CN113800521A

CN113800521A - High-stability self-linked MXene nanosheet and preparation method and application thereof

Info

Publication number: CN113800521A
Application number: CN202111114668.5A
Authority: CN
Inventors: 黄逸凡; 高明; 江敏; 谢晋兴; 万志颖; 梅婷婷
Original assignee: Shenzhen Institute of Advanced Technology of CAS
Current assignee: Shenzhen Institute of Advanced Technology of CAS
Priority date: 2021-09-23
Filing date: 2021-09-23
Publication date: 2021-12-17
Also published as: WO2023045115A1

Abstract

The invention provides a high-stability self-linking MXene nanosheet and a preparation method and application thereof, and particularly provides a surface-modified MXene nanosheet, wherein the MXene nanosheet is provided with a Na ion and sulfonic acid intercalation layer, and meanwhile, the surface is also provided with a polydopamine layer and a polyethylene dioxythiophene layer; the polydopamine layer and the polyethylene dioxythiophene layer are sequentially arranged; specifically, a polydopamine layer is polymerized on the surface of an MXene nanosheet with Na ions and sulfonic acid intercalation, and then a polyethylene dioxythiophene layer is polymerized in situ. The MXene nanosheets interact among various modifications, and simultaneously strengthen various properties of the MXene nanosheets such as physical and chemical stability, film forming capability, biocompatibility and the like in a living body, so that the MXene nanosheets can be used as electrode modification materials, cell repair materials for peripheral nerves, leads for nerve electrodes, sites for central nerve electrodes and the like.

Description

High-stability self-linked MXene nanosheet and preparation method and application thereof

Technical Field

The invention belongs to the field of biological materials, and particularly relates to a high-stability self-linked MXene nanosheet and a preparation method and application thereof.

Background

The unusual characteristics of graphene mechanically exfoliated from graphite indicate that electrical, optical, mechanical and electrochemical properties can be deeply adjusted by thinning the thickness of a three-dimensional material to a two-dimensional atomic sheet, and this breakthrough finding greatly facilitates the research on the synthesis and characterization of high-quality two-dimensional materials other than graphene. MXenes is a new class of two-dimensional materials that has attracted increasing research attention in many respects, standing at the front of the two-dimensional material community. MXene materials are layered two-dimensional carbon/nitrides and are usually obtained by chemical etching to extract a layer a of atomic layers from the MAX phase (Mn +1AXn, N1-3, M is a transition metal, a is a group IIIA or IVA element, and X is C or N) of its parent phase material. To date, over 30 MXene materials have been synthesized experimentally, and more (hundreds) are expected to be thermodynamically stable. Thus, unlike other two-dimensional materials, MXenes itself is a broad class of materials with many properties such as high conductivity, volumetric capacitance, and electromagnetic interference shielding. These excellent results indicate that MXenes has promise in many applications such as electrochemical energy storage, electrical contacts for transparent conductive electrodes and thin film transistors, electromagnetic interference shielding, photodetectors, sensing, and the like. The core of these applications is the fabrication of advanced MXene-based architectures, including nanostructured electrodes, high quality continuous films/contacts, and patterns of functional devices.

Until now, the application of MXene materials in the field of bioengineering mainly focuses on drug loading, conductive polymers and electrode modification, but has little application in the field of neuroscience. The reasons for this are mainly that MXene is easily oxidized and diffused in tissues and has low biocompatibility making it difficult to apply MXene to complex nervous systems.

The modification of MXene materials in the prior art usually focuses on the improvement of certain characteristics such as conductivity, dispersibility and stability, particularly stability, and the conventional modification modes such as the introduction of sodium sepsis, an ionic dispersing agent and the like are used for passivating the edge lattice defects of the materials, and the modification modes can cause the reduction of other properties.

Publication No. CN 111447968A discloses an implant device using 2D metal carbide and nitride (MXene), and specifically discloses a contact material comprising MXene, which further comprises a conductive polymer such as poly (3, 4-ethylenedioxythiophene) or the like. However, in this patent, there is no disclosure of how to prepare a conductive polymer, and polyethylenedioxythiophene is generally obtained by three methods, chemical polymerization, electropolymerization, and photopolymerization. The electropolymerization and photopolymerization can not realize the surface modification of the nanosheets, and can only be used for plating, film coating or volume forming and the like. However, in situ polymerization of ethylenedioxythiophene on MXene is difficult because conventional ethylene dioxythiophene chemical polymerization requires the use of oxidative catalysts containing ferric ions, and MXene is destroyed due to its strong reducing properties.

Patent publication No. CN 109096754 a discloses an MXene-polydopamine composite material obtained by reacting MXene and dopamine to obtain poly-dopamine polymerized in situ, but this solution has a long polymerization time, which takes 24 hours due to weak polymerization activity because polymerization is performed directly on the surface of MXene. In addition, the polymerized dopamine is placed on the surface of MXene and directly contacts with the outside, so that the dopamine is easily influenced by an excessively strong oxidation environment to cause structural damage, and the effect of maintaining the stability of the poly dopamine layer which originally can increase the stability is partially lost.

Disclosure of Invention

The invention aims to provide an MXene nanosheet capable of adapting to a complex in-vivo environment aiming at the defects and shortcomings of the prior art, and simultaneously enhances various properties of the MXene nanosheet such as physical and chemical stability, film forming capability, biocompatibility and the like in a living body.

One aspect of the invention provides a surface-modified MXene nanosheet, wherein the MXene nanosheet is provided with Na ions and sulfonic acid intercalation, and meanwhile, the surface is also provided with a polydopamine layer and a polyethylene dioxythiophene layer.

