WO2019095751A1

WO2019095751A1 - Cellulose/two-dimensional layered material composite hydrogel and preparation method therefor

Info

Publication number: WO2019095751A1
Application number: PCT/CN2018/100240
Authority: WO
Inventors: 张晗; 邢晨阳; 陈世优
Original assignee: 深圳大学
Priority date: 2017-11-15
Filing date: 2018-08-13
Publication date: 2019-05-23
Also published as: CN107973920A

Abstract

The present invention provides a cellulose/two-dimensional layered material composite hydrogel. The composite hydrogel comprises a cellulose three-dimensional network structure, and a two-dimensional material supported in the cellulose three-dimensional network structure. The two-dimensional layered material is a two-dimensional transition metal carbide, nitride, or carbonitride. The two-dimensional layered material can be stably supported in the composite hydrogel system and is not easy to agglomerate. The composite hydrogel is compatible with biological fluids, completely biodegradable, achieves strong biosafety, and can be used in the field of biomedicine. The present invention further provides a preparation method for the composite hydrogel.

Description

Cellulose/two-dimensional layer material composite hydrogel and preparation method thereof

This application claims priority to Chinese Patent Application filed on November 15, 2017, the Chinese Patent Office, Application No. 201711128428.4, entitled "A Cellulose/Two-Dimensional Layered Material Composite Hydrogel and Its Preparation Method" The content of the above-mentioned prior application is incorporated herein by reference.

Technical field

The invention belongs to the field of hydrogel preparation, and in particular relates to a cellulose/two-dimensional layer material composite hydrogel and a preparation method thereof.

Background technique

Two-dimensional transition metal carbide or carbonitride (MXenes) is a new two-dimensional material discovered this year. It has high specific surface area, high electrical conductivity, and flexible composition. The smallest nano-layer The advantages of thick and controllable have great potential in the fields of energy storage, electromagnetic shielding, water treatment, gas/biosensing and photoelectrochemical catalysis. To emphasize its two-dimensional structure similar to graphene, this class of compounds is collectively named MXenes.

In the field of biomedicine, MXenes exhibits excellent photothermal conversion efficiency under near-infrared light (for example, 808 nm), showing great advantages in photothermal therapy; however, MXenes is not sufficiently dispersible in biological fluids. When sedimentation occurs, there are obvious regional differences in the photothermal effect. Moreover, the structure of MXenes-based materials is too single, and the stability of MXenes in them is poor, and it is easy to be detached, which cannot meet the targeting and persistence required for tumor treatment. Therefore, it is necessary to expand the form of MXenes in the field of biomedicine.

Cellulose is the most abundant renewable resource on the earth. It has the advantages of complete biocompatibility and complete biodegradability. However, due to its high crystallinity and intramolecular/intermolecular hydrogen bonding, cellulose is difficult to dissolve and refractory. This has made it difficult to form and shape, which greatly limits the development of cellulose in biomedical materials.

Summary of the invention

In view of the above, the present invention provides a cellulose/two-dimensional layered material composite hydrogel, which has high stability in the composite hydrogel, and the composite hydrogel is in a biological fluid. It has good dispersibility, exhibits high photothermal conversion efficiency, has excellent biocompatibility, biosafety and other excellent properties, and has good mechanical strength, and is expected to be applied in the field of biomedicine.

In a first aspect, the present invention provides a cellulose/two-dimensional layered material composite hydrogel comprising a three-dimensional network structure of cellulose and two-dimensionally supported in the three-dimensional network structure of the cellulose. A layered material that is a two-dimensional transition metal carbide, nitride or carbonitride (MXenes).

Wherein, the chemical formula of the two-dimensional layered material (MXenes) is M _n+1 X _n T _x , wherein M is a transition metal element, X is a carbon element and/or a nitrogen element, and n is an integer of 1-3. T _x represents a surface group, and T may be selected from at least one of O ²⁻ , OH ⁻ , F ⁻ and NH ₄ ⁺ .

Further, the two-dimensional layered material is Ti ₃ C ₂ T _x , Ti ₂ CT _x , (Ti _0.5 , Nb _0.5 ) ₂ CT _x , (V _0.5 , Cr _0.5 ) ₃ C ₂ T _x , Ta ₄ C ₃ T _x , V ₂ CT _x , Nb ₂ CT _x , Nb ₄ C ₃ T _x , (Nb _0.8 , Ti _0.2 ) ₄ C ₃ T _x , (Nb _0.8 , Zr _0.2 ) ₄ C ₃ T _x , Ti ₃ CNT One or more of _x , Mo ₂ TiC ₂ T _x , Mo ₂ Ti ₂ C ₃ T _x and Cr ₂ TiC ₂ T _x .

In the present invention, the two-dimensional layered material may be a detached or unstripped MXenes material. Preferably, the two-dimensional layered material is a two-dimensional layered material after liquid phase stripping, and the thickness thereof is on the order of nanometers.

Preferably, the two-dimensional layered material has a thickness of 6-10 nm. At this time, the two-dimensional layered material may be referred to as "two-dimensional material nanosheet". A two-dimensional layered material of nanometer thickness can be more firmly loaded into the cellulose three-dimensional network structure.

Wherein, the number of layers of the two-dimensional layered material is 1-20 layers. More preferably, it is 2-10 layers.

Preferably, the two-dimensional layered material has a transverse dimension of from 60 to 200 nm. The lateral dimension refers to the length or width of the two-dimensional layered material.

