Preparation method of polylactic acid-based nano-filtration fiber membrane with efficient natural photothermal conversion efficiency

Abstract

The invention discloses a preparation method of a polylactic acid-based nano-filtration fiber membrane with efficient natural photothermal conversion efficiency, and belongs to the field of membranes. The specific preparation process comprises the following steps: firstly, preparing molybdenum disulfide nano particles, and then coating the surfaces of the molybdenum disulfide nano particles with a polydopamine (PDA) layer to obtain nano particles with a core-shell structure so as to improve the dispersity of the nano particles in an electrostatic spinning solution and improve the compatibility and interfacial force with a polymer matrix; then modifying copper sulfide nanoparticles on the outer surface of the polydopamine to construct composite photo-thermal conversion particles with a core-shell-satellite structure; finally, polylactic acid is used as a base material, and the nano-filtration fiber membrane is obtained through an electrostatic spinning technology. By utilizing different absorption characteristics of CuS, PDA, MoS2 and polylactic acid to light with different energy, through the design of the multi-layer structure of the photo-thermal conversion particles, the multi-component efficient synergistic effect is fully exerted, the full absorption and utilization of wide-spectrum sunlight are realized, and the solar energy-thermal energy conversion efficiency is remarkably improved.

Description

Technical Field

[0001] This invention relates to a method for preparing a polylactic acid-based nanofiber filter membrane with high natural photothermal conversion efficiency, belonging to the field of functional filter fiber material technology. Background Technology

[0002] Typical natural photothermal conversion materials include copper sulfide (CuS), molybdenum disulfide (MoS2), MXene, zinc oxide (ZnO), rare earth elements, and graphene. In recent years, researchers have attempted to introduce different types of photothermal nanoparticles into polymer fibers to endow them with photothermal response characteristics, thereby developing multifunctional membrane materials that combine efficient filtration and photothermal sterilization functions. For example, patent CN202311316995 prepared a copper oxide / polyvinylidene fluoride photothermal membrane, and patent CN202110519228.1 prepared a MoS2 / PCL photothermal nanofiber membrane, both exhibiting good photothermal conversion performance. However, photothermal fiber membrane materials with a single photothermal functional filler component suffer from problems such as a narrow light absorption range, insufficient photothermal stability, and low photothermal conversion efficiency. Therefore, researchers have further improved the absorption and conversion rate of solar radiation across a wider spectrum by combining multiple photothermal fillers and leveraging their multi-component synergistic effect. For example, patent CN202110993266.0 describes a composite photothermal photocatalyst prepared by introducing three different types of photothermal conversion particles: graphene oxide, silver, and cerium oxide. This composite exhibits good solar photothermal conversion efficiency and photocatalytic performance. Patent CN202211392044.4 also discloses a method for preparing a BiOBr / Bi2S3 heterojunction photocatalyst, resulting in a heterojunction photocatalyst with full-spectrum response and photothermal effect, which can effectively utilize near-infrared light to achieve photothermal conversion. Since CuS has a broad natural light absorption spectrum and low synthesis cost, while MoS2 has advantages such as low excitation energy, large specific surface area, and high chemical stability, researchers have also prepared MoS2-modified CuS particles and loaded them onto the surface of g-C3N4 nanosheets using a solvent evaporation method, finding that this material possesses highly efficient photocatalytic capabilities.

[0003] In the preparation of polymer-based filter fiber membrane materials, on the one hand, the average diameter of electrospun fiber membranes is only 100-300 nm, which is close to the particle size of inorganic photothermal functional particles. When inorganic photothermal functional particles are directly added to the polymer matrix as fillers, the interfacial forces between them and the matrix are weak, which may lead to the destruction of the prepared nanofiber membrane structure or a reduction in porosity. In some cases, photothermal functional particles may even detach from the fibers, ultimately affecting the performance and safety of the fiber membrane. On the other hand, the polymer-based nanofiber filter membranes prepared by electrospinning are characterized by photothermal functional particles with high photothermal conversion capabilities being encapsulated in the polymer matrix or embedded within the polymer fibers. When natural light is incident and interacts with the photothermal functional particles, except for a few exposed on the surface of the polymer fibers, in most cases, the light needs to penetrate the polymer matrix to reach the photothermal functional particles and undergo the photothermal conversion reaction. Meanwhile, different types of photothermal nanoparticles have varying absorption and conversion capabilities for different wavelengths of light, and different wavelengths of light have varying transmittance to polymer matrix materials. Simply embedding inorganic photothermal functional particles into the polymer matrix leads to attenuation of incident light during propagation within the polymer matrix, resulting in low radiative energy utilization and hindering the improvement of photothermal conversion efficiency. Therefore, how to achieve efficient and stable photothermal synergistic effects through the design of composite structures with multiple photothermal components has become a key issue in the preparation of high-efficiency natural photothermal conversion nanofiber membranes.

