Photo-thermal cotton thread capable of being flexibly woven and preparation method

Abstract

The invention discloses a preparation method of a photo-thermal cotton thread capable of being flexibly woven. The preparation method specifically comprises the following steps: pretreating a cotton thread; the preparation method comprises the following steps: dissolving dopamine hydrochloride and tris (hydroxymethyl) aminomethane in distilled water, and dropwise adding an ammonia water solution until the pH value of a mixed solution is 8.4-8.6, so as to obtain an in-situ polymerization reaction solution; the pretreated cotton thread is placed in the in-situ polymerization reaction solution for stirring reaction, washing and vacuum drying are carried out, and the polydopamine modified cotton thread is obtained; silver nanoparticles serve as a photo-thermal absorption layer, and photo-thermal cotton threads which have photo-thermal conversion capacity and can be flexibly woven are prepared. According to the method, silver nanoparticles are reduced on the surface of the cotton fabric by adopting a simple one-step reduction method, then the photo-thermal cotton thread which has photo-thermal conversion capacity and can be flexibly woven is prepared, the solar spectrum absorption rate of the photo-thermal cotton thread is larger than 85%, the peak temperature of the photo-thermal cotton thread reaches 101.5 DEG C in an outdoor temperature rise test and is 43.9 DEG C higher than that of the cotton fabric, and the heating performance is excellent.

Description

Technical Field

[0001] The present invention belongs to the field of functional fabric preparation, and in particular relates to a method for preparing flexibly woven photothermal cotton yarn, and also relates to flexibly woven photothermal cotton yarn. Background Art

[0002] Textiles play an important role in daily life and can maintain the thermal balance between the human body and the environment. The development of wearable winter fabrics that can generate heat for a long time has become the preferred solution to the problem of keeping warm in winter. As a renewable resource, solar energy has the advantages of abundant sources, environmental protection and easy access. Traditional textiles cannot effectively absorb and convert light energy into heat energy under light conditions, which limits their application potential in the field of photothermal. Photothermal materials can absorb near-infrared light and generate heat through plasma resonance or energy transition bands, thereby achieving rapid local warming. Introducing photothermal conversion materials into the surface of fabrics to give fabrics photothermal properties can achieve human warmth outdoors.

[0003] Cotton thread is comfortable, flexible, and weavable. Through weaving techniques, it can be woven into textiles with diverse structures and excellent breathability. Silver nanoparticles (AgNPs), as nanomaterials, have attracted considerable attention due to their unique physicochemical properties. Their specific size and surface structure cause free electrons on their surface to collectively oscillate when light strikes them, resonating with the incident light. This process rapidly converts light energy into heat. This efficient photothermal conversion capability holds enormous potential for application in a wide range of fields. However, the performance of a single material often has limitations. While traditional cotton thread offers excellent comfort and weavability, it lacks specialized functionality. While silver nanoparticles possess excellent photothermal conversion capabilities, their direct application in real-world situations is limited. Against this backdrop, the technology of coating AgNPs onto the surface of cotton thread has emerged. This not only complements the performance of the two materials but also imparts exceptional photothermal conversion capabilities to cotton thread. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing flexibly woven photothermal cotton yarn, thereby solving the problem of poor photothermal performance of existing cotton yarn.

[0005] The second object of the present invention is to provide the above-mentioned photothermal cotton thread that can be flexibly woven.

[0006] The technical solution adopted by the present invention is a method for preparing a flexibly woven photothermal cotton thread, which is specifically implemented according to the following steps: Step 1, pre-treating the cotton thread; Step 2: dissolving dopamine hydrochloride and tris(hydroxymethylaminomethane) in distilled water to form a mixed solution; then adding an ammonia solution dropwise until the pH of the mixed solution is 8.4-8.6 to obtain an in situ polymerization reaction solution; placing the pretreated cotton thread in the in situ polymerization reaction solution and stirring the reaction; after the stirring reaction is completed, taking out the cotton thread, washing it with distilled water and anhydrous ethanol in sequence, and vacuum drying it to obtain a polydopamine-modified cotton thread; Step 3: After step 2, silver nanoparticles are used as a photothermal absorption layer to prepare a flexibly woven photothermal cotton thread with photothermal conversion capability.

