G-mxene-paa-fe3+ hydrogel and preparation method and application thereof

Abstract

This invention belongs to the field of biosensing technology, specifically relating to a G-MXene-PAA-Fe 3+ Hydrogels, their preparation methods, and applications. This invention modifies MXene with antioxidants to prepare modified G-MXene; then, using acrylic acid (AA) free radical polymerization chemical crosslinking as the first network, polyacrylic acid (PAA)-Fe... 3+ Metal ions are complexed into a second network, and modified G-MXene is used as a crosslinking agent and conductive nanofiller. G-MXene-PAA-Fe is prepared using a simple and easy-to-operate one-pot method with ammonium persulfate as the initiator. 3+ Self-healing conductive hydrogel. The self-healing conductive hydrogel prepared by this invention has excellent stability, self-healing properties, mechanical properties, conductivity, and sensing properties, and has broad application prospects in the field of flexible sensors.

Description

Technical Field

[0001] This invention belongs to the field of biosensing technology, specifically relating to a G-MXene-PAA-Fe 3+ Hydrogels, their preparation methods, and applications. Background Technology

[0002] Hydrogels are flexible and resilient polymers with a 3D network structure, containing a large number of hydrophilic groups. They can absorb tens or even hundreds of times more water or liquid than themselves and can swell even when insoluble in water, thus exhibiting excellent water retention capabilities. As a special type of hydrogel, smart hydrogels integrate sensing, actuation, and information processing, possessing intelligent characteristics and showing broad application prospects in traditional biomedical and sensing fields. However, traditional hydrogels still suffer from drawbacks such as poor self-healing properties, low electrical conductivity, poor mechanical properties, poor biocompatibility, and slow and singular response to external stimuli, limiting their further application in the sensing field. Therefore, it is necessary to further improve the performance of hydrogels and expand their application in flexible sensors.

[0003] Studies have shown that introducing functional nanomaterials into hydrogel networks can improve their conductivity, mechanical properties, and biocompatibility, and bring new functional responses, thus breaking the limitations of traditional hydrogel technology. Among all two-dimensional nanomaterials, MXene is a class of transition metal carbide / nitride two-dimensional nanomaterials with a graphene-like structure. Its chemical formula is M... n+1 X n T X (n = 1-4), where M represents the pre-transition metal (Ti, V, Nb, etc.), X represents C or N, and T represents the transition metal. X Different surface terminal groups (-OH, -O, -F, etc.) represent different MXenes. Due to their excellent conductivity, hydrophilicity, processability, specific surface area, and mechanical strength, MXenes are widely used in electrochemical energy storage and conversion, electromagnetic interference shielding, sensing, and biomedicine. For example, inspired by the ordered structure of muscle, a research team at Jilin University prepared anisotropic MXene conductive hydrogels using a directional freezing method. Due to the anisotropy of the MXene conductive hydrogel, its mechanical properties and conductivity are enhanced in specific directions. Through solvent displacement, the hydrogel exhibits a wide temperature range of -36℃ to 25℃. This MXene conductive hydrogel can be used as a wearable flexible sensor and a 3D sensing array. However, when MXene is exposed to air or water, it rapidly oxidizes and degrades within days, leading to the decomposition of its layered, two-dimensional structure, forming titanium dioxide (TiO2) and carbon (C). The oxidative stability and surface weight accumulation problems of MXene severely hinder its application in practical industry.

[0004] Furthermore, due to the inherently low Young's modulus of hydrogels, coupled with the complex load-bearing and dynamic environment within the human body, hydrogel bioelectronic devices are easily damaged during use. To extend their durability, reliability, and lifespan, endowing hydrogels with self-healing properties is a better choice. However, preparing hydrogels with excellent self-healing, conductivity, mechanical properties, and sensing properties presents numerous challenges in raw material selection, preparation processes, and practical applications. Summary of the Invention

[0005] In view of this, the present invention proposes a self-healing conductive hydrogel applicable to wearable flexible sensors, its preparation method, and its application. Based on the novel transition metal carbide / nitride MXene, the present invention introduces antioxidant-modified MXene into an acrylic acid radical polymerization and metal coordination bond hydrogel system, and prepares MXene-PAA-Fe through a simple one-pot method. 3+ This self-healing conductive hydrogel possesses excellent stability, self-healing properties, mechanical properties, electrical conductivity, and sensing properties, making it suitable for use in the field of flexible sensors.

[0006] One of the objectives of this invention is to provide a method for preparing G-MXene-PAA-Fe 3+ A composition of self-healing conductive hydrogels.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] Used in the preparation of G-MXene-PAA-Fe 3+ A composition of a self-healing conductive hydrogel, the composition comprising the following components: modified G-MXene, acrylic acid, and FeCl3; wherein the volume ratio of the modified G-MXene to the acrylic acid is 170-180:230-270; and the volume of the FeCl3 is 2-4 mol% of the acrylic acid monomer.

[0009] Preferably, the volume ratio of the modified G-MXene to the acrylic acid is 175:250.

[0010] Furthermore, MXene is modified with an antioxidant to obtain the modified G-MXene; the volume ratio of MXene to the antioxidant is 1:5 to 10; the antioxidant is L-ascorbic acid.

[0011] Considering the susceptibility of MXene to oxidation, this invention employs L-ascorbic acid (VC) for antioxidant modification, yielding G-MXene. Antioxidant treatment significantly alters the surface chemistry of MXene, removing a large number of F groups from its surface; in the presence of the antioxidant, Ti… + To Ti2+ / Ti 3+ The chemical state transition of Ti is suppressed; 4+ The growth rate is slow over time. Compared with unmodified MXene nanosheets, the conductivity of modified G-MXene is not significantly reduced, and its morphology still maintains a certain degree of stability after 22 days.

[0012] Furthermore, the composition also contains an initiator; the volume ratio of the acrylic acid to the initiator is 4 to 6:1; the initiator is ammonium persulfate.

[0013] Preferably, the volume ratio of the acrylic acid to the initiator is 5:1.

[0014] The second objective of this invention is to provide a method for preparing G-MXene-PAA-Fe based on the aforementioned composition. 3+ The present invention employs a simple one-pot method to prepare self-healing conductive hydrogels in a single container.

[0015] To achieve the above objectives, the present invention adopts the following technical solution:

[0016] G-MXene-PAA-Fe was prepared based on the aforementioned composition. 3+ The method for producing self-healing conductive hydrogels includes the following steps:

[0017] S1: Under the action of ultrasound, deionized water, modified G-MXene, acrylic monomer and ammonium persulfate solution are added in sequence and uniformly dispersed to obtain G-MXene-PAA hydrogel; the volume ratio of the deionized water, the modified G-MXene, the acrylic monomer and the ammonium persulfate solution is 500:170~180:230-270:50;

[0018] S2: The G-MXene-PAA hydrogel obtained in S1 was immersed in FeCl3 solution to obtain G-MXene-PAA-Fe 3+ Self-healing conductive hydrogel.

[0019] Furthermore, in S1, the volume ratio of the deionized water, the modified G-MXene, the acrylic monomer, and the ammonium persulfate solution is 10:3.5:5:1.