[0004] This invention proposes a method for preparing MoS2@PDA / CuS composite photothermal nanoparticles with a core-shell-satellite structure and their polylactic acid-based nanofiber membrane. First, a PDA layer is coated onto the surface of MoS2 nanoparticles via in-situ oxidative polymerization. Next, CuS is grown in-situ on the MoS2@PDA surface using a hydrothermal method, constructing the core-shell-satellite structured MoS2@PDA / CuS ternary composite photothermal nanoparticles. Finally, a MoS2@PDA / CuS / PLA photothermal nanofiber membrane is prepared using solution electrospinning. Through this preparation method, the core-shell-satellite structured ternary composite photothermal nanoparticles can form a strong interfacial interaction with polylactic acid fibers, while simultaneously achieving uniform dispersion within the PLA fiber membrane. Ultimately, this ensures that the photothermal nanofiber membrane maintains high filtration efficiency (>98%) while significantly improving its natural photothermal response performance. This photothermal nanofiber membrane not only possesses efficient photothermal conversion and breathability, but also exhibits excellent filtration performance and environmentally friendly characteristics, making it widely applicable in the development of next-generation disposable green filtration and protective products. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing a polylactic acid-based nanofiber filter membrane with high natural photothermal conversion efficiency, comprising the following steps:

[0006] S1 Preparation of molybdenum disulfide nanoparticles

[0007] Thioacetamide and ammonium molybdate were added to NH4HCO3 solution and stirred for 30-60 min. The mixture was then heated at 180℃-200℃ for 12-18 h. After the reaction was completed, the mixture was cooled to room temperature, and the resulting product was washed, centrifuged, dried, and collected.

[0008] S2 Preparation of molybdenum disulfide / polydopamine nanoparticles

[0009] A molybdenum disulfide nanoparticle suspension was prepared by adding molybdenum disulfide nanoparticles to deionized water. A dopamine hydrochloride solution was prepared by dissolving dopamine hydrochloride in tris(hydroxymethyl)aminomethane buffer. The molybdenum disulfide nanoparticle suspension and the dopamine hydrochloride solution were ultrasonically treated in an ice bath for 30-120 min, and then stirred at room temperature for 4-12 h. After washing, centrifugation and drying, core-shell structured molybdenum disulfide / polydopamine nanoparticles were obtained.

[0010] S3 Preparation of Molybdenum Disulfide / Polydopamine / Copper Sulfide Nanoparticles

[0011] Molybdenum disulfide / polydopamine nanoparticles were dissolved in deionized water and ultrasonically dispersed for 30-60 min. Then, copper sulfide nanoparticles were added and stirred slowly for 2-5 h to allow them to adhere to the polydopamine surface. After washing, centrifugation, and drying, core-shell-satellite structured molybdenum disulfide / polydopamine / copper sulfide nanoparticles were obtained.

[0012] S4 Preparation of Molybdenum Disulfide / Polydopamine / Copper Sulfide / Polylactic Acid Nanofiber Membranes

[0013] Molybdenum disulfide / polydopamine / copper sulfide nanoparticles were added to a solvent and ultrasonically dispersed for 30-60 min. Polylactic acid was then added to the solvent, and the mixture was stirred at room temperature for 6-8 h to remove foam before use. Molybdenum disulfide / polydopamine / copper sulfide / polylactic acid nanofiber membranes were prepared by electrospinning.

[0014] The preparation method of polylactic acid-based nanofiber filter membrane with high natural photothermal conversion efficiency as described above, wherein each 3g-4g of thioacetamide corresponds to 2g-4g of ammonium molybdate and 50mL of NH4HCO3 solution, and the concentration of NH4HCO3 solution is 0.03-0.05mol / L.

