Bifunctional monomer synergistic molecularly imprinted electrochemical sensor as well as preparation method and application thereof

Abstract

The invention discloses a bifunctional monomer synergistic molecularly imprinted electrochemical sensor and a preparation method and application thereof, the preparation method comprises the following steps: polishing a glassy carbon electrode, and cleaning for later use after polishing; the method comprises the following steps: preparing an electrochemical polymerization solution of o-phenylenediamine (o-PD), 3, 4-diaminotoluene (3, 4-DAT) and perfluorooctane sulfonate, and taking a mixed solvent of a 0.1 M acetate buffer solution and methanol as a solvent; taking the pretreated glassy carbon electrode as a working electrode, putting a three-electrode system into an electrochemical polymerization solution, and performing electrochemical polymerization on molecularly imprinted poly-o-phenylenediamine and 3, 4-diaminotoluene by using a cyclic voltammetry to obtain a modified electrode; and cleaning the modified electrode to obtain the electrode. The electrochemical sensor has high sensitivity, excellent reproducibility, good stability and good recovery rate, and can rapidly detect perfluorooctane sulfonate in the environment with high sensitivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensor preparation, and in particular relates to a bifunctional monomer cooperative molecular imprinting electrochemical sensor and a preparation method and application thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Perfluorooctane sulfonate (PFOS) is a typical perfluorinated compound. Its hydrogen atoms are completely replaced by fluorine atoms, forming a highly stable carbon-fluorine bond. This structure makes PFOS extremely persistent, bioaccumulative, and toxic. Industrial activities are the primary source of PFOS release into the environment. Through various pathways, including water transport, surface runoff, atmospheric deposition, and volatilization, it is widely distributed and continuously accumulates in water bodies, soil, and sediments, posing a serious threat to terrestrial and aquatic ecosystems.

[0004] Human Exposure Routes and Health Risks: PFOS can enter the human body and accumulate through the food chain (particularly in seafood and meat). Numerous studies have confirmed that dietary intake is the primary route of PFOS exposure in humans, and that dietary intake is significantly correlated with PFOS concentrations in biological matrices such as blood. Epidemiological evidence indicates that even low-concentration exposure to PFOS can cause liver damage, kidney dysfunction, and adverse effects on metabolism, immune regulation, and reproductive health.

[0005] Given the widespread contamination and serious health risks of PFOS, accurate, sensitive, and efficient monitoring is crucial. However, the presence of trace amounts of PFOS in complex environmental matrices and biological samples, as well as matrix interference, pose significant challenges to existing detection technologies.

[0006] Currently, the most commonly used method for detecting perfluorooctane sulfonate is high-performance liquid chromatography-mass spectrometry / mass spectrometry (HPLC-MS / MS). This method has high sensitivity, but it has the disadvantages of complex pretreatment, high detection costs, long detection cycles, and inability to perform on-site testing. Electrochemical sensing technology, with its simplicity, sensitivity, and versatility, enables quantitative analysis by measuring changes in the electrical signal triggered by the redox reaction of the target. However, the inherent chemical inertness of PFOS makes it difficult to undergo direct electrochemical reactions. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a bifunctional monomer cooperative molecular imprinting electrochemical sensor and its preparation method and application. The electrochemical sensor has high sensitivity, excellent reproducibility, good stability and good recovery rate, and can quickly detect perfluorooctane sulfonate in the environment with high sensitivity.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions: In a first aspect, the present invention provides a method for preparing a bifunctional monomer cooperative molecular imprinting electrochemical sensor, comprising the following steps: Polish the glassy carbon electrode, clean it and set it aside; An electrochemical polymerization solution of o-phenylenediamine (o-PD), 3,4-diaminotoluene (3,4-DAT), and perfluorooctane sulfonate was prepared using a mixed solvent of 0.01-0.5 M acetate buffer and methanol; The pretreated glassy carbon electrode was used as the working electrode, and the three-electrode system was placed in an electrochemical polymerization solution. Cyclic voltammetry was used to electrochemically polymerize molecularly imprinted poly-o-phenylenediamine and 3,4-diaminotoluene to obtain a modified electrode. After cleaning the modified electrode, it is obtained.

[0009] In a second aspect, the present invention provides a bifunctional monomer cooperative molecular imprinting electrochemical sensor prepared by the preparation method.

[0010] In a third aspect, the present invention provides the use of the bifunctional monomer cooperative molecular imprinting electrochemical sensor in detecting perfluorooctane sulfonate.

[0011] The beneficial effects achieved by one or more embodiments of the present invention are as follows: The present invention uses two monomers, o-phenylenediamine and 3,4-diaminotoluene (3,4-DAT), to copolymerize to form a molecularly imprinted polymer. The purpose is to utilize the F···H weak interaction formed between the fluorine atoms (F) in the PFOS molecule and the hydrogen atoms (H) of the methyl and amino groups in the MIPs cavity to significantly improve the enrichment efficiency of PFOS on the sensor surface, thereby improving the detection performance, and addressing the many shortcomings of traditional perfluorooctane sulfonate (PFOS) detection methods, such as complex and time-consuming sample pretreatment, high operating technical requirements, and high costs.

