High-efficiency air filtering nanofiber membrane with continuous antibacterial performance and preparation method of high-efficiency air filtering nanofiber membrane

Abstract

The invention discloses an efficient air filtering nanofiber membrane with continuous antibacterial performance and a preparation method thereof, and the preparation method comprises the following steps: dissolving TPU in a mixed solvent of N, N-dimethylformamide and acetone to form a TPU solution; adding the ZIF-8 nanoparticles into the TPU solution to form a TZ solution; preparing a TPU / ZIF-8 nanofiber membrane by adopting an electrostatic spinning technology; the preparation method comprises the following steps: dissolving PVDF in a mixed solvent of N, N-dimethylformamide and acetone to form a PVDF solution; adding MXene into the PVDF solution to form a PM solution; and spinning and compounding a PM solution on the surface of the TPU / ZIF-8 nanofiber membrane to obtain the TPU / ZIF-8 nanofiber membrane. The invention provides an electrostatic spinning nanofiber composite membrane with high filtering efficiency and lasting antibacterial performance so as to realize efficient interception and long-acting inhibition on particulate matters and microorganisms in air.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanofiber membranes, in particular, the present application relates to a high-efficiency air filtration nanofiber membrane with sustained antibacterial performance and a preparation method thereof. BACKGROUND

[0002] Air filtration systems have important application value in environmental governance and medical health fields. With the increasing concentration of particulate matter, bacteria and viruses and other pollutants in the air, the demand for high-efficiency air filtration materials is increasing. The ideal air filter should not only achieve efficient capture of particulate matter, but also have antibacterial function to prevent the growth of microorganisms during use, causing a decrease in filtration efficiency and secondary pollution. In existing research, electrospun nanofiber membranes exhibit excellent performance in air filtration due to their controllable fiber diameter, large specific surface area and adjustable porosity, and can efficiently capture ultrafine particles at low pressure drop. However, traditional electrospun fiber membranes mostly do not have antibacterial properties and are easily contaminated by microorganisms during long-term use, reducing the service life.

[0003] To improve the antibacterial performance, researchers propose to introduce functional materials into electrospun nanofiber membranes. For example, metal organic framework material ZIF-8 has a large specific surface area and controllable pore structure, and can play a certain antibacterial role by releasing metal ions. However, ZIF-8 has poor stability in high humidity environment, and the metal ion release process is difficult to maintain long-term. On the other hand, MXene material as a new type of two-dimensional material has good electrical conductivity and photothermal properties, and can achieve rapid sterilization under light or electrical stimulation, and also has potential advantages in adsorbing and intercepting particulate pollutants. However, MXene is easily oxidized in air, and its dispersion and binding stability in polymer matrix are insufficient, limiting its application in filtration membranes.

[0004] Therefore, although the existing air filtration materials based on electrospun nanofiber membranes have made certain progress in efficient filtration and antibacterial function, there are still obvious deficiencies in antibacterial durability, material stability and dual-functional integrated design, which are still difficult to meet the demand for long-term air purification in industrial sites, medical institutions and high-pollution environments. SUMMARY

[0005] The present application aims to at least solve one of the technical problems in the related art, and therefore provides a high-efficiency air filtration nanofiber membrane with sustained antibacterial performance and a preparation method and application thereof.

[0006] The present application adopts the following technical solutions: In a first aspect, The application provides a preparation method of high-efficiency air filtration nanofiber membrane with sustained antibacterial performance, comprising the following steps: (1) dissolving TPU (polyurethane) in a mixed solvent of N,N-dimethylformamide and acetone, continuously stirring to form a TPU solution; adding ZIF-8 nanoparticles into the TPU solution, continuously stirring to form a TZ solution; and preparing a TPU / ZIF-8 nanofiber membrane by using an electrospinning technology; (2) dissolving PVDF (polyvinylidene fluoride) in a mixed solvent of N,N-dimethylformamide and acetone, continuously stirring to form a PVDF solution; adding MXene into the PVDF solution, continuously stirring to form a PM solution; (3) performing spinning compounding on the PM solution of step (2) on the surface of the TPU / ZIF-8 nanofiber membrane, and obtaining the high-efficiency air filtration nanofiber membrane with sustained antibacterial performance.

[0007] In some embodiments, in step (1), the volume ratio of N,N-dimethylformamide and acetone is 4:6-10:1.

[0008] In some embodiments, in step (1), the concentration of TPU in the TZ solution is 4-15 wt%; and the addition amount of ZIF-8 nanoparticles is 0.4-0.6% of the mass of TPU.

[0009] In some preferred embodiments, the concentration of TPU in the TZ solution is 6-10 wt%; and more preferably 8 wt%.

[0010] In some embodiments, in step (1), the setting parameters of electrospinning are as follows: the spinning voltage is 15-35 kV, the receiving distance is 5-25 cm, and the advancing rate is 1-3 mL / h. Preferably, the setting parameters of electrospinning are as follows: the spinning voltage is 20 kV, the receiving distance is 20 cm, and the spinning speed is 2 mL / h.

[0011] In some embodiments, the preparation method of ZIF-8 nanoparticles is as follows: dissolving 2-methylimidazole and zinc nitrate hexahydrate in deionized water, stirring sufficiently, heating at 37℃ for 6 hours, centrifuging after the reaction is completed, washing with methanol for multiple times, and drying in a 37℃ oven for 24 hours to obtain ZIF-8 nanoparticles.

[0012] In a specific embodiment, the ratio of 2-methylimidazole, zinc nitrate hexahydrate and deionized water is 4.54 g:0.22 g:80 mL.

[0013] In some embodiments, in step (2), the volume ratio of N,N-dimethylformamide and acetone is 5:5-10:1.

[0014] In some embodiments, in step (2), the concentration of PVDF in the PM solution is 6-15 wt%; and the amount of MXene added is 4-6% of the mass of PVDF.

[0015] In some embodiments, in step (2), the concentration of PVDF in the PM solution is 8-12 wt%; and more preferably 10 wt%.

[0016] In some embodiments, in step (2), the method for synthesizing MXene comprises the following steps: Dissolve lithium fluoride in 9M hydrochloric acid, add Ti3AlC2 powder to the premixed etching solution under continuous magnetic stirring during the etching process, react at 35°C for 24 hours, after etching is completed, wash with deionized water, centrifuge, discard the supernatant, repeat the process until the pH value of the supernatant reaches 6, centrifuge the dark green suspension rich in MXene layers at a speed of 3500 rpm for 30 minutes to separate MXene, then ultrasonic treatment in an ice water bath for 1 hour to achieve uniform peeling, and finally dry in a vacuum oven at 60°C for 12 hours to obtain a stable MXene powder product.

[0017] In a specific embodiment, the ratio of Ti3AlC2 powder, lithium fluoride and 9M hydrochloric acid is 1g:1g:20mL.

[0018] In some embodiments, in step (3), the setting parameters of electrospinning are as follows: spinning voltage 8-16kV, receiving distance 5-25 cm, and pushing rate 1-3mL / h. Preferably, the setting parameters of electrospinning are as follows: spinning voltage 14kV, spinning speed 1.5mL / h, and receiving distance 20cm.