[0015] The preparation method of polylactic acid-based nanofiber filter membrane with high natural photothermal conversion efficiency as described above, wherein the heating reaction in S1 is to transfer the solution into a polytetrafluoroethylene container and seal it in a stainless steel autoclave, and heat it at 180℃-200℃ for 12h-18h.

[0016] The preparation method of polylactic acid-based nanofiber membrane with high natural photothermal conversion efficiency as described above, wherein each 100mg-300mg molybdenum disulfide nanoparticle corresponds to 100ml deionized water, 20mg-400mg dopamine hydrochloride, and 100ml tris(hydroxymethyl)aminomethane buffer solution, the concentration of which is 8-10mM.

[0017] The method for preparing polylactic acid-based nanofiber filter membrane with high natural photothermal conversion efficiency as described above is characterized in that: the molybdenum disulfide / polydopamine nanoparticles prepared in S2 have a particle size of 20-150 nm and an outer dopamine layer thickness of 5-50 nm.

[0018] The method for preparing polylactic acid-based nanofiber membranes with high natural photothermal conversion efficiency as described above is characterized in that: in S3, every 3-5g of molybdenum disulfide / polydopamine nanoparticles corresponds to 3-5g of copper sulfide nanoparticles.

[0019] The preparation method of polylactic acid-based nanofiber filter membrane with high natural photothermal conversion efficiency as described above includes the following steps: washing in S1, S2, and S3 involves washing with ethanol and water 3-5 times respectively; vacuum drying involves vacuum drying overnight at 50-60°C.

[0020] The method for preparing a polylactic acid-based nanofiber filter membrane with high natural photothermal conversion efficiency as described above, wherein in step S4, each 0.0105g-0.105g of molybdenum disulfide / polydopamine / copper sulfide nanoparticle corresponds to 30g of solvent and 1.8-2.4g of polylactic acid. Preferably, the mass ratio of molybdenum disulfide / polydopamine / copper sulfide nanoparticles to polylactic acid is 0.5-5%.

[0021] The method for preparing polylactic acid-based nanofiber membranes with high natural photothermal conversion efficiency as described above, wherein the solvent in S4 is any one or a mixture of ethyl acetate, N,N-dimethylformamide, trifluoroethanol, and hexafluoroisopropanol.

[0022] The preparation method of polylactic acid-based nanofiber membrane with high natural photothermal conversion efficiency as described above, wherein the electrospinning voltage in S4 is 10-20kV.

[0023] In the preparation method of polylactic acid-based nanofiber membrane with high natural photothermal conversion efficiency as described above, the spinning distance of electrospinning in S4 is 150-200 mm.

[0024] The preparation method of polylactic acid-based nanofiber membrane with high natural photothermal conversion efficiency as described above, wherein the electrospinning speed in S4 is 1-2 mL / h.

[0025] The preparation method of polylactic acid-based nanofiber membrane with high natural photothermal conversion efficiency as described above, wherein the electrospinning time in S4 is 0.5-2h.

[0026] The method for preparing polylactic acid-based nanofiber membranes with high natural photothermal conversion efficiency as described above is characterized in that: the polylactic acid-based nanofiber membrane with high natural photothermal conversion efficiency prepared in S4 has a fiber diameter range of 80-300 nm.

[0027] Compared with the prior art, the present invention involves the following mechanisms and innovations:

[0028] Polylactic acid (PLA)-based nanofiber membranes, prepared by electrospinning, require natural light to penetrate the PLA matrix in most cases to undergo photothermal conversion with the photothermal functional particles. Since the spectrum of natural light includes the ultraviolet, visible, and near-infrared regions, different wavelengths of light have varying transmittance to the PLA matrix. Therefore, in the design of efficient photothermal conversion functional particle structures, simply considering the photothermal conversion capability of the particles themselves will result in low energy utilization of incident light radiation, hindering the improvement of the PLA photothermal fiber membrane's photothermal conversion efficiency. It is also necessary to fully consider the PLA's transmittance to different wavelengths of light and the absorption and conversion capabilities of different types of photothermal functional particles for different wavelength bands of light.

