Janus cotton fabric with radiation refrigeration and antibacterial functions and preparation method thereof

Abstract

The invention discloses a Janus cotton fabric with radiation refrigeration and antibacterial functions and a preparation method thereof.The preparation method creatively achieves multifunctional integration through multistage structural design and interface engineering and specifically comprises the steps that 1, a bionic silicon dioxide nano sheath layer grows on the surface of cotton fiber in situ through a controllable sol-gel method; the monodispersity of the nanoparticles is ensured by optimizing the ratio of the TEOS to the silane coupling agent; (2) introducing high-refractive-index nanoparticles to construct a dual-scale photonic crystal structure, and enhancing solar spectrum reflection by using a plasma resonance effect; (3) performing hydrophilic interface modification by adopting a biomacromolecule self-assembly technology to form a super-hydrophilic antibacterial layer; and (4) constructing a super-hydrophobic interface on the single side of the fabric through precise spraying, and finally forming a Janus structure with an asymmetric wetting gradient. The preparation process is mild in condition and high in controllability, and the obtained Janus fabric has excellent antibacterial performance (the antibacterial rate gt; 99.5%) and radiation refrigeration performance (daytime sub-environment temperature drop gt; 8 DEG C).

Description

Technical Field

[0001] The present invention relates to the technical field of functional textile materials, and specifically to a Janus cotton fabric based on bionic micro-nanostructure regulation. The Janus cotton fabric has the functions of high-efficiency antibacterial, solar spectrum regulation and mid-infrared radiation cooling, and can be widely used in intelligent temperature-regulating clothing, medical protective materials and special functional textiles. Background Art

[0002] In hot environments, the human body maintains thermal balance primarily through heat radiation and sweat evaporation [Joule, 2020, 4, 724−742.]. However, when humidity is too high or sweat cannot evaporate quickly, sweat accumulates on the skin surface, causing discomfort and potentially leading to illness. Furthermore, a moist skin environment creates an ideal breeding ground for bacteria, which not only produces odor but can also cause skin infections and other health issues [Progress in Materials Science, 2023, 139, 101−172.]. Therefore, developing multifunctional fabrics that can effectively channel sweat, provide cooling, and act as antibacterial agents is crucial for improving human comfort and health in hot environments.

[0003] Radiative cooling technology uses outer space as a cooling source, relying on an 8-13 µm "atmospheric window" channel to dissipate heat from terrestrial objects into outer space in the form of electromagnetic waves. This technology is energy-neutral, low-cost, environmentally friendly, and sustainable [Nature Photonics, 2022, 16, 182-190]. Janus structural materials, due to their asymmetric functional design, offer unique advantages in the field of smart textiles. Existing research (e.g., related patents such as CN 119121629A) has shown that directional sweat management can be achieved by constructing a hydrophilic / hydrophobic double-sided structure. However, such designs often focus on controlling liquid transport and fail to synergize with radiative cooling performance. In particular, achieving antibacterial properties while maintaining high solar reflectivity and high to medium infrared emissivity remains a challenge for existing technologies.

[0004] Inspired by natural organisms (such as the Janus structure of the desert beetle's carapace), this paper proposes a method for preparing a superfabric that combines inorganic and organic components to achieve both efficient radiative cooling and moisture-absorbing antibacterial properties. This method utilizes a sol-gel method to in-situ grow high-emissivity inorganic silica microspheres on cotton fabric. This modified fabric is then loaded with high-refractive-index nanoparticles using a silane coupling agent. The resulting fabric is then modified with a hydrophilic and hydrophobic coating to create a Janus cotton fabric with both radiative cooling and antibacterial properties. Summary of the Invention

[0005] The purpose of the present invention is to provide a simple and efficient method for preparing radiative cooling and antibacterial superfabrics based on in situ synthesis and coating modification. The prepared superfabric effectively combines breathability, softness, antibacterial and durability, bringing new possibilities for the rational design and sustainable development of the next generation of smart textiles.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is: A method for preparing Janus cotton fabric with radiant cooling and antibacterial functions comprises the following steps: Step 1: Pretreatment of cotton fabric: Soak the raw cotton fabric in acetone, ethanol, and deionized water sequentially and ultrasonicate for 10-30 minutes to expose the cellulose hydroxyl active sites. Then, dry the fabric in an oven at 40-60°C to a constant weight to obtain the pretreated cotton fabric.

[0007] Step 2: In situ Growth of Biomimetic Silica Nanosheaths: Catalyst I solution was diluted with deionized water to form Solution A. The pretreated cotton fabric was immersed in Solution A and interface activation was performed under constant temperature magnetic stirring (200-800 rpm, 25 ± 5°C). Tetraethyl orthosilicate (TEOS) was used as a silicon source and thoroughly mixed with a silane coupling agent in anhydrous ethanol to prepare Solution B (silicon source precursor). Solution B was added dropwise to the Solution A-fabric system at a microfluidic injection rate of 0.1-3 mL / min, allowing the epitaxial growth of SiO2 nanoclusters along the cotton fiber axis. The fabric was stirred at room temperature for 10-30 minutes at a controlled stirring rate of 200-800 rpm. After stirring, the mixed solution was allowed to stand for 1 to 24 hours, and the cotton fabric with in-situ silica growth was taken out. The reaction product was washed with deionized water several times to remove unreacted tetraethyl orthosilicate and silane coupling agent, and then placed in an oven at 40 to 60°C to dry to constant weight to prepare Cotton@SiO2 fabric.

