A flexible TiO 2 -based nanofiber membrane and its preparation method and application

Abstract

The present invention belongs to the technical field of nanofiber, and specifically relates to a flexible TiO2-based nanofiber membrane and its preparation method and application. The preparation method of the flexible TiO2-based nanofiber membrane of the present invention comprises the following steps: S1. Mix a surfactant, a metal salt, a titanium source and a solvent uniformly to obtain a spinning solution; S2. Perform electrospinning on the spinning solution, and apply pulsed high-voltage static electricity at the nozzle, and the spinning jet intermittently explodes into a net to obtain a hybrid fiber membrane composite of a two-dimensional nanonet and a nanofiber scaffold; S3. Perform gradient calcination on the hybrid fiber membrane to obtain the flexible TiO2-based nanofiber membrane. The present invention realizes the preparation of the flexible TiO2-based nanofiber membrane by using pulsed high-voltage electrospinning and gradient calcination technologies. The steps are simple and flexible, easy to operate, and realize the expansion of the nanofiber membrane from polymer materials to inorganic materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanofibers, and particularly relates to a flexible TiO 2 -based nanofiber membrane and its preparation method and application. Background Art

[0002] With the continuous development of the industrialization level, the problem of air pollution has become increasingly serious, posing a great threat to the ecological environment and human health. In order to reduce the harm of air pollution, air filtration materials are widely used in people's production and life. The importance of air filtration materials is particularly prominent. Currently, the commonly used air filtration materials are mainly micron or submicron fiber filtration materials, which have good filtration efficiency for PM 10 or PM 2.5 However, they generally have the deficiencies of relatively thick diameters and large pore sizes, so the filtration efficiency for particulate matter PM 0.3 with the most penetrating particle size is relatively low.

[0003] Some literature obtains nanofiber web materials by increasing the probability of electrostatic spraying, but this method has deficiencies such as large preparation randomness and poor adjustability of the fiber web structure; in addition, the above method is only applicable to the preparation of some specific polymer materials, and the prepared air filtration materials do not have the characteristics of sterilization and disinfection, and it is difficult to meet the actual application requirements.

[0004] In order to further obtain a nanofiber membrane with bactericidal activity, in the prior art, there is also a disclosure of first obtaining a nanofiber scaffold doped with nano-titanium dioxide by electrospinning, and then spraying antibacterial ultrafine fibers on the nanofiber scaffold to obtain the final antibacterial and antiviral air filtration material. However, the network structure formed by random stacking through spraying has problems such as low coverage rate, poor stability, and difficult regulation. There is also literature reporting the preparation of a halamine-modified nanofiber membrane by electrospinning and chlorine bleaching treatment. Although this material has good air filtration efficiency and antibacterial activity, it requires frequent chlorine bleaching treatment during use, and there are problems such as easy attenuation of antibacterial activity, poor stability, and cumbersome use process.

[0005] Therefore, it is necessary to provide an improved technical solution for the deficiencies of the above prior art. Summary of the Invention

[0006] The purpose of the present invention is to provide a flexible TiO 2 -based nanofiber membrane and its preparation method and application to solve or improve at least one of the problems of cumbersome preparation process, poor stability, low filtration efficiency, and poor antibacterial effect of the current filtration materials.

[0007] To achieve the above purpose, the present invention provides the following technical solution: A flexible TiO 2Preparation method of flexible TiO₂-based nanofiber membrane, comprising the following steps: S1. Mix a surfactant, a metal salt, a titanium source and a solvent evenly to obtain a spinning solution; S2. Perform electrospinning on the spinning solution and apply pulsed high-voltage static electricity at the nozzle, and the spinning jet intermittently explodes into a net to obtain a hybrid fiber membrane composed of a two-dimensional nanonet and a nanofiber scaffold; S3. Perform gradient calcination on the hybrid fiber membrane to obtain the flexible TiO₂ 2 -based nanofiber membrane.

[0008] Preferably, in step S2, the pulse waveform of the applied pulsed high-voltage static electricity is a spike wave, the instantaneous voltage of the pulse peak value is 50-80 kV, the voltage of the pulse valley value is 15-30 kV, and the pulse frequency is 0.5-50 Hz.

[0009] Preferably, in step S3, the gradient calcination includes a first-stage calcination and a second-stage calcination; the first-stage calcination is carried out in a nitrogen atmosphere, and the second-stage calcination is carried out in an air atmosphere; the temperature of the first-stage calcination is lower than that of the second-stage calcination, and the time of the first-stage calcination is longer than that of the second-stage calcination.