The interaction between the two-dimensional layered material MXenes is weak, and the pure MXenes gel cannot be built by self-assembly behavior. In the present invention, the two-dimensional layered material MXenes is wound by the three-dimensional network structure formed by the cellulose molecules. In the cellulose three-dimensional network structure, a two-dimensional layered material MXenes is loaded into the system to form a cellulose/two-dimensional layered material composite hydrogel. Among them, the composite hydrogel significantly improves the dispersibility of the two-dimensional layered material MXenes and prevents agglomeration between MXenes.

Wherein, the cellulose three-dimensional network structure comprises a three-dimensional network structure in which cellulose or a cellulose derivative itself is connected, or a three-dimensional network structure formed by a cellulose and/or a cellulose derivative through a crosslinking agent.

Wherein the cellulose derivative comprises cellulose modified with at least one of graphene oxide, chitosan, cyclodextrin and gelatin, or carboxylated, silylated cellulose.

Preferably, the crosslinking agent includes at least one of epichlorohydrin and isocyanate, but is not limited thereto.

Wherein, the cellulose three-dimensional network structure has a pore structure with a pore diameter of 40-130 μm. Preferably, the pore structure has a pore diameter of 50 to 80 μm.

Wherein, the composite hydrogel has a water content of 85%-98%. The composite hydrogel has a large water content and is easily dispersed in an aqueous solution or a biological body fluid, and has excellent compatibility with body fluids, which can improve adhesion of the two-dimensional layered material to living cells and tissues. .

Wherein the mass ratio of the cellulose in the three-dimensional network structure of the cellulose to the two-dimensional layered material is 100: (0.0001 to 50), preferably 100: (0.001 to 10), further preferably 100: (0.001) ～5), more preferably 100:0.05.

In an embodiment of the invention, the three-dimensional network structure of cellulose is a three-dimensional network structure in which cellulose molecules and a crosslinking agent are crosslinked.

Wherein, the mass ratio of the cellulose to the crosslinking agent in the three-dimensional network structure of the cellulose is 100: (1.372-13.71). It is preferably 100: (4.116 to 13.71), further preferably 100: (4.116 to 6.86).

Wherein the cellulose is one or more of lignocellulose, bamboo cellulose, wood cellulose pulp, cotton cellulose, microcrystalline cellulose, hydroxyethyl cellulose, carboxymethyl cellulose.

The composite hydrogel of the cellulose/two-dimensional layered material provided by the first aspect of the invention has a three-dimensional network structure of cellulose as a carrier, and the three-dimensional network structure stably supports a two-dimensional layered material, thereby improving two-dimensional The dispersibility of the layered material prevents agglomeration of the two-dimensional layered material, expanding the product form of the two-dimensional layered material. The composite hydrogel of the cellulose/two-dimensional layered material has good dispersibility in biological fluid, exhibits excellent characteristics of high photothermal conversion efficiency, complete biocompatibility, biosafety, and the like, and has good properties. The mechanical strength is expected to be applied in the field of biomedicine, especially in the field of cancer treatment.

In a second aspect, the present invention provides a method for preparing a cellulose/two-dimensional layered material composite hydrogel, comprising the following steps:

(1) providing a two-dimensional layered material, the two-dimensional layered material being a two-dimensional transition metal carbide, nitride or carbonitride;

(2) preparing a mixed solvent containing a strong base, urea and water, and pre-cooling, adding the cellulose powder to the pre-cooled mixed solvent, and vigorously stirring to obtain a cellulose solution;

(3) mixing the two-dimensional layered material and the crosslinking agent with the cellulose solution under high-speed stirring, and after ultrasonic treatment, crosslinking reaction at 65-90 ° C for 0.5-2 hours, Cross-linking reactant;

(4) The cellulose regenerant is added to the cross-linking reaction solution for 30-60 minutes, and then the regenerated cross-linking reactant is placed in water for dialysis to obtain a cellulose/two-dimensional layered material composite hydrogel.

The cellulose/two-dimensional layered material composite hydrogel prepared by the above method comprises a cellulose three-dimensional network structure crosslinked by cellulose and a crosslinking agent, and further comprises two supported in the three-dimensional network structure of the cellulose. Dimensional layered material. Further, the surface of the two-dimensional layered material is covered by the cellulose three-dimensional network structure.

Wherein, in the step (2), the mixed solvent is precooled to -15 to -5 °C. This facilitates better dissolution of the cellulose powder. Preferably, the mixed solvent is pre-cooled to -12 °C.

Optionally, the cellulose powder has a particle size of from 10 to 30 microns.

Wherein, in the step (2), the rotational speed of the vigorous stirring is 7000 to 10000 rpm, and the time of the vigorous stirring is 1 to 3 minutes.

In the step (3), the high-speed stirring rotation speed is 7000 to 10000 rpm, and the high-speed stirring time is 1 to 3 minutes. The stirring speed and the stirring time of the vigorous stirring and the high-speed stirring may be the same or different.

In the step (3), the crosslinking agent is preferably a substance which is not completely hydrophobic. The crosslinking agent carries at least one of an epoxy group (COC) and an isocyanate group (NCO), such that the functional groups in the crosslinking agent can be combined with the cellulose molecular chain -OH cross-linking reaction occurs.

Preferably, the crosslinking agent is selected from one or more of epichlorohydrin and isocyanate, but is not limited thereto. Further preferably, the crosslinking agent is epichlorohydrin. At this time, the hydroxyl functional group (-OH) on the cellulose molecular chain undergoes a nucleophilic reaction with the carbon atom on the epoxy functional group (C-O-C) in the epichlorohydrin, and crosslinks to form a hydrogel system.