In a solution of the invention, the layer of polyethylene dioxythiophene is selected from a layer of poly (3, 4-ethylene dioxythiophene), or a layer comprising a polymer of poly (3, 4-ethylene dioxythiophene).

In the technical scheme of the invention, the Na ions and the sulfonic acid intercalation are obtained by the following method: dispersing the two-dimensional MXene nanosheets in an alkaline solution containing sodium ions, and mixing to obtain Na ion intercalated two-dimensional MXene nanosheets; reacting the two-dimensional MXene nanosheet intercalated by the Na ions with sulfanilic acid diazonium salt to obtain the MXene nanosheet intercalated and modified by the Na ions and the sulfonic acid.

In the technical scheme of the invention, the polydopamine layer and the polyethylene dioxythiophene layer are sequentially arranged.

In an embodiment of the present invention, the polyethylene dioxythiophene layer accounts for 0.01% to 50% of the total mass of the surface-modified MXene nanosheets, for example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%.

According to the technical scheme, MXene is intercalated by Na ions, then the MXene is stripped to a single layer or a few layers by sulfonic acid intercalation, then a dopamine layer is polymerized on the surface of the MXene nanosheet, and finally ethylene dioxythiophene is polymerized in situ.

In the technical scheme of the invention, the in-situ polymerized polydopamine layer is obtained by mixing and reacting dopamine or pre-polymerized dopamine and MXene nano-sheets with Na ions and sulfonic acid intercalation

In the technical scheme of the invention, the pre-polymerized dopamine is obtained by dispersing dopamine in an alkaline buffer.

In the technical scheme of the invention, the polyethylene dioxythiophene layer is obtained by carrying out in-situ polymerization on ethylene dioxythiophene. Preferably, the ethylenedioxythiophene is selected from 3, 4-ethylenedioxythiophene.

In the technical scheme of the invention, no catalyst with oxidation is added in the polymerization process of the polyethylene dioxythiophene layer. Such as a catalyst comprising ferric ions.

In the technical scheme of the invention, the substrate of the MXene nanosheet is selected from Ti₃C₂、Ti₂C、Nb₂C、V₂C、Mo₂C。

In the technical scheme of the invention, the surface-modified MXene nanosheet is obtained by the following method:

1) intercalation modification of Na ions and sulfonic acid: dispersing the two-dimensional MXene nanosheets in an alkaline solution containing sodium ions, and mixing to obtain Na ion intercalated two-dimensional MXene nanosheets; reacting the two-dimensional MXene nanosheets intercalated by Na ions with sulfanilic acid diazonium salt to obtain intercalated and modified MXene nanosheets of Na ions and sulfonic acid;

2) polymerization of dopamine by michael addition reaction: pre-polymerizing dopamine in an alkaline buffer solution, and then mixing and reacting the pre-polymerized solution with the intercalated and modified MXene nanosheets of Na ions and sulfonic acid to obtain the intercalated and modified MXene nanosheets with a polymerized dopamine layer and Na ions and sulfonic acid;

3) further in-situ polymerization to obtain a non-oxidized polyethylene dioxythiophene layer: dispersing ethylene dioxythiophene raw materials in a water-soluble organic solvent, adding the water-soluble organic solvent into the aqueous solution of the MXene nanosheets obtained in the step 2), and carrying out intercalation modification on the MXene nanosheets which are provided with a polymerized dopamine layer and a non-oxidized polyethylene dioxythiophene layer and contain Na ions and sulfonic acid under the condition that no oxidant is contained.

The invention also provides a preparation method of the surface modified MXene nanosheet, which comprises the following steps:

1) intercalation modification of Na ions and sulfonic acid: dispersing the two-dimensional MXene nano-substrate in an alkaline solution containing sodium ions, and mixing to obtain a Na ion intercalated two-dimensional MXene nano-sheet; reacting the two-dimensional MXene nanosheets intercalated by Na ions with sulfanilic acid diazonium salt to obtain intercalated and modified MXene nanosheets of Na ions and sulfonic acid;

In the technical scheme of the invention, the two-dimensional MXene nano substrate in the step 1) is selected from Ti₃C₂、Ti₂C、Ta₄C₃、Nb₂C、V₂C or Mo₂C, one or more of them in combination.

In the technical scheme of the invention, the two-dimensional MXene nano substrate in the step 1) is obtained by selectively etching MAX phase ceramics through HF acid.

In the technical scheme of the invention, the MAX phase ceramic in the step 1) is selected from Ti₃AlC₂、Ti₂AlC、Nb₂AlC、V₂AlC、Mo₂AlC、Ta₄AlC₃One or more of the above.

In the technical scheme of the invention, the methodThe alkaline solution containing sodium ions in the step 1) is selected from NaOH solution and Na₂CO₃Solution, NaHCO₃Solution, KOH solution, K₂CO₃Solution, KHCO₃And (3) solution.

In the technical scheme of the invention, after the sodium ion intercalation in the step 1), the sodium ion intercalation is washed to be neutral by using water, for example, the pH value is washed to be 7-8.

In the technical scheme of the invention, the sulfanilic acid diazonium salt in the step 1) is obtained by reacting sulfanilic acid, hydrochloric acid and sodium nitrite, preferably, the reaction is carried out at the temperature of-5-10 ℃.

In the technical scheme of the invention, in the step 1), sulfanilic acid diazonium salt and sodium ion intercalation MXene nanosheet react for 2-10 hours at 0-5 ℃, and large aggregates and unreacted particles are removed and separated by centrifugation.

In the technical scheme of the invention, the pH value of the alkaline buffer solution in the step 2) is selected from 8.5-9.