[0008] The catalyst I is selected from at least one of the following: dilute hydrochloric acid, citric acid, and ammonia water, and the amount used is 5% to 40% of the mass of deionized water.

[0009] Step 3: Plasmon Resonance Modification of High-Refractive-Index Nanoparticles: The high-refractive-index nanoparticles were ultrasonically dispersed in an ethanol-water solution (ethanol / water volume ratio of 1:1) to obtain a high-refractive-index nanoparticle dispersion. The ultrasonic power was set at 30 W to 750 W, and the ultrasonication time was set at 0.5 to 90 min. The cotton@SiO2 fabric was placed in the dispersion at room temperature and mechanically stirred to completely immerse the fabric in the dispersion. The stirring speed was controlled between 100 rpm and 800 rpm. A silane coupling agent and catalyst II were added to chemically bond the nanoparticles to the interstices of the SiO2 network, forming a dual-scale photonic crystal structure. The reaction was allowed to proceed for 1 to 6 hours to ensure complete reaction. After completion, the product was washed with deionized water several times to remove unreacted nanoparticles and silane coupling agent, and then dried in an oven at 40-60°C to constant weight, thereby preparing the dual-nanoparticle-loaded fabric.

[0010] The catalyst II is selected from at least one of the following: dilute hydrochloric acid, citric acid, and aqueous ammonia, and the amount used is 1% to 20% of the mass of the aqueous ethanol solution.

[0011] Step 4: Hydrophilic interface modification: Using biomacromolecule self-assembly technology, immerse the double-nanoparticle-loaded fabric prepared in step 3 in a hydrophilic modification solution for 1 to 10 minutes, take out the fabric, wipe off the excess liquid on the surface of the fabric, and place it in a 40 to 80°C oven to dry to constant weight to prepare a hydrophilic double-nanoparticle-loaded fabric.

[0012] The hydrophilic substance in the hydrophilic modification solution is selected from one or more of the following combinations: alkyl glycoside, polyvinyl alcohol, sodium alginate, sodium carboxymethyl cellulose, and chitosan, and the amount of the hydrophilic substance is 0.05% to 5% of the mass of the deionized water.

[0013] Step 5, hydrophobic interface modification: Use a spray gun to spray the hydrophobic agent onto the hydrophilic double-nanoparticle-loaded fabric prepared in step 4. The hydrophobic layer and the hydrophilic layer form an asymmetric Janus wetting gradient, which can directionally conduct moisture and inhibit biofilm formation, ultimately obtaining a Janus cotton fabric with radiant cooling and antibacterial functions.

[0014] In step 1 of the present invention, the conditions for the ultrasonic treatment are preferably: ultrasonic treatment at a power of 50 W to 600 W for 10 min to 60 min, to lay the interface foundation for the subsequent in-situ growth of the nanostructure.

[0015] In step 1 of the present invention, considering the reflectivity and transmittance of the original cotton fabric itself, 60s or 80s pure cotton fabric is preferred, and the size depends on the use requirements.

[0016] In step 2 of the present invention, in order to fully protonate the hydroxyl groups on the cellulose surface (-OH → -OH2 +), the activation time is preferably 10~30 min.

[0017] In step 2 of the present invention, considering the SiO2 particle size distribution (preferably a distribution range of 500 nm to 2000 nm) obtained by in situ sol-gel conversion and its dispersibility on the surface of the textile fiber, the amount of tetraethyl orthosilicate used is 10% to 30% of the mass of ethanol used, and the silane coupling agent is at least one selected from the following: KH550, KH560, and KH570, and the amount used is 1% to 10% of the mass of ethanol used.

[0018] In step 3 of the present invention, the high refractive index nanoparticles are purchased directly from the market. Considering the scattering effect and dispersion stability of the nanoparticle surface, the average size is controlled to be 100 nm to 2000 nm, and the nanoparticles are selected from at least one of the following: nano-alumina, nano-titanium dioxide, nano-barium sulfate, nano-hexagonal boron nitride, nano-zirconium oxide, nano-magnesium oxide, nano-zinc oxide, and kaolin.

[0019] In step 3 of the present invention, considering the dispersibility and modification efficiency of the high refractive index nanoparticles in the solvent, the mass amount of the nanoparticles is 1% to 10% of the mass amount of the ethanol aqueous solution, and the silane coupling agent is at least one selected from the following: KH550, KH560, and KH570, and the amount used is 1% to 10% of the mass amount of the ethanol aqueous solution.

[0020] In step 5 of the present invention, the hydrophobic agent can be obtained by an existing method, (1) preparing a PMPS / SiO2 cross-linked network hydrophobic agent by a polymerization reaction initiated by ultraviolet light. Chem. Eng. J., 2023, 455, 139894]; (2) Directly purchase commercial hydrophobic agents (such as Dow Corning® DC-5200).