Wherein, in the step (3), the ultrasonic treatment has a power of 300-500 W and a time of 10 to 30 minutes.

Preferably, in the step (3), the temperature of the crosslinking reaction is 70 to 85 °C. For example, it can be 72, 75, 78, 80 or 82 °C.

Wherein, in the step (4), the cellulose regeneration liquid is a dilute sulfuric acid solution having a mass fraction of 5% to 10%.

Preferably, the volume ratio of the crosslinking reactant to the dilute sulfuric acid solution is 1: (2-3). Further, the volume of the dilute sulfuric acid solution used is 10 to 15 mL. Wherein, the cross-linking reactant is a hydrogel of cellulose/crosslinking agent/two-dimensional layered material/sodium hydroxide/urea.

Wherein, in step (4), the dialysis time is 3-7 days. The purpose of dialysis is mainly to remove strong alkali, urea and regenerant.

Wherein, in the step (2), the mass concentration of the strong base is 5-15%, and the mass concentration of urea is 10-15%.

Wherein the strong base is one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide.

In the step (2), the mass ratio of the mixed solvent to the cellulose in the cellulose solution is 100: (1 to 4).

Preferably, the volume ratio of the volume of the cellulose solution to the crosslinking agent is 100: (0.2-2.0).

Preferably, the mass ratio of the volume of the cellulose solution to the crosslinking agent is 100: (0.236-2.36) mL/g.

Preferably, the mass ratio of the mass of the cellulose solution to the crosslinking agent is 100: (0.212-2.12).

Wherein, the mass ratio of the cellulose to the two-dimensional transition metal carbide nanosheet is 100: (0.0001 to 50). For example, it may be 100:0.01, 100:0.03, 100:0.05, 100:0.1, 100:0.5, 100:1, 100:5, 100:10. It is preferably 100: (0.001 to 10), more preferably 100: (0.001 to 5), still more preferably 100: 0.05.

The two-dimensional layered material MXenes can generate heat under the illumination of near-infrared light (such as 808 nm), and the temperature can be raised from room temperature to up to 150 ° C, and can be killed by regulating its content in the composite hydrogel. The required temperature of dead cancer cells (such as 43-60 ° C), compared with other common photothermal reagents (such as nano gold, nano Pd, CuS and porphyrin), the two-dimensional layered material MXenes has higher light Thermal conversion efficiency as well as better biocompatibility and biosafety.

Optionally, the mass ratio of the cellulose to the two-dimensional layered material is 100: (0.0001-0.01). At this time, the composite hydrogel can be irradiated with an 808 nm laser having an irradiation power of 0.5/cm ² , and the photothermal equilibrium temperature reaches 50.2-60.2 ° C, so that the composite hydrogel can have an irradiation power of 1.0/ Under the illumination of 808 nm laser of cm ² , the photothermal equilibrium temperature reached 55.4-73.1 °C. It can be seen that when the two-dimensional layered material of lower quality is contained, the composite hydrogel can be given a good photothermal effect of killing tumor cells.

In the present invention, the two-dimensional layered material MXenes may be an unstripped MXenes bulk material, and may directly perform the A element (such as the Al element) in the layered precursor MAX (chemical formula M _n+1 AX _n ). Acid etching, high temperature etching or vapor phase etching. The two-dimensional layered material MXenes may also be obtained by further stripping the MXenes bulk material.

Preferably, the two-dimensional layered material has a thickness of 6-10 nm. At this time, the two-dimensional layered material may be referred to as a "two-dimensional material nanosheet."

Preferably, the number of layers of the two-dimensional layered material is from 1 to 20 layers, further preferably from 2 to 10 layers.

In the present invention, the preparation method of the two-dimensional material nanosheet is not limited, and may be prepared in the following manner:

(a) slowly mixing hydrofluoric acid and a layered precursor MAX (chemical formula M _n+1 AX _n ), and etching away the A site element in the layered precursor MAX to obtain an etching mixture;

After centrifuging the etching mixture, washing and collecting a solid precipitate, and vacuum drying the solid precipitate to obtain a two-dimensional layered material body (ie, MXenes);

(b) mixing the main body of the two-dimensional layered material and the organic solvent, grinding the mixture, and adding the organic solvent to the mixture obtained by polishing to obtain a dispersion; and performing the probe at a power of 1000 to 1400 W Ultrasonic 30-60 hours, the solution obtained after ultrasonication is subjected to low speed centrifugation, the supernatant is collected, and the supernatant is centrifuged at a high speed, and a solid precipitate is collected, and the solid precipitate is vacuum dried to obtain the two-dimensional material. Nanosheets.

Optionally, the ratio of the mass of the two-dimensional layered material body to the total volume of the organic solvent is (0.25-1) mg/mL.

Alternatively, the milling time is 20-60 min and the milling is carried out under anaerobic conditions.

The surface energy of the organic solvent matches the surface energy of the two-dimensional layered material body, and there is a certain interaction between the two to balance the energy required to peel off the two-dimensional layered material body. Wherein the organic solvent is selected from the group consisting of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-cyclohexyl-2-pyrrolidone (CHP), and One or more of isopropyl alcohol (IPA), but is not limited thereto.

Preferably, the low speed centrifugation has a rotational speed of 5000-8000 rpm and a time of 20-40 min. Further preferably, the low speed centrifugal speed is 6000-8000 rpm.

Preferably, the high speed centrifugation has a rotational speed of 15000-18000 rpm for a period of 30-60 min. Further preferably, the high speed centrifugation is 16000-18000 rpm.

