Double-layer composite nanofiber membrane with light-heat conversion function and preparation method thereof

Abstract

This invention provides a bilayer composite nanofiber membrane with photothermal conversion function and its preparation method, which is composed of a self-floating polymer fiber layer and a composite nanofiber layer. The composite nanofiber layer includes a three-dimensional porous thermoplastic polymer nanofiber membrane formed by cross-linking thermoplastic polymer nanofibers, and photothermal nanoparticles completely encapsulated within the thermoplastic polymer nanofibers. This bilayer composite nanofiber membrane possesses good self-floating properties, excellent mechanical properties, a fast water transport rate, and excellent photothermal conversion performance. This invention prepares an integrated photothermal composite nanofiber, effectively solving the problem of easy detachment of particulate coating materials. Furthermore, the bilayer membrane structure is simple, and using nanofibers as the raw material for the photothermal conversion layer reduces heat loss.

Description

Technical Field

[0001] This invention relates to the field of seawater desalination fiber membrane material preparation technology, and in particular to a bilayer composite nanofiber membrane with photothermal conversion function and its preparation method. Background Technology

[0002] Since approximately 71% of the Earth's surface is covered by oceans, developing seawater desalination technology is considered the most promising way to address the global shortage of freshwater resources. However, traditional seawater desalination methods, such as reverse osmosis, cryogenic distillation, and multi-stage flash evaporation, still have many limitations, including high equipment construction and maintenance costs, demanding operating conditions, huge energy consumption, and environmental pollution, which do not align with national sustainable development strategies. Solar energy, on the other hand, has attracted widespread attention due to its abundant resources, wide coverage, renewability, low cost, and high energy efficiency. Seawater desalination membranes, in particular, have shown great promise due to their low cost and excellent evaporation performance. However, their poor mechanical properties, poor self-floating performance, large heat loss, and complex structural design hinder their practical application.

[0003] Patent CN115893556A discloses a photothermal seawater desalination composite film with a double-layer structure, its preparation method, and its application. Two-dimensional MXene nanomaterials are obtained by hydrothermal-assisted etching of the precursor MAX phase. Then, using copper chloride, bismuth chloride, and thiourea as precursors, a Cu3BiS3 / MXene nanocomposite material is synthesized based on the two-dimensional MXene nanomaterials using a solvothermal method. Next, the Cu3BiS3 / MXene nanocomposite material is dispersed and mixed with sodium alginate to obtain a homogeneous solution. Subsequently, a cross-linking coating process is used to coat the Cu3BiS3 / MXene homogeneous solution onto basalt fiber cloth, forming a bismuth-sulfur copper / MXene / basalt composite film with a rough surface and a double-layer structure. However, this method suffers from a technical defect: the photothermal conversion layer is easily damaged, thus significantly affecting the seawater desalination effect.

[0004] In view of this, it is necessary to design an improved bilayer composite nanofiber membrane with photothermal conversion function and its preparation method to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a bilayer composite nanofiber membrane with photothermal conversion function and its preparation method.

[0006] To achieve the above-mentioned objectives, the present invention provides a bilayer composite nanofiber membrane with photothermal conversion function, which is composed of a self-floating polymer fiber layer and a composite nanofiber layer.

[0007] The composite nanofiber layer includes a three-dimensional porous thermoplastic polymer nanofiber membrane formed by cross-linking thermoplastic polymer nanofibers with a diameter of 300-500 nm, and photothermal nanoparticles with a particle size of 30-50 nm that are completely encapsulated inside the thermoplastic polymer nanofibers.

[0008] The thickness ratio of the polymer fiber layer to the composite nanofiber layer is (100~150):1, and the pore size ratio is (50~100):1.

[0009] As a further improvement of the present invention, the polymer fiber layer is a PP fiber layer; the thermoplastic polymer nanofiber is a PVA-co-PE nanofiber.

[0010] As a further improvement of the present invention, the photothermal nanoparticles are one or more combinations of cesium tungsten bronze nanoparticles, perovskite nanoparticles, carbon-based nanoparticles, and inorganic semiconductor nanoparticles.

[0011] As a further improvement of the present invention, the crosslinking agent for the crosslinking reaction is glutaraldehyde.