[0020] Furthermore, in S1, the concentration of the modified G-MXene is 10 mg / mL; and the concentration of the ammonium persulfate solution is 50 mg / mL.

[0021] Furthermore, in S2, the amount of the FeCl3 solution is 2-4 mol% of the acrylic acid monomer, preferably 3 mol%.

[0022] Furthermore, in S2, the concentration of the FeCl3 solution is 15 mg / mL.

[0023] Furthermore, in S2, the soaking time is 25-60 minutes, preferably 30 minutes.

[0024] Furthermore, the preparation method of the modified G-MXene is as follows:

[0025] (1) Add Ti3AlC2 to LiF / HCl etching solution and synthesize MXene by selective etching;

[0026] (2) The MXene obtained in step (1) is modified with an antioxidant to obtain the modified G-MXene.

[0027] Furthermore, the MXene obtained in step (1) is a two-dimensional single-layer sheet structure with a thickness of approximately 3.0-3.5 nm and a lateral dimension of approximately 1.3-1.7 μm.

[0028] Furthermore, the LiF / HCl etching solution is prepared as follows: LiF is dissolved in 9M HCl solution at room temperature and magnetically stirred for 20 minutes to obtain the etching solution; the ratio of LiF to the 9M HCl solution is 1g:20mL.

[0029] Furthermore, step (1) specifically involves:

[0030] Ti3AlC2 was slowly added to the etching solution, stirred at 35°C for 24 hours, centrifuged at 3500 rpm for 5 minutes, and the supernatant was discarded. The supernatant was then washed repeatedly by centrifugation with 1M hydrochloric acid and deionized water until the pH of the supernatant was greater than 5. After discarding the supernatant, water was added again, and the solution was sonicated in an ice bath under nitrogen for 1 hour and centrifuged for 1 hour to collect the supernatant, thus preparing a monolayer MXene suspension.

[0031] Furthermore, the reaction conditions in step (2) include: sonication for 4-10 min and oscillation reaction for 4-10 h; preferably, sonication for 5 min and oscillation reaction for 5 h.

[0032] Furthermore, in step (2), the volume ratio of MXene to the antioxidant is 1:5 to 10, preferably 1:7; the antioxidant is L-ascorbic acid.

[0033] Furthermore, in step (2), the reaction conditions are sonication for 4-6 minutes and shaking on a shaker for 4-8 hours, with the most preferred conditions being sonication for 5 minutes and shaking on a shaker for 5 hours.

[0034] In this invention, G-MXene-PAA-Fe 3+The principle of the self-healing conductive hydrogel is as follows: First, L-ascorbic acid is used as an antioxidant to modify MXene nanosheets, preparing long-term stable modified G-MXene nanosheets. Next, in the presence of the modified G-MXene nanosheets (as a crosslinking agent and conductive nanofiller) and the initiator ammonium persulfate, G-MXene-PAA hydrogel is formed through in-situ free radical polymerization of acrylic acid monomers. Finally, Fe... 3+ Using G-MXene nanosheets as coordination centers, G-MXene-PAA-Fe is formed by coordinating and crosslinking the polarization groups on the modified G-MXene nanosheets with the carboxyl groups in the PAA chain. 3+ Hydrogel.

[0035] The third objective of this invention is to provide a G-MXene-PAA-Fe prepared by the aforementioned method. 3+ Self-healing conductive hydrogel.

[0036] To achieve the above objectives, the present invention adopts the following technical solution:

[0037] G-MXene-PAA-Fe prepared by the aforementioned method 3+ Self-healing conductive hydrogel.

[0038] Furthermore, in the self-healing conductive hydrogel, acrylic acid free radical polymerization chemical crosslinking forms the first network, polyacrylic acid (PAA)-Fe 3+ Metal ions complex to form a second network.

[0039] Furthermore, the G-MXene-PAA-Fe 3+ The self-healing conductive hydrogel has a self-healing time of 15 minutes to 12 hours and a self-healing rate of 92% to 98%.

[0040] The fourth objective of this invention is to provide the aforementioned composition and / or the aforementioned G-MXene-PAA-Fe 3+ Application of self-healing conductive hydrogels in the fabrication of wearable flexible sensors.

[0041] The beneficial effects of this invention are as follows:

[0042] 1. This invention uses L-ascorbic acid as an antioxidant to modify MXene nanosheets, preparing long-term stable MXene nanosheets (G-MXene nanosheets). G-MXene exhibits 3.5 times higher electrical conductivity and better oxidative stability than MXene. These G-MXene nanosheets can play multiple roles during the gelation process. Their synergistic effect with other elements in the hydrogel network leads to better hydrogel stability, showing promising application prospects in hydrogel flexible sensors.

[0043] 2. This invention utilizes ammonium persulfate as an initiator, acrylic acid monomer, FeCl3, and modified G-MXene nanosheets to prepare MXene-PAA-Fe via a simple one-pot method. 3+ Self-healing conductive hydrogel. MXene nanosheets, as a multifunctional crosslinking agent, work together with the initiator ammonium persulfate to effectively promote the free radical polymerization of AA monomers within 10 minutes. While imparting conductivity to the hydrogel, it also avoids the disadvantages of traditional AA monomer free radical polymerization, such as high temperature and long time.

[0044] 3. This invention relates to PAA-Fe 3+ The introduction of G-MXene nanosheets into the system effectively improves its mechanical and electrical conductivity properties. G-MXene-PAA-Fe 3+ The hydrogel exhibits a tensile strength of up to 1443.8 kPa, an elongation at break of up to 926.7%, and an electrical conductivity as high as 2.8 S·m. -1 When the modified G-MXene:AA:APS:H2O ratio is 3.5:5:1:10 (i.e., the amount of modified G-MXene in the reaction system is 175 μL, the amount of acrylic acid monomer is 250 μL, the amount of ammonium persulfate solution is 50 μL, and the amount of water is 500 μL), the G-MXene-PAA-Fe prepared by this invention... 3+ The self-healing conductive hydrogel has the best overall performance.

[0045] 4. The G-MXene-PAA-Fe of the present invention 3+ The self-healing conductive hydrogel has excellent self-healing properties, with a self-healing rate of 94.2%.

[0046] 5. The G-MXene-PAA-Fe of the present invention 3+ When used in sensor applications, self-healing conductive hydrogels can effectively reflect real-time relative resistance changes under different actions, showing promising application prospects as wearable smart strain sensors with a strain sensitivity of up to 3.68.