[0010] Preferably, the temperature of the first-stage calcination is 250-350 °C, and the calcination time is 120-240 min; the temperature of the second-stage calcination is 400-550 °C, and the calcination time is 30-60 min.

[0011] Preferably, in step S1, the titanium source is isopropyl titanate and / or tetrabutyl titanate; the metal salt is at least one of ferric chloride, cobalt chloride, copper chloride, zinc chloride, tungsten chloride, strontium chloride, bismuth nitrate, cerium nitrate, lanthanum nitrate and silver nitrate; the surfactant is polyacrylamide and / or polyoxypropylene polyoxyethylene copolymer; the solvent is at least one of water, ethanol, acetic acid and N,N-dimethylformamide.

[0012] Preferably, in the spinning solution, the concentration of the surfactant is 2 wt%-15 wt%; the concentration of the titanium source is 10 wt%-30 wt%; the molar ratio of the titanium source to the metal salt is 1:(0.01-0.1).

[0013] Preferably, in step S2, the perfusion speed during the electrospinning process is 1-5 mL / h, the receiving distance of the hybrid fiber membrane is 20-35 cm, the ambient temperature is 15-30 °C, and the ambient humidity is 10%-40%.

[0014] The present invention also provides a flexible TiO₂ 2 -based nanofiber membrane, which adopts the following technical solution: A flexible TiO₂ 2 -based nanofiber membrane, the flexible TiO₂ 2The nanofiber web membrane was prepared by the method described above.

[0015] Preferably, the flexible TiO 2 The nanofiber mesh membrane is composed of a nanofiber support and a two-dimensional nanonet; the fiber diameter of the two-dimensional nanonet is 10-50nm, and the mesh aperture is 30-400nm; the coverage of the two-dimensional nanonet is 60%-90%; the fiber diameter of the nanofiber support is 200-800nm; the flexible TiO 2 The porosity of the nanofiber web membrane is 70%-95%, the softness is 20-60mN, and the tensile strength is 1-5MPa.

[0016] The present invention also provides a flexible TiO 2 The application of the nanofiber web membrane adopts the following technical solution: the flexible TiO 2 Application of nanofiber web membrane in sterilization and / or filtration.

[0017] Beneficial effects:

[0018] 1. The present invention uses pulse high-voltage electrospinning and gradient calcination technology to achieve flexible TiO 2 The preparation of the nanofiber mesh membrane is simple, flexible and easy to operate. Compared with the existing technology, this method has the advantages of high two-dimensional nano-mesh coverage, good structural stability and strong controllability, and realizes the expansion of the nanofiber mesh membrane from polymer materials to inorganic materials.

[0019] 2. Flexible TiO prepared by the present invention 2 The nanofiber mesh membrane is composed of a pure inorganic nanofiber scaffold and a two-dimensional nanonet. It not only has the fine two-dimensional mesh structure unique to the nanofiber mesh membrane, but also has inorganic TiO 2 Excellent photocatalytic activity gives the material excellent air filtration performance and bactericidal and disinfecting activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them:

[0021] Figure 1 The flexible TiO 2 Nanofiber web membrane; wherein Figure 1 (a) is an optical photograph, Figure 1 (b) is the SEM image;

[0022] Figure 2 This is the SEM image of the product prepared in Comparative Example 1;

[0023] Figure 3 SEM image of the product prepared in Comparative Example 2. Detailed implementation manners

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0025] The present invention will be described in detail below in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0026] In view of at least one of the problems of cumbersome preparation process, poor stability, low filtration efficiency and poor antibacterial effect existing in current filter materials, the present invention provides a preparation method of a flexible TiO 2 -based nanofiber membrane. The preparation method of the flexible TiO 2 -based nanofiber membrane in the embodiment of the present invention includes the following steps: S1. Mix a surfactant, a metal salt, a titanium source and a solvent evenly to obtain a spinning solution; S2. Perform electrospinning on the spinning solution, and apply pulsed high-voltage static electricity at the nozzle, and the spinning jet intermittently explodes into a network to obtain a hybrid fiber membrane composed of a two-dimensional nanonet and a nanofiber scaffold; S3. Perform gradient calcination on the hybrid fiber membrane to obtain the flexible TiO 2 -based nanofiber membrane.