Preferably, the vacuum drying has a drying temperature of 50-80 ° C and a drying time of 12-24 h.

The formation mechanism of the cellulose/two-dimensional layered material composite hydrogel provided by the invention is as follows: 1) Firstly, the cellulose is dissolved by using a low-temperature alkaline mixed solvent of sodium hydroxide, urea and water to dissolve the cellulose. The hydrogen bond network between the chains is gradually opened to form the sodium and hydroxide ions of the hydrate, forming a new hydrogen bond network with the molecular chain of the cellulose, and the urea molecule hydrate prevents the self of the cellulose molecular chain. Associating, finally, the cellulose molecular chain is dissolved in an aqueous solution in the form of a tubular clathrate, which overcomes the high crystallinity and intramolecular/intermolecular strong hydrogen bonding of cellulose which is difficult to dissolve in ordinary water including solvent Solvent problem. In addition, the alkaline solution also helps to improve the stability of the two-dimensional transition metal carbide nanosheet and protect the two-dimensional transition metal carbide from oxidation. 2) When the aqueous cellulose solution is mixed with the two-dimensional layered material and the crosslinking agent under high-speed stirring, after ultrasonication, the cellulose molecular chain and the crosslinking agent undergo nucleophilic reaction at a certain temperature, and the two-dimensional layered material is simultaneously The two-layered layered material is placed in an extremely stable state to form a three-dimensional network of cellulose/crosslinking agent/two-dimensional layered material/sodium hydroxide/urea hydrogel. 3) The cellulose/crosslinking agent/two-dimensional layered material/sodium hydroxide/urea hydrogel is regenerated after being immersed in a dilute sulfuric acid solution, that is, the cellulose molecular chain is precipitated, The hydrogel after the regeneration is easily taken out, and after immersion in water, sodium hydroxide and urea can be removed, and finally a composite hydrogel of cellulose/two-dimensional layered material is obtained.

In the composite hydrogel of the cellulose/two-dimensional layered material, the two-dimensional layered material is stably supported in a three-dimensional network structure in which cellulose and a crosslinking agent are crosslinked, due to the blocking of the cellulose macromolecular chain, The two-dimensional layered material is in an extremely stable state, and agglomeration sedimentation is less likely to occur, so that the composite hydrogel has a relatively uniform and stable photothermal effect, and the photothermal effect has almost no regional difference. Secondly, the composite hydrogel contains sufficient moisture to be easily dispersed in an aqueous solution or a biological body fluid, and has excellent compatibility with body fluids, which can improve the two-dimensional layered material and biological cells and tissues. Adhesion. Further, due to the gelation property of the composite hydrogel, when used as an anticancer therapeutic system, it can be directly injected into a tumor site by means of "intratumoral injection". In addition, the cellulose-based gel framework of the composite hydrogel can also fix other hydrophilic anticancer drugs, and provide multi-mode comprehensive treatment for targeted therapy, photothermal therapy and chemotherapy of tumor cells. . Finally, since the cellulose and the two-dimensional layered material are both biocompatible materials, the composite hydrogel also has excellent properties such as complete biocompatibility and biosafety.

The preparation method of the cellulose/two-dimensional layer material composite hydrogel provided by the second aspect of the invention has the advantages of simple process, green environmental protection, excellent performance and stable uniformity.

The advantages of the embodiments of the present invention will be set forth in part in the description which follows.

DRAWINGS

1 is a transmission electron microscope (TEM) photograph of a Ti ₃ C ₂ T _x nanosheet used in an embodiment of the present invention: (a) a low resolution photograph (scale is 100 nm); (b) a high resolution topography photograph (the scale is 20 nm); (c) Selected area electron diffraction photographs.

2 is a macro photograph of the aqueous solution of Ti ₃ C ₂ T _x nanosheets provided in the present invention at room temperature for 24 hours before (a), after (b), and the cellulose hydrogel of Comparative Example 4 and Examples Macroscopic photo (c) of a composite hydrogel of cellulose/Ti ₃ C ₂ T _x nanosheets in 2, 4, 6 and 7.

Figure 3 is a scanning electron microscope (SEM) photograph of the aerogel obtained after freeze-drying of a hydrogel: (a) aerogel corresponding to cellulose hydrogel (Comparative Example 4); (b) Cellulose/Ti A composite hydrogel of ₃ C ₂ T _x nanosheets (Example 4) corresponds to an aerogel.

Detailed ways

The following is a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It is the scope of protection of the present invention.

The embodiments of the present invention are further described below in various embodiments. The embodiments of the present invention are not limited to the following specific embodiments. Changes can be implemented as appropriate within the scope of the invariable primary rights.

Unless otherwise stated, the raw materials and other chemical reagents used in the examples of the present invention are commercially available products.

