figure 3a Before demolding, Figure 3b This is after demolding. As shown in Figure 3, after washing with the eluent, the content of F in the polymer decreased significantly due to the removal of template molecules (PFOA) and the formation of cavities. This indicates that Al / Co-MOFs / rGO and DMMIP were successfully loaded and deposited on the glassy carbon electrode surface.
[0073] Figure 4 Electrochemical impedance spectroscopy (EIS) graphs of the Al / Co-MOFs / rGO / GCE electrode and the Al / Co-MOFs / rGO@DMMIP / GCE electrode prepared in Example 1 of this invention before and after demolding. Figure 4 It can be seen that, compared with bare GCE, the introduction of Al / Co-MOFs / rGO increases the specific surface area of the electrode, improves the conductivity, and leads to an increase in the redox peak current. After electropolymerization of NIP, the electrode surface is covered by polymer, and the Fe in the electrolyte... 2+ / 3+ The inability to reach the electrode surface leads to increased impedance and the disappearance of the peak current. The template molecule (PFOA) is eluted from the MIP using an eluent, forming an ion channel and causing a decrease in resistance, thus regenerating the redox current. Electrochemical impedance spectroscopy (EIS) is a very effective method for studying electron transfer resistance (Rct), where Rct is equal to the diameter of the semicircle in the diagram.
[0074] Figure 5 This is a cyclic voltammetric scan of the electropolymerization reaction process in Example 1 of the present invention. Figure 5 It can be seen that the NIP and MIP layers on the electrode surface undergo electropolymerization in the electrodeposition solution. During the NIP polymerization process, a prominent peak can be observed at 0.41V for the oxidative polymerization of DA and o-PD, followed by another smaller peak at about 0.68V. After the incorporation of PFOA, the complete disappearance of the second oxidation peak can be observed, which is direct evidence that PFOA is incorporated into the polymer layer as a template molecule.
[0075] Example 2
[0076] The application of a composite sensing electrode in the detection of perfluorinated and polyfluoroalkyl substances, specifically the detection of perfluorooctanoic acid (PFOA) in water using the composite sensing electrode prepared in Example 1, includes the following steps:
[0077] S1. An electrochemical sensor was constructed using a composite sensing electrode as the working electrode. All electrochemical studies were conducted in a three-electrode battery configuration. The glassy carbon electrode was used as the working electrode with a diameter of 3 mm, the counter electrode was a graphite electrode, and the reference electrode was Ag / AgCl / (3m KCl). In the analysis of ultrapure water samples and water samples from the Xiangjiang River basin, the MIP electrode was cultured in perfluorooctanoic acid solution, and DPV tests were performed after immersion in the solution for 15 minutes. Each DPV test was performed at least three times.
[0078] S2. The test solution is added to the electrochemical sensor for scanning. Specifically, differential pulse voltammetry (DPV) is used to scan the test solution and collect the current of the test solution. The DPV parameters are -0.1 to 0.5 V vs Ag / AgCl, potential amplitude 50 mV, potential increment 10 mV, sampling width 10 ms, and pulse period 100 ms.
[0079] S3. Based on the current of the test solution and the standard linear regression equation of the concentration of perfluorooctanoic acid (PFOA) and the current, the concentration of PFOA in the test solution was calculated, and the results are shown in Table 1.
[0080] In this embodiment, the method for constructing the standard linear regression equation between the concentration of perfluorooctanoic acid and the current includes the following steps:
[0081] Standard perfluorooctanoic acid (PFOA) solutions of different concentrations were prepared, namely 0 nM, 0.02 nM, 0.05 nM, 0.3 nM, 0.5 nM, 2 nM, 10 nM, and 100 nM. The current of the standard PFOA solutions of different concentrations was obtained using the electrochemical sensor constructed in Example 2. A linear relationship between concentration and current was established, and a standard linear regression equation for the concentration of PFOA and current was obtained.
[0082] Figure 6 This is a DPV test curve of standard perfluorooctanoic acid (PFOA) solutions of different concentrations in Example 2 of the present invention. Figure 6 It is evident that the electrochemical sensor constructed based on the composite sensing electrode (Al / Co-MOFs / rGO@DMMIP / GCE) of this invention exhibits excellent current sensitivity and response capability, demonstrating superior linear detection range and detection limit.
