A modified carbon nanotube polyvinyl alcohol electrothermal composite film and its preparation method

Abstract

The present invention discloses a modified carbon nanotube / polyvinyl alcohol electrothermal composite film and a preparation method thereof, wherein the electrothermal composite film comprises a substrate and a conductive filler deposited layer by layer on the surface of the substrate; wherein the conductive filler is a multi-walled carbon nanotube functionalized with epigallocatechin gallate. A modified carbon nanotube / polyvinyl alcohol electrothermal composite film was prepared by a layer-by-layer deposition method. The electrothermal composite film has good electrothermal performance, namely, a rapid temperature response, and can reach a steady-state temperature within 90 seconds. By adjusting the multi-walled carbon nanotube content and applying voltage, the performance of the electrothermal composite film can be precisely controlled. The prepared electrothermal composite film exhibits excellent mechanical and electrothermal properties, and has a rapid temperature response, and can reach a steady-state temperature in a short time. The electrothermal composite film also has good flexibility and elasticity, and can be widely used in the fields of wearable heating cotton fabrics, physical therapy and health, floor heating, deicing / defrosting devices, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing electric heating composite films based on carbon nanotubes and polyvinyl alcohol, and in particular relates to a modified carbon nanotube polyvinyl alcohol electric heating composite film and a preparation method thereof. Background Art

[0002] Electrothermal materials can easily and controllably convert electrical energy into thermal energy using the Joule effect, and therefore have been widely used in our lives. Traditional electrothermal materials are nickel-chromium alloys and iron-aluminum alloys, but they have some disadvantages, such as high rigidity, low heating efficiency, complex manufacturing process, poor flexibility, and high cost. In recent years, indium tin oxide (ITO) has attracted significant research interest due to its high electrical conductivity. Unfortunately, the scarcity and high cost of indium, as well as the complex and time-consuming preparation process of ITO films, which usually requires high temperatures and exhibits brittleness under mechanical deformation, have limited its widespread application in the field of electrothermal materials.

[0003] Some low-dimensional carbon nanomaterials, including graphene (GE), carbon nanotubes (CNTs), silver nanowires (AgNWs), etc., are used as the main electrothermal materials due to their excellent electrical / thermal conductivity. Among them, carbon nanotubes are considered to be an alternative to ITO due to their excellent electrical conductivity, good flexibility and thermal stability, and have been widely studied. As a one-dimensional carbon nanomaterial, carbon nanotubes have extremely high electrical conductivity, thermal conductivity and excellent mechanical properties, and are therefore considered to be an ideal raw material for electrothermal applications. However, due to the strong van der Waals attraction between individual carbon nanotubes, carbon nanotubes are prone to agglomeration, making it difficult to achieve dispersion, which greatly affects the bonding between carbon nanotubes and the substrate. The preparation of composite electrothermal films requires not only conductive materials, but also the selection of a substrate as a support. Epoxy resin is used as a traditional substrate material, but it has some disadvantages, such as being unable to withstand bending or deformation, and having too high a viscosity resulting in poor dispersion effect.

[0004] Therefore, how to provide a modified carbon nanotube polyvinyl alcohol electrothermal composite film and a preparation method thereof, and realize the deposition of functionalized carbon nanotubes on a substrate to prepare an electrothermal composite film, is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] To this end, the present invention provides a modified carbon nanotube polyvinyl alcohol electrothermal composite film and a preparation method thereof to solve the relevant technical problems existing in the prior art, so that the obtained electrothermal composite film exhibits excellent mechanical properties and electrothermal properties, and has a rapid temperature response, so as to achieve wide application in the field of electrothermal.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] According to a first aspect of the present invention, there is provided a modified carbon nanotube polyvinyl alcohol electrothermal composite film comprising a substrate and a conductive filler deposited layer by layer on the surface of the substrate;

[0008] Wherein, the conductive filler is multi-walled carbon nanotube functionalized with epigallocatechin gallate.

[0009] Furthermore, the multi-walled carbon nanotubes (MWCNTs) have a purity of 98 wt.%, a length of 0.5-2 μm, and an outer diameter of 10-20 nm.