[0029] Based on the above principles, this invention innovatively utilizes the weak absorption region of polylactic acid in the 650-900 nm near-infrared "optical transparency window" to design and prepare MoS2@PDA / CuS composite photothermal nanoparticles with a core-shell-satellite structure. These nanoparticles have a core of MoS2 particles with relatively stronger absorption capacity for near-infrared light, a shell of PDA particles with relatively stronger absorption capacity for visible light, and CuS particles with relatively stronger visible light conversion capacity modified on the surface of PDA.

[0030] Compared to polylactic acid (PLA) photothermal fiber membranes that directly blend MoS2 and CuS or modify CuS particles with MoS2 (CuS@MoS2), the core-shell-satellite structure of MoS2@PDA / CuS composite photothermal nanoparticles not only achieves the synergistic effect of the three functional components, but also utilizes the weak absorption region of PLA's "optical transparency window" to minimize the absorption of full-spectrum incident light energy by the PLA matrix. On the other hand, through the core-shell-satellite structure design, MoS2, which has a stronger photothermal conversion capability for near-infrared light with high transmittance, is the inner layer, while CuS and PDA, which have stronger photothermal conversion capabilities for visible and ultraviolet light, are the outer layers. This fully leverages the different conversion capabilities and synergistic effects of different types of photothermal conversion functional particles for ultraviolet, visible, and near-infrared light, ultimately improving the overall photothermal conversion efficiency of the fiber membrane.

[0031] Furthermore, the prepared MoS2@PDA / CuS composite photothermal nanoparticles with a core-shell-satellite structure improve the dispersion and stability of photothermal functional particles in polylactic acid spinning solution due to the adhesiveness of PDA. This is beneficial for improving the dispersion of photothermal functional particles in electrospun fiber membranes. At the same time, PDA can also enhance the interfacial interaction between photothermal functional particles and polylactic acid matrix, thereby improving the overall performance and safety of fiber membranes.

[0032] The polylactic acid-based nanofiber membrane with high natural photothermal conversion efficiency prepared by this invention can be used in winter outdoor personal thermal management protective products such as warm masks and outdoor thermal protective clothing.

[0033] The beneficial effects of this invention are:

[0034] (1) This invention provides a polylactic acid-based nanofiber filter membrane with high natural photothermal conversion efficiency. By utilizing the selective absorption characteristics of different photothermal nanoparticles to specific wavelengths of light, a wide spectrum of solar light absorption is achieved through the synergistic effect of multiple components, which significantly improves the solar energy to thermal energy conversion efficiency.

[0035] (2) The present invention provides a polylactic acid-based nanofiber membrane with high natural photothermal conversion efficiency. The dense fiber structure is obtained by electrospinning technology, which enables the fiber membrane to have high filtration efficiency and also ensures good air permeability.

[0036] (3) The preparation method is simple to operate, green and safe, and the obtained nanofibers are biodegradable, which has good application prospects as a protective filter material. Detailed Implementation

[0037] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0038] Example 1

[0039] (1) Add 3g of thioacetamide and 2g of ammonium molybdate to 50mL of 0.03mol / L NH4HCO3 solution, stir for 30min, and then heat at 180℃ for 12h. After the reaction is complete, cool to room temperature, wash, centrifuge and dry the product and collect it.

[0040] (2) A molybdenum disulfide nanoparticle suspension was prepared by adding 100 mg of molybdenum disulfide nanoparticles to 100 ml of deionized water. A dopamine hydrochloride solution was prepared by dissolving 20 mg of dopamine hydrochloride in 100 ml of 0.8 mmol / L tris(hydroxymethyl)aminomethane buffer. The molybdenum disulfide nanoparticle suspension and the dopamine hydrochloride solution were ultrasonically treated in an ice bath for 30 min, and then stirred and reacted at room temperature for 8 h. After washing, centrifugation and drying, molybdenum disulfide / polydopamine nanoparticles were obtained.

[0041] (3) Dissolve 3g of molybdenum disulfide / polydopamine nanoparticles in 200ml of deionized water, sonicate for 30min, then add 3g of copper sulfide nanoparticles and stir slowly for 2h to allow them to adhere to the surface of polydopamine. After washing, centrifugation and drying, molybdenum disulfide / polydopamine / copper sulfide nanoparticles are obtained.