[0012] As a further improvement of the present invention, the photothermal nanoparticles are modified by reacting with metal alkoxides or epoxy compounds to give their surface active groups.

[0013] To achieve the above-mentioned objectives, the present invention also provides a method for preparing the above-mentioned bilayer composite nanofiber membrane with photothermal conversion function, which includes the following steps:

[0014] S1, Photothermal nanoparticle pretreatment: Photothermal nanoparticles with a particle size of 30~50nm are pretreated to obtain photothermal nanoparticles with active groups on the surface.

[0015] S2, Preparation of composite nanofibers: 5-10% by mass of thermoplastic polymer masterbatch is added to a mixed solvent of water and alcohol, and heated and stirred in a water bath at 60-100℃ to obtain a precursor solution. Then, the pretreated photothermal nanoparticles are uniformly dispersed in the precursor solution. Finally, the uniformly mixed composite solution is poured into cold water to destroy its solvent system, precipitating the nanoparticle / thermoplastic polymer nanofiber composite. After drying and pulverizing, a composite powder with a particle size of 300-500 nm is prepared. The composite powder is mixed uniformly with cellulose acetate butyrate, and melt-spun to obtain virgin fibers. Then, the cellulose acetate butyrate is removed to obtain island-shaped composite nanofibers with a diameter of 300-500 nm.

[0016] S3, Preparation of composite nanofiber suspension: 1.5%-3.5% by mass of composite nanofibers are placed in a mixed solvent of water and alcohol, and the mixture is stirred at high speed to prepare a nanofiber suspension. Finally, a crosslinking agent is added to carry out a crosslinking reaction to obtain the composite nanofiber suspension.

[0017] S4, Preparation of bilayer composite nanofiber membrane: The composite nanofiber suspension is coated on the polymer fiber layer, and the solvent is removed to obtain a bilayer composite nanofiber membrane.

[0018] As a further improvement of the present invention, the ratio of the photothermal nanoparticles to the thermoplastic polymer masterbatch is (5~10):100.

[0019] As a further improvement of the present invention, the mass ratio of the crosslinking agent to the composite nanofiber is (20~35):100.

[0020] As a further improvement of the present invention, the pretreatment process of step S1 is as follows: using ethanol as a solvent, 30% to 50% by mass of photothermal nanoparticles are poured in, and 3% to 5% by mass of modifier metal alkoxide or epoxy compound is added. The mixture is stirred at 60 to 100°C for 4 to 6 hours, and then dried to obtain photothermal nanoparticles with active groups on the surface.

[0021] As a further improvement of the present invention, the alcohol in the mixed solvent is isopropanol.

[0022] As a further improvement of the present invention, the coating process in step S4 is: spraying.

[0023] The beneficial effects of this invention are:

[0024] 1. The bilayer composite nanofiber membrane with photothermal conversion function provided by this invention prepares an integrated photothermal composite nanofiber in which photothermal nanoparticles are completely encapsulated inside the fiber, effectively solving the problem of easy detachment of particle coating materials in the prior art. Moreover, the bilayer membrane structure is simple, and the use of nanofibers as the raw material for the photothermal conversion layer reduces heat loss.

[0025] 2. The bilayer composite nanofiber membrane with photothermal conversion function provided by this invention not only solves the problem of poor mechanical properties in seawater desalination membranes, but also has advantages such as simple structure, excellent self-floating performance, and low heat loss, and has great application prospects in the field of seawater desalination.

[0026] 3. The bilayer composite nanofiber membrane with photothermal conversion function provided by this invention achieves complete encapsulation of photothermal nanoparticles and preparation of composite nanofibers through a series of continuous morphological changes of thermoplastic nanofibers, masterbatch, liquid macromolecules in a specific solvent system, precipitated composite fibers, composite powder, and island-structured composite nanofibers. This realizes the integrated preparation of photothermal nanoparticles and nanofibers. Furthermore, by pretreating the photothermal nanoparticles, the interaction between active groups and PVA-co-PE is utilized to increase the number of nanoparticles that are completely encapsulated and the uniformity of dispersion, thereby achieving complete and uniform encapsulation of photothermal nanoparticles by nanofibers. Attached Figure Description

[0027] Figure 1 Electron micrograph of the composite nanofibers provided in Example 1 of the present invention (unit: nm ).

