Air particulate filtering nanofiber membrane, and preparation method and application thereof

Abstract

The application discloses an air particulate matter filtering nanofiber membrane and a preparation method and application thereof, and comprises the following steps: dispersing fiber arborization aids, triboelectricity enhancing materials and fluorine-containing polymers in a solvent to form a spinning solution, and electrospinning the spinning solution to obtain the air particulate matter filtering nanofiber membrane; the triboelectricity enhancing materials are fluorinated modified MXene and / or fluorinated modified graphene. The spinning solution is prepared by mixing the fiber arborization aids, the triboelectricity enhancing materials and the fluorine-containing polymers, a multi-level micro-nanofiber structure is constructed by electrospinning, the gradient pore size distribution and the biomimetic tree-like topological characteristics provide a new idea for realizing the synergistic optimization of 'high interception-low air resistance', and the enhanced triboelectricity performance provides a scheme for intelligent air filtering monitoring.

Description

Technical Field

[0001] This invention relates to the field of air filtration materials technology, specifically to an air particulate matter filtration nanofiber membrane, its preparation method, and its application. Background Technology

[0002] Particulate matter pollution is one of the main forms of air pollution and has become a significant environmental problem threatening public health. Long-term exposure to high concentrations of particulate matter significantly increases the risk of respiratory and cardiovascular diseases. Therefore, developing air protection materials that combine high-efficiency filtration with good user comfort is of great importance.

[0003] Currently, electret filter materials based on meltblown nonwoven fabrics are widely used in commercial protective masks, primarily relying on electrostatic adsorption and physical interception to remove particulate matter. However, these materials are prone to charge decay in high-humidity environments or during prolonged use, leading to a significant decrease in filtration efficiency. Electrospun nanofiber membranes, due to their high specific surface area and tunable pore structure, are considered a potential alternative to traditional filter materials. However, overly dense fiber arrangement increases breathing resistance, resulting in increased pressure drop, reduced wearing comfort, and difficulty in achieving an ideal balance between high efficiency and low resistance. Furthermore, traditional air filter materials are mainly used for passive protection, making it difficult to achieve real-time sensing of environmental pollution levels and human breathing status, thus limiting the development of next-generation intelligent protective air filter materials.

[0004] Therefore, developing intelligent air filtration material systems that combine high-efficiency filtration performance, good wearing comfort, and real-time monitoring functions has become a key technological breakthrough direction for public health and environmental safety. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing an air particulate matter filtration nanofiber membrane, its preparation method, and its application. The spinning solution is prepared by mixing fiber branching agent, triboelectric enhancement material, and fluorinated polymer. Electrospinning constructs a multi-level micro / nanofiber structure. Its gradient pore size distribution and biomimetic tree-like topology provide a new approach to achieving synergistic optimization of "high-efficiency interception and low air resistance".

[0006] To address the aforementioned technical problems, the first aspect of this invention provides a method for preparing an air particulate matter filtration nanofiber membrane, comprising the following steps:

[0007] A fiber branching agent, a triboelectric reinforcing material, and a fluorinated polymer are dispersed in a solvent to form a spinning solution. The spinning solution is then electrospun to obtain the air particulate matter filtration nanofiber membrane.

[0008] The triboelectric enhancement material is fluorinated modified MXene and / or fluorinated modified graphene.

[0009] This invention adds triboelectric enhancement materials to the spinning solution, resulting in nanofiber membranes doped with functional nanomaterials prepared by electrospinning. Through microcapacitance, these membranes achieve not only high-efficiency filtration but also superior triboelectric output performance, thus providing a solution for real-time monitoring. Simultaneously, fluorinated MXene or graphene, with its surface-modified fluorinated groups, not only further enhances electronegativity but also improves the hydrophobic properties of the fiber membrane, avoiding the decrease in hydrophobicity caused by the doping of fiber branching aids (anionic surfactants).

[0010] The present invention adds a fiber branching agent (anionic surfactant) to the spinning solution, which can significantly increase the solution conductivity, promote the generation of multi-level micro and nanofiber structures, ensure the generation of branched fibers during electrospinning, and at the same time, the anions do not affect the triboelectronegativity of the fiber membrane.

[0011] The present invention uses fluorinated polymers as spinning raw materials not only to utilize their hydrophobicity to ensure the structural integrity of branched ultrafine fibers (20-50nm) under certain humidity, but also to give the fiber membrane excellent triboelectric output performance due to the high electronegativity of fluorine atoms, laying the foundation for realizing intelligent monitoring.

[0012] Furthermore, the fiber branching agent is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium stearate, and sodium laurate;

[0013] The fluorinated polymer is selected from one or more of polytetrafluoroethylene (PTFE), polytetrafluoroethylene-hexafluoropropylene (FEP), polytetrafluoroethylene-ethylene (ETFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polyvinylidene fluoride-tetrafluoroethylene (PVDF-TFE).

[0014] Furthermore, the concentration of the fluorinated polymer in the spinning solution is 14-17 wt%, the amount of the fiber branching agent added is 3-9% of the mass of the fluorinated polymer, and the amount of the triboelectric reinforcing material added is 3-12% of the mass of the fluorinated polymer.

[0015] Furthermore, the preparation method of the fluorinated modified MXene or fluorinated modified graphene is as follows: 1H,1H,2H,2H-perfluorodecyltriethoxysilane and MXene or graphene oxide are dispersed in ethanol and reacted to obtain fluorinated modified MXene or fluorinated modified graphene.