[0042] (4) 0.0105 g of molybdenum disulfide / polydopamine / copper sulfide nanoparticles were added to a mixed solvent of 30 g ethyl acetate and N,N-dimethylformamide (mass ratio 1:1) and ultrasonically dispersed for 30 min. Then, 1.8 g of polylactic acid was added to the solvent, and the mixture was stirred at room temperature for 6 h to remove foam before use. Molybdenum disulfide / polydopamine / copper sulfide / polylactic acid nanofiber membranes were prepared by electrospinning at a voltage of 10 kV, a spinning distance of 150 mm, a spinning speed of 1 mL / h, and a spinning time of 1 h.

[0043] Example 2

[0044] (1) Add 4g of thioacetamide and 4g of ammonium molybdate to 50mL of 0.05mol / L NH4HCO3 solution, stir for 60min, and then heat at 200℃ for 18h. After the reaction is complete, cool to room temperature, wash, centrifuge and dry the product and collect it.

[0045] (2) A molybdenum disulfide nanoparticle suspension was prepared by adding 300 mg of molybdenum disulfide nanoparticles to 100 ml of deionized water. A dopamine hydrochloride solution was prepared by dissolving 400 mg of dopamine hydrochloride in 100 ml of 10 mmol / L tris(hydroxymethyl)aminomethane buffer. The molybdenum disulfide nanoparticle suspension and the dopamine hydrochloride solution were ultrasonically treated in an ice bath for 60 min, and then stirred for 12 h at room temperature. After washing, centrifugation, and drying, molybdenum disulfide / polydopamine nanoparticles were obtained.

[0046] (3) Dissolve 5g of molybdenum disulfide / polydopamine nanoparticles in 200ml of deionized water, sonicate for 30min, then add 5g of copper sulfide nanoparticles and stir slowly for 5h to allow them to adhere to the surface of polydopamine. After washing, centrifugation and drying, molybdenum disulfide / polydopamine / copper sulfide nanoparticles are obtained.

[0047] (4) 0.021 g of molybdenum disulfide / polydopamine / copper sulfide nanoparticles were added to 30 g of trifluoroethanol solvent and ultrasonically dispersed for 60 min. Then, 2.4 g of polylactic acid was added to the solvent, and the mixture was stirred at room temperature for 8 h to remove foam before use. Molybdenum disulfide / polydopamine / copper sulfide / polylactic acid nanofiber membranes were prepared by electrospinning at a voltage of 20 kV, a spinning distance of 200 mm, a spinning speed of 2 mL / h, and a spinning time of 0.5 h.

[0048] Example 3

[0049] (1) Add 3.5 g of thioacetamide and 3.5 g of ammonium molybdate to 50 mL of 0.05 mol / L NH4HCO3 solution, stir for 60 min, and then heat at 200 °C for 12 h. After the reaction is complete, cool to room temperature, wash, centrifuge and dry the product and collect it.

[0050] (2) A molybdenum disulfide nanoparticle suspension was prepared by adding 300 mg of molybdenum disulfide nanoparticles to 100 ml of deionized water. A dopamine hydrochloride solution was prepared by dissolving 400 mg of dopamine hydrochloride in 100 ml of 10 mmol / L tris(hydroxymethyl)aminomethane buffer. The molybdenum disulfide nanoparticle suspension and the dopamine hydrochloride solution were ultrasonically treated in an ice bath for 30 min, and then stirred and reacted at room temperature for 12 h. After washing, centrifugation and drying, molybdenum disulfide / polydopamine nanoparticles were obtained.

[0051] (3) Dissolve 3g of molybdenum disulfide / polydopamine nanoparticles in 200ml of deionized water, sonicate for 60min, then add 5g of copper sulfide nanoparticles and stir slowly for 5h to allow them to adhere to the surface of polydopamine. After washing, centrifugation and drying, molybdenum disulfide / polydopamine / copper sulfide nanoparticles are obtained.

[0052] (4) 0.063 g of molybdenum disulfide / polydopamine / copper sulfide nanoparticles were added to 30 g of hexafluoroisopropanol solvent and ultrasonically dispersed for 60 min. Then, 2.1 g of polylactic acid was added to the solvent, and the mixture was stirred at room temperature for 6 h to remove foam before use. Molybdenum disulfide / polydopamine / copper sulfide / polylactic acid nanofiber membranes were prepared by electrospinning at a voltage of 15 kV, a spinning distance of 150 mm, a spinning speed of 1 mL / h, and a spinning time of 1.5 h.