[0012] The sensor is simple to operate and low-cost, allowing direct detection of PFOS in real samples without complex pretreatment steps. Its rapid detection, ease of operation, and excellent selectivity and sensitivity make it a promising tool for efficient, continuous, and rapid online detection of PFOS.

[0013] The bifunctional monomer-synergistic molecularly imprinted electrochemical sensor prepared by this invention exhibits excellent sensitivity and stability in detecting PFOS. It features a fast response, low background noise, and a low detection limit. Furthermore, in spiked recovery experiments with actual water samples and some everyday samples, the sensor demonstrated good recovery rates, making it suitable for rapid on-site detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0015] Figure 1 Schematic diagram of the construction of the bifunctional monomer cooperative molecular imprinting electrochemical sensor of the present invention and its detection of PFOS; Figure 2 This is a scanning electron microscope (SEM) image of the surface of the working electrode of the bifunctional monomer cooperative molecular imprinting electrochemical sensor prepared by the present invention; Figure 3 The electropolymerization cyclic voltammogram of the bifunctional monomer cooperative molecular imprinting electrochemical sensor prepared by the present invention; Figure 4 The differential pulse voltammogram of the invented sensor detecting PFOS when the ratio of o-phenylenediamine and 3,4-diaminotoluene was 10:1 during electrochemical polymerization; Figure 5 The current response change-concentration linear correlation curve of the invented sensor detecting PFOS when the ratio of o-phenylenediamine and 3,4-diaminotoluene is 10:1 during electrochemical polymerization; Figure 6 The differential pulse voltammogram of the invented sensor detecting PFOS when the ratio of o-phenylenediamine and 3,4-diaminotoluene was 5:1 during electrochemical polymerization; Figure 7 The linear correlation curve of the current response change and concentration of PFOS detected by the invented sensor with a ratio of o-phenylenediamine and 3,4-diaminotoluene of 5:1 during electrochemical polymerization; Figure 8 The differential pulse voltammogram of the invented sensor detecting PFOS when o-phenylenediamine and 3,4-diaminotoluene were electrochemically polymerized at a ratio of 2:1; Figure 9 The linear correlation curve of the current response change and concentration of PFOS detected by the invented sensor with a ratio of o-phenylenediamine and 3,4-diaminotoluene of 2:1 during electrochemical polymerization; Figure 10 The differential pulse voltammogram of the invented sensor detecting PFOS when o-phenylenediamine and 3,4-diaminotoluene were electrochemically polymerized at a ratio of 1:2; Figure 11 The current response change-concentration linear correlation curve of the invented sensor detecting PFOS when the ratio of o-phenylenediamine and 3,4-diaminotoluene is 1:2 during electrochemical polymerization; Figure 12The differential pulse voltammogram of the invented sensor detecting PFOS when o-phenylenediamine and 3,4-diaminotoluene were electrochemically polymerized at a ratio of 1:5; Figure 13 The current response change-concentration linear correlation curve of the invented sensor detecting PFOS when the ratio of o-phenylenediamine and 3,4-diaminotoluene is 1:5 during electrochemical polymerization; Figure 14 The differential pulse voltammogram of the invented sensor detecting PFOS when o-phenylenediamine and 3,4-diaminotoluene were electrochemically polymerized at a ratio of 1:1; Figure 15 The figure is a linear correlation curve of the current response change and concentration of PFOS detected by the invented sensor with a ratio of 1:1 of o-phenylenediamine and 3,4-diaminotoluene during electrochemical polymerization. DETAILED DESCRIPTION

[0016] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0017] In a first aspect, the present invention provides a method for preparing a bifunctional monomer cooperative molecular imprinting electrochemical sensor, comprising the following steps: Polish the glassy carbon electrode, clean it and set it aside; An electrochemical polymerization solution of o-phenylenediamine (o-PD), 3,4-diaminotoluene (3,4-DAT), and perfluorooctane sulfonate was prepared using a mixed solvent of 0.01-0.5 M acetate buffer and methanol; The pretreated glassy carbon electrode was used as the working electrode, and the three-electrode system was placed in an electrochemical polymerization solution. Cyclic voltammetry was used to electrochemically polymerize molecularly imprinted poly-o-phenylenediamine and 3,4-diaminotoluene to obtain a modified electrode. The modified electrode is rinsed with water, immersed in a methanol / water mixed solution for a set time, and then cleaned with methanol to obtain the modified electrode.

[0018] The acetate buffer is primarily responsible for providing ionic conductivity and maintaining a stable pH, which is essential for the stable electrochemical polymerization process. Perfluorooctane sulfonate (PFOS) has poor solubility in water. Using methanol as a solvent significantly reduces solvent polarity, greatly increasing the solubility of PFOS and ensuring its uniform dispersion in the polymerization solution. This prevents PFOS from precipitating and preventing effective polymerization with the monomer, thus ensuring efficient imprinting site formation. Therefore, the electrochemical polymerization solution uses a mixture of acetate buffer and methanol.