Example 1

A method for preparing a composite hydrogel of cellulose/small layer Ti ₃ C ₂ T _x nanosheets, comprising:

Step (1). Preparation of a small layer of Ti ₃ C ₂ T _x nanosheet by liquid phase stripping method, the specific steps are as follows:

1-a): Preparation of a multi-layered Ti ₃ C ₂ T _x material by hydrofluoric acid etching, the specific operation is as follows: powdered ternary layered nitride Ti ₃ AlC ₂ and hydrofluoric acid aqueous solution (quality of HF) The fraction is 10% to 40%) and the reaction is carried out by adding it to a polyethylene plastic beaker at a solid content ratio of 10 g/100 mL. The ternary layered nitride Ti ₃ C ₂ T _x needs to be slowly added to the hydrofluoric acid aqueous solution, and the slow addition time is 10 minutes to 30 minutes. After the addition, the reaction is carried out at the reaction temperature for 12 hours to 24 hours. After the end of the reaction, the resulting etching mixture was centrifuged at 17,000 rpm for 35 minutes, and a solid precipitate was collected and washed repeatedly with absolute ethanol and deionized water until the solution was neutral. The precipitate obtained after washing is a binary multilayer Ti ₃ C ₂ T _x ; finally, the obtained precipitate is dried under vacuum for 48 to 64 hours, and is used;

1-b): The above two-dimensional multilayer Ti ₃ C ₂ T _x MXene material and N-methylpyrrolidone (NMP) were added to an agate mortar at a solid content ratio of 500 mg/10 mL for mechanical grinding for 30 minutes. The milled composite was transferred to a 100 mL reaction flask, and 90 mL of NMP was added to obtain a dispersion, and the solid content of the two-dimensional multilayer Ti ₃ C ₂ T _x MXene material in the total NMP was 5 mg/mL.

1-c): The above dispersion was subjected to probe ultrasonication at an ultrasonic power of 600 W for 50 hours to obtain a solution containing two-dimensionally small Ti ₃ C ₂ T _x nanosheets, that is, a small layer of Ti ₃ C ₂ T _x A mixed solution of nanosheets and NMP is used.

1-d): The above-mentioned small layer Ti ₃ C ₂ T _x nanosheet solution was centrifuged at a rotation speed of 7000 rpm for 25 minutes, and 3/4 of the supernatant was slowly taken out.

1-e): The supernatant was then subjected to high-speed centrifugation at a rotational speed of 17,000 rpm for 35 minutes, and the supernatant was slowly decanted to collect a small layer of Ti ₃ C ₂ T _x nanosheet solid.

1-f): drying the above-mentioned small layer Ti ₃ C ₂ T _x nanosheet solid in a vacuum drying oven for 20 hours at a temperature of 75 ° C, finally obtaining a dried small layer of Ti ₃ C ₂ T _x nanosheet solid, ready for use .

Step (2). Preparing an alkaline aqueous solution of transparent and uniform cellulose, the specific steps of which are as follows:

2-a): adding sodium hydroxide, urea and deionized water to a 200 mL beaker at a mass ratio of 7%/12%/81% to obtain a mixed solvent, wherein the mass of deionized water is 81.0 g. That is, the total volume of the mixed solvent was 100 mL; the mixed solvent was pre-cooled for 30 minutes, and the temperature was brought to -12 ° C until use.

2-b): adding cellulose powder to the above-mentioned pre-cooled mixed solvent, wherein the mass ratio of the mixed solvent to the cellulose is 100:4; then the obtained cellulose suspension is vigorously stirred at a stirring speed of 7500 rpm. The time is 2 minutes, and finally a homogeneous, transparent cellulose solution, that is, a mixed solution of cellulose/sodium hydroxide/urea/deionized water, is obtained.

Step (3). Preparation of a composite hydrogel of cellulose/less Ti ₃ C ₂ T _x nanosheets, the specific steps of which are as follows:

3-a): taking 5 mL of the cellulose solution in the step (2), taking a small layer of Ti ₃ C ₂ T _x nanosheet solids in the step (1), wherein the cellulose and the less Ti ₃ C ₂ T _x nanosheets The mass ratio is 100: 0.0001, taking 0.5 mL of epichlorohydrin, that is, the ratio of the volume of the cellulose solution to the epichlorohydrin is 100:10; the three are highly stirred, the stirring speed is 7500 rpm, and the time is 2 minutes; Then ultrasonically in a water bath, ultrasonic power 300W for 15 minutes, to obtain a mixture after ultrasonication, ie, cellulose / epichlorohydrin / less Ti ₃ C ₂ T _x nanosheet / sodium hydroxide / urea / deionized water Mixed solution.

3-b): The above-mentioned ultrasonic mixture was placed in an oil bath at 70 ° C for chemical crosslinking reaction for 1.5 hours to obtain a crosslinked reactant, that is, cellulose/epichlorohydrin/small layer Hydrogel of Ti ₃ C ₂ T _x nanosheets / sodium hydroxide / urea / deionized water.

3-c): 15 mL of a dilute sulfuric acid solution having a mass fraction of 8% was added to the above cross-linking reaction, and the acid was immersed for 40 minutes to cause the cellulose regeneration behavior, that is, the cellulose molecular chain to precipitate. Next, the regenerated cross-linked reactant is placed in deionized water and dialyzed for 5 days to gradually dialyze out sodium hydroxide, urea, and sulfuric acid to finally obtain a composite water of cellulose/small layer Ti ₃ C ₂ T _x nanosheet. gel.

The composite hydrogel of the cellulose/small layer Ti ₃ C ₂ T _x nanosheet prepared by the embodiment of the invention comprises a three-dimensional network structure formed by crosslinking the cellulose molecule and the crosslinking agent, and is loaded in the three-dimensional network structure. A small layer of Ti ₃ C ₂ T _x nanosheets.

Example 2

A composite hydrogel prepared from cellulose/small layer Ti ₃ C ₂ T _x nanosheets differs from Example 1 in that, in step 3-a), cellulose and a small layer of Ti ₃ C ₂ T _x nanosheets The mass ratio is 100:0.01.