[0028] Figure 2 Electron micrograph (EM) image of the bilayer composite nanofiber membrane provided in Example 1 of this invention (unit: μm).

[0029] Figure 3 This is an experimental diagram of the self-floating of the double-layer composite nanofiber membrane provided in Example 1 of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0032] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0033] This invention provides a method for preparing a bilayer composite nanofiber membrane with photothermal conversion function, comprising the following steps:

[0034] S1, Photothermal nanoparticle pretreatment: Photothermal nanoparticles with a particle size of 30~50nm are pretreated to obtain photothermal nanoparticles with active groups on the surface.

[0035] S2, Preparation of composite nanofibers: 5-10% by mass of thermoplastic polymer masterbatch is added to a mixed solvent of water and alcohol, and heated and stirred in a water bath at 60-100℃ to obtain a precursor solution. Then, the pretreated photothermal nanoparticles are uniformly dispersed in the precursor solution. Finally, the uniformly mixed composite solution is poured into cold water to destroy its solvent system, precipitating the nanoparticle / thermoplastic polymer nanofiber composite. After drying and pulverizing, a composite powder with a particle size of 300-500 nm is prepared. The composite powder is mixed uniformly with cellulose acetate butyrate, and melt-spun to obtain virgin fibers. Then, the cellulose acetate butyrate is removed to obtain island-shaped composite nanofibers with a diameter of 300-500 nm.

[0036] S3, Preparation of composite nanofiber suspension: 1.5%-3.5% by mass of composite nanofibers are placed in a mixed solvent of water and alcohol, and the mixture is stirred at high speed to prepare a nanofiber suspension. Finally, a crosslinking agent is added to carry out a crosslinking reaction to obtain the composite nanofiber suspension.

[0037] S4, Preparation of bilayer composite nanofiber membrane: The composite nanofiber suspension is coated on the polymer fiber layer, and the solvent is removed to obtain a bilayer composite nanofiber membrane.

[0038] Preferably, the ratio of the photothermal nanoparticles to the thermoplastic polymer masterbatch is (5~10):100.

[0039] Preferably, the mass ratio of the crosslinking agent to the composite nanofiber is (20~35):100.

[0040] Preferably, the pretreatment process in step S1 is as follows: using ethanol as a solvent, pouring in 30%~50% by mass of photothermal nanoparticles, adding 3%~5% by mass of modifier metal alkoxide or epoxy compound, stirring at 60~100℃ for 4-6 hours, and then drying to obtain photothermal nanoparticles with active groups on the surface.

[0041] Preferably, the alcohol in the mixed solvent is isopropanol.

[0042] Example 1

[0043] Example 1 provides a method for preparing a bilayer composite nanofiber membrane with photothermal conversion function, comprising the following steps:

[0044] S1, Screening of photothermal nanopowders / particles and thermoplastic polymers: Selecting Cs with a particle size of 30~50nm. X WO3NPs (cesium tungsten bronze nanoparticles) were selected as photothermal nanoparticles, with PVA- co -PE (ethylene-vinyl alcohol copolymer) masterbatch as a thermoplastic polymer masterbatch;

[0045] The photothermal nanoparticles were modified and pretreated as follows:

[0046] Using ethanol as a solvent, 40% by mass of photothermal nanoparticles were poured in, and 5% by mass of a modifier metal alkoxide or epoxy compound was added. The mixture was stirred at 80°C for 5 hours, and then dried to obtain photothermal nanoparticles with active groups on the surface.

[0047] The modifier is one or a combination of propylene oxide, alkyl or aryl isocyanates, metal alkoxides, epoxy compounds, etc.

