Electrochemical working electrode and preparation method and application thereof

Abstract

This invention discloses an electrochemical working electrode, its preparation method, and its application. The electrode comprises a conductive substrate, a composite layer, and a Nafion-stabilized modification layer covering the composite layer. The composite layer includes an ordered porous anodic alumina functional layer loaded on the surface of the conductive substrate and a molecularly imprinted polymer sensitive membrane in situ grown within the nanopores of the ordered porous anodic alumina functional layer. The molecularly imprinted polymer sensitive membrane uses 1,3,6,8-tetra(3-carboxyphenyl)pyrene as the functional monomer and Fe... 3+ The template molecule is synthesized in situ by constant current electrodeposition. This invention utilizes the AAO nanoconfining effect and size matching recognition, combined with specific coordination, to achieve highly selective and sensitive detection. The detection linear range is 0.01~50 mg / L, the detection limit is ≤0.004 mg / L, and the relative error is ≤5% under 100 times excess divalent iron. No sample pretreatment is required, and the operation is simple and stable.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensing and analysis technology, and in particular to an electrochemical working electrode, its preparation method, and its application. Background Technology

[0002] In laboratory analysis and testing, material preparation, electrolyte formulation, and other scenarios, divalent iron (Fe2+) is used... 2+ The purity of the solution directly determines the reliability of the experimental results, among which trivalent iron (Fe3+) is crucial. 3+ ) is the most important oxidizing impurity, trace amounts of Fe 3+ This can lead to problems such as redox reaction imbalance, distorted experimental data, and material structural defects. Therefore, for Fe... 2+ Fe in solution 3+ Its accurate detection has significant value for laboratory applications.

[0003] Fe is commonly used in laboratories at present. 3+ The detection method has obvious drawbacks: the o-phenanthroline spectrophotometric method requires multiple pretreatment steps such as hydroxylamine hydrochloride reduction and colorimetric reagent complexation, which is cumbersome and requires high concentrations of Fe. 2+ The matrix exhibits severe spectral interference, resulting in a relative detection error of 5% to 20%. While atomic absorption spectrometry and ICP-MS offer high detection accuracy, their high instrument costs, complex sample pretreatment, and long detection cycles make them unsuitable for rapid batch testing in laboratories.

[0004] Electrochemical detection methods offer advantages such as simple equipment, rapid response, and low cost, but related technologies have several shortcomings: traditional glassy carbon and ITO planar electrodes have small specific surface areas, low loading of sensitive sites, and insufficient detection sensitivity; ordinary modified electrodes have weak adhesion between the sensitive film and the substrate, are prone to detachment, and have poor stability in continuous detection; although molecular imprinting technology can achieve specific recognition, the planar substrate imprint has low hole regularity and weak size matching effect, especially at high Fe concentrations. 2+ Selectivity decreases significantly in coexisting systems.

[0005] Therefore, it is necessary to develop a method to enhance Fe 2+ Fe in solution 3+ The technical solution for electrochemical detection is very important. Summary of the Invention

[0006] In view of this, this application provides an electrochemical working electrode, its preparation method, and its application, to address how to improve the electrochemical detection of Fe. 2+ Fe in solution 3+ Issues related to sensitivity, selectivity, and stability.

[0007] To achieve the above technical objectives, this application adopts the following technical solution: In a first aspect, this application provides an electrochemical working electrode, comprising a conductive substrate, a composite layer, and a Nafion-stabilized modification layer covering the composite layer; the composite layer comprises an ordered porous anodic alumina functional layer loaded on the surface of the conductive substrate and a molecularly imprinted polymer sensitive membrane in situ grown within the nanopores of the ordered porous anodic alumina functional layer; the molecularly imprinted polymer sensitive membrane uses 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene as the functional monomer and Fe... 3+ It was synthesized in situ using a template molecule via constant current electrodeposition.