[0016] Furthermore, the electrospinning conditions are as follows: spinning voltage is 15-18 kV, spinning solution flow rate is 0.4-0.8 mL / h, spinning distance is 13-17 cm, collecting drum speed is 100-400 r / min, and relative humidity is 10-30%.

[0017] The second aspect of the present invention provides an air particulate filter nanofiber membrane prepared by the preparation method described in the first aspect.

[0018] A third aspect of the present invention provides a face mask, the face mask comprising a spunbond nonwoven fabric layer, a copper mesh electrode layer, a nanofiber membrane as described in the second aspect, and a nylon mesh layer arranged in sequence.

[0019] Furthermore, the nanofiber membrane is deposited in situ on the copper mesh electrode layer via electrospinning; the nylon mesh layer is in contact with the nanofiber membrane (they can contact and separate from each other).

[0020] The copper mesh electrode layer has a mesh size of 100-300.

[0021] Furthermore, the nylon mesh layer is 200-400 mesh, and nano-silver is deposited in situ on both sides. Specifically, the nylon mesh layer is immersed in a 0.05-0.1 mol / L silver nitrate aqueous solution, and 10-15% of the solution volume of methanol is added. The mixture is stirred for 30-60 minutes under light-protected conditions, and then placed under a xenon lamp for continuous irradiation for 2-3 hours. The nylon mesh layer with in situ deposited nano-silver is obtained by photoreduction.

[0022] Furthermore, the mask connects the copper mesh electrode layer to an oscilloscope and an electrometer via wires or outputs signals via a wireless module, for intelligent monitoring of human breathing status, real-time air pollution status, and real-time filtration efficiency.

[0023] The mask structure constructed in this invention achieves triboelectric output for real-time monitoring: the inner layer is ordinary commercial spunbond nonwoven fabric to isolate moisture during exhalation and avoid affecting the electrodes; the outer layer of the spunbond nonwoven fabric is a copper mesh electrode layer, on which is a multi-level nanofiber membrane deposited in situ, the two forming an integrated structure to ensure stable output of triboelectric signals; the outer layer of the nanofiber membrane is a nano-silver modified nylon mesh layer. Nylon is a positive triboelectric material relative to fluorinated polymers, and its positive triboelectric performance can be further improved by in-situ assembly of nano-silver. When a person breathes, the nanofiber membrane is attached to the copper mesh and its position remains relatively unchanged, while the nylon mesh layer collides and separates from the nanofiber membrane with the reciprocating airflow during exhalation and inhalation, thereby generating triboelectric induced charges on the copper mesh electrodes, forming an open-circuit voltage and short-circuit current in the external circuit.

[0024] The beneficial effects of this invention are:

[0025] This invention utilizes anionic surfactants to induce electrostatic stretching, achieving in-situ splitting and refinement of fibers during electrospinning, and successfully constructing a fiber membrane with a micro-nano multi-level structure. By forming a high-density nanoscale fiber network between the main fibers, the fiber membrane is endowed with excellent particulate matter filtration performance. Without increasing the thickness of the fiber membrane, good air permeability is ensured, achieving synergistic optimization between filtration efficiency and breathing resistance, and providing an ideal structural basis for constructing high-performance air filtration materials.

[0026] This invention involves doping nanofiber membranes with fluorinated MXene or graphene, creating a microcapacitor effect within the membrane and significantly improving its triboelectric output performance. Combined with the fiber refinement induced by anionic surfactants and the strong negative charge imparted by fluorination, these multiple synergistic effects lay the foundation for active intelligent monitoring based on triboelectric properties. Specifically, the fluorinated MXene or graphene constructs abundant microcapacitor structures within the fiber membrane, effectively enhancing charge capture and storage capabilities. This allows the nanofiber membrane to generate higher and more stable triboelectric signals under mechanical triggering, providing ample output for self-powered sensing. Simultaneously, the anionic surfactants induce fiber splitting and refinement, increasing the fiber surface area and interfacial contact sites per unit volume, while fluorination further strengthens the material's negative charge. The synergistic effect of these two factors significantly improves the surface charge density and charge stability of the fiber membrane, thereby optimizing the sensitivity and reliability of the triboelectric response.

[0027] The co-doping of fluorinated MXene or graphene in this invention effectively avoids the increase in hydrophilicity caused by the addition of anionic surfactants to regulate the structure of the fiber membrane, thereby significantly improving the environmental resistance of the nanofiber membrane and enabling it to maintain stable filtration and sensing functions in high humidity environments.

[0028] The micro-nano multi-level nanofiber membrane of this invention not only ensures high-efficiency and low-resistance particulate matter filtration performance, but also serves as a structural carrier for the triboelectric functional layer, realizing the dual functions of "filtration + sensing" and avoiding the problems of increased thickness and increased breathing resistance caused by the additional sensing layer.

[0029] The nanofiber membrane of this invention can output electrical signals in real time without relying on an external power source, simply through everyday mechanical triggering such as breathing. It can be used to monitor physiological and environmental parameters such as airborne particulate matter load, breathing frequency and depth, thus constructing a technological path for the development of next-generation smart protective materials. Attached Figure Description

[0030] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 SEM image of the nanofiber membrane prepared in Comparative Example 1;

[0032] Figure 2 SEM image of the nanofiber membrane prepared in Comparative Example 2;

[0033] Figure 3 SEM image of the nanofiber membrane prepared in Comparative Example 3;

[0034] Figure 4 A comparison diagram of the conductivity and viscosity of the spinning solutions prepared in Comparative Examples 1-3;

[0035] Figure 5 The images in a and b represent SEM images of the nanofiber membranes prepared in Examples 1-4, respectively.