[0019] The second aspect, The application provides a high-efficiency air filtration nanofiber membrane with sustained antibacterial performance, which is prepared by the method comprising the above steps.

[0020] The third aspect, The application also provides the use of the high-efficiency air filtration nanofiber membrane with sustained antibacterial performance in the preparation of an antibacterial mask.

[0021] In some embodiments of the application, the mask comprises an outer non-woven fabric layer, a high-efficiency air filtration nanofiber membrane with sustained antibacterial performance, and an inner non-woven fabric layer.

[0022] That is, the antibacterial mask comprises four layers, namely an outer non-woven fabric layer, a PVDF / MXene nanofiber membrane, a TPU / ZIF-8 nanofiber membrane, and an inner non-woven fabric layer.

[0023] The present application has the following advantages and beneficial effects: The present application overcomes the defects of insufficient antibacterial performance, poor material stability and difficulty in balancing high filtration efficiency and long-term antibacterial performance of the existing air filtration material, and provides an electrospun nanofiber composite membrane with high filtration efficiency and long-term antibacterial performance, so as to realize efficient interception and long-term inhibition of particulate matters and microorganisms in the air.

[0024] Compared with the prior art, the antibacterial layer is constructed by the TPU / ZIF-8 electrospun nanofiber membrane, the continuous release of metal ions is realized while the flexibility and mechanical properties are ensured, and the material is endowed with long-term antibacterial performance. The filtration layer is constructed by the PVDF / MXene electrospun nanofiber membrane, which has a high specific surface area and a porous structure, realizes efficient interception of ultrafine particulate matters, and the photothermal effect of MXene further enhances the antibacterial performance. The composite structure of the antibacterial layer and the filtration layer enables the material to have both high filtration efficiency (PM 0.3 blocking rate is more than 99.99%) and long-term antibacterial function, prolongs the service life of the filter material, and reduces the risk of secondary pollution.

[0025] The preparation method of the present application is simple in process, suitable for large-scale production, and has good industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 SEM images and diameter distribution graphs of TPU nanofiber membranes prepared from different concentrations of TPU; Figure 2 SEM images and diameter distribution graphs of pure TPU nanofiber membranes and TZ nanofiber membranes with different ZIF-8 concentrations; Figure 3 The determination result graph of the surface water contact angle of the pure TPU nanofiber membrane and the TZ nanofiber membrane with different ZIF-8 concentrations; Figure 4 The tensile stress-strain curve graph of the pure TPU nanofiber membrane and the TZ nanofiber membrane with different ZIF-8 concentrations; Figure 5 The porosity analysis graph of the pure TPU nanofiber membrane and the TZ nanofiber membrane with different ZIF-8 concentrations; Figure 6 The antibacterial performance graph of the pure TPU nanofiber membrane and the TZ nanofiber membrane with different ZIF-8 concentrations; Figure 7 The cell activity (%) of the pure TPU nanofiber membrane and the TZ nanofiber membrane with a ZIF-8 concentration of 0.6% changes with time trend graph; Figure 8 The influence graph of fiber diameter on the pressure drop of TPU and TZ nanofiber membranes with different ZIF-8 concentrations; Figure 9 SEM images and diameter distribution of PVDF nanofiber membranes with different concentrations; Figure 10 SEM images and diameter distribution of pure PVDF nanofiber membranes and PM nanofiber membranes with different concentrations of MXene; Figure 11 Surface water contact angle measurement results of pure PVDF nanofiber membranes and PM nanofiber membrane samples with different concentrations of MXene; Figure 12 Tensile stress-strain curve of pure PVDF nanofiber membranes and PM nanofiber membranes with different concentrations of MXene; Figure 13 Porosity analysis of pure PVDF nanofiber membranes and PM nanofiber membranes with different concentrations of MXene; Figure 14 Antibacterial performance of pure PVDF nanofiber membranes and PM nanofiber membranes with different concentrations of MXene; Figure 15 Bacteriostatic rate statistics of pure PVDF nanofiber membranes and PM nanofiber membranes with different concentrations of MXene; Figure 16 Cell viability (%) of pure PVDF nanofiber membranes and PM nanofiber membranes with 6% concentration of MXene over time trend graph; Figure 17 Effect of fiber diameter on pressure drop of PVDF and PM nanofiber membranes with different concentrations of MXene; Figure 18 TZ-PM mask structure schematic diagram; Figure 19 TZ-PM mask colony formation measurement results after actual use for 6, 12, and 24 hours; Figure 20 Filtering and air permeability performance evaluation of the mask. DETAILED DESCRIPTION

[0027] The embodiments of the present application will be described in detail below, and the embodiments described below are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0028] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0029] Unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art.

[0030] In the present document, where values are described as ranges, it is to be understood that the disclosure includes disclosure of all possible sub-ranges within the described range, and specific numerical values falling within the described range, whether explicitly stated or not.

[0031] In the present document, the terms "first", "second", "third", etc. in relation to "first aspect", "second aspect", "third aspect", etc. are only used for descriptive purposes and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implying that the indicated technical features are of importance or quantity. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of a non-exhaustive enumeration and should be understood not to constitute a closed limitation of the number.

[0032] The embodiment of the present application provides a preparation method of a high-efficiency air filtration nanofiber membrane with persistent antibacterial performance, which is composed of a polyurethane nanofiber membrane (TPU / ZIF-8) loaded with MOF (ZIF-8) and a polyvinylidene fluoride (PVDF) nanofiber membrane (PVDF / MXene) loaded with MXene. When exposed to particulate pollution, the first PVDF / MXene layer can first filter the particulate matter (the filtration efficiency is more than 99.99%), and also has good antibacterial performance (MXene itself has antibacterial performance and also has photothermal antibacterial performance under photothermal conditions). The lower TPU / ZIF-8 nanofiber layer has good antibacterial performance (bacteriostatic rate > 99%), and the persistent release of ZIF-8 improves the persistent use effect. In the field of air filtration, it has broad application prospects.

[0033] Characterization methods and performance tests 1. Scanning electron microscope (SEM) The scanning electron microscope (SEM) was used to observe the morphology and structure of the nanofiber. Before sample analysis, the conductive carbon tape was fixed on the sample table to ensure firm adhesion. To enhance conductivity and prevent charge effects during imaging, the sample was treated with 90 seconds of gold spraying by sputter coating instrument. The SEM working acceleration voltage was set to 10 kV, and high-resolution images were collected by different magnifications (5,000 times to 50,000 times) to analyze the fiber diameter, surface features and overall morphology of the nanofilm. ImageJ software was used to measure the fiber diameter of the obtained images.

[0034] 2. Water contact angle A water droplet contact angle tester from YUNFAN (Tianjin) Instruments Co., Ltd. was used to measure the contact angle of selected samples. Water droplets were added to the surface of electrospun samples using a syringe, and the static water contact angle on the sample surface in air was measured within 30 seconds after the droplet was deposited at room temperature. Each sample was measured 5 times, and five independent samples were prepared for each experimental condition.

