MXene-polymeric ionic liquid electrochemical modification material and application thereof

Abstract

The application discloses an MXene-polymerization ionic liquid electrochemical modification material and application thereof. The electrochemical modification material is MXene-PILs, and a preparation method is as follows: MXene few-layer colloidal solution is blended with polymerization ionic liquid to form a uniform and stable solution, then the obtained mixed solution is freeze-dried to prepare a solid sample, and finally the MXene-PILs is obtained. The prepared electrochemical modification material not only improves the oxidation resistance of MXene nanosheets, but also has excellent electrical conductivity and biocompatibility. The material is applied to a biosensor, and the application in the fields of electrochemical analysis and biosensing is expanded.

Description

Technical Field

[0001] This invention relates to the field of bioelectrochemistry, specifically to an MXene-polymer ionic liquid electrochemical modification material and its application. Background Technology

[0002] Two-dimensional transition metal carbides (or nitrides) MXene (Ti3C2T) x MXene, possessing a graphene-like 2D layered structure, excellent metallic conductivity, biocompatibility, and good dispersibility in aqueous phases, has been widely used in various fields such as metals, ion batteries, supercapacitors, fuel cells, and electronic devices. However, MXene exhibits properties similar to the generated O2. - The nanosheets are prone to degradation due to reactions with free radicals such as ·OH. Therefore, they are easily oxidized in humid or aquatic environments, leading to the disintegration of the 2D layered structure and severely impairing their electrical conductivity, thus limiting the practical applications of MXene.

[0003] Imidazole-based ionic liquids have been reported to act as quenchers, preventing reactive oxygen species (ROS), such as hydroxyl radicals (·OH), from entering the surface of 2D materials and reducing the reaction between free radicals and MXene sheets. Simultaneously, ionic liquids are also ideal materials for immobilizing enzymes, possessing biocompatibility, thermal stability, chemical stability, a wide electrochemical window, and high conductivity. However, most reported methods rely on the use of large quantities of ionic liquid monomers, which is impractical for large-scale production. Therefore, this study investigates a low-cost, highly stable method for modifying MXene nanosheets with polymeric ionic liquids (PILs), meeting practical production needs.

[0004] A biosensor is an instrument that senses biological material and converts its concentration into an electrical signal for detection. It consists of immobilized biological material, a transducer, and a signal amplification device, and has received considerable attention in recent years. Two-dimensional transition metal carbides (or nitrides) MXene (Ti3C2T) x MXene possesses a 2D layered structure similar to graphene, exhibiting a large specific surface area and many excellent physicochemical properties, such as superior metallic conductivity, biocompatibility, good dispersibility in aqueous phase, and reducibility, making it an ideal material for preparing electrochemical biosensors. Therefore, polymeric ionic liquids can be introduced into MXene to compensate for its inherent shortcomings while enhancing its biosensing performance. This also facilitates enzyme loading, leverages the synergistic effects of composite materials, and allows for the preparation of MXene-based AChE electrochemical biosensors with superior performance. Summary of the Invention

[0005] This invention utilizes a method of blending MXene with polymeric ionic liquids to prepare MXene-PILs composite materials. Then, acetylcholinesterase, capable of specifically recognizing organophosphorus pesticides, is further introduced and immobilized on the surface of a glassy carbon electrode to construct an MXene-based acetylcholinesterase electrochemical biosensor. Results show that the prepared composite material possesses both excellent conductivity and biocompatibility, maintaining the biological activity of the immobilized enzyme while promoting direct electron transfer between the enzyme and the electrode surface. It can be applied in fields such as electrochemical analysis and biosensing.

[0006] The technical solution adopted in this invention is: an MXene-polymer ionic liquid electrochemical modification material, wherein the MXene-polymer ionic liquid electrochemical modification material is MXene-PILs, and the preparation method includes the following steps:

[0007] 1) Dissolve 1-vinyl-3-ethylimidazolium bromide monomer in chloroform, add azobisisobutyronitrile (AIBN), stir to dissolve, heat to 60-70°C in N2 atmosphere, reflux for 5-6 hours, after the reaction is completed, cool to room temperature, wash the product with chloroform, and dry in a freeze dryer to obtain polymeric ionic liquids (PILs).

[0008] 2) Mix the MXene colloidal solution with polymeric ionic liquids (PILs) and sonicate for 30-40 minutes to form a homogeneous and stable solution. Then freeze-dry the resulting mixed solution to obtain MXene-PILs.

[0009] Furthermore, in the above-mentioned MXene-polymer ionic liquid electrochemical modification material, in step 2), the concentration of the MXene colloidal solution is 2-8 mg / mL, and the material-liquid ratio is MXene colloidal solution:polymer ionic liquid = 1 mL: 20-30 mg.

