A method for preparing hydrogel, hydrogel and application of hydrogel

Abstract

The present application provides a method for preparing a hydrogel, a hydrogel, and an application of the hydrogel. The method for preparing a hydrogel provided in the present application comprises: preparing an initial precursor solution using gelatin, acrylamide, N,N'-methylenebisacrylamide, and a pre-prepared MXene material; adding acrylic acid and ZrCl4 to the initial precursor solution, and stirring for a first preset time to obtain a target precursor solution; adding ammonium persulfate to the target precursor solution, stirring for a second preset time, and then transferring it to a mold to form a hydrogel at room temperature; the hydrogel exhibits a gradient wettability structure that gradually transitions from hydrophilicity to hydrophobicity, and MXene material is evenly distributed inside. The method for preparing a hydrogel provided in the present application can quickly achieve gelation in a very short time, and has the advantages of time saving, low carbon and environmental protection. In addition, through the method for preparing a hydrogel, a gradient wettability structure can also be formed to improve the water transport capacity of the hydrogel.

Description

Technical Field

[0001] The present application relates to the technical field of hydrogel preparation, and in particular to a hydrogel preparation method, a hydrogel, and applications of the hydrogel. Background Art

[0002] Water shortage is one of the major challenges that urgently needs to be addressed. Seawater is recognized as one of the world's most abundant natural resources. To alleviate this problem, various desalination technologies have been developed. Traditional desalination technologies include reverse osmosis, electrodialysis, and distillation. However, the energy consumption and high costs associated with these technologies hinder their application in resource-scarce areas.

[0003] With the continuous development of technology, the emergence of solar desalination technology has become increasingly popular among scientists due to its green and sustainable nature. The key to improving the performance of solar interfacial photoevaporation desalination is to enhance the photothermal conversion performance, evaporation efficiency, and fouling resistance of the interfacial photoevaporator. Interfacial solar evaporation devices are typically composed of a substrate material and a photothermal conversion material. Regarding the substrate material, hydrogels with excellent water permeability and three-dimensional pore structures are gaining increasing attention in the field of seawater desalination.

[0004] However, traditional hydrogel synthesis usually utilizes freeze-drying or other complex and time-consuming preparation methods, and requires external energy input such as heat, ultraviolet rays, irradiation, etc. It usually takes several hours or even days to complete the gelation of the hydrogel, which is not suitable for rapid large-scale production. Summary of the Invention

[0005] In view of this, the present application provides a hydrogel preparation method, a hydrogel, and an application of the hydrogel, for quickly preparing the hydrogel at room temperature.

[0006] Specifically, this application is implemented through the following technical solutions:

[0007] In a first aspect, the present application provides a method for preparing a hydrogel, comprising:

[0008] An initial precursor solution is prepared using gelatin, acrylamide, N,N'-methylenebisacrylamide, and a pre-prepared MXene material; wherein the MXene material is uniformly dispersed in the initial precursor solution;

[0009] Acrylic acid and ZrCl4 are added to the initial precursor solution and stirred for a first preset time to obtain a target precursor solution; wherein the ZrCl4 is hydrolyzed in the initial precursor solution to release Zr 4+ ;

[0010] Ammonium persulfate is added to the target precursor solution, stirred for a second preset time, and then transferred to a mold to form a hydrogel at room temperature; wherein the ammonium persulfate decomposes in the target precursor solution to generate free radicals, which initiate a polymerization reaction of the acrylic acid, the acrylamide, and the N,N'-methylenebisacrylamide, preferentially forming an acrylic acid-acrylamide copolymer network at the bottom of the mold; as the polymerization reaction continues, the acrylic acid gradually copolymerizes with the gelatin, gradually forming a polyacrylic acid-gelatin copolymer network at the top of the mold, so that the finally formed hydrogel exhibits a gradient wettability structure that gradually transitions from hydrophilicity to hydrophobicity along the bottom-up direction of the mold, and the MXene material is evenly distributed inside the hydrogel.

[0011] The second aspect of the present application provides a hydrogel, which is prepared based on the hydrogel preparation method described in any one of the first aspects of the present application; the hydrogel is a hydrogel with a three-dimensional network structure; wherein the hydrogel exhibits a gradient wettability structure that gradually transitions from hydrophilicity to hydrophobicity along the bottom-up direction of the mold, and MXene material is evenly distributed inside the hydrogel.

[0012] A third aspect of the present application provides an application of a hydrogel, wherein the hydrogel is prepared based on the hydrogel preparation method described in any one of the first aspects of the present application, and the hydrogel is used for seawater desalination and seawater purification.

[0013] The hydrogel preparation method provided in this application has the following technical effects:

[0014] (1) Through MXene and Zr 4+ The synergistic effect of the hydrogel and the rapid gelation of the hydrogel can be achieved under mild conditions without any external energy input;

[0015] (2) The hydrogel system is based on polyacrylic acid and gelatin, and acrylamide and N, N'-methylenebisacrylamide are introduced to optimize the pore structure of the hydrogel. The hydrogel synthesized on this basis can form a gradient wettability structure. The upper photothermal conversion layer is used for solar energy absorption and water evaporation, and the lower hydrophilic network can ensure sufficient water supply. This unique wettability change can effectively directionally pump liquid and confine it to the water transport channel, thereby achieving low heat loss and good water supply.

[0016] (3) Thanks to the excellent photocatalytic properties of MXene materials, the hydrogel formed by this method has excellent photocatalytic bactericidal properties. Within 1 h, the sterilization rate of Escherichia coli is as high as 99%. After 10 sterilization cycle tests, the sterilization rate has not decreased significantly, and the surface has a good cyclic sterilization effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of the hydrogel preparation method provided in this application;

[0018] Figure 2 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 Hydrogel and GAM1Zr 4.5 Comparison of hydrogels;

[0019] Figure 3 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 Test diagram of the water absorption process of water droplets on the hydrogel surface;

[0020] Figure 4 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 Energy dispersive X-ray spectra of the hydrogel surface;

[0021] Figure 5 MXene material and Zr shown in an exemplary embodiment of this application 4+ Effect of the addition amount on the gel time of hydrogel;

[0022] Figure 6 MXene material and Zr shown in an exemplary embodiment of this application 4+ Effect of the addition amount on the mechanical properties of hydrogel;

[0023] Figure 7 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 FTIR spectrum of hydrogel;

[0024] Figure 8 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 XPS spectrum of hydrogel;

[0025] Figure 9 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 XRD pattern of hydrogel;

[0026] Figure 10 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 UV-Vis-NIR spectra of hydrogel;

[0027] Figure 11 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 Graph showing the change of hydrogel surface temperature with irradiation time;

[0028] Figure 12Pure water, GAMZr and GBAAM1Zr under 1 sun intensity 4.5 Graph showing the change in evaporation volume of the hydrogel evaporator over time;

[0029] Figure 13 The mass loss graph and evaporation rate graph of the hydrogel under 0.5, 1, 1.5 and 2 sun illumination intensities shown in an exemplary embodiment of the present application;

[0030] Figure 14 Infrared images of the hydrogel evaporator under different light intensities after evaporation for 1 h;

[0031] Figure 15 This is a diagram of an experimental setup for a photocatalytic sterilization test on Escherichia coli according to an exemplary embodiment of the present application;

[0032] Figure 16 This is an exemplary embodiment of the present application showing the effect of photocatalytic inactivation of Escherichia coli without hydrogel;

[0033] Figure 17 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The photocatalytic inactivation effect of the hydrogel under one sun's light intensity;

[0034] Figure 18 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 Photocatalytic inactivation of E. coli by hydrogel under dark conditions;

[0035] Figure 19 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The sterilization performance of the hydrogel in the cyclic photocatalytic system after ten consecutive test cycles;

[0036] Figure 20 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The effect diagram of the hydrogel durability experiment;

[0037] Figure 21 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The results of the hydrogel's salt tolerance experiment;

[0038] Figure 22 An exemplary embodiment of the present application shows GBAAM1Zr after being immersed in acid, alkali and salt solution for 7 days. 4.5 Photographs of hydrogels;

[0039] Figure 23 A physical diagram showing an outdoor evaporation device according to an exemplary embodiment of the present application;

[0040] Figure 24 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 Rendering of the hydrogel outdoor evaporation experiment. DETAILED DESCRIPTION

[0041] Exemplary embodiments are described in detail herein, with examples illustrated in the accompanying drawings. When the following description refers to the drawings, identical numerals in different drawings represent identical or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with this application.

