Composite nanofiber membrane as well as preparation method and application thereof

Abstract

The invention relates to a composite nanofiber membrane and a preparation method and application thereof, and belongs to the technical field of wearable electromagnetic shielding materials. The preparation method comprises the following steps: dissolving polyacrylonitrile in a solvent, and spinning to obtain a polyacrylonitrile nanofiber membrane; then, the polyacrylonitrile nanofiber membrane is soaked in a trihydroxymethyl aminomethane hydrochloride solution containing dopamine; soaking the dopamine-coated fiber membrane in a mixed solution containing a copper salt or a silver salt, and then soaking the dopamine-coated fiber membrane in a reaction solution to obtain a modified nanofiber membrane; then spraying a dispersion liquid containing a conductive filler onto the modified nanofiber membrane to obtain a conductive filler modified nanofiber membrane; and finally, dissolving polyurethane into a solvent, and spinning by taking the conductive filler modified nanofiber membrane as a receiver to obtain the composite nanofiber membrane. The composite nanofiber membrane has excellent electromagnetic shielding performance, directional perspiration ability, air permeability, photothermal conversion ability, antibacterial property, mechanical strength and flexibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of wearable electromagnetic shielding materials, and specifically relates to a composite nanofiber membrane and a preparation method and application thereof, and in particular relates to the application of the composite nanofiber membrane in wearable electromagnetic shielding materials. Background Art

[0002] With the rapid development and popularization of communication electronic devices and wearable flexible electronic devices, the electromagnetic radiation they generate not only interferes with the normal operation of electronic equipment, but also poses a serious threat to human health. Therefore, there is an urgent need to develop flexible wearable electromagnetic shielding materials to deal with related electromagnetic pollution.

[0003] Electrospinning is a simple and versatile method for preparing nanofibers. Polymer-based nanofiber membranes produced by electrospinning offer advantages such as high flexibility, high porosity, and strong self-support, providing an effective substrate for reducing electromagnetic wave losses within the material. In recent years, various conductive fillers, including carbon-based fillers (carbon nanotubes, graphene, carbon fibers, etc.), metal nanoparticles or nanowires (silver nanoparticles or silver nanowires, etc.), and transition metal carbonitrides (MXene), have been grown or coated onto flexible nanofiber membranes to develop flexible electromagnetic shielding materials. However, existing research primarily focuses on improving the electromagnetic shielding performance of materials, often overlooking the challenges faced by wearable electromagnetic shielding materials during prolonged wear, such as the feeling of stuffiness caused by sweat accumulation and bacterial growth. For example, Yang et al. prepared a stearic acid-modified silver-coated polyacrylonitrile nanofiber membrane (APAN-Ag-SA) (Superhydrophobic and Corrosion-Resistant Electrospun Hybrid Membrane for High-Efficiency Electromagnetic Interference Shielding, ACS Applied Electronic Materials (2021, 3, 2067-2078)). While this membrane has excellent shielding properties, long-term wear causes sweat accumulation, leading to discomfort in hot and humid environments and even bacterial growth. Therefore, developing a composite nanofiber membrane that integrates directional perspiration removal, antibacterial properties, and electromagnetic shielding has greater practical application potential.

[0004] In addition, most electromagnetic shielding nanofiber membranes prepared by electrospinning cannot simultaneously achieve both mechanical strength and flexibility. Summary of the Invention

[0005] To address the existing problem of nanofiber membranes failing to balance electromagnetic shielding performance, wearer comfort (directional perspiration removal), and health protection (antibacterial properties), this invention provides a composite nanofiber membrane, its preparation method, and its application. By simulating plant transpiration and leveraging the synergistic effect of fillers, the composite nanofiber membrane improves the material's electromagnetic shielding performance, moisture absorption and perspiration removal, photothermal conversion capacity, and antibacterial properties. It can be used as a wearable electromagnetic shielding material and has broad application prospects in wearable devices.

[0006] The present invention solves the above technical problems and adopts the following technical solutions.

[0007] In a first aspect, the present invention provides a composite nanofiber membrane comprising a hydrophilic layer, an adhesive layer, and a hydrophobic layer arranged in sequence;

[0008] The material of the hydrophilic layer is polyacrylonitrile modified by nanoparticles, the material of the bonding layer is conductive filler, and the material of the hydrophobic layer is polyurethane.

[0009] Preferably, the nanoparticles include but are not limited to one or more of copper sulfide nanoparticles, silver nanoparticles, and gold nanoparticles.

[0010] Preferably, the conductive filler is MXene, acidified carbon nanotubes or graphene; more preferably, the acidified carbon nanotubes are carbon nanotubes acidified by a mixture of concentrated sulfuric acid and concentrated nitric acid.

[0011] Preferably, the thickness of the hydrophilic layer is 20-32 μm, and the pore size is 0.15-0.85 μm;

[0012] The thickness of the bonding layer is 25-41 μm;

[0013] The hydrophobic layer has a thickness of 22-43 μm and a pore size of 1-4.5 μm.

[0014] In a second aspect, the present invention provides a method for preparing a composite nanofiber membrane, comprising the following steps:

[0015] Step 1: dissolving polyacrylonitrile in a solvent to obtain a polyacrylonitrile spinning solution, and spinning to obtain a polyacrylonitrile nanofiber membrane;

[0016] Step 2: Soaking the polyacrylonitrile nanofiber membrane obtained in step 1 in a tris-hydroxymethylaminomethane hydrochloride (Tris-HCl) solution containing dopamine, shaking the solution, taking it out, and repeatedly rinsing it with deionized water and ethanol alternately, and drying it to obtain a dopamine-coated fiber membrane;

[0017] Step 3: First, soak the dopamine-coated fiber membrane obtained in step 2 in an aqueous solution containing copper salt for 2 to 6 hours, then transfer the soaked dopamine-coated fiber membrane to a mixed solution containing copper salt, add sodium thiosulfate after it is completely soaked, stir evenly and react, take out after the reaction stops, rinse repeatedly with water and ethanol, and dry to obtain a modified nanofiber membrane;

[0018] Alternatively, the dopamine-coated fiber membrane obtained in step 2 is first soaked in an aqueous solution containing silver salt for 2 to 6 hours, and then the soaked dopamine-coated fiber membrane is transferred to a silver ammonia solution for soaking. After it is completely soaked, glucose is added, stirred evenly and reacted. After the reaction stops, the membrane is taken out, rinsed repeatedly with water and ethanol, and dried to obtain a modified nanofiber membrane.

[0019] Step 4: spraying the dispersion containing the conductive filler onto the modified nanofiber membrane prepared in step 3, and drying to obtain the conductive filler modified nanofiber membrane;

[0020] Step 5: dissolving the polyurethane in a solvent to obtain a polyurethane spinning solution, and spinning the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver to obtain a composite nanofiber membrane.