[0008] Secondly, this application provides a method for preparing an electrochemical working electrode, comprising the following steps: After hydrophilization treatment, the double-channel AAO film is transferred to the surface of a cleaned conductive substrate and then hot-pressed to obtain a conductive substrate / ordered anodic aluminum oxide porous functional layer. 1,3,6,8-tetra(3-carboxyphenyl)pyrene, ferric salt, and supporting electrolyte were dispersed in a solvent to obtain a prepolymerized electrolyte. A conductive substrate / ordered anodic alumina porous functional layer was used as the working electrode, and constant current electrodeposition was performed in the prepolymerized electrolyte to obtain a conductive substrate / AAO / molecularly imprinted polymer sensitive membrane composite electrode. After acid washing, the conductive substrate / AAO / molecularly imprinted polymer sensitive film composite electrode is drop-coated with Nafion ethanol solution and then vacuum dried to obtain the electrochemical working electrode.

[0009] Preferably, the conductive substrate includes one or more of ITO conductive glass, FTO conductive glass, or conductive carbon paper; the surface resistivity of the conductive substrate is ≤20 Ω / sq.

[0010] Preferably, the pore size of the dual-channel AAO thin film is 30~80 nm, and the pore density is 10. 9 ~10 11 Hole / cm 2 The thickness is 50~200μm, the porosity is 10~20%, and the pores have a hexagonal close-packed ordered structure.

[0011] Preferably, the steps for hydrophilicating the double-channel AAO membrane are as follows: after cleaning the double-channel AAO membrane, it is dried with nitrogen gas and then subjected to oxygen plasma treatment.

[0012] Preferably, the prepolymerized electrolyte comprises 0.01~0.02 mol / L 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene and 0.005~0.01 mol / L FeCl3. The supporting electrolyte is 6H₂O and 0.1 mol / L; the solvent is an aqueous solution of acetonitrile.

[0013] Preferably, the parameters for galvanic electrodeposition are a current density of 0.8~1.5 mA / cm². 2 The deposition time is 12-20 minutes and the deposition temperature is 20-30℃.

[0014] Thirdly, this application provides an application of an electrochemical working electrode for the quantitative detection of ferric ions in a ferrous matrix.

[0015] Preferably, it includes the following steps: A three-electrode system consisting of an electrochemical working electrode, a counter electrode, and a reference electrode was constructed. The test solution was adjusted to acidity and a supporting electrolyte was added to obtain the test treatment solution; The three-electrode system was placed in the test solution, a reduction constant potential was applied, and the steady-state reduction current was collected under stirring. The concentration of ferric ions in the test solution was calculated using the standard curve method.

[0016] Preferably, the pH of the test solution is adjusted to 1.0~1.5; the voltage of the reduction constant potential is -0.15 ~ +0.1 V.

[0017] The beneficial effects of this application are as follows: The electrochemical working electrode constructed based on AAO ordered nanopores significantly increases the specific surface area, effectively improving the imprinted hole density and electron transport rate, thereby significantly enhancing the method sensitivity. Simultaneously, this application utilizes a synergistic dual recognition mechanism of AAO confinement size effect and TCPPy carboxyl-specific coordination to effectively eliminate interference from coexisting high-valence metal ions and excess matrix components, giving the method excellent selectivity. Furthermore, the molecular imprint membrane is anchored and immobilized using a Nafion film, effectively suppressing the shedding and contamination of the sensitive layer during use and storage, ensuring the response stability of the method under continuous testing and long-term storage conditions. Therefore, the overall improvement in the electrochemical detection of Fe is enhanced. 2+ Fe in solution 3+ Sensitivity, selectivity and stability.

[0018] This application requires no pretreatment steps such as reduction and color development, has a simple operation process, and a short single detection time, making it easy to achieve rapid analysis of batch samples. Detailed Implementation

[0019] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0020] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0023] Unless otherwise explicitly defined and specified herein, all technical and scientific terms used in this application shall have the generally accepted meanings understood by one of ordinary skill in the field of chemical and chemical materials technology (including but not limited to polymer chemistry, inorganic chemistry, organic synthesis, catalysis chemistry, materials processing, and chemical unit operations) based on their professional knowledge and conventional practice. The use of any terminology herein is intended to describe the specific embodiments of this application in the clearest and most accurate manner, so as to fully disclose the technical solution. Such use shall not in any way be construed as a limitation on the scope of the claims, nor does it imply the exclusion of equivalent technical solutions that could be reasonably known by one of skill in the art based on the concept of this application.