[0035] 3. Mechanical properties The mechanical properties of nanofiber membranes were evaluated using a universal tensile testing machine. The samples were prepared by cutting into thin strips with dimensions of 5 mm (width) x 50 mm (length). Each sample was firmly fixed between the upper and lower clamps of the tensile testing machine with an initial clamping distance of 20 mm. The test was conducted at a constant crosshead speed of 40 mm / min under controlled environmental conditions (room temperature: 25°C, relative humidity: 65%). During the test, the tensile stress-strain curve was recorded in real time by the instrument software. The sample was stretched until it broke under automatic program control. Three samples of each nanofiber material were tested to ensure reproducibility, and the average values of tensile strength, elongation at break, and Young's modulus were calculated.

[0036] 4. Membrane porosity The porosity of the prepared membranes was quantitatively determined using the geometric density method. The mass (m) of the sample was measured using a precision analytical balance. The cross-sectional area (A = 5 cm²) was calculated by measuring the length and width using a digital caliper. At the same time, the thickness (t) was determined by taking the average of five measurements at different locations on the sample surface using a digital micrometer. For the TPU and PVDF polymer matrices, theoretical densities (p) of 1.071 g / cm³ and 1.78 g / cm³ were applied, respectively. The percentage of porosity was then calculated using the following formula: .

[0037] 5. Antimicrobial performance test The antimicrobial activity of the samples against standard strains of Staphylococcus aureus and Escherichia coli was evaluated according to the shaking method (GB / T 20944 Part 3). After the standard slant strain was cultured, serial dilutions (10-fold gradient) were made with phosphate buffer to the target bacterial solution concentration. Sterile treated membrane samples (circular samples with a diameter of 1 cm) were immersed in 1 mL of bacterial suspension (900 μL PBS + 100 μL diluted bacterial solution) and incubated for 24 hours at 37°C with continuous shaking. After the incubation was completed, 20 μL of the suspension was evenly spread on an agar plate using a sterile spreader, and incubated at 37°C for another 24 hours. By comparing the number of viable bacteria in the experimental group (antibacterial sample) and the control group (blank sample), the inhibition rate was calculated according to the formula: where: W b- Viable count of blank sample after 24 hours of shaking.

[0038] Wc - Viable count of antimicrobial sample after 24 hours of shaking.

[0039] 6. Cytotoxicity evaluation Cell viability assay was performed to evaluate the cytocompatibility of nanofiber with mouse C2C12 myoblast cells. C2C12 cells were seeded in 24-well plates at a density of 4 x 10 4 cells per well and pre-cultured for 24 hours at 37°C in a 5% CO2 humidified environment to allow cell adhesion. After cell adhesion, nanofiber samples (1 cm diameter circular samples) were added to the experimental group, while no material was added to the control group.

[0040] Cells were cultured for 1, 2, and 3 days, respectively, with fresh medium changed daily. At each time point, nanofiber and medium were gently removed, and cells were washed with phosphate buffer. Live / dead cell staining was performed according to the reagent instructions. After staining, residual dye was removed by PBS washing.

[0041] Fluorescent images were collected using an inverted fluorescence microscope, and multiple fields of view were randomly selected for each well to ensure representative analysis. ImageJ software was used to quantitatively calculate cell survival rate, i.e., the percentage of live cells (green fluorescence) in the total number of cells (live cells + dead cells) in each field of view.

[0042] 7. Filtration efficiency The filtration efficiency of nanofiber membranes was evaluated using a customized particle filtration efficiency tester based on laser scattering method (Shanghai Pangfang Electronics Technology Co., Ltd.). This instrument can detect particles in four size ranges: 0.3-1.0 pm, 1.0-2.5 pm, 2.5-10 pm, and >10 pm.

[0043] First, the instrument was preheated to a stable state, and after all parameters were normally displayed on the screen, a 5 x 5 cm nanofiber membrane sample was prepared, carefully loaded into the test fixture, and ensured to be locked in place. Mosquito incense smoke source was placed in the particle generation cabin, and the upper cover was sealed to maintain a controlled environment. The test was carried out at a gas flow rate of 4 L / min and a gas pressure of 0.02 MPa for 2 minutes.

[0044] During the test, the instrument display screen data was photographed in real time by a smartphone. After the test, the recorded data was imported into Excel for analysis, and the average concentration of particles before and after filtration was calculated, respectively. The filtration efficiency was calculated according to the following formula:

[0045] In the formula: E - Filtration efficiency; N b- the number of airborne particles before filtration; Na - the number of airborne particles after filtration.

[0046] 8. Water Vapor Transmission Rate (WVTR) The water vapor transmission rate (WVTR) was determined using a modified gravimetric method. A cylindrical glass bottle with a 36 mm opening diameter (cross-sectional area of 10.18 cm2) containing deionized water was sealed with a test film to ensure no liquid leakage and placed in a constant temperature and humidity environment (37°C, 90% RH). After 24 hours, the weight loss caused by water vapor penetration was measured by an analytical balance, and the WVTR was calculated according to the following formula:

[0047] In the formula: W 0 - the initial mass of the device (g); W 1 - the final mass after 24 hours (g); A - the effective permeation area (cm2); t - the duration of the test (days).

[0048] 9. Qualitative air permeability evaluation A simple experimental device was used to qualitatively evaluate the air permeability of PM and TZ nanofiber membranes. A beaker containing hot water at 100°C was sealed with a prepared nanofiber membrane, and an empty beaker of the same size was inverted on top of the sealed beaker. After a few seconds, dense water droplets formed on the inner wall of the empty beaker, indicating that water vapor had penetrated the membrane. This qualitative method directly presents the air permeability characteristics of the membrane.

[0049] In the embodiments of the present application: Synthesis of ZIF-8: 4.54 g of 2-methylimidazole and 0.22 g of zinc nitrate hexahydrate were dissolved in 80 ml of deionized water, and stirred at room temperature for 20 minutes. Then the uniform solution was transferred to a polytetrafluoroethylene-lined autoclave, and heated at 37°C for 6 hours. After the reaction was completed, ZIF-8 nanoparticles were obtained by centrifugal separation, and washed with methanol several times to remove unreacted precursors and impurities. Finally, the purified nanoparticles were placed in a 37°C oven for drying for 24 hours to obtain ZIF-8 material.

[0050] Synthesis of MXene First, prepare the etching solution: dissolve 1 g of lithium fluoride (LiF) in 20 mL of 9M hydrochloric acid (HCl). During the etching process, 1 g of Ti3AlC2 powder is gradually added to the pre-mixed etching solution under continuous magnetic stirring (350 rpm). The reaction system is maintained at 35°C in a lined container for 24 hours.

[0051] After etching, rinse thoroughly with deionized water to remove residual acid and byproducts. Centrifuge at 3500 rpm for 5 minutes, discard the supernatant, repeat the process until the supernatant pH reaches about 6. Dark green supernatant rich in MXene layers is centrifuged at 3500 rpm for 30 minutes to separate MXene, and the resulting suspension is ultrasonically treated in an ice water bath for 1 hour to achieve uniform exfoliation. Finally, the exfoliated MXene suspension is dried in a vacuum oven at 60°C for 12 hours to obtain a stable MXene powder product without liquid layering.