[0036] Figure 6 Viscosity and conductivity curves of spinning solutions prepared with different concentrations of F-MXene for Comparative Example 2 and Examples 1-4;

[0037] Figure 7 For comparison of the PSL aerosol filtration performance containing PM0.3 particles in Comparative Examples 1-3 and Example 3;

[0038] Figure 8 This is a SEM image of the nanofiber membrane prepared in Example 3 after filtration.

[0039] Figure 9 Photographs, SEM images, and corresponding silver elemental mapping diagrams of silver-modified nylon mesh;

[0040] Figure 10 A comparison of the triboelectric output voltage of the nanofiber membrane prepared in Example 3 and the nylon mesh before and after modification during contact friction.

[0041] Figure 11 A comparison of the triboelectric output voltages of the nanofiber membranes prepared in Comparative Examples 1-5 and Example 3 when they are subjected to contact friction with modified nylon mesh.

[0042] Figure 12 Statistical diagrams of water contact angles for nanofiber membranes prepared in Comparative Examples 1-4 and Example 3;

[0043] Figure 13The graph shows a comparison of the triboelectric output voltage of the nanofiber membranes prepared in Example 3 and Comparative Example 4 under different humidity conditions.

[0044] Figure 14 This is a schematic diagram of the intelligent mask with autonomous monitoring function prepared in Example 3;

[0045] Figure 15 This is a schematic diagram of the working mechanism of the smart mask with autonomous monitoring function prepared in Example 3;

[0046] Figure 16 The image shows the monitoring signal of the human respiratory state by the smart mask with autonomous monitoring function prepared in Example 3.

[0047] Figure 17 This is a schematic diagram of a testing device for quantitative air pollutant filtration analysis using mosquito coils as simulated particulate matter.

[0048] Figure 18 This is a comparison of the triboelectric output voltage of the nanofiber membrane prepared in Example 3 after filtering and retaining different pollutant particles;

[0049] Figure 19 The graph shows the change in the triboelectric output voltage of the nanofiber membrane prepared in Example 3 after continuous filtration in different PM2.5 concentration environments for 60 seconds. (a) is a comparison graph of output voltage, and (b) is a graph showing the change in voltage decay rate.

[0050] Figure 20 The images show the performance degradation of the nanofiber membrane prepared in Example 3 after filtering and retaining different amounts of mosquito coil particles. (a) is a graph showing the output voltage degradation, (b) is a graph showing the output voltage change, (c) is a curve showing the filtration performance change after retaining different amounts of particles, and (d) is a SEM image showing the filter performance after retaining different amounts of particles. Detailed Implementation

[0051] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] The preparation method of fluorinated modified MXene (F-MXene) used in the following examples and comparative examples includes the following steps: 50 mg of monolayer MXene powder was added to 40 mL of an ethanol solution of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFOTS, concentration 5 wt%), and the mixture was magnetically stirred at room temperature for 8 hours. After the reaction was completed, the precipitate was collected by centrifugation at 12000 rpm and repeatedly washed with ethanol to remove excess PFOTS. Finally, it was freeze-dried to obtain F-MXene powder.

[0053] The preparation method of the silver-modified nylon mesh used in the following examples and comparative examples includes the following steps: cutting a 300-mesh nylon mesh into a shape of 20cm × 10cm, immersing it in a 0.05 mol / L silver nitrate aqueous solution, adding 10% methanol by volume of the solution, and magnetically stirring for 60 min under light-protected conditions to allow for sufficient ion adsorption; then turning on a 300 W xenon lamp (with light intensity controlled at approximately 100 mW / cm²). 2 The nylon mesh layer with in-situ deposited nano-silver was continuously irradiated for 120 minutes in a constant temperature water bath at 25 ℃. After being removed, it was rinsed multiple times with deionized water and dried in a vacuum drying oven at 60 ℃.

[0054] Example 1

[0055] This embodiment relates to a method for preparing a smart mask with autonomous monitoring function, including the following steps:

[0056] S1. Prepare a solvent by mixing N,N-dimethylformamide (DMF) and acetone at a volume ratio of 4:1. Add F-MXene to the mixed solvent and disperse it by ultrasonication. The amount of F-MXene added is 3 wt% of the mass of the PVDF added later.

[0057] S2. Add PVDF powder and stir thoroughly at 60°C to prepare a PVDF spinning solution with a concentration of 15 wt%.

[0058] S3. Add sodium dodecylbenzenesulfonate (SDBS) at 7 wt% of PVDF mass, and continue stirring for 2 hours.

[0059] S4. Wrap a 200-mesh copper mesh around a collecting roller. Perform electrospinning under a constant temperature of 25℃ and relative humidity of 25%. Adjust the spinning parameters as follows: voltage 16 kV, spinning solution flow rate 0.5 mL / h, collecting distance 15 cm, and roller receiver rotation speed 300 r / min. After continuous collection for 2 hours, a multifunctional PVDF / F-MXene / SDBS (PFS) nanofiber membrane with copper mesh is obtained.