In the technical scheme of the invention, the mass ratio of the intercalated and modified MXene nanosheets of dopamine, Na ions and sulfonic acid in step 2) is 1:5-20, such as 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 and 1: 20.

In the technical scheme of the invention, the ethylene dioxythiophene raw material in the step 3) is selected from 3, 4-ethylene dioxythiophene.

In the technical scheme of the invention, the ratio of the raw material of ethylene dioxythiophene to the intercalation modified MXene nanosheets having a polymerized dopamine layer and Na ions and sulfonic acid in step 3) is 0.1 g to 15 g of raw material of ethylene dioxythiophene, such as 0.5 g, 1g, 2 g, 3g, 4g, 5 g, 6 g, 7 g, 8 g, 9 g, 10g, 11 g, 12 g, 13 g, 14 g and 15 g, added to every 1g of intercalation modified MXene nanosheets having a polymerized dopamine layer and Na ions and sulfonic acid.

In the technical scheme of the invention, no oxidant is added in the reaction in the step 3).

The invention further provides application of the surface modified MXene nanosheets as electrode modification materials, cell repair materials for peripheral nerves, leads for nerve electrodes and sites for central nerve electrodes.

In the technical scheme of the invention, the electrode modification material is selected from modification materials of electrodes for nerves, such as electrode modification for central nerves and peripheral nerves.

The invention further provides a biological electrode, and the surface of the electrode is provided with the MXene nanosheets with the modified surfaces as electrode surface modification materials.

In a further aspect, the invention provides a dispersion system, wherein the dispersion system comprises the surface-modified MXene nanosheets and a dispersion matrix selected from a hydrogel, an elastomer and a solvent.

In the technical scheme of the invention, the hydrogel is selected from at least one of polyacrylamide hydrogel, polyvinyl alcohol hydrogel, hyaluronic acid derivatives, collagen, gelatin, fiber web protein, fibrinogen, alginate and chitosan. The solvent is selected from aqueous solution and organic solution.

In the technical scheme of the invention, the concentration of the surface-modified MXene nanosheets in the dispersion system is 0.1-10 mg/mL. For example, 0.5mg/mL, 1mg/mL, 2mg/mL, 3mg/mL, 4mg/mL, 5mg/mL, 6mg/mL, 7mg/mL, 8mg/mL, 9mg/mL, 10 mg/mL.

Advantageous effects

1. Aiming at the defect that the MXene material needs to be used in a living body, the chemical environment is complex and is easy to oxidize, so that the change of the electrical property is large, the lattice defect at the MXene boundary is passivated, the oxidation resistance is improved by utilizing the active redox activity, the MXene material is more suitable for the chemical environment in the living body, and the stability of the electrical property can be maintained. Specifically, an implantation experiment in a mouse was performed, and it was confirmed that the tissue near the material was healthy within 6 weeks, no oxidative stress occurred, and a certain amount of new blood vessels were observed.

2. For the aspects of volumetric biological applications such as electrodes, printed electronics and the like, the biomaterial is required to have low tissue diffusivity and cell erosion resistance, while the MXene material cells have excellent tissue adhesion capacity and reduced tissue diffusivity, so that the MXene material is very suitable for volumetric biological applications. In particular, the in vivo implantation experiment of the mice is carried out, and the material and tissue boundaries are clear and no obvious tissue diffusion occurs within 6 weeks. Furthermore we performed a gel viscosity test by mixing the nanoplatelets of the invention in a polyacrylamide hydrogel, comparing the viscosity of the polyacrylamide hydrogel without MXene addition and of the hydrogel without polymerized ethylenedioxythiophene. The results show that the polyacrylamide hydrogel with the addition of the inventive nanoplates has the strongest viscosity and viscosity stability on a time scale.

3. According to the invention, the stability and the dispersibility in dispersion systems such as hydrogel and elastomer can be realized without introducing graphene or changing the dispersion system.

4. The MXene of the invention is different from the film forming capability of MXene in the prior art, the MXene materials of the invention form a stable structure by means of covalent bond connection, and the MXene in the prior art is realized by the aid of the restacking of the sheet layers and the Van der Waals force between the sheet layers, so that the MXene of the invention has better film forming stability in water.

5. The MXene further increases the biocompatibility and the peroxidase activity of the material, and can realize the effects of increasing cell adhesion, reducing cell active oxygen and promoting migration and differentiation of nerve cells. We have conducted PC12, Row264.7 and S16 cell culture, and have proved that the MXene material of the invention can reduce the oxidative stress of cells and promote the adhesion, diffusion, division and differentiation of cells.

6. The material simultaneously strengthens the physical and chemical stability, the film forming capability, the biocompatibility and other properties of the MXene nanosheets in a living body from various aspects, so that the MXene nanosheets can be used for electrode modification of central nerves and peripheral nerves, can be used for manufacturing leads of electrodes of the central nerves and the peripheral nerves, and can also be used for cell repair of the peripheral nerves. Can effectively resist the oxidation pressure and cell erosion of the in vivo environment during operation.

7. MXene of the invention has a non-linear degradation rate. In the later stage of material work, the material is degraded at an accelerated speed, and the material has better self-removing capability, so that the material has good prospect in the field of degradable electrodes.