[0007] The present invention is also characterized in that: In step 1, specifically: Sodium hydroxide is dissolved in distilled water and stirred evenly to obtain a sodium hydroxide solution; cotton thread is immersed in the sodium hydroxide solution and heated in a water bath for reaction at a reaction temperature of 80-85° C. and a reaction time of 1-2 hours; and the cotton thread is washed and dried to obtain pretreated cotton thread.

[0008] In step 2, the mass ratio of dopamine hydrochloride, tris(hydroxymethyl)aminomethane and distilled water is 0.30-0.50:1.80-3.00:100-300; the reaction temperature is 24-26° C., and the reaction time is 24 h.

[0009] In step 3, specifically: Step 3.1, dissolving AgNO3 in distilled water to obtain an AgNO3 solution, adding an aqueous ammonia solution dropwise under continuous stirring, and stopping the addition when observing that the solution system undergoes a phase transition from a clear state to a turbid state and then gradually returns to a clear state to obtain a silver ammonia complex solution; Step 3.2, immersing the polydopamine-modified cotton thread in a silver-ammonia complex solution and stirring the solution to obtain a silver-ammonia-cotton thread composite system; Step 3.3, slowly add the reducing agent solution to the silver ammonia-cotton thread composite system under continuous stirring, and use ammonia water to maintain the pH of the reaction system at 10.0-11.0, and carry out in situ reduction reaction under water bath conditions. After the reaction is completed, wash with distilled water and anhydrous ethanol in turn, and vacuum dry to obtain a flexibly woven photothermal cotton thread.

[0010] In step 3.2, the stirring treatment temperature is 23-27° C., and the stirring treatment time is 3-4 h.

[0011] In step 3.3, the reaction temperature is 50-55° C., and the reaction time is 4-8 hours; the reducing agent solution is prepared by mixing glucose and distilled water in a mass ratio of 1.9-3.9:100-300.

[0012] Another technical solution adopted by the present invention is the photothermal cotton thread prepared by the preparation method of the photothermal cotton thread that can be flexibly woven.

[0013] The beneficial effects of the present invention are: The method of the present invention selects cotton yarn with good air permeability and wearing comfort as a base material, uses a simple one-step reduction method to reduce silver nanoparticles on the surface of the cotton yarn, and then produces a flexibly weavable photothermal cotton yarn with photothermal conversion capability. The solar spectrum absorption rate of the cotton yarn is greater than 85%. In an outdoor temperature rise test (108°58′ east longitude and 34°23′ north latitude), the peak temperature reaches 101.5°C, which is 43.9°C higher than the peak temperature of cotton fabric, and has excellent heating performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a solar spectrum absorptivity curve of the silver nanoparticle-modified cotton thread material prepared in Example 2. DETAILED DESCRIPTION