[0010] Furthermore, the epigallocatechin gallate (EGCG) powder is AR grade.

[0011] According to a second aspect of the present invention, there is provided a method for preparing an electrothermal composite film, comprising the following steps:

[0012] (1) Multi-walled carbon nanotubes (MWCNTs) and epigallocatechin gallate (EGCG) are dispersed in deionized water in a certain proportion; the solution is then vigorously stirred under certain temperature and time conditions to achieve non-covalent modification of the multi-walled carbon nanotubes, and modified carbon nanotubes (E-MWCNTs) powder is obtained by filtration, washing, drying and grinding;

[0013] (2) Dissolve polyvinyl alcohol (PVA) particles in an aqueous solution, heat and stir at 90°C to dissolve them, then add glycerol and hydroxypropyl methylcellulose (HPMC), continue mechanical stirring to completely dissolve them, and place the prepared mixed solution in a vacuum drying oven, evacuate the vacuum, and store overnight to remove bubbles;

[0014] (3) A certain amount of E-MWCNTs and HPMC were dispersed in an N,N-dimethylformamide (DMF) solution and ultrasonically treated. The mixed solution was centrifuged at a certain speed for a certain time, and 90% of the supernatant was collected to obtain an E-MWCNTs dispersion of the corresponding concentration. A certain amount of E-MWCNTs solution was added to a polytetrafluoroethylene (PTFE) mold and then dried in an oven.

[0015] (4) PVA solution was added to the above mold, and continued to dry in an oven, and removed by tweezers to obtain an electrothermal composite film.

[0016] Furthermore, the preparation of the epigallocatechin gallate functionalized multi-walled carbon nanotube (E-MWCNTs) solution is as follows:

[0017] Multi-walled carbon nanotubes (MWCNTs) and epigallocatechin gallate (EGCG) are dispersed in deionized water at a mass ratio of 1:(4-8); the mixture is then stirred in a water bath at 50-70°C for 12-36 hours, and E-MWCNTs powder is obtained by filtration, washing, drying and grinding. Subsequently, a certain amount of E-MWCNTs and hydroxypropyl methylcellulose (HPMC) are dispersed in an N,N-dimethylformamide (DMF) solution, the solution is placed in an ultrasonic mill for ultrasonic dispersion, and the mixed solution is then centrifuged at a speed of 7000-9000 r / min for 10-30 minutes, and 90% of the supernatant is collected to obtain an E-MWCNTs dispersion of the corresponding concentration.

[0018] Furthermore, the conditions for preparing the E-MWCNTs dispersion using an ultrasonic mill are:

[0019] The power is 120-240 watts, the time is 0.5-2 hours, the dispersant is hydroxypropyl methylcellulose (HPMC), and the concentration of the modified carbon nanotube solution is 1-8 mg / mL.

[0020] Furthermore, the hydroxypropyl methylcellulose powder (HPMC) is AR grade; and the polyvinyl alcohol (PVA) has a molecular weight of about 170,000.

[0021] Furthermore, the solid content of the prepared polyvinyl alcohol solution is about 6-10%.

[0022] Furthermore, the ratio of multi-walled carbon nanotubes (MWCNTs) to epigallocatechin gallate (EGCG) is 1:5.

[0023] The present invention has the following advantages:

[0024] 1. The modified carbon nanotube / polyvinyl alcohol electrothermal composite film was prepared by the layer-by-layer deposition (LBL) method. The electrothermal composite film has good electrothermal performance, that is, fast temperature response, and can reach a steady-state temperature within 90 seconds.

[0025] 2. By adjusting the content of multi-walled carbon nanotubes and applying voltage, the performance of the electrothermal composite membrane can be precisely controlled. Since polyvinyl alcohol is a biodegradable material and is environmentally friendly, it is selected as the substrate of the electrothermal composite membrane.