[0083] Figure 7 This is a linear regression curve of the electrochemical sensor used in Example 2 of the present invention for detecting perfluorooctanoic acid. Figure 7It can be seen that, under low concentration conditions (0.01 nM to 1 nM), the standard linear regression equation between the concentration of perfluorooctanoic acid and the current is:
[0084] y = -18.31 × ln(x) + 60.4 (1);
[0085] Meanwhile, under high concentration (1 nM to 100 nM) conditions, the standard linear regression equation between the concentration of perfluorooctanoic acid and the current is:
[0086] y = -5.71 ln(x) + 54.9 (2);
[0087] In equations (1) and (2), y is the current value of the solution in μA; x is the concentration of perfluorooctanoic acid in the solution in nM; the detection linear range of the sensor is 0.01nM to 100nM, and the detection limit is 0.005nM.
[0088] Depend on Figure 6 and Figure 7 The results show that the electrochemical sensor constructed based on the composite sensing electrode (Al / Co-MOFs / rGO@DMMIP / GCE) in this invention has good sensing response performance, high sensitivity and response capability. When used to detect PFOA in water, the linear detection range is 10pM-100nM and the LOD is 5.0pM.
[0089] In this embodiment, to evaluate the detection capability of the electrochemical sensor based on the composite sensing electrode (Al / Co-MOFs / rGO@DMMIP / GCE) in actual water bodies, three parallel analyses were performed on three samples from tributaries of the Yangtze River spiked with 10 pM, 50 pM, and 500 pM, respectively, as detailed in Table 1. The results show that the recovery rate of the electrochemical sensor based on the composite sensing electrode (Al / Co-MOFs / rGO@DMMIP / GCE) ranged from 97.0% to 103.4%, with a small difference, indicating that the electrochemical sensor based on the composite sensing electrode (Al / Co-MOFs / rGO@DMMIP / GCE) in this invention has good potential for practical application.
[0090] Table 1. Application of Al / Co-MOFs / rGO / DMMIP / GCE in PFOA detection of actual samples.
[0091] Spiked concentration (pM) Measurement mean ± standard deviation (pM) Recovery rate ± relative standard deviation (%) 10 9.7±0.3 97.0±3.1 50 51.7±2.1 103.4±4.1 500 491.5±11.4 98.3±2.3
[0092] As can be seen from the above results, the composite sensing electrode of the present invention has the advantages of multiple and uniformly dispersed binding sites, good conductivity, good structural stability, and strong specific recognition ability. When used as the working electrode of an electrochemical sensor, it can quickly and accurately detect perfluorinated and polyfluoroalkyl substances in water, while effectively reducing false positive records during the detection process. It has the advantages of short detection cycle, high detection sensitivity, and high accuracy. It has high application value and good application prospects in the fields of environmental monitoring, food safety, and water quality diagnosis.
[0093] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.
Claims
1. A composite sensing electrode, characterized in that, The composite sensing electrode includes a base electrode, the working end surface of which is covered with a support material layer, and a bifunctional monomer molecularly imprinted polymer film for recognizing and capturing target substances is loaded on the support material layer; the support material layer is based on reduced graphene oxide, and Al / Co-MOFs are loaded on the substrate.
2. The composite sensing electrode according to claim 1, characterized in that, The support material layer has a multi-layered mesh structure covering the working end surface of the base electrode; the bifunctional monomer molecularly imprinted polymer film is loaded onto the support material layer in an emulsion form.
3. The composite sensing electrode according to claim 1 or 2, characterized in that, The base electrode is at least one of glassy carbon electrode, screen-printed electrode, and BDD electrode; the bifunctional monomer molecularly imprinted polymer film uses dopamine and o-phenylenediamine as bifunctional monomers.
4. A method for preparing a composite sensing electrode as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Preparation of Al / Co-MOFs; (2) The Al / Co-MOFs obtained in step (1) are mixed with reduced graphene oxide to form a suspension; (3) Drop the suspension obtained in step (2) onto the working end surface of the base electrode and dry it to obtain a base electrode with a support material layer on the surface. (4) The base electrode with a support material layer on its surface obtained in step (3) is placed in a solution containing o-phenylenediamine, dopamine and template molecules to carry out an electropolymerization reaction. (5) The product obtained after electropolymerization in step (4) is washed, eluted, and template molecules are removed to obtain a composite sensing electrode.