[0021] Preferably, in step 1, the mass fraction of polyacrylonitrile in the polyacrylonitrile spinning solution is 10% to 20%, the solvent is N,N-dimethylformamide, N-methylpyrrolidone or tetrahydrofuran, the spinning voltage is 16 to 17 kV, and the spinning distance is 15 to 18 cm.

[0022] Preferably, in step 2, the concentration of the tris(hydroxymethyl)aminomethane hydrochloride solution containing dopamine is 7.9 mg·mL -1 , pH = 8.5~9, oscillation rate is 60~90 rpm, reaction temperature is 40~60℃, and reaction time is 12~24h.

[0023] Preferably, in step 2, the drying temperature is 338K.

[0024] Preferably, in step 2, the fiber diameter of the dopamine-coated fiber membrane is 150-290 nm.

[0025] Preferably, in step three, the concentration of the aqueous solution containing the copper salt is 0.025~0.175 mol / L, and the copper salt is copper acetate, copper sulfate, copper chloride or copper nitrate. More preferably, the copper salt is copper acetate.

[0026] Preferably, in step three, in the mixed solution containing copper salt, the copper salt is copper acetate, copper sulfate, copper chloride or copper nitrate, the concentration of the copper salt is 0.025~0.175mol / L, the mixed solution is a mixed solution of water and ethylene glycol with a volume ratio of 1:1~1:3, the reaction molar ratio of the copper salt and sodium thiosulfate is 1:1~1:3, the reaction time is 4~7h, and the reaction temperature is 70~180°C; more preferably, the copper salt is copper acetate.

[0027] Preferably, in step three, the concentration of the aqueous solution containing the silver salt is 0.1-0.3 mol / L, and the silver salt is silver nitrate.

[0028] Preferably, in step three, the concentration of the silver ammonia solution is calculated as silver nitrate concentration, the concentration of silver nitrate is 0.1~0.3 mol / L, the reaction molar ratio of silver ions to glucose in the silver ammonia solution is 1:2, the reaction time is 0.5~4h, and the reaction temperature is 70~90°C.

[0029] Preferably, in step three, the dopamine-coated fiber membrane obtained in step two is immersed in an aqueous solution containing copper salt for 2 to 6 hours, dried first, and then the dried dopamine-coated fiber membrane after soaking is transferred to a mixed solution containing copper salt for immersion.

[0030] Preferably, in step three, the dopamine-coated fiber membrane obtained in step two is immersed in an aqueous solution containing silver salt for 2 to 6 hours, dried first, and then the dried dopamine-coated fiber membrane after soaking is transferred to a silver ammonia solution for immersion.

[0031] It should be noted that silver ammonia solution is a prior art preparation process. The preparation process involves first preparing a silver nitrate solution, then adding sodium hydroxide to the silver nitrate solution until the solution becomes turbid. Ammonia water (25% to 28% by weight) is then added dropwise to the solution until the solution becomes clear, thereby obtaining the silver ammonia solution. Because addition is stopped upon clarification during the preparation of the silver ammonia solution, the concentration of the silver ammonia solution is measured in terms of silver nitrate concentration.

[0032] Preferably, in step 4, the concentration of the conductive filler in the dispersion containing the conductive filler is 8-20 mg / L, and the spraying rate is 10-20 ml / h.

[0033] Preferably, in step five, the mass fraction of polyurethane in the polyurethane spinning solution is 20% to 25%; the spinning voltage is 14 to 15 kV, and the spinning distance is 15 to 18 cm; and the solvent is one of N,N-dimethylformamide, N-methylpyrrolidone or tetrahydrofuran.

[0034] In a third aspect, the present invention also provides an application of the above-mentioned composite nanofiber membrane in a wearable electromagnetic shielding material.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The composite nanofiber membrane of the present invention has excellent electromagnetic shielding performance and can be used in smart wearable clothing, thereby reducing radiation exposure of electronic equipment to the human body and protecting human health.

[0037] The composite nanofiber membrane of the present invention has excellent air permeability and directional moisture absorption and perspiration removal capabilities, ensuring comfort during long-term wearing.

[0038] The composite nanofiber membrane of the present invention also has excellent light-to-heat conversion capability, ensuring thermal comfort of the body in a cold environment, and the composite nanofiber membrane has antibacterial capability against Escherichia coli and Staphylococcus aureus, avoiding bacterial growth in a humid environment.

[0039] The composite nanofiber membrane of the present invention combines polyacrylonitrile and polyurethane nanofibers, which not only improves the breaking elongation of the polyacrylonitrile electrospun fiber membrane but also improves the mechanical strength of the polyurethane electrospun fiber membrane, so that the composite nanofiber membrane exhibits good mechanical strength and flexibility, and can still maintain excellent electromagnetic shielding performance after being bent and folded 100 times.

[0040] The preparation method of the composite nanofiber membrane of the present invention can control the loading amount of the conductive filler by adjusting the concentration of the dispersion containing the conductive filler, thereby maintaining the material's excellent moisture absorption and perspiration properties while imparting it with excellent electromagnetic shielding performance.

[0041] The preparation method of the composite nanofiber membrane of the present invention has a simple process and has broad application prospects in wearable devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0043] Figure 1 This is a scanning electron microscope (SEM) image of a cross section of the composite nanofiber membrane prepared in Example 1 of the present invention;

[0044] Figure 2 This is a graph showing the electromagnetic shielding performance of the composite nanofiber membrane prepared in Example 1 of the present invention;

[0045] Figure 3 This is a graph showing the change in water contact angle of the composite nanofiber membrane prepared in Example 1 of the present invention under anti-gravity conditions;

[0046] Figure 4This is the photothermal cycle curve of the composite nanofiber membrane prepared in Example 1 of the present invention;

[0047] Figure 5 These are flat plate test pictures of the composite nanofiber membrane prepared in Example 1 of the present invention, wherein a is a photo of the Escherichia coli colony (without the composite nanofiber membrane), b is a photo of the Escherichia coli colony with the composite nanofiber membrane, c is a photo of the Staphylococcus aureus colony (without the composite nanofiber membrane), and d is a photo of the Staphylococcus aureus colony with the composite nanofiber membrane. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the embodiments.

[0049] In the following examples, various processes and methods not described in detail are conventional methods well known in the art.

[0050] Unless otherwise specified, the materials, reagents, devices, instruments, and equipment used in the following examples can be obtained from commercial sources.