[0060] S5. Cut the spunbond nonwoven fabric and the nanofiber membrane with copper mesh into 19cm × 10cm sizes, and assemble them with the modified nylon mesh in sequence (with the copper mesh side close to the spunbond nonwoven fabric and the nanofiber membrane side close to the modified nylon mesh) to form a mask.

[0061] Example 2

[0062] The difference between this embodiment and Embodiment 1 is that the amount of F-MXene added is 6 wt% of the mass of PVDF, while other steps and parameters remain unchanged.

[0063] Example 3

[0064] The difference between this embodiment and Embodiment 1 is that the amount of F-MXene added is 9 wt% of the mass of PVDF, while other steps and parameters remain unchanged.

[0065] Example 4

[0066] The difference between this embodiment and Embodiment 1 is that the amount of F-MXene added is 12 wt% of the mass of PVDF, while other steps and parameters remain unchanged.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 3 is that F-MXene and SDBS are not added to the spinning solution, meaning the prepared nanofiber membrane is a pure PVDF nanofiber membrane. Specifically, the following steps are included:

[0069] S1. Prepare a solvent by mixing N,N-dimethylformamide (DMF) and acetone at a volume ratio of 4:1, add PVDF powder, and stir thoroughly at 60°C to prepare a PVDF spinning solution with a content of 15 wt%.

[0070] S2, same as step S4 in Example 1.

[0071] S3, same as step S5 in Example 1.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 3 is that F-MXene is not added to the spinning solution. Specifically, the steps include the following:

[0074] S1. Prepare a solvent by mixing N,N-dimethylformamide (DMF) and acetone at a volume ratio of 4:1, add PVDF powder, and stir thoroughly at 60°C to prepare a PVDF spinning solution with a content of 15 wt%.

[0075] S2. Add sodium dodecylbenzenesulfonate (SDBS) at 7 wt% of PVDF mass, and continue stirring for 2 hours.

[0076] S3, same as step S4 in Example 1.

[0077] S4, same as step S5 in Example 1.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 3 is that SDBS is not added to the spinning solution. Specifically, the following steps are included:

[0080] S1. Prepare a solvent by mixing N,N-dimethylformamide (DMF) and acetone at a volume ratio of 4:1. Add F-MXene to the mixed solvent and disperse it by ultrasonication. The amount of F-MXene added is 9 wt% of the mass of the PVDF added later.

[0081] S2. Add PVDF powder and stir thoroughly at 60°C to prepare a PVDF spinning solution with a content of 15 wt%.

[0082] S3, same as step S4 in Example 1.

[0083] S4, same as step S5 in Example 1.

[0084] Comparative Example 4

[0085] The difference between this comparative example and Example 3 is that F-MXene is replaced with an equal mass of unfluorinated modified MXene, while other steps and parameters remain unchanged.

[0086] Comparative Example 5

[0087] The difference between this comparative example and Example 3 is that SDBS is replaced with an equal mass of tetrabutylammonium chloride (TBAC), while other steps and parameters remain unchanged.

[0088] Test Example 1

[0089] The morphology of the nanofiber membranes prepared in Examples 1-4 and Comparative Examples 1-5 was observed and analyzed, and their air filtration performance was compared.

[0090] like Figure 1 As shown, the PVDF nanofiber membrane prepared in Comparative Example 1 does not have a multi-level fiber structure, and the pore size between fibers is about 2.5 μm. It has a good interception effect on PM2.5 particles, but the interception effect on finer particles (such as PM0.3) will be reduced.

[0091] Figure 2The image shows a SEM image of the nanofiber membrane prepared in Comparative Example 2. As can be seen from the image, due to the addition of SDBS, a nanoscale fiber network structure exists between the main fibers in the prepared nanofiber membrane. This is because the SDBS anions dispersed in the spinning solution significantly improve the conductivity of the spinning solution, increasing it from 61 μs / cm in the pure PVDF spinning solution of Comparative Example 1 to 321 μs / cm in Comparative Example 2. Figure 4 The high electrical conductivity increases the charge density on the jet surface, effectively promoting the formation of a regular, uniform two-dimensional nanomesh structure. This nanoscale mesh structure can significantly improve the interception efficiency of the fiber membrane for fine particulate matter, while avoiding the increase in resistance caused by increasing the filtration efficiency through increasing the thickness of the fiber membrane, thus achieving a good balance between high-efficiency filtration and low breathing resistance.

[0092] Figure 3 The image shows a SEM image of the nanofiber membrane prepared in Comparative Example 3. Although the addition of F-MXene also significantly improved the conductivity of the spinning solution (254 μs / cm), Figure 4 However, judging from the morphology images of the fiber membrane, no nano-network structure was formed. This is because F-MXene has a two-dimensional sheet structure, which mainly exists in the spinning solution as independent sheets or a few stacked layers, lacking the molecular-level dispersion ability and interfacial activity of anionic surfactants like SDBS. Specifically, SDBS, as a small-molecule anionic surfactant, can be uniformly distributed in the spinning solution system, forming a stable charge-rich layer on the jet surface through electrostatic stretching, thereby effectively inducing Coulomb splitting and refinement of the jet and promoting the formation of nanoscale fiber networks. Although F-MXene has high intrinsic conductivity and negative charge, its large sheet size and rigid structure limit its ability to form a uniform and continuous charge distribution on the jet surface, making it difficult to induce controllable branching and refinement behavior of the jet. In addition, the addition of F-MXene mainly changes the bulk conductivity of the spinning solution rather than enhancing the local charge density on the jet surface. Therefore, its inducing effect on fiber refinement is limited, and the final fiber membrane is still dominated by trunk fibers, lacking the typical structural characteristics of a multi-level nano-network. In summary, the formation of the nano-network structure mainly depends on the addition of SDBS, while the purpose of F-MXene doping is to improve the triboelectric output performance of the fiber membrane, which will be tested and verified later.