[0047] 6. This invention further explores G-MXene-PAA-Fe 3+ The effects of hydrogel preparation conditions on various properties (conductivity, mechanical properties, self-healing, etc.), and the final prepared G-MXene-PAA-Fe 3+ Hydrogels possess excellent self-healing properties, electrical conductivity, mechanical properties, sensing properties, biocompatibility, and oxidative stability, making them promising candidates for applications in the sensing field. Furthermore, this invention provides a reference for the fabrication of MXene-based conductive hydrogels in flexible sensors. Attached Figure Description

[0048] Figure 1 A schematic diagram illustrating the synthesis of MXene nanosheets;

[0049] Figure 2 For MXene-PAA and MXene-PAA-Fe 3+ Schematic diagram of the hydrogel preparation process;

[0050] Figure 3 The image shows the results of light visual observation of MXene and G-MXene dispersions at a concentration of 1.25 mg / mL. Figure 3 -A is a graph of MXene and G-MXene dispersions at a concentration of 1.25 mg / mL at day 0; Figure 3 -B is a graph of MXene and G-MXene dispersions at a concentration of 1.25 mg / mL after 3 days; Figure 3 -C is a graph of MXene and G-MXene dispersions at a concentration of 1.25 mg / mL after 5 days; Figure 3 -D is a graph of MXene and G-MXene dispersions at a concentration of 1.25 mg / mL after 8 days; Figure 3 -E is a graph of MXene and G-MXene dispersions at a concentration of 1.25 mg / mL 14 days after shaking; Figure 3 -F is a graph showing the concentration of MXene and G-MXene dispersions at 1.25 mg / mL 14 days after shaking under sunlight; Figure 3 -G is a graph of MXene and G-MXene dispersions at a concentration of 1.25 mg / mL at 22 days; Figure 3 -H is a graph of MXene and G-MXene dispersions at a concentration of 1.25 mg / mL 22 days after shaking;

[0051] Figure 4 The image shows the results of light visual observation of MXene and G-MXene dispersions at a concentration of 0.5 mg / mL. Figure 4 -A is a graph of MXene and G-MXene dispersions at a concentration of 0.5 mg / mL on day 0; Figure 4 -B is a graph of MXene and G-MXene dispersions at a concentration of 0.5 mg / mL after 3 days; Figure 4 -C is a graph of MXene and G-MXene dispersions at a concentration of 0.5 mg / mL after 5 days; Figure 4 -D is a graph of MXene and G-MXene dispersions at a concentration of 0.5 mg / mL after 8 days; Figure 4 -E is a graph of MXene and G-MXene dispersions at a concentration of 0.5 mg / mL 14 days after shaking; Figure 4-F is a graph showing the concentration of MXene and G-MXene dispersions at 0.5 mg / mL after 14 days of shaking under sunlight; Figure 4 -G is a graph of MXene and G-MXene dispersions at a concentration of 0.5 mg / mL at 22 days; Figure 4 -H is a graph of MXene and G-MXene dispersions at a concentration of 0.5 mg / mL 22 days after shaking;

[0052] Figure 5 XPS spectra and high-resolution spectra of Ti2p for MAX, MXene, and G-MXene; among them, Figure 5 -A shows the XPS spectra of MAX, MXene, and G-MXene; Figure 5 -B represents the high-resolution Ti2p spectra of MAX, MXene, and G-MXene;

[0053] Figure 6 The image shows the gelation process of a mixed solution of AA, APS, and deionized water, and the MXene-PAA hydrogel over 10 minutes. Figure 6 -A and B represent the initial states of a mixed solution of AA, APS, and deionized water; Figure 6 -C and D represent the states of the mixed solution of AA, APS, and deionized water after 10 minutes of mixing; Figure 6 -E and F represent the initial states of the mixed solution of AA, APS, and MXene; Figure 6 -G and H represent the state of the mixed solution of AA, APS, and MXene after 10 minutes of mixing;

[0054] Figure 7 G-MXene-PAA-Fe 3+ Schematic diagram of hydrogel compression and rebound;

[0055] Figure 8 For different proportions of MXene-PAA hydrogel and MXene-PAA-Fe 3+ Stress-strain curves of hydrogels; among which, Figure 8 -A represents the stress-strain curves of MXene-PAA hydrogels with different proportions; Figure 8 -B represents different proportions of MXene-PAA-Fe. 3+ Stress-strain curve of hydrogel;

[0056] Figure 9 For different proportions of G-MXene-PAA-Fe 3+ Stress-strain curves of hydrogels and elastic modulus diagrams of three types of hydrogels; among them, Figure 9 -A represents different proportions of G-MXene-PAA-Fe. 3+Stress-strain curve of hydrogel; Figure 9 -B represents MXene-PAA hydrogel, MXene-PAA-Fe 3+ Hydrogel and G-MXene-PAA-Fe 3+ Elastic modulus diagram of hydrogel;

[0057] Figure 10 G-MXene-PAA-Fe with different MXene contents 3+ Stress-strain curves and elastic modulus diagrams of hydrogels; among them, Figure 10 -A represents G-MXene-PAA-Fe with different MXene contents. 3+ Stress-strain curve of hydrogel; Figure 10 -B represents G-MXene-PAA-Fe with different MXene contents. 3+ Elastic modulus diagram of hydrogel;

[0058] Figure 11 For different proportions of G-MXene-PAA-Fe 3+ Stress-strain curves and toughness diagrams of hydrogels; among which, Figure 11 -A represents different proportions of G-MXene-PAA-Fe. 3+ Stress-strain curve of hydrogel; Figure 11 -B represents different proportions of G-MXene-PAA-Fe. 3+ Toughness diagram of hydrogel;

[0059] Figure 12 G-MXene-PAA-Fe with different MXene contents 3+ Stress-strain curves and toughness diagrams of hydrogels; among which, Figure 12 -A represents G-MXene-PAA-Fe with different MXene contents. 3+ Stress-strain curve of hydrogel; Figure 12 -B represents G-MXene-PAA-Fe with different MXene contents. 3+ Toughness diagram of hydrogel;

[0060] Figure 13 G-MXene-PAA-Fe 3+ A schematic diagram of the self-healing properties of hydrogels;

[0061] Figure 14 G-MXene-PAA-Fe 3+ Hydrogel circuit connection diagram;

[0062] Figure 15 G-MXene-PAA-Fe with different MXene contents 3+ Statistical graph of the electrical conductivity of hydrogels;

[0063] Figure 16 For MXene-PAA-Fe 3+ Hydrogel and G-MXene-PAA-Fe 3+ A graph showing the change in electrical resistance of a hydrogel over 14 days;

[0064] Figure 17 G-MXene-PAA-Fe 3+ The sensitivity test results for the hydrogel are shown in the figure; among them, Figure 17 -A represents G-MXene-PAA-Fe 3+ A schematic diagram of the hydrogel before stretching; Figure 17 -B represents G-MXene-PAA-Fe 3+ A schematic diagram of hydrogel stretching; Figure 17 -C represents G-MXene-PAA-Fe 3+ A schematic diagram of the hydrogel after stretching; Figure 17 -D represents G-MXene-PAA-Fe 3+ A linear plot of the fitted ΔR / R-ε of the hydrogel;

[0065] Figure 18 G-MXene-PAA-Fe for finger bending 0-90° 3+ A graph showing the relative change in electrical resistance of the hydrogel sample;

[0066] Figure 19 G-MXene-PAA-Fe for bending fingers and wrists at a certain angle 3+ A graph showing the real-time relative resistance change of the hydrogel; where, Figure 19 -A represents repeated bending of the finger at a certain angle. G-MXene-PAA-Fe 3+ A graph showing the real-time relative resistance change of the hydrogel; Figure 19 -B represents repeated wrist flexion at a certain angle. (G-MXene-PAA-Fe) 3+ A graph showing the real-time relative resistance change of the hydrogel. Detailed Implementation

[0067] The technical solution of the present invention will be described more clearly and completely below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0068] The main experimental reagents involved in this invention are shown in Table 1.