[0026] 3. The prepared electrothermal composite film exhibits excellent mechanical and electrothermal properties, with a rapid temperature response, reaching a steady-state temperature in a short period of time. The electrothermal composite film also has excellent flexibility and elasticity, and can be widely used in wearable heating cotton fabrics, physical therapy and health care, floor heating, deicing / defrosting devices, and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0028] The structures, proportions, sizes, etc. illustrated in this specification are intended only to complement the contents disclosed herein and to facilitate understanding and reading by persons familiar with the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, without affecting the efficacy and objectives of the present invention, shall still fall within the scope of the technical contents disclosed herein.

[0029] Figure 1 Schematic diagram of the resistance of the epigallocatechin gallate modified carbon nanotube / polyvinyl alcohol (E-MWCNT / PVA) electrothermal composite film;

[0030] Figure 2 The scanning electron microscope images of the surface and cross section of the epigallocatechin gallate-modified carbon nanotube / polyvinyl alcohol (E-MWCNT / PVA) electrothermal composite film are shown;

[0031] Figure 3 The time-temperature curve of the electrothermal composite film of carbon nanotube / polyvinyl alcohol (E-MWCNT / PVA) modified with epigallocatechin gallate;

[0032] Figure 4 The test curves of cycling characteristics and stability of epigallocatechin gallate modified carbon nanotube / polyvinyl alcohol (E-MWCNT / PVA) electrothermal composite membrane are shown.

[0033] Figure 5 Far-infrared heating diagram of epigallocatechin gallate-modified carbon nanotube / polyvinyl alcohol (E-MWCNT / PVA) electrothermal composite film in normal and twisted states. DETAILED DESCRIPTION

[0034] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0035] To address existing challenges in this field, we designed a new, simple, and feasible method using multi-walled carbon nanotubes (E-MWCNTs) functionalized with epigallocatechin gallate (EGCG) as a conductive filler and polyvinyl alcohol (PVA) as a matrix. Comparing the dispersion of MWCNTs and E-MWCNTs solutions at the same concentration after standing for a period of time revealed that after prolonged standing, the MWCNTs significantly aggregated, with the majority settling to the bottom of the bottle, while the E-MWCNT dispersion maintained a well-dispersed state. EGCG molecules adsorbed onto the carbon nanotube walls through strong π-π interactions, enhancing the hydrophilicity of the E-MWCNTs. This not only improves the degree of dissolution of the carbon nanotubes in the solvent but also effectively enhances their adhesion to the matrix.

[0036] According to a first aspect of the present invention, there is provided a modified carbon nanotube polyvinyl alcohol electrothermal composite film comprising a substrate and a conductive filler deposited layer by layer on the surface of the substrate;

[0037] The conductive filler is multi-walled carbon nanotubes functionalized with epigallocatechin gallate.

[0038] Among them, the multi-walled carbon nanotubes (MWCNTs) have a purity of 98 wt.%, a length of 0.5-2 μm, and an outer diameter of 10-20 nm.

[0039] Among them, epigallocatechin gallate (EGCG) powder is AR grade.

[0040] According to a second aspect of the present invention, there is provided a method for preparing an electrothermal composite film, comprising the following steps:

[0041] (1) Multi-walled carbon nanotubes (MWCNTs) and epigallocatechin gallate (EGCG) are dispersed in deionized water in a certain proportion; the solution is then vigorously stirred under certain temperature and time conditions to achieve non-covalent modification of the multi-walled carbon nanotubes, and modified carbon nanotubes (E-MWCNTs) powder is obtained by filtration, washing, drying and grinding;

[0042] (2) Dissolve polyvinyl alcohol (PVA) particles in an aqueous solution, heat and stir at 90°C to dissolve them, then add glycerol and hydroxypropyl methylcellulose (HPMC), continue mechanical stirring to completely dissolve them, and place the prepared mixed solution in a vacuum drying oven, evacuate the vacuum, and store overnight to remove bubbles;

[0043] (3) A certain amount of E-MWCNTs and HPMC were dispersed in an N,N-dimethylformamide (DMF) solution and ultrasonically treated. The mixed solution was centrifuged at a certain speed for a certain time, and 90% of the supernatant was collected to obtain an E-MWCNTs dispersion of the corresponding concentration. A certain amount of E-MWCNTs solution was added to a polytetrafluoroethylene (PTFE) mold and then dried in an oven.