[0015] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] The method for preparing a flexibly braided photothermal cotton thread of the present invention uses polydopamine as a bonding layer and a silver nanoparticle reduction layer, and silver nanoparticles as a photothermal absorption layer to prepare a flexibly braided photothermal cotton thread with photothermal conversion capability, and is specifically implemented in the following steps: Step 1, pre-treating the cotton thread; Dissolve sodium hydroxide in distilled water and stir evenly to obtain a sodium hydroxide solution with a concentration of 0.25 mol / L; Immerse a cotton thread with a diameter of 1.00 mm in a sodium hydroxide solution and conduct a water bath heating reaction; the reaction temperature is 80-85°C and the reaction time is 1-2 hours; remove excess grease from the surface of the cotton thread, wash it, and dry it to obtain a pretreated cotton thread; The mass ratio of cotton thread to sodium hydroxide solution is 0.01:101.00; Step 2, preparing polydopamine-modified cotton thread; Dopamine hydrochloride and tris(hydroxymethyl)aminomethane (Tris) were dissolved in distilled water to form a mixed solution; then, a 28% ammonia solution was added dropwise until the pH of the mixed solution reached 8.4-8.6 to obtain an in-situ polymerization reaction solution; The mass ratio of dopamine hydrochloride, tris(hydroxymethyl)aminomethane and distilled water is 0.30-0.50: 1.80-3.00: 100-300; The pretreated cotton thread was placed in the in-situ polymerization reaction solution and stirred for reaction at a temperature of 24-26°C for 24 hours. Be careful not to tangle the cotton thread during stirring. After the stirring reaction, the cotton thread was taken out and washed with distilled water and anhydrous ethanol in sequence, and vacuum dried to obtain the polydopamine-modified cotton thread. Step 3: Prepare flexibly woven photothermal cotton thread; specifically: Step 3.1, dissolving AgNO3 in distilled water to obtain an AgNO3 solution, and adding dropwise an aqueous ammonia solution having a volume concentration of 28% under continuous stirring. When the solution system undergoes a phase transition from a clear state to a turbid state and then gradually to a clear state, the addition is stopped to obtain a silver ammonia complex solution; The mass ratio of AgNO3 to distilled water is 2-4:100-300; Step 3.2, immersing the polydopamine-modified cotton thread in a silver-ammonia complex solution and stirring the solution at a temperature of 23-27° C. for 3-4 hours. Note that the stirring speed should be controlled uniformly during the stirring process to prevent the cotton thread from becoming entangled, thereby obtaining a silver-ammonia-cotton thread composite system; Step 3.3: Slowly add the reducing agent solution to the silver-ammonia-cotton thread composite system under continuous stirring, and use 28% ammonia water to maintain the pH of the reaction system at 10.0-11.0. Perform an in situ reduction reaction in a water bath at a reaction temperature of 50-55°C for 4-8 hours. After the reaction is completed, wash with distilled water and anhydrous ethanol three times in sequence, and vacuum dry to obtain a silver nanoparticle-modified cotton thread with photothermal conversion performance, i.e., a flexibly woven photothermal cotton thread. The reducing agent solution is prepared by mixing glucose and distilled water in a mass ratio of 1.9-3.9:100-300; The method of the present invention utilizes the adhesive properties of polydopamine (PDA) and its ability to reduce silver ions to introduce AgNPs into cotton thread, imparting photothermal conversion capabilities to the cotton thread, thereby producing photothermal cotton thread. Through a weaving process, this can be fabricated into a wearable material with photothermal properties. The PDA molecular structure is rich in catechol and amino groups, which can bind to the hydroxyl groups on the cotton thread surface through interactions such as hydrogen bonds and van der Waals forces, enhancing the bonding between the functional material and the cotton thread. Furthermore, the phenolic hydroxyl groups and nitrogen-containing groups in the PDA layer have a strong adsorption effect on silver ammonium ions. The weak reducing properties of PDA can be utilized to reduce the adsorbed silver ammonium ions to AgNPs. This photothermal cotton thread can be fabricated into textiles with diverse structures and good breathability through a weaving process, meeting wearable comfort requirements for the human body.

[0017] Example 1 The method for preparing the flexibly woven photothermal cotton yarn of the present invention is specifically implemented according to the following steps: Step 1, pre-treating the cotton thread; Dissolve 1.00 g of sodium hydroxide in 100 ml of distilled water and stir well to obtain a sodium hydroxide solution; A cotton thread with a diameter of 1.00 mm and a mass of 10.00 g was immersed in the sodium hydroxide solution and reacted in a water bath at 80°C for 1 hour to remove excess grease from the surface of the cotton thread. The cotton thread was then taken out, thoroughly cleaned, and dried to obtain the pretreated cotton thread. Step 2, preparing polydopamine-modified cotton thread; Weigh 0.30 g of dopamine hydrochloride and 1.80 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve them in 100 mL of distilled water. Then, add ammonia solution dropwise until the pH of the mixture reaches 8.4 to obtain an in situ polymerization reaction solution. Place the pretreated cotton thread in the in-situ polymerization reaction solution and stir the reaction at 24°C for 24 hours. Be careful not to tangle the cotton thread during stirring. After stirring, remove the cotton thread and immerse it in distilled water and anhydrous ethanol three times (5 minutes each time) to thoroughly rinse. Then place it in a vacuum drying oven and dry it at 50°C to constant weight. Step 3: Prepare flexibly woven photothermal cotton thread; specifically: Weigh 2.00 g of AgNO₃ (analytical grade) and dissolve it in 100 mL of distilled water. Add ammonia solution dropwise while stirring continuously. Stop adding when the solution undergoes a phase transition from clear to turbid and then gradually to clear, to obtain a silver-ammine complex solution. Immerse polydopamine-modified cotton thread in the silver-ammine complex solution. Stir at 23°C for 3 hours. Maintain a constant stirring speed during stirring to prevent tangling of the thread.