[0069] Table 1. Experimental Reagents Browser

[0070] Serial Number name Specification relative molecular mass 1 Acrylic acid (AA) 500mL / bottle 72.063 2 <![CDATA[Ti3AlC2 MAX phase]]> 10g / bag 194.6 3 <![CDATA[Iron(III) chloride hexahydrate (FeCl3·6H2O)]]> 500g / bottle 270.21 4 L-Ascorbic Acid (VC) 100g / bottle 176.12 5 Ammonium persulfate (APS) 100g / bottle 228.20 6 Lithium fluoride (LiF) 100g / bottle 25.94 7 Hydrochloric acid (HCl) 500mL / bottle 36.46

[0071] Table 2. List of Experimental Apparatus and Instruments

[0072]

[0073]

[0074] In this embodiment of the invention, some reagent preparation methods are as follows:

[0075] 1) Preparation of 9M HCl: At room temperature, measure 15mL of concentrated hydrochloric acid (12M HCl) and slowly pour 5mL of deionized water along a glass rod. Stir with a magnetic stirrer until the solution is mixed evenly.

[0076] 2) Preparation of 1M HCl: At room temperature, measure 5 mL of concentrated hydrochloric acid (12M HCl) and slowly pour it into 55 mL of deionized water along a glass rod. Stir with a magnetic stirrer until the solution is mixed evenly.

[0077] 3) Preparation of L-ascorbic acid solution: Dissolve 2g of L-ascorbic acid in 20mL of deionized water and stir with a magnetic stirrer until the solution is mixed evenly to obtain an L-ascorbic acid solution with a concentration of 100mg / mL.

[0078] 4) Preparation of ammonium persulfate solution: Dissolve 0.25g of ammonium persulfate powder in 5mL of deionized water and stir with a magnetic stirrer until the solution is mixed evenly to obtain an APS solution with a concentration of 50mg / mL.

[0079] 5) Preparation of ferric chloride solution: Dissolve 0.15g of ferric chloride hexahydrate in 10mL of deionized water and stir with a magnetic stirrer until the solution is mixed evenly to obtain a FeCl3 solution with a concentration of 15mg / mL.

[0080] In this embodiment of the invention, MXene(Ti3C2T) X It was synthesized using a selective etching method with LiF / HCl as the etching solution. A schematic diagram of its preparation is shown below. Figure 1 As shown, the aluminum (Al) layer was removed from the parent Ti3AlC2 matrix by acid etching, and a multilayer MXene clay was inserted, followed by ultrasonic layering to obtain a single layer of MXene. The preparation method of MXene has been reported in the inventor's previous research; please refer to invention patent publication number CN118755148A for details. The specific experimental steps are as follows:

[0081] (1) Dissolve 1.0g LiF in 20mL 9M HCl solution at room temperature. Stir for 20min under magnetic stirring. Then slowly add 1.0g Ti3AlC2 to the above mixture solution and stir at 35℃ for 24h.

[0082] (2) After reacting for 24 hours, centrifuge the product at 3500 rpm for 5 minutes and discard the supernatant.

[0083] (3) Add 1M hydrochloric acid and deionized water and centrifuge and wash repeatedly until the pH is greater than 5.

[0084] (4) Discard the supernatant, add water, and sonicate the solution in an ice bath under nitrogen for 1 hour and centrifuge for 1 hour to collect the supernatant, thus preparing a monolayer MXene suspension (concentration of 10 mg / mL).

[0085] The prepared MXene was characterized by Tyndall effect experiments, transmission electron microscopy, atomic force microscopy, scanning electron microscopy, and X-ray diffraction. The results showed that the MXene nanosheets prepared by this invention exhibited excellent dispersibility in water; the MXene nanosheets displayed an ultrathin but relatively smooth two-dimensional monolayer sheet structure, with a thickness of 3.3 nm and a lateral dimension of 1.5 μm. Furthermore, XRD results showed that the (002) peak of the monolayer MXene was more intense than that of the MAX phase peak, indicating that the Al layer etching was relatively complete and that the acid-etched MXene preparation was successful. After etching, insertion, and further layering, the obvious (002) peak shifted from the typical 2θ angle of 9.7° in the parent MAX phase to a lower 2θ angle of approximately 6.5°, which is a typical characteristic of MXene nanosheets.

[0086] Due to the ultrathin thickness of MXene nanosheets and the Fe introduced during subsequent hydrogel fabrication... 3+ The synergistic effect of these factors gives it a large number of active sites and high conductivity, thus improving its activity.

[0087] Example 1. G-MXene-PAA-Fe 3+ Preparation method of self-healing conductive hydrogel

[0088] (1) Preparation of MXene: 1.0 g LiF was dissolved in 20 mL of 9 M HCl solution at room temperature and magnetically stirred for 20 min to obtain an etching solution; 1.0 g Ti3AlC2 was slowly added to the etching solution, stirred at 35 °C for 24 h, centrifuged at 3500 rpm for 5 min, and the supernatant was discarded; 1 M hydrochloric acid and deionized water were added and centrifuged and washed multiple times until the pH of the supernatant was >5; after discarding the supernatant, water was added again, and the solution was sonicated in an ice bath under nitrogen for 1 h and centrifuged for 1 h to collect the supernatant and prepare a monolayer MXene suspension.

[0089] (2) Preparation of modified MXene: Take 2.5 mL of the monolayer MXene suspension obtained in step (1), add 17.5 mL of premixed L-ascorbic acid solution, sonicate for 5 min, and then shake on a shaker for 5 h to obtain 20 mL of G-MXene dispersion; after freeze-drying the obtained G-MXene dispersion, use deionized water to reconstitute the G-MXene dispersion with a concentration of 10 mg / mL.

[0090] (3) Preparation of G-MXene-PAA self-healing conductive hydrogel

[0091] Under the action of ultrasound, 500 μl of deionized water, 175 μl of G-MXene dispersion (concentration of 10 mg / mL), 250 μl of AA monomer and 50 μl of APS solution (concentration of 50 mg / mL) were added sequentially and dispersed uniformly to obtain G-MXene-PAA self-healing conductive hydrogel.

[0092] (4)G-MXene-PAA-Fe 3+ Preparation of self-healing conductive hydrogels

[0093] The G-MXene-PAA self-healing hydrogel obtained in step (3) was immersed in FeCl3 solution (concentration of 15 mg / mL) at room temperature for 30 min to obtain G-MXene-PAA-Fe 3+ Self-healing conductive hydrogel. The amount of FeCl3 solution is calculated based on a 3 mol% AA ratio.