8. The MXene layers are modified cooperatively to obtain the composite material which is more suitable for being complex in vivo, high in stability, low in tissue diffusion and high in biocompatibility. Firstly, sulfonic acid and Na ion intercalation improves the electronic activity of the surface of the nano sheet, and promotes the subsequent in-situ nano-scale dopamine polymerization. Meanwhile, the Raman spectrum proves that the sodium sulfonate ion intercalation and the polydopamine layer added before the method can promote the in-situ polymerization of the ethylene dioxythiophene on the surface of the MXene nanosheet without an additional oxidant. Meanwhile, Raman spectrum also proves that the synthesized polyethylene dioxythiophene has lower polymerization degree compared with the conventionally synthesized polyethylene dioxythiophene by using an oxidation method. And more surprising is that such low polymerization degree polymerized ethylene dioxythiophene MXene nanosheets have better redox performance, viscosity, solution stability and hydrophobicity which progresses with the degree of oxidation. In turn, the polyethylene dioxythiophene can effectively isolate the poly-dopamine and the reaction of the internal MXene main body with the external oxidation environment, and is used for protecting the poly-dopamine layer. The polymerized dopamine has reversible redox performance in a limited space, which generates mussel-like viscosity, and the stability of MXene is improved to a certain extent, but the polydopamine is directly contacted with the outside, so that the polydopamine is easily influenced by too strong oxidative environment to cause structural damage, the viscosity is lost, and the in-situ ethylene dioxythiophene polymerization can further protect the polydopamine. In particular in an oxidation system, the oligoethylenedioxythiophene is used as an electron donor for the redox reversible reaction of the polydopamine under the condition of contact oxidation environment or under the conventional condition, so that the redox performance of the polydopamine is increased, and the viscosity and the stability which are not easily influenced by the oxidation environment are shown.

Drawings

Fig. 1 is a schematic view of a nanosheet structure.

FIG. 2 is an SEM scanning electron microscopy topography of nanoplates obtained from examples 1-4.

FIG. 3 is an SEM scanning electron microscope of the nanoplate dispersions obtained in examples 1-4, characterizing the self-linking properties.

FIG. 4 shows the chemical test results of antioxidant activity of the nanosheets.

Figure 5 is a graph of the stability results of the nanoplatelets in animal body tissue.

FIG. 6 is a cyclic voltammogram.

Figure 7 is a graph comparing stability of hydrogels with nanoplatelets.

Figure 8 is a graph of the compressive strength results for hydrogels containing nanosheets.

FIG. 9 is a graph showing the results of an experiment on the adhesiveness of a hydrogel containing nanosheets.

Figure 10 is a graph of the compressive strength results for hydrogels containing nanosheets.

FIG. 11 shows the adhesion experiment results of nanosheet cells, wherein a is an MXene-NS nanosheet set and b is an MXene-NSD-PEDOT nanosheet set.

Fig. 12 is a raman spectrum of the nanosheet obtained in example 1.

Fig. 13 is an SEM scanning electron microscopy topography of the nanoplatelets obtained in example 9.

Detailed Description

First, MAX phase ceramics were selectively etched using HF acid to obtain accordion-like MXene, and then MXene was intercalated using Na ions and MXeneN was obtained. Then we continue to intercalate MXene-N with sulfanilic acid diazo to obtain MXene-NS. Polymerizing dopamine on MXene-NS by Michael addition reaction under alkaline and aerobic conditions to obtain MXene-NSD, and then polymerizing PEDOT on MXene-NSD without adding oxidant to obtain MXene-NSD-PEDOT

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof are described in detail below, but the present invention is not to be construed as being limited to the implementable range thereof.

Example 1 preparation of modified MXene materials

1) Mixing 3g of Ti₃AlC₂The powder was slowly dipped into a teflon beaker containing 40mL of aqueous HF and etched at room temperature for 48 hours. The resulting suspension was then transferred to a centrifuge tube and centrifuged. Wet precipitate de-ionizationThe seed water was washed and centrifuged several times. Obtaining the accordion-shaped two-dimensional MXene material Ti which is selectively etched by HF acid₃C₂。

2) After decanting the liquid from the previous step, a small amount of dilute NaOH solution was added dropwise to the centrifuge tube, and the solution was transferred to a beaker and stirred for 2 hours. The product was centrifuged and washed several times with copious amounts of deionized water until the pH of the top liquid was 7-8 to give MXene-N (Na)⁺Intercalated MXene material). Under the structure, Na ions are embedded between MXene sheets, and the MXene sheet distance is enlarged, so that the subsequent sulfonic acid modification reaction is promoted.

3) 10g sulfanilic acid was suspended in 40mL water and cooled to 0-5 ℃. A solution of 9mL of HCl and 30mL of water was pre-cooled to 0-5 ℃ and added slowly to the suspension with stirring under an ice bath. After 15 minutes, 4g of a cold solution of sodium nitrite (18mL) was added dropwise to the suspension and the reaction was complete to give a diazonium salt solution. The diazonium salt solution synthesized as described above was added dropwise to an aqueous MXene-N dispersion with stirring in an ice bath, and the mixture was maintained at 0-5 ℃ for about 4 hours. After the reaction was completed, the mixture was centrifuged and washed several times, and then centrifuged to separate large aggregates and unreacted particles. The supernatant was then lyophilized to MXene-NS powder (intercalated modified MXene nanoplatelets of Na ions and sulfonic acid). The sulfonic acid group is embedded between MXene sheets, the MXene sheet interval is further expanded, complete stripping occurs, and the stripped single-layer or multiple layers of MXene can be observed by a scanning electron microscope, a transmission electron microscope and the like. At the moment, the sulfonic acid group on the surface of MXene has good reactivity and is a precondition for the subsequent reaction of polydopamine and polyethylene dioxythiophene.