[0048] S2, Cs X WO3 / PVA- co Preparation of PE composite nanofibers:

[0049] S21, PVA- in (S1) co -PE nanofiber masterbatch is added to a mixed solvent of deionized water and isopropanol (volume ratio 3:1), PVA- co - PE nanofiber masterbatch accounts for 6% of the mass of the mixed solvent to obtain a solid-liquid mixture; then the solid-liquid mixture is placed in an 80°C water bath and stirred until PVA- co -PE nanofiber masterbatch was completely dissolved to obtain a precursor solution for Cs x Wo3 nanoparticle modification pretreatment, based on the active groups modified on the nanoparticle surface, enhances dispersion performance, utilizing active groups and PVA- co The interactions between PE particles can also increase the number of nanoparticles that are completely encapsulated, followed by high-speed stirring of PVA using a high-speed disperser. co -PE precursor solution simultaneously with Cs x Wo3 nanoparticles are relatively uniformly dispersed within it (PVA- co -The mass ratio of PE nanofiber masterbatch to photothermal nanoparticles is 100:8). Then, the uniformly mixed Cs x Wo3 / PVA- co - Pouring the PE composite solution into cold water disrupts its solvent system, precipitating Cs. x Wo3 / PVA- co -PE composite, and dried at 60–100°C. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) x Wo3 / PVA- co After the PE composite is completely dried, it is pulverized into powder with a particle size of 300~500nm using a pulverizer.

[0050] S22, the obtained Cs x Wo3 / PVA- co- PE composite powder and cellulose acetate butyrate (CAB) are mixed evenly at a mass ratio of 1.5:9.5, and then fed into the hopper of a twin-screw extruder for melt extrusion and stretching to obtain virgin fibers. Then, acetone is used to remove the CAB from the virgin fibers to obtain Cs fibers with a diameter of 300~500nm. x Wo3 / PVA- co -PE composite nanofibers. Please refer to [link / reference]. Figure 1 As shown, photothermal nanoparticles are uniformly encapsulated inside composite nanofibers.

[0051] S3, Cs X WO3 / PVA- co Preparation of PE / GA composite nanofiber suspension: The composite nanofibers in (S2) were placed in a mixed solution of deionized water and isopropanol (volume ratio 3:1), with the mass of the composite nanofibers being 3.5% of the mass of the mixed solvent. The solid-liquid mixture was poured into a high-speed stirrer and stirred at a speed of 6000–10000 rpm for 1.5–2.5 min to obtain Cs. x Wo3 / PVA- co A PE composite nanofiber suspension was prepared, and then glutaraldehyde (GA) was added to the composite nanofiber suspension, with GA accounting for 20% of the composite nanofiber mass. After magnetic stirring, the cross-linking reaction was carried out for 3-4 hours to obtain Cs. X WO3 / PVA- co -PE / GA composite nanofiber suspension.

[0052] S4, Cs X WO3 / PVA- co Preparation of PE / GA / PP bilayer composite nanofiber membrane: The suspension in (S3) was poured into an atomizing spray gun and atomized. A piece of PP nonwoven fabric with a size of 10×10 cm was cut and fixed on the surface of a glass plate. It was then evenly sprayed onto the PP substrate. After the water and isopropanol had completely evaporated, Cs was obtained by peeling. X WO3 / PVA- co -PE / GA / PP double-layer composite nanofiber membrane.

[0053] Please see Figure 2 As shown, the PP fiber layer and the CsXWO3 / PVA-co-PE / GA composite nanofiber layer are tightly bonded together, with the composite nanofibers distributed on the surface of the PP fiber layer and in the three-dimensional porous structure, achieving interlocking composite.

[0054] In this Example 1, a CsXWO3 / PVA-co-PE / GA / PP bilayer composite nanofiber membrane was prepared using PP nonwoven fabric as the substrate. It has good self-floating properties, excellent mechanical properties, fast water delivery rate and excellent photothermal conversion performance.

[0055] In the photothermal conversion performance test, under sunlight irradiation, in the dry state, Cs X WO3 / PVA- co The surface temperature of the PE / GA / PP bilayer composite nanofiber membrane reaches 103.6℃, ​​and the evaporation rate in the hydrated state is as high as 2.80 kg. . m -2. h -1 Its photothermal conversion efficiency reaches 92%.

[0056] Self-floating test: Please refer to Figure 3 As shown, it can be seen that selecting PP substrate as the floating layer gives the CsXWO3 / PVA-co-PE / GA / PP double-layer composite nanofiber membrane excellent self-floating performance and flexibility.

[0057] Comparative Example 1

[0058] A single-layer PP substrate film was used as a blank control.

[0059] Example 2-3

[0060] The difference from Example 1 is that the mass ratio of the composite nanofibers to the mixed solvent is different in step S3. Everything else is the same as in Example 1 and will not be repeated here.