[0053] Example 4

[0054] (1) Add 3.2 g of thioacetamide and 3 g of ammonium molybdate to 50 mL of 0.05 mol / L NH4HCO3 solution, stir for 60 min, and then heat at 200 °C for 15 h. After the reaction is complete, cool to room temperature, and collect the product by washing, centrifugation and drying.

[0055] (2) A molybdenum disulfide nanoparticle suspension was prepared by adding 300 mg of molybdenum disulfide nanoparticles to 100 ml of deionized water. A dopamine hydrochloride solution was prepared by dissolving 400 mg of dopamine hydrochloride in 100 ml of 10 mmol / L tris(hydroxymethyl)aminomethane buffer. The molybdenum disulfide nanoparticle suspension and the dopamine hydrochloride solution were ultrasonically treated in an ice bath for 30 min, and then stirred and reacted at room temperature for 12 h. After washing, centrifugation and drying, molybdenum disulfide / polydopamine nanoparticles were obtained.

[0056] (3) Dissolve 3g of molybdenum disulfide / polydopamine nanoparticles in 200ml of deionized water, sonicate for 60min, then add 3g of copper sulfide nanoparticles and stir slowly for 5h to allow them to adhere to the surface of polydopamine. After washing, centrifugation and drying, molybdenum disulfide / polydopamine / copper sulfide nanoparticles are obtained.

[0057] (4) 0.105 g of molybdenum disulfide / polydopamine / copper sulfide nanoparticles were added to a mixed solvent of 30 g ethyl acetate and N,N-dimethylformamide and ultrasonically dispersed for 30 min. Then, 2.1 g of polylactic acid was added to the solvent, and the mixture was stirred at room temperature for 6 h to remove foam before use. Molybdenum disulfide / polydopamine / copper sulfide / polylactic acid nanofiber membranes were prepared by electrospinning at a voltage of 15 kV, a spinning distance of 200 mm, a spinning speed of 1 mL / h, and a spinning time of 1 h.

[0058] Comparative Example 1

[0059] 2.1 g of polylactic acid was added to a mixed solvent of 30 g ethyl acetate and N,N-dimethylformamide, and sonicated for 30 min to ensure uniform dispersion. The mixture was then stirred at room temperature for 6 h to remove foam before use. Polylactic acid nanofiber membranes were prepared using an electrospinning machine with a spinning voltage of 15 kV, a spinning distance of 200 mm, a spinning speed of 2 mL / h, and a spinning time of 2 h.

[0060] Comparative Example 2

[0061] 0.105 g of molybdenum disulfide nanoparticles were added to a mixed solvent of 30 g ethyl acetate and N,N-dimethylformamide and sonicated for 30 min to achieve uniform dispersion. Next, 2.1 g of PLA was added to the solvent, and the mixture was stirred at room temperature for 6 h to remove foam before use. Copper disulfide / polylactic acid nanofiber membranes were prepared using an electrospinning machine at a voltage of 15 kV, a spinning distance of 200 mm, a spinning speed of 2 mL / h, and a spinning time of 1.5 h.

[0062] Comparative Example 3

[0063] 400 mg of dopamine hydrochloride was dissolved in 100 mL of a 10 mmol / L tris(hydroxymethyl)aminomethane buffer solution with a pH of 8.5. The solution was sonicated in an ice bath for 30 min, followed by stirring at room temperature for 12 h. The product was washed, centrifuged, and dried to obtain polydopamine nanoparticles.

[0064] Polydopamine nanoparticles with a mass fraction of 0.105 were added to a mixed solvent of ethyl acetate and N,N-dimethylformamide and sonicated for 30 min to achieve uniform dispersion. Then, 2.1 g of PLA was added to the suspension, and the mixture was stirred at room temperature for 24 h to remove foam before use. Polydopamine / polylactic acid nanofiber membranes were prepared using an electrospinning machine with a spinning voltage of 15 kV, a spinning distance of 200 mm, a spinning speed of 2 mL / h, and a spinning time of 1 h.

[0065] Comparative Example 4

[0066] 0.105 g of copper sulfide nanoparticles were added to a mixed solvent of 30 g ethyl acetate and N,N-dimethylformamide and sonicated for 30 min to achieve uniform dispersion. Next, 2.1 g of PLA was added to the solvent, and the mixture was stirred at room temperature for 6 h to remove foam before use. Copper sulfide / polylactic acid nanofiber membranes were prepared using an electrospinning machine at a voltage of 15 kV, a spinning distance of 200 mm, a spinning speed of 2 mL / h, and a spinning time of 1 h.