[0042] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms "a," "the," and "the" used in this application are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0043] It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0044] Specific embodiments are given below to introduce the technical solutions of the present application in detail.

[0045] Figure 1 This is a flow chart of the hydrogel preparation method provided in this application. Figure 1 The method provided in this embodiment may include:

[0046] S101. Prepare an initial precursor solution using gelatin, acrylamide, N,N'-methylenebisacrylamide, and a pre-prepared MXene material; wherein the MXene material is uniformly dispersed in the initial precursor solution.

[0047] Specifically, in one possible implementation, the initial precursor solution is prepared using gelatin, acrylamide (AM), N,N'-methylenebisacrylamide (MBA), and pre-prepared MXene material, including:

[0048] Step 1: Add a first specified amount of MXene material to deionized water and ultrasonically vibrate for a third preset time to uniformly disperse the MXene material in the deionized water to form a stable suspension.

[0049] The following is a brief introduction to the raw materials used in this application:

[0050] Specifically, lithium fluoride LiF (LiF with a purity of 99%), titanium aluminum carbide Ti3AlC2 (Ti3AlC2 with a purity of 98%), zirconium chloride ZrCl4 (ZrCl4 with a purity of 99%), acrylamide (acrylamide with a purity of 99%) and N,N'-methylenebisacrylamide were provided by Shanghai MacLean Biochemical Technology Co., Ltd.; gelatin, acrylic acid, ammonium persulfate, sodium chloride and hydrochloric acid were provided by Sinopharm Chemical Reagent Co., Ltd.; Escherichia coli was provided by Shanghai Luwei Technology; further, the chemical substances used in this application were used directly without further purification, and the solutions were prepared using distilled water.

[0051] In a specific implementation, in one possible implementation, in this step, a certain amount of MXene is first added to 20 ml of deionized water so that the MXene accounts for a specific weight percentage of the total mass of the deionized water; then, in order to ensure that the MXene added to the deionized water can be evenly dispersed in the deionized water, the mixed solution is ultrasonically shaken for 30 minutes using an ultrasonic shaker to obtain a stable suspension.

[0052] It should be noted that a certain amount of MXene is added to 20 ml of deionized water so that its specific weight percentage of the total mass of the deionized water can be 0.5 wt %, 1 wt % and 1.5 wt %; among which 0.5 wt % means that 0.1 g of MXene is added to 20 ml of deionized water, 1 wt % means that 0.2 g of MXene is added to 20 ml of deionized water, and 1.5 wt % means that 0.3 g of MXene is added to 20 ml of deionized water.

[0053] It should be noted that the MXene material in this embodiment is pre-prepared. The preparation process of the pre-prepared MXene material may include:

[0054] (1) An etching solution containing HF is prepared using HCl solution and LiF.

[0055] It should be noted that, in a specific implementation, HCl solution and LiF can be mixed in a ratio of 1:1 to obtain an etching solution; if there is too much LiF, it may lead to excessive generation of HF, increasing unnecessary by-products; if there is too much HCl solution, it may cause LiF to fail to react completely, affecting the efficiency of the reaction.

[0056] (2) Ti3AlC2 is added to the etching solution to selectively remove Al atoms using HF to generate a black product; wherein the black product is Ti3C2 with a layered structure, and functional groups Tx are formed on the surface of the Ti3C2.

[0057] Specifically, after Ti3AlC2 is added to the etching solution, HF selectively removes aluminum (Al) atoms in Ti3AlC2 and converts the aluminum in Ti3AlC2 into aluminum fluoride (AlF3) by chemically reacting with aluminum. In this way, the Ti3AlC2 in the raw material becomes Ti3C2 composed of titanium (Ti) and carbon (C).

[0058] It should be noted that the Ti3C2 produced in this step is a black product and a layered material. Due to the etching effect of HF in the etching solution, various functional groups (usually -OH, -F, -O, -F, etc.) are formed on the surface of Ti3C2. These functional groups are collectively referred to as Tx. Through Tx, the chemical properties of Ti3C2 can be effectively improved.

[0059] (3) The black product is washed and centrifuged until the pH value of the washing solution is greater than 6.

[0060] (4) The black product after washing and centrifugation was freeze-dried for 48 h to obtain the MXene material.

[0061] In the above steps (3) and (4), the black product Ti3C2 is washed with deionized water to remove the aluminum fluoride (AlF3) remaining on its surface and the HF solution that has not reacted with Ti3AlC2, so as to avoid these impurities from interfering with the subsequent process; thereafter, the black product after washing is further centrifuged to further separate and remove the dissolved matter and residual liquid attached to its surface until the pH value of the final washing solution is greater than 6. The black product after washing and centrifugation is then freeze-dried for 48 hours to finally obtain the MXene material.

[0062] It should be noted that a pH value of the washing liquid greater than 6 indicates that the acidic substances in the washing liquid (the acidic substances in the washing liquid may include HF (hydrogen fluoride) and possible by-products (such as AlF3, HCl, etc.)) have been fully neutralized; further, freeze-drying the black product after washing and centrifugation can effectively remove moisture from the surface of the black product without destroying the layered structure of the black product. In this way, its original physical properties can be effectively maintained, avoiding the damage that traditional heating drying may cause to the final MXene material.

[0063] Step 2: Add gelatin to the suspension, and heat and stir at 45-55° C. for a fourth preset time, so that the gelatin is completely dissolved and fully mixed with the suspension to form a uniform first mixed solution.

[0064] In this step, gelatin, a natural polymer with excellent biocompatibility and gel-forming properties, serves as the three-dimensional scaffold material in the hydrogel system. Heating and stirring at 45-55°C significantly increases gelatin's solubility, making it readily soluble in water. This allows it to mix with the other components of the suspension. Gelatin acts as a gelling agent, helping to form a uniform first mixture within the suspension and providing gelling properties, which serve as a foundation for subsequent cross-linking reactions between the various substances.

[0065] In a specific implementation, the fourth preset time period may be 30 to 60 minutes. For example, in one possible implementation, in this step, 2 g of gelatin may be added to the suspension, and heated and stirred at 50° C. for 30 minutes.

[0066] Step 3: Add acrylamide and N,N'-methylenebisacrylamide to the first mixed solution to form a second mixed solution.

[0067] Specifically, acrylamide has excellent water solubility and can form linear polymer chains during free radical polymerization. N,N-methylenebisacrylamide, acting as a crosslinking agent, can promote the formation of crosslinked structures during the polymerization process. In this step, polymerization raw materials are added to the first mixed solution to provide the chemical components for forming a three-dimensional crosslinked hydrogel structure.

[0068] It should be noted that, in a possible implementation, 3 g of acrylamide and 0.28 g of N,N-methylenebisacrylamide may be added to the first mixed solution.

[0069] Step 4: Stir the second mixed solution in a water bath at 55-65° C. for a fifth preset time, and then cool to room temperature to obtain the initial precursor solution.

[0070] It should be noted that the fifth preset duration can be selected according to actual needs and is not limited in this application. For example, in one embodiment, the fifth preset duration can be 0.5h to 1h, and the following description is based on the fifth preset duration of 1h as an example.

[0071] Specifically, in this step, heating the second mixed liquid in a 60°C water bath can help promote the full dissolution and mixing of acrylamide and N,N'-methylenebisacrylamide in the second mixed liquid. Thereafter, after heating and stirring for a fifth preset time, cooling the mixed liquid at room temperature can stabilize the various structures in the second mixed liquid, ensure that the required polymerization or cross-linking reaction is carried out under controllable conditions, and avoid excessively rapid reaction within the second mixed liquid, which may affect the uniformity and performance of the desired initial precursor solution.

[0072] S102, adding acrylic acid and ZrCl4 to the initial precursor solution and stirring for a first preset time to obtain a target precursor solution; wherein the ZrCl4 is hydrolyzed in the initial precursor solution to release Zr 4+ .

[0073] It should be noted that the specific value of the first preset duration is set according to actual needs and is not adjusted in this embodiment. For example, in a possible implementation, the first preset duration is 20 to 40 minutes.