[0093] Figure 5 The images in a and b represent SEM images of the nanofiber membranes prepared in Examples 1-4, respectively. Figure 6Viscosity and conductivity curves of spinning solutions prepared with different concentrations of F-MXene in Comparative Example 2 and Examples 1-4 are shown. When SDBS and F-MXene are doped simultaneously, with a fixed SDBS doping concentration of 7 wt%, the amount of F-MXene added has no negative impact on the formation of the nanonetwork structure, further verifying the role of SDBS in the composite system and laying the foundation for constructing high-efficiency, low-resistance filter materials. Simultaneously, because F-MXene doping can further improve the overall conductivity of the spinning solution on top of SDBS doping, the resulting nanonetwork structure is richer and the fibers are finer.

[0094] The filtration performance of the nanofiber membranes prepared in Comparative Examples 1-3 and Example 3 was tested using PSL aerosols containing PM0.3 particles. The results are as follows: Figure 7 As shown in the figure, the filtration efficiency of the pure PVDF nanofiber membrane prepared in Comparative Example 1 is only 80.82%. However, after adding SDBS, the nanofiber membrane prepared in Comparative Example 2 achieves a filtration efficiency of 99.98% and a quality factor of 0.083 Pa due to the formation of a multi-level nanonetwork structure. -1 When only F-MXene is doped without the addition of SDBS, the filtration efficiency and quality factor of the fiber membrane prepared in Comparative Example 3 are similar to those of Comparative Example 1 because no nanonetwork structure is formed in the fiber membrane. However, when both SDBS and F-MXene are doped, the nanofiber membrane prepared in Example 3, due to the formation of a finer nanonetwork structure, maintains excellent filtration efficiency while slightly reducing piezoresistive resistance, thus resulting in a higher quality factor (0.088 Pa). -1 ), resulting in better overall filtration performance.

[0095] Figure 8 The image shown is a SEM image of the nanofiber membrane prepared in Example 3 after filtration. It can be seen that in particulate matter filtration, the finer nanonetwork structure plays a key role in intercepting fine particulate matter compared to the main fiber membrane, which is the key to its ability to effectively improve filtration performance.

[0096] Test Example 2

[0097] The triboelectric output performance of the nanofiber membranes prepared in Example 3 and Comparative Examples 1-5 was tested and compared. A copper mesh on the nanofiber membrane was used as an electrode and fixed to a substrate. A silver-modified nylon mesh was used as the contact friction layer. The test size was 6 cm × 6 cm, the contact distance was 4 mm, the contact pressure was 10 N, and the contact frequency was 2 Hz. The open-circuit voltage was recorded using a graphical sampling multimeter and a high-resistance / low-current electrometer.

[0098] Figure 9The images show photographs, SEM images, and corresponding silver elemental mapping of the silver-modified nylon mesh. It can be seen that the 300-mesh nylon mesh is semi-transparent. This porous structure ensures that particles can easily pass through to the nanofiber membrane layer in subsequent applications, while also providing some resistance under airflow, allowing for reciprocating motion and collision with the nanofiber membrane during respiration. Numerous fine particles appear on the surface of the modified nylon mesh, and the corresponding Ag elemental mapping shows that the surface silver nanoparticles are uniformly distributed on the nylon mesh surface.

[0099] The triboelectric output performance of the nanofiber membrane prepared in Example 3 and the nylon mesh before and after silver modification were compared and tested. The results are as follows: Figure 10 As shown in the figure, the modified nylon mesh can significantly increase the triboelectric output voltage, which is twice that of the unmodified nylon mesh.

[0100] The triboelectric output performance of the modified nylon mesh and the fiber membranes obtained in Comparative Examples 1-5 and Example 3 were compared and tested. The results are shown in [Figure Number]. Figure 11As shown in the figure, the output voltage of the pure PVDF nanofiber membrane prepared in Comparative Example 1 was only about 28V, while the addition of SDBS increased the output voltage of the nanofiber membrane to about 48V (Comparative Example 2). This is mainly attributed to the following mechanisms: First, as an anionic surfactant, SDBS significantly improves the conductivity of the spinning solution, promotes fiber splitting and refinement during electrospinning, and forms a nanoscale fiber network structure with a higher specific surface area, thereby increasing the effective contact sites inside the friction layer and enhancing the generation and transfer efficiency of triboelectric charge. Second, the sulfonate groups abundant in the SDBS molecule have strong electronegativity, which can enhance the charge capture and retention ability of the PVDF fiber surface, increase the surface charge density, and thus improve the overall triboelectric output performance. When doped with 9wt% F-MXene, the triboelectric output voltage of the fiber membrane increased significantly, reaching about 112V, which is 4 times that of the pure PVDF nanofiber membrane. This is because F-MXene, as a highly conductive two-dimensional material, forms a microcapacitor structure inside the fiber membrane, significantly enhancing its charge capture and storage capabilities. Simultaneously, its abundant fluorine-containing functional groups on its surface endow the fiber membrane with strong negative charge, increasing the triboelectric charge density. Since SDBS not only promotes the formation of the nanoscale fiber network structure but also improves triboelectric performance to some extent, the synergistic effect of both further enhances the triboelectric output performance. In Example 3, the nanofiber membrane prepared by co-doping 9 wt% F-MXene and 7 wt% SDBS achieved a triboelectric output voltage of 123 V, providing a reliable signal output basis and sensitivity guarantee for high-performance triboelectric signal sensing and monitoring. However, when 9 wt% MXene and 7 wt% SDBS were used as the doping medium, the nanofiber membrane prepared in Comparative Example 4 showed a slight decrease, which also demonstrates the role of fluorination modification of MXene in further promoting triboelectric output performance. In Comparative Example 5, TBAC was used instead of SDBS. When the branching promoter was a cationic agent, its positive charge weakened the overall negative charge of the membrane, which reduced the membrane's ability to capture and store electrons during contact friction. As a result, the output voltage decreased significantly. This indicates that when promoting the formation of multi-level structures in the fibrous membrane nanonetwork, it is necessary to rationally select charge-enhancing materials with negative charge, so as to synergistically improve the triboelectric output performance of the fibrous membrane while promoting the formation of multi-level structure nanofiber membranes.