[0021] In step 5 of the present invention, in order to ensure that the hydrophobic modification of the fabric is limited to a single side area and the hydrophobic effect of the coating is significant, a high-precision air spray gun is used to spray the fabric on one side 2 to 3 times (with an interval of 1 min) under the conditions of a nozzle diameter of 0.3-0.5 mm, an atomization pressure of 0.15-0.25 MPa, and a spraying distance of 15-25 cm.

[0022] This invention innovatively achieves multifunctional integration through multi-level structural design and interface engineering. Specifically, it includes: (1) in situ growth of a biomimetic silica nanosheath on the cotton fiber surface via a controlled sol-gel method, optimizing the ratio of TEOS and silane coupling agent to ensure the monodispersity of the nanoparticles; (2) introducing high-refractive-index nanoparticles to construct a dual-scale photonic crystal structure, utilizing the plasma resonance effect to enhance solar spectrum reflectance; (3) using biomacromolecule self-assembly technology to modify the hydrophilic interface and form a superhydrophilic antibacterial layer; and (4) constructing a superhydrophobic interface on one side of the fabric through precise spraying, ultimately forming a Janus structure with an asymmetric wetting gradient. This preparation process is mild and highly controllable, and the resulting Janus fabric has both excellent antibacterial properties (inhibition rate >99.5%) and radiant cooling performance (daytime subambient temperature drop >8°C).

[0023] After in-depth research, the inventors discovered that the ratio of tetraethyl orthosilicate to silane coupling agent significantly influences the colloidal stability and nanostructure morphology of the sol-gel system when preparing silica-modified cotton fabric. When the TEOS mass fraction increases above 30%, localized supersaturation during the hydrolysis and polycondensation reaction leads to the formation of polydisperse SiO2 secondary aggregates, causing system instability. After drying, micron-sized particles shed from the fabric surface (SEM-EDS confirmed the shed materials to be amorphous SiO2). Furthermore, the study found that increasing the amount of silane coupling agent significantly improved the dispersion of silica particles on the fiber surface. Therefore, the appropriate amounts of tetraethyl orthosilicate and silane coupling agent should be determined based on the actual silica dispersion and mechanical property requirements.

[0024] The antibacterial effect of super fabrics is achieved through the synergistic effect of inorganic and organic materials. The titanium dioxide and zinc oxide in the high-refractive-index nanoparticles and the inorganic and organic components such as alkyl glycoside and chitosan in the hydrophilic modifiers all have antibacterial effects. The type and dosage of nanoparticles and organic antibacterial agents will affect the antibacterial effect and solar emissivity of the modified super fabrics. Therefore, it is necessary to determine the appropriate type and dosage of raw materials.

[0025] Compared with the prior art, the excellent effects of the present invention are mainly reflected in: (1) the size and distribution of silica can be effectively controlled by adjusting the preparation process parameters of the precursor solution; (2) the inorganic-organic composite antibacterial system exhibits a significant synergistic effect, providing a basis for precise control based on the quantitative relationship between antibacterial efficiency and loading amount; (3) through the effective combination of high-emissivity silica and high-refractive index inorganic particles, the material is endowed with excellent radiative cooling performance, which has solved the compatibility problem between antibacterial function and radiative cooling performance in a breakthrough way; (4) the directional transport effect of the Janus structure avoids the accumulation of sweat and promotes the evaporation and heat dissipation of water. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Scanning electron microscopy imaging of radiatively cooled metatextile fibers.

[0027] Figure 2 Element distribution map on the surface of radiative cooling metafabric fiber. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto: Example 1: A raw cotton fabric (4 × 4 cm) was sequentially immersed in acetone, ethanol, and deionized water, ultrasonically treated for 10 minutes, and then dried in an oven at 60°C to constant weight. The cotton fabric was then immersed in 20% ammonia solution (15 mL) at 200 rpm. 4 mL of tetraethyl orthosilicate and 1 mL of KH560 were thoroughly mixed in 20 mL of anhydrous ethanol. The mixture was then added to the A-fabric solution at a rate of 3 mL / min and stirred at room temperature for 10 minutes at 200 rpm. After stirring, the mixture was allowed to stand for 6 hours. The cotton fabric with in situ silica growth was removed and washed and dried. 3 g of 500 nm titanium dioxide was dispersed in 50 mL of ethanol / water (ethanol / water volume ratio 1:1) and ultrasonically treated at 300 W for 20 minutes. The silica-modified fabric was placed in the dispersion at room temperature at 200 rpm. 1 mL of silane coupling agent and 2 mL of ammonia solution were added. The mixture reacted for 3 hours and then washed and dried to prepare the dual-nanoparticle-loaded fabric.