[0074] Optionally, in a possible implementation, 4 ml of acrylic acid (AA) and a certain amount of zirconium chloride (ZrCl 4 ) (accounting for 1.5, 3, or 4.5 mol% of AA) may be added to the initial precursor solution and stirred for 30 minutes.

[0075] It should be noted that acrylic acid contains a carboxyl (-COOH) functional group, which is a highly reactive chemical group within its structure. It contains a polar oxygen atom inside and can form hydrogen bonds or coordination bonds with other chemical substances to enhance its reactivity. During the synthesis of hydrogels, the carboxyl functional group can react with functional groups in other molecules to produce chemical crosslinks.

[0076] Acrylamide molecules contain amino (-NH2) functional groups, which have strong affinity and can react with the carboxyl groups in acrylic acid to promote free radical polymerization, thereby contributing to the formation of the internal network structure during the preparation of hydrogels. Furthermore, N,N'-methylenebisacrylamide contains two vinyl (-CH=CH2) functional groups, which have a carbon-carbon double bond (C=C) inside and have strong reactivity. They can react with the carboxyl groups in acrylic acid during polymerization to form cross-linking points, thereby enhancing the network structure of the hydrogel. The surface of MXene materials usually contains hydroxyl (-OH) or oxide (-O) functional groups, which can hydrogen bond or chemically react with the carboxyl groups in acrylic acid, thereby further enhancing the stability of the generated hydrogel. In addition, the functional groups on the surface of MXene can also react with Zr 4+The formation of coordination bonds between ZrCl4 and ZrCl4 can help the cross-linking reaction and promote the formation of hydrogels. 4+ The ions can coordinate with the carboxyl groups in acrylic acid to form stable coordination bonds, thereby making the structure in the precursor solution more stable and avoiding instability in subsequent reactions.

[0077] S103, adding ammonium persulfate to the target precursor solution, stirring for a second preset time, and then transferring to a mold to form a hydrogel at room temperature.

[0078] It should be noted that the specific value of the second preset time length is set according to actual needs and is not limited in this embodiment. For example, in one possible implementation, the second preset time length is 2 to 5 minutes, and 3 minutes is used as an example for explanation below.

[0079] In a specific implementation, in one possible implementation, 0.05 g of ammonium persulfate (APS) was added to the target precursor solution, stirred for 3 min, and then quickly transferred to a reaction vessel to form a hydrogel at room temperature, which was named GBAAM. x Zr y , where x represents different contents of MXene and y represents different contents of Zr 4+ .

[0080] It should be noted that the ammonium persulfate decomposes in the target precursor solution to generate free radicals, which trigger the polymerization reaction of the acrylic acid, the acrylamide and the N,N'-methylenebisacrylamide, and preferentially form an acrylic acid-acrylamide copolymer network at the bottom of the mold; as the polymerization reaction continues, the acrylic acid gradually copolymerizes with the gelatin, and gradually forms a polyacrylic acid-gelatin copolymer network at the top of the mold, so that the finally formed hydrogel exhibits a gradient wettability structure that gradually transitions from hydrophilicity to hydrophobicity along the bottom-up direction of the mold, and the MXene material is evenly distributed inside the hydrogel.

[0081] The following is a detailed introduction to the production mechanism of hydrogel:

[0082] Specifically, after the mixed liquid is injected into the mold, the heat at the bottom of the mold dissipates faster or the initiator gathers at the bottom first under the action of gravity, and the polymerization reaction takes effect first from the bottom.

[0083] In the initial stage, ammonium persulfate decomposes in the target precursor solution to generate free radicals. These free radicals act as initiators for the polymerization reaction, promoting the polymerization of double bonds in acrylic acid, acrylamide, and N,N'-methylenebisacrylamide molecules (the C=C double bonds of acrylic acid and acrylamide and the two C=C double bonds of N,N'-methylenebisacrylamide) to form long-chain polymers (acrylic acid-acrylamide copolymer chains), which are highly hydrophilic structures.

[0084] As the free radicals diffuse upward in the solution and the temperature becomes uniform, the –NH2, –OH, –COOH and other functional groups in gelatin begin to copolymerize with the vinyl or carboxyl groups in acrylic acid to form a polyacrylic acid-gelatin copolymer network (polyacrylic acid / gelatin copolymer chain), which is a relatively hydrophobic structure.

[0085] Referring to the previous description, it can be understood that the spatial distribution of the hydrogel changes layer by layer, with an acrylic acid-acrylamide copolymer network at the bottom and gradually transitioning to a polyacrylic acid-gelatin copolymer network upwards, ultimately forming a gradient wettability structure that gradually transitions from hydrophilic to hydrophobic.

[0086] It should be noted that in the initial suspension, MXene has been evenly dispersed after ultrasonic treatment, and its particle size is small and its hydrophilicity is strong. Therefore, it can be evenly embedded in the polymer network during the entire polymerization process, and through its surface hydroxyl (–OH) and oxide (–O - ) to form hydrogen bonds or coordination interactions with polymerized monomers to enhance the stability, mechanical properties, and electrical conductivity of the hydrogel.

[0087] The feasibility of the structural mechanism of the gradient wettability of the hydrogel surface morphology by adding acrylamide and N,N'-methylenebisacrylamide is analyzed below through a specific example:

[0088] First, in this embodiment, the structural characteristics and wettability of a hydrogel without the addition of acrylamide and N,N'-methylenebisacrylamide are introduced. The structural characteristics of this hydrogel include: a relatively loose internal network structure, random pore size and distribution, and a lack of a regular macroporous structure; scanning such a hydrogel using a scanning electron microscope (SEM), and the resulting SEM image shows no significant difference in the morphology between the upper and lower surfaces, and the surface is relatively uniform without obvious porous features; the internal molecular chains are weakly connected, the pore structure is irregular, and an effective water transport channel cannot be formed; further, the wettability of such a hydrogel includes: its overall wettability is uniformly distributed, lacking a gradient change from top to bottom; its water adsorption and capillary action are weak, and the liquid penetration and transport efficiency are low.

[0089] It should be noted that acrylamide contains an amide group (-CONH2), which has strong hydrophilicity and can form hydrogen bonds with water molecules, thereby significantly improving the hydrophilicity of hydrogels containing acrylamide; N,N'-methylenebisacrylamide, as a bifunctional cross-linker, contains two polymerizable double bonds and can play a cross-linking role in hydrogels.

[0090] Furthermore, in the present application, the hydrogel prepared by adding acrylamide and N, N'-methylenebisacrylamide, since N, N'-methylenebisacrylamide acts as a crosslinking agent, can increase the crosslinking points in the hydrogel molecular network, thereby increasing the crosslinking point density in the hydrogel molecular network, thereby forming a denser three-dimensional network structure inside the hydrogel. The addition of hydrophilic acrylamide will lead to the formation of more long molecular chains inside the hydrogel. These long molecular chains will be interconnected under the action of the crosslinking agent N, N'-methylenebisacrylamide, and leave pores between the multiple long molecular chains. In this way, the size of the pores inside the hydrogel can be effectively improved, promoting the adsorption and transfer of water inside the hydrogel. In addition, the acrylamide and N, N'-methylenebisacrylamide added to the hydrogel will also combine with the gelatin in the hydrogel to produce hydrogen bonds, further enhancing the hydrophobicity of the prepared hydrogel.

[0091] (1) Comparative Example 1

[0092] To illustrate the method provided in this embodiment, a gradient wettability structure can be formed by adding acrylamide and N, N'-methylenebisacrylamide to the hydrogel GAM1Zr 4.5 , and the hydrogel GBAAM1Zr formed in this embodiment 4.5 For comparison, the details are as follows:

[0093] Next, we first 4.5 A brief introduction to the formation process:

[0094] Specifically, 0.2 g of MXene was added to 20 ml of deionized water and ultrasonically shaken for 30 minutes to obtain a uniform suspension. Then, 2 g of gelatin was added to the above suspension and heated and stirred at 50 ° C for 30 minutes. Then, after the solution was cooled to, 4 ml of acrylic acid (AA) and 0.58 g of zirconium chloride (ZrCl4) were added and stirred for 30 minutes. Finally, 0.05 g of ammonium persulfate (APS) was added to the suspension, stirred for 3 minutes, and then quickly transferred to a reaction container to form a hydrogel at room temperature, which was named GAM1Zr 4.5 .