[0010] An MXene-polymer ionic liquid-based electrochemically modified electrode is prepared using the aforementioned MXene-polymer ionic liquid electrochemically modified material MXene-PILs. The preparation method includes the following steps: First, using a layer-by-layer drop-addition method, the MXene-PILs solution is drop-coated onto the surface of a pretreated glassy carbon electrode (GCE) and dried at room temperature. Then, an acetylcholinesterase (AChE) solution is drop-coated onto the MXene-PILs surface and dried at 2–6 °C. After drying, Nafion solution is drop-coated and dried again at 2–6 °C to obtain the MXene-polymer ionic liquid-based electrochemically modified electrode (AChE / MXene-PILs / GCE).

[0011] Furthermore, in the aforementioned MXene-polymer ionic liquid-based electrochemically modified electrode, the concentration of the MXene-PILs solution is 2–8 mg / mL, the concentration of the acetylcholinesterase (AChE) solution is 150–250 U / mL, and the concentration of the Nafion solution is 0.2–0.8 wt%; by volume ratio, the ratio of MXene-PILs solution:acetylcholinesterase (AChE) solution:Nafion solution is 7:9:5.

[0012] Furthermore, in the aforementioned MXene-polymer ionic liquid-based electrochemically modified electrode, the pH value of the acetylcholinesterase (AChE) solution is 7-8.

[0013] The MXene-polymer ionic liquid-based electrochemically modified electrode provided by this invention is used as a biosensor in the electrochemical qualitative and quantitative detection of pesticides.

[0014] Furthermore, the pesticide in question is an organophosphorus pesticide.

[0015] Furthermore, the organophosphorus pesticide is methyl parathion.

[0016] Furthermore, the method is as follows: The above-mentioned MXene-polymer ionic liquid-based electrochemically modified electrode (AChE / MXene-PILs / GCE) is placed in a PBS solution of acetylthiocholine iodide (ATCl), a solution containing methyl parathion is added, and differential pulse voltammetry is used for detection.

[0017] The present invention has the following beneficial effects:

[0018] This invention designs and synthesizes an MXene-polymer ionic liquid-based biosensor with enhanced antioxidant properties. By introducing polymer ionic liquid into MXene, the deficiencies of MXene itself are compensated for, while its biosensing performance is enhanced. This is more conducive to enzyme loading. The preparation method is simple, and the resulting material has both excellent conductivity and biocompatibility, which is beneficial for enzyme immobilization and maintaining biological activity.

[0019] The biosensor prepared by this invention exhibits excellent electrochemical activity for the detection of methyl parathion, and can achieve high sensitivity, low detection limit and high selectivity for the detection of methyl parathion concentration. Attached Figure Description

[0020] Figure 1 Here are the scanning electron microscope (SEM) image (A), transmission electron microscope (TEM) image (B), and elemental analysis mapping image (C) of the few-layer MXene.

[0021] Figure 2These are the full spectrum of MXene-PILs (A), the fine spectrum of Ti 2p (B), the fine spectrum of O 1s (C), and the fine spectrum of N 1s (D).

[0022] Figure 3 These are the Ti 2p spectra of MXene (A), MXene (B) after 72 hours of UV irradiation, and MXene-PILs (C) after 72 hours of UV irradiation.

[0023] Figure 4 The diagram shows the zeta potential of MXene (A), PILs (B), and MXene-PILs (C), and the histogram of the zeta potential of the three substances (D).

[0024] Figure 5 The results of MXene / GCE irradiated with ultraviolet light for 72 hours before and after in a 5×10⁻⁶ solution containing 0.1 M KCl. -3 M Fe(CN)6 3- / 4- Cyclic voltammetry curves in solution.

[0025] Figure 6 The results of MXene-PILs / GCE irradiated with ultraviolet light for 72 hours before and after in a 5×10⁻⁶ solution containing 0.1M KCl. -3 MFe(CN)6 3- / 4- Cyclic voltammetry curves in solution.

[0026] Figure 7 The MXene / GCE was tested under different scan rates at a concentration of 0.1 M KCl in a 5 × 10⁻⁶ solution. -3 M Fe(CN)6 3- / 4- Cyclic voltammetry curves in solution (A) and the corresponding linear relationship between the square root of the scan rate and the peak current (B), MXene-PILs / GCE in 5×10⁻⁶ solution containing 0.1 M KCl. -3 M Fe(CN)6 3- / 4- Cyclic voltammetry curves in solution (C) and the corresponding linear relationship between the square root of the scan rate and the peak current (D).

[0027] Figure 8 MXene / GCE after 72 hours of UV irradiation under different scan rates was analyzed in a 5×10⁻⁶ solution containing 0.1 M KCl. -3 M Fe(CN)6 3- / 4- Cyclic voltammetry curves in solution (A) and the corresponding linear relationship between the square root of the scan rate and the peak current (B), MXene-PILs / GCE after 72 hours of UV irradiation in a 5×10⁻⁶ solution containing 0.1 M KCl. -3 MFe(CN)6 3- / 4-Cyclic voltammetry curves in solution (C) and the corresponding linear relationship between the square root of the scan rate and the peak current (D).