[0067] Comparative Example 5

[0068] 0.105 g of copper sulfide nanoparticles and molybdenum disulfide particles (mass ratio 1:1) were directly added to a mixed solvent of 30 g ethyl acetate and N,N-dimethylformamide, and sonicated for 30 min to achieve uniform dispersion. Next, 2.1 g of PLA was added to the solvent, and the mixture was stirred at room temperature for 6 h to remove foam before use. Copper sulfide / polylactic acid nanofiber membranes were prepared using an electrospinning machine with a spinning voltage of 15 kV, a spinning distance of 200 mm, a spinning speed of 2 mL / h, and a spinning time of 1 h.

[0069] Comparative Example 6

[0070] (1) A molybdenum disulfide nanoparticle suspension was prepared by adding 300 mg of molybdenum disulfide nanoparticles and copper sulfide nanoparticles (mass ratio 1:1) to 100 ml of deionized water. A dopamine hydrochloride solution was prepared by dissolving 400 mg of dopamine hydrochloride in 100 ml of 10 mmol / L tris(hydroxymethyl)aminomethane buffer. The above nanoparticle suspension and dopamine hydrochloride solution were ultrasonically treated in an ice bath for 30 min, and then stirred and reacted at room temperature for 12 h. After washing, centrifugation and drying, molybdenum disulfide / copper sulfide@polydopamine nanoparticles were obtained.

[0071] (4) 0.105 g of molybdenum disulfide / copper sulfide@polydopamine nanoparticles were added to a mixed solvent of 30 g ethyl acetate and N,N-dimethylformamide and ultrasonically dispersed for 30 min. Then, 2.1 g of polylactic acid was added to the solvent, and the mixture was stirred at room temperature for 6 h to remove foam before use. Molybdenum disulfide / polydopamine / copper sulfide / polylactic acid nanofiber membranes were prepared by electrospinning at a voltage of 15 kV, a spinning distance of 200 mm, a spinning speed of 1 mL / h, and a spinning time of 1 h.

[0072] The filtration performance of the polylactic acid-based nanofiber membrane with high natural photothermal conversion efficiency prepared in the above embodiments was tested against natural light irradiation temperature. The nanofiber membrane was laid flat at the test position of the instrument, and its filtration performance was characterized using an SC-FT-1702DYY type mask filtration performance tester. A 5% NaCl solution was prepared as the aerosol test medium, and the flow rate was set to 32 L / min to obtain the filtration efficiency and air permeability of the nanofiber membrane. The photothermal performance of the nanofiber membrane was tested using a xenon lamp to simulate natural light, with a simulated sunlight intensity and a light power density of 1 kW / m². 2 The surface temperature change of the nanofiber membrane was recorded in real time using an infrared camera. The test data are as follows:

[0073]

[0074] The data in the table show that when different proportions of MoS2@PDA / CuS composite photothermal nanoparticles with core-shell-satellite structures are added, the filtration efficiency of the polylactic acid-based nanofiber membrane remains above 98%, and its air resistance remains below 50 Pa, except for the sample with a spinning time of 2 hours. Due to the selective absorption of specific wavelengths of light by different photothermal nanoparticles in the molybdenum disulfide / polydopamine / copper sulfide nanoparticles, the polylactic acid-based photothermal nanofibers filled with MoS2@PDA / CuS composite photothermal nanoparticles exhibit broad-spectrum solar light absorption. After placing the fibers under a xenon lamp and irradiating them with simulated sunlight intensity for 6 minutes, the surface temperature of the nanofiber membranes all increased significantly. Compared with the comparative example, the photothermal efficiency of the polylactic acid-based nanofiber membrane with MoS2@PDA / CuS composite photothermal nanoparticles with core-shell-satellite structures is significantly higher than that of the comparative example with the same proportion of different types of photothermal nanoparticles.