[0052] Exploration Example 1-1 The method for preparing the TPU nanofiber membrane includes the following steps: dissolving TPU (polyurethane) in a mixed solvent of N,N-dimethylformamide and acetone in a volume ratio of 1:1, continuously stirring to form a TPU solution with a TPU concentration of 6%; and using electrospinning to prepare the TPU nanofiber membrane; and the parameters for electrospinning are as follows: a spinning voltage of 30 kV, a spinning speed of 1.5 mL / h, and a receiving distance of 15 cm.

[0053] Exploration Example 1-2 Different from Exploration Example 1-1, the concentration of TPU in Exploration Example 1-2 is 8%.

[0054] Exploration Example 1-3 Different from Exploration Example 1-1, the concentration of TPU in Exploration Example 1-3 is 10%.

[0055] Figure 1 SEM images and diameter distributions of the TPU nanofiber membranes prepared at different concentrations of TPU are shown ((a) 6% concentration, (b) 8% concentration, (c) 10% concentration). Table 1 shows the mechanical strength and thickness data of the TPU nanofiber membranes prepared at different concentrations. Figure 1 As can be seen from the SEM images and Table 1, the SEM images show that when the TPU concentration is increased from 6% to 8%, the uniformity of the fiber diameter is significantly improved; and this morphology optimization has a synergistic effect on the enhancement of mechanical properties. Among them, the sample with a concentration of 8% exhibits the optimal tensile strength (17.72±2.08 MPa) and elongation at break (223.47±18.65%).

[0056] Table 1 Mechanical strength and thickness data of the TPU nanofiber membranes prepared at different concentrations

[0057] Mean ± standard deviation (n=3) Example 1-1 The method for preparing a TPU / ZIF-8 nanofiber membrane (referred to as a TZ nanofiber membrane) includes the following steps: TPU (polyurethane) was dissolved in a mixed solvent of N,N-dimethylformamide and acetone with a volume ratio of 1:1, and an 8% TPU solution was formed by continuous stirring; ZIF-8 nanoparticles were added to the TPU solution, and the amount of ZIF-8 added was 0.4% of the mass of TPU, and a TZ solution was formed by continuous stirring; a TPU / ZIF-8 nanofiber membrane was prepared by electrospinning technology (spinning voltage was 20 kV, spinning speed was 2.0 mL / h, and receiving distance was 20 cm). Named TZ-0.4.

[0058] Example 1-2 The difference from Example 1-1 is that the amount of ZIF-8 added is 0.5% of the mass of TPU, and it is named TZ-0.5.

[0059] Example 1-3 The difference from Example 1-1 is that the amount of ZIF-8 added is 0.6% of the mass of TPU, and it is named TZ-0.6.

[0060] Comparative Example 1 The preparation method of the TPU nanofiber membrane includes the following steps: TPU (polyurethane) was dissolved in a mixed solvent of N,N-dimethylformamide and acetone with a mass ratio of 1:1, and an 8% TPU solution was formed by continuous stirring; a TPU nanofiber membrane was prepared by electrospinning technology (spinning voltage was 20 kV, spinning speed was 2.0 mL / h, and receiving distance was 20 cm). Named TPU.

[0061] Material characterization and performance evaluation SEM: Figure 2 SEM images and diameter distributions of pure TPU nanofiber membranes and different ZIF-8 concentration TZ nanofiber membranes; (a) pure TPU, (b) 0.4%, (c) 0.5%, (d) 0.6%; the average diameter of the nanofiber was calculated by Figure 2 It can be seen that the introduction of ZIF-8 significantly affects the fiber diameter, and with the increase of ZIF-8 concentration, the fiber diameter shows an obvious increasing trend. Specifically, the average diameter of pure TPU is 172.55 ± 87.19 nm, the average diameter of TZ-0.4 is 245.9 ± 62.53 nm, the average diameter of TZ-0.5 is 246.98 ± 102.14 nm, and the average diameter of TZ-0.6 is 248.47 ± 106.90 nm. This trend is attributed to the change of solution viscosity and electrospinning kinetics caused by the addition of ZIF-8, thereby forming thicker fibers. And the SEM images show that even if the content of ZIF-8 increases, the nanofiber still maintains a smooth and continuous morphology, indicating that ZIF-8 has good dispersibility in the TPU matrix.

[0062] Water contact angle: Figure 3 The results of the water contact angle measurements for the pure TPU nanofiber membrane and the TZ nanofiber membranes with different ZIF-8 concentrations are shown as the average values ± standard deviations of five independent experiments, with typical droplet morphology diagrams. The data measured by the water droplet contact angle tester show that the water contact angle of pure TPU is 101.97 ± 1.5°, and with the addition of ZIF-8, the water contact angle shows a systematic increasing trend, proving that ZIF-8 can effectively enhance the hydrophobicity of the membrane material. The water contact angles of TZ-0.4, TZ-0.5 and TZ-0.6 are 104.49 ± 2.3°, 109.18 ± 3.5° and 114.12 ± 5°, respectively. This change rule can be attributed to the inherent hydrophobic properties of the ZIF-8 organic linker (2-methylimidazole) and the increase in surface roughness caused by the introduction of ZIF-8 particles. The phenomenon of increasing water contact angle with increasing ZIF-8 concentration is of great significance for mask applications. A hydrophobic surface can effectively block moisture and prevent the accumulation of water vapor generated by breathing, both improving the comfort of wearing and inhibiting the growth of bacteria (most bacteria thrive in humid environments). For mask applications, a water contact angle of 100°-130° is considered an ideal range, which can strike a balance between hydrophobicity and breathability and comfort.

[0063] Mechanical properties Figure 4 The tensile stress-strain curves of the pure TPU nanofiber membrane and the TZ nanofiber membranes with different ZIF-8 concentrations are shown in the figure. With the increase of ZIF-8 concentration, the mechanical properties of the composite material show a clear pattern. Pure TPU shows the highest tensile strength, while the introduction of ZIF-8 leads to a gradual decrease in mechanical properties. The measured tensile strength values of pure TPU, TZ-0.4, TZ-0.5 and TZ-0.6 are 32.39 MPa, 29.40 MPa, 28.87 MPa and 24.82 MPa, respectively, showing a continuous downward trend with the increase of ZIF-8 loading.

[0064] This decrease in tensile strength can be attributed to the following factors: a higher ZIF-8 concentration may cause particle agglomeration, forming stress concentration points in the TPU matrix. These agglomerates, as defect points, damage the structural integrity of the composite material. In addition, the interface between ZIF-8 particles and the TPU matrix may not be able to effectively transfer stress, causing the material to fail earlier under tensile load.

[0065] The stress-strain curves also indicate that the ductility of the materials decreases with increasing ZIF-8 concentration. This suggests that the ZIF-8 particles limit the ability of the polymer chains to move, thereby weakening the material's ability to plastically deform before breaking. The simultaneous decrease in tensile strength and ductility indicates a trade-off between maintaining mechanical properties and obtaining the functional benefits of ZIF-8.

[0066] Membrane porosity The porosity of the nanofiber is a key parameter in the application of antibacterial masks, which not only affects the antibacterial performance, but also relates to the air permeability and wearing comfort of the mask.