[0029] Weigh 0.2 g of alkyl glycoside and 0.8 g of polyvinyl alcohol and dissolve them in 19 g of deionized water to prepare a hydrophilic modification solution. Immerse the prepared double-nanoparticle loaded fabric in the hydrophilic modification solution for 5 minutes, take out the fabric, wipe off the excess liquid on the surface of the fabric, and put it into an 80°C oven to dry to prepare a hydrophilic double-nanoparticle loaded fabric. Use a spray gun to spray the hydrophobic agent DowCorning® DC-5200 on one side of the hydrophilic double-nanoparticle loaded fabric. The nozzle diameter is 0.3 mm, the atomization pressure is 0.25 MPa, the spraying distance is 25 cm, and the fabric is sprayed on one side twice (with an interval of 1 minute). The fabric finally prepared is as shown in FIG. Figure 1 and Figure 2 As shown, Figure 1 Scanning electron microscope imaging of radiation-cooled metafabric fibers. Figure 2 Element distribution map on the surface of radiative cooling metafabric fiber.

[0030] The reflectivity of the sample in the solar band was measured using an ultraviolet-visible-near-infrared spectrophotometer. The integrating sphere accessory is provided with the spectrophotometer. The weighted reflectivity of the metafabric in the solar spectrum band was measured to be 91.72%. The emissivity of the metafabric in the mid-infrared band was measured using a Fourier transform infrared spectrometer equipped with an integrating sphere. The weighted emissivity of the material was measured to be 96.61%.

[0031] Escherichia coli (ATCC 25922, E. coli ), Staphylococcus aureus (MCCCB 26003, S. aureus ), Escherichia coli and Staphylococcus aureus were cultured in liquid LB medium at 37 o The culture was shaken at 200 rpm for 12 h in a constant temperature shaker at C, and the bacterial solution was finally diluted to a concentration of 1×10 7 CFU mL –1 The superfabric sample to be tested was immersed in bacterial culture solution and cultured at 37°C for 24 hours, and then the sample was taken out. The sample surface was gently rinsed with ultrapure water to wash off the bacteria that were not firmly attached. Then, the sample was placed in 20 mL PBS buffer and ultrasonicated for 5 minutes to elute the bacteria on the sample surface into PBS buffer to obtain an eluate containing bacteria. The eluate was diluted step by step to form a gradient of 10 -2 , 10 -3 , 10 -4 25 μL of each gradient bacterial solution was spread on a solid culture medium and incubated at 37°C for 24 hours. Using raw cotton fabric as a blank control, the superfabric demonstrated excellent antibacterial efficacy against Escherichia coli and Staphylococcus aureus at 99.5% and 99.6%, respectively, according to GB / T 20944.3-2008.

[0032] Comparative Example 1: A raw cotton fabric (4 × 4 cm) was sequentially immersed in acetone, ethanol, and deionized water, ultrasonically treated for 10 minutes, and then dried in a 60°C oven to constant weight. The cotton fabric was then immersed in 15 mL of 30% ammonia solution at 200 rpm. 6 mL of tetraethyl orthosilicate and 1.5 mL of KH560 were thoroughly mixed in 20 mL of anhydrous ethanol and added to the A-fabric solution at a rate of 3 mL / min. The mixture was stirred at room temperature for 10 minutes at 200 rpm. After stirring, the mixture was allowed to stand for 6 hours. The cotton fabric with in situ silica growth was removed, washed, and dried. 5 g of 500 nm titanium dioxide was dispersed in 50 mL of ethanol / water (ethanol / water volume ratio 1:1) and ultrasonically treated at 300 W for 20 minutes. The silica-modified fabric was placed in the dispersion at room temperature, the rotation speed was controlled at 200 rpm, 2 mL of silane coupling agent and 3 mL of ammonia solution were added, and the mixture was reacted for 3 h and then washed and dried to prepare the double-nanoparticle-loaded fabric.

[0033] 0.2 g of chitosan and 0.8 g of polyvinyl alcohol were dissolved in 19 g of deionized water to prepare a hydrophilic modification solution. The resulting dual-nanoparticle-loaded fabric was immersed in the hydrophilic modification solution for 5 minutes. The fabric was removed, excess liquid on the surface was wiped off, and the fabric was dried in an 80°C oven to prepare the hydrophilic dual-nanoparticle-loaded fabric. The hydrophobic agent DowCorning® DC-5200 was sprayed onto one side of the hydrophilic dual-nanoparticle-loaded fabric using a spray gun. The spray gun was used with a nozzle diameter of 0.3 mm, an atomization pressure of 0.25 MPa, and a spray distance of 25 cm. Two coats of the fabric were applied to each side, with a 1-minute interval between coats.

[0034] The reflectivity of the sample in the solar band was measured using an ultraviolet-visible-near-infrared spectrophotometer. The integrating sphere accessory is provided with the spectrophotometer. The weighted reflectivity of the metafabric in the solar spectrum band was measured to be 90.25%. The emissivity of the metafabric in the mid-infrared band was measured using a Fourier transform infrared spectrometer equipped with an integrating sphere. The weighted emissivity of the material was measured to be 96.78%.

[0035] Using the same bacterial culture method and testing method as Example 1, the antibacterial rates of the super fabric against Escherichia coli and Staphylococcus aureus were 99.2% and 99.5%, respectively, showing excellent antibacterial effects.