[0024] The terms "comprising," "including," "having," "containing," and any grammatical variations or similar expressions used in the specification and claims of this application are all open-ended and non-exhaustive descriptive terms. Their purpose is to explicitly describe the existence of technical features, components, steps, or parts, while explicitly allowing and covering the possibility that other features, components, steps, parts, or any combinations thereof not explicitly listed may exist or be added to the technical solution, as long as such additions do not destroy the integrity and inventiveness of the original technical solution.

[0025] When the terms "embodiments," "some embodiments," or "specific embodiments" are mentioned in the specification, they refer to examples that, in conjunction with the specific parameters, materials, steps, and results described in that section, constitute one or a group of examples for implementing the technical solutions of this application. These embodiments are used for full disclosure and illustrative purposes, not for exhaustive enumeration. Those skilled in the art should understand that, without departing from the overall inventive concept of this application, the various technical features disclosed in different embodiments can be combined, substituted, modified, or deleted to form other implementation methods that are not listed one by one in the specification but also fall within the protection scope of this application.

[0026] Unless otherwise expressly specified and limited, all terms related to chemical process operations, material preparation, processing and analytical testing involved in this application shall be interpreted in the broadest sense based on the conventional understanding of those skilled in the art.

[0027] Regarding performance testing and structural characterization, all testing and characterization methods involved in this application, unless otherwise specified, refer to conventional methods known in the art. Specific testing conditions may be selected and adjusted according to the sample properties and relevant national standards, international standards, or industry-standard methods. Test items may include mechanical properties (such as tensile, bending, and impact strength), thermal properties (such as DSC and TGA analysis), and chemical stability (such as solvent resistance and acid / alkali corrosion resistance). Structural characterization methods may include FT-IR, NMR, XRD, SEM, TEM, and BET. All test results should be understood to be within the allowable range of conventional experimental errors.

[0028] Regarding numerical values ​​and ranges, all parameter ranges expressed in this application in the form of "from a certain value to a certain value" should be understood as explicitly disclosing the endpoints of the range, each specific numerical point between the endpoints, and all sub-ranges formed by any two numerical points within the range. For example, "30℃ to 80℃" discloses 30, 31, ..., 80℃, as well as sub-ranges such as 30-50℃, 45-70℃, etc. When a numerical value is preceded by "about," "approximately," or similar words, it indicates that the numerical value is allowed to have reasonable errors recognized in the art under the measurement or control conditions, which can generally be understood as the deviation allowed by relevant standards or a normal fluctuation range of ±5% or ±10%.

[0029] Anodized aluminum oxide (AAO) possesses a highly ordered nanoporous structure with a large specific surface area and uniform pore size, making it suitable as a confined growth carrier for molecularly imprinted polymers, significantly improving the density and regularity of imprinted holes. 1,3,6,8-Tetra(3-carboxyphenyl)pyrene (TCPPy) contains multiple carboxyl active sites, which can interact with Fe³⁺. + It forms stable coordination bonds, adapting to the molecular imprint size matching recognition mechanism; Nafion perfluorosulfonic acid membrane can effectively anchor the sensitive layer, inhibit non-specific adsorption and membrane detachment, and improve detection stability.

[0030] Based on this, this application was created.

[0031] For existing Fe 3+ The current detection methods suffer from drawbacks such as cumbersome operation, poor selectivity, insufficient stability, low specific surface area of ​​planar electrodes, and poor imprint recognition efficiency. This application provides an electrochemical working electrode comprising a conductive substrate, a composite layer, and a Nafion-stabilized modification layer covering the composite layer. The composite layer includes an ordered porous anodic alumina functional layer loaded on the surface of the conductive substrate and a molecularly imprinted polymer sensitive membrane in situ grown within the nanopores of the ordered porous anodic alumina functional layer. The molecularly imprinted polymer sensitive membrane uses 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene as the functional monomer and Fe... 3+ It was synthesized in situ using a template molecule via constant current electrodeposition.

[0032] The electrode in this application is generated by the interaction of TCPPy carboxyl groups with Fe. 3+ The specific coordination effect of Fe, combined with the size matching and confinement effect of AAO nanopores, enables the control of Fe 3+ The dual-specific recognition capability of the Nafion layer enhances the adhesion, anti-fouling ability, and long-term stability of the sensitive membrane, thereby enabling the chemical working electrode to detect Fe. 2+ Fe in solution 3+ The sensitivity, selectivity and stability are improved.