Example 3

A composite hydrogel prepared from cellulose/small layer Ti ₃ C ₂ T _x nanosheets differs from Example 1 in that, in step 3-a), cellulose and a small layer of Ti ₃ C ₂ T _x nanosheets The mass ratio is 100:0.03.

Example 4

The composite hydrogel for preparing cellulose/less Ti ₃ C ₂ T _x nanosheets differs from Example 1 in the quality of cellulose and less Ti ₃ C ₂ T _x nanosheets in step 3-a) The ratio is 100:0.05.

Example 5

The composite hydrogel for preparing cellulose/less Ti ₃ C ₂ T _x nanosheets differs from Example 1 in the quality of cellulose and less Ti ₃ C ₂ T _x nanosheets in step 3-a) The ratio is 100:5.

Example 6

The composite hydrogel for preparing cellulose/less Ti ₃ C ₂ T _x nanosheets differs from Example 1 in the quality of cellulose and less Ti ₃ C ₂ T _x nanosheets in step 3-a) The ratio is 100:10.

Example 7

The composite hydrogel for preparing cellulose/less Ti ₃ C ₂ T _x nanosheets differs from Example 1 in the quality of cellulose and less Ti ₃ C ₂ T _x nanosheets in step 3-a) The ratio is 100:50.

To highlight the beneficial effects of the present invention, the following comparative examples are provided:

Comparative example 1

Preparation of cellulose hydrogels, including:

Step (1). Preparing an alkaline aqueous solution of transparent and uniform cellulose, the specific steps are as follows:

1-a): sodium hydroxide, urea and deionized water were added to a 200 mL beaker at a mass ratio of 7%/12%/81% to obtain a mixed solvent, wherein the mass of deionized water was 81.0 g. That is, the total volume of the mixed solvent was 100 mL; the mixed solvent was pre-cooled for 30 minutes, and the temperature was brought to -12 ° C until use.

1-b): adding the cellulose powder to the pre-cooled mixed solvent, wherein the mass ratio of the mixed solvent to the cellulose is 100:1; and then the obtained cellulose suspension is vigorously stirred at a stirring speed of 7500 rpm. The time was 2 minutes, and finally a homogeneous, transparent cellulose solution, that is, a mixed solution of cellulose/sodium hydroxide/urea/deionized water, was obtained.

Step (2). Preparation of a cellulose hydrogel, the specific steps of which are as follows:

2-a): Take 5 mL of the cellulose solution in the step (1), and take 0.1 mL of epichlorohydrin, that is, the ratio of the volume of the cellulose solution to the epichlorohydrin is 100:2; the three are highly stirred and stirred. The speed is 7500 rpm and the time is 2 minutes; then the water bath is ultrasonic, the ultrasonic power is 300 W, and the time is 15 minutes, and the ultrasonic mixture is obtained, that is, the mixture of cellulose/epichlorohydrin/sodium hydroxide/urea/deionized water. Solution, ready to use.

2-b): The above mixed solution after ultrasonication is placed in an oil bath at 70 ° C to cause a chemical crosslinking reaction for 1.5 hours to obtain a crosslinked reactant, that is, cellulose/epichlorohydrin/hydrogen peroxide Sodium/urea/deionized water hydrogel, ready for use.

2-c): 15 mL of a dilute sulfuric acid solution having a mass fraction of 8% was added to the above cross-linking reaction solution for 40 minutes to regenerate the cellulose. Next, the regenerated cross-linked reactant is placed in deionized water and dialyzed for 5 days to gradually dialyze out sodium hydroxide and urea to finally obtain a hydrogel of cellulose/epichlorohydrin (referred to as cellulose water for short). gel).

Comparative Example 2: The difference from Comparative Example 1 was that the mass ratio of the mixed solvent to the cellulose was 100:2, and the ratio of the volume of the cellulose solution to the epichlorohydrin was 100:4.

Comparative Example 3: The difference from Comparative Example 1 was that the mass ratio of the mixed solvent to the cellulose was 100:3, and the ratio of the volume of the cellulose solution to the epichlorohydrin was 100:6.

Comparative Example 4: The difference from Comparative Example 1 was that the mass ratio of the mixed solvent to the cellulose was 100:4, and the ratio of the volume of the cellulose solution to the epichlorohydrin was 100:10.

Comparative Example 5: The difference from Comparative Example 1 was that the mass ratio of the mixed solvent to the cellulose was 100:4, and the ratio of the volume of the cellulose solution to the epichlorohydrin was 100:14.

Comparative Example 6: The difference from Comparative Example 1 was that the mass ratio of the mixed solvent to the cellulose was 100:4, and the volume ratio of the cellulose solution to the epichlorohydrin was 100:20.

1 is a transmission electron microscope microtopography of a small layer of Ti ₃ C ₂ T _x nanosheets used in an embodiment of the present invention, (a) being a low resolution photograph; and (b) being a high resolution photograph. The microscopic morphology of the less Ti ₃ C ₂ T _x nanosheets was tested as follows: Apparatus: High resolution transmission electron microscope; Model: FEI Tecnai G ² F30; Test high pressure: 300 kV.

It can be seen from (a) of FIG. 1 that the size of the small-layer Ti ₃ C ₂ T _x nanosheet is about 60 nm×200 nm; as shown in (b) of FIG. 1, a small layer of Ti ₃ C ₂ T _x nanosheets is shown. A distinct plurality of layered structures indicate that the lesser Ti ₃ C ₂ T _x nanosheets of the present invention have a better two-dimensional layered structure. Further, the number of layers of the obtained small-layer Ti ₃ C ₂ T _x nanosheets is 6 to 10 layers. It can be seen from (c) of FIG. 1 that the obtained small-layer Ti ₃ C ₂ T _x nanosheet has a weak selective electron diffraction structure, indicating that the small-layer Ti ₃ C ₂ T _x nanosheet has a certain crystal structure.