[0036] Comparative Example 2: A raw cotton fabric (4 × 4 cm) was sequentially immersed in acetone, ethanol, and deionized water, ultrasonically treated for 10 minutes, and then dried in a 60°C oven to constant weight. The cotton fabric was then immersed in 10% ammonia solution (15 mL) at 200 rpm. 2 mL of tetraethyl orthosilicate and 0.5 mL of KH560 were thoroughly mixed in 20 mL of anhydrous ethanol. The mixture was then added to the A-fabric solution at a rate of 3 mL / min and stirred at room temperature for 10 minutes at 200 rpm. After stirring, the mixture was allowed to stand for 6 hours. The cotton fabric with in situ silica growth was removed, washed, and dried. 2 g of 500 nm titanium dioxide was dispersed in 50 mL of ethanol / water (ethanol / water volume ratio 1:1) and ultrasonically treated at 300 W for 20 minutes. The silica-modified fabric was placed in the dispersion at room temperature, the rotation speed was controlled at 200 rpm, 0.5 mL of silane coupling agent and 3 mL of ammonia solution were added, and the mixture was reacted for 3 h, then washed and dried to prepare the double-nanoparticle-loaded fabric.

[0037] A hydrophilic modification solution was prepared by dissolving 0.2 g of alkyl glycoside and 0.8 g of polyvinyl alcohol in 19 g of deionized water. The resulting dual-nanoparticle-loaded fabric was immersed in the solution for 5 minutes. The fabric was removed, excess liquid on the surface was wiped off, and the fabric was dried in an 80°C oven to obtain the hydrophilic dual-nanoparticle-loaded fabric. The hydrophobic agent DowCorning® DC-5200 was sprayed onto one side of the hydrophilic dual-nanoparticle-loaded fabric using a spray gun. The spray gun was used with a nozzle diameter of 0.3 mm, an atomization pressure of 0.25 MPa, and a spray distance of 25 cm. Two coats of the fabric were applied with a 1-minute interval between coats.

[0038] The reflectivity of the sample in the solar band was measured using an ultraviolet-visible-near-infrared spectrophotometer. The integrating sphere accessory is provided with the spectrophotometer. The weighted reflectivity of the metafabric in the solar spectrum band was measured to be 82.39%. The emissivity of the metafabric in the mid-infrared band was measured using a Fourier transform infrared spectrometer equipped with an integrating sphere. The weighted emissivity of the material was measured to be 92.62%.

[0039] Using the same bacterial culture method and testing method as Example 1, the antibacterial rates of the super fabric against Escherichia coli and Staphylococcus aureus were 97.4% and 95.5%, respectively, showing excellent antibacterial effects.

[0040] Example 2: A raw cotton fabric (4 × 4 cm) was sequentially immersed in acetone, ethanol, and deionized water, ultrasonically treated for 10 minutes, and then dried in an oven at 60°C to constant weight. The cotton fabric was then immersed in 20% ammonia solution (15 mL) at 200 rpm. 4 mL of tetraethyl orthosilicate and 1 mL of KH560 were thoroughly mixed in 20 mL of anhydrous ethanol. The mixture was then added to the A-fabric solution at a rate of 3 mL / min and stirred at room temperature for 10 minutes at 200 rpm. After stirring, the mixture was allowed to stand for 6 hours. The cotton fabric with in situ silica growth was removed and washed and dried. 3 g of 500 nm alumina was dispersed in 50 mL of ethanol / water (ethanol / water volume ratio 1:1) and ultrasonically treated at 300 W for 20 minutes. The silica-modified fabric was placed in the dispersion at room temperature at 200 rpm. 1 mL of silane coupling agent and 2 mL of ammonia solution were added. The mixture reacted for 3 hours and then washed and dried to prepare the dual-nanoparticle-loaded fabric.

[0041] A hydrophilic modification solution was prepared by dissolving 0.2 g of alkyl glycoside and 0.8 g of polyvinyl alcohol in 19 g of deionized water. The resulting dual-nanoparticle-loaded fabric was immersed in the solution for 5 minutes. The fabric was removed, excess liquid on the surface was wiped off, and the fabric was dried in an 80°C oven to obtain the hydrophilic dual-nanoparticle-loaded fabric. The hydrophobic agent DowCorning® DC-5200 was sprayed onto one side of the hydrophilic dual-nanoparticle-loaded fabric using a spray gun. The spray gun was used with a nozzle diameter of 0.3 mm, an atomization pressure of 0.25 MPa, and a spray distance of 25 cm. Two coats of the fabric were applied with a 1-minute interval between coats.

[0042] The reflectivity of the sample in the solar band was measured using an ultraviolet-visible-near-infrared spectrophotometer. The integrating sphere accessory is provided with the spectrophotometer. The weighted reflectivity of the metafabric in the solar spectrum band was measured to be 89.44%. The emissivity of the metafabric in the mid-infrared band was measured using a Fourier transform infrared spectrometer equipped with an integrating sphere. The weighted emissivity of the material was measured to be 96.27%.