[0067] Figure 5 Porosity analysis chart of pure TPU nanofiber membrane and TZ nanofiber membrane with different ZIF-8 concentrations. Data in the form of mean ± standard deviation, derived from five independent experiments. With statistically significant differences) by Figure 5 It can be seen that with the increase of ZIF-8 loading, the porosity gradually rises from 71.99 ± 0.26% of pure TPU to 74.78 ± 0.26% of the TZ-0.6 sample with the highest ZIF-8 concentration.

[0068] The increase in porosity of TZ (TZ-0.4, TZ-0.5 and TZ-0.6) nanofiber membrane can be attributed to the following factors: First, ZIF-8 nanoparticles produce additional voids in the fiber matrix due to their crystal structure and interfacial gaps formed with TPU polymer; Second, SEM analysis shows that the increase in fiber diameter caused by higher ZIF-8 loading may promote the formation of more open pore structures between fibers. The porosity range of 71.99-74.78% indicates that the membrane material has high porosity characteristics suitable for filtration applications, effectively balancing particle capture efficiency and air flow resistance.

[0069] Antibacterial performance evaluation: Figure 6 Antibacterial performance chart of pure TPU nanofiber membrane and TZ nanofiber membrane with different ZIF-8 concentrations, where (a) is the colony count; (b) is the antibacterial circle experiment, where a is pure TPU, b is TZ-0.4, c is TZ-0.5, d is TZ-0.6, (c) is the antibacterial rate statistics, (d) is the antibacterial circle diameter statistics.

[0070] By Figure 6It can be seen that the introduction of ZIF-8 into the TPU matrix can significantly improve the ability of the material to inhibit bacterial growth compared with pure TPU, and the antibacterial effect is proportional to the increase of ZIF-8 loading. The colony count results show that compared with the blank control group and pure TPU, the TZ composite material can significantly reduce the number of bacterial colonies. For E. coli, the antibacterial rate increased from 18% for pure TPU to 99.66% for TZ-0.4, 99.74% for TZ-0.5, and 99.82% for TZ-0.6; for S. aureus, the antibacterial rate increased from 35.25% for pure TPU to 99.87% for TZ-0.4, 99.91% for TZ-0.5, and 99.93% for TZ-0.6. The significant improvement in antibacterial performance can be attributed to ZIF-8: its high specific surface area and porous structure provide sufficient sites for bacterial cell interaction, which can lead to physical damage to the bacterial cell membrane or chemical interference with cell processes, ultimately resulting in bacterial inactivation. In addition, the zinc ions released by ZIF-8 can also enhance the antibacterial activity, which can destroy the bacterial cell membrane and inhibit enzyme activity. The uniform distribution of ZIF-8 in the TPU matrix ensures the consistency of the antibacterial effect in the material, which is crucial for air filtration membranes - stable antibacterial performance can effectively filter and inactivate bacteria in the air.

[0071] It can be seen from the antibacterial circle experiment that a clear antibacterial circle is formed around the TZ composite material, and its diameter increases with the increase of ZIF-8 content. For E. coli, the diameter of the antibacterial circle increased from 0 mm (no antibacterial activity) for pure TPU to 1.8 mm for TZ-0.4, 2 mm for TZ-0.5, and 3 mm for TZ-0.6; for S. aureus, it increased from 0 mm for pure TPU to 2.1 mm for TZ-0.4, 2.8 mm for TZ-0.5, and 3.2 mm for TZ-0.6. The presence of the antibacterial circle indicates that the composite material not only inhibits the growth of surface bacteria, but also releases antibacterial components to the surrounding medium, forming a more extensive protective effect, which is particularly important for air filtration membranes for masks, as the material needs to prevent bacterial colonization on its surface and in the adjacent area.

[0072] The antibacterial circle of S. aureus is larger than that of E. coli, indicating that the composite material has more effect on gram-positive bacteria. This difference may be due to the difference in cell wall structure between the two types of bacteria: gram-positive bacteria (such as S. aureus) have a thick peptidoglycan layer, which may be more susceptible to the physical and chemical effects of ZIF-8; while gram-negative bacteria (such as E. coli) have an additional outer membrane structure, which may have some resistance to antibacterial agents. However, significant antibacterial circles were observed for both strains, demonstrating that the TZ composite material has broad-spectrum antibacterial activity and is suitable for filtration membranes that protect against a variety of air pathogens.

[0073] Cytotoxicity evaluation: Figure 7The cell activity (%) of pure TPU nanofiber membranes and TZ nanofiber membranes with a 0.6% ZIF-8 concentration is shown as a trend over time. The sustained stability of cell activity measurements is crucial for filtration applications. Data from 24 to 72 hours show that the cell activity of the TZ nanofiber membrane consistently decreased by less than 3%, indicating extremely low leaching of zinc ions or other harmful components. This stability contrasts sharply with traditional silver-based antimicrobial filters—which often experience increased cytotoxicity over time due to continuous ion migration. Stable cell activity and continuously enhanced antimicrobial effects together suggest that TZ composites are an ideal alternative for long-term filtration applications such as medical facilities or public transportation systems. These results demonstrate that the introduction of ZIF-8 successfully optimizes the balance between antimicrobial performance and biosafety. Although the cell activity (91.9%) of the TZ material is slightly lower than that of pure TPU, it remains well within the safe threshold range for handling airborne pathogens. This strategy of trading minimal biocompatibility for significant antimicrobial performance gains provides a key advantage in constructing filtration systems to address pandemic threats.

[0074] Filtration performance: Table 2 shows the comparison of particulate matter quantity and concentration before and after filtration for each sample. The filtration performance of the four samples (TPU, TZ-0.4, TZ-0.5, and TZ-0.6) was evaluated, primarily targeting PM2.5. 1.0 PM 2.5 PM 10 The removal efficiency and particle count of particles with diameters >0.3µm and >0.5µm were analyzed. Table 2 shows that the TZ nanofilm of this invention effectively removes PM2.5. 10 (≤10µm), PM 2.5 (≤2.5µm), PM 1.0 It has a filtration efficiency of ≥99.98% for particles ≤1.0µm, >0.5µm, and >0.3µm.

[0075] Table 2 Comparison of particulate matter quantity and concentration before and after filtration for each sample

[0076] Relationship between fiber diameter and pressure drop in TZ nanofiber membranes Figure 6 To investigate the effect of fiber diameter on the voltage drop of pure TPU nanofiber membranes and TZ nanofiber membranes, the following methods were used: Figure 6It can be seen that the pure TPU sample fiber diameter is the smallest (172.55 nm), but presents the highest pressure drop (89.2 Pa); in contrast, as the ZIF-8 concentration increases (0.4-0.6 %), the TZ nanofiber membrane fiber diameter gradually increases (245.9-248.47 nm), but the pressure drop continuously decreases (82.5-70.2 Pa). The reason for the analysis may be that the integration of ZIF-8 changes the fiber morphology, which may promote the airflow through by reducing fiber entanglement, increasing fiber spacing, or forming a more open network structure.