[0051] In the present invention, the scanning electron microscope test instrument used is HITACHI-SU8020. The electromagnetic shielding performance test instrument is the vector network analyzer Agilent PNA-N5244A. The conductivity test instrument is the four-probe tester Keithley2450. The mechanical property test instrument is the Japanese Shimadzu AG-1KN electronic universal material testing machine. The constant temperature and humidity chamber is HWS-80. The water contact angle test instrument is the German-Dataphysics-OCA20. The antibacterial test method is to first take 10μL of bacterial solution (Escherichia coli or Staphylococcus aureus bacterial solution) and add it to a centrifuge tube containing 20 mL of nutrient broth, and then place the centrifuge tube in a constant temperature shaker at 37°C and incubate at a rate of 200 rpm / min for 24 hours. Then dilute the obtained bacterial solution to 10 6 CFU / mL and 10 μL of diluted bacterial solution was added to the nutrient broth containing the composite nanofiber membrane, and then NIR laser (50 mW / cm 2 ) irradiate the material for 5 minutes, then place it in a constant temperature shaker to react for 24 hours. Finally, dilute the bacterial solution after 24 hours of reaction to 10 5 CFU / mL, and 10 μL was taken for plate counting.

[0052] Example 1

[0053] Step 1: First, add 1g of polyacrylonitrile to 9g of N,N-dimethylformamide and stir overnight until the solution is completely dissolved. Then, the obtained spinning solution is loaded into a syringe for spinning to obtain a polyacrylonitrile nanofiber membrane. The voltage of the electrospinning machine is 16kV and the spinning distance is 18cm.

[0054] Step 2: Soak the polyacrylonitrile nanofiber membrane in 100 mL of Tris-HCl solution containing dopamine (concentration of 7.9 mg mL -1 , pH = 8.5) and oscillated on a shaker at 40 ° C for 24 hours with an oscillation rate of 90 rpm. After that, it was repeatedly rinsed with deionized water and ethanol alternately, and then placed in an oven (338K) to dry to obtain a dopamine-coated fiber membrane with a fiber diameter of 150~290nm.

[0055] Step 3: First soak the dopamine-coated fiber membrane in a copper acetate (0.15 mol / L) aqueous solution for 2 hours, then transfer the soaked dopamine-coated fiber membrane into a mixed solution containing copper acetate (0.15 mol / L) (the solution is a mixed solution of water and ethylene glycol, with a volume ratio of 20 mL:60 mL). After the membrane is completely soaked, sodium thiosulfate is added (the reaction molar ratio of copper acetate and sodium thiosulfate is 1:1), stirred evenly, and reacted in an oil bath at 70°C for 4 hours. After the reaction stops, take it out, rinse it repeatedly with water and ethanol, and dry it to obtain a modified nanofiber membrane, that is, a nanofiber membrane modified with copper sulfide nanoparticles, wherein the diameter of the copper sulfide nanoparticles is about 20 nm, which can be well anchored on the fiber without affecting the pore size between the fibers and is not easy to fall off.

[0056] Step 4: Cut the modified nanofiber membrane into 7×7 cm, and evenly spray a MXene dispersion with a concentration of 9.8 mg / L onto the modified nanofiber membrane at a rate of 10 ml / h to obtain a conductive filler modified nanofiber membrane.

[0057] Step 5: Dissolve the polyurethane in DMF to obtain a 25 wt% polyurethane spinning solution, and use the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver for spinning to obtain a composite nanofiber membrane. The spinning voltage is 14 kV, the spinning time is 1 h, and the spinning distance is 15 cm.

[0058] The hydrophilic layer (CuS@PDA / PAN) of the composite nanofiber membrane prepared in Example 1 has a thickness of approximately 27 μm, a thickness of approximately 39 μm for the adhesive layer (MXene), and a thickness of approximately 22 μm for the hydrophobic layer (TPU); the pore size of the hydrophilic layer is 0.25-0.65 μm, and the pore size of the hydrophobic layer is 1.05-4.05 μm.

[0059] Figure 1This is a cross-sectional scanning electron microscope (SEM) image of the composite nanofiber membrane prepared in Example 1; Figure 1 It can be seen that the nanofiber membrane is a porous structure as a whole, and shows a difference in pore size along the thickness direction. After testing, the electromagnetic shielding value of the composite nanofiber membrane prepared in Example 1 in the X-band is 50dB ( Figure 2 The conductivity is 54S / cm, and after 100 bending and folding, it can still maintain excellent electromagnetic shielding performance with an electromagnetic shielding value of 48dB. In order to verify the directional perspiration ability and air permeability of the composite nanofiber membrane, an anti-gravity water contact angle test was carried out ( Figure 3 As shown in the experiment of water vapor transmission rate, the composite nanofiber membrane can quickly evaporate sweat within 10 seconds, and the composite nanofiber membrane has excellent air permeability, with a water vapor transmission rate of 720g·m -2 ·d -1 , which is much higher than the air permeability of human skin. In addition, the composite nanofiber membrane has a 2 Under the irradiation of xenon lamp, the equilibrium temperature can be rapidly increased from 24℃ to 50℃, and the photothermal curves after 5 cycles are almost the same, such as Figure 4 As shown, the composite nanofiber membrane has excellent light and heat stability. The antibacterial rates of the composite nanofiber membrane against Escherichia coli and Staphylococcus aureus are 95% and 99%, respectively. Figure 5 At the same time, the composite nanofiber membrane has good tensile strength and elongation at break, which are 9 MPa and 230% respectively.

[0060] Example 2

[0061] Step 1: First, add 1 g of polyacrylonitrile to 9 g of N,N-dimethylformamide and stir overnight until the solution is completely dissolved. Then, the obtained spinning solution is loaded into a syringe for spinning to obtain a polyacrylonitrile nanofiber membrane. The voltage of the electrospinning machine is 16 kV and the spinning distance is 18 cm.

[0062] Step 2: Soak the polyacrylonitrile nanofiber membrane in 100 mL of Tris-HCl solution containing dopamine (concentration of 7.9 mg mL -1 , pH = 8.5) and oscillated on a shaker at 40 ° C for 24 hours with an oscillation rate of 90 rpm. After that, it was repeatedly rinsed with deionized water and ethanol alternately, and then placed in an oven (338K) to dry to obtain a dopamine-coated fiber membrane with a fiber diameter of 150~290nm.