[0044] (4) PVA solution was added to the above mold, and continued to dry in an oven, and removed by tweezers to obtain an electrothermal composite film.

[0045] The relationship between resistance and MWCNT content when the ratio of multi-walled carbon nanotubes (MWCNT) to epigallocatechin gallate (EGCG) is different. Figure 1 As shown, it can be seen that as the carbon nanotube content increases, the resistance of the electrothermal composite film decreases.

[0046] The preparation of the epigallocatechin gallate functionalized multi-walled carbon nanotubes (E-MWCNTs) solution is as follows:

[0047] Multi-walled carbon nanotubes (MWCNTs) and epigallocatechin gallate (EGCG) are dispersed in deionized water at a mass ratio of 1:(4-8); the mixture is then stirred in a water bath at 50-70°C for 12-36 hours, and E-MWCNTs powder is obtained by filtration, washing, drying and grinding. Subsequently, a certain amount of E-MWCNTs and hydroxypropyl methylcellulose (HPMC) are dispersed in an N,N-dimethylformamide (DMF) solution, the solution is placed in an ultrasonic mill for ultrasonic dispersion, and the mixed solution is then centrifuged at a speed of 7000-9000 r / min for 10-30 minutes, and 90% of the supernatant is collected to obtain an E-MWCNTs dispersion of the corresponding concentration.

[0048] The conditions for preparing the E-MWCNTs dispersion using an ultrasonic pulverizer are: power of 120-240 watts, time of 0.5-2 hours, dispersant of hydroxypropyl methylcellulose (HPMC), and modified carbon nanotube solution concentration of 1-8 mg / mL.

[0049] Among them, hydroxypropyl methylcellulose powder (HPMC) AR grade; polyvinyl alcohol (PVA), molecular weight is about 170000.

[0050] The solid content of the prepared polyvinyl alcohol solution is about 6-10%.

[0051] Among them, the ratio of multi-walled carbon nanotubes (MWCNTs) to epigallocatechin gallate (EGCG) is 1:5.

[0052] For better explanation, the reagents and materials used in the present invention include: epigallocatechin gallate (EGCG), multi-walled carbon nanotubes (MWCNT), hydroxypropyl methylcellulose (HPMC), N,N-dimethylformamide (DMF), polyvinyl alcohol (PVA), etc.

[0053] In this study, a digital multimeter (MT-1280) was used to measure the resistance of the E-MWCNT / PVA electrothermal composite film. A direct current (DC, MS-605D) power supply was applied to both ends of the E-MWCNT / PVA electrothermal composite film sample using copper electrodes and thermocouples. This allowed for real-time measurement of the maximum surface temperature change of the E-MWCNT / PVA electrothermal composite film, thereby evaluating the electrothermal behavior of the film. By using E-MWCNT / PVA films of different lengths to measure their temperature changes under a voltage of 0-30V, the relationship between their stable temperature and voltage changes was evaluated; the voltage response performance of the E-MWCNT / PVA film was measured by increasing the voltage, cutting off the power, increasing the voltage, cutting off the power, etc. at different periods; the temperature response performance and stability of the E-MWCNT / PVA film under multiple cycles at the same voltage were tested; the temperature response cyclic characteristics of the E-MWCNT / PVA film under equal differential voltage were tested; the E-MWCNT / PVA electrothermal composite film was bent or twisted, and the thermal infrared (IR) image was recorded by an infrared camera (FLIRT460) to observe its heating performance under deformation and test its flexibility and elasticity; the morphology of the prepared E-MWCNT / PVA electrothermal composite film was observed by scanning electron microscopy (SEM).

[0054] In order to better illustrate the technical solutions and technical effects of the present application, the present application provides the following embodiments.