[0033] This application provides a method for preparing an electrochemical working electrode, comprising the following steps: After hydrophilization treatment, the double-channel AAO film is transferred to the surface of a cleaned conductive substrate and then hot-pressed to obtain a conductive substrate / ordered anodic aluminum oxide porous functional layer. 1,3,6,8-tetra(3-carboxyphenyl)pyrene, ferric salt, and supporting electrolyte were dispersed in a solvent to obtain a prepolymerized electrolyte. A conductive substrate / ordered anodic alumina porous functional layer was used as the working electrode, and constant current electrodeposition was performed in the prepolymerized electrolyte to obtain a conductive substrate / AAO / molecularly imprinted polymer sensitive membrane composite electrode. After acid washing, the conductive substrate / AAO / molecularly imprinted polymer sensitive film composite electrode is drop-coated with Nafion ethanol solution and then vacuum dried to obtain the electrochemical working electrode.

[0034] In some embodiments, the conductive substrate includes one or more of ITO conductive glass, FTO conductive glass, or conductive carbon paper; the surface resistivity of the conductive substrate is ≤20 Ω / sq.

[0035] In some embodiments, the pore size of the double-pass AAO film used is 30~80 nm, and the pore density is 10. 9The film has a porosity of ~10¹¹ pores / cm², a thickness of 50~200 μm, and a porosity of 10~20%, with hexagonal close-packed ordered pores. After hydrophilization treatment and hot-pressing onto the surface of a conductive substrate, this dual-channel AAO film constitutes the ordered anodic aluminum oxide porous functional layer.

[0036] In this embodiment, the dual-channel AAO film is a commercially available product, commercially available from Huayuan (China) or similar suppliers; preferably, it has a pore size of 50 nm, a thickness of 50~100 μm, and a pore density of approximately 10¹. 0 The isotropic double-channel AAO membrane has a porosity of approximately 15-20% and its channels are arranged in a hexagonal close-packed ordered structure. The ordered anodic aluminum oxide porous functional layer is tightly bonded to the conductive substrate without bubbles or delamination.

[0037] In some embodiments, the hydrophilization treatment of the double-channel AAO film is performed by cleaning the double-channel AAO film, drying it with nitrogen gas, and then treating it with oxygen plasma.

[0038] In this embodiment, the specific steps for hydrophilicating the dual-channel AAO film are as follows: the dual-channel AAO film is ultrasonically cleaned in acetone, anhydrous ethanol, and ultrapure water for 10-15 minutes respectively, dried with high-purity nitrogen, and then subjected to oxygen plasma treatment at 100-300W power for 1-3 minutes to improve surface hydrophilicity and reactivity.

[0039] In some embodiments, the prepolymerized electrolyte comprises 0.01~0.02 mol / L 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene and 0.005~0.01 mol / L FeCl3. The supporting electrolyte is 6H₂O and 0.1 mol / L; the solvent is an aqueous solution of acetonitrile.

[0040] In some embodiments, the volume ratio of acetonitrile to water is 1:1 to 3:1; the supporting electrolyte is selected from one of tetrabutylammonium perchlorate, lithium perchlorate, and potassium nitrate; after the electrolyte is prepared, it is ultrasonically dispersed for 30 to 60 minutes and then purged with nitrogen for 10 to 15 minutes to remove oxygen.

[0041] In some embodiments, the parameters for galvanostatic electrodeposition are a current density of 0.8~1.5 mA / cm². 2 The deposition time is 12-20 minutes and the deposition temperature is 20-30℃.

[0042] In this embodiment, the molecularly imprinted polymer sensitive film obtained by the above-described constant current electrodeposition operation has a thickness of 50~200 nm and is modified on the inner wall of the nanopores of the ordered anodic aluminum oxide porous functional layer, with a uniform surface, no agglomeration, and no cracks.

[0043] In some embodiments, the acid washing step of the conductive substrate / AAO / molecularly imprinted polymer sensitive film composite electrode is as follows: immerse the electrode after electrodeposition in a 0.1 mol / L HCl solution for 5-10 min at room temperature to 40°C and a stirring rate of 300-500 rpm. After elution, rinse with ultrapure water until neutral to remove the template Fe. 3+ .