4) The MXene-NS powder obtained was dispersed at a concentration of 3mg/mL with 60mL of deionized water, and 15mL of Tris-HCl solution (pH 8.5) was added dropwise to the solution. Meanwhile, 30mg of Dopamine (DA) was added to 15mL of Tris-HCl solution (pH 8.5) and stirred for 15 minutes for preliminary polymerization. And then dripping the DA prepolymerization solution into the MXene-NS solution and stirring for 4 hours to obtain an MXene-NSD nanosheet (the MXene nanosheet which is provided with a polymeric dopamine layer and is modified by intercalation of Na ions and sulfonic acid), wherein the surface of the MXene nanosheet is covered by the nano-scale or submicron-scale polymeric dopamine. MXene-NSD nanosheets were centrifuged and washed several times.

5) 1g of MXene-NSD nanoplatelets were redispersed with 1 l of deionized water, 10g of 3, 4-Ethylenedioxythiophene (EDOT) was dissolved in 100 ml of ethanol; the EDOT solution was then added dropwise to the MXene-NSD solution and stirred at room temperature for 24 hours. Then, the solution is centrifuged, washed for several times and freeze-dried to obtain MXene-NSD-PEDOT nanosheets (MXene nanosheets having a polymeric dopamine layer and a non-oxidized polyethylene dioxythiophene layer, and intercalated and modified Na ions and sulfonic acid) where the non-oxidized polyethylene dioxythiophene layer covers 4) and the surface of the synthesized MXene-NSD.

Example 2 preparation of modified MXene materials

1) 4g of Ti₃AlC₂The powder was slowly dipped into a teflon beaker containing 40mL of aqueous HF and etched at room temperature for 48 hours. The resulting suspension was then transferred to a centrifuge tube and centrifuged. The wet precipitate was washed with deionized water and centrifuged several times.

2) After decanting the liquid from the previous step, a small amount of dilute NaOH solution was added dropwise to the centrifuge tube, and the solution was transferred to a beaker and stirred for 2 hours. The product was centrifuged and washed several times with copious amounts of deionized water until the pH of the top liquid was 7-8 to give MXene-N (Na)⁺Intercalated MXene material).

3) 6.3g sulfanilic acid was suspended in 30mL water and cooled in an ice bath. A solution of 9mL of HCl and 30mL of water was precooled and added slowly to the suspension with stirring under ice bath conditions. After 15 minutes, a cold solution of 2.4g of sodium nitrite (18mL) was added dropwise to the suspension and stirred for 30 minutes to give a diazonium salt solution. The diazonium salt solution synthesized as described above was added dropwise to an aqueous MXene-N dispersion with stirring in an ice bath, and the mixture was maintained at 0-5 ℃ for about 4 hours. After the reaction was completed, the mixture was centrifuged and washed several times, and then centrifuged to separate large aggregates and unreacted particles. The supernatant was then lyophilized to MXene-NS powder (intercalated modified MXene nanoplatelets of Na ions and sulfonic acid).

4) The MXene-NS powder obtained was dispersed at a concentration of 2.5mg/mL with 60mL of deionized water, and 15mL of Tris-HCl solution (pH 8.5) was added dropwise to the solution. Meanwhile, 15mg of Dopamine (DA) was added to 15mL of Tris-HCl solution (pH 8.5) and stirred for 15 minutes for preliminary polymerization. And then dripping the DA prepolymerization solution into the MXene-NS solution and stirring for 4 hours to obtain an MXene-NSD nanosheet (the MXene nanosheet which is provided with a polymeric dopamine layer and is modified by intercalation of Na ions and sulfonic acid), wherein the surface of the MXene nanosheet is covered by the nano-scale or submicron-scale polymeric dopamine. MXene-NSD nanosheets were centrifuged and washed several times.

5) 1g of MXene-NSD nanoplatelets were redispersed with 1 l of deionized water, 5 g of 3, 4-Ethylenedioxythiophene (EDOT) was dissolved in 100 ml of ethanol; the EDOT solution was then added dropwise to the MXene-NSD solution and stirred at room temperature for 24 hours. Then, the solution is centrifuged, washed for several times and freeze-dried to obtain MXene-NSD-PEDOT nanosheets (MXene nanosheets having a polymeric dopamine layer and a non-oxidized polyethylene dioxythiophene layer, and intercalated and modified Na ions and sulfonic acid) where the non-oxidized polyethylene dioxythiophene layer covers 4) and the surface of the synthesized MXene-NSD.

Example 3 preparation of modified MXene materials

1) Mixing 3g of Ti₃AlC₂The powder was slowly dipped into a teflon beaker containing 40mL of aqueous HF and etched at room temperature for 48 hours. The resulting suspension was then transferred to a centrifuge tube and centrifuged. The wet precipitate was washed with deionized water and centrifuged several times. Obtaining the accordion-shaped two-dimensional MXene material Ti which is selectively etched by HF acid₃C₂。

3) 6.3g sulfanilic acid was suspended in 30mL water and cooled to 0-5 ℃. A solution of 9mL of HCl and 30mL of water was pre-cooled to 0-5 ℃ and added slowly to the suspension with stirring under an ice bath. After 15 minutes, a cold solution of 2.4g of sodium nitrite (18mL) was added dropwise to the suspension and stirred for 30 minutes to give a diazonium salt solution. The diazonium salt solution synthesized as described above was added dropwise to an aqueous MXene-N dispersion with stirring in an ice bath, and the mixture was maintained at 0-5 ℃ for about 4 hours. After the reaction was completed, the mixture was centrifuged and washed several times, and then centrifuged at 4000rpm for 1 hour to separate large aggregates and unreacted particles. The supernatant was then lyophilized to MXene-NS powder (intercalated modified MXene nanoplatelets of Na ions and sulfonic acid). The sulfonic acid group is embedded between MXene sheets, the MXene sheet interval is further expanded, complete stripping occurs, and the stripped single-layer or multiple layers of MXene can be observed by a scanning electron microscope, a transmission electron microscope and the like. At the moment, the sulfonic acid group on the surface of MXene has good reactivity and is a precondition for the subsequent reaction of polydopamine and polyethylene dioxythiophene.