[0019] The core of this method involves electrochemically copolymerizing o-phenylenediamine (o-PD) and 3,4-diaminotoluene (3,4-DAT) in the presence of PFOS template molecules to form a molecularly imprinted polymer (MIP) film on the surface of a glassy carbon electrode. After PFOS is eluted, cavities remain in the film that are complementary to PFOS in shape, size, and functional groups. During detection, PFOS molecules can specifically rebind into these cavities, causing changes in the electrode's electrochemical signals (such as current and impedance), thereby enabling detection.

[0020] As a basic monomer and skeleton builder, o-phenylenediamine's amino group is oxidized during the cyclic voltammetry scan to form cationic free radicals, which then undergo a polymerization reaction to generate a conductive poly-o-phenylenediamine (PoPD) film. This film constitutes the main skeleton of the MIP. The benzene ring structure of PoPD provides a hydrophobic interaction site that can react hydrophobically with the carbon fluorine chain of PFOS. The amino group (-NH2) and imino group (-NH-) on the PoPD chain can provide hydrogen bond donor sites (NH), which can theoretically react with the sulfonate group (-SO3 ⁻ ) to form hydrogen bonds (NH...O=S). PoPD is known for its good film-forming properties, electrochemical stability, conductivity, and good mechanical strength, providing a stable substrate and conductive pathway for the sensor.

[0021] 3,4-Diaminotoluene is used as a functional comonomer to introduce a key recognition group (methyl group). The fluorine atom (F) in the PFOS molecule has a high electronegativity and a small atomic radius, making it a weak hydrogen bond acceptor. Although the CH bond on the methyl group of 3,4-DAT is generally not considered a strong hydrogen bond donor, its hydrogen atom (H) has a weak positive charge (δ + When spatially close, the F atom can form a weak F···HC interaction (also known as a fluorine-hydrogen bond or a C-H...F hydrogen bond) with the H atom on the methyl group. This interaction is a key innovation and enhancement in the specific recognition of PFOS. The presence of the methyl group also provides steric hindrance, helping to induce the formation of a cavity during polymerization that more precisely matches the local shape of the PFOS molecule (especially the alkyl portion near the sulfonic acid group). Copolymerization with o-PD can modulate the properties of the polymer membrane (such as hydrophilicity, flexibility, and pore size) to optimize the imprinting effect.

[0022] Perfluorooctane sulfonate as a template molecule.

[0023] During the detection process, PFOS molecules are efficiently and specifically "captured" into the imprinted cavity through the synergistic effect of the above-mentioned multiple interactions, resulting in measurable changes in the electrode interface properties (such as capacitance and electron transfer rate).

[0024] The preparation of molecularly imprinted polymers (MIPs) requires the removal of the template molecule after polymerization to form a cavity that matches the target. If the template is not completely eluted, residual PFOS will occupy the cavity, reducing the binding capacity during detection. If the cavity is blocked, it will not be able to specifically recognize the target.

[0025] PFOS binds to polymers through multiple forces (hydrophobic interaction, electrostatic attraction, and F···H interaction), and simple water washing cannot destroy these forces. Methanol reduces the polarity of the solution, weakening the hydrophobic interaction between the PFOS carbon fluoride chain and the polymer benzene ring. Methanol interferes with the water molecular network, reduces the dielectric constant, and weakens the sulfonic acid group (-SO3 - ) and polymer amino groups (-NH3 + The solubility of PFOS in methanol is significantly higher than that in pure water.

[0026] Methanol has the ability to swell polymers, which can relax the cross-linked network of poly (o-phenylenediamine) (PoPD) and poly (3,4-diaminotoluene) (PDAT), open the micropores closed by dense stacking during the polymerization process, and release the embedded PFOS molecules, especially the template located deep in the polymer.

[0027] After elution, the polymer undergoes local segmental rearrangement in the mixed solvent, bringing the cavity structure closer to the original shape of PFOS and improving subsequent identification efficiency. Adding water maintains the stability of the polymer, while pure methanol may cause excessive swelling or even exfoliation.

[0028] Finally, methanol is used for cleaning. Taking advantage of the strong volatility of methanol, the electrode surface is quickly dried, the polymer network is shrunk to the working state, the cavity configuration is fixed, and the residual mixed solvent is prevented from affecting subsequent detection.

[0029] In some embodiments, the polishing method is to use aluminum oxide powder with a particle size of 0.3 μm and 0.05 μm in sequence for polishing (to remove organic matter, grease, metal ions in the air or previous experimental residues adsorbed on the surface of the glassy carbon electrode during use, storage or transportation, and to eliminate scratches, pits, etc. that may exist on the electrode at the microscopic scale) until the electrode surface becomes mirror-like, and then repeatedly ultrasonically clean it in ultrapure water and anhydrous ethanol, and dry it for use.

[0030] In some embodiments, in the electrochemical polymerization solution, the concentration of o-phenylenediamine is 1-20 mM, the concentration of 3,4-diaminotoluene is 1-50 mM, and the concentration of perfluorooctane sulfonate is 0.1-2 mM.

[0031] Preferably, in the electrochemical polymerization solution, the concentration of o-phenylenediamine is 5-15 mM, the concentration of 3,4-diaminotoluene is 1-20 mM, and the concentration of perfluorooctane sulfonate is 0.5-1.5 mM.