5. The preparation method according to claim 4, characterized in that, In step (4), the solution containing o-phenylenediamine, dopamine, perfluorinated molecules, and template molecules is prepared by dissolving o-phenylenediamine, dopamine, and template molecules in a phosphate buffer solution; the molar ratio of o-phenylenediamine to dopamine is 3-4:1; the molar ratio of o-phenylenediamine to template molecules is 7-9:1; the ratio of PBS solution to MeOH in the phosphate buffer solution is 2:1; the template molecules are perfluorinated and polyfluoroalkyl substances; the perfluorinated and polyfluoroalkyl substances are perfluorooctanoic acid or perfluorooctane sulfonic acid; the potential cycling range in the electropolymerization reaction is 0-0.8V, the number of electrocycles is 15-20 times, and the scan rate is 50mV s. -1 .
6. The preparation method according to claim 5, characterized in that, In step (2), the suspension is prepared by the following method: Al / Co-MOFs, reduced graphene oxide, and an organic solvent are mixed and ultrasonically dispersed to obtain a suspension; the mass ratio of Al / Co-MOFs to reduced graphene oxide is 1:1; the organic solvent is ethanol; and the concentration of the suspension is 1.0 mg / mL. -1 ; In step (3), the base electrode is further treated as follows before use: the base electrode is polished and then ultrasonically cleaned in ultrapure water and ethanol in sequence. In step (5), the product obtained after electropolymerization in step (4) is rinsed with deionized water; the eluent used in the elution process is a methanol solution; the methanol solution is obtained by mixing ultrapure water and methanol; the volume ratio of ultrapure water to methanol is 1:1; the elution time is 20 min.
7. The preparation method according to any one of claims 4 to 6, characterized in that, In step (1), the preparation method of the Al / Co-MOFs includes the following steps: (1.1) Dissolve aluminum salt, cobalt salt, and terephthalic acid in a mixed solution of deionized water and N,N-dimethylformamide, and stir to obtain a precursor solution; the molar ratio of aluminum salt, cobalt salt, and terephthalic acid is 3:1:10; the aluminum salt is AlCl3·6H2O; the cobalt salt is CoCl2·6H2O; the stirring time is 10 min to 40 min; (1.2) The precursor solution obtained in step (1.1) is subjected to a hydrothermal reaction and washed to obtain Al / Co-MOFs; the temperature of the hydrothermal reaction is 110℃~140℃; the time of the hydrothermal reaction is 12h.
8. The application of a composite sensing electrode as described in any one of claims 1 to 3 or a composite sensing electrode prepared by the preparation method described in any one of claims 4 to 7 in the detection of perfluorinated and polyfluoroalkyl substances.
9. The application according to claim 8, characterized in that, The detection of perfluorinated and polyfluoroalkyl substances in water using a composite sensing electrode includes the following steps: S1. Construct an electrochemical sensor using a composite sensing electrode as the working electrode; S2. Add the solution to be tested to the electrochemical sensor for scanning and collect the current of the solution to be tested; S3. Based on the current of the solution to be tested, and combined with the standard linear regression equation of the concentration of perfluorinated and polyfluoroalkyl substances with the current, the concentration of perfluorinated and polyfluoroalkyl substances in the solution to be tested is calculated.
10. The application according to claim 9, characterized in that, In step S2, the solution to be tested is scanned using differential pulse voltammetry; the potential during the scan is -0.1V to 0.5V. In step S3, the perfluorinated and polyfluoroalkyl substances are perfluorooctanoic acid or perfluorooctane sulfonic acid; When the perfluorinated and polyfluoroalkyl substances are perfluorooctanoic acid, the standard linear regression equations of the concentration of perfluorooctanoic acid and the current are shown in equations (1) and (2). When the concentration of perfluorooctanoic acid is 0.01 nM to 1 nM, the standard linear regression equation between the concentration of perfluorooctanoic acid and the current is as follows: y = -18.31 × ln(x) + 60.4 (1); When the concentration of perfluorooctanoic acid (PFOA) is between 1 nM and 100 nM, the standard linear regression equation between the PFOA concentration and the current is as follows: y = -5.71 ln(x) + 54.9 (2); In equations (1) and (2), y is the current value of the solution in μA; x is the concentration of perfluorooctanoic acid in the solution in nM; the detection linear range is 0.01nM to 100nM; and the detection limit is 0.005nM.