[0095] Further, Figure 2GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 Hydrogel and GAM1Zr 4.5 Comparison chart of hydrogels. Please refer to Figure 2 , (a1) Figure shows GAM1Zr 4.5 Digital images of hydrogels, (a2) GAM1Zr 4.5 SEM images of the upper surface of the hydrogel at a scale of 5µm, (a3) ​​shows GAM1Zr 4.5 SEM images of the hydrogel surface at a scale of 200µm, (a4) shows GAM1Zr 4.5 SEM images of the lower surface of the hydrogel at a scale of 5µm, (a5) shows GAM1Zr 4.5 SEM image of the lower surface of the hydrogel at a scale of 200µm; (b1) GBAAM1Zr 4.5 Digital images of hydrogels, (b2) GBAAM1Zr 4.5 SEM images of the upper surface of the hydrogel at a scale of 5µm, (b3) shows GBAAM1Zr 4.5 SEM image of the hydrogel surface at a scale of 200µm, (b4) shows GBAAM1Zr 4.5 SEM images of the lower surface of the hydrogel at a scale of 5µm, (b5) shows GBAAM1Zr 4.5 SEM image of the lower surface of the hydrogel at a scale of 200 µm.

[0096] Please continue Figure 2 Figures (a1) and (b1) of GAM1Zr 4.5 Hydrogel and GBAAM1Zr 4.5 The hydrogel is black in the whole picture, indicating that MXene is successfully doped into GAM1Zr 4.5 Hydrogel and GBAAM1Zr 4.5 In hydrogels, the hydrophilicity of the lower surface of the hydrogel can be enhanced through the hydrophilic functional groups of MXene.

[0097] Further, based on Figure 2 As can be seen from Figures (a2) to (a5), GAM1Zr 4.5 The upper surface of the hydrogel is relatively smooth, while its lower surface has dense pores, which is not conducive to water transport. Figure 2 In Figures (b2) to (b5), we can see that GBAAM1Zr 4.5 The upper surface of the hydrogel is still relatively smooth, which can inhibit the penetration of water molecules and has hydrophobicity, but GBAAM1Zr 4.5The lower surface of the hydrogel can be seen to have a dense and large pore structure at a scale of 200µm. Such a structure can be conducive to water transport, and it also verifies that the addition of acrylamide and N, N'-methylenebisacrylamide makes GBAAM1Zr 4.5 Multiple long molecular chains are formed inside the hydrogel and connected to form numerous pores.

[0098] In summary, compared with the hydrogel without acrylamide and N,N'-methylenebisacrylamide, the hydrogel prepared by adding acrylamide and N,N'-methylenebisacrylamide has a gradient wettability structure with a hydrophobic upper surface and a hydrophilic lower surface. Such a gradient wettability structure has a higher water transfer efficiency than the hydrogel with a uniform structure.

[0099] Referring to the previous description, it can be understood that by introducing acrylamide and N, N'-methylenebisacrylamide into the hydrogel, the pore size of the hydrogel can be effectively improved, which is beneficial to water transmission. The reason for this phenomenon may be that the increase in the content of the cross-linking agent N, N'-methylenebisacrylamide will lead to the formation of more cross-linking points, and the increase in the hydrophilic acrylamide monomer will lead to the formation of more long molecular chains. When these molecular chains are connected to each other under the action of the cross-linking agent N, N'-methylenebisacrylamide, pores will be left between them. In addition, the combination of acrylic acid and gelatin will produce hydrogen bonds, which will enhance the hydrophobicity of the hydrogel. It is for these reasons that GBAAM1Zr 4.5 The hydrogel formed a gradient wettability structure. Therefore, by adjusting the content of acrylamide and N,N'-methylenebisacrylamide, the polymerization reaction of the hydrogel can be regulated, thereby achieving the regulation of the hydrogel wettability gradient.

[0100] Furthermore, in this embodiment, the contact angle meter was used to measure the GBAAM1Zr 4.5 The water absorption process of water droplets on the hydrogel surface was used to evaluate its water absorption performance and verify the GBAAM1Zr 4.5 Hydrogel is a hydrogel with a gradient wettability structure.

[0101] Figure 3 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 Test diagram of the water absorption process of water droplets on the hydrogel surface.

[0102] For details, please refer to Figure 3 , Figure 3 The middle (a1) figure is GBAAM1Zr 4.5 The water contact angle measurement results of the upper surface of the hydrogel at 0s, (a2) is GBAAM1Zr 4.5 The water contact angle measurement results of the upper surface of the hydrogel at 0.1s, (a3) ​​is GBAAM1Zr4.5 Water contact angle measurement results of the upper surface of the hydrogel at 1 min; Figure 3 The middle (b1) figure shows GBAAM1Zr 4.5 The water contact angle measurement results of the lower surface of the hydrogel at 0s, (b2) is GBAAM1Zr 4.5 The water contact angle measurement results of the lower surface of the hydrogel at 0.1s, (b3) is GBAAM1Zr 4.5 The water contact angle measurement results of the lower surface of the hydrogel at 1 min. Figure 3 , it can be seen that GBAAM1Zr 4.5 The water contact angles on the upper and lower surfaces of the hydrogel show differences; when the water droplet just drops onto the GBAAM1Zr 4.5 When the hydrogel is on the surface, the water droplet and GBAAM1Zr 4.5 The water contact angle between the hydrogel surface at 0.1s and the water contact angle after 1min were almost unchanged, indicating that GBAAM1Zr 4.5 The upper surface of the hydrogel has a good barrier effect on water droplets and has strong hydrophobicity. Furthermore, when the water droplets fall onto the GBAAM1Zr 4.5 When the hydrogel is on the lower surface, the water droplet and GBAAM1Zr 4.5 The water contact angle between the lower surface of the hydrogel at 0.1s is compared with that between the water droplet and GBAAM1Zr 4.5 The contact angle between the upper and lower surfaces of the hydrogel is smaller at 0.1s, and at 3s, the water droplet passes smoothly through the GBAAM1Zr 4.5 The lower surface of the hydrogel showed that GBAAM1Zr 4.5 The lower surface of the hydrogel has a good transmission effect on water droplets and has strong hydrophilicity. 4.5 Hydrogel is a hydrogel with a gradient wettability structure.

[0103] Furthermore, for GBAAM1Zr 4.5 The surface of the hydrogel was subjected to EDS analysis to test the distribution of elements C, O, F, and Ti. Figure 4 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The energy dispersive X-ray spectrum of the hydrogel surface shows that the element Ti is evenly distributed on the sample skeleton. Ti is a characteristic element of MXene. This result confirms the uniform distribution of MXene in the hydrogel.

[0104] Furthermore, in order to verify the 4+ The effect of the addition amount on the gelation speed and mechanical properties of the hydrogel, the present application further carried out comparative experiments, as follows:

[0105] Figure 5 MXene material and Zr shown in an exemplary embodiment of this application 4+ The effect of the addition amount on the gel time of hydrogel. Figure 6 MXene material and Zr shown in an exemplary embodiment of this application 4+ The effect of the addition amount on the mechanical properties of the hydrogel. Figure 6 Figure (a) shows the case where the added MXene material is 0.5 wt% and the Zr 4+ Comparison of the fracture stress of the hydrogel when the content of is 1.5 wt%, 3 wt% and 4.5 wt%. Figure 6 In the middle (b), when the MXene material content is 1 wt%, the Zr 4+ The fracture stress comparison of the hydrogel is shown in the figure below when the content of 1.5 wt%, 3 wt% and 4.5 wt%. Figure 6 Figure (c) shows the case where the added MXene material content is 1.5 wt% and the Zr 4+ Comparison of the fracture stress of hydrogels when the content of is 1.5 wt%, 3 wt% and 4.5 wt%.

[0106] Please continue to refer to Figure 5 , Figure 5 It shows that when the added MXene material is 0.5 wt%, the Zr 4+ When the content of Zr is 1.5 wt%, 3 wt% and 4.5 wt%, the gel time of the hydrogel, and when the added MXene material is 1 wt%, the Zr 4+ When the content of Zr is 1.5 wt%, 3 wt% and 4.5 wt%, the gel time of the hydrogel, and when the added MXene material is 1.5 wt%, the Zr 4+ When the content of is 1.5 wt%, 3 wt% and 4.5 wt%, the gel time of the hydrogel is long. Figure 5 It can be seen that increasing the content of MXene material will accelerate the gelation speed of hydrogel. 4+ The increase in concentration will also accelerate the gelation rate of the hydrogel.