[0101] The synergistic optimization effect of F-MXene and SDBS co-doping is not only to jointly improve the triboelectric output performance of the fiber membrane, but more importantly, it has a significant impact on the hydrophobic properties of the fiber membrane, thereby affecting the stability during the monitoring process. Figure 12The graph shows the water contact angles of the nanofiber membranes prepared in Comparative Examples 1-4 and Example 3. As can be seen from the graph, the pure PVDF nanofiber membrane in Comparative Example 1 exhibits inherent hydrophobic properties, with a contact angle of 132.2°. In Comparative Example 2, the addition of SDBS, due to the presence of a large number of hydrophilic anions, caused the contact angle to drop sharply to 21.7°, changing from hydrophobic to hydrophilic. While this imparts good filtration performance to the nanofiber membrane, the hydrophilicity is detrimental to the stable triboelectric output of the fiber membrane under high humidity conditions. In contrast, due to the grafting of long fluoroalkyl chains onto the surface of F-MXene, the nanofiber membrane prepared in Comparative Example 3 further improved its hydrophobicity on top of the original PVDF hydrophobic properties, achieving a water contact angle of 140.5°. When both are present in the sample of Example 3, the hydrophobic properties of F-MXene dominate, effectively offsetting the hydrophilic effect of SDBS, maintaining the fiber membrane in a stable hydrophobic state of 133.1°. Therefore, the co-incorporation of F-MXene not only effectively enhances the triboelectric output performance of the nanofiber membrane but also effectively overcomes the negative impact of SDBS on the membrane, maintaining its hydrophobic properties and helping to maintain surface charge transfer efficiency in humid environments, thus ensuring the stability of triboelectric performance. Simultaneously, SDBS not only promotes the formation of branched network structures and improves the filtration performance of the fiber membrane but also enhances the overall triboelectric output performance of the fiber membrane. Therefore, the synergistic effect of F-MXene and SDBS lays the foundation for the construction of high-performance filtration and monitoring masks.

[0102] Furthermore, when unmodified MXene is doped, the water contact angle of the nanofiber membrane prepared in Comparative Example 4 is 0°. The combined effect of hydrophilic SDBS and hydrophilic MXene results in extremely strong hydrophilicity in the fiber membrane, which is detrimental to respiratory filtration and intelligent monitoring. This demonstrates that fluorinated MXene not only slightly improves the triboelectric output performance but also provides crucial support for the hydrophobic stability of the fiber membrane.

[0103] Based on this, the triboelectric output performance of the nanofiber membranes prepared in Comparative Example 4 and Example 3 under different humidity environments was evaluated. Figure 13While the nanofiber membrane doped with SDBS and MXene in Comparative Example 4 exhibits good triboelectric output performance, its output voltage drops sharply with increasing humidity. At 50% humidity, the output voltage is around 108V; however, it drops to around 53V when humidity rises to only 60%, and further to 5.6V at 80% humidity, a decrease of 95%. This is because the surface of the fiber membrane is highly hydrophilic (water contact angle of 0°), easily adsorbing water molecules from the air in high humidity environments. This leads to the neutralization of triboelectric charges by water molecules or dissipation through the water film, weakening the charge capture and retention capabilities. In contrast, the nanofiber membrane prepared in Example 3, due to its excellent hydrophobicity (133.1°), can maintain an output voltage of 92V even in a 90% high humidity environment, demonstrating superior moisture resistance and environmental adaptability, providing a guarantee for long-term reliable sensing and monitoring under complex conditions.

[0104] Test Example 3

[0105] Using the nanofiber membrane prepared in Example 3, a multi-layer structure was assembled according to the construction method of a smart monitoring mask to evaluate its application in smart detection. Figure 14 The diagram shows the multi-layered structure of a smart mask. The inner layer is made of ordinary commercial spunbond nonwoven fabric to isolate moisture during exhalation and prevent it from affecting the electrodes. The outer layer of the spunbond nonwoven fabric is a copper mesh electrode, on which sits a multi-level nanofiber membrane obtained through in-situ deposition. The two are integrated to ensure the output of triboelectric signals. The outer layer of the nanofiber membrane is a nano-silver modified nylon mesh. When a person breathes, the nanofiber membrane adheres to the copper mesh and remains relatively stationary. During exhalation and inhalation, the modified nylon mesh collides and separates from the nanofiber membrane with the airflow, generating triboelectric induction charges on the copper mesh electrode. These charges are connected to the copper mesh electrode via wires, forming an open-circuit voltage and a short-circuit current in the external circuit to achieve signal detection.