[0077] Water vapor transmission rate (WVTR) The WVTR characteristics of pure TPU and TZ nanofiber membranes were systematically evaluated by the weight cup method, as shown in Table 3. From Table 3, the WVTR values of all test membranes are highly close (0.111-0.116 g / cm 2 / 24h), indicating that the introduction of ZIF-8 has little effect on the moisture permeability of the material. The reference WVTR of the TPU membrane is 0.111 g / cm 2 / 24h, and the TZ nanofiber membrane only presents a slight fluctuation: the WVTR of TZ-0.4 and TZ-0.6 samples is slightly higher (0.115 and 0.116 g / cm 2 / 24h, respectively), which is only increased by 3.6% and 4.5% compared with pure TPU.

[0078] Table 3 WVTR data of pure TPU and TZ nanofiber membranes

[0079] Exploration Example 2-1 The method of the PVDF nanofiber membrane comprises the following steps: dissolving PVDF in a mixed solvent with a volume ratio of N,N-dimethylformamide and acetone being 7:3, continuously stirring to form a PVDF solution with a concentration of 10% of PVDF; and preparing a PVDF nanofiber membrane by electrospinning. The parameters of electrospinning are as follows: the spinning voltage is 12 kV, the spinning speed is 2 mL / h, and the receiving distance is 15 cm.

[0080] Exploration Example 2-2 The difference from Exploration Example 2-1 is that the concentration of PVDF in Exploration Example 2-2 is 8%.

[0081] Exploration Example 2-3 The difference from Exploration Example 2-1 is that the concentration of PVDF in Exploration Example 2-3 is 12%.

[0082] Figure 9 SEM images and diameter distribution of PVDF nanofibers with different concentrations, wherein a) 8%, b) 10%, and c) 12%. The diameter distribution is shown in the lower right corner of each image. Figure 9It can be seen that when the concentration is 8%, the fibers present a relatively uniform and fine morphology with an average diameter of 70.41 ± 38.16 nm. This is consistent with the lower tensile strength (8.34 ± 1.3 MPa) and elongation at break (18.23 ± 2.9%) in Table 4, indicating that the finer fibers, although delicate in structure, may lack mechanical stability. The fiber diameter of the sample with a concentration of 10% increases slightly (72.46 ± 38.04 nm), but the mechanical properties improve significantly, with a tensile strength of 18.55 ± 2.8 MPa and an elongation at break of 38.90 ± 5.8%. This indicates that a moderate increase in PVDF concentration can enhance the structural integrity while maintaining fiber flexibility. When the concentration increases to 12%, the fibers become significantly thicker (161.8 ± 91.99 nm) and less uniform, with a wider diameter distribution range. Although the tensile strength (33.20 ± 4.2 MPa) and elongation at break (86.42 ± 12.1%) are significantly improved at this concentration, the film thickness (0.027 ± 0.004 mm) increases compared to the 10% sample (0.018 ± 0.002 mm). This mechanical enhancement may be due to the strengthening of molecular chain entanglement and fiber interaction, thereby improving the load capacity. However, the widening of the diameter distribution and the decrease in thickness may affect the filtration efficiency - thicker fibers generally correspond to larger pore sizes. The 10% concentration exhibits the best balance: moderate mechanical strength (18.55 ± 2.8 MPa) and fiber uniformity (72.46 ± 38.04 nm), providing an ideal foundation for sustained filtration performance.

[0083] Table 4 Diameter, mechanical strength, and thickness data of PVDF nanofiber films at different concentrations

[0084] Mean ± standard deviation (n = 3) Example 2-1 A method for preparing a PVDF / MXene nanofiber film (referred to as PM nanofiber film), comprising the following steps: Dissolve PVDF in a mixed solvent of N,N-dimethylformamide and acetone with a volume ratio of 7:3, continuously stir to form a 10% PVDF solution; add MXene to the PVDF solution, the addition amount of MXene is 4% of the mass of PVDF, continuously stir to form a PM solution; prepare a PVDF / MXene nanofiber film by electrospinning technology (spinning voltage is 14 kV, spinning speed is 1.5 mL / h, receiving distance is 20 cm). Named as PM-4.

[0085] Example 2-2 The difference from Example 2-1 is that the addition amount of MXene in Example 2-2 is 5% of the mass of PVDF, named PM-5.

[0086] Example 2-3 The difference from Example 2-1 is that the addition amount of MXene in Example 2-3 is 6% of the mass of PVDF, named PM-6.

[0087] Comparative Example 2 A method for preparing a PVDF nanofiber membrane, comprising the following steps: PVDF was dissolved in a mixed solvent of N,N-dimethylformamide and acetone with a volume ratio of 7:3, and continuously stirred to form a 10% PVDF solution; a PVDF nanofiber membrane was prepared by electrospinning technology (spinning voltage was 14 kV, spinning speed was 1.5 mL / h, and receiving distance was 20 cm). Named PVDF.

[0088] Material characterization and performance evaluation SEM: Figure 10 SEM images and diameter distribution of pure PVDF nanofiber membrane and PM nanofiber membrane with different MXene concentrations, wherein a) pure PVDF, b) 4%, c) 5%, d) 6%; through Figure 10 It can be seen that the nanofibers of all MXene loadings maintain a smooth and continuous structure, indicating that MXene is well dispersed in the PVDF matrix. This uniform dispersion ensures the consistency of the performance of the membrane material. Through the diameter distribution data, it can be seen that with the increase of MXene concentration, the fiber diameter shows a significant decreasing trend: the average diameter of pure PVDF is 375.36±46.05 nm, PM-4 reduces to 369.95±187.15 nm, PM-5 is 318.03±130.37 nm, and PM-6 further reduces to 267.62±101.48 nm. This diameter reduction may be due to the change in solution viscosity and electrospinning kinetics caused by the addition of MXene, thereby promoting the formation of finer fibers. The decrease in diameter indicates that the filtration performance may be improved—finer fibers usually form smaller pore sizes, which helps to enhance the capture ability of sub-micron particles such as bacteria, viruses, etc., which is crucial for mask applications.

[0089] Water contact angle: Figure 11 Water contact angle measurement results of pure PVDF nanofiber membrane and PM nanofiber membrane with different MXene concentrations (data is the average value±standard deviation of five independent experiments, with typical droplet images); through Figure 11It can be seen that the WCA of pure PVDF is 108.16±1.5°, which reflects its inherent hydrophobicity, and although MXene usually presents hydrophilicity due to the presence of -OH, -O- and other functional groups, its addition causes a slight but continuous increase in WCA: PM-4 (4% MXene) rises to 111.34±3.3°, PM-5 (5% MXene) and PM-6 (6% MXene) reach 117.02±4.5° and 117.50±5°, respectively. The possible reason for the analysis is: the regulation effect of MXene on surface roughness. Although MXene itself is hydrophilic, the micro-nano surface structure formed after its introduction into the PVDF matrix enhances the hydrophobicity. In practical applications (such as masks), the WCA values of this series of composite materials are all in the ideal interval of 100°-130°, which can ensure the balance between moisture resistance and air permeability.