[0018] A 100 mL reducing solution containing 1.90 g of glucose was prepared. The reducing agent solution was slowly added to the silver-ammonia-cotton thread composite system under continuous stirring, maintaining the reaction system at a pH of 10.0. The in situ reduction reaction was carried out in a 50°C water bath for 4 hours. After the reaction, the functionalized cotton thread was removed and thoroughly rinsed by immersing it in distilled water and then anhydrous ethanol three times (10 minutes each time). Finally, it was dried in a vacuum drying oven at 60°C to constant weight, yielding silver nanoparticle-modified cotton thread with photothermal conversion properties.

[0019] Example 2 The method for preparing the flexibly woven photothermal cotton yarn of the present invention is specifically implemented according to the following steps: Step 1, pre-treating the cotton thread; Dissolve 1.00 g of sodium hydroxide in 100 ml of distilled water and stir well to obtain a sodium hydroxide solution; A cotton thread with a diameter of 1.00 mm and a mass of 10.00 g was immersed in the sodium hydroxide solution and reacted in a water bath at 80°C for 1 h to remove excess grease from the surface of the cotton thread. The cotton thread was then taken out, thoroughly cleaned, and dried to obtain the pretreated cotton thread. Step 2, preparing polydopamine-modified cotton thread; Accurately weigh 0.40 g of dopamine hydrochloride and 2.40 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve them in 200 mL of distilled water. Then, add ammonia solution dropwise until the pH of the mixture reaches 8.5 to obtain an in situ polymerization reaction solution. Place the pretreated cotton thread in the in situ polymerization reaction solution and stir the reaction. Maintain the reaction temperature at 25°C and stir the reaction system at a constant speed for 24 hours, taking care not to tangle the cotton thread during stirring. After stirring, remove the cotton thread and immerse it in distilled water and anhydrous ethanol three times (5 minutes each time) to thoroughly rinse. Then, place it in a vacuum drying oven at 50°C and dry it to constant weight.

[0020] Step 3: Prepare flexibly woven photothermal cotton thread; specifically: Weigh 3.00 g of AgNO₃ (analytical grade) and dissolve it in 200 mL of distilled water. Add ammonia solution dropwise while stirring continuously. Stop adding when the solution undergoes a phase transition from clear to turbid and then gradually to clear, to obtain a silver-ammine complex solution. Immerse pre-prepared polydopamine cotton thread in the silver-ammine complex solution. Stir at 24°C for 4 hours. Maintain a constant stirring speed during stirring to prevent tangling of the thread.

[0021] Prepare 200 mL of reducing solution containing 2.90 g of glucose. Slowly add the reducing agent solution to the silver-ammonia-cotton thread composite system under continuous stirring. Maintain the reaction system at a pH of 10.5, and conduct the in situ reduction reaction in a 50°C water bath for 6 h. After the reaction, remove the functionalized cotton thread and rinse thoroughly by immersing it in distilled water and anhydrous ethanol three times (10 min each time). Finally, dry it in a vacuum drying oven at 60°C to constant weight, yielding a silver nanoparticle-modified cotton thread material with photothermal conversion properties.

[0022] Figure 1 This is a solar spectrum absorptivity curve of the silver nanoparticle-modified cotton thread material prepared in Example 2. As can be seen from the figure, the solar spectrum absorptivity of the photothermal cotton thread can reach 84%, which means that the material can effectively capture solar energy and convert it into thermal energy.