[0063] Step 3: First soak the dopamine-coated fiber membrane in a copper acetate (0.125 mol / L) aqueous solution for 2 hours, then transfer the soaked dopamine-coated fiber membrane into a mixed solution containing copper acetate (0.125 mol / L) (the solution is a mixed solution of water and ethylene glycol, with a volume ratio of 20 mL:60 mL). After the membrane is completely soaked, sodium thiosulfate is added (the reaction molar ratio of copper acetate and sodium thiosulfate is 1:1). After stirring evenly, react in an oil bath at 70°C for 4 hours. After the reaction stops, take it out, rinse it repeatedly with water and ethanol, and dry it to obtain a modified nanofiber membrane, that is, a composite nanofiber modified with copper sulfide nanoparticles, wherein the diameter of the copper sulfide nanoparticles is about 20 nm, which can be well anchored on the fiber without affecting the pore size between the fibers and is not easy to fall off.

[0064] Step 4: Cut the modified nanofiber membrane into 7×7 cm, and evenly spray a dispersion of MXene with a concentration of 8.9 mg / L onto the modified nanofiber membrane at a rate of 10 ml / h to obtain a conductive filler modified nanofiber membrane.

[0065] Step 5: Dissolve the polyurethane in DMF to obtain a 25 wt% polyurethane spinning solution, and use the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver for spinning to obtain a composite nanofiber membrane. The spinning voltage is 14 kV, the spinning time is 4 h, and the spinning distance is 15 cm.

[0066] The composite nanofiber membrane prepared in Example 2 has a hydrophilic layer (CuS@PP) thickness of approximately 27 μm, an adhesive layer (MXene) thickness of approximately 30 μm, and a hydrophobic layer (TPU) thickness of approximately 42 μm; the pore size of the hydrophilic layer is 0.25-0.65 μm, and the pore size of the hydrophobic layer is 1.05-4.05 μm.

[0067] After testing, the composite nanofiber membrane prepared in Example 2 has an electromagnetic shielding value of 40dB in the X-band and a conductivity of 45S / cm. It can still maintain excellent electromagnetic shielding performance after 100 bending and folding, with an electromagnetic shielding value of 38dB. The composite nanofiber membrane can evaporate sweat within 60s, and its water vapor permeability is 420g·m -2 ·d -1 In addition, the composite nanofiber membrane was 2 Under xenon lamp irradiation, the equilibrium temperature rapidly increased from 24°C to 45°C, and the photothermal curves remained nearly identical after five cycles, demonstrating the excellent photothermal stability of the composite nanofiber membrane. The composite nanofiber membrane demonstrated antibacterial rates of 90% against Escherichia coli and 95% against Staphylococcus aureus. Furthermore, the composite nanofiber membrane exhibited excellent tensile strength and elongation at break, reaching 9.2 MPa and 230%, respectively.

[0068] Example 3

[0069] Step 1: First, add 1 g of polyacrylonitrile to 9 g of N,N-dimethylformamide and stir overnight until the solution is completely dissolved. Then, the obtained spinning solution is loaded into a syringe for spinning to obtain a polyacrylonitrile nanofiber membrane. The voltage of the electrospinning machine is 16 kV and the spinning distance is 18 cm.

[0070] Step 2: Soak the polyacrylonitrile nanofiber membrane in 100 mL of Tris-HCl solution containing dopamine (concentration of 7.9 mg mL -1 , pH = 8.5) and oscillated on a shaker at 40 ° C for 24 hours with an oscillation rate of 90 rpm. After that, it was repeatedly rinsed with deionized water and ethanol alternately, and then placed in an oven (338K) to dry to obtain a dopamine-coated fiber membrane with a fiber diameter of 150~290nm.

[0071] Step 3: First, soak the dopamine-coated fiber membrane in a copper sulfate (0.175 mol / L) aqueous solution for 2 hours, and then transfer the soaked dopamine-coated fiber membrane into a mixed solution containing copper sulfate (0.175 mol / L) (the solution is a mixed solution of water and ethylene glycol, with a volume ratio of 20 mL:60 mL). After the membrane is completely soaked, sodium thiosulfate is added (the reaction molar ratio of copper sulfate and sodium thiosulfate is 1:1). After stirring evenly, react in an oil bath at 70°C for 4 hours. After the reaction stops, take it out, rinse it repeatedly with water and ethanol, and dry it to obtain a modified nanofiber membrane, that is, a composite nanofiber modified with copper sulfide nanotubes, wherein the diameter of the copper sulfide nanotubes is about 400 nm, which is not easy to anchor on the fiber, but is easy to cover the fiber surface and is extremely easy to fall off.

[0072] Step 4: Cut the modified nanofiber membrane into 7×7 cm, and evenly spray a dispersion of MXene with a concentration of 9.8 mg / L onto the modified nanofiber membrane at a rate of 10 ml / h to obtain a conductive filler modified nanofiber membrane.

[0073] Step 5: Dissolve the polyurethane in DMF to obtain a 25 wt% polyurethane spinning solution, and use the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver for spinning to obtain a composite nanofiber membrane. The spinning voltage is 14 kV, the spinning time is 1 h, and the spinning distance is 15 cm.

[0074] The hydrophilic layer (CuS@PDA / PAN) of the composite nanofiber membrane prepared in Example 3 has a thickness of about 30 μm, the adhesive layer (MXene) has a thickness of about 39 μm, and the hydrophobic layer (TPU) has a thickness of about 22 μm; the pore size of the hydrophilic layer is 0.2~0.45 μm, and the pore size of the hydrophobic layer is 1.05~4.05 μm.

[0075] After testing, the composite nanofiber membrane prepared in Example 3 had an electromagnetic shielding value of 40dB in the X-band and a conductivity of 35S / cm. After 100 bends and folds, the electromagnetic shielding value decreased to 28dB. The composite nanofiber membrane could evaporate sweat within 12 seconds, and its water vapor permeability was 570g·m -2 ·d -1 The composite nanofiber membrane is at 50mW / cm 2 Under xenon lamp irradiation, the equilibrium temperature rapidly increased from 24°C to 40°C, and the photothermal curves remained nearly identical after five cycles, demonstrating the excellent photothermal stability of the composite nanofiber membrane. The composite nanofiber membrane demonstrated antibacterial rates of 87% and 90% against Escherichia coli and Staphylococcus aureus, respectively. Furthermore, the composite nanofiber membrane exhibited excellent tensile strength and elongation at break, reaching 8.9 MPa and 200%, respectively.

[0076] Example 4

[0077] Step 1: First, add 1 g of polyacrylonitrile to 9 g of N,N-dimethylformamide and stir overnight until the solution is completely dissolved. Then, the obtained spinning solution is loaded into a syringe for spinning to obtain a polyacrylonitrile nanofiber membrane. The voltage of the electrospinning machine is 16 kV and the spinning distance is 18 cm.

[0078] Step 2: Soak the polyacrylonitrile nanofiber membrane in 100 mL of Tris-HCl solution containing dopamine (concentration of 7.9 mg mL -1 , pH = 8.5) and oscillated on a shaker at 40 ° C for 24 hours with an oscillation rate of 90 rpm. After that, it was repeatedly rinsed with deionized water and ethanol alternately, and then placed in an oven (338K) to dry to obtain a dopamine-coated fiber membrane with a fiber diameter of 150~290nm.