[0090] Mechanical properties: Figure 12 The tensile stress-strain curves of pure PVDF nanofiber membrane and PM nanofiber membranes with different concentrations of MXene are shown in the figure. The tensile strength of pure PVDF is 31.50 MPa, while the tensile strengths of PM-4, PM-5 and PM-6 nanofiber membranes are 32.23 MPa, 32.56 MPa and 32.63 MPa, respectively. With the addition of MXene, the tensile strength of PM nanofiber membrane shows a slight but continuous increase, which is attributed to the reinforcing effect of MXene, which improves the load-bearing capacity of the PVDF matrix. This improvement in mechanical properties may be due to the uniform dispersion of MXene in the polymer matrix and the strong interfacial adhesion between MXene and PVDF.

[0091] The stress-strain curves show that the ductility of PM nanofiber membranes is slightly improved compared with pure PVDF. This phenomenon indicates that the addition of MXene not only improves the tensile strength, but also maintains or slightly enhances the plastic deformation capacity of the material before fracture.

[0092] Membrane porosity Figure 13 The porosity of pure PVDF nanofiber membrane and PM nanofiber membranes with different concentrations of MXene was analyzed. The data are expressed as mean ± standard deviation, derived from five independent experiments. Indicates a statistically significant difference.

[0093] With the increase of MXene content, the porosity gradually decreased from 74.97 ± 0.25% of pure PVDF to 71.83 ± 0.26% of PM-6. With the increase of MXene loading, the porosity showed a gradual decreasing trend, which was mainly attributed to the following factors: first, the introduction of MXene nanosheets filled the voids within the fiber matrix, reducing the total pore volume; second, the decrease of fiber diameter after adding MXene may lead to more dense fiber accumulation. Although the increase of MXene content caused a slight decrease in porosity, the membrane material still maintained a high porosity level of about 71.83 ± 0.26%.

[0094] Antibacterial performance evaluation Figure 14 The antibacterial performance of pure PVDF nanofiber membrane and PM nanofiber membrane with different MXene concentrations is shown in the figure, Figure 15 The antibacterial rate statistics. Experimental data show that the addition of MXene significantly improves the material's ability to inhibit bacterial growth, and the antibacterial effect increases with the increase of MXene loading. For E. coli, the antibacterial rate increased from 16% for pure PVDF to 93.33% for PM-4, 97.37% for PM-5, and 99.73% for PM-6; for S. aureus, the antibacterial rate increased from 7.69% for pure PVDF to 94.65% for PM-4, 97.69% for PM-5, and 99.69% for PM-6. These data show that even the lowest MXene loading (PM-4) can greatly inhibit bacterial growth, while the high loading sample (PM-6) almost achieves complete inhibition. The significant improvement in antibacterial performance is mainly due to the high specific surface area and layered structure of MXene, which provides sufficient sites for bacteria-material interaction. This interaction can lead to physical damage to the bacterial cell membrane or chemical interference with cellular processes, ultimately causing bacterial inactivation. In addition, the release of metal ions (such as titanium or other transition metals) from MXene can also enhance the antibacterial activity, as they can damage the bacterial cell membrane and inhibit enzyme activity. The uniform distribution of MXene in the PVDF matrix ensures that the antibacterial effect is throughout the material, which is crucial for filtration membranes that need to continuously and effectively filter and inactivate airborne bacteria.

[0095] Cytotoxicity evaluation Figure 16The cell viability (%) of pure PVDF nanofiber membrane and PM nanofiber membrane with 6% MXene concentration as a function of time was observed for 72 hours, and all materials maintained more than 90% cell viability: the initial stage control group activity reached 97.0%, and the PVDF and PM nanofiber membrane were 95.0% and 94.0%, respectively. The slight activity decrease (2.0-3.0%) exhibited by the polymer matrix indicated that early cell-material interaction only triggered slight acute cytotoxicity. By 48 hours, cell viability continued to maintain a high level (control group 96.3%, PVDF 96.0%, and PM nanofiber membrane 95.4%), and PVDF and PM nanofiber membrane always maintained more than 95% activity, confirming that these materials did not trigger significant cell death, but regulated proliferation behavior through non-toxic mechanisms such as contact inhibition or metabolic interference. The 72-hour measurement data reinforced this trend: the control group activity was 93.5%, and the PVDF and PM nanofiber membrane were 93.0% and 92.0%, respectively. The PM nanofiber membrane activity was 1.5% lower than PVDF, suggesting that the introduction of MXene might produce a slight but persistent cytotoxic effect, but the overall activity was still within the acceptable range of biocompatible materials (>90%). The analysis found that the main mechanism of action of MXene might involve interfering with the cell division process, rather than damaging the membrane structure or inducing apoptosis.

[0096] Filtering efficiency The present application systematically evaluates the removal efficiency of different particle sizes by testing the filtering efficiency of four samples (PVDF, PM-4, PM-5, and PM-6). All samples exhibit highly consistent excellent performance: the filtering efficiency of PM 1.0 , PM 2.5 , and PM 10 is 100%, and the filtering efficiency of >0.3 µm and >0.5 µm particles is 99.98%. This high consistency between samples proves that the filtration system has excellent reproducibility and reliability, fully meeting the application requirements of strict air quality control scenarios.

[0097] Table 5 Control table of particle number or concentration before and after filtering of different samples

[0098] Relationship between PM fiber diameter and pressure drop Figure 17The effect of fiber diameter on the pressure drop of PVDF and PM-4, PM-5, and PM-6 nanofiber membranes was investigated. As can be seen from Table 17, the data showed a clear pattern: as the fiber diameter decreased, the pressure drop increased significantly. The PVDF sample with the largest fiber diameter (375.36 nm) showed the lowest pressure drop (about 82.5 Pa), while the PM-6 with the smallest fiber diameter (267.62 nm) showed the highest pressure drop (about 134 Pa).

[0099] Water vapor transmission rate (WVTR) The WVTR of pure PVDF and PM nanofiber membranes was evaluated using the weight cup method. The results are shown in Table 6. As can be seen from Table 6, the introduction of MXene caused a concentration-dependent change in moisture permeability: the reference WVTR of pure PVDF was 0.118±0.003 g / cm 2 / 24h, while the permeability of PM nanofiber membranes fluctuated between 0.114±0.002 and 0.127±0.005 g / cm 2 / 24h. Appropriate amounts of MXene can improve fiber uniformity, and excessive amounts can easily cause agglomeration. When the MXene loading increased to 5 wt%, the WVTR showed a gradual upward trend: PM-4 and PM-5 increased by 4.24% and 7.63% respectively compared to pure PVDF. This enhancement effect is due to two competing mechanisms: the hydrophilicity of MXene nanosheets may create new paths for water molecule transport, but their layered structure also increases the tortuosity of the diffusion path. The 3.4% reduction in WVTR of PM-6 suggests a threshold effect - higher loading (6 wt%) may cause nanosheet agglomeration, thereby reducing the effective diffusion path.