Figure 2 provides a macro photograph of the resulting aqueous solution (100 ppm) of a small layer of Ti ₃ C ₂ T _x nanosheets placed at room temperature for 24 hours, and the cellulose hydrogel and cellulose/less Ti ₃ C of Comparative Example 4 Macroscopic photograph of a composite hydrogel of ₂ T _x nanosheets (Examples 2, 4, 6 and 7). It can be seen from Fig. 2 that the small layer of Ti ₃ C ₂ T _x nanosheet aqueous solution is uniformly dispersed 24 hours ago (Fig. 2 (a)); however, after standing for 24 hours, a small amount of Ti ₃ C ₂ T _x nanosheet aqueous solution is obtained. Significant sedimentation behavior occurred, and the color of the solution became lighter (Fig. 2(c)), indicating that the water solubility of the less Ti ₃ C ₂ T _x nanosheets was poor. It can be seen from (c) of Fig. 2 that the pure cellulose hydrogel (Comparative Example 4) has a colorless translucent "jelly-type" macroscopic morphology as a whole; and after the successful introduction of a small number of Ti ₃ C ₂ T _x nanosheets The composite hydrogel of the obtained cellulose/small layer Ti ₃ C ₂ T _x nanosheets is black with the increase of the content of the less Ti ₃ C ₂ T _x nanosheets, and the two have a vivid color contrast.

Figure 3 provides a composite hydrogel of cellulose hydrogel ((a), Comparative Example 4) and cellulose/less Ti ₃ C ₂ T _x nanosheets ((b), Example 4) after freeze drying A scanning electron micrograph of the corresponding aerogel obtained. The test conditions were as follows: To test the macromolecular porous structure in the cellulose hydrogel, the tested hydrogel (the cellulose hydrogel of Comparative Example 4 and the cellulose/less Ti ₃ C ₂ T _x nm of Example 4) The composite hydrogel of the tablet was first subjected to freeze-drying treatment to obtain a corresponding aerogel structure, wherein the experimental conditions of freeze-drying were: temperature: -80 ° C; time: 72 hours. Then the microtopography was tested, the instrument equipment used: cold field emission scanning electron microscope; model: SEM-Hitachi SU8010; test voltage: 3kV; sample surface silver time: 20 seconds.

As can be seen from Figure 3, both types of aerogels exhibit significant porosity, which is determined by the three-dimensional gel network structure of cellulose. However, it is obvious that the composite hydrogel of the cellulose/small layer Ti ₃ C ₂ T _x nanosheet prepared by the invention has a uniform pore structure distribution, and the pore diameter is 50-80 μm, and the porosity is obtained. About 75%.

The composite hydrogels of the cellulose/epichlorohydrin hydrogel prepared in Comparative Examples 1 to 6 and the cellulose/less Ti ₃ C ₂ T _x nanosheets prepared in Examples 1 to 7 were respectively subjected to mechanical properties. Test and photothermal performance tests, the results are shown in Table 1.

Table 1 Basic composition and performance parameters of hydrogels in Comparative Examples 1-6 and Examples 1-7

Table 1 shows typical compositions and physical properties of Comparative Examples 1-6 and Examples 1-7 of the present invention. As is apparent from Table 1, in Comparative Examples 1 to 6, as the volume fraction of the crosslinking agent epichlorohydrin was increased, the mechanical strength of the finally obtained cellulose hydrogel was also remarkably increased. For example, when the volume ratio of cellulose solution to epichlorohydrin is 100:0.2 (ie, Comparative Example 1), the compression modulus is 19.4 kPa; when the volume ratio of cellulose solution to epichlorohydrin is increased to 100:1.0 (i.e., Comparative Example 4) and 100:2.0 (i.e., Comparative Example 6), their respective compressive moduli increased to 60.8 kPa and 79.1 kPa, respectively, due to the higher cross-linking agent content of the cellulose hydrogel. The degree of chemical cross-linking is greatly increased. However, pure cellulose hydrogel lacks any functionality and does not exhibit any photothermal effect, and its photothermal equilibrium temperature is 25 ° C, which is substantially the same as room temperature.

However, as a strong contrast, in the composite hydrogel of the cellulose/small layer Ti ₃ C ₂ T _x nanosheets provided in Examples 1-7, due to the introduction of a small number of Ti ₃ C ₂ T _x nanosheets, The final photothermal equilibrium temperature is greatly increased. For example, when the mass ratio of cellulose to a small layer of Ti ₃ C ₂ T _x nanosheet is 100:0.0001 (ie, Example 1), the final photothermal equilibrium temperature of the composite hydrogel can be 0.5 and 1.0 W/cm ² . Reaching 50.2 and 55.4 ° C, respectively, has an increase of about 25.2 and 30.4 ° C compared to a pure cellulose hydrogel. When the cellulose composite hydrogel continues to increase / layer less Ti ₃ C ₂ T _x nanosheet layer of less Ti ₃ C ₂ T nanosheet mass fraction _x, the equilibrium temperature of the photothermal even more than the substantial increase The detection range of the thermal imager. For example, when the mass ratio of cellulose to a small number of Ti ₃ C ₂ T _x nanosheets is 100:5 (ie, Example 5), the final photothermal equilibrium temperature of the composite hydrogel is 0.5 and 1.0 W/cm ² , respectively. 122 and 135.7 ° C; the final light of the composite hydrogel when the mass ratio of cellulose to the small layer of Ti ₃ C ₂ T _x nanosheets is 100:10 (ie, Example 6) and 100:50 (ie, Example 7) The heat balance temperature is higher than 150 ° C, which exceeds the detection range of the thermal imager.