[0027] The present invention first precisely controls the process of the charged droplets exploding into a network by applying pulsed high-voltage static electricity at the electrospinning nozzle to produce a hybrid fiber membrane composed of a two-dimensional nanonet / nanofiber scaffold, and then performs gradient calcination to obtain a flexible TiO 2 -based nanofiber membrane. This method is simple and controllable, flexible in operation, with a stable two-dimensional network structure and high coverage rate. The product has good flexibility, bactericidal activity and high-efficiency air filtration performance.

[0028] The present invention uses pulsed high-voltage electrospinning and gradient calcination technologies to prepare a flexible TiO 2 -based nanofiber membrane. The principle is as follows: First, mix a surfactant, a dopant (metal salt), a titanium source and a solvent evenly to prepare a stable spinning solution. The purpose of adding a surfactant (preferably a polymer surfactant) is: on the one hand, to increase the solution viscosity to improve spinnability, and on the other hand, to reduce the solution surface tension to promote the formation of droplets at the subsequent electrospinning nozzle; the added metal salt (as a dopant) is used to increase the conductivity of the spinning solution to further enhance the formation of droplets at the electrospinning nozzle. In addition, it also serves as a doping modifier to improve the photocatalytic bactericidal activity of TiO 2 .

[0029] Subsequently, the above-mentioned hybrid chemical fiber web is placed in a tubular furnace and first calcined at a low temperature under a nitrogen atmosphere, allowing the polymer components in the hybrid chemical fiber web to gradually undergo carbonization. On the one hand, it can avoid the damage to the fiber web structure caused by the excessive decomposition of the polymer during the calcination process. On the other hand, it can inhibit the nucleation and crystallization of TiO 2 in the fiber web, reduce the grain size, and improve the flexibility of the fiber web material. Finally, the temperature is further increased and short-time calcination is carried out under an air atmosphere to remove the organic components, and finally a flexible TiO 2 -based nanofiber web is obtained.

[0030] In a preferred embodiment of the present invention, in step S2, the pulse waveform of the applied pulsed high-voltage electrostatic is a spike wave, the instantaneous voltage of the pulse peak is 50 - 80 kV (for example, 50 kV, 55 kV, 60 kV, 65 kV, 70 kV, 75 kV or 80 kV), the valley voltage of the pulse is 15 - 30 kV (for example, 15 kV, 18 kV, 21 kV, 24 kV, 26 kV, 28 kV or 30 kV), and the pulse frequency is 0.5 - 50 Hz (for example, 0.5 Hz, 1 Hz, 5 Hz, 10 Hz, 20 Hz, 30 Hz, 40 Hz or 50 Hz). Pulsed high-voltage electrospinning is carried out on the prepared spinning solution. The pulsed high-voltage electrostatic has a spike waveform characteristic, that is, the voltage will instantaneously jump from low voltage to high voltage and then immediately return to low voltage every once in a while. When the voltage is low, the spinning jet is mainly at the nozzle, and a nanofiber scaffold is obtained; and when the voltage jumps to high voltage instantaneously, at this time, due to the sharp increase in the electric field force, the jet instantaneously overcomes the surface tension and separates into countless charged small droplets, and further undergoes spreading, splitting and phase separation under the action of the high-voltage electric field force during the flight process, and finally a two-dimensional nano-network is formed and deposited on the nanofiber scaffold.

[0031] In a preferred embodiment of the present invention, in step S3, the gradient calcination includes a first-stage calcination and a second-stage calcination; the first-stage calcination is carried out under a nitrogen atmosphere, and the second-stage calcination is carried out under an air atmosphere; the temperature of the first-stage calcination is lower than that of the second-stage calcination, and the time of the first-stage calcination is longer than that of the second-stage calcination. By first carrying out low-temperature calcination on the hybrid chemical fiber web under a nitrogen atmosphere, allowing the polymer components (surfactants) in the hybrid chemical fiber web to gradually undergo carbonization, on the one hand, it can avoid the damage to the structure of the fiber web caused by the excessive decomposition of the polymer during the calcination process. On the other hand, it can inhibit the nucleation and crystallization of TiO 2 in the fiber web, reduce the grain size, and improve the flexibility of the fiber web material. Finally, the temperature is further increased and short-time calcination is carried out under an air atmosphere to remove the organic components, and finally a flexible TiO 2 -based nanofiber web is obtained.