[0079] Step 3: First, soak the dopamine-coated fiber membrane in a copper chloride (0.15 mol / L) aqueous solution for 2 hours, and then transfer the soaked dopamine-coated fiber membrane into a mixed solution containing copper chloride (0.15 mol / L) (the solution is a mixed solution of water and ethylene glycol, with a volume ratio of 20 mL:60 mL). After the membrane is completely soaked, sodium thiosulfate is added (the reaction molar ratio of copper chloride and sodium thiosulfate is 1:1). After stirring evenly, react in an oil bath at 70°C for 4 hours. After the reaction stops, take it out, rinse it repeatedly with water and ethanol, and dry it to obtain a modified nanofiber membrane, that is, a composite nanofiber modified by copper sulfide nanosheets, wherein the copper sulfide nanosheets have a thickness of about 25 nm and a diameter of about 70 nm. They are not easy to anchor on the fibers, but are easy to cover the fiber surface and are extremely easy to fall off.

[0080] Step 4: Cut the modified nanofiber membrane into 7×7 cm, and evenly spray a dispersion containing MXene with a concentration of 10.5 mg / L onto the modified nanofiber membrane at a rate of 10 ml / h to obtain a conductive filler modified nanofiber membrane.

[0081] Step 5: Dissolve the polyurethane in DMF to obtain a 25 wt% polyurethane spinning solution, and use the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver for spinning to obtain a composite nanofiber membrane. The spinning voltage is 14 kV, the spinning time is 1 h, and the spinning distance is 15 cm.

[0082] The hydrophilic layer (CuS@PDA / PAN) of the composite nanofiber membrane prepared in Example 4 has a thickness of approximately 27 μm, the adhesive layer (MXene) has a thickness of approximately 40 μm, and the hydrophobic layer (TPU) has a thickness of approximately 22 μm; the pore size of the hydrophilic layer is 0.2~0.42 μm, and the pore size of the hydrophobic layer is 1.05~4.05 μm.

[0083] After testing, the composite nanofiber membrane prepared in Example 4 has an electromagnetic shielding value of 54dB in the X-band, a conductivity of 60S / cm, and an electromagnetic shielding value of 35dB after 100 bending and folding. The composite nanofiber membrane can quickly evaporate sweat within 23s, and the water vapor permeability is 490g·m -2 ·d -1 In addition, the composite nanofiber membrane was 2 Under xenon lamp irradiation, the equilibrium temperature rapidly increased from 24°C to 55°C, and the photothermal curves after five cycles were nearly identical, demonstrating the excellent photothermal stability of the composite nanofiber membrane. The composite nanofiber membrane demonstrated antibacterial rates of 95% against Escherichia coli and 99% against Staphylococcus aureus. Furthermore, the composite nanofiber membrane exhibited excellent tensile strength and elongation at break, reaching 8.7 MPa and 210%, respectively.

[0084] Example 5

[0085] Step 1: First, add 1 g of polyacrylonitrile to 9 g of N,N-dimethylformamide and stir overnight until the solution is completely dissolved. Then, the obtained spinning solution is loaded into a syringe for spinning to obtain a polyacrylonitrile nanofiber membrane. The voltage of the electrospinning machine is 16 kV and the spinning distance is 18 cm.

[0086] Step 2: Soak the polyacrylonitrile nanofiber membrane in 100 mL of Tris-HCl solution containing dopamine (concentration of 7.9 mg mL -1, pH = 8.5) and oscillated on a shaker at 40 ° C for 24 hours with an oscillation rate of 90 rpm. After that, it was repeatedly rinsed with deionized water and ethanol alternately, and then placed in an oven (338K) to dry to obtain a dopamine-coated fiber membrane with a fiber diameter of 150~290nm.

[0087] Step 3: First, soak the dopamine-coated fiber membrane in a copper nitrate (0.15 mol / L) aqueous solution for 2 hours, and then transfer the soaked dopamine-coated fiber membrane into a mixed solution containing copper nitrate (0.15 mol / L) (the solution is a mixed solution of water and ethylene glycol, with a volume ratio of 20 mL:60 mL). After the membrane is completely soaked, sodium thiosulfate is added (the reaction molar ratio of copper nitrate and sodium thiosulfate is 1:1). After stirring evenly, react in an oil bath at 180°C for 4 hours. After the reaction stops, take it out, rinse it repeatedly with water and ethanol, and dry it to obtain a modified nanofiber membrane, that is, a composite nanofiber modified with copper sulfide nanotubes, wherein the diameter of the copper sulfide tube is about 500 nm, which is not easy to anchor on the fiber, but is easy to cover the fiber surface and is extremely easy to fall off.

[0088] Step 4: Cut the modified nanofiber membrane into 7×7 cm, and evenly spray a dispersion containing 9.8 mg / L MXene onto the modified nanofiber membrane at a rate of 10 ml / h to obtain a conductive filler-modified nanofiber membrane.

[0089] Step 5: Dissolve the polyurethane in DMF to obtain a 25 wt% polyurethane spinning solution, and use the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver for spinning to obtain a composite nanofiber membrane. The spinning voltage is 14 kV, the spinning time is 1 h, and the spinning distance is 15 cm.

[0090] The hydrophilic layer (CuS@PDA / PAN) of the composite nanofiber membrane prepared in Example 5 has a thickness of approximately 30 μm, the adhesive layer (MXene) has a thickness of approximately 39 μm, and the hydrophobic layer (TPU) has a thickness of approximately 22 μm; the pore size of the hydrophilic layer is 0.2~0.42 μm, and the pore size of the hydrophobic layer is 1.05~4.05 μm.

[0091] After testing, the composite nanofiber membrane prepared in Example 5 has an electromagnetic shielding value of 49dB in the X-band, a conductivity of 52S / cm, and an electromagnetic shielding value of 32dB after 100 bending and folding. The composite nanofiber membrane can quickly evaporate sweat within 28s, and the water vapor permeability is 490g·m -2 ·d -1 In addition, the composite nanofiber membrane was 2Under xenon lamp irradiation, the equilibrium temperature rapidly increased from 24°C to 50°C, and the photothermal curves remained nearly identical after five cycles, demonstrating the composite nanofiber membrane's excellent photothermal stability. The composite nanofiber membrane demonstrated antibacterial rates of 95% against Escherichia coli and 99% against Staphylococcus aureus. Furthermore, the composite nanofiber membrane exhibited excellent tensile strength and elongation at break, reaching 8.7 MPa and 210%, respectively.