[0100] Table 6 WVTR data of PVDF and PM nanofiber membranes

[0101] Example 3 A method for preparing a high-efficiency air filtration nanofiber membrane with sustained antibacterial performance, comprising the following steps: Dissolve TPU in a mixed solvent of N,N-dimethylformamide and acetone in a volume ratio of 1:1, continuously stir to form an 8% TPU solution; add ZIF-8 nanoparticles to the TPU solution, the addition amount of ZIF-8 is 0.6% of the mass of TPU, continuously stir to form a TZ solution; prepare a TPU / ZIF-8 nanofiber membrane using electrospinning technology (spinning voltage is 20 kV, spinning speed is 2.0 mL / h, receiving distance is 20 cm).

[0102] The PVDF is dissolved in a mixed solvent of N, N-dimethylformamide and acetone in a volume ratio of 7:3, and a 10% PVDF solution is formed under continuous stirring; the MXene is added to the PVDF solution, and the addition amount of the MXene is 6% of the mass of the PVDF, and a PM solution is formed under continuous stirring; and the PM solution is spun on the surface of the TPU / ZIF-8 nanofiber membrane to prepare a TZ-PM composite membrane under the condition that the spinning voltage of electrospinning is 14 kV, the spinning speed is 1.5 mL / h, and the receiving distance is 20 cm.

[0103] Example 4 The preparation method of the mask in the embodiment of the application comprises the following steps: using a commercially available medical protective mask as a base carrier, and realizing precise embedding and compounding of a functional layer through structural reconstruction. Specifically, the mask is carefully cut along the edge between the outer layer and the inner layer in a sterile environment, the middle layer region is exposed, and the original middle layer is removed. The TZ-PM composite film prepared in Example 3 is cut to a size matching the mask body, and then placed flat between the inner and outer layers to make it fully adhere to the original non-woven layer. After embedding, the edges are oriented and pressed to package, so as to restore the overall sealing and mechanical stability of the mask. The final mask maintains the original appearance while realizing the synergistic integration of antibacterial and filtering functions.

[0104] The TZ-PM mask in the embodiment of the application, as shown in Figure 14 The TZ-PM mask structure comprises: (1) an outer non-woven fabric for liquid barrier and coarse particle filtration; (2) a PM nanofiber filter layer for providing high-efficiency particle capture function; (3) a TZ composite antibacterial layer for active pathogen inactivation; and (4) an inner non-woven fabric comfort layer.

[0105] Figure 19 The results of the colony-forming assay after the TZ-PM mask is used for 6, 12 and 24 hours. It can be seen from Figure 19 that no Escherichia coli colonies (no visible CFU) are detected within 12 hours of intermittent use (2 hours of use and 2 hours of rest), and the antibacterial standard is maintained at >99%. The first colony detection occurs only at the 24-hour time point. It can be seen that (1) the antibacterial components (ZIF-8 and MXene) can be continuously and effectively released in multiple use cycles; and (2) the 12-hour effective duration meets the daily use recommendation. The test results of the TZ and PM single materials and the TZ-PM mask are highly consistent, which confirms that the laboratory design has the same effectiveness in the actual product.

[0106] Figure 20For filtration and air permeability evaluation of the mask, where (a) is the filtration rate comparison of the traditional mask (N95) and TZ-PM mask (four layers) (data is the mean ± standard deviation of five independent tests); (b) the water vapor transmission test scene of TZ-PM mask (2 minutes later), the results show that TZ-PM mask achieves excellent filtration efficiency of 99.99 ± 0.013%, which is significantly better than the traditional mask (95.3 ± 0.78%). The water vapor transmission test shows excellent air permeability: visible water droplets are formed on the inner wall of the sealed beaker within two minutes of testing.

[0107] Although the embodiments of the present application have been shown and described above, it should be understood by those skilled in the art that the above embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for preparing a high-efficiency air filtration nanofiber membrane with sustained antibacterial properties, characterized by comprising the following steps: (1) TPU was dissolved in a mixed solvent of N,N-dimethylformamide and acetone and stirred continuously to form a TPU solution; ZIF-8 nanoparticles were added to the TPU solution and stirred continuously to form a TZ solution; TPU / ZIF-8 nanofiber membrane was prepared by electrospinning technology; (2) Dissolve PVDF in a mixed solvent of N,N-dimethylformamide and acetone and stir continuously to form a PVDF solution; add MXene to the PVDF solution and stir continuously to form a PM solution; (3) The PM solution from step (2) is spun and composited on the surface of the TPU / ZIF-8 nanofiber membrane to prepare a high-efficiency air filtration nanofiber membrane with continuous antibacterial properties.

2. The method according to claim 1, characterized in that, In step (1), the volume ratio of N,N-dimethylformamide to acetone is 4:6-10:

1.

3. The method according to claim 1, characterized in that, In step (1), the concentration of TPU in the TZ solution is 4-15 wt%; the amount of ZIF-8 nanoparticles added is 0.4-0.6% of the mass of TPU; preferably, the concentration of TPU in the TZ solution is 6-10 wt%; more preferably, it is 8 wt%.

4. The method according to claim 1, characterized in that, In step (1), the electrospinning settings are: spinning voltage 15-35kV, receiving distance 5-25 cm, and feed rate 1-3mL / h; preferably, the electrospinning settings are: spinning voltage 20 kV, receiving distance 20 cm, and spinning speed 2 mL / h.

5. The method according to claim 1, characterized in that, The ZIF-8 nanoparticles were prepared by dissolving 2-methylimidazole and zinc nitrate hexahydrate in deionized water, stirring thoroughly, heating at 37°C for 6 hours, centrifuging after the reaction was completed, washing with methanol several times, and then drying in an oven at 37°C for 24 hours to obtain ZIF-8 nanoparticles.

6. The method according to claim 1, characterized in that, In step (2), the volume ratio of N,N-dimethylformamide to acetone is 5:5-10:

1.

7. The method according to claim 1, characterized in that, In step (2), the concentration of PVDF in the PM solution is 6-15 wt%; the amount of MXene added is 4-6% of the mass of PVDF; preferably, the concentration of PVDF in the PM solution is 8-12 wt%; more preferably, it is 10 wt%. And / or, in step (2), the method for synthesizing MXene includes the following steps: dissolving lithium fluoride in 9M hydrochloric acid, adding Ti3AlC2 powder to the premixed etching solution under continuous magnetic stirring during the etching process, reacting at 35°C for 24 hours, washing thoroughly with deionized water after etching, centrifuging, discarding the supernatant, repeating the process until the pH of the supernatant reaches 6, centrifuging the dark green suspension rich in MXene layer at 3500 rpm for 30 minutes to separate MXene, then ultrasonically treating in an ice-water bath for 1 hour to achieve uniform peeling, and finally drying in a vacuum oven at 60°C for 12 hours to obtain a stable MXene powder product.

8. The method according to claim 1, characterized in that, In step (3), the electrospinning settings are: spinning voltage 8-16kV, receiving distance 5-25 cm, and feed rate 1-3mL / h; preferably, the electrospinning settings are: spinning voltage 14 kV, spinning speed 1.5 mL / h, and receiving distance 20 cm.

9. A high-efficiency air filtration nanofiber membrane with sustained antibacterial properties, characterized in that, It is prepared by the method comprising any one of claims 1-8.

10. The application of the high-efficiency air-filtering nanofiber membrane with sustained antibacterial properties as described in claim 9 in the preparation of antibacterial masks.

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