[0106] Its monitoring principle is as follows Figure 15 As shown, during inhalation, airflow pressure drives the flexible modified nylon mesh to bend inward and make physical contact with the nanofiber membrane. The triboelectric effect causes equal amounts of opposite charges to accumulate on the surfaces of the two materials; the fiber membrane becomes negatively charged, and the nylon mesh becomes positively charged. Due to the electrostatic induction of the copper mesh electrodes, electrons flow from the external current to the electrodes. Subsequently, during exhalation, the reverse airflow gradually separates the two friction layers, disrupting the original electrostatic balance. The resulting induced potential drives electrons from the electrodes to the grounding terminal. Through this periodic "contact-separation" cycle, the mechanical energy of the respiration process can be effectively converted into electrical energy, thus enabling self-powered monitoring and real-time monitoring of the human respiratory physiological state and environmental information.

[0107] This smart mask was used to detect human respiration, such as Figure 16 As shown, this mask can accurately identify four typical breathing states: normal breathing, fast breathing, coughing, and apnea. Under normal breathing conditions, the mask outputs a stable periodic pulse signal with a voltage of approximately 2 V. When the subject experiences rapid breathing after exercise, the signal frequency increases significantly, and the voltage rises to approximately 6 V due to the increased airflow intensity. When simulating coughing, the instantaneous strong airflow impact causes violent contact and separation of the friction layer, generating a characteristic signal with sharp peaks, with peak voltages exceeding 12 V. In contrast, when the subject is in an apnea (breath-holding) state, there is no relative movement at the friction interface, and the output signal returns to the baseline level. These results clearly demonstrate that the monitor possesses high sensitivity and real-time feature recognition capabilities, showing potential in intelligent respiratory monitoring, sleep apnea syndrome early warning, and daily health management.

[0108] To evaluate the capabilities of the fiber membrane prepared in Example 3 in environmental monitoring and self-efficacy monitoring, a filtration device simulating a real-world polluted environment was constructed, such as... Figure 17 As shown, the device uses a transparent acrylic sheet as its outer shell (32 cm × 42 cm × 32 cm) to allow for real-time observation of the internal pollution levels. An air intake is located on the left side of the device to introduce PM2.5 particles generated by burning mosquito coils to create a simulated polluted environment. An exhaust fan is deployed in the core area of ​​the device, supported by four plastic brackets at its base to ensure airflow. The fiber membrane to be tested is fixed above the exhaust fan to achieve optimal filtration. Furthermore, an air quality monitor is placed at the front left of the device to monitor changes in pollutant concentrations in real time.

[0109] To further evaluate the ability of the nanofiber membrane prepared in Example 3 to identify environmental particulate matter while filtering it, 11 types of pollutant particles, including metals, metal oxides, and polymers, were selected. A dusty environment was created, and the particles were trapped on the surface of the nanofiber membrane. The response characteristics of different pollutants to the triboelectric output voltage were then tested. Figure 18As shown in the figure, the output performance is highly sensitive to the physicochemical properties of the attached material, and the voltage amplitude exhibits a gradient difference with the type of powder. Among them, the attachment of graphene, which has excellent conductivity, causes the output voltage to drop sharply to the lowest value (approximately 20 V), followed by copper (Cu) and iron (Fe) micropowders. Highly conductive powders such as Graphene, Cu, and Fe construct a micron-scale charge transport network on the surface of the tribological layer, acting as a "fast channel" for charge loss, causing the surface induced charge to leak out in a very short time, resulting in a significant decrease in voltage output. In contrast, powders with high electronegativity, such as PVDF, PTFE, PVA, and mosquito smoke dust particles, exhibit good compatibility, allowing the device to maintain a higher electrical output level (approximately 70-80 V). This dust coverage leads to the reconstruction of the effective triboelectric sequence, causing the system's energy conversion logic to evolve from a "fiber membrane-nylon mesh" pairing to a "powder-nylon mesh" composite triboelectric mode, with the output performance controlled by the electronegativity of the powder material itself. Natural polymers (chitosan, silk fibroin) and metal oxides (TiO2, ZnO) exhibit output voltages between the two. Insulating Chitosan and Silk fibroin powders readily capture positive charges during adsorption and friction. The reverse electric field generated by the polarized charges of these particles partially counteracts the frictional effect of the negatively charged nanofiber membrane, weakening its sensing capability. Simultaneously, inorganic particles such as TiO2 and ZnO form geometric barriers and physical isolation at the interface. This non-uniform microscopic coverage not only hinders close molecular-level contact between friction layers but also reduces the effective charge transfer area due to changes in contact force. In summary, these results not only verify the sensitivity of the fiber membrane's triboelectric properties to pollutants of different components but also provide a solid physical basis for its signal calibration and pattern recognition in dusty environments.

[0110] Taking mosquito coils as an example, the change in triboelectric output voltage of the filtered fiber membrane was tested under different PM2.5 environments at the same time (60s). Figure 19 As shown in figures a and b, the amount of particulate matter trapped on the fiber membrane surface varies at different PM2.5 concentrations. Higher concentrations result in greater surface trapping and a greater impact on the triboelectric output voltage. As illustrated, higher PM2.5 concentrations lead to faster voltage decay, and the magnitude of the coefficients in the linear fitting equation can be used to identify air pollution conditions.