[0028] Figure 9 The results are AChE / MXene-PILs / GCE(a), PILs / GCE(b), and AChE / PILs / GCE(c) in 5×10⁻⁶ sodium chloride solution containing 0.1 MKCl. -3 M Fe(CN)6 3- / 4- Cyclic voltammetry curves in solution.

[0029] Figure 10 The following are MXene-PILs / GCE(a), AChE / MXene-PILs / GCE(b), AChE / PILs / GCE(c), and GCE(d) in 5 × 10⁻⁶ solution containing 0.1 M KCl. -3 M Fe(CN)6 3- / 4- AC impedance diagram in solution.

[0030] Figure 11 The cyclic voltammetry curves of AChE / MXene-PILs / GCE (a), AChE / MXene / GCE (b), and MXene-PILs / GCE (c) in 0.1M PBS (pH 7.5) containing 3.0mM ATCl are shown.

[0031] Figure 12 This is a histogram of zeta potentials for MXene-PILs and AChE.

[0032] Figure 13 The cyclic voltammetry curves of (A) AChE / MXene-PILs / GCE in 0.1M PBS (pH 7.5) containing 3.0mM ATCl under different scan rates, and the linear relationship between the corresponding scan rate and peak current (B) are shown.

[0033] Figure 14 The differential pulse voltammetric response (A) and the response current variation curve (B) of the AChE / MXene-PILs / GCE modified electrode after continuous addition of methyl parathion to 0.1M PBS (pH 7.5) containing 3.0mM ATCl are shown.

[0034] Figure 15 This demonstrates the long-term stability of AChE / MXene-PILs / GCE over 28 days.

[0035] Figure 16 The interference of different species on the detection of methyl parathion.

[0036] Figure 17The differential pulse voltammetric response of five AChE / MXene-PILs / GCEs prepared under the same conditions in 0.1M PBS (pH 7.5) containing 3.0 mM ATCl is shown. Detailed Implementation

[0037] To better understand the technical solution of the present invention, specific embodiments are provided for further detailed description, but the solution is not limited thereto.

[0038] This invention utilizes a method of blending MXene with polymeric ionic liquids to prepare MXene-PILs composite materials. Then, acetylcholinesterase, which specifically recognizes organophosphorus pesticides, is introduced and immobilized on the surface of a glassy carbon electrode to construct an MXene-based acetylcholinesterase electrochemical biosensor. Using methyl parathion as a model pesticide, different concentrations of organophosphorus pesticides exhibit varying degrees of inhibition on acetylcholinesterase activity, which can be expressed as differences in electrical signals through a converter, thus achieving the goal of rapid pesticide analysis and detection. Material characterization and electrochemical performance testing were performed using instruments such as X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, atomic force microscopy, and an electrochemical workstation. The results show that the prepared composite material possesses both excellent conductivity and biocompatibility, maintaining the biological activity of the immobilized enzyme while promoting direct electron transfer between the enzyme and the electrode surface. It can be applied in electrochemical analysis, biosensing, and other fields.

[0039] Example 1: Preparation method of MXene-polymer ionic liquid electrochemically modified material (I) is as follows:

[0040] 1. Preparation of polymeric ionic liquids

[0041] Accurately weigh 20 g of 1-vinyl-3-ethylimidazolium bromide monomer and add it to a 250 mL round-bottom flask. Dissolve it in 100 mL of chloroform, then add 0.4 g of azobisisobutyronitrile (AIBN) and stir to dissolve. Replace the air in the flask using the Schlenk technique to place the entire system in a nitrogen atmosphere. Heat to 65 °C and reflux for 5 h. After the reaction is complete, cool to room temperature. Wash the product three times with chloroform and finally freeze-dry for 12 h to obtain a yellow solid, which is the polymeric ionic liquid (PIL).

[0042] 2. Synthesis of MXene-polymeric ionic liquid electrochemically modified materials (MXene-PILs)

[0043] Take 1 mL of 5 mg / mL MXene few-layer colloidal solution in a test tube, add 25 mg of polymeric ionic liquid (PILs), and then sonicate for 30 min. After the solid is completely dispersed and a homogeneous and stable solution is formed, the MXene-PILs composite material is obtained. The obtained composite material is freeze-dried for 12 h to prepare a solid sample, and then a 5 mg / mL MXene-PILs solution is prepared with ultrapure water.