[0044] In some embodiments, the Nafion-stabilized modified layer is prepared by drop-coating and vacuum drying from a 0.3–0.8 wt% Nafion solution in ethanol or isopropanol; the drop-coating amount of Nafion solution is 6–10 μL / cm. 2 The drying conditions were 70~80℃, vacuum degree ≤-0.09 MPa, and drying time 20~40 min; the resulting Nafion layer thickness was 10~30 nm, the surface was continuous, without pinholes or cracks, and the water contact angle was ≤30°.

[0045] Specifically, the preparation method of the electrochemical working electrode in this application is as follows: ITO / FTO was ultrasonically cleaned sequentially with acetone, ethanol, and water, and then dried with nitrogen to obtain a clean conductive substrate. A double-channel anodic aluminum oxide (AAO) film with a pore size of 30-80 nm was selected and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and ultrapure water for 10 min each. After drying with high-purity nitrogen, it was treated with oxygen plasma for 2 min to improve surface hydrophilicity and reactivity. The treated double-channel AAO film was then transferred to the surface of the hydrophilically modified conductive substrate using a water-floating method. The AAO was slowly lifted to make it flat and adhere. After drying at room temperature, it was hot-pressed at 100-120℃ and 0.3-0.5 MPa for 5-10 min to ensure that the AAO and the conductive substrate are firmly bonded without bubbles or warping, forming a conductive substrate / ordered anodic aluminum oxide porous functional layer that can be directly used for electrodeposition. Using acetonitrile:water = 2:1 (volume ratio) as solvent, 0.015 mol / L TCPPy functional monomer, 0.008 mol / L FFeCl3 template molecule, and 0.1 mol / L tetrabutylammonium perchlorate supporting electrolyte were added, and the mixture was ultrasonically stirred for 30 min until completely dissolved to obtain a prepolymer electrolyte. A three-electrode deposition system was constructed using a conductive substrate / ordered anodic alumina porous functional layer as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl (saturated KCl) as the reference electrode. The current density was set at 1.0 mA / cm². 2 TCPPy-Fe was grown in situ within AAO nanopores after a deposition time of 15 min. 3+ Molecularly imprinted polymer sensitive film, thus obtaining a conductive substrate / AAO / molecularly imprinted polymer sensitive film composite electrode; The conductive substrate / AAO / molecularly imprinted polymer sensitive film composite electrode was immersed in 0.1 mol / L HCl solution for 8 min to elute the template Fe. 3+ 8 μL of 0.5 wt% Nafion ethanol solution was dropped onto the electrode and dried under vacuum at 70 °C for 30 min to obtain the electrochemical working electrode.

[0046] This application provides an application of an electrochemical working electrode for the quantitative detection of ferric ions in a ferrous matrix.

[0047] In some embodiments, the ferrous matrix includes ferrous sulfate electrolyte, pickling waste liquid, iron-based material leachate, and battery precursor solution.

[0048] In some embodiments, the following steps are included: A three-electrode system consisting of an electrochemical working electrode, a counter electrode, and a reference electrode was constructed. The test solution was adjusted to acidity and a supporting electrolyte was added to obtain the test treatment solution; The three-electrode system was placed in the test solution, a reduction constant potential was applied, and the steady-state reduction current was collected under stirring. The concentration of ferric ions in the test solution was calculated using the standard curve method.

[0049] In some embodiments, the test solution is adjusted to 1.0~1.5; the voltage of the reduction constant potential is -0.15 ~ +0.1V.

[0050] Specifically, the steps for quantitatively detecting ferric ions in a ferrous matrix using an electrochemical working electrode are as follows: Using the electrochemical working electrode of this application as the working electrode, a platinum sheet or graphite electrode as the counter electrode, and an Ag / AgCl (saturated KCl) or saturated calomel electrode as the reference electrode; using 0.1~0.3 mol / L HClO4 as the supporting electrolyte, the pH of the test solution is adjusted to 0.5~1.0 to suppress Fe. 3+ Hydrolysis revealed that the test solution contained trace amounts of Fe. 3+ Fe 2+ Matrix solution; before detection, the working electrode was eluted and activated with 0.1 mol / L HCl to remove the template; a constant potential of -0.15 ~ +0.1 V (vs Ag / AgCl) was applied, and steady-state reduction current was collected for 40 ~ 60 s at a stirring rate of 600 ~ 900 rpm. A series of Fe solutions of different concentrations were prepared using the standard curve method. 3+ Standard solutions were used to measure their steady-state reduction currents under the same conditions, with Fe as the standard solution. 3+ A standard curve was established with concentration on the x-axis and steady-state reduction current on the y-axis. The Fe concentration in the test solution was then calculated from the standard curve based on the steady-state reduction current of the test solution.3+ The concentration.