[0092] Example 6

[0093] Step 1: First, add 1 g of polyacrylonitrile to 9 g of N,N-dimethylformamide and stir overnight until the solution is completely dissolved. Then, the obtained spinning solution is loaded into a syringe for spinning to obtain a polyacrylonitrile nanofiber membrane. The voltage of the electrospinning machine is 16 kV and the spinning distance is 18 cm.

[0094] Step 2: Soak the polyacrylonitrile nanofiber membrane in 100 mL of Tris-HCl solution containing dopamine (concentration of 7.9 mg·mL-1, pH=8.5), and oscillate on a shaker at 40°C for 24 hours with an oscillation rate of 90 rpm. Then, rinse it alternately with deionized water and ethanol, and then place it in an oven (338K) to dry to obtain a dopamine-coated fiber membrane with a fiber diameter of 150~290 nm.

[0095] Step 3: First soak the dopamine-coated fiber membrane in a copper nitrate (0.15 mol / L) aqueous solution for 2 hours, then transfer the soaked dopamine-coated fiber membrane into a mixed solution containing copper nitrate (0.15 mol / L) (the solution is a mixed solution of water and ethylene glycol, with a volume ratio of 20 mL:20 mL). After the membrane is completely soaked, sodium thiosulfate is added (the reaction molar ratio of copper nitrate and sodium thiosulfate is 1:1). After stirring evenly, react in an oil bath at 70°C for 4 hours. After the reaction stops, take it out, rinse it repeatedly with water and ethanol, and dry it to obtain a modified nanofiber membrane, that is, a composite nanofiber modified with copper sulfide nanotubes, wherein the diameter of the copper sulfide tube is about 600 nm, which is not easy to anchor on the fiber, but is easy to cover the fiber surface and is extremely easy to fall off.

[0096] Step 4: Cut the modified nanofiber membrane into 7×7 cm, and evenly spray a dispersion containing 9.8 mg / L MXene onto the modified nanofiber membrane at a rate of 10 ml / h to obtain a conductive filler-modified nanofiber membrane.

[0097] Step 5: Dissolve the polyurethane in DMF to obtain a 25 wt% polyurethane spinning solution, and use the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver for spinning to obtain a composite nanofiber membrane. The spinning voltage is 14 kV, the spinning time is 1 h, and the spinning distance is 15 cm.

[0098] The hydrophilic layer (CuS@PDA / PAN) of the composite nanofiber membrane prepared in Example 6 has a thickness of approximately 30 μm, the adhesive layer (MXene) has a thickness of approximately 39 μm, and the hydrophobic layer (TPU) has a thickness of approximately 22 μm; the pore size of the hydrophilic layer is 0.2~0.42 μm, and the pore size of the hydrophobic layer is 1.05~4.05 μm.

[0099] After testing, the composite nanofiber membrane prepared in Example 6 has an electromagnetic shielding value of 49dB in the X-band, a conductivity of 52S / cm, and an electromagnetic shielding value of 30dB after 100 bends and folds. The composite nanofiber membrane can quickly evaporate sweat within 30s, and its water vapor permeability is 485g·m -2 ·d -1 In addition, the composite nanofiber membrane was 2 Under xenon lamp irradiation, the equilibrium temperature rapidly increased from 24°C to 50°C, and the photothermal curves after five cycles were nearly identical, demonstrating the excellent photothermal stability of the composite nanofiber membrane. The composite nanofiber membrane demonstrated antibacterial rates of 95% and 99% against Escherichia coli and Staphylococcus aureus, respectively. Furthermore, the composite nanofiber membrane exhibited excellent tensile strength and elongation at break of 8.6 MPa and 210%, respectively.

[0100] Example 7

[0101] Step 1: First, add 1 g of polyacrylonitrile to 9 g of N,N-dimethylformamide and stir overnight until the solution is completely dissolved. Then, the obtained spinning solution is loaded into a syringe for spinning to obtain a polyacrylonitrile nanofiber membrane. The voltage of the electrospinning machine is 16 kV and the spinning distance is 18 cm.

[0102] Step 2: Soak the polyacrylonitrile nanofiber membrane in 100 mL of Tris-HCl solution containing dopamine (concentration of 7.9 mg mL -1 , pH = 8.5) and oscillated on a shaker at 40 ° C for 24 hours with an oscillation rate of 90 rpm. After that, it was repeatedly rinsed with deionized water and ethanol alternately, and then placed in an oven (338K) to dry to obtain a dopamine-coated fiber membrane with a fiber diameter of 150~290nm.

[0103] Step 3: First soak the dopamine-coated fiber membrane in a copper acetate (0.15 mol / L) aqueous solution for 2 hours, then transfer the soaked dopamine-coated fiber membrane into a mixed solution containing copper acetate (0.15 mol / L) (the solution is a mixed solution of water and ethylene glycol, with a volume ratio of 20 mL:60 mL). After the membrane is completely soaked, sodium thiosulfate is added (the reaction molar ratio of copper acetate and sodium thiosulfate is 1:1). After stirring evenly, react in an oil bath at 70°C for 4 hours. After the reaction stops, take it out, rinse it repeatedly with water and ethanol, and dry it to obtain a modified nanofiber membrane, that is, a composite nanofiber modified with copper sulfide nanoparticles, wherein the diameter of the copper sulfide nanoparticles is about 20 nm, which can be well anchored on the fiber without affecting the pore size between the fibers and is not easy to fall off.

[0104] Step 4: Cut the modified nanofiber membrane into 7×7 cm, and evenly spray a dispersion containing acidified carbon nanotubes with a concentration of 9.8 mg / L onto the modified nanofiber membrane at a rate of 10 ml / h to obtain a conductive filler modified nanofiber membrane, wherein the acidified carbon nanotubes are carbon nanotubes acidified with concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1, the acidification temperature is 60~120℃, and the acidification time is 2~8h.

[0105] Step 5: Dissolve the polyurethane in DMF to obtain a 25 wt% polyurethane spinning solution, and use the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver for spinning to obtain a composite nanofiber membrane. The spinning voltage is 14 kV, the spinning time is 1 h, and the spinning distance is 15 cm.

[0106] The hydrophilic layer (CuS@PDA / PAN) of the composite nanofiber membrane prepared in Example 7 has a thickness of approximately 27 μm, the adhesive layer (acidified carbon nanotubes) has a thickness of approximately 29 μm, and the hydrophobic layer (TPU) has a thickness of approximately 22 μm; the pore size of the hydrophilic layer is 0.3~0.65 μm, and the pore size of the hydrophobic layer is 1.05~4.05 μm.