[0055] Example 1

[0056] 1. Mix 100 mg of multi-walled carbon nanotubes (MWCNTs) with 500 mg of epigallocatechin gallate (EGCG) and disperse them in deionized water, resulting in a 1:5 ratio of MWCNTs to EGCG. The mixture was then stirred in a 60°C water bath for 24 hours. E-MWCNT powder was obtained by filtration, washing, drying, and grinding. Subsequently, the E-MWCNTs and HPMC were dispersed in N,N-dimethylformamide (DMF), and the solution was ultrasonically dispersed in an ultrasonic mill at 180W for 1.5 hours. The mixed solution was then centrifuged at 8000 rpm for 10 minutes, and 90% of the supernatant was collected to obtain an E-MWCNT dispersion with a concentration of 5 mg / mL.

[0057] 2. Add a certain volume of E-MWCNTs dispersion to a polytetrafluoroethylene (PTFE) mold and heat it in a 60°C oven for 2 hours. Then, add the PVA solution to the mold and heat it in a 60°C oven for 1 hour. Remove the film with tweezers to obtain an electrothermal composite film.

[0058] 3. Performance test: SEM images of E-MWCNT / PVA films are shown in Figure 3. Figure 2 (a) Surface image and Figure 2 (b) The cross-sectional image shows that the E-MWCNT content of the test film is 0.5wt%, and it can be seen that the carbon nanotubes are evenly dispersed, forming a good double-layer structure. The prepared electrothermal composite film can be cut into different sizes, including 9×1cm 2 The maximum heating temperature of the electrothermal composite film can reach 130℃ under an applied voltage of 30V. Figure 3 As shown in (a), the E-MWCNT content of the test film is 0.5 wt.%, and the thickness is ∼120 μm.

[0059] Example 2

[0060] 1. Mix 100 mg of multi-walled carbon nanotubes (MWCNTs) with 600 mg of epigallocatechin gallate (EGCG) and disperse them in deionized water, resulting in a 1:6 ratio of MWCNTs to EGCG. The mixture was then stirred in a 70°C water bath for 30 hours. E-MWCNT powder was obtained by filtration, washing, drying, and grinding. Subsequently, the E-MWCNTs and HPMC were dispersed in N,N-dimethylformamide (DMF), and the solution was ultrasonically dispersed at 240W for 1 hour in an ultrasonic mill. The mixed solution was then centrifuged at 9000 rpm for 15 minutes, and 90% of the supernatant was collected to obtain a 6 mg / mL E-MWCNT dispersion.

[0061] 2. Add a certain volume of E-MWCNTs dispersion to a polytetrafluoroethylene (PTFE) mold and heat it in a 50°C oven for 3 hours. Then, add the PVA solution to the mold and heat it in a 50°C oven for 2 hours. Remove the film with tweezers to obtain an electrothermal composite film.

[0062] 3. Performance test: The prepared electrothermal composite film can be cut into different sizes, including 3×1cm 2 The maximum heating temperature of the electrothermal composite film can reach 140℃ under an applied voltage of 12V. Figure 3(b) The temperature response of the E-MWCNT / PVA film at 4, 6, 8, 10 and 12 V step-up and step-down conditions was measured for one cycle, with each cycle lasting 4 minutes and an interval of 2 minutes, showing very good voltage response performance and cycling performance, as shown in Figure 2. Figure 4 (a) shows the temperature response cycle characteristics of the E-MWCNT / PVA film at 4, 8 and 12V voltages, 10 cycles, each voltage applied for 2 minutes and off for 2 minutes, as shown in Figure 4 (b) shows the temperature response performance and stability of the E-MWCNT / PVA film under 12V for multiple cycles. Figure 4 (c) shows the temperature response of 10 cycles, with each voltage applied for 2 minutes and off for 2 minutes; 2 Different voltages were applied to the E-MWCNT / PVA electrothermal composite film, and its heating performance was observed using thermal infrared (IR) images recorded by an infrared camera (FLIRT460). Figure 5 As shown in (a), the heat generation photos under voltages of 6V and 12V are shown. When the device is bent or twisted, it can be seen that it still generates heat in the twisted and stretched state. Figure 5 As shown in (b), after the twisting or stretching is undone, it can still return to its original heating state, showing good flexibility and elasticity.

[0063] The above embodiments are preferred embodiments, and other embodiments are not listed one by one.

