Silver nanowire composite citric acid cross-linked chitosan transparent conductive film and preparation method thereof

Abstract

The application belongs to the field of photoelectric materials, and particularly relates to a silver nanowire composite citric acid cross-linked chitosan transparent conductive film and a preparation method thereof. The preparation method comprises the following steps: adding chitosan, citric acid and deionized water into a beaker in sequence, stirring uniformly, then adding acetic acid and glycerol in sequence, continuing to stir, and then reacting under high-temperature conditions to obtain a citric acid cross-linked chitosan solution; cleaning and drying PET, then uniformly spraying a silver nanowire suspension on the surface of the PET to obtain a silver nanowire / PET conductive film; coating the citric acid cross-linked chitosan solution on the surface of the silver nanowire / PET conductive film, drying, and then peeling the film from the PET. The silver nanowires on the conductive film have a grid structure, and the citric acid cross-linked chitosan is used as a substrate of the conductive film, so that the obtained conductive film has excellent heat resistance, light transmission and conductivity, and the preparation method is simple and easy to implement, and no toxic and harmful raw materials are used, which is safe and environmentally friendly.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photoelectric materials, and particularly relates to a silver nanowire composite citric acid cross-linked chitosan transparent conductive film and a preparation method thereof. BACKGROUND

[0002] With the rapid development of information technology, the flexible transparent electrode is gradually applied in photoelectric devices due to its superior mechanical properties such as bendability and foldability, and good light transmittance and conductivity. Indium tin oxide (ITO) is a traditional transparent conductive film material, which is widely used to manufacture photoelectric devices due to its high transparency, excellent conductivity, good chemical stability and high heat resistance. However, the scarcity of indium resources leads to high production cost of ITO, and ITO lacks flexibility and is prone to cracking in the application process and has biological toxicity, which limits its application in flexible electronic devices. Therefore, the development of low-cost and environmentally friendly flexible transparent film has become the research focus.

[0003] Silver nanowire (AgNWs) has a simple preparation method, certain flexibility, photoelectric performance comparable to ITO, and can be used to prepare conductive films in multiple ways, and the cost is much lower than that of ITO. Therefore, the silver nanowire transparent conductive film is the most powerful substitute for ITO. At present, scientists have explored the use of polyimide (PI), polydimethylsiloxane (PDMS), polyethylene terephthalate (PET) and the like to prepare silver nanowire composite transparent conductive film, but these substrate materials are difficult to degrade and bring burden to the environment. Cellulose, gelatin, starch, polylactic acid, polyvinyl alcohol and chitosan are biodegradable, and can be used as substrate materials of transparent electrodes to reduce environmental pollution and meet the demand for sustainable development. Among them, chitosan has excellent film-forming performance, good biocompatibility and biodegradability, and is an environmentally friendly material with great application potential. However, the poor thermal stability and excessive hydrophilicity of chitosan limit its application range. In recent years, people have improved its performance by cross-linking or adding fillers. The commonly used cross-linking agent is glutaraldehyde, but glutaraldehyde has biological toxicity and is not conducive to environmental protection. SUMMARY

[0004] In view of the shortcomings of the prior art, the present application provides a silver nanowire composite citric acid cross-linked chitosan transparent conductive film and a preparation method thereof. The silver nanowires on the conductive film have a grid structure, and citric acid cross-linked chitosan is used as the substrate of the conductive film. The obtained conductive film has excellent heat resistance, light transmittance and conductivity, and the preparation method is simple and easy to implement, and no toxic and harmful raw materials are used, which is safe and environmentally friendly.

[0005] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows:

[0006] A preparation method of a silver nanowire composite citric acid cross-linked chitosan transparent conductive film, comprising the following steps:

[0007] (1) chitosan, citric acid, and deionized water are sequentially added into a beaker, stirred uniformly, then acetic acid and glycerol are sequentially added, continue to stir, and then placed in a high temperature condition to react, to obtain a citric acid cross-linked chitosan solution;

[0008] (2) PET is cleaned and dried, then a silver nanowire suspension is uniformly sprayed on the surface of the PET to obtain a silver nanowire / PET conductive film;

[0009] (3) the citric acid cross-linked chitosan solution in step (1) is coated on the surface of the silver nanowire / PET conductive film in step (2), dried, and then the film is peeled off from the PET, to obtain the silver nanowire composite citric acid cross-linked chitosan transparent conductive film.

[0010] Preferably, the amount ratio of chitosan, citric acid, acetic acid, glycerol, and deionized water in step (1) is 2-3g:1.6-2.4g:1.3-2g:0.5-0.75g:100mL.