[0044] (II) Characterization of MXene and MXene-PILs

[0045] Figure 1 These are scanning electron microscope (SEM) images (A), transmission electron microscope (TEM) images (B), and elemental analysis mapping images (C) of few-layer MXene. The morphology and composition of the MXene were confirmed by SEM, TEM, and elemental analysis mapping. Figure 1 As shown in (A) and (B) of the figure, it can be clearly seen that MXene consists of very thin monolayer nanosheets, approximately several hundred nanometers wide, without obvious stacking patterns, and with relatively uniform thickness. The average thickness of the original MXene nanosheets is 4.5–5.5 nm. This ultrathin two-dimensional layered structure has a large specific surface area, and its open interlayer spaces are beneficial for shortening the mass transport path. Therefore, in applications such as biosensing, the two-dimensional nanostructure provided by MXene is beneficial for enzymes to maintain their biological activity and for the transport of enzyme substances and products. Figure 1 As shown in (C), the elemental distribution image of MXene shows a uniform distribution of Ti, O, C, and F elements within the selected area, which is typical of Ti3C2T. x Elemental distribution of nanosheets.

[0046] Figure 2 These are the full spectrum (A), fine spectrum (B), fine spectrum (C), and fine spectrum (D) of MXene-PILs. X-ray photoelectron spectroscopy (XPS) confirmed the chemical structures of MXene and PILs, demonstrating the successful preparation of MXene-PILs nanocomposites. Figure 2 As shown in (A), characteristic peaks of Ti, C, O, F, and N can be observed in the full spectrum of MXene-PILs. Figure 2 As shown in (B), the fine spectrum of Ti 2p can be divided into 10 independent component peaks: Ti-C (454.4 eV and 460.0 eV), Ti(II) (455.3 eV and 461.0 eV), Ti(III) (456.3 eV and 462.2 eV), TiO2 (457.4 eV), TiO2 (457.4 eV), TiO2 (457.4 eV), TiO2 (454 ...60. 2-X F X(458.8eV) and Ti-CF x (464.7 eV). For example... Figure 2 As shown in (C), the O 1s fine spectrum can be divided into three independent component peaks: TiO2 (530.0 eV), Ti-CO, and Ti-CO. x (532.0 eV), Ti-C-(OH) x (533.4 eV). Fine spectra of Ti 2p and O1s compared with spectra obtained by MXene in XPS studies. Figure 1 To. Furthermore, Figure 2 The N1s spectrum in (D) can be used to confirm the presence of the polymeric ionic liquid in the composite material. It belongs to the C=N and CN on the imidazole ring of the ionic liquid, with binding energies of 401.3 eV and 401.7 eV, respectively.

[0047] (III) Study on the antioxidant properties of MXene and MXene-PILs

[0048] Figure 3 These are the Ti 2p spectra of MXene (A), MXene (B) after 72 hours of UV irradiation, and MXene-PILs (C) after 72 hours of UV irradiation. Figure 3 As shown in (A) and (B), the Ti2p of the original MXene nanosheets was decomposed into six peaks: Ti-C (454.1 eV and 459.2 eV), Ti(II) (454.7 eV and 460.5 eV), Ti(III) (455.7 eV and 462.2 eV), TiO2 (457.0 eV), and TiO2. 2-X F X (458.3eV) and Ti-CF x (464.2 eV). As can be seen from the figure, after MXene was irradiated with ultraviolet light for 72 hours, the content of Ti(Ⅳ) (including TiO2 and TiO2) decreased. 2-X F X The content of TiO2 increased sharply, rising from 23.31% to 32.20%, while the contents of Ti-C, Ti(II), and Ti(III) decreased significantly. This is because MXene nanosheets are oxidized and transformed into TiO2 and amorphous carbon. Figure 3As shown in Figure (C), after 72 hours of UV irradiation, the total composition of Ti-C, Ti(II), and Ti(III) in MXene-PILs remained almost unchanged compared to the original MXene, while the content of Ti(IV) increased only slightly, from 23.31% to 27.03%. This indicates that the oxidation process of MXene was inhibited by the introduced polymeric ionic liquid, reducing the conversion of low-valent titanium to high-valent titanium. Therefore, it is reasonable to infer that the polymeric ionic liquid provides a unique ability to protect MXene from oxidation, mainly based on the fact that imidazole ionic liquids can act as quenchers to remove harmful ·OH groups.