[0032] In a preferred embodiment of the present invention, the temperature of the first-stage calcination is 250 - 350 °C (for example, 250 °C, 270 °C, 290 °C, 310 °C, 330 °C, 340 °C or 350 °C), and the calcination time is 120 - 240 min (for example, 120 min, 140 min, 160 min, 180 min, 200 min, 220 min or 240 min); the temperature of the second-stage calcination is 400 - 550 °C (for example, 400 °C, 430 °C, 460 °C, 490 °C, 520 °C or 550 °C), and the calcination time is 30 - 60 min (30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min). Among them, the temperature of the first-stage calcination cannot be too low, otherwise it is difficult for the hetero-fiber web to carbonize; nor can the temperature be too high, otherwise the polymer components will decompose too quickly during the calcination process, damaging the fiber web structure. The temperature and time of the second-stage calcination cannot be too high, otherwise the grain size will be too large, resulting in poor flexibility and brittleness of the fiber web.

[0033] In a preferred embodiment of the present invention, in step S1, the titanium source is isopropyl titanate and / or tetrabutyl titanate; the metal salt is at least one of ferric chloride, cobalt chloride, copper chloride, zinc chloride, tungsten chloride, strontium chloride, bismuth nitrate, cerium nitrate, lanthanum nitrate and silver nitrate; the surfactant is polyacrylamide and / or polyoxypropylene polyoxyethylene copolymer; the solvent is at least one of water, ethanol, acetic acid and N,N-dimethylformamide.

[0034] In a preferred embodiment of the present invention, in the spinning solution, the concentration of the surfactant is 2 wt% - 15 wt% (for example, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt% or 15 wt%); the concentration of the titanium source is 10 wt% - 30 wt% (10 wt%, 15 wt%, 20 wt%, 25 wt% or 30 wt%); the molar ratio of the titanium source to the metal salt is 1:(0.01 - 0.1) (for example, 1:0.01, 1:0.03, 1:0.05, 1:0.07, 1:0.09 or 1:0.1).

[0035] In a preferred embodiment of the present invention, in step S2, the perfusion speed during the electrospinning process is 1 - 5 mL / h (for example, 1 mL / h, 2 mL / h, 3 mL / h, 4 mL / h or 5 mL / h), the receiving distance of the hetero-fiber web is 20 - 35 cm (for example, 20 cm, 23 cm, 26 cm, 29 cm, 32 cm or 35 cm), the ambient temperature is 15 - 30 °C (for example, 15 °C, 18 °C, 20 °C, 22 °C, 24 °C, 26 °C, 28 °C or 30 °C), and the ambient humidity is 10% - 40% (for example, 10%, 15%, 20%, 25%, 30%, 35% or 40%).

[0036] The present invention also provides a flexible TiO 2 -based nanofiber web, and the flexible TiO 2 -based nanofiber web of the embodiment of the present invention is prepared by the method described above.

[0037] In a preferred embodiment of the flexible TiO 2 -based nanofiber web of the present invention, the flexible TiO 2 -based nanofiber web is composed of a nanofiber scaffold and a two-dimensional nanonetwork; the fiber diameter of the two-dimensional nanonetwork is 10-50 nm (for example, 10 nm, 20 nm, 30 nm, 40 nm or 50 nm), and the pore size of the mesh is 30-400 nm (for example, 30 nm, 60 nm, 100 nm, 200 nm, 300 nm or 400 nm); the coverage rate of the two-dimensional nanonetwork (i.e., the planar proportion of the two-dimensional nanonetwork in the flexible TiO 2 -based nanofiber web) is 60%-90% (for example, 60%, 65%, 70%, 75%, 80%, 85% or 90%); the fiber diameter of the nanofiber scaffold is 200-800 nm (for example, 200 nm, 240 nm, 310 nm, 370 nm, 450 nm, 520 nm, 580 nm, 630 nm, 690 nm, 720 nm, 760 nm or 800 nm); the porosity of the flexible TiO 2 -based nanofiber web is 70%-95% (for example, 70%, 75%, 80%, 85%, 90% or 95%), the softness is 20-60 mN (for example, 20 mN, 25 mN, 30 mN, 35 mN, 40 mN, 45 mN, 50 mN, 55 mN or 60 mN), and the tensile strength is 1-5 MPa (for example, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa or 5 MPa).