[0107] After testing, the composite nanofiber membrane prepared in Example 7 has an electromagnetic shielding value of 42dB in the X-band and a conductivity of 24S / cm. It can still maintain excellent electromagnetic shielding performance after 100 bending and folding, with an electromagnetic shielding value of 38dB. The composite nanofiber membrane can quickly evaporate sweat within 10 seconds, and the water vapor permeability of the composite nanofiber membrane is 693g·m -2 ·d -1 In addition, the composite nanofiber membrane was 2Under xenon lamp irradiation, the equilibrium temperature rapidly increased from 24°C to 45°C, and the photothermal curves after five cycles were nearly identical, demonstrating the excellent photothermal stability of the composite nanofiber membrane. The composite nanofiber membrane demonstrated antibacterial rates of 80% against Escherichia coli and 85% against Staphylococcus aureus. Furthermore, the composite nanofiber membrane exhibited excellent tensile strength and elongation at break, reaching 8.5 MPa and 200%, respectively.

[0108] Example 8

[0109] Step 1: First, add 1 g of polyacrylonitrile to 9 g of N,N-dimethylformamide and stir overnight until the solution is completely dissolved. Then, the obtained spinning solution is loaded into a syringe for spinning to obtain a polyacrylonitrile nanofiber membrane. The voltage of the electrospinning machine is 16 kV and the spinning distance is 18 cm.

[0110] Step 2: Soak the polyacrylonitrile nanofiber membrane in 100 mL of Tris-HCl solution containing dopamine (concentration of 7.9 mg mL -1 , pH = 8.5) and oscillated on a shaker at 40 ° C for 24 hours with an oscillation rate of 90 rpm. After that, it was repeatedly rinsed with deionized water and ethanol alternately, and then placed in an oven (338K) to dry to obtain a dopamine-coated fiber membrane with a fiber diameter of 150~290nm.

[0111] Step 3: First, soak the dopamine-coated fiber membrane obtained in step 2 in an aqueous solution containing silver nitrate (0.2 mol / L) for 2 hours, and then transfer the soaked dopamine-coated fiber membrane into a silver ammonia solution (the concentration of silver nitrate is 0.2 mol / L) for immersion. After the membrane is completely soaked, glucose is added. The molar ratio of silver ions to glucose in the silver ammonia solution is 1:2. After stirring evenly, react at 70°C for 4 hours. After the reaction stops, take it out, rinse it repeatedly with water and ethanol, and dry it to obtain a modified nanofiber membrane, that is, a composite nanofiber modified with silver nanoparticles, wherein the diameter of the silver nanoparticles is about 30 nm.

[0112] Step 4: Cut the modified nanofiber membrane into 7×7 cm, and evenly spray a dispersion containing 9.8 mg / L MXene onto the modified nanofiber membrane at a rate of 10 ml / h to obtain a conductive filler-modified nanofiber membrane.

[0113] Step 5: Dissolve the polyurethane in DMF to obtain a 25 wt% polyurethane spinning solution, and use the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver for spinning to obtain a composite nanofiber membrane. The spinning voltage is 14 kV, the spinning time is 1 h, and the spinning distance is 15 cm.

[0114] The hydrophilic layer (Ag@PDA / PAN) of the composite nanofiber membrane prepared in Example 8 has a thickness of approximately 28 μm, a thickness of approximately 39 μm for the adhesive layer (MXene), and a thickness of approximately 22 μm for the hydrophobic layer (TPU); the pore size of the hydrophilic layer is 0.25-0.65 μm, and the pore size of the hydrophobic layer is 1.05-4.05 μm.

[0115] After testing, the composite nanofiber membrane prepared in Example 8 has an electromagnetic shielding value of 90dB in the X-band and a conductivity of 100S / cm. It can still maintain excellent electromagnetic shielding performance after 100 bending and folding, with an electromagnetic shielding value of 85dB. The composite nanofiber membrane can quickly evaporate sweat within 12 seconds, and its water vapor permeability is 690g·m -2 ·d -1 In addition, the composite nanofiber membrane was 2 Under xenon lamp irradiation, the equilibrium temperature rapidly increased from 24°C to 60°C, and the photothermal curves after five cycles were nearly identical, demonstrating the excellent photothermal stability of the composite nanofiber membrane. The composite nanofiber membrane demonstrated antibacterial rates of 96% and 99% against Escherichia coli and Staphylococcus aureus, respectively. Furthermore, the composite nanofiber membrane exhibited excellent tensile strength and elongation at break, reaching 9.2 MPa and 220%, respectively.

[0116] Comparative Example 1

[0117] Step 1: First, add 1 g of polyacrylonitrile to 9 g of N,N-dimethylformamide and stir overnight until the solution is completely dissolved. Then, the obtained spinning solution is loaded into a syringe for spinning to obtain a polyacrylonitrile nanofiber membrane. The voltage of the electrospinning machine is 16 kV and the spinning distance is 18 cm.

[0118] Step 2: Soak the polyacrylonitrile nanofiber membrane in 100 mL of Tris-HCl solution containing dopamine (concentration of 7.9 mg mL -1 , pH = 8.5) and oscillated on a shaker at 40 ° C for 24 hours with an oscillation rate of 90 rpm. After that, it was repeatedly rinsed with deionized water and ethanol alternately, and then placed in an oven (338K) to dry to obtain a dopamine-coated fiber membrane with a fiber diameter of 150~290nm.

[0119] Step 3: First soak the dopamine-coated fiber membrane in a copper acetate (0.15 mol / L) aqueous solution for 2 hours, then transfer the soaked dopamine-coated fiber membrane into a mixed solution containing copper acetate (0.15 mol / L) (the solution is a mixed solution of water and ethylene glycol, with a volume ratio of 20 mL:60 mL). After the membrane is completely soaked, sodium thiosulfate is added (the reaction molar ratio of copper acetate and sodium thiosulfate is 1:1), stirred evenly, and reacted in an oil bath at 70°C for 4 hours. After the reaction stops, take it out, rinse it repeatedly with water and ethanol, and dry it to obtain a modified nanofiber membrane, that is, a nanofiber membrane modified with copper sulfide nanoparticles, wherein the diameter of the copper sulfide nanoparticles is about 20 nm, which can be well anchored on the fiber without affecting the pore size between the fibers and is not easy to fall off.

[0120] Step 4: Dissolve the polyurethane in DMF to obtain a 25 wt% polyurethane spinning solution, and use the modified nanofiber membrane as a receiver for spinning to obtain a composite nanofiber membrane. The spinning voltage is 14 kV and the spinning time is 1 h.