[0049] It has been reported that MXene has the property of reacting with the generated free radicals, leading to the oxidation of MXene and the degradation of its two-dimensional sheet structure. Figure 4 This shows the Zeta potential diagrams of MXene (A), PILs (B), and MXene-PILs (C), and the Zeta potential histogram (D) for the three substances. Figure 4 As shown, MXene nanosheets possess end groups such as -OH, -O, and -F, exhibiting a negative surface charge and a Zeta potential of -20.3 mV. The polymeric ionic liquid, with its positively charged characteristics, exhibits a Zeta potential of 78.7 mV, demonstrating strong electropositivity. After introducing the polymeric ionic liquid into MXene, the Zeta potential of the composite material is 61.6 mV. This is because the polymeric ionic liquid can be adsorbed onto the surface of the MXene nanosheets through electrostatic interactions, enabling surface charge reversal in the MXene composite material and enhancing the stability of the colloidal solution. This strong interaction constructs a protective layer on the surface of the MXene nanosheets, effectively suppressing the increase of free radicals and frequent surface attacks by ·OH, thereby mitigating the reaction between free radicals and MXene nanosheets. This further explains, from the perspective of electrostatic interactions, the fact that the polymeric ionic liquid can inhibit MXene oxidation.

[0050] Example 2: MXene-polymer ionic liquid-based electrochemically modified electrode (AChE / MXene-PILs / GCE electrode) (I) Preparation method is as follows:

[0051] 1. Preparation of polymeric ionic liquids: Same as in Example 1

[0052] 2. Synthesis of MXene-polymeric ionic liquid electrochemically modified materials (MXene-PILs): Same as in Example 1.

[0053] 3. Preparation of MXene-polymer ionic liquid-based electrochemically modified electrodes

[0054] Pretreatment of Glassy Carbon Electrode (GCE): In this embodiment, a 3 mm diameter glassy carbon electrode (GCE) was used. The GCE was polished with 1.0, 0.3, and 0.05 μm Al₂O₃ solutions, and then ultrasonically cleaned with ultrapure water for 1 min. A three-electrode system was constructed using the glassy carbon electrode as the working electrode, a platinum wire as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Cyclic voltammetry (CV) tests were performed in a 0.1 M KCl solution of 0.5 mM K₃Fe(CN)₆, with a scan range of -200 to 800 mV (vs. Ag / AgCl) and a scan rate of 100 mV / s. When the peak position difference between the oxidation and reduction peaks was less than 70.0 mV, the electrode was considered to have met the activation and cleaning requirements. The glassy carbon electrode was then removed, cleaned with ultrapure water, and dried with high-purity nitrogen (N₂) for later use.

[0055] A modified electrode was prepared from a pretreated glassy carbon electrode (GCE) using a layer-by-layer drop-casting method. 7 μL of a 5 mg / mL MXene-PILs solution was drop-cast onto the pretreated GCE surface and dried at room temperature to obtain MXene-PILs / GCE. Next, 9 μL of a 200 U / mL AChE solution was drop-cast onto the MXene-PILs / GCE surface and dried at 4 °C. After drying, 5 μL of a 0.5 wt% Nafion solution was drop-cast, and the electrode was completely dried at 4 °C to obtain an MXene-polymer ionic liquid-based electrochemically modified electrode, labeled AChE / MXene-PILs / GCE.

[0056] (II) Characterization of Electrodes

[0057] Figure 5 The results of MXene / GCE irradiated with ultraviolet light for 72 hours before and after in a 5×10⁻⁶ solution containing 0.1 M KCl. -3 M Fe(CN)6 3- / 4- Cyclic voltammetry curves in solution. For example... Figure 5 As shown, the cyclic voltammetry curve of the MXene / GCE modified electrode before UV irradiation exhibits a pair of standard redox peaks, with an oxidation peak current of 122.2 μA. UV light accelerates the oxidation process of MXene. After 72 hours of UV irradiation, the peak current of the MXene / GCE modified electrode is 98.7 μA, a decrease of 19.23% compared to before UV irradiation. This is because the MXene nanosheets decompose into amorphous TiO2 and disordered carbon structures after oxidation, causing the collapse of its two-dimensional layered structure and weakening its conductivity.

[0058] As discussed earlier, polymeric ionic liquids can effectively delay the oxidation of MXene, so the conductivity of MXene after incorporation with polymeric ionic liquids was further investigated. Figure 6The results of MXene-PILs / GCE irradiated with UV light for 72 hours before and after in a 5×10⁻⁶ solution containing 0.1 MKCl. -3 M Fe(CN)6 3- / 4- Cyclic voltammetry curves in solution. For example... Figure 6 As shown, the cyclic voltammetry curves of the MXene-PILs / GCE modified electrode before and after UV irradiation are basically identical. Before UV irradiation, the oxidation peak current of MXene-PILs / GCE is 118.6 μA. After 72 hours of UV irradiation, the peak current of MXene-PILs / GCE is 111.8 μA, a decrease of only 5.73%. Therefore, by comparing the attenuation of the oxidation peak current before and after UV irradiation, it can be inferred that the polymeric ionic liquid plays a crucial role in enhancing the long-term antioxidant properties of MXene and maintaining its excellent conductivity. This can meet the requirements of long-term material stability for electrochemical components in practical applications.