[0032] Further preferably, in the electrochemical polymerization solution, the concentration of o-phenylenediamine is 7-12 mM, the concentration of 3,4-diaminotoluene is 7-12 mM, and the concentration of perfluorooctane sulfonate is 0.7-1.2 mM.

[0033] More preferably, in the electrochemical polymerization solution, the concentration of o-phenylenediamine is 10 mM, the concentration of 3,4-diaminotoluene is 10 mM, and the concentration of perfluorooctane sulfonate is 1 mM.

[0034] In some embodiments, the volume ratio of acetate buffer to methanol in the mixed solvent is 1-5:1, preferably 1-3:1.

[0035] Preferably, the concentration of the acetate buffer is 0.05-0.15M.

[0036] In some embodiments, the scan rate of the cyclic voltammetry is 10-100 mV s -1 , the voltage range is 0.0-1.0V, and the number of cycles is 20-30.

[0037] Preferably, the scan rate of the cyclic voltammetry is 30-70 mV s -1 , the voltage range is 0.0-1.0V, and the number of cycles is 22-28.

[0038] Further preferably, the scan rate of the cyclic voltammetry is 50 mV s -1 , the voltage range is 0.0-1.0V, and the number of cycles is 25.

[0039] In some embodiments, in the methanol / water mixed solution, the volume ratio of methanol to water is 1:0.8-1.2, preferably 1:1.

[0040] Preferably, the modified electrode is immersed in the methanol / water mixed solution for 5-15 minutes, preferably 10 minutes.

[0041] In a second aspect, the present invention provides a bifunctional monomer cooperative molecular imprinting electrochemical sensor prepared by the preparation method.

[0042] In a third aspect, the present invention provides the use of the bifunctional monomer cooperative molecular imprinting electrochemical sensor in detecting perfluorooctane sulfonate.

[0043] The application includes the following steps: Step 1: Immerse the electrode in a solution containing a known concentration of PFOS and stir for 15 minutes; In step 2, differential pulse voltammetry was used to evaluate the interaction between PFOS and the modified electrode in FcCOOH solution.

[0044] In step 2, the perfluorooctane sulfonate in the sample is qualitatively determined; and a calibration standard curve is obtained by comparing the change in the detected current intensity with the concentration of the corresponding known perfluorooctane sulfonate, so as to quantitatively detect the concentration of the perfluorooctane sulfonate.

[0045] In step 2, differential pulse voltammetry was used to detect perfluorooctane sulfonate in FcCOOH solution using a three-electrode system: a modified glassy carbon electrode as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum wire electrode as the counter electrode; the potential range was 0.0-0.5 V; the pulse width was 25.0 ms; the pulse amplitude was 25.0 mV; the incremental potential was 4.0 mV; and the scan rate was 20 mV s -1 ; The concentration of FcCOOH is 0.5 mM.

[0046] This electrochemical sensor can be used to detect perfluorooctane sulfonate in actual water environments and some daily samples.

[0047] The present invention will be further described below with reference to the embodiments.

[0048] Example 1 The ratio of o-phenylenediamine to 3,4-diaminotoluene during electrochemical polymerization is 10:1.

[0049] A method for preparing a bifunctional monomer cooperative molecular imprinting electrochemical sensor comprises the following steps: (1) Polishing with aluminum oxide powder with a particle size of 0.3 μm and 0.05 μm in sequence until the electrode surface is mirror-like, then repeatedly ultrasonically cleaning in ultrapure water and anhydrous ethanol, drying and setting aside to obtain a pretreated glassy carbon electrode; (2) Prepare an electrochemical polymerization solution composed of 0.1 M acetate buffer (pH 5.8) / methanol (2:1, v / v) containing 10.0 mM o-phenylenediamine (o-PD), 1.0 mM 3,4-diaminotoluene (3,4-DAT), and 1.0 mM perfluorooctane sulfonate; (3) The pretreated glassy carbon electrode was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The three-electrode system was placed in the electrochemical polymerization solution. Electrochemical polymerization of molecularly imprinted poly(o-phenylenediamine) and 3,4-diaminotoluene (3,4-DAT) was performed using cyclic voltammetry. The scan rate of cyclic voltammetry was 50 mV s -1 , the potential range is 0.0-1.0 V, and the number of cycles is 25 times; (4) After the polymerization is completed, the modified electrode is rinsed with water and immersed in a methanol / water solution with gentle stirring. The volume ratio of methanol to water in the methanol / water solution is 1:1. The immersion time is 10 minutes, and then washed with methanol.

[0050] Figure 2 This is a scanning electron microscope (SEM) image of the surface of the working electrode of the bifunctional monomer cooperative molecular imprinting electrochemical sensor prepared in the present invention; the morphology of the surface of the working electrode of the bifunctional monomer cooperative molecular imprinting electrochemical sensor was observed by scanning electron microscopy (SEM), showing a smooth surface morphology, indicating that the molecular imprinting membrane on the electrode surface was successfully prepared.

[0051] Figure 3 The electropolymerization cyclic voltammogram of the bifunctional monomer cooperative molecular imprinting electrochemical sensor prepared by the present invention.