4) The MXene-NS powder obtained was dispersed at a concentration of 5mg/mL with 60mL of deionized water, and 15mL of Tris-HCl solution (pH 8.5) was added dropwise to the solution. Meanwhile, 15mg of Dopamine (DA) was added to 15mL of Tris-HCl solution (pH 8.5) and stirred for 15 minutes for preliminary polymerization. And then dripping the DA prepolymerization solution into the MXene-NS solution and stirring for 4 hours to obtain an MXene-NSD nanosheet (the MXene nanosheet which is provided with a polymeric dopamine layer and is modified by intercalation of Na ions and sulfonic acid), wherein the surface of the MXene nanosheet is covered by the nano-scale or submicron-scale polymeric dopamine. MXene-NSD nanosheets were centrifuged and washed several times.

5) 1g of MXene-NSD nanoplatelets were redispersed with 1 l of deionized water and 3g of 3, 4-Ethylenedioxythiophene (EDOT) was dissolved in 100 ml of ethanol; the EDOT solution was then added dropwise to the MXene-NSD solution and stirred at room temperature for 24 hours. Then, the solution is centrifuged, washed for several times and freeze-dried to obtain MXene-NSD-PEDOT nanosheets (MXene nanosheets having a polymeric dopamine layer and a non-oxidized polyethylene dioxythiophene layer, and intercalated and modified Na ions and sulfonic acid) where the non-oxidized polyethylene dioxythiophene layer covers 4) and the surface of the synthesized MXene-NSD.

Example 4 preparation of modified MXene materials

1) Mixing 3g of Ti₃AlC₂The powder was slowly immersed in a solution containing 40mL of aqueous HFIn a teflon beaker and etched at room temperature for 48 hours. The resulting suspension was then transferred to a centrifuge tube and centrifuged. The wet precipitate was washed with deionized water and centrifuged several times. Obtaining the accordion-shaped two-dimensional MXene material Ti which is selectively etched by HF acid₃C₂。

4) The MXene-NS powder obtained was dispersed at a concentration of 3.75mg/mL with 60mL of deionized water, and 15mL of Tris-HCl solution (pH 9) was added dropwise to the solution. Meanwhile, 15mg of Dopamine (DA) was added to 15mL of Tris-HCl solution (pH 8.5) and stirred for 15 minutes for preliminary polymerization. And then dripping the DA prepolymerization solution into the MXene-NS solution and stirring for 4 hours to obtain an MXene-NSD nanosheet (the MXene nanosheet which is provided with a polymeric dopamine layer and is modified by intercalation of Na ions and sulfonic acid), wherein the surface of the MXene nanosheet is covered by the nano-scale or submicron-scale polymeric dopamine. MXene-NSD nanosheets were centrifuged and washed several times.

5) 1g of MXene-NSD nanoplatelets were redispersed with 1 l of deionized water, and 15 g of 3, 4-Ethylenedioxythiophene (EDOT) was dissolved in 100 ml of ethanol; the EDOT solution was then added dropwise to the MXene-NSD solution and stirred at room temperature for 24 hours. Then, the solution is centrifuged, washed for several times and freeze-dried to obtain MXene-NSD-PEDOT nanosheets (MXene nanosheets having a polymeric dopamine layer and a non-oxidized polyethylene dioxythiophene layer, and intercalated and modified Na ions and sulfonic acid) where the non-oxidized polyethylene dioxythiophene layer covers 4) and the surface of the synthesized MXene-NSD.

Example 5 scanning Electron microscopy

The MXene-NSD-PEDOT nanosheets obtained in examples 1-4 were subjected to scanning electron microscope detection, and the experimental results are shown in FIGS. 2-3.

Fig. 2 shows the finally synthesized MXene-NSD-PEDOT nanosheet, and the nanosheet has a three-layer structure which is obvious from the cross section, wherein the outer layer is a non-oxidized polyethylene dioxythiophene layer, and the inner layer is MXene-NSD. It can be seen that the synthetic polymeric dopamine layer is relatively thin, since reversible redox on a nano or sub-micron scale can increase the viscosity of the material, while a thicker layer of non-oxidized polyethylene dioxythiophene can provide sufficient electrons to protect the internal structure.

FIG. 3 shows the surface appearance of the aqueous solution containing the finally synthesized MXene-NSD-PEDOT nanosheets when the aqueous solution is dried in a natural state at room temperature, and the MXene-NSD-PEDOT nanosheets form large-area covalent connection through oxidative polymerization. At the same time, fine fold protrusions are visible on the surface, which promotes cell adhesion and spreading.

Example 6 preparation of polyethylene dioxythiophene of different polymerization degree and Raman Spectroscopy detection

Synthesizing the polymerized ethylene dioxythiophene by an oxidative catalyst chemical synthesis method, specifically preparing 160 mu L of 3, 4-ethylEthylenedioxythiophene (EDOT) was dissolved in 10mL ethanol and FeCl was added₃After the catalyst was washed and dried, comparative PEDOT nanoparticles were obtained. The raman spectrum of the nanosheets obtained in example 1 and the comparative example were examined by raman spectroscopy. The results of the Raman spectroscopy are shown in FIG. 12.