[0038] The two-dimensional network structure of the flexible TiO 2 -based nanofiber web of the present invention is stable and has a high coverage rate, and the product has good flexibility, bactericidal activity and high-efficiency air filtration performance.

[0039] The present invention also provides an application of the flexible TiO 2 -based nanofiber web, and the application of the flexible TiO 2 -based nanofiber web as described above in sterilization and / or filtration.

[0040] The following specifically describes the flexible TiO 2 -based nanofiber web of the present invention, its preparation method and application through specific embodiments.

[0041] The raw materials used in the following examples are all commercially available and mainly sourced from Aladdin Reagents.

[0042] Example 1

[0043] The preparation method of the flexible TiO 2 -based nanofiber web in this example includes the following steps:

[0044] S1. Mix polyoxypropylene polyoxyethylene copolymer, zinc chloride, titanium isopropoxide, ethanol and acetic acid evenly to obtain a spinning solution, where the concentration of polyoxypropylene polyoxyethylene copolymer is 5 wt%, the concentration of titanium isopropoxide is 20 wt%, the molar ratio of titanium isopropoxide to cobalt chloride is 1:0.03, and the volume ratio of ethanol to acetic acid is 1:1;

[0045] S2. Perform electrospinning on the spinning solution and apply pulsed high-voltage static electricity at the nozzle (the pulse waveform is a spike wave, the instantaneous voltage of the pulse peak is 65 kV, the valley voltage of the pulse is 20 kV, and the pulse frequency is 40 Hz). The spinning jet intermittently explodes into a web to obtain a hybrid fiber web composed of a two-dimensional nanonet and a nanofiber scaffold; among them, the perfusion speed during the electrospinning process is 3 mL / h, the receiving distance of the hybrid fiber web is 28 cm, the ambient temperature is 25 °C, and the ambient humidity is 25%.

[0046] S3. Perform gradient calcination on the hybrid fiber web to obtain the flexible TiO 2 -based nanofiber web of this example; among them, the gradient calcination consists of a first-stage calcination and a second-stage calcination. The first-stage calcination is carried out in a nitrogen atmosphere, the temperature of the first-stage calcination is 280 °C, and the calcination time is 180 min; the second-stage calcination is carried out in an air atmosphere, the temperature of the second-stage calcination is 500 °C, and the calcination time is 45 min.

[0047] Example 2

[0048] The preparation method of the flexible TiO 2 -based nanofiber web in this example includes the following steps:

[0049] S1. Mix polyacrylamide, tungsten chloride, tetrabutyl titanate, water and acetic acid evenly to obtain a spinning solution, where the concentration of polyacrylamide is 2 wt%, the concentration of tetrabutyl titanate is 10 wt%, the molar ratio of tetrabutyl titanate to tungsten chloride is 1:0.1, and the volume ratio of water to acetic acid is 2:1;

[0050] S2. Electrospin the spinning solution and apply pulsed high-voltage static electricity at the nozzle (the pulse waveform is a spike wave, the instantaneous voltage of the pulse peak is 50 kV, the voltage of the pulse valley is 15 kV, and the pulse frequency is 0.5 Hz). The spinning jet intermittently explodes into a net, obtaining a hybrid fiber web composite of a two-dimensional nanonet and a nanofiber scaffold. Among them, the perfusion speed during the electrospinning process is 1 mL / h, the receiving distance of the hybrid fiber web is 20 cm, the ambient temperature is 15 °C, and the ambient humidity is 10%.

[0051] S3. Gradiently calcine the hybrid fiber web to obtain the flexible TiO 2 -based nanofiber web of this example. Among them, the gradient calcination consists of a first-stage calcination and a second-stage calcination. The first-stage calcination is carried out in a nitrogen atmosphere, the temperature of the first-stage calcination is 250 °C, and the calcination time is 240 min. The second-stage calcination is carried out in an air atmosphere, the temperature of the second-stage calcination is 400 °C, and the calcination time is 60 min.

[0052] Example 3

[0053] The preparation method of the flexible TiO 2 -based nanofiber web of this example includes the following steps:

[0054] S1. Mix polyoxypropylene polyoxyethylene copolymer, silver nitrate, tetrabutyl titanate, ethanol, and acetic acid evenly to obtain a spinning solution, where the concentration of polyoxypropylene polyoxyethylene copolymer is 15 wt%, the concentration of isopropyl titanate is 30 wt%, the molar ratio of tetrabutyl titanate to silver nitrate is 1:0.01, and the volume ratio of ethanol to acetic acid is 1:2.