[0043] Using the same bacterial culture method and testing method as Example 1, the antibacterial rates of the super fabric against Escherichia coli and Staphylococcus aureus were 94.2% and 93.7%, respectively, showing excellent antibacterial effects.

[0044] Example 3: A raw cotton fabric (4 × 4 cm) was sequentially immersed in acetone, ethanol, and deionized water and ultrasonically treated for 10 minutes. The fabric was then dried in a 60°C oven to constant weight. The fabric was then immersed in 20% ammonia solution (15 mL) at 200 rpm. 4 mL of tetraethyl orthosilicate and 1 mL of KH560 were thoroughly mixed in 20 mL of anhydrous ethanol and added to the fabric A solution at a rate of 3 mL / min. The mixture was stirred at room temperature for 10 minutes at 200 rpm. After stirring, the mixture was allowed to stand for 6 hours. The cotton fabric with in situ silica growth was removed, washed, and dried. 3 g of 500 nm zinc oxide was dispersed in 50 mL of ethanol / water (ethanol / water volume ratio 1:1) and ultrasonically treated at 300 W for 20 minutes. The silica-modified fabric was placed in the dispersion at room temperature, the rotation speed was controlled at 200 rpm, 0.5 mL of silane coupling agent and 1 mL of ammonia solution were added, and the mixture was reacted for 3 h, then washed and dried to prepare the double-nanoparticle-loaded fabric.

[0045] 1 g of polyvinyl alcohol was dissolved in 19 g of deionized water to prepare a hydrophilic modification solution. The resulting dual-nanoparticle-loaded fabric was immersed in the hydrophilic modification solution for 10 minutes. The fabric was removed, excess liquid on the surface wiped off, and dried in an 80°C oven to produce the hydrophilic dual-nanoparticle-loaded fabric. The hydrophobic agent Dow Corning® DC-5200 was sprayed onto one side of the hydrophilic dual-nanoparticle-loaded fabric using a spray gun. The spray gun was set at a nozzle diameter of 0.3 mm, an atomization pressure of 0.25 MPa, and a spray distance of 25 cm. Two coats of the fabric were applied with a 1-minute interval between coats.

[0046] The reflectivity of the sample in the solar band was measured using an ultraviolet-visible-near-infrared spectrophotometer. The integrating sphere accessory is provided with the spectrophotometer. The weighted reflectivity of the metafabric in the solar spectrum band was measured to be 83.41%. The emissivity of the metafabric in the mid-infrared band was measured using a Fourier transform infrared spectrometer equipped with an integrating sphere. The weighted emissivity of the material was measured to be 92.58%.

[0047] Using the same bacterial culture method and testing method as Example 1, the antibacterial rates of the super fabric against Escherichia coli and Staphylococcus aureus were 90.3% and 87.6%, respectively, showing excellent antibacterial effects.

[0048] Example 4: A raw cotton fabric (4 × 4 cm) was sequentially immersed in acetone, ethanol, and deionized water and ultrasonically treated for 10 minutes. The fabric was then dried in an oven at 60°C to constant weight. The fabric was then immersed in 20% ammonia solution (15 mL) at 200 rpm. 4 mL of tetraethyl orthosilicate and 1 mL of KH560 were thoroughly mixed in 20 mL of anhydrous ethanol. The mixture was then added to the A-fabric solution at a rate of 3 mL / min and stirred at room temperature for 10 minutes at 200 rpm. After stirring, the mixture was allowed to stand for 6 hours. The cotton fabric with in situ silica growth was removed and washed and dried. 3 g of kaolin was dispersed in 50 mL of ethanol / water (ethanol / water volume ratio 1:1) and ultrasonically treated at 300 W for 20 minutes. The silica-modified fabric was placed in the dispersion at room temperature at 200 rpm. 1 mL of silane coupling agent and 2 mL of ammonia solution were added. The mixture reacted for 3 hours and then washed and dried to prepare the dual-nanoparticle-loaded fabric.

[0049] 0.4 g of alkyl glycoside and 1.6 g of polyvinyl alcohol were dissolved in 18 g of deionized water to prepare a hydrophilic modification solution. The resulting dual-nanoparticle-loaded fabric was immersed in the hydrophilic modification solution for 10 minutes. The fabric was removed, excess liquid on the surface was wiped off, and the fabric was dried in an 80°C oven to prepare the hydrophilic dual-nanoparticle-loaded fabric. The hydrophobic agent DowCorning® DC-5200 was sprayed onto one side of the hydrophilic dual-nanoparticle-loaded fabric using a spray gun. The spray gun was used with a nozzle diameter of 0.3 mm, an atomization pressure of 0.25 MPa, and a spray distance of 25 cm. Two coats of the fabric were applied with a 1-minute interval between coats.

[0050] The reflectivity of the sample in the solar band was measured using an ultraviolet-visible-near-infrared spectrophotometer. The integrating sphere accessory is provided with the spectrophotometer. The weighted reflectivity of the metafabric in the solar spectrum band was measured to be 71.29%. The emissivity of the metafabric in the mid-infrared band was measured using a Fourier transform infrared spectrometer equipped with an integrating sphere. The weighted emissivity of the material was measured to be 94.02%.