[0075] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a polylactic acid-based nanofiber filter membrane with high natural photothermal conversion efficiency, characterized in that, Includes the following steps: S1 Preparation of molybdenum disulfide nanoparticles Thioacetamide and ammonium molybdate were added to NH4HCO3 solution and stirred for 30-60 min. The mixture was then heated at 180℃-200℃ for 12-18 h. After the reaction was completed, the mixture was cooled to room temperature, and the resulting product was washed, centrifuged, dried, and collected. S2 Preparation of molybdenum disulfide / polydopamine nanoparticles A molybdenum disulfide nanoparticle suspension was prepared by adding molybdenum disulfide nanoparticles to deionized water. A dopamine hydrochloride solution was prepared by dissolving dopamine hydrochloride in tris(hydroxymethyl)aminomethane buffer. The molybdenum disulfide nanoparticle suspension and the dopamine hydrochloride solution were ultrasonically treated in an ice bath for 30-120 min, and then stirred at room temperature for 4-12 h. After washing, centrifugation and drying, core-shell structured molybdenum disulfide / polydopamine nanoparticles were obtained. S3 Preparation of Molybdenum Disulfide / Polydopamine / Copper Sulfide Nanoparticles Molybdenum disulfide / polydopamine nanoparticles were dissolved in deionized water and ultrasonically dispersed for 30-60 min. Then, copper sulfide nanoparticles were added and stirred slowly for 2-5 h to allow them to adhere to the polydopamine surface. After washing, centrifugation, and drying, core-shell-satellite structured molybdenum disulfide / polydopamine / copper sulfide nanoparticles were obtained. S4 Preparation of Molybdenum Disulfide / Polydopamine / Copper Sulfide / Polylactic Acid Nanofiber Membranes Molybdenum disulfide / polydopamine / copper sulfide nanoparticles were added to a solvent and ultrasonically dispersed for 30-60 min. Polylactic acid was then added to the solvent, and the mixture was stirred at room temperature for 6-8 h to remove foam before use. Molybdenum disulfide / polydopamine / copper sulfide / polylactic acid nanofiber membranes were prepared by electrospinning.

2. The method according to claim 1, characterized in that, In S1, every 3g-4g of thioacetamide corresponds to 2g-4g of ammonium molybdate and 50mL of NH4HCO3 solution, with the concentration of NH4HCO3 solution being 0.03-0.05mol / L. The heating reaction involves transferring the solution to a polytetrafluoroethylene container and sealing it in a stainless steel autoclave, then heating the reaction at 180℃-200℃ for 12h-18h.

3. The method according to claim 1, characterized in that, In S2, each 100mg-300mg of molybdenum disulfide nanoparticles corresponds to 100ml of deionized water, 20mg-400mg of dopamine hydrochloride, and 100ml of tris(hydroxymethyl)aminomethane buffer solution with a concentration of 8-10mM.

4. The method according to claim 1, characterized in that, The molybdenum disulfide / polydopamine nanoparticles prepared in S2 have a particle size of 20-150 nm and an outer dopamine layer thickness of 5-50 nm.

5. The method according to claim 1, characterized in that, In S3, each 3-5g of molybdenum disulfide / polydopamine nanoparticles corresponds to 3-5g of copper sulfide nanoparticles; in S1, S2, and S3, washing is performed by washing with ethanol and water 3-5 times respectively; vacuum drying is performed overnight at 50-60℃.

6. The method according to claim 1, characterized in that, In S4, for every 0.0105g-0.105g of molybdenum disulfide / polydopamine / copper sulfide nanoparticles, there are 30g of solvent and 1.8-2.4g of polylactic acid; preferably, the mass ratio of molybdenum disulfide / polydopamine / copper sulfide nanoparticles to polylactic acid is 0.5-5%; the solvent is any one or a mixture of ethyl acetate, N,N-dimethylformamide, trifluoroethanol, and hexafluoroisopropanol.

7. The method according to claim 1, characterized in that, In S4, the electrospinning voltage is 10-20kV, the electrospinning distance is 150-200mm, the electrospinning speed is 1-2mL / h, and the electrospinning time is 0.5-2h.

8. The method according to claim 1, characterized in that, The polylactic acid-based nanofiber membranes with high natural photothermal conversion efficiency prepared in S4 have a fiber diameter range of 80-300 nm.

9. The nanofiber filter membrane prepared according to any one of claims 1-8.

10. The application of the nanofiber filter membrane prepared according to any one of claims 1-8, for use in winter outdoor personal thermal management protective products such as thermal masks and outdoor thermal protective clothing.

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