[0055] S2. Electrospin the spinning solution and apply pulsed high-voltage static electricity at the nozzle (the pulse waveform is a spike wave, the instantaneous voltage of the pulse peak is 80 kV, the voltage of the pulse valley is 30 kV, and the pulse frequency is 50 Hz). The spinning jet intermittently explodes into a net, obtaining a hybrid fiber web composite of a two-dimensional nanonet and a nanofiber scaffold. Among them, the perfusion speed during the electrospinning process is 5 mL / h, the receiving distance of the hybrid fiber web is 35 cm, the ambient temperature is 30 °C, and the ambient humidity is 40%.

[0056] S3. Gradiently calcine the hybrid fiber web to obtain the flexible TiO 2 -based nanofiber web of this example. Among them, the gradient calcination consists of a first-stage calcination and a second-stage calcination. The first-stage calcination is carried out in a nitrogen atmosphere, the temperature of the first-stage calcination is 350 °C, and the calcination time is 120 min. The second-stage calcination is carried out in an air atmosphere, the temperature of the second-stage calcination is 550 °C, and the calcination time is 30 min.

[0057] Comparative Example 1

[0058] The difference between this comparative example and Example 1 is only that in the spinning process, pulsed high-voltage static electricity is not used, but constant high-voltage static electricity of 20 kV is directly used for spinning, and the rest are the same as those in Example 1.

[0059] The SEM image of the product prepared in this comparative example is as Figure 2 shown.

[0060] It can be Figure 2 seen that: compared with Example 1, in the sample finally obtained in Comparative Example 1, there are only nanofibers and no two-dimensional nanonet. This is mainly because the applied high-voltage static electricity is a constant voltage, and the electric field force is relatively constant and will not increase sharply, so the spinning jet is difficult to overcome the surface tension and break into a net.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is only that in the calcination process, gradient calcination is not used, but it is directly calcined at 500 °C in an air atmosphere for 45 min, and the rest are the same as those in Example 1.

[0063] The SEM image of the product prepared in this comparative example is as Figure 3 shown.

[0064] It can be Figure 3 seen that: compared with Example 1, the TiO 2 -based nanofiber network membrane obtained in Comparative Example 2 has problems of large brittleness, poor flexibility and low strength. This is mainly because the lack of low-temperature calcination in an inert atmosphere in the first stage leads to too fast thermal decomposition of the polymer components in the hybrid fiber network, causing certain damage to the fiber membrane structure; in addition, direct high-temperature calcination easily leads to too fast crystallization growth and larger grain size of TiO 2 in the fiber network membrane, thus reducing the flexibility of the nanofiber network membrane.

[0065] Experimental Example

[0066] 1. Test the fiber scaffold, pore size of the mesh holes, coverage rate of the two-dimensional nanonet, porosity, softness and tensile strength of the flexible TiO 2 -based nanofiber network membrane of the example and the products of the comparative examples 2 Test method: The fiber scaffold and pore size of the mesh holes of the two-dimensional nanonet are mainly obtained through statistical analysis of the FE-SEM photos of the samples; the coverage rate of the two-dimensional nanonet is mainly obtained by analyzing some FE-SEM photos of the samples by the "grid method"; the flexible TiO

[0067] -based nanofiber network membrane of the example and the products of the comparative examples 2The porosity of the flexible TiO₂-based nanofiber membrane was mainly measured by a pore size analyzer, the softness was measured by a paper softness analyzer (using the ASTM D2923-95 test standard), and the tensile strength was measured by a tensile tester (using the ISO 1789:2008 standard).

[0068] 2. Filtration and sterilization performance tests

[0069] Test method:

[0070] Flexible TiO₂ 2 The filtration performance of the flexible TiO₂-based nanofiber membrane was tested by an automatic filter material tester: A sodium chloride aqueous solution with a concentration of 2 wt% was prepared as the generating solution for 0.3 μm aerosol, and the air flow rate was set to 32 L / min -1 , and the effective test area was 100 cm² 2 ;

[0071] Flexible TiO₂ 2 The sterilization performance test of the flexible TiO₂-based nanofiber membrane: A 2×2 cm² nanofiber membrane was immersed in 10 mL of an E. coli bacterial solution with a concentration of 3×10⁶ CFU / mL, and then a 300 W xenon lamp was used as the visible light source for a 60-min photocatalytic sterilization experiment. The number of bacterial colonies was counted by the counting method to calculate the sterilization efficiency. 2 7