[0094] Example 2. Antioxidant modification of MXene

[0095] MXene nanosheet dispersions were modified with L-ascorbic acid aqueous solution as an antioxidant to ensure a reducing environment. After sonication for 5 min, the dispersions were placed on a shaker and kept vibrating for 5 h to obtain a stable dispersion. In addition, the MXene colloid was diluted with deionized water to the same concentration, and after sonication, a controlled dispersion was obtained. At this point, the concentrations of the two MXene dispersions were the same (1.25 mg / mL). Based on experimental conditions, two dispersions diluted to the same concentration were placed in small glass bottles at room temperature, sonicated until uniform dispersion, and their oxidation process was observed. On the other hand, the antioxidant-modified monolayer G-MXene dispersion was freeze-dried and prepared to have the same concentration as the unmodified monolayer MXene dispersion. After sonication, both were stored at low temperature for later use in hydrogel preparation. The operation steps are as follows:

[0096] ① Antioxidant Modification Group

[0097] For every 2.5 mL of MXene nanosheet dispersion prepared, 17.5 mL of premixed L-ascorbic acid solution was added, and after sonication for 5 min, the mixture was placed on a shaker and kept vibrating for 5 h to obtain 20 mL of G-MXene dispersion.

[0098] ② Unmodified control group

[0099] For every 2.5 mL of MXene nanosheet dispersion prepared, 17.5 mL of deionized water was added, and the mixture was sonicated to obtain 20 mL of MXene dispersion.

[0100] Example 3. Optimization of preparation conditions for self-healing conductive hydrogel

[0101] (1) Preparation of MXene-PAA self-healing conductive hydrogel and G-MXene-PAA self-healing conductive hydrogel

[0102] MXene-PAA / G-MXene-PAA nanocomposite hydrogels were prepared by in-situ free radical polymerization of AA monomers in the presence of MXene / G-MXene nanosheets and initiator APS. The specific method is as follows: An antioxidant-modified G-MXene dispersion was freeze-dried to obtain a sponge-like powder solid. This powder was then dissolved in a certain amount of deionized water and sonicated for 10 min to prepare a G-MXene dispersion with the same concentration as the unmodified MXene dispersion. Under ultrasonication, deionized water, MXene / G-MXene dispersion (10 mg / mL), AA monomer, and APS solution (50 mg / mL) were added sequentially in different proportions to maintain uniform dispersion, resulting in MXene-PAA self-healing conductive hydrogels and G-MXene-PAA self-healing conductive hydrogels.

[0103] This experiment investigated the effects of different AA / APS ratios and different amounts of MXene on the properties of the prepared hydrogels. The specific groupings are shown in Tables 3 and 4.

[0104] Table 3. Experimental grouping of MXene-PAA hydrogel 1

[0105] AA:APS (volume ratio) AA(μl) MXene / G-MXene(μl) APS(μl) <![CDATA[H2O(μl)]]> 1:1 150 175 150 500 2:1 200 175 100 500 3:1 225 175 75 500 4:1 240 175 60 500 5:1 250 175 50 500 6:1 257 175 43 500 7:1 263 175 37 500 8:1 267 175 33 500

[0106] Table 4. Experimental Group 2 of MXene-PAA Hydrogel

[0107]

[0108]

[0109] (2)MXene-PAA-Fe 3+ / G-MXene-PAA-Fe 3+Preparation of self-healing conductive hydrogels

[0110] The prepared MXene-PAA / G-MXene-PAA self-healing hydrogel was immersed in FeCl3 solution (15 mg / mL) at room temperature for 30 min. The amount of FeCl3 solution was calculated based on a 3 mol% AA ratio. Complete absorption and uniform coordination crosslinking were allowed to form MXene-PAA-FeCl3. 3+ / G-MXene-PAA-Fe 3+ Self-healing conductive hydrogel. Fe 3+ The uniform distribution of MXene nanosheets throughout the hydrogel facilitates the uniform formation of Fe between the hydroxyl groups of the MXene nanosheets and the carboxyl groups of the PAA chains. 3+ Mediated coordination crosslinking further enhances its crosslinking mechanism, as shown in the schematic diagram below. Figure 2 As shown.

[0111] Example 4. Characterization of MXene antioxidant modification

[0112] (1) Light visual observation

[0113] A stable G-MXene dispersion diluted with L-ascorbic acid aqueous solution at a certain concentration was stored in sealed glass bottles for several days at room temperature. Conversely, a control dispersion of MXene diluted with deionized water at a certain concentration was stored in sealed glass bottles for the same number of days under the same conditions. No degassing was performed before or during storage, ensuring contact between the MXene dispersion solution and the headspace (air) of the bottles. Changes in the degree of dispersion and stability of both dispersions were observed over 22 days.

[0114] 1) High concentration group

[0115] Take 5 mL of the prepared 1.25 mg / mL G-MXene stable dispersion and MXene controlled dispersion and store them in a sealed glass bottle for several days and observe.

[0116] 2) Low concentration group

[0117] Dilute the 1.25 mg / mL stable G-MXene dispersion and the controlled MXene dispersion to a concentration of 0.5 mg / mL, then take 5 mL of each and store them in a sealed glass bottle for several days and observe.

[0118] result: Figure 3Photographs of MXene and G-MXene solutions at a concentration of 1.25 mg / mL collected at different times are shown to investigate oxidative stability. Both MXene and G-MXene dispersions initially appeared black, but after two days of exposure in water, the MXene dispersion showed stratification, while the G-MXene dispersion did not show significant visual change. This indicates that MXene nanosheets stored in water are more prone to aggregation and precipitation, while the G-MXene solution on the right is uniform and stable under the same conditions, suggesting that the L-ascorbic acid-modified G-MXene solution possesses a certain degree of stability. Repeat experiments were performed with lower concentrations of MXene and G-MXene dispersions (0.5 mg / mL), yielding the same observations; see [link to relevant documentation]. Figure 9 .

[0119] Continuous observation showed that the MXene dispersion remained layered from day 5 to 8, while the G-MXene dispersion remained relatively stable and black. Afterward, the layered MXene dispersion was shaken, and the solution continued to separate into layers over time. Figure 3 and Figure 4 It can be seen that, regardless of the concentration, after shaking both dispersions on day 14, the MXene dispersion in deionized water showed obvious aggregation and the formation of particulate matter, which was more easily observed under sunlight. In contrast, the G-MXene dispersion remained uniformly distributed and appeared black or dark green. The particulate matter in the MXene dispersion is due to the visible precipitation of titanium dioxide (TiO2) and carbon formed after the oxidation of MXene nanosheets, indicating that the MXene dispersion had undergone significant oxidation at this point.

[0120] From then until day 22, the MXene dispersion gradually turned gray to white, while the G-MXene dispersion remained relatively stable and black, indicating that the MXene nanosheets in the MXene dispersion degraded faster. This leads to the conclusion that monolayer MXene nanosheets treated with L-ascorbic acid become more stable in an oxygen-rich environment. This demonstrates that MXene nanosheets can be protected from severe oxidation after prolonged storage in L-ascorbic acid sodium aqueous solution, confirming the successful antioxidant modification of MXene in this experiment.

[0121] (2) X-ray photoelectron spectroscopy (XPS)

[0122] Equal amounts of the prepared monolayer MXene dispersion and G-MXene dispersion were taken and filtered under vacuum to form membranes. The filtered membranes were then puffed with nitrogen at room temperature for 5 minutes and sealed for storage, allowing them to dry uniformly. X-ray photoelectron spectroscopy (XPS) was used to study the surface chemical properties of the (Ti3AlC2)MAX phase, MXene, and G-MXene samples. XPS utilized highly characteristic binding energies to perform qualitative analysis of the elemental composition of the MAX phase and MXene materials, observing the intensity of the titanium dioxide peak and the Ti peak in the nanosheets. This determined whether the MXene modification was successful.