The raman spectrum results show that the polymerized ethylenedioxythiophene synthesized in examples 1-4 of the present invention has a lower degree of polymerization than the polymerized ethylenedioxythiophene conventionally synthesized using an oxidation process.

The change of characteristic functional group peaks of the nanosheets at different oxidation stages is observed through Raman spectroscopy, and the result shows that the MXene disclosed by the invention is different from the film forming capability of MXene in the prior art, a stable structure connected by covalent bonds is formed between MXene materials, and the MXene in the prior art is realized by re-stacking of the sheet layers and Van der Waals force between the sheet layers, so that the MXene disclosed by the invention has better film forming stability in water.

Example 7MXene nanosheet Oxidation resistance test

The experimental method comprises the following steps: MXene, MXene-NS and MXene-NSD-PEDOT were dispersed in deionized water, and left open in air at 25 ℃ to observe the state. The result is shown in figure 4, and the experimental result shows that MXene-NSD-PEDOT has better antioxidant performance compared with MXene and MXene-NS. It remained intact after 4 weeks of standing, while MXene and MXene-NS showed oxidation for about one and three days, respectively. The dynamic equilibrium system of the PDA/PEDOT is that Ti is added into the polydopamine layer and the polyethylene dioxythiophene layer in the MXene nanosheet MXene-NSD-PEDOT of the invention₃C₂The crystals are separated from the external environment and induce redox activity by conversion of catechol to quinone: 0.34 unit electron flow from PEDOT to Ti₃C₂And reduces the oxidation of catechol group in PDA, therefore, the present invention shows relatively high antioxidant activity.

Example 8 in vivo implantation experiment in mice

The experimental method comprises the following steps: the mice were anesthetized, the MXene-NSD-PEDOT nanosheets were dispersed in physiological saline at a concentration of 1mg/mL, 0.15mL of the MXene-NSD-PEDOT nanosheet dispersion was injected into the outer thigh of the mice by a syringe, and after 6 weeks, the thigh of the mice was fixedly sectioned and observed by hematoxylin-eosin staining.

The experimental results are shown in fig. 5, and it was confirmed that within 6 weeks, the material and tissue boundary was clear, no significant tissue diffusion occurred, the tissue near the material was healthy, no oxidative stress occurred, and a certain amount of new blood vessels were observed. The material provided by the invention has better stability.

Example 7 Cyclic voltammetry curves and degradation experiments

The redox behavior of MXene-NSD-PEDOT nanoplates was studied using cyclic voltammetry (FIG. 6). Respectively detecting MXene-NSD-PEDOT nanosheets (namely nanosheets with low PEDOT polymerization degree) prepared by the method without adding FeCl3, wherein an oxidation peak at 0.13V corresponds to the conversion of catechol to quinone; the reduction peak at-0.41V corresponds to the conversion of quinone to catechol. An accelerated experiment was performed, i.e. an oxidizing environment was provided. With the continuous further polymerization of PEDOT on the surface of the nanosheet with low degree of PEDOT polymerization under the condition of providing an oxidizing environment, the obtained highly polymerized nanosheet shows an additional peak value at 0.41V, which corresponds to Ti₃C₂Oxidation of the crystal lattice. The acceleration experiment proves that: as the degree of PEDOT polymerization can increase with time in vivo, distortion of the CV curve and a sharp rise in impedance can be observed. This indicates that as the time span of MXene-NSD-PEDOT nanoplatelets in vivo increases, the PEDOT layer will continue to polymerize until a complete state-the electron transfer capability of the nanoplatelets will reach their peak. From then on, Ti₃C₂The crystals will participate in the oxidation process: ROS will continuously consume Ti₃C₂Electrons accumulate and gradually degrade the nanosheet structure. This property allows for nonlinear degradation of the nanoplatelets-by accelerated oxidative decomposition-and better self-removal capacity later in function.

Example 10 detection of preparation Properties of hydrogel containing MXene nanosheet

MXene-NS gel, MXene-NSD-PEDOT gel and blank hydrogel (PAM) without MXene nanosheets are prepared by mixing MXene-NSene-PEDOT or intermediate MXene-NS obtained in example 1 of the invention in polyacrylamide hydrogel in a ratio of 1mg of MXene nanosheet to 1mL of hydrogel.

The gel stability experiment result is shown in figure 7, and the PAM, MXene-NS gel and MXene-NSD-PEDOT gel are sequentially arranged from left to right, so that no agglomeration phenomenon occurs in the MXene-NSD-PEDOT gel, and obvious agglomeration phenomenon occurs in the other two hydrogels.

The tensile strength of PAM, MXene-NS gel and MXene-NSD-PEDOT gel is respectively detected, the experimental result is shown in figure 8, the result shows that the MXene-NSD-PEDOT gel has the highest tensile strength, and compared with MXene-NS, MXene-NSD-PEDOT brings remarkable improvement to the tensile strength of hydrogel.

PAM, MXene-NS gel, MXene-NSD-PEDOT gel were tested for viscosity with polyethylene (polythene) and Stainless steel (Stainless steel), respectively, to assess viscosity. The results are shown in fig. 9 and show that MXene-NSD-PEDOT gel shows the highest viscosity on both polyethylene and stainless steel surfaces. Compared with MXene-NS, MXene-NSD-PEDOT brings a remarkable improvement to the viscosity of the hydrogel.

The impedance values of PAM, MXene-NS gel, MXene-NSD-PEDOT gel and polyethylene (polythene) at different frequencies are respectively detected, the experimental result is shown in figure 10, and the results show that the MXene-NSD-PEDOT gel shows higher conductivity at different frequencies.