[0011] Preferably, the high temperature in step (1) is 120-140℃, and the reaction time is 15-20min.

[0012] Preferably, the spraying condition in step (2) is that the carrier gas pressure is 100-150kPa, the spraying speed is 14-18μL / s, and the spraying distance is 5-8cm.

[0013] Preferably, the silver nanowire suspension in step (2) is a silver nanowire ethanol suspension, and the concentration is 0.5-1.0mg / mL.

[0014] Preferably, the length of the silver nanowire in the silver nanowire suspension in step (2) is 20-30μm, and the diameter is 20-40nm.

[0015] Preferably, the coating method of the citric acid cross-linked chitosan solution in step (3) is spin coating, coating, or casting.

[0016] A silver nanowire composite citric acid cross-linked chitosan transparent conductive film prepared by the above preparation method.

[0017] The positive beneficial effects of the present application are:

[0018] 1. The present application uses natural non-toxic citric acid as a cross-linking agent, citric acid is added in the preparation of chitosan solution, the carboxyl group in citric acid combines with the amino group of chitosan to form an ester group structure, which improves the water absorption of chitosan, increases the mechanical strength and heat resistance of the chitosan film.

[0019] 2. The application prepares a silver nanowire / PET conductive film with a grid structure on the surface of PET by controlling the carrier gas pressure, spraying speed and spraying distance, improves the photoelectric performance, uses citric acid crosslinked chitosan as the substrate of the conductive film to improve the heat resistance of the conductive film, and first prepares a silver nanowire composite citric acid crosslinked chitosan transparent conductive film, which has excellent heat resistance, light transmittance, conductivity, flexibility, biocompatibility and biodegradability, is an environment-friendly photoelectric material, and has a simple and easy-to-operate preparation method, uses no toxic and harmful raw materials, and is safe and environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 SEM image of the conductive film of Example 1 of the application;

[0021] Figure 2 TG and DTG curves of the conductive film of Example 1 of the application;

[0022] Figure 3 TG and DTG curves of the conductive film of Comparative Example 1 of the application;

[0023] Figure 4 SEM image of the conductive film of Comparative Example 2 of the application. DETAILED DESCRIPTION

[0024] The application will be further described below in combination with some specific embodiments.

[0025] Example 1

[0026] A preparation method of a silver nanowire composite citric acid crosslinked chitosan transparent conductive film, comprising the following steps:

[0027] (1) 3 g of chitosan, 2.4 g of citric acid and 100 mL of deionized water were weighed and added into a beaker in sequence, stirred for 2 min, then 2 g of acetic acid and 0.75 g of glycerol were added, and stirred vigorously at room temperature for 4 h, and then placed in an environment of 130°C for reaction for 15 min to obtain a citric acid crosslinked chitosan solution;

[0028] (2) The PET was cleaned and dried, then 1.5 mL of silver nanowire suspension was uniformly sprayed on the surface of a 5 cm x 5 cm PET by a spray gun, the carrier gas pressure was 150 kPa, the spraying speed was 16 μL / s, and the spraying distance was 7 cm, and then dried to obtain a silver nanowire / PET conductive film;

[0029] The solvent of the silver nanowire suspension is ethanol, and the concentration of the silver nanowire suspension is 0.5 mg / mL, wherein the length of the silver nanowire is 30 μm and the diameter is 20 nm;

[0030] (3) the citric acid cross-linked chitosan solution of step (1) is spin-coated on the surface of the silver nanowire / PET conductive film of step (2) at a speed of 500 rpm for 50 s, and then is placed in a drying box at 55 DEG C for 4 h, and finally the film is peeled off from the PET to obtain the conductive film.

[0031] The transmittance of the conductive film of the example at 550 nm is 79.6%, and the square resistance is 40.3 Ω / sq; the scanning electron microscope and the thermogravimetric test results of the conductive film of the example are shown in Figure 1 and Figure 2 .

[0032] As shown in Figure 1 , the conductive film prepared by the application has a grid structure.

[0033] As shown in Figure 2 , in the first stage (0-150 DEG C), the weight loss rate of the film is only 6%, and the weight loss in this stage is mainly due to the evaporation of residual moisture and acetic acid in the film; in the second stage (150 DEG C-300 DEG C), the weight loss rate of the film is 24%, and the weight loss in this stage is mainly due to the volatilization of glycerol; the weight loss rate of the conductive film prepared by the application is not more than 10% at 200 DEG C, and the conductive film of the application has a high heat resistance.