[0051] Using the same bacterial culture method and testing method as Example 1, the antibacterial rates of the super fabric against Escherichia coli and Staphylococcus aureus were 95.3% and 94.3%, respectively, showing excellent antibacterial effects.

[0052] Example 5: A raw cotton fabric (4 × 4 cm) was sequentially immersed in acetone, ethanol, and deionized water, ultrasonically treated for 10 minutes, and then dried in an oven at 60°C to constant weight. The cotton fabric was then immersed in a 20% dilute hydrochloric acid solution (15 mL) at 200 rpm. 4 mL of tetraethyl orthosilicate and 1 mL of KH560 were thoroughly mixed in 20 mL of anhydrous ethanol. The mixture was then added to the A-fabric solution at a rate of 3 mL / min and stirred at room temperature for 10 minutes at 200 rpm. After stirring, the mixture was allowed to stand for 6 hours. The cotton fabric with in situ silica growth was removed and washed and dried. 3 g of titanium dioxide was dispersed in 50 mL of ethanol / water (ethanol / water volume ratio 1:1) and ultrasonically treated at 300 W for 20 minutes. The silica-modified fabric was placed in the dispersion at room temperature at 200 rpm. 2 mL of silane coupling agent and 1 mL of dilute hydrochloric acid solution were added. The mixture reacted for 3 hours and then washed and dried to prepare the dual-nanoparticle-loaded fabric.

[0053] 0.2 g of chitosan and 0.8 g of polyvinyl alcohol were dissolved in 19 g of deionized water to prepare a hydrophilic modification solution. The resulting dual-nanoparticle-loaded fabric was immersed in the hydrophilic modification solution for 10 minutes. The fabric was removed, the excess liquid on the surface was wiped off, and the fabric was dried in an 80°C oven to prepare the hydrophilic dual-nanoparticle-loaded fabric. The hydrophobic agent DowCorning® DC-5200 was sprayed onto one side of the hydrophilic dual-nanoparticle-loaded fabric using a spray gun. The spray gun was used with a nozzle diameter of 0.3 mm, an atomization pressure of 0.25 MPa, and a spray distance of 25 cm. Three coats of the fabric were applied with 1-minute intervals.

[0054] The reflectivity of the sample in the solar band was measured using an ultraviolet-visible-near-infrared spectrophotometer. The integrating sphere accessory is provided with the spectrophotometer. The weighted reflectivity of the metafabric in the solar spectrum band was measured to be 91.09%. The emissivity of the metafabric in the mid-infrared band was measured using a Fourier transform infrared spectrometer equipped with an integrating sphere. The weighted emissivity of the material was measured to be 95.28%.

[0055] Using the same bacterial culture and testing methods as in Example 1, the antibacterial rates of the super fabric against Escherichia coli and Staphylococcus aureus were 98.2% and 97.4%, respectively, demonstrating excellent antibacterial effects.

[0056] Table 1 Comparison of test results of Examples 1 to 5 and Comparative Examples 1 to 2 As shown in the Examples and Comparative Examples in Table 1, the silica size distribution controlled by the amount of tetraethyl orthosilicate and the amount of titanium dioxide are directly related to the reflectivity and emissivity of the modified metafabric. Excessive amounts of tetraethyl orthosilicate and titanium dioxide (Comparative Example 1) will cause the particles to form polydisperse secondary agglomerates, resulting in the shedding of micron-sized particles on the fabric surface, thereby affecting the optical properties of the fabric. Excessive amounts of tetraethyl orthosilicate and titanium dioxide (Comparative Example 2) will reduce the radiative cooling effect of the fabric. It can be seen that the particle size and amount in Example 1 are optimal.

[0057] Therefore, in Examples 2, 3, and 4, the dosage of tetraethyl orthosilicate was retained from Example 1, while the type of high-refractive-index inorganic nanoparticles was changed. However, the reflectivity and emissivity were significantly lower than those in Example 1, indicating that the type of high-refractive-index inorganic nanoparticles in Example 1 was optimal. In Experimental Examples 3, 4, and 5, the ratios and types of the components in the hydrophilic modifier were adjusted. The results showed that the antibacterial rates of the fabric against Escherichia coli and Staphylococcus aureus were lower than those in Example 1, indicating that the ratios and types of the components in the hydrophilic modifier in Example 1 were optimal.

[0058] The above embodiments of the present invention are intended to illustrate the present invention rather than to limit the present invention. Any changes within the equivalent meaning and scope of the claims of the present invention should be considered to be included within the scope of the claims.