[0107] Referring to the previous description, it can be understood that by adjusting the MXene and Zr 4+ The content of MXene and Zr can regulate the gelation speed of the hydrogel. This is because different contents of MXene and Zr 4+It will affect the cross-linking degree and reaction rate in the hydrogel system, thus affecting the synthesis time and performance of the hydrogel. Specifically, increasing the MXene content will accelerate the gelation speed of the hydrogel, because MXene nanosheets have a large surface area and active sites, which can promote the formation of the hydrogel gel network. At the same time, Zr 4+ Increasing the concentration will also enhance the cross-linking density of the hydrogel, thereby accelerating the gelation speed of the hydrogel.

[0108] In summary, by adding MXene materials and Zr 4+ , which can improve the gelation speed of hydrogel, and with the addition of MXene materials and Zr 4+ The increase in the content can further improve the gelation speed of the hydrogel.

[0109] For further information, please refer to Figure 6 , it can be seen that with the increase of MXene content, the fracture stress of the hydrogel continues to decrease, and when the Zr 4+ The fracture stress of the hydrogel increases continuously with the increase of the content.

[0110] In summary, appropriate amounts of MXene materials and Zr can be added 4+ , in order to improve the gelation speed of the hydrogel at room temperature, and also pay attention to the MXene material content and Zr 4+ In this application, based on the above results, the MXene content was selected as 1 wt%, Zr 4+ GBAAM1Zr with a content of 4.5wt% 4.5 Hydrogels can have both a faster gelation speed and stronger mechanical properties at room temperature.

[0111] Further, referring to the above description, under the synergistic effect of the gradient wettability structure and the MXene material, the light absorption performance, evaporation performance, salt resistance, acid and alkali resistance, photocatalytic sterilization ability and cycle stability of the hydrogel are all improved. Therefore, in the following verification test, GBAAM1Zr 4.5 Hydrogel is used as an example for illustration.

[0112] The following tests verify that the hydrogel's light absorption performance, evaporation performance, salt resistance, acid and alkali resistance, photocatalytic sterilization ability, and cyclic stability have been improved:

[0113] It should be noted that a photoevaporator is a device that uses solar energy to convert water into steam, and hydrogel is the key material used in the photoevaporator.

[0114] (1) Surface chemical composition analysis

[0115] Figure 7 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 FTIR spectrum of hydrogel. It can be observed from the FTIR spectrum that GBAAM1Zr 4.5 The hydrogel is located at 1632 cm -1 A characteristic peak appears at 4+ It forms a coordination bond with the carboxyl group in the polyacrylic acid chain. 4.5 Hydrogel at 1706 cm -1 and 1163 cm -1 New characteristic peaks appeared at 1706 cm -1 The characteristic peak at GBAAM1Zr is attributed to the vibration of the -C=O double bond in the backbone structure of polyacrylic acid and polyacrylamide, indicating that AM and AA have successfully achieved cross-linking. 4.5 Hydrogel 1163 cm -1 The characteristic peak at is due to the stretching vibration of CN in MBA. 4.5 The hydrogel is located at 1414 cm -1 The characteristic peak at is attributed to the symmetric stretching of carboxylate ions. 4.5 The hydrogel is located at 1541 cm -1 The characteristic peak at is attributed to the asymmetric stretching of COO¯. These results indicate that the AA monomer successfully exists on the gelatin skeleton. 4.5 3180 cm of hydrogel -1 ~3333 cm -1 The absorption peaks of MXene surface hydroxyl groups were observed at all locations. Therefore, in GBAAM1Zr 4.5 During the preparation process, the structure of MXene was well maintained, as evidenced by X-ray diffraction patterns and X-ray photoelectron spectroscopy.

[0116] X-ray photoelectron spectroscopy (XPS) was used to characterize the GBAAM1Zr 4.5 The surface chemical composition of the hydrogel was analyzed. Figure 8 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 XPS spectrum of hydrogel. Figure 8 Figure (a) shows GBAAM1Zr 4.5 The complete XPS spectrum of the hydrogel shows the presence of C1s, N 1s, Ti 2p and O 1s peaks. Figure 8 Figure (b) shows GBAAM1Zr 4.5The C1s spectrum of the hydrogel shows that the peaks at 283.9 eV, 284.8 eV, 285.6 eV, 286.5 eV and 288.1 eV belong to C-Ti-O, CC, CN, CO, and C=O bonds, respectively. 4.5 The GBAAM1Zr 4.5 XPS analysis of Ti 2p diffraction peaks in hydrogel and MXene. Figure 8 Figure (c) shows GBAAM1Zr 4.5 XPS spectrum of Ti 2p diffraction peak in hydrogel, Figure 8 Figure (d) is the XPS spectrum of the Ti 2p diffraction peak of MXene, from GBAAM1Zr 4.5 The Ti 2p diffraction peaks in the hydrogel can be found, and the fitting peaks near 454.9 eV and 460.9 eV correspond to Ti-C, the peaks at 457.0 eV and 462.4 eV correspond to Ti-OH bonds, and the peaks at 459.1 eV and 463.9 eV correspond to TiO2 bonds, respectively, indicating that the modification of MXene is successful.

[0117] In order to further understand the changes in the crystal structure of MXene after forming hydrogel, XRD was used to characterize GBAAM1Zr 4.5 Hydrogel, MXene and Tl3AlC2 were characterized. Figure 9 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 For XRD pattern of hydrogel, please refer to Figure 9 , in GBAAM1Zr 4.5 The XRD pattern of the hydrogel completely preserves the (004) and (104) crystal planes of MXene. This change in crystal structure indicates that the two-dimensional layered structure of MXene is not destroyed during the formation of the dynamically cross-linked hydrogel. 4.5 The lattice parameters of the hydrogel are highly consistent with those of the MXene nanosheets, indicating that the structure of MXene is similar to that of GBAAM1Zr 4.5 The structural stability of GBAAM1Zr 4.5 Hydrogels have laid an important foundation for their application in fields such as photothermal conversion and catalysis.

[0118] (2) Light absorption performance

[0119] In this embodiment, firstly, GBAAM1Zr 4.5 The light absorption properties of the hydrogel were tested:

[0120] It should be noted that MXene materials, as the main solar energy absorption materials, can convert solar radiation into thermal energy.

[0121] In this example, in order to characterize the GBAAM1Zr 4.5 The light absorption properties of the hydrogel were measured using UV-visible-near-infrared diffuse reflectance measurements of GBAAM1Zr in the dry state. 4.5 Absorbance of the hydrogel.

[0122] Figure 10 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 UV-Vis-NIR spectrum of hydrogel, please refer to Figure 10 ,GBAAM1Zr 4.5 The hydrogel has excellent light absorption performance in the wavelength range of 250nm-2500nm, and also shows that the MXene material has excellent light absorption performance in the GBAAM1Zr 4.5 The surface of the hydrogel induces light scattering or refraction, and absorbs light into the GBAAM1Zr 4.5 In hydrogels, the light absorption properties of hydrogels are significantly enhanced.

[0123] In addition, in this example, in order to systematically evaluate GBAAM1Zr 4.5 The solar interface evaporation performance of the evaporator composed of hydrogel as the photothermal conversion material was also tested, and the actual photothermal conversion capacity of the evaporator was tested by using a solar simulator composed of xenon lamps to simulate the actual solar irradiation environment. Figure 11 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The surface temperature of the hydrogel changes with irradiation time. Figure 11 , it can be seen that GBAAM1Zr 4.5 The surface temperature changes with irradiation time. Under the same solar intensity, GBAAM1Zr 4.5 The surface temperature of the hydrogel rose rapidly to 32.3 °C within 10 min, and after 60 min, the GBAAM1Zr 4.5 The surface temperature of the hydrogel reached 39.9 °C, which also showed that GBAAM1Zr 4.5 The solar energy absorbed by the hydrogel can be confined in the evaporator and not diffused into the water body. The reason for this result is that GBAAM1Zr 4.5 The evaporator can localize the heat converted from solar energy on its surface, and the polystyrene foam can effectively inhibit the conduction of heat to the water body, which further verifies the GBAAM1Zr 4.5 The hydrogel has good light absorption properties.