[0034] Example 2

[0035] A preparation method of a silver nanowire composite citric acid cross-linked chitosan transparent conductive film, comprising the following steps:

[0036] (1) 2g of chitosan, 1.6g of citric acid and 100mL of deionized water are weighed into a beaker respectively, stirred for 2min, and then 2g of acetic acid and 0.5g of glycerol are added, stirred vigorously at room temperature for 4h, and then placed in an environment at 130 DEG C for 15min to obtain a citric acid cross-linked chitosan solution;

[0037] (2) the PET is cleaned and dried, then 2.5mL of silver nanowire suspension is uniformly sprayed on the surface of a 5cm*5cm PET by a spray gun, the carrier gas pressure is 150kPa, the spraying speed is 16μL / s, the spraying distance is 7cm, and the silver nanowire / PET conductive film is obtained after drying;

[0038] The solvent of the silver nanowire suspension is ethanol, and the concentration of the silver nanowire suspension is 0.5mg / mL, wherein the length of the silver nanowire is 30μm, and the diameter is 20nm;

[0039] (3) The citric acid cross-linked chitosan solution of step (1) is spin-coated on the surface of the silver nanowire / PET conductive film of step (2) at a spin-coating speed of 500 rpm and a spin-coating time of 50 s, and then placed in a drying box at 55°C for drying for 4 h. Finally, the film is peeled off from the PET to obtain the silver nanowire composite citric acid cross-linked chitosan transparent conductive film.

[0040] The transmittance of the conductive film of this example at 550 nm is 71.7%, and the square resistance is 23.4 Ω / sq.

[0041] Example 3

[0042] A preparation method of a silver nanowire composite citric acid cross-linked chitosan transparent conductive film, comprising the following steps:

[0043] (1) 2.5 g of chitosan, 1.6 g of citric acid and 100 mL of deionized water are weighed into a beaker respectively, stirred for 2 min, and then 1.3 g of acetic acid and 0.5 g of glycerol are added respectively. Stir vigorously at room temperature for 4 h, and then place in an environment of 130°C for 15 min to obtain a citric acid cross-linked chitosan solution;

[0044] (2) The PET is cleaned and dried, and then 4 mL of silver nanowire suspension is uniformly sprayed on the surface of a 5 cm x 5 cm PET by a spray gun. The carrier gas pressure is 150 kPa, the spraying speed is 16 μL / s, and the spraying distance is 7 cm. After drying, a silver nanowire / PET conductive film is obtained;

[0045] The solvent of the silver nanowire suspension is ethanol, and the concentration of the silver nanowire suspension is 0.5 mg / mL. The length of the silver nanowire is 30 μm, and the diameter is 20 nm;

[0046] (3) The citric acid cross-linked chitosan solution of step (1) is spin-coated on the surface of the silver nanowire / PET conductive film of step (2) at a spin-coating speed of 500 rpm and a spin-coating time of 50 s, and then placed in a drying box at 55°C for drying for 4 h. Finally, the film is peeled off from the PET to obtain the silver nanowire composite citric acid cross-linked chitosan transparent conductive film.

[0047] The transmittance of the conductive film of this example at 550 nm is 67.9%, and the square resistance is 7.6 Ω / sq.

[0048] Comparative Example 1

[0049] A preparation method of a silver nanowire composite chitosan conductive film, comprising the following steps:

[0050] (1) 3 g of chitosan is added to a beaker containing 100 mL of deionized water, stirred for 2 min, and then 2 g of acetic acid and 0.75 g of glycerol are added respectively. Stir vigorously at room temperature for 4 h to obtain a chitosan solution;

[0051] (2) The PET is cleaned and dried, and then 1.5 mL of silver nanowire suspension is uniformly sprayed on the surface of a 5 cm x 5 cm PET by using an airbrush, the carrier gas pressure is 150 kPa, the spraying speed is 16 μL / s, the spraying distance is 7 cm, and drying is performed to obtain a silver nanowire / PET conductive film;

[0052] The solvent of the silver nanowire suspension is ethanol, and the concentration of the silver nanowire suspension is 0.5 mg / mL, wherein the length of the silver nanowire is 30 μm, and the diameter is 20 nm;

[0053] (3) The chitosan solution in step (1) is spin-coated on the surface of the silver nanowire / PET conductive film in step (2), the spin-coating speed is 500 rpm, the spin-coating time is 50 s, and then the film is placed in a drying box at 55 °C for drying for 4 h, and finally the film is peeled off from the PET to obtain the product.

[0054] The transmittance of the conductive film in this embodiment at 550 nm is 80.4%, and the square resistance is 43.5 Ω / sq; the thermogravimetric test results of this comparative example are shown in Figure 3 .