[0051] This invention uses ITO / FTO or conductive carbon paper as a conductive substrate, and composites an ordered anodic alumina (AAO) porous functional layer on the surface. An in-situ layer of 1,3,6,8-tetra(3) alumina is prepared using a constant current electrodeposition method. A molecularly imprinted sensitive membrane using carboxyphenyl (CPI)pyrene as a functional monomer and ferric iron as a template is surface-modified with Nafion film to enhance stability. This invention utilizes the AAO nanoconfining effect and size-matching recognition, combined with specific coordination, to achieve highly selective and sensitive detection; the detection linear range is 0.01~50 mg / L, the detection limit is ≤0.004 mg / L, and the relative error is ≤5% under 100-fold excess ferric iron coexistence. No sample pretreatment is required, and the operation is simple and highly stable.

[0052] Source of raw materials Dual-channel AAO thin film: commercially available from Huayuan (China) or similar suppliers; preferably with a pore size of 50 nm, a thickness of 50~100 μm, and a pore density of approximately 10¹. 0 The isotropic double-channel AAO membrane has a porosity of approximately 15-20% and its channels are arranged in a hexagonal close-packed ordered structure.

[0053] Test solution: 1000 mg / L Fe 2+ Matrix solution, with added Fe 3+ Up to the theoretical concentration of 0.05 mg / L.

[0054] Fe 3+ A series of standard solutions: Fe at concentrations of 0.01, 0.1, 1, 10, and 50 mg / L. 3+ Standard solution.

[0055] The following specific embodiments further illustrate this solution.

[0056] Example 1 An electrochemical working electrode includes a conductive substrate, a composite layer, and a Nafion-stabilized modification layer covering the composite layer. The composite layer includes an ordered porous anodic alumina functional layer supported on the surface of the conductive substrate and a molecularly imprinted polymer sensitive membrane in situ grown within the nanopores of the ordered porous anodic alumina functional layer. The molecularly imprinted polymer sensitive membrane uses 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene as the functional monomer and Fe... 3+ It was synthesized in situ using a template molecule via constant current electrodeposition.

[0057] The preparation method of the electrochemical working electrode includes the following steps: A 1 cm × 1 cm ITO conductive glass was selected and ultrasonically cleaned in acetone, anhydrous ethanol, and ultrapure water for 10 min each, dried with high-purity nitrogen, and treated with oxygen plasma for 1–3 min to obtain a clean and hydrophilic conductive substrate. A 50 nm pore size double-channel AAO film was taken and ultrasonically cleaned in acetone, ethanol, and water for 5 min each, dried with nitrogen, and treated with oxygen plasma for 1 min. The treated AAO film was laid flat on the surface of deionized water to allow it to spread naturally without wrinkles. The hydrophilic ITO substrate was inserted obliquely into the water and slowly lifted from below, so that the AAO was uniformly adhered to the ITO conductive surface. After drying at room temperature, it was hot-pressed at 110 °C and 0.4 MPa for 8 min to form a conductive substrate / ordered anodic aluminum oxide porous functional layer. Using acetonitrile:water at a volume ratio of 2:1 as a mixed solvent, add sequentially: 0.015 mol / L TCPPy and 0.008 mol / L FeCl3. 6H₂O and 0.1 mol / L tetrabutylammonium perchlorate were mixed and placed in an ultrasonic cleaner, sonicated at room temperature for 30 min until the solid was completely dissolved, yielding a homogeneous and transparent prepolymerized electrolyte. Using a conductive substrate / ordered anodic alumina porous functional layer as the working electrode, a platinum sheet electrode as the counter electrode, and Ag / AgCl (saturated KCl) as the reference electrode, the three electrodes were immersed in the electrolyte and connected to an electrochemical workstation with a constant current density of 1.0 mA / cm². 2 The electrodeposition time was 15 min. After the deposition was completed, the electrode was removed and the surface was gently rinsed 3 times with ultrapure water to remove unreacted monomers and residual electrolytes, thus obtaining the conductive substrate / AAO / molecularly imprinted polymer sensitive film composite electrode. The conductive substrate / AAO / molecularly imprinted polymer sensitive film composite electrode was immersed in 0.1 mol / L HCl solution and allowed to stand at room temperature for 8 min. The template Fe within the imprinted film was eluted using hydrogen ion competitive coordination. 3+ After removal, rinse the electrode surface with ultrapure water until the pH of the rinsing solution is neutral, blow dry with nitrogen, then take 5 wt% Nafion stock solution, dilute with anhydrous ethanol to 0.5 wt%, sonicate for 10 min to disperse evenly, accurately pipette 8 μL of the diluted Nafion solution with a microsyringe, and evenly drop it onto the electrode imprint film surface. Place the electrode in a vacuum drying oven and vacuum dry at 70℃ for 30 min to obtain the electrochemical working electrode.