Claims

1. A method for preparing Janus cotton fabric with radiant cooling and antibacterial functions, characterized in that: The following steps are involved: Step 1: Pretreatment of cotton fabric: soaking the original cotton fabric in acetone, ethanol, and deionized water in sequence and ultrasonically treating the fabric to expose the cellulose hydroxyl active sites; then drying the fabric in an oven to a constant weight to obtain the pretreated cotton fabric; Step 2, in situ growth of biomimetic silica nanosheath: The catalyst I solution is diluted with deionized water as solution A, and the pretreated cotton fabric is immersed in solution A and interfacial activation is performed under constant temperature magnetic stirring; tetraethyl orthosilicate is used as a silicon source and is fully mixed with a silane coupling agent in anhydrous ethanol to prepare solution B; solution B is added dropwise to the solution A-fabric system at a microfluidic injection rate to allow SiO2 nanoclusters to grow epitaxially along the cotton fiber axis, and stirred at room temperature for 10-30 minutes, with the stirring rate controlled at 200-800 rpm; after the stirring is completed, the mixed solution is allowed to stand for 1-24 hours, and the cotton fabric with in situ silica growth is taken out. The reaction product is washed with deionized water several times to remove unreacted tetraethyl orthosilicate and silane coupling agent, and then placed in a 40-60°C oven to dry to constant weight to prepare cotton@SiO2 fabric; Step 3: Plasmon resonance modification of high-refractive-index nanoparticles: The high-refractive-index nanoparticles are ultrasonically dispersed in an ethanol-water solution to obtain a high-refractive-index nanoparticle dispersion. Cotton@SiO2 fabric is placed in the dispersion at room temperature and mechanically stirred to completely immerse the fabric in the dispersion. A silane coupling agent and catalyst II are added to chemically bond the nanoparticles to the gaps in the SiO2 network, forming a dual-scale photonic crystal structure. After the reaction, the product is washed with deionized water multiple times to remove unreacted nanoparticles and silane coupling agent, and then dried in an oven at 40-60°C to constant weight to prepare a dual-nanoparticle-loaded fabric. Step 4, hydrophilic interface modification: using biomacromolecule self-assembly technology, immerse the double-nanoparticle-loaded fabric prepared in step 3 in a hydrophilic modification solution for 1-10 minutes, remove the fabric, wipe off excess liquid on the surface of the fabric, and dry it in an oven at 40-80°C to constant weight to prepare a hydrophilic double-nanoparticle-loaded fabric; Step 5, hydrophobic interface modification: Use a spray gun to spray the hydrophobic agent onto the hydrophilic double-nanoparticle-loaded fabric prepared in step 4. The hydrophobic layer and the hydrophilic layer form an asymmetric Janus wetting gradient, which can directionally conduct moisture and inhibit biofilm formation, ultimately obtaining a Janus cotton fabric with radiant cooling and antibacterial functions.

2. The method for preparing Janus cotton fabric with radiant cooling and antibacterial functions according to claim 1, characterized in that: In step 2, the catalyst I is selected from at least one of the following: dilute hydrochloric acid, citric acid, and ammonia water, and the amount used is 5% to 40% of the mass of deionized water.

3. The method for preparing Janus cotton fabric with radiant cooling and antibacterial functions according to claim 2, characterized in that: In step 3, the catalyst II is at least one selected from the following: dilute hydrochloric acid, citric acid, and aqueous ammonia, and the amount used is 1% to 20% of the mass of the ethanol aqueous solution.

4. The method for preparing Janus cotton fabric with radiant cooling and antibacterial functions according to claim 1, characterized in that: In step 1, considering the reflectivity and transmittance of the raw cotton fabric itself, the raw cotton fabric is selected to be 60s or 80s pure cotton fabric.

5. The method for preparing Janus cotton fabric with radiant cooling and antibacterial functions according to claim 3, characterized in that: In step 2, in order to fully protonate the hydroxyl groups on the cellulose surface (-OH → -OH2 + ), the activation time is 10~30min.

6. The method for preparing Janus cotton fabric with radiant cooling and antibacterial functions according to claim 5, characterized in that: In step 2, considering the SiO2 particle size distribution obtained by in situ sol-gel conversion and its dispersibility on the surface of the fabric fiber, the amount of tetraethyl orthosilicate used is 10% to 30% of the mass of ethanol used.

7. The method for preparing a Janus cotton fabric with radiant cooling and antibacterial functions according to claim 5 or 6, characterized in that: In step 2, the silane coupling agent is selected from at least one of the following: KH550, KH560, and KH570, and the amount used is 1% to 10% of the mass of the ethanol used.

8. The method for preparing Janus cotton fabric with radiant cooling and antibacterial functions according to claim 7, characterized in that: In step 3, the average size of the high refractive index nanoparticles is controlled to be 100 nm to 2000 nm, and the particles are selected from at least one of the following: nano-alumina, nano-titanium dioxide, nano-barium sulfate, nano-hexagonal boron nitride, nano-zirconium oxide, nano-magnesium oxide, nano-zinc oxide, and kaolin.

9. The method for preparing Janus cotton fabric with radiant cooling and antibacterial functions according to claim 8, characterized in that: The mass dosage of the high refractive index nanoparticles is 1-10% of the mass dosage of the ethanol aqueous solution.

10. The method for preparing Janus cotton fabric with radiant cooling and antibacterial functions according to claim 8, characterized in that: In step 5, the fabric is sprayed on one side 2 to 3 times with a nozzle diameter of 0.3-0.5 mm, an atomization pressure of 0.15-0.25 MPa, and a spraying distance of 15-25 cm, with an interval of 1 minute between each time.

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