[0052] As electrochemical polymerization progressed, redox reactions between o-phenylenediamine and 3,4-diaminotoluene molecules on the electrode surface caused the current to increase, indicating an increasing amount of polymer deposited on the working electrode. In the first scan, an anodic peak at approximately 0.51 V vs. Ag / AgCl was detected, and this peak current gradually decreased over the following cycles. After 25 cycles of electrochemical polymerization, the current stabilized, indicating completion of polymerization.

[0053] A method for rapidly detecting perfluorooctane sulfonate using the electrochemical sensor comprises the following steps: Step 1: immerse the modified electrode in a solution containing a known concentration of perfluorooctane sulfonate and stir for 15 minutes; Step 2: Differential pulse voltammetry is used to evaluate the interaction between PFOS and the modified electrode in FcCOOH solution to qualitatively determine the PFOS in the sample. A calibration curve is obtained by comparing the change in detected current intensity with the concentration of known PFOS to quantitatively determine the concentration of PFOS.

[0054] Differential pulse voltammetry was used to detect PFOS in FcCOOH solution using a three-electrode system: a modified glassy carbon electrode as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum wire electrode as the counter electrode; the potential range was 0.0–0.5 V; the pulse width was 25.0 ms; the pulse amplitude was 25.0 mV; the incremental potential was 4.0 mV; and the scan rate was 20 mV s. -1 ; The concentration of FcCOOH is 0.5 mM.

[0055] The differential pulse voltammogram of perfluorooctane sulfonate detected by the prepared electrochemical sensor is shown in Figure 4. Figure 4 As shown; The electrode of the present invention uses differential pulse voltammetry to detect the response current of known concentrations of perfluorooctane sulfonate, and a correlation curve between the current response change and the perfluorooctane sulfonate concentration can be obtained ( Figure 5 ). The linear regression equation for the sensor's detection of perfluorooctane sulfonate was y=0.09122x+0.0214, with a linear range of 0-20 nM, a correlation coefficient of 0.99369, a response sensitivity of 0.09122 μA / nM, and a detection limit as low as 0.0268 nM.

[0056] Example 2 The ratio of o-phenylenediamine to 3,4-diaminotoluene during electrochemical polymerization is 5:1.

[0057] A method for preparing a bifunctional monomer cooperative molecular imprinting electrochemical sensor comprises the following steps: (1) Polishing with aluminum oxide powder with a particle size of 0.3 μm and 0.05 μm in sequence until the electrode surface is mirror-like, then repeatedly ultrasonically cleaning in ultrapure water and anhydrous ethanol, drying and setting aside to obtain a pretreated glassy carbon electrode; (2) Prepare an electrochemical polymerization solution composed of 0.1 M acetate buffer (pH 5.8) / methanol (2:1, v / v) containing 10.0 mM o-phenylenediamine (o-PD), 2.0 mM 3,4-diaminotoluene (3,4-DAT), and 1.0 mM perfluorooctane sulfonate; (3) The pretreated glassy carbon electrode was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The three-electrode system was placed in the electrochemical polymerization solution. Electrochemical polymerization of molecularly imprinted poly(o-phenylenediamine) and 3,4-diaminotoluene (3,4-DAT) was performed using cyclic voltammetry. The scan rate of cyclic voltammetry was 50 mV s -1 , the potential range is 0.0-1.0 V, and the number of cycles is 25 times; (4) After the polymerization is completed, the modified electrode is rinsed with water and immersed in a methanol / water solution with gentle stirring. The volume ratio of methanol to water in the methanol / water solution is 1:1. The immersion time is 10 minutes, and then washed with methanol.

[0058] Figure 6 The differential pulse voltammogram of the invented sensor detecting PFOS when the ratio of o-phenylenediamine and 3,4-diaminotoluene was 5:1 during electrochemical polymerization; Figure 7 This is a linear correlation curve of the current response change and concentration of PFOS detected by the invented sensor when the ratio of o-phenylenediamine and 3,4-diaminotoluene is 5:1 during electrochemical polymerization.

[0059] The electrode of the present invention uses differential pulse voltammetry to detect the response current of known concentrations of perfluorooctane sulfonate, and a correlation curve between the current response change and the perfluorooctane sulfonate concentration can be obtained ( Figure 7 ). The linear regression equation for the sensor's detection of perfluorooctane sulfonate was y=0.09988x-0.0088, with a linear range of 0-20 nM, a correlation coefficient of 0.99165, a response sensitivity of 0.09988 μA / nM, and a detection limit as low as 0.0245 nM.

[0060] Example 3 The ratio of o-phenylenediamine to 3,4-diaminotoluene during electrochemical polymerization is 2:1.