[0055] As can be seen from FIG. 3, in the first stage (0-150 °C), the weight loss rate of the film is 8.9%, and the weight loss in this stage is mainly due to the evaporation of residual water and acetic acid in the film; in the second stage (150 °C-300 °C), the weight loss rate of the film is 39.6%, and the weight loss in this stage is mainly due to the volatilization of glycerol. Compared with embodiment 1 of the present application, the weight loss rate in each stage is relatively large, which indicates that the heat resistance decreases, which is mainly due to the cross-linking structure in the citric acid cross-linked chitosan of the present application, which slows down the volatilization of each component and improves the heat resistance of the conductive film.

[0056] Comparative Example 2

[0057] A method for preparing a silver nanowire composite citric acid cross-linked chitosan conductive film, comprising the following steps:

[0058] (1) 3 g of chitosan, 2.4 g of citric acid, and 100 ml of deionized water are weighed into a beaker, respectively, and stirred for 2 min, then 2 g of acetic acid and 0.75 g of glycerol are added, and stirred vigorously at room temperature for 4 h, and then placed in an environment of 130 °C for 15 min to obtain a citric acid cross-linked chitosan solution;

[0059] (2) The glass is cleaned and dried, and then 1.5 mL of silver nanowire suspension is uniformly sprayed on the surface of a 5 cm x 5 cm glass by using an airbrush, the carrier gas pressure is 150 kPa, the spraying speed is 16 μL / s, the spraying distance is 7 cm, and drying is performed to obtain a silver nanowire conductive network;

[0060] The silver nanowire suspension was prepared using ethanol as the solvent and had a concentration of 0.5 mg / mL. The silver nanowires had a length of 30 μm and a diameter of 20 nm.

[0061] (3) Spin-coat the citric acid crosslinked chitosan solution described in step (1) onto the surface of the silver nanowire conductive network described in step (2) at a spin coating speed of 500 rpm and a spin coating time of 50 s. Then place it in a drying oven at 55°C for 4 h and finally peel the film off the glass to obtain the final product.

[0062] The conductive film in this embodiment has a transmittance of 75.2% at 550 nm and a sheet resistance of 50.4 Ω / sq; the scanning electron microscope image of the conductive film in this embodiment is shown below. Figure 4 .

[0063] Depend on Figure 4 It can be seen that when the substrate PET is replaced with glass, the silver nanowires in the conductive film do not form a network structure, resulting in reduced transmittance and decreased conductivity.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a silver nanowire composite citric acid cross-linked chitosan transparent conductive film, characterized in that it comprises the following steps: (1) chitosan, citric acid and deionized water are sequentially added into a beaker, stirred uniformly, then acetic acid and glycerol are sequentially added, continue to stir, then placed in a high temperature condition for reaction, to obtain a citric acid cross-linked chitosan solution; (2) PET is cleaned and dried, then a silver nanowire suspension is uniformly sprayed on the surface of the PET to obtain a silver nanowire / PET conductive film; (3) the citric acid cross-linked chitosan solution in step (1) is coated on the surface of the silver nanowire / PET conductive film in step (2), dried, then the film is peeled off from the PET, to obtain a silver nanowire composite citric acid cross-linked chitosan transparent conductive film; the amount ratio of chitosan, citric acid, acetic acid, glycerol and deionized water in step (1) is 2-3g: 1.6-2.4g:1.3-2g:0.5-0.75g:100mL; The high temperature in step (1) is 120-140℃, and the reaction time is 15-20min.

2. The method for preparing a transparent conductive film of silver nanowires composite with citric acid crosslinked chitosan according to claim 1, characterized in that, The spraying condition in step (2) is: the carrier gas pressure is 100-150kPa, the spraying speed is 14-18μL / s, and the spraying distance is 5-8cm.

3. The method for preparing a transparent conductive film of silver nanowires composite with citric acid crosslinked chitosan according to claim 1, characterized in that, The silver nanowire suspension in step (2) is silver nanowire ethanol suspension, and the concentration is 0.5-1.0mg / mL.

4. The method for preparing a transparent conductive film of silver nanowires composite with citric acid crosslinked chitosan according to claim 3, characterized in that, The silver nanowire length in the silver nanowire suspension in step (2) is 20-30μm, and the diameter is 20-40nm.

5. The method for preparing a transparent conductive film of silver nanowires composite with citric acid crosslinked chitosan according to claim 1, characterized in that, The coating method of the citric acid crosslinked chitosan solution in step (3) is spin coating or flow casting. 6.A silver nanowire composite citric acid crosslinked chitosan transparent conductive film prepared by the preparation method in any one of claims 1-5.

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