[0123] Results: XPS analysis of the samples showed significant differences in chemical composition among the (Ti3AlC2)MAX phase, MXene, and G-MXene. Figure 5 As shown in Figure -A, the XPS measurement spectrum of the (Ti3AlC2)MAX phase shows a peak at 77.0 eV corresponding to Al, but below the detection limits of MXene and G-MXene. This indicates that HF ​​treatment of the MAX powder removed most of the Al layer. The measured spectrum of MXene showed an F peak at 685.0 eV, with an atomic content of 10.82%, which is due to the addition of fluorine during the HF etching process. After L-ascorbic acid treatment, the fluorine content decreased significantly to 8.66%. This indicates that L-ascorbic acid treatment significantly altered the surface chemistry of MXene, and the antioxidant treatment could remove a large amount of F from MXene.

[0124] High-resolution spectra of Ti2p, such as Figure 5 As shown in -B, the fitted peak is Ti. + Ti 2+ Ti 3+ and Ti 4+ (Titanium dioxide). For the prepared MXene nanosheets stored in deionized water and in L-ascorbic acid solution, titanium dioxide (Ti) 4+ Titanium dioxide (Ti) contains a relatively low atomic composition in the Ti2p region. However, for samples stored in water, the atomic composition is higher. 4+ The sample contains a much higher atomic fraction, which is confirmed by the high-intensity peak around 462 eV, evidence of severe oxidation of MXene. Observe the Ti in deionized water in the figure. 4+ Ti 3+ Ti 2+ and Ti + As expected, under aging conditions in water, we observed an increase in the relative atomic composition of Ti species in the oxidized state (i.e., Ti...). 2+ and Ti 3+ Oxidized to Ti 4+ Ti +Oxidized to Ti 2+ and Ti 3+ In the presence of L-ascorbic acid, Ti + To Ti 2+ / Ti 3+ The chemical state transition of Ti is suppressed; 4+ Growth slows down over time.

[0125] (3) Conductivity test

[0126] At room temperature, the conductivity of the above-mentioned MXene and G-MXene films was tested by the four-probe method to verify whether the conductivity of the modified G-MXene dispersion is better.

[0127] Results: The conductivity of the original monolayer MXene dispersion was 2.2 S·m. -1 The electrical conductivity of G-MXene dispersions modified with L-ascorbic acid for antioxidant effects can reach 7.7 S·m. -1 This data further illustrates the success of L-ascorbic acid's antioxidant modification, demonstrating that it improves the stability of MXene dispersions, prevents oxidation in a short period of time, and retains the electrical conductivity of MXene materials to some extent.

[0128] Example 5. Gel formation analysis of MXene-based self-healing conductive hydrogel

[0129] As shown in Example 3, this invention synthesizes MXene-PAA hydrogels via in-situ free radical polymerization of acrylic acid (AA) monomers in the presence of MXene nanosheets and the initiator ammonium persulfate (APS). MXene nanosheets were used as a multifunctional crosslinking agent to construct the MXene-PAA hydrogel, which has a large number of polarized surface functional groups (-F, -OH, -O, etc.) that interact with the carboxyl groups on the PAA chains through hydrogen bonds. It should be noted that due to the presence of low-valent Ti(II) and Ti(III) substances, MXene nanosheets exhibit strong reducing properties; therefore, the redox reaction between the reduced MXene nanosheets and the oxidation initiator (APS) significantly lowers the decomposition activation energy of APS, generating a large number of free radicals. This also avoids the disadvantages of traditional AA free radical polymerization, which requires high temperatures, long polymerization times, and corrosive, highly neurotoxic crosslinking agents such as TEMED.

[0130] Gel-forming effect such as Figure 6As shown, rapid gelation of the MXene-PAA hydrogel can be observed at room temperature for approximately 10 minutes. However, due to the lack of reduced MXene-assisted free radical generation, a pure PAA hydrogel without MXene cannot be achieved at room temperature. This indicates that MXene nanosheets replace the role of N,N,N',N'-tetramethylethylenediamine (TEMED), catalyzing the generation of free radicals from APS. This not only avoids prolonged high-temperature free radical polymerization during gelation but also imparts conductivity.

[0131] Example 6. Mechanical property testing of MXene-based self-healing conductive hydrogel

[0132] To test the strength of the prepared hydrogels, a universal testing machine was used to test the strength of MXene-PAA / G-MXene-PAA hydrogels and MXene-PAA-Fe hydrogels. 3+ / G-MXene-PAA-Fe 3+ The mechanical properties of the hydrogel were measured.

[0133] (1) Compression test

[0134] Compression tests were performed on the prepared hydrogel cylindrical sample (11 mm in diameter and 8.8 mm in height) at ambient temperature with a loading rate of 5 mm / min. The compressive load (F) and displacement (x) were recorded.

[0135] The formula for calculating compressive stress is as follows:

[0136]

[0137] Among them, Load value λ represents the load value in N; r represents the hydrogel radius in mm. Four parallel samples were tested in each group, and the average value of the test results was recorded.

[0138] The formula for calculating compressive strain is as follows:

[0139]

[0140] Where Position represents displacement in mm, and h represents hydrogel height in mm. Four parallel samples were tested in each group, and the average value of the test results was recorded.

[0141] The elastic modulus of the hydrogel is estimated by the slope of the straight line fitted to the stress-strain curve from 0% strain to the 10% strain before fracture.

[0142] The test results are as follows:

[0143] 1) The ratio of AA to APS: such as Figure 7 As shown, when the finger compresses G-MXene-PAA-Fe3+ When a hydrogel is compressed and deformed, it does not break; when the force applied by the finger is removed, the hydrogel quickly rebounds from the compressed state and returns to its original shape, demonstrating the excellent resilience of the hydrogel sample. The compressive mechanical properties of hydrogels are generally characterized by their elastic modulus; the higher the elastic modulus of a hydrogel, the less easily the material is deformed. Figure 8 , Figure 9 As can be seen from this, compared with MXene-PAA hydrogel, the introduction of Fe... 3+ The MXene-PAA-Fe obtained later 3+ The elastic modulus of the hydrogel was improved, particularly when AA:APS = 5:1, MXene-PAA-Fe 3+ The elastic modulus of the hydrogel (76.589 kPa) is 22.125 kPa higher than that of the MXene-PAA hydrogel (54.464 kPa). This is because soaking in FeCl3 solution establishes a hydrogel with a large number of uniformly coordinated crosslinks, thereby improving the mechanical strength of the hydrogel.