[0124] (3) Evaporation performance

[0125] Furthermore, the evaporation performance of the hydrogel is tested as follows:

[0126] It should be noted that the GBAAM1Zr prepared by the hydrogel preparation method provided in this application 4.5 The gradient wettability structure of the hydrogel can achieve fast and efficient seawater desalination and freshwater extraction. In order to test the evaporation performance of the hydrogel, the first aspect of this experiment was to test the evaporation performance of pure water, GAM1Zr under 1 sun intensity. 4.5 (Hydrogel formed without AM and MBA) and GBAAM1Zr 4.5 The evaporation amount of hydrogel in the optical evaporator changes with time. Specifically, Figure 12 Pure water, GAMZr and GBAAM1Zr under 1 sun intensity 4.5 The evaporation amount of the hydrogel evaporator changes with time, where Figure 12 Figure (a) shows the intensity of pure water, GAMZr (specifically GAM1Zr) under one solar illumination. 4.5 )、GBAAM1Zr 4.5 Graph of mass variation in optical evaporator; Figure 12 Figure (b) shows pure water, GAMZr, and GBAAM1Zr under one sun's illumination intensity. 4.5 Diagram of the evaporation rate in a light evaporator.

[0127] Further, such as Figure 12 As shown in Figure (a), GAMZr and GBAAM1Zr 4.5 The evaporation rate of MXene-based gradient wettability hydrogel is significantly higher than that of pure water.

[0128] It should be noted that the evaporation rate was calculated by the mass loss in each test group recorded by the electronic balance, e.g. Figure 12 As shown in Figure (b), pure water, GAMZr and GBAAM1Zr 4.5 The evaporation rates are 0.426 kg·m -2 ·h -1 , 1.473 kg·m -2 ·h -1 , 1.762 kg·m -2 ·h -1 ,GBAAM1Zr 4.5 The evaporation rate is 4.14 times that of pure water, demonstrating the excellent water evaporation capacity of the solar-driven interface.

[0129] It should be noted that the design of the water evaporator includes the evaporation layer and the water transport layer. The evaporation layer is the core part of the water evaporation process. Its main function is to absorb sunlight and convert it into heat energy, causing water to change from liquid to gas. 4.5 In the hydrogel, the evaporation layer uses MXene material, which makes it have a strong light-heat conversion ability and can effectively accelerate the evaporation of water. In addition, the main function of the water transport layer is to transport water from the water storage area to the evaporation layer, ensuring that water can continuously flow from the water storage area to the evaporation layer, thereby avoiding the inability to transport water to the evaporation layer in time during the evaporation process. 4.5 In the hydrogel, the design of the water transport layer can ensure rapid replenishment of water, thereby maintaining an efficient evaporation rate of the evaporation layer.

[0130] Furthermore, in order to explore the effect of different solar illumination intensities on GBAAM1Zr 4.5 The second aspect of this experiment also tested the effect of hydrogel evaporation on GBAAM1Zr 4.5 Mass loss and evaporation rate of hydrogels under irradiation of 0.5, 1, 1.5, and 2 suns.

[0131] Figure 13 The mass loss graph and evaporation rate graph of the hydrogel under 0.5, 1, 1.5 and 2 sun illumination intensities are shown in an exemplary embodiment of the present application; wherein, Figure 13 Figure (a) shows GBAAM1Zr 4.5 Mass loss diagram of hydrogel under 0.5, 1, 1.5 and 2 suns of light intensity, Figure 13 Figure (b) shows GBAAM1Zr 4.5 Graph of evaporation rates of hydrogels under 0.5, 1, 1.5, and 2 suns. Figure 12 ,GBAAM1Zr 4.5 The evaporation rates of the hydrogel under 0.5, 1, 1.5, and 2 suns of illumination were 0.880, 1.762, 2.165, and 2.749 kg·m, respectively. -2 ·h -1 As the intensity of sunlight increases, GBAAM1Zr 4.5 The surface temperature of the hydrogel increases under illumination, which in turn leads to an increase in the evaporation rate.

[0132] In addition, the evaporation rate of GAMZr hydrogel was 1.473 kg·m under 1 sun intensity. -2 ·h -1 , under an intensity of 1.5 suns, the evaporation rate is 1.53 kg·m -2 ·h -1Under the illumination intensity of 2 suns, the evaporation rate reached 1.63 kg·m -2 ·h -1 ,GBAAM1Zr 4.5 The evaporation rate of the hydrogel is better than that of GAMZr hydrogel.

[0133] Figure 14 The infrared images of the hydrogel evaporator under different light intensities after evaporation for 1 hour. Figure 14 Within 1 h of irradiation, the corresponding GBAAM1Zr 4.5 The surface temperature of the hydrogel is stable at 32.8 ℃, 39.9 ℃, 48.4 ℃ and 55.9 ℃ respectively. It can be seen that GBAAM1Zr 4.5 It has excellent light-to-heat conversion performance. 4.5 The excellent photothermal conversion performance is due to the excellent light absorption effect and long light wave absorption of MXene nanosheets in the solar spectrum range, and the ability to quickly convert the absorbed light energy into heat energy; secondly, GBAAM1Zr 4.5 The hydrogel has a gradient wettability structure, and its hierarchical porous structure is also conducive to the production of steam.

[0134] In summary, according to the above test results, MXene has excellent photothermal conversion performance and GBAAM1Zr 4.5 The unique gradient wettability structure enables the photoevaporator developed in this paper to have an excellent vapor generation rate.

[0135] (IV) Photocatalytic sterilization ability

[0136] Furthermore, the following is a 4.5 The photocatalytic bactericidal ability of the hydrogel was tested:

[0137] In this experiment, in order to study GBAAM1Zr 4.5 The photocatalytic bactericidal ability of the hydrogel was tested using Escherichia coli as a representative. 4.5 Photocatalytic bactericidal ability of hydrogels. Figure 15 This is a diagram of an experimental setup for a photocatalytic sterilization test on Escherichia coli according to an exemplary embodiment of the present application; Figure 16 An exemplary embodiment of the present application shows the photocatalytic inactivation effect of Escherichia coli without hydrogel (under the illumination intensity of one sun); Figure 17 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The photocatalytic inactivation effect of the hydrogel under one sun's light intensity; Figure 18 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5Image of the photocatalytic inactivation of Escherichia coli by hydrogel under dark conditions. Figure 19 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 Bacterial performance of the hydrogel over ten consecutive test cycles in a cyclic photocatalytic system.

[0138] in, Figure 16 Figure (b1) shows the GBAAM1Zr-free state at 0 min under one solar illumination intensity. 4.5 The effect of hydrogel's photocatalytic inactivation of Escherichia coli. Figure 16 Figure (b2) shows the 60-min time point without GBAAM1Zr 4.5 Image of the photocatalytic inactivation of Escherichia coli by hydrogel; Figure 17 Figure (b1) shows GBAAM1Zr 4.5 The inactivation effect of the hydrogel on E. coli at 0 min under the irradiation of one sun intensity. Figure 17 Figure (b2) shows GBAAM1Zr 4.5 The inactivation effect of the hydrogel on E. coli at 20 minutes under the intensity of sunlight. Figure 17 Figure (b3) shows GBAAM1Zr 4.5 The inactivation effect of the hydrogel on E. coli at 40 minutes under the intensity of sunlight. Figure 17 Figure (b4) shows GBAAM1Zr 4.5 The inactivation effect of the hydrogel on E. coli at 60 minutes under the intensity of one sun; Figure 18 The middle (a1) figure is GBAAM1Zr 4.5 The inactivation effect of hydrogel on E. coli at 0 min under dark conditions. Figure 18 The middle (a2) figure is GBAAM1Zr 4.5 Graph showing the inactivation effect of E. coli by the hydrogel at 60 minutes under dark conditions.