[0058] Example 2 A method for detecting ferric ions in a ferrous matrix using an electrochemical working electrode includes the following steps: Using 0.1 mol / L HClO4 as the supporting electrolyte, the pH of the test solution was adjusted to 1.0 to suppress Fe. 3+ Hydrolysis yields the test solution; Using the electrochemical working electrode of Example 1 as the working electrode, a platinum or graphite electrode as the counter electrode, and Ag / AgCl (saturated KCl) as the reference electrode, the working electrode was eluted with 0.1 mol / L HCl and activated before detection. The three-electrode system was placed in the test solution, a constant potential of -0.1 V (vs Ag / AgCl) was applied, the stirring rate was 800 rpm, and the steady-state reduction current was collected for 45 s. 3+ A linear equation was fitted using the concentrations of a series of standard solutions as the x-axis and the steady-state current as the y-axis. Then, the steady-state current of the test solution was measured under the same detection conditions. Substituting the obtained steady-state current value into the linear equation yielded the Fe concentration in the test solution. 3+ The concentration.

[0059] Comparative Example 1 A TCPPy imprinted electrode is identical to that in Example 1, except that the step of compositing a dual-channel AAO film onto a hydrophilic ITO substrate is replaced by: polishing the ITO substrate sequentially with 0.3μm and 0.05μm Al2O3 polishing powder to a mirror finish, rinsing with ultrapure water, ultrasonically cleaning with ethanol-water for 5 minutes each, and drying with nitrogen for later use.

[0060] Comparative Example 2 An AAO-based non-imprinted electrode is identical to Example 1 in all other respects, except that FeCl3 is not added. 6H2O.

[0061] Comparative Example 3 An AAO-based imprinted electrode is identical to Example 1 in all other respects, except that Nafion solution is not used.

[0062] Testing and Evaluation The linear equation obtained by testing the electrode of Example 1 according to the method of Example 2 is as follows: I(μA) = 0.48c(mg / L) + 0.015, R 2 =0.9994, Fe in the test solution 3+ The detected concentration was 0.052 mg / L.

[0063] The electrodes of Example 1 and each comparative example were tested according to the method of Example 2, and their performance was compared. The detection limit, linear range, simulated sample detection value, RSD, and 100 times Fe were compared for each detection system. 2+ Interference error and response retention rate after 20 consecutive detections were analyzed; and compared with the detection system of the o-phenanthroline spectrophotometric method. The steps of the o-phenanthroline spectrophotometric method are as follows: Step 1: Reagent preparation 0.5% o-phenanthroline ethanol solution, 10% hydroxylamine hydrochloride aqueous solution, acetate-sodium acetate buffer solution (pH=4.6); Step 2: Sample pretreatment Take 10 mL of the simulated sample to be tested, add 1 mL of hydroxylamine hydrochloride solution, shake well and let stand for 10 min to reduce Fe. 3+ Add 2 mL of o-phenanthroline solution and 5 mL of buffer solution, and bring the volume to 25 mL. Incubate for 15 min for color development.