[0059] The reaction process on the electrode surface was further investigated by examining the changes in current response at different scan rates. Figure 7 The MXene / GCE was tested under different scan rates at a concentration of 0.1 M KCl in a 5 × 10⁻⁶ solution. -3 M Fe(CN)6 3- / 4- Cyclic voltammetry curves in solution (A) and the corresponding linear relationship between the square root of the scan rate and the peak current (B), MXene-PILs / GCE in 5×10⁻⁶ solutions containing 0.1 MKCl. -3 M Fe(CN)6 3- / 4- The cyclic voltammetry curve in the solution (C) and the corresponding linear relationship between the square root of the scan rate and the peak current (D). Figure 7 As shown in (A) and (C), when the scan rate increases within the range of 20 mV / s to 200 mV / s, the oxidation peak current increases, and the oxidation peak shifts towards the positive potential. Figure 7 As shown in (B) and (D), the oxidation peak current is proportional to the square root of the scan rate, indicating that the oxidation reaction on the surface of the MXene / GCE and MXene-PILs / GCE modified electrodes before UV irradiation is a diffusion-controlled process.

[0060] Figure 8 MXene / GCE after 72 hours of UV irradiation under different scan rates was analyzed in a 5×10⁻⁶ solution containing 0.1 M KCl. -3 M Fe(CN)6 3- / 4- Cyclic voltammetry curves in solution (A) and the corresponding linear relationship between the square root of the scan rate and the peak current (B), MXene-PILs / GCE after 72 hours of UV irradiation in a 5×10⁻⁶ solution containing 0.1 M KCl. -3 MFe(CN)63- / 4- The cyclic voltammetry curve in the solution (C) and the corresponding linear relationship between the square root of the scan rate and the peak current (D). Figure 8 As shown in (A) and (C), when the scan rate increases within the range of 20 mV / s to 200 mV / s, the oxidation peak current increases, and the oxidation peak shifts towards the positive potential. Figure 8 As shown in (B) and (D), the oxidation peak current is proportional to the square root of the scan rate, which indicates that the oxidation reaction on the surface of the MXene / GCE and MXene-PILs / GCE modified electrodes after UV irradiation is a diffusion-controlled process.

[0061] (III) Characterization of the electrochemical performance of the AChE / MXene-PILs / GCE electrode

[0062] Electrochemical characterization was performed in 0.1M PBS buffer solution (pH 7.5) at a scan rate of 100 mV / s. A three-electrode system was used: an Ag / AgCl electrode as the reference electrode, a platinum electrode as the auxiliary electrode, and an AChE / MXene-PILs / GCE modified electrode as the working electrode. Under the same experimental conditions, the AChE / MXene-PILs / GCE modified electrode was continuously scanned 50 times before each test to assess the stability and applicability of the electrode material.

[0063] The fabrication process of the biosensor was studied by analyzing the peak current changes in cyclic voltammetry curves. Figure 9 The samples are AChE / MXene-PILs / GCE (a), PILs / GCE (b), and AChE / PILs / GCE (c) in 5 × 10⁻⁶ solution containing 0.1 M KCl. -3 MFe(CN)6 3- / 4- Cyclic voltammetry curves in solution. For example... Figure 9 As shown, a pair of redox peaks can be observed on PILs / GCE. Compared with PILs / GCE, the redox peak current of AChE / PILs / GCE is significantly reduced. This is mainly because AChE, being a biomacromolecule, has poor conductivity after being immobilized on the electrode surface, hindering electron transfer at the electrode surface and leading to a decrease in the conductivity of the modified electrode, thus reducing the redox peak current. However, this also indicates that AChE was successfully immobilized on the electrode surface. Compared with AChE / PILs / GCE, the redox peak current of AChE / MXene-PILs / GCE is significantly increased. This enhanced cyclic voltammetric response is mainly attributed to the large surface area and excellent metallic conductivity of MXene, which enhances the conductivity of the substrate.

[0064] The magnitude of the interfacial electron transfer resistance of the modified electrode can, to some extent, determine the conductivity of the modified material. Figure 10The following are MXene-PILs / GCE(a), AChE / MXene-PILs / GCE(b), AChE / PILs / GCE(c), and GCE(d) in 5 × 10⁻⁶ solution containing 0.1 M KCl. -3 M Fe(CN)6 3- / 4- AC impedance diagram in solution. For example... Figure 10 As shown, the electron transfer resistance of MXene-PILs / GCE is 97.8 Ω. After further loading AChE onto the MXene-PILs surface, the resistance of AChE / MXene-PILs / GCE is 218.0 Ω, a significant increase, demonstrating successful enzyme immobilization and the successful fabrication of the biosensor. Notably, the resistance of AChE / PILs / GCE is 508.3 Ω. At the same enzyme dosage, the resistance of the enzyme electrode with added MXene is significantly lower than that of AChE / PILs / GCE. This is because MXene possesses excellent metallic conductivity and a large specific surface area, accelerating electron transfer on the electrode surface. The results of the AC impedance spectroscopy comparison are consistent with those obtained from cyclic voltammetry.