[0023] Example 3 The method for preparing the flexibly woven photothermal cotton yarn of the present invention is specifically implemented according to the following steps: Step 1, pre-treating the cotton thread; Dissolve 1.00 g of sodium hydroxide in 100 ml of distilled water and stir well to obtain a sodium hydroxide solution; A cotton thread with a diameter of 1.00 mm and a mass of 10.00 g was immersed in the sodium hydroxide solution and reacted in a water bath at 80°C for 1 hour to remove excess grease on the surface of the cotton thread. The cotton thread was then taken out, thoroughly washed, and dried to obtain the pretreated cotton thread. Step 2, preparing polydopamine-modified cotton thread; Accurately weigh 0.50 g of dopamine hydrochloride and 3.00 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve them in 300 mL of distilled water. Then, add ammonia solution dropwise until the pH of the mixture reaches 8.5 to obtain an in situ polymerization reaction solution. Place the pretreated cotton thread in the in-situ polymerization solution and stir at 25°C for 24 hours. Be careful not to tangle the thread during stirring. After stirring, remove the thread and immerse it in distilled water and anhydrous ethanol three times (5 minutes each time) to rinse thoroughly. Then, place it in a vacuum drying oven and dry it at 50°C to constant weight.

[0024] Step 3: Prepare flexibly woven photothermal cotton thread; specifically: Weigh 4.00 g of AgNO₃ (analytical grade) and dissolve it in 300 mL of distilled water. Add ammonia solution dropwise while stirring continuously. Stop adding when the solution undergoes a phase transition from clear to turbid and then gradually to clear, to obtain a silver-ammine complex solution. Immerse pre-prepared polydopamine cotton thread in the silver-ammine complex solution. Stir at 25°C for 3 hours. Maintain a constant stirring speed during stirring to prevent tangling of the thread.

[0025] Prepare 300 mL of reducing solution containing 3.90 g of glucose. Slowly add the reducing agent solution to the silver-ammonia-cotton thread composite system under continuous stirring. Maintain the reaction pH at 11.0 and conduct the in situ reduction reaction in a 50°C water bath for 8 h. After the reaction, remove the functionalized cotton thread and rinse thoroughly by immersing it in distilled water and anhydrous ethanol three times (10 min each time). Finally, dry it in a vacuum drying oven at 60°C to constant weight, yielding silver nanoparticle-modified cotton thread with photothermal conversion properties.