[0061] A method for preparing a bifunctional monomer cooperative molecular imprinting electrochemical sensor comprises the following steps: (1) Polishing with aluminum oxide powder with a particle size of 0.3 μm and 0.05 μm in sequence until the electrode surface is mirror-like, then repeatedly ultrasonically cleaning in ultrapure water and anhydrous ethanol, drying and setting aside to obtain a pretreated glassy carbon electrode; (2) Prepare an electrochemical polymerization solution composed of 0.1 M acetate buffer (pH 5.8) / methanol (2:1, v / v) containing 10.0 mM o-phenylenediamine (o-PD), 5.0 mM 3,4-diaminotoluene (3,4-DAT), and 1.0 mM perfluorooctane sulfonate; (3) The pretreated glassy carbon electrode was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The three-electrode system was placed in the electrochemical polymerization solution. Electrochemical polymerization of molecularly imprinted poly(o-phenylenediamine) and 3,4-diaminotoluene (3,4-DAT) was performed using cyclic voltammetry. The scan rate of cyclic voltammetry was 50 mV s -1 , the potential range is 0.0-1.0 V, and the number of cycles is 25 times; (4) After the polymerization is completed, the modified electrode is rinsed with water and immersed in a methanol / water solution with gentle stirring. The volume ratio of methanol to water in the methanol / water solution is 1:1. The immersion time is 10 minutes, and then washed with methanol.

[0062] Figure 8 The differential pulse voltammogram of the invented sensor detecting PFOS during electrochemical polymerization of o-phenylenediamine and 3,4-diaminotoluene in a ratio of 2:1.

[0063] Figure 9 The figure is a linear correlation curve of the current response change and concentration of PFOS detected by the invented sensor with a ratio of o-phenylenediamine and 3,4-diaminotoluene of 2:1 during electrochemical polymerization.

[0064] The electrode of the present invention uses differential pulse voltammetry to detect the response current of known concentrations of perfluorooctane sulfonate, and a correlation curve between the current response change and the perfluorooctane sulfonate concentration can be obtained ( Figure 9 ). The linear regression equation for the sensor's detection of perfluorooctane sulfonate was y=0.08294x-0.0863, with a linear range of 0-15 nM, a correlation coefficient of 0.95142, a response sensitivity of 0.08294 μA / nM, and a detection limit as low as 0.0295 nM.

[0065] Example 4 The ratio of o-phenylenediamine to 3,4-diaminotoluene during electrochemical polymerization is 1:2.

[0066] A method for preparing a bifunctional monomer cooperative molecular imprinting electrochemical sensor comprises the following steps: (1) Polishing with aluminum oxide powder with a particle size of 0.3 μm and 0.05 μm in sequence until the electrode surface is mirror-like, then repeatedly ultrasonically cleaning in ultrapure water and anhydrous ethanol, drying and setting aside to obtain a pretreated glassy carbon electrode; (2) Prepare an electrochemical polymerization solution consisting of 0.1 M acetate buffer (pH 5.8) / methanol (2:1, v / v) containing 10.0 mM o-phenylenediamine (o-PD), 20.0 mM 3,4-diaminotoluene (3,4-DAT), and 1.0 mM perfluorooctane sulfonate; (3) The pretreated glassy carbon electrode was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The three-electrode system was placed in the electrochemical polymerization solution. Electrochemical polymerization of molecularly imprinted poly(o-phenylenediamine) and 3,4-diaminotoluene (3,4-DAT) was performed using cyclic voltammetry. The scan rate of cyclic voltammetry was 50 mV s -1 , the potential range is 0.0-1.0 V, and the number of cycles is 25 times; (4) After the polymerization is completed, the modified electrode is rinsed with water and immersed in a methanol / water solution with gentle stirring. The volume ratio of methanol to water in the methanol / water solution is 1:1. The immersion time is 10 minutes, and then washed with methanol.

[0067] Figure 10The differential pulse voltammogram of the invented sensor detecting PFOS when o-phenylenediamine and 3,4-diaminotoluene were electrochemically polymerized at a ratio of 1:2; Figure 11 The figure is a linear correlation curve of the current response change and concentration of PFOS detected by the invented sensor with a ratio of o-phenylenediamine and 3,4-diaminotoluene of 1:2 during electrochemical polymerization.

[0068] The electrode of the present invention uses differential pulse voltammetry to detect the response current of known concentrations of perfluorooctane sulfonate, and a correlation curve between the current response change and the perfluorooctane sulfonate concentration can be obtained ( Figure 13 ). The linear regression equation for the sensor's detection of perfluorooctane sulfonate was y=0.0757x+0.0668, with a linear range of 0-20 nM, a correlation coefficient of 0.96298, a response sensitivity of 0.0757 μA / nM, and a detection limit as low as 0.0323 nM.

[0069] Example 5 The ratio of o-phenylenediamine to 3,4-diaminotoluene during electrochemical polymerization is 1:5.