[0061] In Example 2, the mass of the composite nanofibers was 2.5% of the mass of the mixed solvent;

[0062] In Example 3, the mass of the composite nanofibers was 1.5% of the mass of the mixed solvent.

[0063] Mechanical properties, photothermal conversion properties, and evaporation properties of Examples 1-3 were tested.

[0064] Mechanical property testing method: The flat composite film was cut into 2 × 5 cm samples, and then both ends were fixed on the INSTRON fixture. The tensile strength of the samples was tested at a tensile speed of 0.1 m / min.

[0065] Photothermal conversion performance testing method: The test was conducted under simulated sunlight using a xenon lamp. The composite film was irradiated under the xenon lamp for 10 minutes, and then the illumination was removed. The temperature was recorded simultaneously using infrared imaging.

[0066] Evaporation performance test method: The test was conducted under simulated sunlight with a xenon lamp. The sample was placed in prepared artificial seawater and irradiated with a xenon lamp for 60 minutes. The mass change of the artificial seawater was recorded using an electronic balance, and the temperature change of the sample surface was recorded and analyzed using a Fluke infrared imager.

[0067] The performance test results are shown in Table 1:

[0068]

[0069] The mass ratio of composite nanofibers affects the membrane thickness and pore size of the composite nanofiber layer. As shown in Table 1, increasing the mass ratio of composite nanofibers simultaneously improves the mechanical properties, evaporation performance, and photothermal conversion performance. In other words, the thickness and pore size of the composite nanofiber layer can regulate the mechanical and photothermal conversion performance of the bilayer composite nanofiber membrane.

[0070] Comparative Example 2

[0071] The difference from Example 1 is that in step S1, no photothermal nanoparticle modification pretreatment is performed.

[0072] Comparative Example 2, without any modification to the photothermal nanoparticles, exhibited poor dispersion performance in the precursor solution, easily agglomerating and failing to disperse uniformly. Therefore, the prepared composite powder contained PVA- co -PE polymers are difficult to uniformly coat photothermal nanoparticles. Some are loaded on the surface of polymer powder and are easy to fall off, which leads to easy damage and failure of the photothermal conversion layer.

[0073] Examples 4-5

[0074] The difference from Example 1 is that the mass ratio of glutaraldehyde added in step S3 is different. Everything else is the same as in Example 1, and will not be repeated here.

[0075] In Example 6, glutaraldehyde (GA) accounted for 25% of the mass of the composite nanofibers;

[0076] In Example 7, glutaraldehyde (GA) accounts for 35% of the mass of the composite nanofibers.

[0077] In Examples 1 and 4-5, the mass ratio of the crosslinking agent has an impact: increasing the crosslinking agent can improve Cs. x Wo3 / PVA- co - PE composite nanofibers achieve cross-linking, which to some extent enhances the mechanical tensile properties of the bilayer composite nanofiber membrane.

[0078] Comparative Examples 3-5

[0079] The difference from Examples 1-3 is that no cross-linking reaction is performed in step S3.

[0080] In Comparative Examples 3-5, no cross-linking reaction was used, and the Cs prepared were... X WO3 / PVA- co -PE / PP double-layer composite nanofiber membrane.

[0081]

[0082] As can be seen from the table above, without undergoing a cross-linking reaction, Cs can be directly... X WO3 / PVA- co When PE nanofiber suspension is coated onto PP substrate, its mechanical properties are lower than those of the cross-linked bilayer composite film, indicating that the cross-linking reaction can significantly enhance the mechanical properties of the bilayer composite film.