[0026] Example 4 The method for preparing the flexibly woven photothermal cotton yarn of the present invention is specifically implemented according to the following steps: Step 1, pre-treating the cotton thread; Dissolve sodium hydroxide in distilled water and stir evenly to obtain a sodium hydroxide solution; The cotton thread with a diameter of 1.00 mm was immersed in a sodium hydroxide solution and heated in a water bath for reaction; the reaction temperature was 85°C and the reaction time was 2 h; the cotton thread was washed and dried to obtain the pretreated cotton thread; Step 2, preparing polydopamine-modified cotton thread; Dopamine hydrochloride and tris(hydroxymethylaminomethane) (Tris) were dissolved in distilled water to form a mixed solution; then, a 28% aqueous ammonia solution was added dropwise until the pH of the mixed solution reached 8.4, thereby obtaining an in-situ polymerization reaction solution; The mass ratio of dopamine hydrochloride, tris(hydroxymethyl)aminomethane and distilled water is 0.50: 3.00: 300; The pretreated cotton thread was placed in the in-situ polymerization reaction solution and stirred for reaction at a temperature of 24°C for 24 hours. Be careful not to tangle the cotton thread during stirring. After the stirring reaction, the cotton thread was taken out and washed with distilled water and anhydrous ethanol in sequence, and vacuum dried to obtain a polydopamine-modified cotton thread. Step 3: Prepare flexibly woven photothermal cotton thread; specifically: Step 3.1, dissolving AgNO3 in distilled water to obtain an AgNO3 solution, and adding dropwise an aqueous ammonia solution having a volume concentration of 28% under continuous stirring. When the solution system undergoes a phase transition from a clear state to a turbid state and then gradually to a clear state, the addition is stopped to obtain a silver ammonia complex solution; The mass ratio of AgNO3 to distilled water is 4:100; Step 3.2, immersing the polydopamine-modified cotton thread in the silver-ammonia complex solution and stirring the solution at a temperature of 23° C. for 3 h. Note that the stirring speed should be controlled uniformly during the stirring process to prevent the cotton thread from tangling, thereby obtaining a silver-ammonia-cotton thread composite system; Step 3.3, slowly adding the reducing agent solution to the silver-ammonia-cotton thread composite system under continuous stirring, and using ammonia water with a volume concentration of 28% to maintain the pH of the reaction system at 10.0, performing an in situ reduction reaction in a water bath at a reaction temperature of 55°C for 4 hours. After the reaction is completed, washing with distilled water and anhydrous ethanol three times in sequence, and vacuum drying to obtain a silver nanoparticle-modified cotton thread with photothermal conversion performance, i.e., a flexibly woven photothermal cotton thread; The reducing agent solution was prepared by mixing glucose and distilled water at a mass ratio of 1.9:100; Example 5 The method for preparing the flexibly woven photothermal cotton yarn of the present invention is specifically implemented according to the following steps: Step 1, pre-treating the cotton thread; Dissolve sodium hydroxide in distilled water and stir evenly to obtain a sodium hydroxide solution; A cotton thread with a diameter of 1.00 mm was immersed in a sodium hydroxide solution and heated in a water bath for reaction; the reaction temperature was 85°C and the reaction time was 2 h; excess grease on the surface of the cotton thread was removed, and the thread was washed and dried to obtain the pretreated cotton thread; Step 2, preparing polydopamine-modified cotton thread; Dopamine hydrochloride and tris(hydroxymethyl)aminomethane (Tris) were dissolved in distilled water to form a mixed solution; then, a 28% ammonia solution was added dropwise until the pH of the mixed solution reached 8.6, thereby obtaining an in-situ polymerization reaction solution; The pretreated cotton thread was placed in the in-situ polymerization reaction solution and stirred for reaction at a temperature of 26°C for 24 h. Care was taken not to tangle the cotton thread during stirring. After the stirring reaction, the cotton thread was taken out and washed with distilled water and anhydrous ethanol in sequence, and vacuum dried to obtain the polydopamine-modified cotton thread. Step 3: Prepare flexibly woven photothermal cotton thread; specifically: Step 3.1, dissolving AgNO3 in distilled water to obtain an AgNO3 solution, and adding dropwise an aqueous ammonia solution having a volume concentration of 28% under continuous stirring. When the solution system undergoes a phase transition from a clear state to a turbid state and then gradually to a clear state, the addition is stopped to obtain a silver ammonia complex solution; The mass ratio of AgNO3 to distilled water is 2:300; Step 3.2, immersing the polydopamine-modified cotton thread in the silver-ammonia complex solution and stirring the solution at a temperature of 27° C. for 4 h. Note that the stirring speed should be controlled uniformly during the stirring process to prevent the cotton thread from becoming entangled, thereby obtaining a silver-ammonia-cotton thread composite system; Step 3.3, slowly adding the reducing agent solution to the silver-ammonia-cotton thread composite system under continuous stirring, and using 28% volume concentration of ammonia water to maintain the pH of the reaction system at 11.0, performing an in situ reduction reaction in a water bath at a reaction temperature of 55°C for 8 hours. After the reaction is completed, washing with distilled water and anhydrous ethanol three times in sequence, and vacuum drying to obtain a silver nanoparticle-modified cotton thread with photothermal conversion performance, i.e., a flexibly woven photothermal cotton thread; The reducing agent solution was prepared by mixing glucose and distilled water at a mass ratio of 3.9:300; Example 6 The method for preparing a flexibly braided photothermal cotton thread of the present invention uses cotton thread as a base material. First, the surface of the cotton thread is pretreated with a sodium hydroxide solution to remove excess grease. Then, a self-polymerization reaction of dopamine is carried out on the surface of the cotton thread to form a polydopamine cotton thread. Finally, an in-situ reduction method is used to introduce silver nanoparticles into the surface of the polydopamine cotton thread, thereby preparing a flexibly braided cotton thread with a photothermal conversion function. In this process, polydopamine not only acts as a reducing agent to reduce silver ions to silver nanoparticles, but also plays an excellent bonding role. In this mode, the solar spectrum absorption rate of the photothermal cotton thread is greater than 85%. In an outdoor temperature rise test (108°58′ east longitude; 34°23′ north latitude), its peak temperature reached 101.5°C, which is 43.9°C higher than the peak temperature of pure cotton thread, and has excellent photothermal performance.