[0065] Figure 11 These are the cyclic voltammetry curves of AChE / MXene-PILs / GCE (a), AChE / MXene / GCE (b), and MXene-PILs / GCE (c) in 0.1M PBS (pH 7.5) containing 3.0 mM ATCl. Figure 11 As shown, both AChE / MXene / GCE and AChE / MXene-PILs / GCE modified electrodes exhibited an irreversible oxidation peak after the addition of the substrate ATCl, while the modified electrode MXene-PILs / GCE without AChE did not produce an oxidation peak. This is because AChE catalyzes the substrate ATCl to generate the hydrolysis product thiocholine, which oxidizes on the electrode surface, producing an oxidation peak. The figure shows that the oxidation peak current of AChE / MXene-PILs / GCE is significantly higher than that of AChE / MXene / GCE, indicating that introducing polymeric ionic liquids into MXene effectively enhances the electrocatalytic performance of the enzyme biosensor. This is because after MXene is blended with polymeric ionic liquids, the positively charged polymeric ionic liquids can alter the negatively charged surface charge of MXene, allowing the MXene-PILs composite material to immobilize the electronegative acetylcholinesterase on the electrode surface through electrostatic attraction (e.g., ...). Figure 12 As shown in the figure, this method enables the electrostatic assembly of enzymes on the surface of a glassy carbon electrode. Electrostatic attraction shortens the distance between the enzyme and the electrode surface, accelerating electron transfer. Simultaneously, the polymeric ionic liquid itself is biocompatible, creating a favorable microenvironment for the enzyme and helping to maintain its natural activity.

[0066] Figure 13 The figures show (A) cyclic voltammetry curves of AChE / MXene-PILs / GCE in 0.1M PBS (pH 7.5) containing 3.0 mM ATCl under different scan rates, and (B) the corresponding linear relationship between scan rate and peak current. Figure 13 As shown in (A), when the scan rate increases within the range of 20 mV / s to 200 mV / s, the oxidation peak current increases, and the oxidation peak shifts towards the positive potential. Figure 13 As shown in (B), the peak current is proportional to the square root of the scan rate, which indicates that the oxidation reaction on the electrode is a diffusion-controlled process.

[0067] Example 3: Application of MXene-polymer ionic liquid-based electrochemically modified electrode in electrochemical qualitative and quantitative detection of pesticides (I) Characterization of the electrocatalytic performance of AChE / MXene-PILs / GCE electrode

[0068] Based on the optimized parameters mentioned above, the relationship between pesticide concentration and inhibition rate was studied using methyl parathion as a model pesticide. The prepared AChE / MXene-PILs / GCE was placed in 0.1M PBS (pH 7.5) with a concentration of 3.0 mM ATCl, and different concentrations of methyl parathion (5.0 × 10⁻⁶) were added. -4 10 -3 5.0×10 -3 10 -2 5.0×10 -2 10 -1 The solutions were incubated at 1.0 and 10.0 ng / mL for 15 min. Then, differential pulse voltammetry (DPV) was used for detection.

[0069] Figure 14 The differential pulse voltammetric response (A) and the response current versus methyl parathion concentration curve (B) of the AChE / MXene-PILs / GCE modified electrode after continuous addition of methyl parathion to 0.1M PBS (pH 7.5) containing 3.0 mM ATCl are shown. Figure 14 As shown in Figure (A), the DPV response of the prepared AChE / MXene-PILs / GCE gradually decreases with increasing methyl parathion concentration. This is because organophosphorus pesticides inhibit the activity of AChE, and the higher the concentration, the stronger the inhibitory effect, leading to a continuous decrease in the response current. The standard curve of inhibition rate versus methyl parathion concentration is shown in Figure (A). Figure 14 As shown in (B), the linear equation for the biosensor is inhibition (%) = 14.44 log C + 60.86 (R). 2 =0.9964), the linear range is 5.0×10-4 ~10.0 ng / mL, detection limit is 2.0 × 10⁻⁶ -4 ng / mL (3σ rule).

[0070] (II) Study on the stability, repeatability and anti-interference performance of AChE / MXene-PILs / GCE electrode

[0071] Long-term stability is an important parameter for evaluating the performance of AChE biosensors.

[0072] Figure 15 This refers to the long-term stability of AChE / MXene-PILs / GCE over 28 days. (For example...) Figure 15 As shown, AChE / MXene-PILs / GCE was stored at 4°C, and its response current change was monitored over 28 days to evaluate the stability of the biosensor. The monitoring showed that the final current retention rate was 93%, indicating that the prepared AChE / MXene-PILs / GCE has excellent long-term stability.