[0083] In summary, this invention provides a bilayer composite nanofiber membrane with photothermal conversion function and its preparation method, which is composed of a self-floating polymer fiber layer and a composite nanofiber layer. The composite nanofiber layer includes a three-dimensional porous thermoplastic polymer nanofiber membrane formed by the cross-linking reaction of thermoplastic polymer nanofibers, and photothermal nanoparticles completely encapsulated within the thermoplastic polymer nanofibers. This bilayer composite nanofiber membrane possesses good self-floating properties, excellent mechanical properties, a fast water transport rate, and excellent photothermal conversion performance. This invention prepares an integrated photothermal composite nanofiber, effectively solving the problem of easy coating material detachment. Furthermore, the bilayer membrane structure is simple, and using nanofibers as the raw material for the photothermal conversion layer reduces heat loss.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A bilayer composite nanofiber membrane with photothermal conversion function, characterized in that: The bilayer composite nanofiber membrane is composed of a self-floating polymer fiber layer and a composite nanofiber layer. The composite nanofiber layer includes a three-dimensional porous thermoplastic polymer nanofiber membrane formed by cross-linking thermoplastic polymer nanofibers with a diameter of 300-500 nm, and photothermal nanoparticles with a particle size of 30-50 nm that are completely encapsulated inside the thermoplastic polymer nanofibers. The thickness ratio of the polymer fiber layer to the composite nanofiber layer is (100~150):1, and the pore size ratio is (50~100):

1. The thermoplastic polymer nanofibers are PVA-co-PE nanofibers; The photothermal nanoparticles undergo modification pretreatment by reacting with metal alkoxides or epoxy compounds to give their surface active groups. The method for preparing the bilayer composite nanofiber membrane includes the following steps: S1, Photothermal nanoparticle pretreatment: Photothermal nanoparticles with a particle size of 30~50nm are pretreated to obtain photothermal nanoparticles with active groups on the surface. S2, Preparation of composite nanofibers: 5-10% thermoplastic polymer masterbatch by mass is added to a mixed solvent of water and alcohol, and heated and stirred in a water bath at 60-100℃ to obtain a precursor solution. Then, the pretreated photothermal nanoparticles are uniformly dispersed in the precursor solution. Finally, the uniformly mixed composite solution is poured into cold water to destroy its solvent system, precipitating the nanoparticle / thermoplastic polymer nanofiber composite. After drying and pulverizing, a composite powder with a particle size of 300-500 nm is prepared. The composite powder is mixed uniformly with cellulose acetate butyrate, and melt-spun to obtain virgin fibers. Then, the cellulose acetate butyrate is removed to obtain island-shaped composite nanofibers with a diameter of 300-500 nm. S3, Preparation of composite nanofiber suspension: 1.5%-3.5% by mass of composite nanofibers are placed in a mixed solvent of water and alcohol, and the mixture is stirred at high speed to prepare a nanofiber suspension. Finally, a crosslinking agent is added to carry out a crosslinking reaction to obtain the composite nanofiber suspension. S4, Preparation of bilayer composite nanofiber membrane: The composite nanofiber suspension is coated on the polymer fiber layer, and the solvent is removed to obtain a bilayer composite nanofiber membrane.

2. The bilayer composite nanofiber membrane with photothermal conversion function according to claim 1, characterized in that: The polymer fiber layer is a PP fiber layer.

3. The bilayer composite nanofiber membrane with photothermal conversion function according to claim 1, characterized in that: The photothermal nanoparticles are one or more combinations of cesium tungsten bronze nanoparticles, perovskite nanoparticles, carbon-based nanoparticles, and inorganic semiconductor nanoparticles.

4. The bilayer composite nanofiber membrane with photothermal conversion function according to claim 1, characterized in that: The crosslinking agent for the crosslinking reaction is glutaraldehyde.

5. The bilayer composite nanofiber membrane with photothermal conversion function according to claim 1, characterized in that: The mass ratio of the photothermal nanoparticles to the thermoplastic polymer masterbatch is (5~10):

100.

6. The bilayer composite nanofiber membrane with photothermal conversion function according to claim 1, characterized in that: The mass ratio of the crosslinking agent to the composite nanofiber is (20~35):

100.

7. The bilayer composite nanofiber membrane with photothermal conversion function according to claim 1, characterized in that: The pretreatment process in step S1 is as follows: using ethanol as a solvent, 30% to 50% by mass of photothermal nanoparticles are poured in, and 3% to 5% by mass of modifier metal alkoxide or epoxy compound is added. The mixture is stirred at 60 to 100°C for 4 to 6 hours, and then dried to obtain photothermal nanoparticles with active groups on the surface.

8. The bilayer composite nanofiber membrane with photothermal conversion function according to claim 1, characterized in that: In the mixed solvent, the alcohol is isopropanol.

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