[0139] Specifically, use Figure 15 The device shown performs GBAAM1Zr 4.5 The experiment of hydrogel photocatalytic sterilization, further, in order to explore the GBAAM1Zr 4.5 The inactivation effect of the hydrogel on Escherichia coli and whether the GBAAM1Zr 4.5 The effect of hydrogel on the inactivation of Escherichia coli. First, the hydrogel without GBAAM1Zr 4.5 The E. coli suspension in the hydrogel was placed under a xenon lamp for 60 min, and the results were as follows: Figure 16As shown in the figure, it can be seen that the number of colonies in the blank control experiment after 60 minutes is slightly smaller than the initial number of colonies, indicating that light irradiation can only cause a weak bactericidal effect on Escherichia coli. 4.5 The E. coli suspension in the hydrogel was placed under a xenon lamp for 60 minutes, and the results were as follows: Figure 17 As shown in the figure, it can be seen that after 40 minutes of irradiation under the xenon lamp, the number of E. coli decreased significantly, and after 60 minutes of irradiation, almost all E. coli were inactivated, indicating that GBAAM1Zr 4.5 The hydrogel has excellent photocatalytic bactericidal properties and can achieve efficient photocatalytic sterilization in a shorter time.

[0140] Furthermore, in order to further confirm GBAAM1Zr 4.5 Photocatalytic bactericidal properties of hydrogels, GBAAM1Zr 4.5 The hydrogel was placed in a dark environment and sterilized again. Figure 18 As shown in the figure, the sterilization effect in the dark environment is not significant. Therefore, by comparing with the blank control experiment, it can be seen that the light conditions are more effective in GBAAM1Zr 4.5 GBAAM1Zr plays an important role in the sterilization process of hydrogels. 4.5 The excellent bactericidal performance of the hydrogel is mainly attributed to its photocatalytic activity.

[0141] In addition, in order to verify the GBAAM1Zr 4.5 The recyclability of hydrogel photocatalytic sterilization, this paper also 4.5 The hydrogel was sterilized 10 times according to the same test cycle. The final experimental results are as follows: Figure 19 As shown, refer to Figure 19 It can be proved that after 10 consecutive sterilization cycles, GBAAM1Zr 4.5 The hydrogel still maintains excellent photocatalytic bactericidal activity, showing that GBAAM1Zr 4.5 The hydrogel also exhibits long-term cyclic stability.

[0142] In summary, according to the above test results, it can be seen that GBAAM1Zr 4.5 The hydrogel has excellent photocatalytic sterilization effect and also has cyclic stability that allows it to perform photocatalytic sterilization for a long time while still maintaining the photocatalytic sterilization effect.

[0143] (5) Salt resistance and acid and alkali resistance

[0144] Furthermore, the following is a 4.5 The salt resistance and acid and alkali resistance of the hydrogel are tested:

[0145] First, to prove that GBAAM1Zr 4.5 To determine the durability during long-term seawater evaporation, a continuous 12 h evaporation experiment was conducted using simulated seawater with a salt concentration of 3.5 wt% under one sun intensity. Figure 20 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The effect diagram of the hydrogel durability experiment, among which, Figure 20 The middle (a) picture is GBAAM1Zr 4.5 The effect of the evaporator in 3.5 wt% NaCl solution for 12 hours. Figure 20 The middle (b) picture shows GBAAM1Zr 4.5 Rendering of the evaporator's self-cleaning capability.

[0146] Please refer to Figure 20 , no obvious salt deposition appeared on the surface of the evaporator, and only some salt deposition appeared in the insulation layer near the evaporator, which showed that the evaporator showed excellent self-cleaning properties, and the gradient wettability structure of the hydrogel played a vital role in preventing salt accumulation. The hydrogel with gradient wettability structure can directionally pump liquid to the photothermal conversion layer. During the evaporation process, the salt tends to dissolve at the hydrophilic end and diffuse back into the water body through the concentration gradient, while the salt at the hydrophobic end is difficult to crystallize and deposit due to the high evaporation rate, which significantly reduces the problem of surface salt blockage and ensures that the evaporation rate of the evaporator will not be affected by surface salt deposition under long-term evaporation. In order to further verify the GBAAM1Zr 4.5 The self-cleaning performance of the evaporator is tested by placing the evaporator in simulated seawater and placing a certain amount of NaCl solid on its surface. Figure 20 As can be seen in Figure (b), in the absence of sunlight at night, the salt particles will automatically dissolve after 3 hours, achieving self-cleaning of the evaporator and ensuring long-term normal operation of the evaporator.

[0147] Furthermore, in order to study the salt tolerance of the evaporator in a high-salinity environment, this paper carried out evaporation experiments under different salt concentrations.

[0148] Figure 21 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The effect diagram of the hydrogel's salt resistance experiment. Figure 21 The middle (a) picture is GBAAM1Zr 4.5 Evaporation rate diagram of the evaporator at different salinities, Figure 21 The middle (b) picture shows GBAAM1Zr 4.5 Please refer to the cyclic solar evaporation test results. Figure 21When conducting evaporation experiments at salt concentrations of 5 wt%, 10 wt%, and 20 wt%, the evaporation rate of the hydrogel with a gradient wettability structure decreases continuously with the increase of salt concentration. When the concentration reaches 20 wt%, the evaporation rate of the evaporator can still reach 1.155 kg·m -2 ·h -1 This shows that the evaporator can still operate effectively and stably in solutions with salt concentrations as high as 20 wt%. In addition, this paper also conducted 5 cyclic evaporation experiments, each cycle lasting 2 hours, and the evaporator was rinsed with distilled water after each cycle. Figure 21 As can be seen from Figure (b), the evaporation performance of each cycle is comparable, which indicates that the evaporator can maintain a relatively stable evaporation rate.

[0149] In order to further study GBAAM1Zr 4.5 The acid and alkali resistance of the hydrogel was tested. In this experiment, acid and alkali solutions (pH = 1-13) were used to simulate polluted wastewater and the hydrogel was immersed for 7 days. Figure 22 An exemplary embodiment of the present application shows GBAAM1Zr after being immersed in acid, alkali and salt solution for 7 days. 4.5 Photo of hydrogel. Please refer to Figure 22 ,GBAAM1Zr 4.5 The hydrogel remained intact in acidic, neutral and alkaline solutions with a pH range of 1-10 without disintegration, which may be due to the cross-linking of GBAAM1Zr 4.5 The hydrogel formed a high-density three-dimensional network structure, which further improved the stability of the hydrogel; however, GBAAM1Zr 4.5 The hydrogel was destroyed in extremely alkaline solution, which was mainly attributed to the destruction of the cross-linked network of N,N'-methylenebisacrylamide.

[0150] (6) Outdoor evaporation experiment of hydrogel evaporator

[0151] Furthermore, outdoor photothermal tests were conducted to test the GBAAM1Zr 4.5 The practical application performance of the hydrogel optical evaporator is discussed. Therefore, in this experiment, the East China Sea seawater was selected to react with GBAAM1Zr 4.5 The hydrogel photoevaporator was tested for outdoor photothermal evaporation in all weather conditions.

[0152] Figure 23 A physical diagram showing an outdoor evaporation device is provided as an exemplary embodiment of the present application. Figure 24 GBAAM1Zr is shown as an exemplary embodiment of this application. 4.5 The effect diagram of the hydrogel outdoor evaporation experiment, among which, Figure 24Figure (a) shows the curve of solar temperature and evaporation rate changes outdoors in one day. Figure 24 Figure (b) shows GBAAM1Zr 4.5 The results of 15 cycles of evaporation experiments under one illumination in seawater, Figure 24 Figure (c) is a comparison of ion concentrations before and after seawater desalination.

[0153] from Figure 24 As shown in Figure (a), the evaporation rate of the evaporator shows an overall upward trend with the increase of light and heat intensity, reaching a peak value between 11:00 and 14:00, with a maximum evaporation rate of 1.738 kg·m -2 ·h -1 At the same time, in order to investigate the practical application of GBAAM1Zr 4.5 To test the stability of the water, a 15-cycle evaporation experiment was conducted on real East China Sea water under one sun intensity. Figure 24 As shown in Figure (b), GBAAM1Zr 4.5 The evaporator showed good evaporation stability. In addition, in order to verify whether the fresh water obtained by solar desalination meets the drinking water standards, the Na + , K + , Ca 2+ and Mg 2+ The concentrations of four major ions were tested. Figure 24 As shown in Figure (c), the concentrations of the four main ions in the evaporated fresh water are far below the WHO standard. This shows that the solar evaporator prepared in this paper can effectively desalinate seawater to obtain fresh water suitable for human consumption.