[0121] The thickness of the hydrophilic layer (CuS@PDA / PAN) of the composite nanofiber membrane prepared in Comparative Example 1 is about 27 μm, and the thickness of the hydrophobic layer (TPU) is about 22 μm; the pore size of the hydrophilic layer is 0.25~0.65 μm, and the pore size of the hydrophobic layer is 1.05~4.05 μm.

[0122] After testing, the composite nanofiber membrane prepared in Example 1 has an electromagnetic shielding value of 28dB in the X-band and a conductivity of 11.5S / cm. After 100 bending and folding, the fiber membrane showed obvious delamination, and the electromagnetic shielding value dropped to 14dB. 2 Under xenon lamp irradiation, the equilibrium temperature can be rapidly increased from 24°C to 40°C, with antibacterial rates against Escherichia coli and Staphylococcus aureus of 73% and 78%, respectively. The tensile strength and elongation at break of the composite nanofiber membrane are 3.8 MPa and 39%, respectively.

[0123] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the embodiments. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all embodiments here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A composite nanofiber membrane, characterized in that: It consists of a hydrophilic layer, an adhesive layer and a hydrophobic layer arranged in sequence; The material of the hydrophilic layer is polyacrylonitrile modified by nanoparticles, the material of the bonding layer is conductive filler, and the material of the hydrophobic layer is polyurethane.

2. The composite nanofiber membrane according to claim 1, characterized in that The hydrophilic layer has a thickness of 20-32 μm and a pore size of 0.15-0.85 μm; The thickness of the bonding layer is 25-41 μm; The hydrophobic layer has a thickness of 22-43 μm and a pore size of 1-4.5 μm.

3. The composite nanofiber membrane according to claim 1, characterized in that The nanoparticles are sulfur One or more of copper nanoparticles, silver nanoparticles, and gold nanoparticles; The conductive filler is transition metal carbonitride, acidified carbon nanotube or graphene.

4. The method for preparing the composite nanofiber membrane according to claim 1, wherein: The following steps are involved: Step 1: dissolving polyacrylonitrile in a solvent to obtain a polyacrylonitrile spinning solution, and spinning to obtain a polyacrylonitrile nanofiber membrane; Step 2: Soaking the polyacrylonitrile nanofiber membrane obtained in step 1 in a tris (hydroxymethyl)aminomethane hydrochloride) solution containing dopamine, shaking the reaction, taking it out, repeatedly washing it with deionized water and ethanol alternately, and drying it to obtain a dopamine-coated fiber membrane; Step 3: First, soak the dopamine-coated fiber membrane obtained in step 2 in an aqueous solution containing copper salt for 2 to 6 hours, then transfer the soaked dopamine-coated fiber membrane to a mixed solution containing copper salt, add sodium thiosulfate after it is completely soaked, stir evenly and react, take out after the reaction stops, rinse repeatedly with water and ethanol, and dry to obtain a modified nanofiber membrane; Alternatively, the dopamine-coated fiber membrane obtained in step 2 is first soaked in an aqueous solution containing silver salt for 2 to 6 hours, and then the soaked dopamine-coated fiber membrane is transferred to a silver ammonia solution for soaking. After it is completely soaked, glucose is added, stirred evenly and reacted. After the reaction stops, the membrane is taken out, rinsed repeatedly with water and ethanol, and dried to obtain a modified nanofiber membrane. Step 4: spraying the dispersion containing the conductive filler onto the modified nanofiber membrane prepared in step 3, and drying to obtain the conductive filler modified nanofiber membrane; Step 5: dissolving the polyurethane in a solvent to obtain a polyurethane spinning solution, and spinning the conductive filler-modified nanofiber membrane prepared in step 4 as a receiver to obtain a composite nanofiber membrane.

5. The method for preparing the composite nanofiber membrane according to claim 4, characterized in that: In step 1, the mass fraction of polyacrylonitrile in the polyacrylonitrile spinning solution is 10% to 20%, the solvent is N,N-dimethylformamide, N-methylpyrrolidone or tetrahydrofuran, the spinning voltage is 16 to 17 kV, and the spinning distance is 1 to 18 cm.

6. The method for preparing the composite nanofiber membrane according to claim 4, characterized in that: In step 2, the concentration of the tris(hydroxymethyl)aminomethane hydrochloride) solution containing dopamine is 7.9 mg·mL -1 , pH=8.5~9, oscillation rate is 60~90rpm, reaction temperature is 40~60℃, and reaction time is 12~24h.

7. The method for preparing the composite nanofiber membrane according to claim 4, characterized in that: In step 3, the concentration of the aqueous solution containing the copper salt is 0.025~0.175mol / L; in the mixed solution containing the copper salt, the concentration of the copper salt is 0.025~0.175mol / L, the mixed solution is a mixed solution of water and ethylene glycol with a volume ratio of 1:1~1:3, the reaction molar ratio of the copper salt and sodium thiosulfate is 1:1~1:3, the reaction time is 4~7h, and the reaction temperature is 70~180°C; the copper salts are independently copper acetate, copper sulfate, copper chloride or copper nitrate; The concentration of the aqueous solution containing silver salt is 0.1-0.3 mol / L, and the silver salt is silver nitrate; The concentration of the silver ammonia solution is calculated as silver nitrate concentration, the concentration of silver nitrate is 0.1-0.3 mol / L, the molar ratio of silver ions to glucose in the silver ammonia solution is 1:2, the reaction time is 0.5-4 h, and the reaction temperature is 70-90° C.; The dopamine-coated fiber membrane obtained in step 2 is immersed in an aqueous solution containing copper salt for 2 to 6 hours, dried, and then the dried dopamine-coated fiber membrane is immersed in a mixed solution containing copper salt; The dopamine-coated fiber membrane obtained in step 2 is immersed in an aqueous solution containing silver salt for 2 to 6 hours, dried first, and then the dried dopamine-coated fiber membrane after the soaking is transferred to a silver ammonia solution for immersion.

8. The method for preparing the composite nanofiber membrane according to claim 4, characterized in that: In step 4, the conductive filler is a transition metal carbonitride, an acidified carbon nanotube or graphene, the concentration of the conductive filler in the dispersion containing the conductive filler is 8-20 mg / L, and the spraying rate is 10-20 ml / h.

9. The method for preparing the composite nanofiber membrane according to claim 4, characterized in that: In step 5, the mass fraction of polyurethane in the polyurethane spinning solution is 20% to 25%, the solvent is N,N-dimethylformamide, N-methylpyrrolidone or tetrahydrofuran, the spinning voltage is 14 to 15 kV, and the spinning distance is 15 to 18 cm.

10. Use of the composite nanofiber membrane according to any one of claims 1 to 3 or the composite nanofiber membrane prepared by the preparation method according to any one of claims 4 to 9 in wearable electromagnetic shielding materials.

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