Claims

1. A method for preparing a flexibly woven photothermal cotton thread, characterized in that: Please follow the steps below to implement it: Step 1, pre-treating the cotton thread; Step 2: dissolving dopamine hydrochloride and tris(hydroxymethylaminomethane) in distilled water to form a mixed solution; then adding an ammonia solution dropwise until the pH of the mixed solution reaches 8.4-8.6 to obtain an in-situ polymerization reaction solution; The pretreated cotton thread is placed in an in-situ polymerization reaction solution for stirring reaction. After the stirring reaction is completed, the cotton thread is taken out, washed with distilled water and anhydrous ethanol in sequence, and vacuum dried to obtain a polydopamine-modified cotton thread; Step 3: After step 2, silver nanoparticles are used as a photothermal absorption layer to prepare a flexibly woven photothermal cotton thread with photothermal conversion capability.

2. The method for preparing the flexibly braided photothermal cotton thread according to claim 1, characterized in that: In the step 1, specifically: Sodium hydroxide is dissolved in distilled water and stirred evenly to obtain a sodium hydroxide solution; cotton thread is immersed in the sodium hydroxide solution, heated in a water bath for reaction, washed, and dried to obtain pretreated cotton thread.

3. The method for preparing the flexibly braided photothermal cotton thread according to claim 2, wherein: The reaction temperature is 80-85°C and the reaction time is 1-2h.

4. The method for preparing the flexibly braided photothermal cotton thread according to claim 1, wherein: In the step 2, the mass ratio of dopamine hydrochloride, tris(hydroxymethyl)aminomethane and distilled water is 0.30-0.50:1.80-3.00:100-300; the reaction temperature is 24-26° C., and the reaction time is 24 h.

5. The method for preparing the flexibly braided photothermal cotton thread according to claim 1, characterized in that: In the step 3, specifically: Step 3.1, dissolving AgNO3 in distilled water to obtain an AgNO3 solution, adding an aqueous ammonia solution dropwise under continuous stirring, and stopping the addition when observing that the solution system undergoes a phase transition from a clear state to a turbid state and then gradually returns to a clear state to obtain a silver ammonia complex solution; Step 3.2, immersing the polydopamine-modified cotton thread in a silver-ammonia complex solution and stirring the solution to obtain a silver-ammonia-cotton thread composite system; Step 3.3, slowly add the reducing agent solution to the silver ammonia-cotton thread composite system under continuous stirring, and use ammonia water to maintain the pH of the reaction system at 10.0-11.0, and carry out in situ reduction reaction under water bath conditions. After the reaction is completed, wash with distilled water and anhydrous ethanol in turn, and vacuum dry to obtain a flexibly woven photothermal cotton thread.

6. The method for preparing the flexibly braided photothermal cotton thread according to claim 5, characterized in that: In the step 3.2, the stirring treatment temperature is 23-27° C., and the stirring treatment time is 3-4 h.

7. The method for preparing the flexibly braided photothermal cotton thread according to claim 5, characterized in that: In the step 3.3, the reaction temperature is 50-55° C., and the reaction time is 4-8 hours; the reducing agent solution is prepared by mixing glucose and distilled water in a mass ratio of 1.9-3.9:100-300.

8. The photothermal cotton thread prepared by the method for preparing the flexibly braided photothermal cotton thread according to any one of claims 1 to 7.

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