[0144] It should be noted that this invention uses G-MXene-PAA-Fe nanosheets that have undergone antioxidant modification. 3+ Hydrogel, possessing higher performance than MXene-PAA and MXene-PAA-Fe 3+ The higher elastic modulus of the hydrogel (96.046 kPa) demonstrates that L-ascorbic acid minimized the oxidation of MXene nanosheets during the hydrogel preparation process, the demolding process, and the measurement of hydrogel compressive mechanics, thus preserving its superior mechanical strengthening properties as much as possible. With changes in the AA:APS ratio, the elastic modulus of the three hydrogels showed a trend of first increasing and then decreasing. The 1:1, 7:1, and 8:1 ratios were not tested for compressive mechanics due to their excessively long gelation time, as longer gelation times increase production costs and make the hydrogels more susceptible to prolonged oxidation during preparation, leading to a shorter lifespan. The elastic modulus graphs of the three hydrogels show that the hydrogel with the AA:APS ratio of 5:1 has the highest elastic modulus, with G-MXene-PAA-Fe exhibiting the highest. 3+ The elastic modulus of the hydrogel can reach 96.046 kPa.

[0145] 2) Amount of MXene: such as Figure 10 As shown, when the content of G-MXene nanosheets increases to 175 μl, G-MXene-PAA-Fe 3+The elastic modulus of the hydrogel initially increased, then gradually decreased. Specifically, the superior mechanical strengthening effect of G-MXene nanosheets lies in their larger specific surface area and more polarized functional groups, effectively transferring applied stress to more PAA chains. However, excessive G-MXene nanosheets, without a corresponding number of carboxyl groups on the PAA chains to interact with them, can lead to incomplete gelation and a decrease in compressive modulus.

[0146] (2) Tensile test

[0147] Tensile tests were performed on the prepared rectangular hydrogel samples (30 mm long, 10 mm wide, and 2 mm high) at ambient temperature with a loading rate of 100 mm / min and a measurement length of 15 mm between the clamps. The tensile load (F) and displacement (x) were recorded.

[0148] The formula for calculating tensile stress is as follows:

[0149] Stress (kPa) = 1000F ÷ S

[0150] Where F is the tensile load in N; and S is the cross-sectional area in mm. 2 .

[0151] The formula for calculating tensile strain is as follows:

[0152] Strain = x ÷ l0

[0153] Where x is the displacement and l0 is the measuring length between the fixtures, in mm.

[0154] The toughness (E) of the hydrogel is estimated by the area under the stress-strain curve from 0% strain to fracture strain (ζβ), and the calculation formula is as follows:

[0155]

[0156] The measurement results are as follows:

[0157] 1) The ratio of AA to APS: The tensile mechanical properties of hydrogels are generally characterized by toughness and elongation at break. Toughness is an important mechanical property indicator for measuring the toughness of a material; the higher the value, the smaller the elastic deformation of the material under the same stress conditions. For example... Figure 11 As shown, when AA:APS = 5:1, G-MXene-PAA-Fe 3+ Hydrogels exhibit the greatest toughness, reaching 1443.756 kPa, with an elongation at break of 926.7%.

[0158] 2) Amount of MXene:

[0159] like Figure 12As shown, when the content of G-MXene nanosheets increases to 175 μl, G-MXene-PAA-Fe 3+ The toughness of the hydrogel initially improved, then gradually decreased. Specifically, the superior mechanical strengthening effect of G-MXene nanosheets lies in their larger specific surface area and more polarized functional groups, effectively transferring applied stress to more PAA chains. Similar to compressive mechanical properties, excessive G-MXene nanosheets, without a corresponding number of carboxyl groups on the PAA chains to interact with them, can lead to incomplete gelation, resulting in a corresponding decrease in tensile mechanical properties.

[0160] The results in summary indicate that G-MXene-PAA-Fe was prepared under the following conditions: 175 μL of G-MXene, 250 μL of acrylic acid monomer, 50 μL of ammonium persulfate solution, and 500 μL of H2O (i.e., G-MXene: acrylic acid monomer: ammonium persulfate solution: H2O = 3.5:5:1:10). 3+ Hydrogels have the best mechanical properties.

[0161] Example 7. Self-healing performance test of MXene-based self-healing conductive hydrogel

[0162] The G-MXene-PAA-Fe prepared in this experiment 3+ Hydrogels possess multiple hydrogen bonds and Fe 3+ The self-healing property of the hydrogel is attributed to the metal-coordinate bonds at the coordination center. Due to the combined effect of multiple hydrogen bonds and metal-coordinate bonds, this hydrogel exhibits excellent self-healing properties. At room temperature, the hydrogel sample (AA:APS = 5:1, MXene content 175 μl) was uniformly cut into two equal parts, and the fractured surfaces of the two parts were seamlessly placed together. The self-healing process was observed without any external forces. Then, under the same test conditions, a mechanical compression test was performed on the self-healed hydrogel. After the test, the compressive mechanical properties of the self-healing hydrogel were compared with those of the original hydrogel to verify the superiority of its self-healing performance and calculate its self-healing rate.

[0163] The formula for calculating the self-healing rate is as follows:

[0164]

[0165] Where E1 is the elastic modulus of the self-healing hydrogel, and E0 is the elastic modulus of the original hydrogel.

[0166] Results: The G-MXene-PAA-Fe prepared in this invention... 3+ Hydrogels exhibit excellent self-healing properties due to the combined effects of multiple hydrogen bonds and metal coordination bonds. For example... Figure 13As shown, G-MXene-PAA-Fe 3+ The hydrogel sample healed rapidly within 15 minutes, with no visible gaps, and one side could be held in the air with tweezers, indicating that the hydrogel had essentially healed. After 12 hours, the hydrogel was completely healed, and both ends could be pulled apart; applying force with tweezers was no longer sufficient to separate them. Testing the mechanical properties of the healed hydrogel revealed an elastic modulus of 83.960 kPa, which was not significantly different from the elastic modulus of the hydrogel before cutting (89.125 kPa), indicating that the G-MXene-PAA-Fe prepared in this invention... 3+ The hydrogel exhibits excellent self-healing properties. The calculated self-healing rate of this hydrogel is 94.2%.

[0167] Example 8. Conductivity test of MXene-based self-healing conductive hydrogel

[0168] (1) Dynamic hydrogel-based circuit testing

[0169] Power supply, switch, G-MXene-PAA-Fe 3+ A hydrogel (AA:APS = 5:1, MXene content 175μl) and a red light-emitting diode (LED) bulb were connected in a closed circuit with wires to observe whether the LED bulb could be successfully lit under an applied voltage. The hydrogel was then cut in half, breaking the circuit. The broken surfaces of the hydrogel were then brought together again, and the brightness of the LED bulb was observed.

[0170] Result: As Figure 14 As shown in -A, the power supply, switch, G-MXene-PAA-Fe 3+ A hydrogel (AA:APS = 5:1, MXene amount 175μl) and a red light-emitting diode (LED) bulb were connected in a closed circuit with wires. The LED bulb successfully lit up under an applied voltage. When the hydrogel was cut in half, the circuit was broken, and the bulb went out. Figure 14 -B; After bringing the fractured surfaces of the hydrogel back together, the brightness of the LED bulb is not significantly different from before, such as... Figure 14 -C. When the hydrogel conductor is cut, the bulb dims, but once the two separated hydrogel parts re-contact, the LED bulb immediately emits a bright light, indicating that the conductive hydrogel immediately achieves electrical recovery. This rapid electrical recovery is due to numerous reversible interactions between polarized surface functional groups (-F, -OH, =O, etc.), such as MXene nanosheets, PAA, and Fe. 3+ The carboxyl group. Furthermore, numerous dynamic interactions enable G-MXene-PAA-Fe... 3+Hydrogels exhibit excellent self-healing capabilities in terms of mechanical properties. Therefore, the obtained hydrogels possess near-instantaneous mechanical and electrical self-healing abilities, making them promising candidates for wearable smart strain sensors in reliable and flexible electronic devices.