[0154] Based on the above test results, it can be seen that the use of East China Sea water to GBAAM1Zr 4.5 The hydrogel was tested for desalination of seawater and the Na + , K + , Ca 2+ and Mg 2+ The concentrations of four major ions were tested and found to be far below the WHO standards, meeting the drinking water standards.

[0155] In summary, it can be seen that the preparation method provided in this embodiment has the following advantages:

[0156] (1) GBAAM1Zr 4.5 Hydrogels do not require any external energy and can achieve gelation in a very short time, which has the advantages of saving time, being low-carbon and environmentally friendly.

[0157] (2) After the introduction of acrylic acid and cross-linking agent N, N'-methylenebisacrylamide, GBAAM1Zr4.5 The pore structure of the hydrogel was improved, and a gradient wettability structure was formed, and the water transport capacity was enhanced.

[0158] (3) Under one sun intensity, in 3.5 wt% NaCl solution, GBAAM1Zr 4.5 The evaporation rate of the hydrogel is 1.762 kg·m -2 ·h -1 , the evaporation rate is 4.14 times that of pure water.

[0159] (4) Thanks to the excellent photocatalytic performance of MXene nanosheets, GBAAM1Zr 4.5 The hydrogel exhibited excellent photocatalytic bactericidal properties, achieving a 99% sterilization rate against E. coli within one hour. After 10 sterilization cycles, the sterilization rate showed no significant decrease, demonstrating the surface's excellent cyclic sterilization effectiveness.

[0160] (5) GBAAM1Zr 4.5 The hydrogel has excellent salt tolerance. In a 20 wt% NaCl solution, under one sun intensity, it still has a salt resistance of 1.155 kg·m -2 ·h -1 evaporation rate.

[0161] (6) Using East China Sea water to analyze GBAAM1Zr 4.5 The hydrogel was tested for desalination of seawater and the Na + , K + , Ca 2+ and Mg 2+ The concentrations of four major ions were tested and found to be far below the WHO standards, meeting the drinking water standards.

[0162] The method provided in this embodiment can quickly form a gel structure in a short period of time by initiating in situ free radical polymerization at room temperature without the need for external energy input; at the same time, by precisely controlling the diffusion and polymerization order of the reactants, the network structure is guided to be gradually constructed from the bottom up, achieving a spatial gradient distribution of wettability from hydrophilic to hydrophobic. Thanks to this preparation strategy, the obtained hydrogel not only has a hierarchical and orderly pore structure and excellent water transport capacity, but also exhibits excellent photothermal evaporation efficiency and salt tolerance, and can maintain a high evaporation rate in a high-salt environment; in addition, the introduction of MXene materials gives it excellent photocatalytic bactericidal properties, and it still maintains an efficient sterilization effect in multiple rounds of recycling, showing good stability and reusability. This hydrogel shows broad application prospects in the fields of solar-driven seawater desalination, antibacterial purification, etc.

[0163] The second aspect of the present application also provides a hydrogel, which is prepared based on any one of the hydrogel preparation methods in the above embodiments. The hydrogel is a hydrogel with a three-dimensional network structure, wherein, when viewed from the upper and lower directions from the opening to the bottom of the mold, the hydrogel has a gradient wettability structure, and MXene material is evenly distributed inside the hydrogel.

[0164] The third aspect of the present application further provides an application of a hydrogel, wherein the hydrogel is prepared based on any one of the hydrogel preparation methods in the above embodiments, and the hydrogel is used for seawater desalination and seawater purification.

[0165] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing a hydrogel, characterized in that: The hydrogel preparation method comprises: An initial precursor solution is prepared using gelatin, acrylamide, N,N'-methylenebisacrylamide, and a pre-prepared MXene material; wherein the MXene material is uniformly dispersed in the initial precursor solution; Acrylic acid and ZrCl4 are added to the initial precursor solution and stirred for a first preset time to obtain a target precursor solution; wherein the ZrCl4 is hydrolyzed in the initial precursor solution to release Zr 4+ ; Ammonium persulfate is added to the target precursor solution, stirred for a second preset time, and then transferred to a mold to form a hydrogel at room temperature; wherein the ammonium persulfate decomposes in the target precursor solution to generate free radicals, which initiate a polymerization reaction of the acrylic acid, the acrylamide, and the N,N'-methylenebisacrylamide, preferentially forming an acrylic acid-acrylamide copolymer network at the bottom of the mold; as the polymerization reaction continues, the acrylic acid gradually copolymerizes with the gelatin, gradually forming a polyacrylic acid-gelatin copolymer network at the top of the mold, so that the finally formed hydrogel exhibits a gradient wettability structure that gradually transitions from hydrophilicity to hydrophobicity along the bottom-up direction of the mold, and the MXene material is evenly distributed inside the hydrogel; The initial precursor solution is prepared using gelatin, acrylamide, N,N'-methylenebisacrylamide, and pre-prepared MXene material, comprising: Adding a first specified amount of MXene material to deionized water, and ultrasonically vibrating for a third preset time to uniformly disperse the MXene material in the deionized water to form a stable suspension; Adding gelatin to the suspension, and heating and stirring at 45-55° C. for a fourth preset time, so that the gelatin is completely dissolved and fully mixed with the suspension to form a uniform first mixed liquid; adding acrylamide and N,N'-methylenebisacrylamide to the first mixed solution to form a second mixed solution; The second mixed solution is stirred in a water bath at 55-65° C. for a fifth preset time, and then cooled to room temperature to obtain the initial precursor solution.

2. The method for preparing a hydrogel according to claim 1, wherein Under the synergistic effect of the gradient wettability structure and the MXene material, the evaporation rate of the hydrogel reaches 1.762 kg·m under the illumination of one sun. -2 ·h -1 , the photocatalytic sterilization ability reaches 99%.

3. The method for preparing a hydrogel according to claim 1, wherein: The hydrogel preparation method further comprises: The gelation speed and mechanical properties of the hydrogel are controlled by controlling the addition amount of the MXene material and / or the addition amount of the ZrCl4.

4. The method for preparing a hydrogel according to claim 1, wherein: The hydrogel preparation method further comprises: The wettability gradient of the formed hydrogel is regulated by controlling the added amounts of the acrylamide and the N,N'-methylenebisacrylamide.

5. The method for preparing a hydrogel according to claim 1, wherein: The preparation process of the pre-prepared MXene material includes: preparing an etching solution containing HF using an HCl solution and LiF; Adding Ti3AlC2 to the etching solution to selectively remove Al atoms using HF to generate a black product; wherein the black product is Ti3C2 with a layered structure and functional groups Tx are formed on the surface of the Ti3C2; Washing and centrifuging the black product until the pH value of the washing solution is greater than 6; The black product after washing and centrifugation is freeze-dried for a sixth preset time period to obtain the MXene material.

6. The method for preparing a hydrogel according to claim 2, wherein: The step of adding acrylic acid and ZrCl4 to the initial precursor solution and stirring for a first preset time to obtain a target precursor solution comprises: 4 ml of acrylic acid and a second specified amount of ZrCl 4 were added to the initial precursor solution and stirred for 30 minutes to obtain the target precursor solution.

7. A hydrogel, characterized in that The hydrogel is prepared based on the hydrogel preparation method according to any one of claims 1 to 6; the hydrogel is a hydrogel with a three-dimensional network structure; wherein, The hydrogel exhibits a gradient wettability structure that gradually transitions from hydrophilicity to hydrophobicity along the bottom-up direction of the mold, and the MXene material is evenly distributed inside the hydrogel.

8. The hydrogel according to claim 7, characterized in that Under the synergistic effect of the gradient wettability structure and the MXene material, the evaporation rates of the hydrogel under irradiation with 0.5, 1, 1.5, and 2 sun intensities are 0.880, 1.762, 2.165, and 2.749 kg·m, respectively. -2 ·h -1 .

9. An application of a hydrogel, characterized in that: The hydrogel is prepared based on the hydrogel preparation method according to any one of claims 1 to 6, and the hydrogel is used for seawater desalination and seawater purification.

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