[0070] A method for preparing a bifunctional monomer cooperative molecular imprinting electrochemical sensor comprises the following steps: (1) Polishing with aluminum oxide powder with a particle size of 0.3 μm and 0.05 μm in sequence until the electrode surface is mirror-like, then repeatedly ultrasonically cleaning in ultrapure water and anhydrous ethanol, drying and setting aside to obtain a pretreated glassy carbon electrode; (2) Prepare an electrochemical polymerization solution composed of 0.1 M acetate buffer (pH 5.8) / methanol (2:1, v / v) containing 10.0 mM o-phenylenediamine (o-PD), 50.0 mM 3,4-diaminotoluene (3,4-DAT), and 1.0 mM perfluorooctane sulfonate; (3) The pretreated glassy carbon electrode was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The three-electrode system was placed in the electrochemical polymerization solution. Electrochemical polymerization of molecularly imprinted poly(o-phenylenediamine) and 3,4-diaminotoluene (3,4-DAT) was performed using cyclic voltammetry. The scan rate of cyclic voltammetry was 50 mV s -1 , the potential range is 0.0-1.0 V, and the number of cycles is 25 times; (4) After the polymerization is completed, the modified electrode is rinsed with water and immersed in a methanol / water solution with gentle stirring. The volume ratio of methanol to water in the methanol / water solution is 1:1. The immersion time is 10 minutes, and then washed with methanol.

[0071] Figure 12 The differential pulse voltammogram of the invented sensor detecting PFOS when o-phenylenediamine and 3,4-diaminotoluene were electrochemically polymerized at a ratio of 1:5; Figure 13 This is a linear correlation curve of the current response change and concentration of PFOS detected by the invented sensor when the ratio of o-phenylenediamine and 3,4-diaminotoluene is 1:5 during electrochemical polymerization.

[0072] The electrode of the present invention uses differential pulse voltammetry to detect the response current of known concentrations of perfluorooctane sulfonate, and a correlation curve between the current response change and the perfluorooctane sulfonate concentration can be obtained ( Figure 13 ). The linear regression equation for the sensor's detection of perfluorooctane sulfonate was y=0.06496x+0.094, with a linear range of 0-20 nM, a correlation coefficient of 0.96994, a response sensitivity of 0.06496 μA / nM, and a detection limit as low as 0.0377 nM.

[0073] Example 6 The ratio of o-phenylenediamine to 3,4-diaminotoluene during electrochemical polymerization is 1:1.

[0074] A method for preparing a bifunctional monomer cooperative molecular imprinting electrochemical sensor comprises the following steps: (1) Polishing with aluminum oxide powder with a particle size of 0.3 μm and 0.05 μm in sequence until the electrode surface is mirror-like, then repeatedly ultrasonically cleaning in ultrapure water and anhydrous ethanol, drying and setting aside to obtain a pretreated glassy carbon electrode; (2) Prepare an electrochemical polymerization solution composed of 0.1 M acetate buffer (pH 5.8) / methanol (2:1, v / v) containing 10.0 mM o-phenylenediamine (o-PD), 10.0 mM 3,4-diaminotoluene (3,4-DAT), and 1.0 mM perfluorooctane sulfonate; (3) The pretreated glassy carbon electrode was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The three-electrode system was placed in the electrochemical polymerization solution. Electrochemical polymerization of molecularly imprinted poly(o-phenylenediamine) and 3,4-diaminotoluene (3,4-DAT) was performed using cyclic voltammetry. The scan rate of cyclic voltammetry was 50 mV s -1 , the potential range is 0.0-1.0 V, and the number of cycles is 25 times; (4) After the polymerization is completed, the modified electrode is rinsed with water and immersed in a methanol / water solution with gentle stirring. The volume ratio of methanol to water in the methanol / water solution is 1:1. The immersion time is 10 minutes, and then washed with methanol.

[0075] Figure 14 The differential pulse voltammogram of the invented sensor detecting perfluorooctane sulfonate when o-phenylenediamine and 3,4-diaminotoluene were electrochemically polymerized at a ratio of 1:1; Figure 15 The figure is a linear correlation curve of the current response change and concentration of the sensor invented when the ratio of o-phenylenediamine and 3,4-diaminotoluene is 1:1 during electrochemical polymerization to detect perfluorooctane sulfonate.

[0076] The electrode of the present invention uses differential pulse voltammetry to detect the response current of known concentrations of perfluorooctane sulfonate, and a correlation curve between the current response change and the perfluorooctane sulfonate concentration can be obtained ( Figure 15 ). The linear regression equation for the sensor's detection of perfluorooctane sulfonate was y=0.10192x-0.0446, with a linear range of 0-20 nM, a correlation coefficient of 0.99462, a response sensitivity of 0.10192 μA / nM, and a detection limit as low as 0.0240 nM.

[0077] Comparative Example 1 The difference from Example 6 is that 3,4-diaminotoluene is omitted, and the other aspects are the same as Example 6. The detection limit is 0.0446 nM.

[0078] Comparative Example 2 The difference from Example 6 is that an equal amount of 3,4-diaminotoluene is replaced by o-phenylenediamine, and all other aspects are the same as Example 6. The detection limit is 0.1528 nM.

[0079] To verify the performance and applicability of the present invention, a molecularly imprinted electrochemical sensor (Example 6) prepared with an optimal ratio of o-phenylenediamine and 3,4-diaminotoluene of 1:1 was used to detect perfluorooctane sulfonate in three water samples filtered through a 0.22 μm filter membrane. The three water samples were deionized water, tap water, and lake water.

[0080] Given that the background concentration of PFOS in environmental samples was below the method's detection limit, spike recovery experiments were conducted to simulate actual contamination scenarios by spiking PFOS standards at low (1 nM), medium (10 nM), and high (20 nM) concentrations into three water matrix samples to verify the reliability of the method. The test results are shown in Table 1. The spike recovery rates for the three matrix samples ranged from 89.6% to 103.4%.