[0072] The experimental results are shown in Table 1 below:

[0073] Table 1

[0074]

[0075] In summary: The present invention successfully realized the preparation of the flexible TiO₂-based nanofiber membrane by using pulsed high-voltage electrospinning and gradient calcination technologies. This method has simple steps and flexible operation. The prepared material not only has structural characteristics such as a high two-dimensional nano-network coverage rate, small mesh pore size, and large nanofiber membrane porosity, but also has excellent tensile strength and flexibility. It shows high filtration efficiency and low pressure resistance in air filtration applications, and at the same time exhibits excellent photocatalytic sterilization activity. 2

[0076] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.​​​

Claims

1. A preparation method of a flexible TiO 2 -based nanofiber web It is characterized in that it includes the following steps: S1. Mix a surfactant, a metal salt, a titanium source and a solvent uniformly to obtain a spinning solution; S2. Perform electrospinning on the spinning solution, and apply pulsed high-voltage static electricity at the nozzle. The spinning jet intermittently explodes into a net to obtain a hybrid fiber web composite of a two-dimensional nanonet and a nanofiber scaffold; S3. Gradiently calcine the mixed chemical fiber web to obtain the flexible TiO 2 -based nanofiber web; In step S2, the pulse waveform of the applied pulsed high-voltage static electricity is a spike wave, the instantaneous voltage of the pulse peak value is 50 - 80 kV, the voltage of the pulse valley value is 15 - 30 kV, and the pulse frequency is 0.5 - 50 Hz; In step S3, the gradient calcination includes a first-stage calcination and a second-stage calcination; the first-stage calcination is carried out in a nitrogen atmosphere, and the second-stage calcination is carried out in an air atmosphere; the temperature of the first-stage calcination is lower than that of the second-stage calcination, and the time of the first-stage calcination is longer than that of the second-stage calcination.

2. The preparation method of the flexible TiO 2 -based nanofiber web according to claim 1, It is characterized in that the temperature of the first-stage calcination is 250 - 350 °C, and the calcination time is 120 - 240 min; the temperature of the second-stage calcination is 400 - 550 °C, and the calcination time is 30 - 60 min.

3. The preparation method of the flexible TiO 2 -based nanofiber web according to claim 1, It is characterized in that in step S1, the titanium source is isopropyl titanate and / or tetrabutyl titanate; the metal salt is at least one of ferric chloride, cobalt chloride, copper chloride, zinc chloride, tungsten chloride, strontium chloride, bismuth nitrate, cerium nitrate, lanthanum nitrate and silver nitrate; the surfactant is polyacrylamide and / or polyoxypropylene polyoxyethylene copolymer; the solvent is at least one of water, ethanol, acetic acid and N,N-dimethylformamide.

4. The preparation method of the flexible TiO 2 -based nanofiber web according to claim 1, It is characterized in that in the spinning solution, the concentration of the surfactant is 2 wt% - 15 wt%; the concentration of the titanium source is 10 wt% - 30 wt%; the molar ratio of the titanium source to the metal salt is 1:(0.01 - 0.1).

5. The preparation method of the flexible TiO 2 -based nanofiber web according to claim 1, It is characterized in that in step S2, the perfusion speed during the electrospinning process is 1 - 5 mL / h, the receiving distance of the hybrid fiber web is 20 - 35 cm, the ambient temperature is 15 - 30 °C, and the ambient humidity is 10% - 40%.

6. A flexible TiO 2 -based nanofiber web It is characterized in that The flexible TiO 2 -based nanofiber web is prepared by the method described in any one of claims 1-5.

7. The flexible TiO 2 -based nanofiber web according to claim 6, It is characterized in that The flexible TiO 2 -based nanofiber network membrane is composed of a nanofiber scaffold and a two-dimensional nanonet; the fiber diameter of the two-dimensional nanonet is 10 - 50 nm, the pore diameter of the mesh holes is 30 - 400 nm; the coverage rate of the two-dimensional nanonet is 60% - 90%; the fiber diameter of the nanofiber scaffold is 200 - 800 nm; The porosity of the flexible TiO 2 -based nanofiber web is 70%-95%, the softness is 20-60 mN, and the tensile strength is 1-5 MPa.

8. Use of the flexible TiO 2 -based nanofiber web in sterilization and / or filtration.

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