Example 11 cell adhesion test

The nano-sheets MXene-NS and MXene-NSD-PEDOT are respectively molded on a cover glass sheet in a grid state, rat Schwann cells are inoculated on the grid state, two-day culture is carried out, and the cell state is observed.

The experimental result is shown in figure 11, compared with the MXene-NS group, the cells cultured on the MXene-NSD-PEDOT have better discrimination, and the combination and related physiological response of the cells to the MXene-NSD-PEDOT nanosheet are better than those of the MXene-NS nanosheet as shown in figure 11. Schwann cells are distributed mainly around the processes of neurons in the peripheral nervous system, are sheath cells of peripheral nerve fibers, and play an important role in peripheral nerve regeneration. The experimental results show that the nanosheets of the present invention can further increase adhesion of neural cells.

Example 12 preparation of modified MXene materials

The same procedure as in example 1 was followed, except that Ti was used₃AlC₂Is replaced by Ti₂AlC。

The nanomaterial obtained in example 9 and the dispersion of the nanomaterial described above were observed by scanning electron microscopy, and self-bonding properties and a three-layer structure similar to those of the nanomaterial described in example 1 were observed as shown in fig. 13.

Example 13 preparation of modified MXene materials

The same procedure as in example 1 was followed, except that Ti was used₃AlC₂And replaced with Ta4AlC 3.

Example 14 preparation of modified MXene materials

The same procedure as in example 1 was followed, except that Ti was used₃AlC₂Is replaced by V₂AlC。

Example 15 preparation of modified MXene materials

The same procedure as in example 1 was followed, except that Ti was used₃AlC₂Replaced by Mo₂AlC。

Claims

1. The surface-modified MXene nanosheet is characterized in that the MXene nanosheet is provided with Na ions and sulfonic acid intercalation, and meanwhile, the surface of the MXene nanosheet is also provided with a polydopamine layer and a polyethylene dioxythiophene layer;

preferably, the polydopamine layer and the polyethylene dioxythiophene layer are arranged in sequence;

more preferably, the poly dopamine layer is polymerized on the surface of the MXene nano sheet with Na ions and sulfonic acid intercalation, and then the polyethylene dioxythiophene layer is polymerized in situ.

2. Surface-modified MXene nanosheets according to claim 1, wherein the layer of polyethylene dioxythiophene is obtained by in situ polymerization of ethylene dioxythiophene;

preferably, no catalyst with oxidation is added in the polymerization process of the polyethylene dioxythiophene layer;

more preferably, the catalyst is a ferric ion catalyst.

3. The surface-modified MXene nanoplatelets of claim 1 wherein the MXene nanoplatelets have a substrate selected from the group consisting of Ti₃C₂、Ti₂C、Ta₄C₃、Nb₂C、V₂C、Mo₂C。

4. A process for the preparation of surface-modified MXene nanoplatelets according to any of claims 1-3, characterized in that it comprises the following steps:

5. The method according to claim 4, wherein the two-dimensional MXene nano-substrate in step 1) is selected from Ti₃C₂、Ti₂C、Ta₄C₃、Nb₂C、V₂C or Mo₂One or more of C;

preferably, the two-dimensional MXene nano substrate in the step 1) is obtained by selectively etching MAX phase ceramic through HF acid;

preferably, the sulfanilic acid diazonium salt in step 1) is obtained by reacting sulfanilic acid, hydrochloric acid and sodium nitrite;

more preferably, the MAX phase ceramic is selected from Ti₃AlC₂、Ti₂AlC、Nb₂AlC、V₂AlC、Mo₂One or more combinations of alcs.

6. The preparation method according to claim 4, wherein the mass ratio of the dopamine to the intercalated modified MXene nanosheets of Na ions and sulfonic acid in step 2) is 1: 5-20.

7. The method according to claim 4, wherein the ethylene dioxythiophene raw material in step 3) is selected from 3, 4-ethylene dioxythiophene;

preferably, the ratio of the raw material of ethylene dioxythiophene to the intercalated modified MXene nanosheets having a polymerized dopamine layer and Na ions and sulfonic acid in step 3) is 0.1 g to 15 g of raw material of ethylene dioxythiophene per 1g of the intercalated modified MXene nanosheets having a polymerized dopamine layer and Na ions and sulfonic acid;

preferably, wherein no oxidant is added in the step 3) reaction.

8. Use of the surface-modified MXene nanoplatelets according to any one of claims 1-3 or MXene nanoplatelets obtained by the method of preparation according to any one of claims 4-7 as electrode modification material, cell repair material for peripheral nerves, lead wire for nerve electrodes, site for central nerve electrodes;

preferably, the electrode modification material is selected from modification materials for electrodes for nerves, more preferably, for electrode modification of central nerves and peripheral nerves.

9. A bioelectrode, the surface of which has the surface-modified MXene nanosheet of any one of claims 1 to 3 or the MXene nanosheet obtained by the production method of any one of claims 4 to 7 as an electrode surface modification material;

10. A dispersion comprising the surface-modified MXene nanoplatelets of any one of claims 1 to 3 or the MXene nanoplatelets obtained by the production method of any one of claims 4 to 7, and a dispersion matrix,

preferably, the dispersion matrix is selected from the group consisting of hydrogels, elastomers, solvents;

more preferably, the hydrogel is selected from at least one of polyacrylamide hydrogel, polyvinyl alcohol hydrogel, hyaluronic acid derivatives, collagen, gelatin, fibronectin, fibrinogen, alginate, chitosan; the solvent is selected from aqueous solution or organic solvent;

preferably, the concentration of the surface-modified MXene nanosheets in the dispersion is 0.1-10 mg/mL.