[0064] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A modified carbon nanotube polyvinyl alcohol electrothermal composite film, characterized in that: It comprises a substrate and a conductive filler deposited layer by layer on the surface of the substrate; Wherein, the conductive filler is multi-walled carbon nanotubes functionalized with epigallocatechin gallate; The method for preparing the electrothermal composite film comprises the following steps: (1) Multi-walled carbon nanotubes (MWCNTs) and epigallocatechin gallate (EGCG) are dispersed in deionized water in a certain proportion; the solution is then vigorously stirred under certain temperature and time conditions to achieve non-covalent modification of the multi-walled carbon nanotubes, and modified carbon nanotubes (E-MWCNTs) powder is obtained by filtration, washing, drying and grinding; (2) Dissolve polyvinyl alcohol (PVA) particles in an aqueous solution, heat and stir at 90°C to dissolve them, then add glycerol and hydroxypropyl methylcellulose (HPMC), continue mechanical stirring to completely dissolve them, and place the prepared mixed solution in a vacuum drying oven, evacuate the vacuum, and store overnight to remove bubbles; (3) A certain amount of E-MWCNTs and HPMC were dispersed in an N,N-dimethylformamide (DMF) solution and ultrasonically treated. The mixed solution was centrifuged at a certain speed for a certain time, and 90% of the supernatant was collected to obtain an E-MWCNTs dispersion of the corresponding concentration. A certain amount of E-MWCNTs solution was added to a polytetrafluoroethylene (PTFE) mold and then dried in an oven. (4) PVA solution was added to the above mold, and continued to dry in an oven, and removed by tweezers to obtain an electrothermal composite film.

2. The modified carbon nanotube polyvinyl alcohol electrothermal composite film according to claim 1, characterized in that: in, Multi-walled carbon nanotubes (MWCNTs) have a purity of 98 wt.%, a length of 0.5-2 μm, and an outer diameter of 10-20 nm.

3. The modified carbon nanotube polyvinyl alcohol electrothermal composite film according to claim 1, characterized in that: in, Epigallocatechin gallate (EGCG) powder AR grade.

4. The modified carbon nanotube polyvinyl alcohol electrothermal composite film according to claim 1, characterized in that: in, The preparation of epigallocatechin gallate functionalized multi-walled carbon nanotubes (E-MWCNTs) solution is as follows: Multi-walled carbon nanotubes (MWCNTs) and epigallocatechin gallate (EGCG) are dispersed in deionized water at a mass ratio of 1:(4-8); the mixture is then stirred in a water bath at 50-70°C for 12-36 hours, and E-MWCNTs powder is obtained by filtration, washing, drying and grinding. Subsequently, a certain amount of E-MWCNTs and hydroxypropyl methylcellulose (HPMC) are dispersed in an N,N-dimethylformamide (DMF) solution, the solution is placed in an ultrasonic mill for ultrasonic dispersion, and the mixed solution is then centrifuged at a speed of 7000-9000 r / min for 10-30 minutes, and 90% of the supernatant is collected to obtain an E-MWCNTs dispersion of the corresponding concentration.

5. The modified carbon nanotube polyvinyl alcohol electrothermal composite film according to claim 1, characterized in that: in, The conditions for preparing E-MWCNTs dispersion using an ultrasonic mill are: The power is 120-240 watts, the time is 0.5-2 hours, the dispersant is hydroxypropyl methylcellulose (HPMC), and the concentration of the modified carbon nanotube solution is 1-8 mg / mL.

6. The modified carbon nanotube polyvinyl alcohol electrothermal composite film according to claim 1, characterized in that: in, Hydroxypropyl methylcellulose powder (HPMC) AR grade; polyvinyl alcohol (PVA), molecular weight 170,000.

7. The modified carbon nanotube polyvinyl alcohol electrothermal composite film according to claim 1, characterized in that: in, The solid content of the prepared polyvinyl alcohol solution is 6-10%.

8. The modified carbon nanotube polyvinyl alcohol electrothermal composite film according to claim 4, characterized in that: in, The ratio of multi-walled carbon nanotubes (MWCNTs) to epigallocatechin gallate (EGCG) was 1:5.

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