[0171] (2) Conductivity test

[0172] G-MXene-PAA-Fe with different MXene concentrations was measured using the four-probe method. 3+ The electrical conductivity of the hydrogel was measured in a cylindrical sample with a diameter of 11 mm and a height of 8.8 mm.

[0173] Result: As Figure 15 As shown, the conductivity of the hydrogel sample gradually increases with the amount of MXene. However, when the amount of MXene is 205 μl, the conductivity decreases. This may be because the hydrogel sample surface is uneven due to poor gelation, resulting in inaccurate conductivity testing.

[0174] (3) Changes in the electrical resistance of the hydrogel after 14 days of storage

[0175] MXene-PAA-Fe were measured separately. 3+ Hydrogel and G-MXene-PAA-Fe 3+ The electrical resistance changes of the hydrogel (AA:APS = 5:1, MXene content 175 μl) were observed after 14 days of storage in a normal environment, and the changes were compared to verify whether the antioxidant modification of MXene successfully improved the stability of the hydrogel.

[0176] Result: As Figure 16 As shown, with MXene-PAA-Fe 3+ Compared to hydrogels, G-MXene-PAA-Fe 3+ The electrical resistance change of the hydrogel over 14 days was relatively weak. On day 7, MXene-PAA-Fe... 3+ The resistance change of the hydrogel is G-MXene-PAA-Fe 3+ The hydrogel resistance changed 3.14 times; by day 14, MXene-PAA-Fe 3+ The hydrogel resistance changed by 16.1%, G-MXene-PAA-Fe 3+ The hydrogel resistance changed by 3.5%, representing a 4.6-fold increase. This result indicates that L-ascorbic acid has a good antioxidant modification effect, enabling the MXene-based hydrogel to maintain a certain degree of electrical stability over a relatively long period.

[0177] Example 9. Sensing Test of MXene-based Self-healing Conductive Hydrogel

[0178] (1) Sensitivity

[0179] In the strain sensing experiment, a rectangular prism with a thickness of 3 mm, a length of 30 mm, and a width of 5 mm, and a cylindrical prism with a diameter of 11 mm and a height of 8.8 mm were prepared. 3+ Hydrogel sample (AA:APS = 5:1, MXene content 175 μl). The G-MXene-PAA-Fe hydrogel sample was obtained by stretching. 3+ Hydrogels were used to evaluate their electrical sensitivity as strain sensors. The strain sensitivity of hydrogels was quantitatively assessed using the measurement factor (GF); a higher GF value indicates higher sensitivity. The formula for calculating GF is as follows:

[0180]

[0181] Where ΔR is the change in resistance, ΔR=R-R0; R0 is the initial resistance of the hydrogel, R is the resistance at a certain moment during the stretching / compression process, and ε is the strain at that moment.

[0182] Result: As Figure 17 -A、 Figure 17 -B、 Figure 17 As shown in Figure -C, the resistance of the hydrogel sample changes with different strains during tensile strain testing. A line graph is then plotted with strain (%) on the x-axis and ΔR / R on the y-axis, and a straight line is fitted; the slope is the measurement factor GF. For example... Figure 17 -D as shown, G-MXene-PAA-Fe 3+ The sensitivity of the self-healing hydrogel is 3.68.

[0183] (2) Using G-MXene-PAA-Fe 3+ A hydrogel (AA:APS = 5:1, MXene content 175 μl) was used to simulate a wearable electronic sensor to monitor finger flexion movements. The hydrogel was cut into rectangular samples with a thickness of 2 mm, a length of 20 mm, and a width of 5 mm. The G-MXene-PAA-Fe hydrogel was used to measure finger flexion angles from 0° to 90° using a multimeter. 3+ Changes in the resistance of hydrogels.

[0184] Result: As Figure 18 As shown, G-MXene-PAA-Fe is recorded in real time as the finger bends from 0-90°. 3+ The relative change in resistance of the hydrogel sample. The hydrogel sensor can accurately detect different bending angles of the finger in real time, and immediately restores the initial resistance once the finger returns to its original unbent state.

[0185] (3) Repeat the finger and wrist flexion process and continuously measure G-MXene-PAA-Fe. 3+ The change in hydrogel resistance further verifies the stability of the hydrogel.

[0186] Result: As Figure 19 As shown, the sensor's real-time relative resistance changes are observed when the finger and wrist are bent, respectively. During repeated bending, the hydrogel sensor consistently and stably outputs the relative resistance change, further validating the performance of G-MXene-PAA-Fe. 3+ The stability of hydrogels in sensor applications suggests that the obtained hydrogels have potential applications as wearable smart strain sensors.

Claims

1. G-MXene-PAA-Fe 3+ A self-healing conductive hydrogel, characterized in that... The preparation was carried out using the following method: S1: Under the action of ultrasound, deionized water, modified G-MXene, acrylic monomer and ammonium persulfate solution were added in sequence and uniformly dispersed to obtain G-MXene-PAA hydrogel; S2: The G-MXene-PAA hydrogel obtained in S1 is immersed in a FeCl3 solution to obtain G-MXene-PAA-Fe 3+ Self-healing conductive hydrogel; In S1, the modified G-MXene is obtained by modifying MXene with L-ascorbic acid, and the volume ratio of MXene to L-ascorbic acid is 1:5~10; the volume ratio of deionized water, the modified G-MXene, the acrylic acid monomer and the ammonium persulfate solution is 500:170~180:230-270:50; In S2, the amount of FeCl3 solution used is 2-4 mol% of the acrylic acid monomer, and the concentration of the FeCl3 solution is 15 mg / mL; the soaking time is 25-60 minutes.

2. The self-healing conductive hydrogel according to claim 1, characterized in that, The volume ratio of MXene to L-ascorbic acid is 1:

7.

3. The self-healing conductive hydrogel according to claim 1, characterized in that, The volume ratio of the acrylic monomer to the ammonium persulfate solution is 5:

1.

4. The self-healing conductive hydrogel according to claim 1, characterized in that, In S1, the volume ratio of the deionized water, the modified G-MXene, the acrylic monomer, and the ammonium persulfate solution is 10:3.5:5:

1.

5. The self-healing conductive hydrogel according to claim 1, characterized in that, In S2, the amount of FeCl3 solution used is 3 mol of the acrylic acid monomer.

6. The self-healing conductive hydrogel according to claim 1, characterized in that, The modified G-MXene is prepared as follows: (1) Add Ti3AlC2 to LiF / HCl etching solution and synthesize MXene by selective etching; (2) The MXene obtained in step (1) was modified by L-ascorbic acid to obtain the modified G-MXene.

7. The G-MXene-PAA-Fe of any one of claims 1-6 3+ Use of self-healing conductive hydrogel in the preparation of wearable flexible sensors.

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