[0073] Figure 16 It is AChE / MXene-PILs / GCE interfering with 3mM glucose, 3mM citrate, and 3mM PO4. 3- 3mMNO3 - 3mM K + 3mM Cu 2+ 3mM Mg 2+ 1ng mL -1 Residual activity in the presence of methyl parathion. These interfering substances were chosen because they are commonly found in fruits, vegetables, and water samples, which are potential matrices for detecting organophosphorus pesticides. The evaluation process involved observing changes in the current response of AChE / MXene-PILs / GCE by simultaneously adding ATCl and other interfering substances. Figure 16 It can be seen from the presence of glucose, citric acid, and PO4. 3- NO3 - K + Cu 2+ In its presence, it causes minimal interference to the current response of AChE / MXene-PILs / GCE. The decrease in current response is also significant when detecting a certain concentration of methyl parathion, indicating that the constructed AChE / MXene-PILs / GCE exhibits good anti-interference performance in pesticide detection. However, in the presence of Mg... 2+ When present, it significantly interferes with the sensor's current response, indicating that the presence of Mg in the actual sample... 2+ When present, it can interfere with the sensor's detection of organophosphorus pesticides.

[0074] Figure 17 The differential pulse voltammetric responses of five AChE / MXene-PILs / GCE molecules prepared under the same conditions in 0.1M PBS (pH 7.5) containing 3.0 mM ATCl are shown. Figure 17 As shown, the reproducibility of the prepared sensors was evaluated using differential pulse voltammetry in 0.1 M PBS (pH 7.5) containing 3.0 mM ATCl for five independently prepared AChE / MXene-PILs / GCE modified electrodes. The relative standard deviation (RSD) of ATCl detection was 4.3%, indicating that the constructed AChE / MXene-PILs / GCE exhibits excellent reproducibility.

Claims

1. An MXene-polymer ionic liquid-based electrochemically modified electrode, characterized in that, The preparation method of MXene-PILs, an electrochemically modified material based on MXene-polymer ionic liquid, includes the following steps: First, MXene-PILs solution is drop-coated onto the surface of a pretreated glassy carbon electrode (GCE) using a layer-by-layer drop-addition method and dried at room temperature. Then, acetylcholinesterase (AChE) solution is drop-coated onto the MXene-PILs surface and dried at 2–6 °C. After drying, Nafion solution is drop-coated and dried at 2–6 °C to obtain the MXene-polymer ionic liquid-based electrochemically modified electrode AChE / MXene-PILs / GCE. The preparation method of the MXene-polymer ionic liquid electrochemically modified material MXene-PILs includes the following steps: 1) Dissolve 1-vinyl-3-ethylimidazolium bromide monomer in chloroform, add azobisisobutyronitrile (AIBN), stir to dissolve, heat to 60-70 °C in N2 atmosphere, reflux for 5-6 h, after the reaction is completed, cool to room temperature, wash the product with chloroform, and dry in a freeze dryer to obtain polymeric ionic liquids (PILs). 2) Mix the MXene colloidal solution with the polymeric ionic liquid PILs and sonicate for 30-40 min to form a homogeneous and stable solution. Then freeze-dry the resulting mixed solution to obtain MXene-PILs.

2. The MXene-polymer ionic liquid-based electrochemically modified electrode according to claim 1, characterized in that, In step 2), the concentration of the MXene colloidal solution is 2-8 mg / mL, and the ratio of MXene colloidal solution to polymeric ionic liquid is 1 mL: 20-30 mg.

3. The MXene-polymer ionic liquid-based electrochemically modified electrode according to claim 1, characterized in that, The concentration of MXene-PILs solution was 2–8 mg / mL, the concentration of acetylcholinesterase (AChE) solution was 150–250 U / mL, and the concentration of Nafion solution was 0.2–0.8 wt%. The volume ratio of MXene-PILs solution:acetylcholinesterase (AChE) solution:Nafion solution was 7:9:

5.

4. The MXene-polymer ionic liquid-based electrochemically modified electrode according to claim 3, characterized in that, The pH value of the acetylcholinesterase (AChE) solution is 7-8.

5. The application of the MXene-polymer ionic liquid-based electrochemically modified electrode as described in claim 1, 3 or 4 as a biosensor in the electrochemical qualitative and quantitative detection of pesticides.

6. The application according to claim 5, characterized in that, The pesticide in question is an organophosphorus pesticide.

7. The application according to claim 6, characterized in that, The organophosphorus pesticide in question is methyl parathion.

8. The application according to claim 7, characterized in that, The method is as follows: The MXene-polymer ionic liquid-based electrochemically modified electrode AChE / MXene-PILs / GCE was placed in a PBS solution of acetylthiocholine iodide, and a solution containing methyl parathion was added. Differential pulse voltammetry was used for detection.

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