[0064] Step 3: Detection Using a reagent blank as a reference, absorbance was measured at a wavelength of 510 nm, and quantification was performed using the standard curve method.

[0065] The performance evaluation results of different detection systems are shown in Table 1.

[0066] Table 1 Performance Evaluation Results

[0067] As shown in Table 1, this invention utilizes the AAO nanoconfining effect and size matching recognition, combined with specific coordination, to achieve highly selective and sensitive detection; the detection linear range is 0.01~50 mg / L, the detection limit is ≤0.004 mg / L, and the relative error is ≤5% under 100 times excess divalent iron coexistence. No sample pretreatment is required, and the operation is simple and stable.

[0068] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrochemical working electrode, characterized in that, The composite layer comprises a conductive substrate, a composite layer, and a Nafion-stabilized modification layer covering the composite layer; the composite layer includes an ordered porous anodic alumina functional layer supported on the surface of the conductive substrate and a molecularly imprinted polymer sensitive membrane in situ grown within the nanopores of the ordered porous anodic alumina functional layer; the molecularly imprinted polymer sensitive membrane uses 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene as the functional monomer and Fe... 3+ It was synthesized in situ using a template molecule via constant current electrodeposition.

2. A method for preparing the electrochemical working electrode as described in claim 1, characterized in that, Includes the following steps: After hydrophilization treatment, the double-channel AAO film is transferred to the surface of a cleaned conductive substrate and then hot-pressed to obtain a conductive substrate / ordered anodic aluminum oxide porous functional layer. 1,3,6,8-tetra(3-carboxyphenyl)pyrene, ferric salt, and supporting electrolyte were dispersed in a solvent to obtain a prepolymerized electrolyte; Using a conductive substrate / ordered anodic aluminum oxide porous functional layer as the working electrode, a constant current electrodeposition process is performed in the prepolymerized electrolyte to obtain a conductive substrate / AAO / molecularly imprinted polymer sensitive film composite electrode. After acid washing, the conductive substrate / AAO / molecularly imprinted polymer sensitive film composite electrode is drop-coated with Nafion ethanol solution and then vacuum dried to obtain the electrochemical working electrode.

3. The preparation method according to claim 2, characterized in that, The conductive substrate includes one or more of ITO conductive glass, FTO conductive glass, or conductive carbon paper; the surface resistivity of the conductive substrate is ≤20 Ω / sq.

4. The preparation method according to claim 2, characterized in that, The ordered anodic aluminum oxide porous functional layer has a pore size of 30~80 nm and a pore density of 10. 9 ~10 11 Hole / cm 2 The thickness is 50~200μm, the porosity is 10~20%, and the pores have a hexagonal close-packed ordered structure.

5. The preparation method according to claim 2, characterized in that, The steps for hydrophilization treatment of the dual-channel AAO membrane are as follows: after cleaning the dual-channel AAO membrane, it is dried with nitrogen gas and then subjected to oxygen plasma treatment.

6. The preparation method according to claim 2, characterized in that, The prepolymerized electrolyte comprises 0.01~0.02 mol / L 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene and 0.005~0.01 mol / L FeCl3. The supporting electrolyte is 6H₂O and 0.1 mol / L; the solvent is an aqueous solution of acetonitrile.

7. The preparation method according to claim 2, characterized in that, The parameters for the constant current electrodeposition are a current density of 0.8~1.5 mA / cm². 2 The deposition time is 12-20 minutes and the deposition temperature is 20-30℃.

8. An application of the electrochemical working electrode as described in claim 1 for the quantitative detection of ferric ions in a ferrous matrix.

9. The application according to claim 8, characterized in that, Includes the following steps: A three-electrode system consisting of the electrochemical working electrode, the counter electrode, and the reference electrode was constructed. The test solution was adjusted to acidity and a supporting electrolyte was added to obtain the test treatment solution; The three-electrode system was placed in the test solution, a reduction constant potential was applied, and the steady-state reduction current was collected under stirring. The concentration of ferric ions in the test solution was calculated using the standard curve method.

10. The application according to claim 9, characterized in that, The pH of the test solution is adjusted to 1.0~1.5; the voltage of the reduction constant potential is -0.15 ~ +0.1 V.

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