[0081] Table 1 Detection of PFOS in actual water samples by dual-functional monomer cooperative molecular imprinting electrochemical sensor

[0082] Perfluorooctane sulfonate (PFOS) is widely used in waterproof coatings and food packaging materials. In daily life, humans are easily exposed to PFOS, which can pose health risks. Therefore, the prepared sensor was used to detect PFOS in leachates from commonly used products, such as raincoats and takeout packaging.

[0083] Before measurement, samples were pretreated according to the national standard (GB / T 33893-2017). The pretreatment process was as follows: 1 g of sample was cut into 1 cm × 1 cm pieces. A 1 g sample was weighed and placed in a 50 mL stoppered Erlenmeyer flask. 40 mL of methanol was added, and the flask was sealed, completely immersing the sample. Ultrasonic extraction was performed in a water bath at 60°C for 1 h. After cooling to room temperature, the extract was filtered through a 0.22 μm filter membrane. After filtration, the volume was rotary evaporated to 5 mL, then transferred to a volumetric flask and diluted to 20 mL with water. This served as the sample extract for measurement.

[0084] Finally, PFOS was detected in both raincoat and food packaging samples, with contents of 0.67 nM and 1.14 nM, respectively, as shown in Table 2.

[0085] Table 2 Detection of PFOS in actual samples by dual-functional monomer cooperative molecular imprinting electrochemical sensor

[0086] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a bifunctional monomer cooperative molecularly imprinted electrochemical sensor, characterized in that: The steps include: Polish the glassy carbon electrode, clean it and set it aside; preparing an electrochemical polymerization solution of o-phenylenediamine, 3,4-diaminotoluene and perfluorooctane sulfonate, wherein the solvent is a mixed solvent of 0.01-0.5 M acetate buffer and methanol; The pretreated glassy carbon electrode was used as the working electrode, and the three-electrode system was placed in an electrochemical polymerization solution. Cyclic voltammetry was used to electrochemically polymerize molecularly imprinted poly-o-phenylenediamine and 3,4-diaminotoluene to obtain a modified electrode. The modified electrode is rinsed with water, immersed in a methanol / water mixed solution for a set time, and then cleaned with methanol to obtain the modified electrode.

2. The method for preparing a bifunctional monomer cooperative molecularly imprinted electrochemical sensor according to claim 1, characterized in that: The polishing method comprises the following steps: sequentially polishing with aluminum oxide powder having a particle size of 0.3 μm and 0.05 μm until the electrode surface becomes mirror-like, then repeatedly ultrasonically cleaning in ultrapure water and anhydrous ethanol, and drying for later use.

3. The method for preparing a bifunctional monomer cooperative molecularly imprinted electrochemical sensor according to claim 1, wherein: In the electrochemical polymerization solution, the concentration of o-phenylenediamine is 1-20 mM, the concentration of 3,4-diaminotoluene is 1-50 mM, and the concentration of perfluorooctane sulfonate is 0.1-2 mM; Preferably, in the electrochemical polymerization solution, the concentration of o-phenylenediamine is 5-15 mM, the concentration of 3,4-diaminotoluene is 1-20 mM, and the concentration of perfluorooctane sulfonate is 0.5-1.5 mM; Preferably, in the electrochemical polymerization solution, the concentration of o-phenylenediamine is 7-12 mM, the concentration of 3,4-diaminotoluene is 7-12 mM, and the concentration of perfluorooctane sulfonate is 0.7-1.2 mM.

4. The method for preparing a bifunctional monomer cooperative molecularly imprinted electrochemical sensor according to claim 1, characterized in that: In the mixed solvent, the volume ratio of acetate buffer to methanol is 1-5:1, preferably 1-3:1; Preferably, the concentration of the acetate buffer is 0.05-0.15M.

5. The method for preparing a bifunctional monomer cooperative molecularly imprinted electrochemical sensor according to claim 1, wherein: The scan rate of the cyclic voltammetry was 10-100 mV s -1 , the voltage range is 0.0-1.0V, and the number of cycles is 20-30.

6. The method for preparing a bifunctional monomer cooperative molecularly imprinted electrochemical sensor according to claim 1, wherein: The scan rate of the cyclic voltammetry was 30-70 mV s -1 , the voltage range is 0.0-1.0V, and the number of cycles is 22-28.

7. The method for preparing a bifunctional monomer cooperative molecularly imprinted electrochemical sensor according to claim 1, characterized in that: In the methanol / water mixed solution, the volume ratio of methanol to water is 1:0.8-1.2, preferably 1:

1.

8. The method for preparing a bifunctional monomer cooperative molecularly imprinted electrochemical sensor according to claim 1, characterized in that: The modified electrode is immersed in the methanol / water mixed solution for 5-15 minutes, preferably 10 minutes.

9. A bifunctional monomer cooperative molecular imprinting electrochemical sensor, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the bifunctional monomer cooperative molecular imprinting electrochemical sensor according to claim 9 in detecting perfluorooctane sulfonate.

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