The above results indicate that the introduction of a two-dimensional layered material (specifically, a small layer of Ti ₃ C ₂ T _x nanosheets) not only significantly improves the mechanical strength of the cellulose hydrogel, but also imparts excellent light to the cellulose hydrogel. Thermal properties, and this property can be adjusted by the content of a small number of Ti ₃ C ₂ T _x nanosheets. And when a lower quality Ti ₃ C ₂ T _x nanosheet is used, the composite hydrogel can be brought to a higher photothermal equilibrium temperature.

The above-mentioned embodiments are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Claims

A cellulose/two-dimensional layered material composite hydrogel, characterized in that the composite hydrogel comprises a cellulose three-dimensional network structure, and a two-dimensional material supported in the cellulose three-dimensional network structure, The two-dimensional layered material is a two-dimensional transition metal carbide, nitride or carbonitride.
The composite hydrogel of claim 1 wherein said two dimensional layered material has a thickness of from 6 to 10 nm and a transverse dimension of from 60 to 200 nm.
The composite hydrogel according to claim 1, wherein said three-dimensional network structure of cellulose comprises a three-dimensional network structure in which cellulose or a cellulose derivative itself is linked, or a cellulose and/or cellulose derivative is passed A three-dimensional network structure formed by a crosslinking agent.
The composite hydrogel according to claim 3, wherein the cellulose derivative comprises cellulose modified with at least one of graphene oxide, chitosan, cyclodextrin, and gelatin, or Carboxylated, silylated cellulose.
The composite hydrogel of claim 3 wherein said crosslinking agent comprises at least one of epichlorohydrin and isocyanate.
The composite hydrogel according to claim 1 or 3, wherein the cellulose three-dimensional network structure has a pore structure having a pore diameter of 40 to 130 μm.
The composite hydrogel of claim 6 wherein said pore structure has a pore size of from 50 to 80 μm.
The composite hydrogel according to claim 1 or 3, wherein the mass ratio of the cellulose in the three-dimensional network structure of the cellulose to the nanosheet of the two-dimensional material is 100: (0.0001-50).
The composite hydrogel according to claim 3, wherein a mass ratio of the cellulose to the crosslinking agent in the three-dimensional network structure of the cellulose is 100: (1.372 - 13.71).
A method for preparing a cellulose/two-dimensional material nanosheet composite hydrogel, comprising the steps of:

(1) providing a two-dimensional layered material, the two-dimensional layered material being a two-dimensional transition metal carbide, nitride or carbonitride;

(2) preparing a mixed solvent containing a strong base, urea and water, and pre-cooling, adding the cellulose powder to the mixed solvent after pre-cooling, and vigorously stirring to obtain a cellulose solution;

(3) mixing the two-dimensional layered material and the crosslinking agent with the cellulose solution under high-speed stirring, and after ultrasonic treatment, crosslinking reaction at 65-90 ° C for 0.5-2 hours, Cross-linking reactant;

(4) The cellulose regenerant is added to the cross-linking reaction solution for 30-60 minutes, and then the regenerated cross-linking reactant is placed in water for dialysis to obtain a cellulose/two-dimensional layered material composite hydrogel.
The production method according to claim 10, wherein the mixed solvent has a mass concentration of a strong base of 5-15% and a mass concentration of urea of 10-15%.
The preparation method according to claim 10, wherein a mass ratio of the mixed solvent to the cellulose in the cellulose solution is 100: (1-4); the quality of the cellulose solution is crosslinked with the cellulose The mass ratio of the agent is 100: (0.212-2.12).
The production method according to claim 10, wherein the crosslinking agent is an incomplete hydrophobic substance having at least one of an epoxy group and an isocyanate group.
The production method according to claim 10, wherein the cellulose powder has a particle diameter of 10 to 30 μm.
The preparation method according to claim 10, wherein the two-dimensional layered material has a chemical formula of M n+1 X n T x , wherein M is a transition metal element, and X is a carbon element and/or a nitrogen element. n is an integer of 1-3, T x represents a surface group, and T may be selected from at least one of O 2− , OH − , F − and NH 4 + .
The preparation method according to claim 10, wherein in the step (3), the cellulose regenerating liquid is a dilute sulfuric acid solution having a mass fraction of 5% to 10%; the cross-linking reactant and the dilute The volume ratio of the sulfuric acid solution is 1: (2-3).
The method according to claim 10, wherein the mass ratio of the cellulose to the black phosphorus nanosheet is 100: (0.0001-50).
The method according to claim 17, wherein the mass ratio of the cellulose to the black phosphorus nanosheet is 100: (0.0001 - 0.01).
The preparation method according to claim 10, wherein in the step (1), the rotational speed of the vigorous stirring is 7000 to 10000 rpm, and the time of the vigorous stirring is 1-3 minutes;

In the step (2), the high-speed stirring speed is 7000 to 10000 rpm, and the high-speed stirring time is 1-3 minutes.
The preparation method according to claim 10, wherein the cellulose/two-dimensional layered material composite hydrogel comprises a cellulose three-dimensional network structure crosslinked by cellulose and a crosslinking agent, and further comprising a load in said A two-dimensional layered material in a three-dimensional network structure of cellulose.