[0111] Furthermore, since the amount of particulate matter on the fiber membrane is correlated with the triboelectric output voltage, the magnitude of the triboelectric output voltage can be used to monitor the amount of particles loaded on the fiber membrane. This allows for assessment of whether the mask's filtration efficiency has decreased to the point where replacement is necessary, encouraging timely replacement and preventing harm caused by reduced filtration performance. Similarly, using mosquito coils as a simulated pollutant, the PM2.5 concentration in the chamber before and after filtration is monitored to calculate the amount of particulate matter trapped per unit area on the fiber membrane surface. Then, the triboelectric output voltage of nanofiber membranes with different trapping capacities is tested. Figure 20 As shown, as the amount of particulate matter trapped on the membrane surface increases, the output voltage continuously decreases. Figure 20 (a, b) When the retention rate reaches 0.294 μg / cm³ 2 Afterwards, the output voltage no longer changes. This is because the fiber membrane surface is covered with too many particles. The friction mainly occurs between the nylon mesh and the particles. Therefore, even if the amount of particles increases, the frictional properties remain unchanged, indicating that the particles have completely covered the fiber membrane in this state, and the filter mask is severely contaminated. Figure 20 As shown in Figure d. To provide an alert regarding the loss of filtration efficiency in face masks, the filtration performance of nanofiber membranes with different particulate matter retention capacities was tested, as shown in Figure d. Figure 20 As shown in Figure c, the filtration efficiency continuously decreases with increasing particulate matter retention, while the pressure drop increases due to particulate matter clogging the pores, resulting in a continuous decline in the overall quality factor. When the retention rate is 0.072 μg / cm³... 2 At that time, its filtration efficiency had dropped from over 99% to 98.54%, and the pressure drop had begun to increase significantly, with a severe decrease in the quality factor. This indicates that it's time to consider replacing the mask. Furthermore, the SEM image shows (…). Figure 20 In state d), the particulate matter is not yet severe enough to accumulate in the fiber membrane, but continued accumulation will rapidly reduce its filtration efficiency. Based on this, we can construct a correlation between the triboelectric output voltage signal and mask replacement to provide intelligent reminders for mask or related filter material replacement, instead of the traditional time-based reminders (which cannot reflect the actual situation of the filter material, leading to premature replacement in environments with low air pollution, resulting in waste, or too late replacement in environments with high pollution, causing corresponding harm).

[0112] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing an air particulate matter filtration nanofiber membrane, characterized in that, Includes the following steps: A fiber branching agent, a triboelectric reinforcing material, and a fluorinated polymer are dispersed in a solvent to form a spinning solution. The spinning solution is then electrospun to obtain the air particulate matter filtration nanofiber membrane. The triboelectric enhancement material is fluorinated modified MXene and / or fluorinated modified graphene.

2. The method for preparing an air particulate matter filtering nanofiber membrane as described in claim 1, characterized in that, The fiber branching agent is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium stearate, and sodium laurate; The fluorinated polymer is selected from one or more of polytetrafluoroethylene, polytetrafluoroethylene-hexafluoropropylene, polytetrafluoroethylene-ethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polyvinylidene fluoride-tetrafluoroethylene.

3. The method for preparing an air particulate matter filtering nanofiber membrane as described in claim 1, characterized in that, The concentration of fluorinated polymer in the spinning solution is 14-17 wt%, the amount of fiber branching agent added is 3-9% of the mass of fluorinated polymer, and the amount of triboelectric reinforcing material added is 3-12% of the mass of fluorinated polymer.

4. The method for preparing an air particulate matter filtering nanofiber membrane as described in claim 1, characterized in that, The method for preparing the fluorinated modified MXene or fluorinated modified graphene is as follows: 1H,1H,2H,2H-perfluorodecyltriethoxysilane and MXene or graphene oxide are dispersed in ethanol and reacted to obtain fluorinated modified MXene or fluorinated modified graphene.

5. The method for preparing an air particulate matter filtering nanofiber membrane as described in claim 1, characterized in that, The conditions for electrospinning are as follows: spinning voltage is 15-18 kV, spinning solution flow rate is 0.4-0.8 mL / h, spinning distance is 13-17 cm, collecting drum speed is 100-400 r / min, and relative humidity is 10-30%.

6. An air particulate filter nanofiber membrane prepared by the preparation method according to any one of claims 1-5.

7. A face mask, characterized in that, The mask comprises a spunbond nonwoven fabric layer, a copper mesh electrode layer, a nanofiber membrane as described in claim 6, and a nylon mesh layer arranged in sequence.

8. The mask as described in claim 7, characterized in that, The nanofiber membrane is deposited in situ onto the copper mesh electrode layer via electrospinning. The copper mesh electrode layer has a mesh size of 100-300.

9. The mask as described in claim 7, characterized in that, The nylon mesh layer is 200-400 mesh, and nano-silver is deposited in situ on both sides.

10. The mask as described in claim 7, characterized in that, The mask connects the copper mesh electrode layer to an oscilloscope and an electrometer via wires or to a wireless module to output signals, enabling intelligent monitoring of human breathing status, real-time air pollution status, and real-time filtration efficiency.

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